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1
Hawkyard, Miles. "The fatigue crack growth resistance of Ti-6Al-4V." Thesis, University of Portsmouth, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.339512.
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Skalka, Jan. "Svařování Ti 6Al 4V elektronovým svazkem." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2016. http://www.nusl.cz/ntk/nusl-241156.
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The thesis is dedicated to welding combination of titanium alloy Ti-6Al-4V and austenitic steels 1.4301 by electron beam. Based on literature studies of bonding titanium and its alloys with steels, it was proposed to select for welding interlayer of copper, which could limit the impact of intermetallic phases on the mechanical properties of the weld seam and enable the creation of weld. For welding the pipe samples were used three methods of welding with various welding parameters. Samples which remain after thermal cycling vacuum-tight, were then further analyzed (micro-hardness, tensile test, etc.).
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Bonsang, Franz. "Facture and fatigue investigation of the Ti-6Al-4V titanium alloy." Thesis, McGill University, 1988. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=61939.
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Littlewood, Philip Dilan. "Microplasticity and fatigue crack initiation in titanium alloy Ti-6Al-4v." Thesis, University of Oxford, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.556214.
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Titanium alloys are often used in aerospace applications in which they are subjected to cyclic loading. It has been found that the addition of a hold at peak load greatly decreases the fatigue life of these alloys. This is referred to as "cold-dwell fatigue". In order to improve component life prediction, it is desirable to understand the mechanisms leading to initiation of fatigue cracks. Due to the high anisotropy of a-titanium, it is expected that deformation on a microstructural scale will he significantly heterogeneous. To understand the process of crack nucleation, the mecha- nisms of this deformation must first he understood. This thesis will present a series of experiments which will attempt to give some insight into this process. Two main lines of inquiry have heen undertaken. The first method uses electron hackscat- tered diffraction (EBSD) to obtain the crystal orientations within a selected region. Optical mi- croscopy and digital image correlation methods were then used to track the accumulation of strain in the region during deformation. Results were obtained for monotonic tension, cyclic fatigue, and cold-dwell fatigue. Behaviour in local strain peaks differed hetween loading modes, hut strain concentrations in the range of 2-4 times mean strain were typical. The second method uses the cross-correlation based EBSD technique developed by Wilkinson et al [1] to derive the dislocation densities present in a crystal. By tracking the changes in dislocation density after different deformation regimes, some insight can be gained into the local deformation processes that produced the dislocation densities. Strong links were found between the local crystallography and inhomogeneities in strain and dislocation density accumulation. In particular, interactions between grains of differing orientations was found to have a strong impact on deformation behaviour. Additionally, a link was found between high strain accumulation and crack initiation in both fatigue and dwell fatigue.
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Searles, Thomas K. "Microstructural characterization of the alpha / beta titanium alloy Ti-6Al-4V." The Ohio State University, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=osu1407510262.
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Goralka, Christopher Michael. "Tribological Behaviors of Graphene Nanolubricants on Titanium Alloy (Ti-6Al-4V)." Miami University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=miami1605833256406255.
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Kakavand, Pegah. "A Comparative Study on Micro Electro-Discharge Machining of Titanium Alloy (TI-6AL-4V) and Shape Memory Alloy (NI-TI)." TopSCHOLAR®, 2015. http://digitalcommons.wku.edu/theses/1466.
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The purpose of this research was to investigate the surface modifications that take place during the machining of NiTi SMA and Ti-6Al-4V with micro-EDM. This was done by creating an array of blind holes and micro-patterns on both work-pieces. To analyze the machined surface and investigate the results, scanning electron microscope (SEM), energy dispersive X- ray spectroscopy (EDS) and X-ray diffraction (XRD) techniques were employed. In addition, the effects of various operating parameters on the machining performance was studied to identify the optimum parameters for micro-EDM of NiTi SMA and Ti-6Al-4V. Recently, aerospace and biomedical industries have placed a high demand on nonconventional machining processes, which can be used to machine high strength and hardto- cut materials such as Titanium alloys, Shape Memory Alloys (SMA) and Super Alloys. Electrical Discharge Machining (EDM) is one of the non-traditional technologies that remove materials from the workpiece through a series of electrical sparks that occur between the workpiece and cutting tool with the presence of dielectric liquid. Obtaining smooth and defect-free surfaces on both workpieces was one of the challenges due to the re-solidified debris on the machined surface. The experimental results showed that there was significant amount of re-casting and formation of resolidification of debris on the Ti surface after machining. On the other hand, the surface generated in NiTi SMA were comparatively smoother with lesser amount of resolidified debris on the surface. By analyzing the results from XRD and EDS, some elements of electrode and dielectric materials such as Tungsten, Carbon and Oxygen were observed on NiTi and Ti surface after machining. In the study of effect of operating parameters, it was found that the voltage, capacitance and tool rotational speed had significant effect on machining time. The machining time was reduced by increasing the voltage, capacitance and tool rotational speed. The machining time was found to be comparatively higher for machining NiTi SMA than Ti alloy. Comparing all the parameters, the voltage of 60 V, capacitance of 1000 PF, and tool rotational speed of 3500 RPM were selected as optimum parameters for this study. Although signs of tool electrode wear and debris particles on the machined surface were observed for both workpieces during the micro-EDM process, Ti alloy and NiTi SMA could be machined successfully using the micro-EDM process.
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Gilpin, Andrew. "Prevention of Cathodic Delamination of Polyurethane Adhesive from Ti-6Al-4V Alloy Using Fluorinated Primers." University of Cincinnati / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1491558192907036.
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Zhang, Yancheng. "Numerical simulation approaches and methodologies for multi-physic comprehensions of titanium alloy (Ti-6Al-4V) CUTTING." Phd thesis, INSA de Lyon, 2011. http://tel.archives-ouvertes.fr/tel-00708761.
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The objective of this study is to model material removal with cutting tool in the case of the machining of Titanium alloy (Ti-6Al-4V) and to bring a multi-physic comprehension of chip formation and the tool/workpiece interaction by adopting finite element approaches and methodologies. For that, the present contribution begins by a macroscopic modeling of the orthogonal cutting process. The cut material behavior considered is supposed based on JC law. Moreover, in order to simulate properly the chip genesis, the material fracture energy concept is adopted for controlling the material damage evolution. This allows capturing the shear strain localization and consequently the chip segmentation for a given set of cutting parameters. The frictional contact model considers the influence of temperature on the limiting shear stress at the tool/chip interface. As a result, this reliable model has the capability to simulate the cutting process even with high coefficient of friction and with large cutting edge radius. The parametric study carried out by referring to this model shows a very interesting corroboration with experimental results. In a second step, the present research work presents a material microstructure-level cutting model (MML cutting model) for cutting simulation. The crystal plasticity theory is adopted for modeling the cutting of the Titanium alloy Ti-6Al-4V in orthogonal case. In this model, the grains of the studied material are explicitly considered, and their orientation angles and slip system strength anisotropy are considered as the main source of the microstructure heterogeneity in the cutting material. To simulate the material degradation process, the continuum intra-granular damage and discrete cohesive zone inter-granular damage models are developed, wherein the zero thickness cohesive elements are implemented to simulate the bond between grain interfaces. The material model is validated by a comparison of compression tests from literature. Finally, simulation results demonstrate the possibility to capture the influence of the microstructure on the material removal in terms of chip formation. It is demonstrated that the grain orientation angle plays an important role for the chip segmentation and its periodicity during the cutting process. This certainly can affect the evolution of the cutting force. Additionally, the surface integrity is discussed based on the MML cutting model for different cutting speeds and feed rates. Indeed, a parametric study shows that the surface integrity is seriously affected by the machining parameters, and the affected region is limited within three layer grains for the present MML cutting model.
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Perumal, Bama. "Microstructure and texture evolution during thermo-mechanical processing of two phase titanium alloy Ti-6Al-4V." Thesis, Open University, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.552784.
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Understanding the relationship between high-temperature deformation and microstructure evolution during hot forging of aero-engine alloys is important in ensuring optimum material properties in the final component. Of particular interest, with respect to two-phase titanium alloys is the break-up, below the beta-transus temperature, of an initial transformed alpha-lamellar microstructure during thermo-mechanical processing; this plays a key role in the development of the equiaxed alpha microstructure desired for the final product. Significant research effort has been put into understanding the mechanism for dynamic globularization, formation of kinking and shear banding within the alpha lamellae that can lead to break-up, but no complete quantitative analysis of the evolution of microstructural parameters and crystallographic texture with deformation currently exists. Therefore, reliable quantitative microstructural data associated with this process is important for both informing and validating models describing high-temperature metal-forming. To investigate the influence of hot working parameters, strain, strain rate and temperature, on microstructure evolution in Ti-6Al-4V a series of hot isothermal axis-symmetric compression tests have been carried out at temperatures both low and high in the alpha + beta stability field (880°C and 950°C, respectively), using strain rates (0.01, 0.1 and lis) relevant to industrial press forging. The experimental results showed that the morphology of the secondary a phase transforms gradually from lamellar to equiaxed under the influence of the deformation parameters and that the a lath thickness appears to have little influence on flow behaviour. It was also found that, at lower strains, the alpha laths appeared to be undeformed or only partially distorted. As strain progressed the laths were further broken up by distortion, bending and kinking. The mean aspect ratio of the alpha laths was found to exhibit a gradual reduction with increased strain. The lath area, length and perimeter showed a tendency to decrease with increasing strain. Furthermore, orientation image mapping (by EBSD) and texture analysis (by neutron diffraction) of the alpha phase were used to study the textural evolution during the hot deformation of the specimens and the mechanism involved on development and evolution of crystallographic texture during the a-β-a phase transformation. The strengthening of the ~-phase texture is observed on heating the sample during a-β phase transformation, where it was observed that Burgers relationship was followed but no evidence of preferential transformation was detected. In contrast a definite deviation from the Burgers relationship was observed during hot-compression. During β-a phase transformation upon cooling, however, the Burgers relationship was followed, which is evidence for a texture memory effect due to the growth of the primary alpha phase present at high temperatures.
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Alavi, Farshid. "Optimization of Process Parameters in Micro Electrical Discharge Machining (EDM) of TI-6AL-4V Alloy." TopSCHOLAR®, 2016. http://digitalcommons.wku.edu/theses/1568.
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Ti-6Al-4V has a wide range of applications such as in the automotive and aerospace industries. Nevertheless, titanium alloys are very difficult to machine by conventional methods. Micro-EDM is a non-conventional machining method that uses the thermal effect of precisely controlled sparks. Manufacturers are looking for the methods and optimal settings to increase the productivity of micro-EDM in terms of lessening machining time and tool wear. Moreover, surface integrity of the machined area is crucial for some products such as biomedical implants.
