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1
Allan, Michael MacDonald. "β-recrystallisation characteristics of α + β titanium alloys for aerospace applications." Thesis, University of Strathclyde, 2016. http://digitool.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=27502.
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Tourneroche, Paul. "Développement de mélanges chargés en poudres d'aluminure de titane pour moulage par injection et applications aéronautiques." Thesis, Besançon, 2016. http://www.theses.fr/2016BESA2057.
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La réduction de l’impact des activités humaines sur l’environnement est au sujet de nombreux programmes de recherche. Ainsi, dans le domaine du transport aérien a été créé le projet Clean-Sky, regroupant les thèmes de recherche associés. La thèse, partie de ce dernier, a pour objectif de réduire l’impact environnemental de la production de composants en alliages avancés à base de Titane. La production actuelle ayant une empreinte écologique non négligeable, un procédé de fabrication alternatif est étudié, il s’agit du moulage par injection de poudres métalliques. La première partie de cette consiste donc en la recherche d’une formulation de mélange optimale parmi les solutions classiques et innovantes. Elles sont triées en fonction de leurs aptitudes, déterminées par caractérisations physico-chimiques, à assurer le bon déroulement de chaque étape du procédé. Un nombre réduit de solution étant ainsi dégagé, il s’agit de passer aux étapes d’injection, de déliantage et de frittage. Plusieurs géométries de pièces sont testées dans chacun de ces cas, afin de valider l’adaptation aux différentes contraintes imposées. Lors de ces trois phases, des analyses physico-chimiques complètes permettent de mettre en avant la ou les formulations les plus aptes à permettre la production de ces composants. Une fois la solution fixée, chaque étape du procédé est optimisées, afin de faciliter le transfert industriel et d’assurer la rentabilité du nouveau processus de fabrication. Ces travaux de doctorat ont permis de mettre en avant deux formulations, répondant aux critères définis en début de thèse. Les étapes de mélange, injection, déliantage et frittage ont été optimisées et le transfert industriel est possibleReducing the ecological footprint of human activities is, today, the aim of most of the research programs. In Europe, the « Clean Sky » project funds research activities to make air transport « greener ». This PhD, being part of it, is about improving production of Titanium Aluminide based components. Nowadays production having a strong environmental impact, an alternative way has been investigated: metal injection molding. The first step of this work was focused on a bibliographic study, to select relevant, common and innovative mixtures to be used in the process. Throughout the process, these mixtures have been tested, physically and chemically analyzed, to get data about the optimal mixture. Several components geometries have been tested, during injection, debinding, and sintering steps. Once the mixture(s) chosen, process’ parameters have been optimized to make industrial transfer easier, and lower its overall cost. The developments achieved during this PhD led to two qualified mixtures, and optimized mixing, molding, debinding and sintering steps
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Tuppen, S. J. "Resistance bonding of titanium based aerospace alloys." Thesis, Swansea University, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.639270.
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The current research was commissioned to assess the feasibility of fabricating bonds between a range of commercially available titanium based aerospace alloys, using a low-cost direct resistance heating technique. A novel methodology has been devised and implemented which utilises a Gleeble facility to produce controlled resistance bonds. The optimisation of bonding parameters required to produce high quality joints is discussed i.e. the effects of surface treatment, pressure, time, temperature and environment. Optimised bond conditions have been defined for joining Ti 6/4 to itself and TNB (gamma titanium aluminide) to itself, negating the requirement for specialised surface treatments. In addition, a collaborative venture with Birmingham University was established to incorporate novel surface treatments using an electrical discharge machining procedure. In this respect, Ti 6/4 and TNB bonding couples utilising integral copper recast surface braze layers have been suitably optimised. Finally, the bonding of the dissimilar alloy combination Ti 6/4 to Ni-Ti (shape memory alloy) has been attempted using butt welding (with and without a Cu-Ni interlayer) and eutectic bonding procedures. However, bonding of this material combination proved difficult and this specific pairing may be incompatible using the present technique. Metallographic sections, chemical composition and micro-hardness traverses across all bond lines are presented as evidence of the form and integrity of the resulting joints. The mechanical performance of the bonds was assessed under monotonic tensile loading conditions.