The objective of this study was to investigate the effects of the micro-EDM process parameters on response variables, in order to understand the behavior of each parameter as well as to determine their optimal values. Although, there is a substantial amount of literature studying different aspects of micro-EDM, most of them were designed based on the one-factor-at-a-time experiments instead of studying all factors, simultaneously. This research was conducted through a series of experiments using a full factorial design. An analysis of variance was employed to analyze the findings and to determine the effect and significance of each process parameters on the response variables.
The process parameters included voltage, capacitance, electrode rotational speed, and electrode coating. Voltage and capacitance were studied separately as well as in combination in terms of the discharge energy. Response variables consisted of machining time, tool wear, crater size, microhardness, and element characterization. The surface morphology and element characterization were studied through the application of SEM and EDS analysis.
The findings indicated that voltage had a decreasing effect on machining time, while it increased the crater size. Capacitance decreased machining time and tool wear. It had an increasing effect on the surface hardness. The effects of the TN-coating and electrode rotational speed were not statistically significant. Voltage and capacitance were the only parameters affecting element characterization. The affected elements included Ti, Al, C, and W. The optimal process parameters for two sets of response variables were determined using Minitab 17.
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Colman, Bruno Fontoura da Silva. "Projeto de prótese de disco intervertebral de Ti-6Al-4V entre L4/L3." Universidade Estadual Paulista (UNESP), 2018. http://hdl.handle.net/11449/153841.
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Previous issue date: 2018-03-05<br>Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)<br>Esse trabalho tem a finalidade de projetar, com base em levantamento bibliográfico, uma prótese de disco intervertebral de Ti6Al4V pelo processo DMLS. Os sistemas de imagem de tomografias computadorizadas e ressonâncias magnéticas trabalham de maneira semelhante. Imagens em 3D de dados dos pacientes são construídas através da combinação de fatias 2D tomadas a partir de sistemas de sensores e da interpolação entre eles. A distância entre as fatias desses sistemas de imagens é grosseira comparada com a tecnologia da manufatura aditiva, portanto, esses processos combinam as imagens das fatias dentro de um software para criar um modelo 3D sobrepondo camadas, devido a essa sinergia entre os dois tipos de sistema, pesquisadores de todo o mundo tentam melhorar e inventar próteses para substituir o disco intervertebral através da ciência. Os resultados mostraram que a fabricação de uma prótese de disco com junta esférica pelo processo de manufatura aditiva é viável, porém nos segmentos menores, como na cervical ainda são difíceis de produzir devido à altura do disco intervertebral e ao limite da dimensão das camadas da manufatura aditiva, que atualmente estão por volta dos 20μm, por isso requerem tratamentos superficiais após sua fabricação. Espera-se que este trabalho possa ajudar futuros pesquisadores da área de biomecânica da coluna vertebral.<br>This work has the purpose of designing, based on a bibliographical survey, an intervertebral disc prosthesis of Ti6Al4V by the DMLS process. Computed tomography (CT) imaging systems and MRIs work similarly. 3D images of patients data are constructed by combining 2D slices taken from sensor systems and interpolating between them. The distance between the slices of these imaging systems is rough compared to the additive manufacturing technology, so these processes combine the slice images within a software to create a 3D model overlapping layers because of this synergy between the two system types, researchers around the world try to improve and devise prostheses to replace the intervertebral disc through science. The results showed that the manufacture of a disc prosthesis with spherical joint by the additive manufacturing process is feasible, but in the smaller segments, such as in the cervical still difficult to produce due to the height of the intervertebral disc and to the limit of the size of the layers of the manufacture additives, which are currently around 20μm, so they require surface treatments after their manufacture. It is hoped that this work may help future researchers in the area of spinal biomechanics.<br>CAPES - PROPG
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Chafino, Aixa Juan Antonio. "Mechanical properties opimization of Ti-6Al-4V ELI alloy by controlling its microstructure for biomedical applications." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEI006.
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Le travail consiste en l'optimisation de la microstructure d'un alliage usuel TA6V par obtention de phases métastables. Ces nouvelles microstructures, obtenues par traitements thermiques, permettent d'améliorer la tenue mécanique (statique et en fatigue) de l'alliage sans pour autant changer la biocompatibilité<br>This PhD aims at optimizing the microstructure of the usual TA6V alloy by using metastable phases. These new microstructures, obtained by thermal treatments, permit to improve the mechanical strength (static but also the fatigue ones) without modifying the biocompatibility
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Zhao, Yixiang. "Effects of Laser Shock Peening on Residual Stress, Texture and Deformation Microstructure of Ti-6Al-4V Alloy." University of Cincinnati / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1353343745.
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Kelly, Shawn Michael. "Thermal and Microstructure Modeling of Metal Deposition Processes with Application to Ti-6Al-4V." Diss., Virginia Tech, 2004. http://hdl.handle.net/10919/29731.
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Laser metal deposition (LMD) offers a unique combination of process flexibility, time savings, and reduced cost in producing titanium alloy components. The current challenge in processing titanium alloys using LMD methods is understanding the complex microstructure evolution as a part is fabricated layer by layer. The current work focuses on the characterization, thermal, and microstructural modeling of multilayered Ti-6Al-4V deposits. A thermal model has been developed using finite difference techniques to predict the thermal history of LMD processes. A microstructure model that predicts the alpha phase fraction and morphology evolution was constructed to quantify the effect of thermal cycling on the as-deposited microstructure evolution. Alpha dissolution and growth are modeled assuming one-dimensional plate dissolution according to a parabolic rate law, and a Johnson-Mehl-Avrami-Kolmorgorov (JMAK) nucleation and growth model, respectively. Alpha morphology (colony-alpha and basketweave-alpha) evolution is tracked using a simplistic approach.
Characterization of the deposit has shown that a complex microstructure evolves consisting of a two distinct regions: a transient region of undeveloped microstructure and a characteristic layer that is periodically repeated throughout the deposit. The transient region contains a fine basketweave and colony-alpha morphology. The characteristic layer contains a two phase mixture of alpha+beta, with the alpha phase exhibits regions of colony-alpha (layer band) and basketweave-alpha morphology.
The different regions of microstructural contrast in the deposit are associated with thermal cycling. The thermal model results show that a heat affected zone defined by the beta transus extends approximately 3 layers into the deposit. The phase fraction model predicts the greatest variation in microstructural evolution to occur in a layer n after the deposition of layer n+3. The results of the morphology model show that increased amounts of colony-alpha form near the top of a characteristic layer. It follows that a layer band (colony-alpha region) forms as a result of heating a region of material to a peak temperature just below the beta transus, where a large amount of primary-alpha dissolves. Upon cooling, colony-alpha forms intragranularly. The coupled thermal and microstructure models offer a way to quantitatively map microstructure during LMD processing of Ti-6Al-4V.<br>Ph. D.
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Slabý, Ondřej. "Produktivní obrábění titanových slitin." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2012. http://www.nusl.cz/ntk/nusl-230126.
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This diploma thesis is focused on a productive machining of titanium alloys. At the beginning it deals about titanium and its alloys. It describes chip generation mechanism, tool blunting and surface quality. Further it contains modern strategies of efficient titanium alloys machining. Then it analyzes contemporary manufacturing technology of hinge made of titanium alloy Ti-6Al-4V in Frentech Aerospace s.r.o. company, and at the end finds possibility of savings by inovation of roughing process.
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Smith, Benjamin Daniel. "Microstructure-sensitive plasticity and fatigue of three titanium alloy microstructures." Thesis, Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/49237.
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Titanium alloys are employed in many advanced engineering applications due to their exceptional properties, i.e., a high strength-to-weight ratio, corrosion resistance, and high temperature strength. The performance of titanium alloys is known to be strongly affected by its inherent microstructure, which forms as a result of its thermo-mechanical processing. These microstructures produce compromise relationships between beneficial and detrimental effects on the alloy's performance. To study these structure-property relationships, two distinct crystal plasticity algorithms have been calibrated to data acquired from cyclic deformation experiments performed on three different Ti microstructures: (1) Ti-6Al-4V beta-annealed , (2) Ti-18 solution-treated, age-hardened (STA), and (3) Ti-18 beta-annealed, slow-cooled, age-hardened (BASCA). The calibrated models have been utilized to simulate fatigue loading of variant microstructures to investigate the influence of mean grain size, crystallographic texture, and phase volume fraction. The driving force for fatigue crack nucleation and propagation is quantified through the calculation of relevant fatigue indicator parameters (FIPs) and radial correlation functions are employed to study the correlation between favorably oriented slip systems and the extreme value FIP locations. The computed results are utilized to observe fatigue performance trends associated with changes to key microstructural attributes.
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Tiwari, Rajesh Kumar. "The Thermal Stability of Anodic Oxide Coatings - Strength and Durability of Adhesively Bonded Ti-6Al-4V Alloy." Diss., Virginia Tech, 2002. http://hdl.handle.net/10919/28528.
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The lap shear strength of chromic acid anodized, primed, Ti-6Al-4V alloy bonded with a high performance FM-5 polyimide adhesive has been investigated as a function of thermal treatment for selected times at various temperatures in air. The research findings indicate that the lap shear strength decreases with the increase in duration of the thermal treatment at constant temperature and with the increase in temperature at constant time. The bond fails increasingly in the oxide coating with increasing treatment temperature and time of treatment. Surface analysis results for debonded specimens suggest that the process leading to failure is the formation of fluorine-containing materials within the oxide, which weakens the adherend-adhesive bond. The formation of the fluorine components is facilitated by treatment at elevated temperatures. This study suggests that the presence of fluoride ions in the anodic oxide coating, prior to bonding, is detrimental to the bond strength of adhesively bonded Ti-alloy when exposed to high temperatures.
The wedge test configuration was used to investigate the influence of temperature on the bond durability of adhesively bonded chromic acid anodized Ti-6Al-4V alloy in air. Based on the average crack length vs. exposure time data, the bond durability varied in the order -25°C > 24°C > 177°C. In each case, the bonded joint failed cohesively within the adhesive, irrespective of the temperature of exposure. XPS analysis and scanning electron photomicrographs of failure surfaces revealed that the failure occurred at the scrim cloth/adhesive interface.
The influence of thermal treatment history on the bond durability of adhesively bonded chromic acid anodized Ti-6Al-4V alloy immersed in boiling water was also investigated. The average crack length vs. immersion time indicated no significant differences for specimens that were thermally treated and then bonded compared to the non-thermally treated specimens. In addition, the failure mode was cohesive within the adhesive for specimens prepared using various thermal treatment conditions. The crack growths for samples treated for 0.5 hour and 1.0 hour and for non-thermally treated specimens for any given exposure time were equivalent. In addition, cohesive failure (failure within adhesive) was observed for each specimen under each treatment condition. The specimens that were bonded and then thermally treated for 3 hours, failed in the oxide coating immediately upon insertion of the wedge. Surface analysis results for debonded specimens suggest that the process leading to failure is the formation of fluorine-containing materials within the oxide. The measured average activation energy for the formation of aluminum fluoride species is 149 kJ/mol. The high activation energy suggests that the rate of aluminum fluoride formation is substantial only at high temperatures.
In summary, the presence of fluorides in the anodic oxide coatings prior to bonding is detrimental to the overall strength and durability of adhesively bonded chromic acid anodized Ti-6Al-4V joints which have been exposed to high temperatures (350°C-399°C).<br>Ph. D.
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Whittaker, Jarrod Talbott. "Ductility and Use of Titanium Alloy and Stainless Steel Aerospace Fasteners." Scholar Commons, 2015. http://scholarcommons.usf.edu/etd/5796.
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The main purpose of this thesis is to investigate the ductility and application of titanium alloys, like titanium 6Al-4V, when used in aerospace fasteners compared to more conventional stainless steel aerospace fasteners such as A286. There have been concerns raised about the safe usability of titanium 6-4 in the aerospace industry due to its lack of strain hardening. However, there is a lack of data pertaining to this concern of safe usage which this thesis aims to address. Tensile tests were conducted to find the ductility indexes of these fasteners which quantify the amount of plastic to elastic elongation. From the tests conducted it was found that the two materials yield and tensile strengths were very similar, though the ductility index of A286 is on average ten times greater than that of titanium 6-4. This thesis includes joint diagram examples that analyze typical joints using both materials. It was found from joint diagram examples that the lower ductility index of the titanium alloy will only be detrimental to use at higher preloads. However, the titanium alloy can be used safely in place of A286 in most loading situations just with narrower safety margins in these controlled examples.
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Poondla, Narendra Babu. "A STUDY OF WELDED BUILT-UP BEAMS MADE FROM TITANIUM AND A TITANIUM ALLOY." University of Akron / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=akron1271095999.
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Caudill, James R. "ENHANCED SURFACE INTEGRITY WITH THERMALLY STABLE RESIDUAL STRESS FIELDS AND NANOSTRUCTURES IN CRYOGENIC PROCESSING OF TITANIUM ALLOY TI-6AL-4V." UKnowledge, 2019. https://uknowledge.uky.edu/me_etds/134.
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Burnishing is a chipless finishing process used to improve surface integrity by severe plastic deformation (SPD) of surface asperities. As surface integrity in large measure defines the functional performance and fatigue life of aerospace alloys, burnishing is thus a means of increasing the fatigue life of critical components, such as turbine and compressor blades in gas turbine engines. Therefore, the primary objective of this dissertation is to characterize the burnishing-induced surface integrity of Ti-6Al-4V alloy in terms of the implemented processing parameters. As the impact of cooling mechanisms on surface integrity from SPD processing is largely unexplored, a particular emphasis was placed upon evaluating the influence of cryogenic cooling with liquid nitrogen in comparison to more conventional methodologies.
Analysis of numerical and experimental results reveals that burnishing facilitates grain refinement via continuous dynamic recrystallization. Application of LN2 during SPD processing of Ti-6Al-4V alloy suppresses the growth of new grains, leading to the formation of near-surface nanostructures which exhibit increased microhardness and compressive residual stress fields. This is particularly true in cryogenic multipass burnishing, where successive tool passes utilizing lower working pressures generate thermally stable work hardened surface layers, uniform nano-level surface finishes, and significantly deeper layers of compressive residual stresses.
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Andersson, Niklas. "Modelling of metal removal rate in titanium alloy milling." Thesis, Högskolan i Gävle, Maskinteknik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-27011.
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Titanium is one of fourth most abundant structural metal in earths soil. It is in a composition with other elements, forming titanium alloys. These alloys are used in many different areas, such as medical, energy and sports, but is most commonly used in aerospace applications. Titanium alloys have different solid phases, α, α+β and β depending on temperature and the amount of α and β-stabilizers.When machining titanium alloys, one of the most important factors to control is the temperature in the cutting zone. The built-up heat in the cutting edge of the tool, are connected to titanium alloys low thermal conductivity and high heat capacity, which means that the alloy has low heat conduction from the cutting zone. The temperature is strongly depending on the cutting speed, which is the relative speed difference between the cutting tool and the workpiece. Many studies and research work have been conducted surrounding this fact, focusing on the physical and chemical quantities, to model tool wear progression and how this affects the tool life and the metal removal. These models are often implemented and analyzed in finite element software providing detailed but time-consuming solutions.The focus for this work have been on developing a suitable tool life expectancy model, using design of experiments in combination with metamodeling to establish a model connecting cutting parameters and measured responses in terms of tool life, from a conducted milling experiment. This models where supposed to provide a platform for customer recommendation and cutting data optimization to secure reliable machining operations. The study was limited to focus on the common α+β titanium alloy 6Al-4V. The outcome and conclusion for this study, is that the tool life is strongly connected to the choice of cutting speed and the radial width of cut and that these parameters can be predicted by the two models that have been develop in this project. The models ensure the highest possible metal removal rate, to selected parameters.
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Zucato, Juliano Torteli de Godoi. "Influência do aporte térmico na soldagem da liga de titânio Ti-6Al-4V com laser pulsado Nd:YAG." Ilha Solteira, 2018. http://hdl.handle.net/11449/154870.
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Orientador: Vicente Afonso Ventrella<br>Resumo: O trabalho consiste em um estudo da soldagem sobre uma placa da liga de titânio ASTM (Ti-6Al-4V) de espessura 1,44 mm, utilizando o processo de soldagem à laser Nd:YAG na condição autógena, realizando alterações de parâmetros no processo de soldagem afim de alterar o aporte térmico, encontrando propriedades características como a dureza, tensão de escoamento e microestrutura do material. Os ensaios realizados para a pesquisa foram: análise macrográfica, ensaio de tração, ensaio de microdureza e caracterização microestrutural. Para revelação dos detalhes no metal de solda, foi utilizado um ataque químico com o reagente Kroll. As medidas de geometria (largura e profundidade de penetração) dos cordões de solda, assim como a presença de descontinuidades, foram realizadas através de imagens obtidas pelo microscópio estéreo Zeiss Discovery.V8. O processamento e medição das imagens foi realizado através do software "AxioVision", um software associado ao microscópio utilizado. A análise da microestrutura foi realizada através do Microscópio Óptico Neophot 21, já o ensaio de tração foi realizado através de uma Máquina Universal de Ensaios, além do ensaio de microdureza, que foi realizado na escala Vickers. As análises das propriedades mecânicas foram confrontadas com a microestrutura obtida de acordo com a variação do aporte térmico. Como resultados, foram encontradas várias características essenciais para uma boa soldagem da liga, pois a cada incremento de aporte térmico, o cordão de... (Resumo completo, clicar acesso eletrônico abaixo)<br>Abstract: The work consists of a study of the welding on a plate of titanium alloy ASTM (Ti-6Al-4V) of thickness 1.44 mm, using the welding process Nd: YAG in the autogenous condition, making changes of parameters in the process of welding in order to change the thermal input, finding characteristic properties such as hardness, yield stress and microstructure of the material. The tests carried out for the research were: macrographic analysis, tensile test, microhardness test and microstructural characterization. To reveal the details in the weld metal, a chemical attack was used with the Kroll reagent. The measurements of the geometry (width and depth of penetration) of the weld beads, as well as the presence of discontinuities, were made through images obtained by the stereo microscope Zeiss Discovery.V8. The images were processed and measured using the "AxioVision" software, a software associated with the microscope used. The analysis of the microstructure was performed through the Optical Microscope Neophot 21, and the tensile test was performed through a Universal Testing Machine, in addition to the microhardness test, which was performed on the Vickers scale. The analysis of the mechanical properties were compared with the microstructure obtained according to the variation of the thermal input. As a result, several essential characteristics have been found for a good welding of the alloy, because with each increment of thermal input, the weld bead increases in width, depth and har... (Complete abstract click electronic access below)<br>Mestre
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Gaddam, Raghuveer. "Effect of boron and hydrogen on microstructure and mechanical properties of cast Ti-6Al-4V." Licentiate thesis, Luleå tekniska universitet, Materialvetenskap, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-17757.
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Titanium and its alloys are widely used in applications ranging from aeroengines and offshore equipment to biomedical implants and sporting goods, owing to their high ratio of strength to density, excellent corrosion resistance, and biomedical compatibility. Among the titanium alloys used in aerospace, Ti-6Al-4V (an α+β alloy) is the most widely used, in applications in which the temperature may reach 350°C, at which point it retains good fatigue and fracture properties as well as moderate tensile strength and ductility. These alloy properties are dependent on variables such as crystalline structure, alloy chemistry, manufacturing techniques and environmental conditions during service. These variables influence the microstructure and mechanical properties of titanium alloys. With regard to the alloy chemistry and operating environment, the focus of the present work is to understand the influence of boron and hydrogen on the microstructure and selected mechanical properties of cast Ti-6Al-4V. The addition of boron to cast Ti-6Al-4V (0.06 and 0.11 wt% in this work) refines the coarse “as cast” microstructure, which is evaluated quantitatively using FoveaPro image analysis software. Compression testing was performed using a Gleeble 1500 instrument, by applying a 10% strain at different strain rates (0.001, 0.1 and 1 s-1) for temperatures in the range 25-1100°C. The tests were performed to evaluate the effect of boron on the mechanical properties of the alloy. It was observed that there is an increase in the compressive strength, predominantly at room temperature, of cast Ti-6Al-4V after the addition of boron. Metallographic evaluation showed that this increase in strength is a likely result of reductions in both the prior β grain and α colony dimensions, which is caused by boron addition. Studies in a hydrogen environment at 150 bar showed that cast Ti-6Al-4V exhibited lower yield strength and lower ultimate tensile strength in comparison with those properties measured in an air environment. No significant change in the ductility was observed. It was also noted that in a high strain range (≈2%) the low cycle fatigue (LCF) life was significantly reduced in hydrogen compared with air. Microstructural and fractographic characterization techniques were used to establish the role of hydrogen on the deformation mechanism by analysing the crack propagation path through the microstructure. It is seen that cracks tend to propagate along the interface between prior β grain boundaries and/or along the α colony boundaries<br>Godkänd; 2011; 20110823 (raggad); LICENTIATSEMINARIUM Ämnesområde: Konstruktionsmaterial/Engineering Materials Examinator: Docent Marta-Lena Antti, Institutionen för teknikvetenskap och matematik, Luleå tekniska universitet Diskutant: PhD Magnus Hörnqvist, Volvo Aero Corp. Materials Technology, Trollhättan Tid: Torsdag den 22 september 2011 kl 10.00 Plats: E246, Luleå tekniska universitet
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Bamford, Erik. "Tool wear in turning of titanium alloy Ti–6Al–4V : Challenges and potential solutions for crater wear, diffusion and chip formation." Thesis, Uppsala universitet, Tillämpad materialvetenskap, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-306373.
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Titanium alloys are major materials used in the airplane industry, and prospects show that airplane production will double in the next 20 years. Consequently, the demand for cutting tools for machining of titanium alloys will increase. The primary problem when machining titanium alloys is their low thermal conductivity. Crater wear is the main factor limiting tool life, and is generally caused by thermal diffusion due to high temperatures in the tool-chip interface. This master’s thesis was performed in collaboration with Sandvik Coromant, with the prospect to increase knowledge of how diffusion and chip formation influences crater wear progression. The aim was to study tool wear of cutting tools when turning Ti–6Al–4V. This was done by testing two different rake face geometries, both coated and uncoated, at cutting speeds of 30–115 m/min. Diffusion was investigated to learn about the impact it has on crater wear. Chips were examined to investigate chip formation and shear strain. The coated modified rake face insert showed less crater wear only for the initial few seconds of machining. Uncoated inserts with a modified rake face showed higher diffusion rate and faster crater wear progression than did standard inserts. The standard inserts showed twice as long tool life as did the modified inserts. No significant differences in the chip formation mechanism were found between modified and standard inserts. Cracks were found within shear bands that were thinner than usual, which suggest that the generation of cracks allows less shear deformation.
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Garcia, de Cortazar Maider. "Etude de la faisabilité et du transfert de technologie pour l'alliage Ti-6Al-4V renforcé par du monoborure de titaneDevelopment of a new reinforced titanium alloy : basic research and technological transfer for the Ti-6Al-4V/TiB material." bordeaux 1, 2006. http://www.theses.fr/2006BOR13195.
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Le matériau composite à matrice de titane renforcée par des cristaux discontinus de monoborure de titane (TiB) constitue une classe nouvelle de matériaux destinés à des applications de haute technologie. Ces composites présentent des avantages car le procédé d’élaboration permet l’obtention de pièces de formes complexes à moindre coût par rapport aux composites à matrice titane renforcée par des filaments continus. Le procédé d’obtention de composites Ti/TiB nécessite deux étapes de fabrication : ( 1) au cours de la première étape un pré-composite de fraction volumique élevée en TiB est obtenu par un procédé d’autocombustion ( SHS), (2) lors d’une seconde étape, ce composite est dilué dans l’alliage de titane liquide pour obtenir la fraction volumique désirée. Des composites de fraction volumique en TiB comprise entre 0 et 10% ont été élaborés puis caractérisés. La microstructure de la matrice est affinée et les performances mécaniques sont améliorées par la présence du TiB. Finalement, une étude technico-économique de ce procédé a été réalisée pour évaluer la viabilité industrielle du matériau et du procédé.
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Kusuma, Chandrakanth. "The Effect of Laser Power and Scan Speed on Melt Pool Characteristics of Pure Titanium and Ti-6Al-4V alloy for Selective Laser Melting." Wright State University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=wright1464271345.
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Benmessaoud, Fatna. "Influence de la microstructure sur le comportement mécanique de l'alliage de titane Ti-6Al-4V : étude expérimentale et modélisation numérique multi-échelle Role of grain size and crystallographic texture on tensile behavior induced by sliding mechanism in Ti-6Al-4V alloy An optimization of the local hall-petch relationship using slip trace analysis technique and scale transition rules: application in equiaxed Ti-6Al-4V titanium alloy." Thesis, Ecole nationale des Mines d'Albi-Carmaux, 2020. http://www.theses.fr/2020EMAC0005.
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L’amélioration des performances mécaniques des matériaux utilisés dans l’aéronautique repose généralement sur la compréhension de la relation entre les paramètres microstructuraux et le comportement mécanique macroscopique. De plus, le caractère hétérogène et anisotrope de la plupart des matériaux métalliques, notamment l’alliage de titane Ti-6Al-4V, implique une étude assez approfondie à l’échelle locale. Ce travail constitue une contribution dans ce domaine. Il a pour but d’analyser le comportement mécanique de l’alliage Ti-6Al-4V soumis à des sollicitations monotones et cycliques en lien avec la microstructure. Des caractérisations microstructurales ont été tout d’abord effectuées sur des microstructures nodulaires de Ti-6Al-4V possédant la même texture cristallographique mais avec trois tailles de grain différentes : ultra fine, fine et standard, puis sur des microstructures possédant la même taille de grain mais avec deux textures différentes : forte et faible. Dans une deuxième étape, des essais mécaniques monotones et cycliques ont été réalisés. Les résultats de cette partie ont permis le développement d’un modèle à l’échelle macroscopique. Par la suite, une technique d’analyse des traces de glissement a été développée dont l’objectif est d’identifier la contribution de différents systèmes de glissement dans l’accommodation de la déformation plastique. La dernière partie de cette thèse a été consacrée au développement d’un modèle de plasticité cristalline couplé à la méthode des éléments finis (Crystal Plasticity Finite Element Method (CPFEM)) permettant d’analyser l’effet couplé de la taille moyenne des grains, leur dispersion relative et leur texture cristallographique sur le comportement obtenu aux échelles microscopique, mésoscopique et macroscopique. Les paramètres du modèle ont été identifiés en utilisant des techniques appropriées de transition d’échelles en champs moyens. Les Volumes Élémentaires Représentatifs (VER) utilisés dans le modèle ont été optimisés en considérant deux contraintes majeures : un nombre de grains représentatif et un maillage adéquat. Les simulations numériques ont été réalisées par le biais du code de calcul éléments finis Abaqus/Standard interfacé par la librairie ZMAT<br>Improving the mechanical performances of materials used in aeronautics industry is generally based on the understanding of the relationships between their microstructural features and their mechanical behavior observed at the macroscopic scale. In addition, the heterogeneous and the anisotropic nature of many materials, in particular Ti-6Al-4V titanium alloy, implies a rather detailed investigation of the mechanical behavior at the local scale. This PhD work is a contribution to analyze the mechanical behavior of the Ti-6Al-4V alloy submitted to monotonic and cyclic loadings by considering relationship with the microstructure features. Microstructural characterizations were first performed on nodular Ti-6Al-4V microstructures with identical crystallographic texture and three different grain sizes (ultra fine, fine and standard), then on microstructures with the same grain size but two texturing degrees (strong texturing and weak) were assessed. In a second step, mechanical tensile and cyclic experiences were carried out. The results were used in development of a model with a macroscopic approach. Subsequently, a sliding trace analysis technique was developed in order to identify the contribution of different sliding systems on the accommodation of plastic deformation during the tensile or cyclic loadings. The final part of PhD work was dedicated to the development of a Crystal Plasticity-Finite Element model (CPFEM) to analyze the coupled effect of the average grain sizes, their relative scattering and crystallographic textures on the mechanical behavior at different scales: microscopic (sliding mechanism), mesoscopic (grains) and macroscopic scales. The model parameters were identified using appropriate techniques for the scale transitions. The Representative Volume Element (RVE) necessary for such modeling has been optimized with two constraints: a representative number of grains and an adequate meshing in terms of numbers and type of elements. The numerical simulations were performed using Abaqus/ Standard finite element calculation code interfaced by ZMAT library
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Longhitano, Guilherme Arthur 2015. "Estudo de tratamentos térmicos e acabamentos de superfície na liga Ti-6Al-4V produzida via DMLS para aplicação em implantes." [s.n.], 2016. http://repositorio.unicamp.br/jspui/handle/REPOSIP/265833.
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Orientador: Maria Clara Filippini Ierardi<br>Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica<br>Made available in DSpace on 2018-08-26T21:12:43Z (GMT). No. of bitstreams: 1
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Previous issue date: 2016<br>Resumo: No presente trabalho, a liga de titânio Ti-6Al-4V, empregada em implantes ortopédicos permanentes ou temporários devido à sua biocompatibilidade, foi produzida a partir da manufatura aditiva utilizando o processo de Sinterização Direta de Metais por Laser (DMLS). O material foi submetido a diferentes tratamentos térmicos com o intuito de modificar suas propriedades mecânicas, e a acabamentos de jateamento, ataque químico e polimento eletroquímico para analisar os efeitos dos mesmos no acabamento de superfície. As modificações resultantes após os tratamentos térmicos e acabamentos de superfície foram analisadas por microscopia óptica, microscopia eletrônica de varredura, difração de raios-X, medidas de rugosidade e massa, microdureza Vickers, e ensaios de tração e compressão. No estudo de acabamentos de superfície, o menor valor de rugosidade foi obtido após as etapas de jateamento e ataque químico combinadas. O acabamento de jateamento é responsável por deixar uma superfície com rugosidade uniforme, enquanto o ataque químico é responsável pela limpeza da superfície e redução da rugosidade. As amostras foram submetidas aos tratamentos térmicos nas temperaturas de 850 ºC, 950 ºC e 1050 ºC durante uma hora com resfriamento em forno. Foi constatado que quanto maior a temperatura empregada, maior é a ductilidade do material e, por outro lado, menor é a resistência mecânica. Tal fato ocorreu devido à maior nucleação e crescimento da fases 'alfa' e 'beta' no material, que apresentava inicialmente uma estrutura constituída por martensita hexagonal ('alfa'). A condição de tratamento térmico a 950 ºC foi a que apresentou a melhor relação de propriedades mecânicas, satisfazendo os requerimentos da norma ASTM F136 para a utilização da liga Ti-6Al-4V em implantes<br>Abstract: In this study, the Ti-6Al-4V titanium alloy, used in permanent or temporary orthopedic implants due to its biocompatibility, was produced by additive manufacturing using the Direct Metal Laser Sintering (DMLS) process. The material was subjected to different heat treatments in order to modify their mechanical properties, and to the surface finishes of blasting, chemical etching and electropolishing to analyze their effects on surface finish. The resulting changes after the heat treatments and surface finishes were analyzed by optical microscopy, scanning electron microscopy, X-ray diffraction, roughness and mass measurements, Vickers microhardness, and tensile and compression tests. In surface finishes study, the lowest roughness value was obtained after the combined steps of blasting and chemical etching. The blasting finish is responsible for leaving a surface with uniform roughness, while the chemical etching is responsible for cleaning the surface and reducing roughness. The samples were subjected to heat treatments at temperatures of 850 °C, 950 °C and 1050 °C for one hour followed by furnace cooling. It has been found that the higher the temperature employed, the higher the ductility of the material and, on the other hand, the lower the mechanical strength. This happened due to increased nucleation and growth of 'alfa' and 'beta' phases in the material, which initially had a structure made of hexagonal martensite ('alfa'). The condition of heat treatment at 950 ° C showed the best relation of mechanical properties, meeting the requirements of ASTM F136 for the use of Ti-6Al-4V alloy in implants<br>Mestrado<br>Materiais e Processos de Fabricação<br>Mestre em Engenharia Mecânica
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Kuntz, Sarah Louise. "Feasibility of Attaining Fully Equiaxed Microstructure through Process Variable Control for Additive Manufacturing of Ti-6Al-4V." Wright State University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=wright1464557846.
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Julien, Renaud. "Comportement thermomécanique et évolution microstructurale d'un alliage Ti-6Al-4V forgé α+β, durant la trempe : expérimentations, analyses et modélisation". Thesis, Ecole nationale des Mines d'Albi-Carmaux, 2017. http://www.theses.fr/2017EMAC0001/document.
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Cette étude s'inscrit dans le cadre du projet FUI TiMaS (Titanium Machining and Simulation) dont l'objectif est de développer un outil d'analyse et d'optimisation continu du procédé de production et visant à maîtriser et à prédire la création des contraintes résiduelles pour les pièces de structure en alliage de titane. Les contraintes résiduelles peuvent être générées notamment durant la trempe qui suit les traitements thermomécaniques. L'objectif de cette étude est d’étudier le comportement mécanique ainsi que l'évolution microstructurale de l’alliage Ti-6Al-4V, induits par le refroidissement depuis le domaine α+β, et d’intégrer cela dans une démarche de modélisation. Pour cela, un moyen expérimental, composé d’une machine d'essais hydraulique et d'un chauffage par induction, a été développé afin d’analyser la réponse mécanique de l'alliage Ti-6Al-4V sous différentes conditions mécaniques et thermiques. Ce moyen a permis la réalisation d’essais de traction/relaxation/traction à différentes températures. Parallèlement, une étude par analyse de micrographies a permis de quantifier les fractions de phases α et β ainsi que les épaisseurs de lamelles αII lors du refroidissement. Les observations ont pu être confrontées aux résultats des essais mécaniques afin d’expliquer l’influence du traitement thermique sur la résistance du matériau. Deux modèles de comportement ont été proposés pour prédire la réponse thermomécanique de l’alliage Ti-6Al-4V à l'issue de cette analyse. Le premier est un modèle élasto-visco-plastique incluant un l'écrouissage isotrope prenant en compte l'adoucissement par restauration statique du matériau. Il est valable pour différentes vitesses de refroidissement. Le second est un modèle non-unifié basé sur une loi des mélanges de phases. Il reproduit plus fidèlement le comportement mécanique et permet notamment de modéliser le phénomène de yield point par l'intermédiaire du mouvement des dislocations mobiles<br>This research is part of the TiMaS project (Titanium Machining and Simulation). The main goal of this project is to develop an analysis and optimization tool of the global production process to control and assess the generation of residual stresses for titanium alloys structures parts. Residual stresses can be generated during thermal and mechanical treatment quenching steps. The main goal of this work is to study the mechanical behaviour and the microstructural evolution of Ti-6Al-4V alloy, induce by quenching from the α+β phase field, and incorporate these results in a modelling approach. For this purpose, a new experimental facility, using conventional hydraulic testing machine and induction heating, was developed to investigate the mechanical behaviour of Ti-6Al-4V alloy under different thermal and mechanical loads. This experiment has permitted to realise tensile/relaxation/tensile tests. Furthermore, an image analysis protocol was developed to study fraction of α and β phases and αII lamellae thickness. Microstructural observations can explain some aspects of the material hardening during quenching. Two mechanical behaviour models were proposed to assess the mechanical behaviour of the Ti-6Al-4V alloy. The first one is an elasto-visco-plastic model with isotropic hardening that taking account of the static recovery. It can predict the mechanical behaviour under different quenching rates. The second one is a non-unified model based on a phases mixing law. It permits a better assessment of the mechanical behaviour and allows the modelling of the yield point phenomenon by using mobile dislocations motion
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Lavogiez, Cyril. "Étude de l’effet « dwell » dans le Ti-6Al-4V : mécanismes de déformation et d’amorçage de fissures en relation avec l’orientation cristallographique locale de la phase αp Concurrent operation of slip and twinning under cycling loading of Ti-6Al-4V Analysis of deformation mechanisms operating under fatigue and dwell-fatigue loadings in an α/β titanium alloy Deformation processes at crack initiation site under cyclic loading of Ti-6Al-4V with a dwell period On the mechanism of fatigue and dwell-fatigue crack initiation in Ti-6Al-4V Why do titanium alloys withstand more strain under dwell-fatigue than under fatigue loadings". Thesis, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique, 2020. http://www.theses.fr/2020ESMA0004.
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L’introduction d’un temps de maintien à charge maximale au cours d’un chargement mécanique cyclique d’un alliage de titane (α+β), conduit à une réduction du nombre de cycles à rupture. Cet abattement de durée de vie, appelé effet «dwell», s’accompagne également d’une augmentation de la déformation plastique à rupture et d’une transition de l’amorçage des fissures fatales de la surface vers le cœur. Malgré plus de 40 ans de recherche, ce phénomène, qui est lié à la viscoplasticité des alliages de titane à température ambiante, reste mal expliqué. Dans la littérature, les efforts se sont principalement concentrés sur l’étude du mécanisme d’amorçage de fissure. Différents modèles ont été proposés mais le manque de données expérimentales statistiques sur les sites d’amorçage de fissure en dwell-fatigue, ne permet pas de converger vers un accord général. De plus, peu d’études ont porté sur l’influence du temps de maintien sur les processus de déformation, qui précèdent et sont au cœur de l’amorçage des fissures de fatigue dans les alliages de titane. Les travaux de thèse présentés se proposent ainsi d’étudier l’effet «dwell» à travers l’influence du temps de maintien sur les liens entre la plasticité et l’amorçage des fissures. Pour cela, plusieurs essais de fatigue et de dwell-fatigue ont été effectués sur un alliage Ti-6Al-4V avec une microstructure bimodale. Une étude exhaustive de l’ensemble des mécanismes de déformation de la phase αp (glissement basal, prismatique, pyramidal et , aux interfaces et maclage), résultant de champs mécaniques hétérogènes influencés par le report des contraintes entre grains voisins ou l’interaction des bandes de glissement avec un joint de grain, a d’abord été effectuée. Les techniques d’analyse EBSD et d’analyse des lignes de glissement ont été utilisées dans ce but. Les mécanismes de déformation ont été comparés à des taux de déformation plastique similaires pour différentes durées de maintien. Enfin, les configurations microstructurales d’amorçage de fissures ont été caractérisées. Un mécanisme d’amorçage de fissures nouveau a été mis en évidence en lien avec des configurations microstructurales spécifiques, en fatigue comme en dwell-fatigue et en surface comme à coeur. L’association des résultats sur les modes de déformation et l’amorçage des fissures a permis finalement de de suggérer les points où de futurs efforts pourront se concentrer<br>The introduction of a hold time at maximum stress during the loading of an (α+β) titanium alloys leads to a reduction in the number of cycles to failure. This life debit, called “dwell effect” goes in hand with a higher plastic strain uptake at failure and a transition of the fatal crack initiation from surface to the volume. Despite more than 40 years of scientific research, the origins of this phenomenon, which is closely linked to the viscoplastic behavior of titanium alloy at room temperature, remains unclear. In the literature, the main efforts were focused on elucidating the mechanism of crack initiation. Several models have been proposed but the lack of experimental data with a statistical significance about the crack initiation sites under dwell-fatigue loading prevented to reach a general agreement. Moreover, few studies have investigated the influence of the hold time at maximum stress on the deformation mechanisms, although they precede crack initiation and govern the associated mechanisms under cyclic loading. The presented work is a study of the dwell effect through the analysis of the influence of the hold time at maximum stress in order to clarify the link between plasticity and crack initiation. In this aim, several fatigue and dwell fatigue tests have been performed on a Ti-6Al-4V alloy with a bimodal microstructure. An extensive study of deformation mechanism of the αp phase in relation to the heterogeneous mechanical fields influenced by load shedding between neighboring grains or interactions between slip bands and grain boundaries, has been performed. EBSD analyses and slip trace analysis were employed in this aim. The deformation mechanisms identified by these techniques (basal, prismatic, pyramidal and slip, interface sliding and twinning) were compared for different hold periods at maximum stress at similar cumulated plastic strain. Then, a microstructural configuration promoting crack initiation has been identified. It enabled to propose a new crack initiation mechanism. In addition, this mechanism is unique for crack initiation under fatigue and dwell-fatigue loadings and for surface and subsurface crack initiation. The combination of the results obtained on plasticity and crack initiation clarifies some features of the dwell effect and suggests some outlooks for future work
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Šlais, Miroslav. "Studium vlivu rychlostních a teplotních parametrů na tvařitelnost Ti slitin." Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2012. http://www.nusl.cz/ntk/nusl-234028.
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The PhD thesis deals with the influence of temperature and strain rate on the mechanical behaviour of the Ti-6Al-4V titanium alloy. After verification tests under static loading conditions, the samples were deformed at high strain rates and elevated temperatures, using device for Hopkinson pressure bar test. The result is dependence of stress and strain rate on strain in the temperature range of 20 to 500°C. The deformed shape of specimen from the Taylor anvil test is compared with the results of the simulation in the Ansys – LS Dyna software. The parameters of Johnson-Cook equation were determined from these experiments. Also, the influence of loading conditions on the microstructure was studied. Both optical and scanning electron microscopes were used for the observations. During the research, some adjustments to the experimental devices were made in order to suppress the high-frequency components and noise in the recorded pulses. A functional tensile test adapter for the Hopkinson test was developed; it is registered under No. 2007/008 at the Technology Transfer Office of BUT.
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Sirvin, Quentin. "Etude du comportement mécanique de tôles en alliage de titane et des paramètres procédé dans les opérations d'emboutissage à hautes températures." Thesis, Ecole nationale des Mines d'Albi-Carmaux, 2018. http://www.theses.fr/2018EMAC0003.
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Dans l'industrie aéronautique, les alliages de titane sont utilisés pour leur excellent comportement mécanique associé à une faible masse volumique. Ils sont largement employés sous forme de tôles dont la mise en forme peut se faire par le biais de trois procédés : à température ambiante par opération d'emboutissage, à très hautes températures (T≈900°C) par formage superplastique (SPF) et à des températures intermédiaires (T=730°C, 880°C) par formage à chaud (HF). Le projet repose sur le développement du procédé d'emboutissage à chaud d'une tôle d'alliage de titane Ti-6Al-4V en conditions isothermes à des températures inférieures à 700°C. Par conséquent, la détermination des paramètres procédés et matériaux constitue une étape importante pour la mise en œuvre de simulations numériques et contribue à la réussite des opérations d'emboutissage de pièces industrielles. Ces paramètres procédés sont liés à la vitesse du poinçon, aux efforts de serre-flan et au frottement induit entre le flan et l'outillage. Leur analyse a permis de déterminer deux niveaux de températures (400°C et 500°C) offrant une chute drastique du coût énergétique, en comparaison des procédés HF ou SPF, tout en conservant des niveaux d'allongement suffisants. Les paramètres matériaux influençant le comportement de l'alliage sont analysés et quantifiés. Ils peuvent être influencés par plusieurs mécanismes : élasticité, viscosité, anisotropie (Hill48, Barlat91) et nature de l’écrouissage (isotrope, cinématique). Dans cette étude, un modèle de comportement élasto-viscoplastique anisotrope, capable de considérer les trajets de chargement subis par la tôle lors de sa mise en forme, a été formulé pour les deux niveaux de température. L’implantation du modèle de comportement a été réalisée dans le code de calcul éléments finis Abaqus/Standard 6.14® interfacé avec le logiciel ZMAT®. Elle a permis d’une part des simulations d’emboutissage de profil Omega pour lesquelles des comparaisons avec les expériences ont été réalisées et d’autre part, des calculs sur une pièce de forme complexe<br>In the aerospace industry, titanium alloys are used for their excellent mechanical behavior associated with low density. They are widely available in sheet form and the final shape can be obtained through three processes: at room temperature by stamping operation, at very high temperatures (T≈900°C) by superplastic forming (SPF) and at intermediate temperature (T=730°C, 880°C) by hot forming (HF). The project is based on the development of the hot stamping process of Ti-6Al-4V titanium alloy sheet under isothermal conditions at temperatures below than 700°C. Therefore, the determination of the process and material parameters constitutes an important stage for implementing the numerical simulation while contributing to the success of the stamping operation at the scale of an industrial part. The process parameters are related to the punch speed, the blank holder forces and the friction induced between the sheet and the tool. Their analysis allowed to determine two temperature levels (400°C et 500°C) leading a drastic drop in energy cost, compared to HF or SPF processes, while maintaining enough elongation levels. The material parameters influencing the behavior of the alloy are analyzed and quantified. They can be influenced by several mechanisms: elasticity, viscosity, anisotropy (Hill48, Barlat91) and nature of hardening (isotropic, kinematic). In this study, an anisotropic elasto-viscoplastic behavior model, able to consider the loading path undergone by sheet during forming, has been formulated for both temperature levels. The implementation of the behavior model is achieved in Abaqus/Standard 6.14® Finite Element code with the material library plugin ZMAT®. It enables, on the one hand, stamping numerical simulations of a simple shape Omega profile for which experimental comparisons were done, on the other hand, calculations on an industrial part with a complex shape
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Cellier, Adrien. "Etude du fraisage de l'alliage de titane Ti-6AI-4V : influence des angles de coupe et des rayons de bec sur l'intégrité de surface et la limite d'endurance des pièces." Thesis, Tours, 2013. http://www.theses.fr/2013TOUR4024/document.
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Cette étude s’est focalisée sur l’influence d’une opération de fraisage sur l’intégrité de surface et la durée de vie en fatigue des pièces usinées en titane (Ti-6Al-4V). L’influence des paramètres géométriques tels que les angles de coupe et les rayons de bec sur la performance de l’outil à savoir la durée de vie de l’outil est analysée. Une deuxième partie est consacrée à l’influence des paramètres géométriques sur l’intégrité de surface définie par des facteurs tels que la topographie, les contraintes résiduelles, la dureté et la microstructure. Afin de déterminer la nature des contraintes résiduelles, une approche thermomécanique a été utilisée. Une relation entre les contraintes résiduelles et la dureté sous la surface usinée est établie. Une dernière partie est dédiée à la l’étude de la fatigue des pièces en titane usinées selon les différents paramètres géométriques. Une comparaison des limites d’endurance expérimentales et analytiques issue de la littérature a permis de déterminer les paramètres influents de l’intégrité de surface sur la performance en fatigue. Une analyse fractographique a révélé les phénomènes liés à l’usinage influençant la rupture du matériau<br>This study is carried out on the influence of milling process on surface integrity and fatigue life of a titanium alloy (Ti-6Al-4V). Geometric parameters like cutting angles and nose radius are investigated. In the first part, the observation is focused on tool life. The second part is dedicated to the influence of geometric parameters on surface integrity which is defined by topography, residual stress, hardness and microstructure. To determine the nature of the residual stresses a thermomechanical approach is used. A relation between residual stress and hardness is established. The last part deals with the study of the fatigue of milled titanium samples. A comparison is made between experimental fatigue limit and analytical fatigue limit of a model from literature. With this comparison, the most influential factor of surface integrity on fatigue limit is determined. A fractography analysis reveals the phenomenon related to milling process which can influence the material rupture
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GHAT, MOHAMED SAAD SHEHATA RIZK. "Physical modelling of the high temperature deformation of complex microstructure materials for aeronautical applications." Doctoral thesis, Università Politecnica delle Marche, 2020. http://hdl.handle.net/11566/274085.
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Oggi l'industria aerospaziale sta crescendo rapidamente nello sviluppo del componente meccanico per la parte calda del motore a reazione. La previsione del comportamento dinamico dei metalli è di solito studiata da modelli fenomenologici. In questo studio, abbiamo descritto il comportamento della deformazione a caldo usando diversi approcci per il modello costitutivo: equazione di Hansel e spittle, equazione di Garofalo e modellazione di base. Nel presente lavoro di dottorato sono stati utilizzati tre diversi metalli (Inconel 718, Ti-6Al-4V e AA2024 - T3) che sono ampiamente utilizzati nell'industria aerospaziale. Un modello di base è stato applicato al Ni puro e quindi a una superlega monofase. Nel caso della lega Ti-6Al-4V, il comportamento alla deformazione a caldo è stato studiato mediante test di compressione a caldo nel dominio della fase β. Sono stati analizzati gli effetti dei parametri di deformazione a caldo (temperatura di deformazione e velocità di deformazione) sullo stress del flusso. È stato utilizzato un modello fenomenologico basato sull'equazione di Hansel e Spittel per ottenere una descrizione abbastanza accurata delle curve di flusso per temperature di processo comprese tra 1010 e 1150 ºC e velocità di deformazione di 100 e 0,001 s-¹. Il modello utilizzato ha dato un risultato accurato di esperimenti eccellenti. La deformazione ad alta temperatura della superlega, una soluzione trattata IN718, è stata studiata mediante test di torsione in regime ad alta temperatura (1000-1100 ° C). La dipendenza dallo stress del picco di flusso dalla velocità di deformazione e dalla temperatura è stata descritta da equazioni costitutive basate fisicamente, che hanno tenuto conto sia dell'indurimento della dislocazione che del rafforzamento della soluzione solida e rappresentano un progresso sostanziale rispetto ai modelli fenomenologici, sebbene, nella forma attuale, non può dare la forma completa delle curve di flusso. È stata studiata la risposta al creep per la lega AA2024-T3 prodotta da un processo di agitazione per attrito (FSP), la stessa modellazione del creep basata sull'approccio teorico. La variazione della durezza con la durata del creep è stata utilizzata per quantificare il termine di rafforzamento delle particelle.<br>Today aerospace industry is growing fast on developing the mechanical component for the hot section part of the jet engine. The prediction of the dynamic behavior of metals is usually investigated by phenomenological models. In this study, we described the hot deformation behavior by using different approaches for constitutive model: Hansel and spittle equation, Garofalo equation and basic modelling. In the present PhD work, three different metals were used (Inconel 718, Ti-6Al-4V and AA2024 – T3) which are extensively used in the aerospace industry. A basic model was applied to pure Ni and then to a single-phase superalloy. In the case of Ti-6Al-4V alloy, the hot deformation behavior was studied by hot compression test in β phase domain. The effects of hot deformation parameters (deformation temperature and strain rate) on flow stress were analyzed. A phenomenological model based on the Hansel and Spittel equation was used to obtain a quite accurate description of the flow curves for processing temperatures between 1010 and 1150 ºC and strain rates of 100 and 0.001 s-¹. The model used gave an accurate excellent experiments result. The high temperature deformation of the superalloy, a solution treated IN718, was investigated by torsion testing in a high-temperature regime (1000–1100 °C). The peak-flow stress dependence on strain-rate and temperature was described by a physically-based constitutive equations, which took into account both dislocation hardening and solid solution strengthening, and represents a substantial advancement over phenomenological models, although, in the present form, it cannot give the full shape of the flow curves.The creep response for AA2024-T3 alloy produced by a friction stir processing (FSP) has been investigated, the same creep modeling based on the theoretical approach. The hardness variation with creep duration was used to quantify the particle strengthening term.
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Weaver, Jordan S. "Hierarchical and high throughput mechanical characterization of titanium alloys using spherical indentation stress-strain curves." Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/54398.
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Recent work has shown the capability of spherical nanoindentation to capture local structure-property relationships in polycrystalline cubic metals by measuring indentation stiffness and yield strength from stress-strain curves as a function of the local microstructure in the indentation zone. However, these protocols capture structure-property relationships at only one level of the material hierarchy (e.g., single grains). Thus it is still very difficult to infer bulk structure-property relationships using these indentation protocols, which is mainly due to a lack of understanding indentation length scale effects and the important role played by structural hierarchy (i.e., unique structural features at different length scales). It is the goal of this work to extend these protocols to systematically study length scale effects of mechanical properties (e.g., indentation stiffness and yield strength) in titanium alloys. Alpha-beta titanium alloys were chosen because they display a rich variety of two phase microstructures and structural hierarchy and are well documented in literature. Firstly, nanoindentation protocols are extended to characterize the elastic and plastic anisotropy of a hexagonally close packed metal (alpha titanium in commercially pure and alloy Ti-6Al-4V) and a two phase microstructure (alpha-beta colony in Ti-6Al-4V). Secondly, spherical microindentation stress-strain protocols are developed and employed to characterize polycrystalline volumes in three titanium alloys (commercially pure, Ti-6Al-4V, and Ti18). The results of these major advances in indentation protocols and systematic study of length scale effects on the mechanical properties in Ti-6Al-4V will be presented and discussed along with applications demonstrating their high throughput nature to rapidly explore alloy development.
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Lovrich, Neil Robert. "Fretting Fatigue of Ti-6Al-4V: Experimental Characterization and Simple Design Parameter." Thesis, Available online, Georgia Institute of Technology, 2004:, 2004. http://etd.gatech.edu/theses/available/etd-07072004-113607/unrestricted/lovrich%5Fneil%5Fr%5F200408%5Fmast.pdf.
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Thesis (M.S.)--Mechanical Engineering, Georgia Institute of Technology, 2005. Directed by Richard Neu.<br>Johnson, Steven, Committee Member ; McDowell, David, Committee Member ; Neu, Richard, Committee Chair. Includes bibliographical references.
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Hayes, Brian J. "Characterization of Ti-6Al-4V Produced Via Electron Beam Additive Manufacturing." Thesis, University of North Texas, 2015. https://digital.library.unt.edu/ark:/67531/metadc822771/.
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In recent years, additive manufacturing (AM) has become an increasingly promising method used for the production of structural metallic components. There are a number of reasons why AM methods are attractive, including the ability to produce complex geometries into a near-net shape and the rapid transition from design to production. Ti-6Al-4V is a titanium alloy frequently used in the aerospace industry which is receiving considerable attention as a good candidate for processing via electron beam additive manufacturing (EBAM). The Sciaky EBAM method combines a high-powered electron beam, weld-wire feedstock, and a large build chamber, enabling the production of large structural components. In order to gain wide acceptance of EBAM of Ti-6Al-4V as a viable manufacturing method, it is important to understand broadly the microstructural features that are present in large-scale depositions, including specifically: the morphology, distribution and texture of the phases present. To achieve such an understanding, stereological methods were used to populate a database quantifying key microstructural features in Ti-6Al-4V including volume fraction of phases, a lath width, colony scale factor, and volume fraction of basket weave type microstructure. Microstructural features unique to AM, such as elongated grains and banded structures, were also characterized. Hardness and tensile testing were conducted and the results were related to the microstructural morphology and sample orientation. Lastly, fractured surfaces and defects were investigated. The results of these activities provide insight into the process-structure-properties relationships found in EBAM processed Ti-6Al-4V.
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Riaz, Muhammad Qasim. "Influence of Biochemical Environments on Surface Fatigue of Additive Manufactured Ti-6Al-4V." Youngstown State University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1485534165584066.
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Collier, Charles Andrew. "Osteoblast responses to surface characteristics of plasma electrolytic oxidation coatings on Ti-6Al-4V." Thesis, University of Cambridge, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.609736.
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Lunt, David. "The effect of macrozones in Ti-6Al-4V on the strain localisation behaviour." Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/the-effect-of-macrozones-in-ti6al4v-on-the-strain-localisation-behaviour(f1b4158e-d1f1-4e7b-b32f-91120c7e3cce).html.
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Ti-6Al-4V is the most widely used titanium alloy and is typically used in stages of gas turbine engines, due to its high strength-to-weight ratio, corrosion resistance and high strength at moderate temperatures. However, the alloy is susceptible to the development of strong textures during thermomechanical processing that leads to a preferred crystallographic orientation. These are referred to as macrozones and are thought to develop during the β to α phase transformation, as a result of the retention of large prior β grains during processing and variant selection. Macrozones are clusters of neighbouring grains with a common crystallographic orientation that may act as one single grain during loading and have been shown to cause scatter in the fatigue life. The focus of the current work was based on the analysing the strain behaviour of soft, hard and no macrozones within the microstructure, during various loading conditions. The local strain behaviour was studied at a micro and nanoscale, using the digital image correlation (DIC) technique, which utilises microstructural images recorded during mechanical loading. On a microscale, the no-macrozone and strong-macrozone condition loaded at 0% exhibited homogeneous strain behaviour. The strong-macrozone condition loaded at 45% and 90% to the extrusion direction, respectively, developed pronounced high strain bands correlating to regions that were favourably oriented for prismatic and basal slip, respectively. Characterisation of the slip bands provided a detailed understanding of the deformation behaviour at the nanoscale and the slip system was subsequently determined for each grain using slip trace analysis. Prismatic slip was the dominant slip system in all conditions, particularly in the soft-oriented macrozone regions of the strong-macrozone condition loaded at 45 degrees. Shear strains of 10 times the appliedstrain were observed. Further investigations on the strong-macrozone condition loaded at 45 degrees to ED during standard and dwell fatigue demonstrated early failure in the dwell sample, with higher strain accumulation for dwell.
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Su, Wiliam Tean 1986. "Manufatura aditiva da liga Ti-6Al-4V aplicada em uma biela automotiva." [s.n.], 2013. http://repositorio.unicamp.br/jspui/handle/REPOSIP/263584.
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Orientador: Cecília Amélia de Carvalho Zavaglia, Maria Aparecida Larosa<br>Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica<br>Made available in DSpace on 2018-08-23T16:17:14Z (GMT). No. of bitstreams: 1
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Previous issue date: 2013<br>Resumo: Atualmente, o mercado automotivo tem buscado cada vez mais a redução de peso e aumento de resistência mecânica de seus componentes. Dentro deste contexto, este trabalho tem como objetivo verificar se uma biela automotiva feita da liga de titânio Ti-6Al-4V obtida pelo processo de manufatura aditiva chamado Sinterização Direta de Metais por Laser (DMLS) apresenta os mesmos resultados estruturais que uma biela de Ti-6Al-4V laminada e recozida (comercial) ou que uma biela feita de aço C70, bastante utilizada no mercado. A liga Ti-6Al-4V é utilizada principalmente nas áreas aeronáutica e biomédica, mas também possui aplicações na indústria automotiva, principalmente no segmento de alta performance, graças a fatores como boa resistência mecânica, excelente resistência à corrosão e baixa densidade. As características mecânicas e microestruturais de amostras da liga Ti-6Al-4V prototipada por DMLS e de amostras da liga Ti-6Al-4V laminada e recozida foram avaliadas e comparadas através de ensaios de tração e microdureza, de análises em microscópio óptico e eletrônico de varredura (para a verificação da microestrutura e da porosidade), de ensaios de difração de raios-X (DRX) (para a análise das fases presentes no material), da análise da composição química por espectroscopia de energia dispersiva (EDS) e da análise de densidade pelo princípio de Arquimedes. Bielas de Ti-6Al-4V também foram produzidas por DMLS e ensaios de tração experimentais foram realizados, simulando uma condição de contorno típica utilizada em desenvolvimentos de bielas pela indústria automotiva. Com base nos resultados experimentais, foram realizadas análises de elementos finitos utilizando a mesma condição de contorno dos ensaios, com o intuito de se obter uma correlação entre os resultados experimentais e os virtuais. De uma maneira geral, todos os resultados indicam que a biela de Ti-6Al-4V produzida pelo processo DMLS possui um comportamento estrutural similar à biela de Ti-6Al-4V laminada e recozida<br>Abstract: Nowadays, the automotive market has been looking for more and more lightweight and better strength components. In this context, the objective of this work is to verify if a connecting rod made of the titanium alloy Ti-6Al-4V produced by an additive manufacturing process named Direct Metal Laser Sintering (DMLS) would have equivalent structural results of a connecting rod made of rolled annealed Ti-6AL-4V or even the C70 steel (widely used on the market for this application). This Titanium alloy is primary used in aerospace and biomedical areas, but is also used in the automotive industry, especially on the high performance segment, due to factors like good mechanical strength, excellent corrosion resistance and low density. The mechanical and microstrutural properties of Ti-6Al-4V samples obtained by DMLS and rolling and annealing processes were compared through the realization of tensile and micro hardness tests and through the microstructural characterization, composed of scanning electron microscopy (microstructure verification), optical microscopy (porosity verification), X-ray diffraction analysis for phases quantification, energy dispersive spectroscopy (chemical composition verification) and density analysis using the Arquimedes principle. Ti-6Al-4V connecting rods were also produced by the DMLS process and tensile experimental tests were performed using the same boundary condition as commonly seen on connecting rod development at automotive industry. Based on the experimental results, finite element analyses were performed in order to correlate the experimental and the virtual results. Generally, all the results indicate that the Ti-6Al-4V connecting rod produced by DMLS process has a structural behavior similar to the Ti-6Al-4V connecting rod produced by rolling and annealing process<br>Mestrado<br>Materiais e Processos de Fabricação<br>Mestre em Engenharia Mecânica
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Antonialli, Armando Italo Sette. "Uma contribuição ao fresamento frontal da liga de titanio Ti-6Al-4V." [s.n.], 2009. http://repositorio.unicamp.br/jspui/handle/REPOSIP/264153.
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Orientador: Anselmo Eduardo Diniz<br>Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica<br>Made available in DSpace on 2018-08-12T21:04:08Z (GMT). No. of bitstreams: 1
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Previous issue date: 2009<br>Resumo: As ligas de titânio apresentam baixa usinabilidade devido à reduzida condutividade térmica, à manutenção de suas propriedades mecânicas em altas temperaturas, à elevada afinidade química com os materiais de ferramentas e ao baixo módulo de elasticidade. Esta última característica promove instabilidade da espessura de corte, o que se traduz em altos níveis de vibração, especialmente em processos de usinagem caracterizados por corte interrompido. Este trabalho trata da otimização do fresamento frontal da liga de titânio Ti-6Al-4V a partir da minimização da vibração da ferramenta através de variações do ângulo de posição da ferramenta e do ângulo de contato entre o inserto e o corpo de prova. Os resultados mostram que a utilização de um ângulo de posição reduzido prolonga a vida da ferramenta por associar a maior parte do carregamento radial a freqüências muito baixas, nas quais a ferramenta se comporta como um corpo rígido. O emprego de um ângulo de contato reduzido, por outro lado, é extremamente danoso à vida da ferramenta, pois a entrada do inserto no corpo de prova se dá em condições adversas. Attrition seguido de microlascamentos da aresta, nas condições em que houve vibração excessiva ou intenso choque na entrada do inserto, e difusão, nas condições dinamicamente mais estáveis, foram os principais mecanismos de desgaste de ferramenta verificados neste trabalho<br>Abstract: Titanium alloys present poor machinability because of their low thermal conductivity, their ability to keep good mechanical properties at high temperatures, their high chemical affinity to tool materials and their low Young modulus. This last characteristic generates instabilities of cutting thickness, which means high vibration levels, especially in machining processes involving interrupted cutting. This work studies Ti-6Al-4V titanium alloy face milling optimization by tool vibration reduction using different tool entering angles and different radial immersion angles between tool and workpiece. Results show that using low entering angle do extends tool life due to associating most radial load with very low frequencies, in which tool behaves like a rigid body. On the other hand, using low radial immersion angle extremely impairs tool life, as tool insert enters the workpiece on adverse conditions. Attrition followed by cutting edge microchipping, on experiments in which high vibration levels or intense shock on tool insert enter where found, and diffusion, on experiments dynamically more stable, were the main tool wear mechanisms observed in this work<br>Mestrado<br>Materiais e Processos de Fabricação<br>Mestre em Engenharia Mecânica
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Simonelli, Marco. "Microstructure evolution and mechanical properties of selective laser melted Ti-6Al-4V." Thesis, Loughborough University, 2014. https://dspace.lboro.ac.uk/2134/15070.
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Selective laser melting (SLM) has been shown to be an attractive manufacturing route for the production of ??/?? titanium alloys, and in particular Ti-6Al-4V. A thorough understanding of the relationship between the process, microstructure and mechanical properties of the components produced by this technology is however crucial for the establishment of SLM as an alternative manufacturing route. The purpose of the present study is thus to determine the microstructure evolution, crystallographic texture and the mechanical properties of SLM Ti-6Al-4V. The effect of several processing parameters on the density and the microstructure of the SLM samples were initially investigated. It was found that different sets of process parameters can be used to fabricate near fully dense components. It was found that the samples built using the optimised process window consist exclusively of ????? martensitic phase precipitated from prior ?? columnar grains. It was observed that the ?? grain solidification is influenced by the laser scan strategy and that the ?? phase has a strong <001> texture along its grain growth direction. The ????? martensitic laths that originate from the parent ?? grains precipitate according to the Burgers orientation relationship. It was found that ????? laths clusters from the same ?? grain have a specific misorientation that minimise the local shape strain. Texture inheritance across successive deposited layers was also observed and discussed in relation to various variant selection mechanisms. The mechanical properties of as-built and stress relieved SLM Ti-6Al-4V built using the same optimised process parameters were then investigated. It was found that the build orientation affects the tensile properties, and in particular the ductility of the samples. Samples built perpendicularly to the building direction showed higher ductility than those built in the vertical orientation. It was also observed that a stress relief heat treatment was beneficial to the mechanical properties of SLM Ti-6Al-4V. The ductility of the stress relieved samples was indeed higher than those found in the as-built condition. It was found that the predominant fracture mode during tensile testing is inter-granular. In terms of high-cycle fatigue, it was found that SLM Ti-6Al-4V is comparable to HIPed cast Ti-6Al-4V but it has a significantly lower fatigue resistance than that of wrought and annealed alloys. It was observed that porosity and the elongated prior ?? grain boundaries decrease substantially the fatigue life of the components. Cracks propagate either by fatigue striation or ductile tearing mechanisms. Using alternative laser scan strategies it was possible to control the microstructure of the as-built samples. It was observed that the laser scan vector length influences several microstructural features, such as the width of the prior ?? grains and the thickness of the ????? laths. It was found that re-melting the same layer has instead little effect on the microstructure. A novel laser scan strategy characterised by much lower laser power and scan speed than those typically used in SLM enabled finally to fabricate SLM Ti-6Al-4V with a microstructure close to that of conventionally manufactured Ti-6Al-4V. This study investigates for the first time the crystallographic texture evolution in Ti-6Al-4V manufactured by SLM. Further, this research presents for the first time the effect of the characteristic microstructure and crystallographic texture on the mechanical properties and fracture of SLM Ti-6Al-4V. Lastly, for the first time this research shows examples of microstructural control during the SLM fabrication of the same alloy using long laser dwell times.
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Rocha, Sicknan Soares da [UNESP]. "Efeito de tratamentos térmicos na resistência à tração e na dureza Vickers do Ti c.p. e da liga Ti-6Al-4V obtidos por fundição odontológica." Universidade Estadual Paulista (UNESP), 2002. http://hdl.handle.net/11449/97321.
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rocha_ss_me_arafo.pdf: 674518 bytes, checksum: 9888e8462ea32b3c607f867bc951afd1 (MD5)<br>O objetivo desta investigação foi determinar se os tratamentos térmicos podem alterar a resistência à tração e a dureza Vickers do Ti c.p. e da liga Ti-6Al-4V. Trinta corpos-de-prova na forma de halteres com 3,0 mm no segmento central e 42 mm de comprimento, obtidos por meio de uma matriz de alumínio, foram fundidos no sistema Rematitan. Os corpos-de-prova de Ti c.p. e Ti-6Al-4V foram divididos aleatoriamente em três grupos de 10 cada, e submetidos às seguintes condições de tratamento térmico: (1) controle; (2) T1 - aquecimento a 750ºC/2 h; (3) T2 - recozimento a 955ºC/1 h e envelhecimento a 620ºC/2 h. Ambos, aquecimento e resfriamento, foram realizados em atmosfera controlada de argônio. O ensaio de tração foi efetivado na máquina de testes mecânicos MTS modelo 810 à velocidade de 1,0 mm/min. Após o teste de tração uma das extremidades do corpo-de-prova foi embutida em resina acrílica, regularizada e polida antes da medida da dureza Vickers no durômetro Micromet 2100. As médias de resistência à tração e dureza Vickers foram comparadas estatisticamente usando o teste não-paramétrico de Kluskall-Wallis. Nos grupos de Ti c.p. não foram observadas diferenças significativas na resistência à tração, entretanto, na dureza Vickers os resultados do grupo T2 foram significativamente maiores que os outros grupos, que se mostraram iguais entre si. Na liga Ti-6Al-4V os grupos controle e T1 revelaram igualdade estatística em relação à resistência à tração, e significativamente superiores ao grupo T2. Quanto à dureza Vickers, diferenças estatisticamente significantes foram observadas entre os três grupos de tratamento térmico: T2>T1>controle. Não foi observada correlação entre as propriedades de resistência à tração e dureza Vickers....<br>The aim of this investigation was to determine whether heat treatments could change the tensile strength and Vickers hardness of CP Ti and Ti-6Al-4V alloy castings. Thirty dumbbell rods, 3.0 mm in diameter at the central segment and 42 mm in length, obtained from an aluminum matrix, were cast for each metal in the Rematitan system. The specimens of CP Ti and of alloy Ti-6Al-4V, were divided randomly into three groups of ten each; then submitted to the following heat treatments: (1) control group, without heat treatment; (2) T2 - heat at 750ºC for 2 h; (3) annealing at 955ºC for 1 h and aged at 620ºC for 2 h. The heat treatments, as well as the cooling process were conducted in the furnace with argon atmosphere. The tensile strength was measured by means of a universal testing machine, MTS model 810, at a strain of 1.0 mm/min. After the tensile testing the specimens were embedded in acrylic resin, grounded and polished prior to hardness measurements, using the Vickers tester Micromet 2100. The means and standard deviations of tensile strength and Vickers hardness were statistically compared using Kruskal-Wallis non-parametric test at a=0.05 significance level. In CP Ti groups, no statistically significant differences in tensile strength were observed; however, in Vickers hardness the results of group T2 were significantly higher than the other groups, which showed similar mean values among themselves. In Ti-6Al-4V alloy, the control and T1 groups revealed statistically higher tensile strength when compared to T2 group, with no significant difference between control and T1 group. Regarding Vickers hardness, statistically significant differences were observed among the three heat-treatment groups: T2>T1>control...(Complete abstract, click electronic access below)
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Colafemina, João Paulo. "Estudo da microusinabilidade do Ti (CP) e da liga Ti-6Al-4V no torneamento com ferramenta de diamante." Universidade de São Paulo, 2005. http://www.teses.usp.br/teses/disponiveis/18/18135/tde-15062007-150756/.
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Dentre as diversas aplicações onde o titânio e suas ligas são empregados destaca-se a indústria aeroespacial, pois suas excelentes propriedades de resistência à fratura, resistência à corrosão e razão resistência/peso, a qual se mantém a elevadas temperaturas, torna imprescindível o seu uso. Por outro lado, a usinabilidade de titânio e suas ligas é geralmente considerada como sendo ruim devido a algumas características, como por exemplo, baixa condutividade térmica, reatividade química com a maioria dos materiais ferramenta, alta resistência em altas temperaturas e baixo módulo de elasticidade, entre outras. Por esses motivos, foram realizadas operações de torneamento de ultraprecisão com ferramenta de diamante, a fim de determinar o comportamento do Ti comercialmente puro (CP) e sua liga mais comercialmente usada (Ti-6Al-4V). Os ensaios foram feitos com uso de fluido de corte aplicado em forma de névoa (~100ml/hora) em uma máquina-ferramenta com alta rigidez e precisão de posicionamento (resolução 10 nanômetros). As técnicas de caracterização de superfície usadas foram: microscopia eletrônica de varredura, óptica e de força atômica, microdureza Vickers, perfilometria mecânica e óptica. Os danos superficiais observados devido à interação ferramenta/material foram associados ao fenômeno conhecido como delaminação. Os resultados obtidos de microdureza superficial mostraram aumentos que chegaram à ordem de 85% para o Ti (CP) e de 77% para o Ti-6Al-4V. Os menores valores encontrados para Ra ficaram em torno de 30 nm para o Ti (CP) e de 46 nm para o Ti-6Al-4V enquanto os menores valores encontrados de Rt para o Ti(CP) foi de 590 nm e para o Ti-6Al-4V foi de 416 nm sob as mesmas condições de usinagem. Portanto, a usinagem de ultraprecisão se torna uma alternativa eficiente no uso de operações de acabamento melhorando a integridade superficial do Ti (CP) e suas ligas.<br>Among the various applications where titanium and its alloys are employed, the aeronautic industry is one of the most important, because of their excellent properties such as fracture strength, corrosion resistance and high strength to weight ratio, which is maintained at high temperatures. However, the machinability of titanium and its alloys is generally considered poor due to some of their characteristics as low thermal conductivity, chemical reactivity with most tool materials, high resistance to mechanical work at high temperature and low young\'s modulus, etc. Ultraprecision diamond turning has been carried out in order to determine the behaviour of commercially pure Ti and the most used alloy ((Ti-6Al-4V). Cutting fluid has been applied in the form of mist (~100 ml/hora) during the experiments. A high stiffness and high precision machine tool has been used (positioning precision of 10 nm). Scanning electron microscopy, optical microscopy, atomic force microscopy, Vickers microhardness test and contact and optical perfilometry have been used to characterize the machined surfaces. The surface damage observed due to the interaction tool-workpiece have been associated with the known phenomenon of delamination. The microhardness results presented an increase of the order of 85% for Ti (CP) and of 77% for the Ti-6Al-4V alloy after machining. The lowest values for Ra are around 30 nm for Ti (CP) and 46 nm for Ti-6Al-4V and the lowest values of Rt for Ti (CP) are about 590 nm and 416 nm for the Ti-6Al-4V, for the same conditions. The ultraprecision machining of titanium and its alloys may be an efficient alternative for finish operations resulting in better surface integrity.
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Pilchak, Adam L. "The effect of friction stir processing on the microstructure, mechanical properties and fracture behavior of investment cast Ti-6Al-4V." Columbus, Ohio : Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view.cgi?acc%5Fnum=osu1243874522.
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Zhang, Ming. "Crystal plasticity modeling of Ti-6Al-4V and its application in cyclic and fretting fatigue analysis." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/22669.
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Thesis (Ph. D.)--Mechanical Engineering, Georgia Institute of Technology, 2008.<br>Committee Chair: David. L. McDowell; Committee Member: Min Zhou; Committee Member: Naresh N. Thadhani; Committee Member: Rami M. Haj-Ali; Committee Member: Richard W. Neu.
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Sarsfield, Helen. "Development of a three dimensional grain structure submodel : experimental characterisation and numerical modelling of Ti-6Al-4V at elevated strain rates." Thesis, University of Oxford, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.670174.
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