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Basterretxea-Gomez, A. "Development of improved α + β titanium aerospace alloys." Thesis, Swansea University, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.636052.
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The design of titanium alloys has been traditionally conditioned by the development of relatively “randomly textured” materials rendering isotropic mechanical properties. The present project aims to gain a deeper insight into this area. In particular, the influence that processing variables such as (1) the Rolling Temperature, (2) The Rolling Direction, (3) The Reduction Percentage and (4) Heat Treatments have on the microstructure/texture development and related mechanical properties is given special attention. Mechanical properties analysed in the present project include fatigue crack threshold and crack propagation testing, strain control low cycle fatigue testing, load control low cycle fatigue testing and load control high cycle fatigue testing. An increase of rolling percentage favours recrystallisation of the alpha phase and aligning of textures towards the transverse direction (TD). Heat treated plates show similar texture orientations to those obtained for the un-heat-treated material, with a slight decrease in texture intensities. Material rolled uni-directionally above the beta transus shows strong basal-like texture. As the material is further rolled, now below the beta transus, textures start to become aligned towards the TD. Texture intensities drop substantially in the process. Samples tested at 90 degrees with respect to the rolling direction (RD) show higher threshold values than those tested at 0 degrees. The overall best crack initiation performance is associated to microstructures characterised by elongated alpha grains embedded in an intergranular beta phase. Equiaxed microstructures show poorer crack initiation performance. Samples tested in Strain Control at 90 degrees show higher stabilised stress ranges and lower fatigue performance than those tested at 0 degrees. The highest Load Control figure lives are obtained for samples tested at 0 degrees.
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Hoffmann, Ilona. "MAGNESIUM-TITANIUM ALLOYS FOR BIOMEDICAL APPLICATIONS." UKnowledge, 2014. http://uknowledge.uky.edu/cme_etds/36.
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Magnesium has been identified as a promising biodegradable implant material because it does not cause systemic toxicity and can reduce stress shielding. However, it corrodes too quickly in the body. Titanium, which is already used ubiquitously for implants, was chosen as the alloying element because of its proven biocompatibility and corrosion resistance in physiological environments. Thus, alloying magnesium with titanium is expected to improve the corrosion resistance of magnesium.
Mg-Ti alloys with a titanium content ranging from 5 to 35 at.-% were successfully synthesized by mechanical alloying. Spark plasma sintering was identified as a processing route to consolidate the alloy powders made by ball-milling into bulk material without destroying the alloy structure. This is an important finding as this metastable Mg-Ti alloy can only be heated up to max. 200C° for a limited time without reaching the stable state of separated magnesium and titanium. The superior corrosion behavior of Mg80-Ti20 alloy in a simulated physiological environment was shown through hydrogen evolution tests, where the corrosion rate was drastically reduced compared to pure magnesium and electrochemical measurements revealed an increased potential and resistance compared to pure magnesium. Cytotoxicity tests on murine pre-osteoblastic cells in vitro confirmed that supernatants made from Mg-Ti alloy were no more cytotoxic than supernatants prepared with pure magnesium. Mg and Mg-Ti alloys can also be used to make novel polymer-metal composites, e.g., with poly(lactic-co-glycolic acid) (PLGA) to avoid the polymer’s detrimental pH drop during degradation and alter its degradation pattern.
Thus, Mg-Ti alloys can be fabricated and consolidated while achieving improved corrosion resistance and maintaining cytocompatibility. This work opens up the possibility of using Mg-Ti alloys for fracture fixation implants and other biomedical applications.
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Kim, Tae-wŏn. "Failure processes in the superplastic forming of aerospace alloys." Thesis, University of Oxford, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389112.
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Chapman, Tamara. "The effect of environment on fatigue mechanisms in aerospace titanium alloys." Thesis, Imperial College London, 2015. http://hdl.handle.net/10044/1/28997.
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Titanium alloys are widely used in the aerospace industry, owing largely to their high specific fatigue strength at temperatures approaching 550C. A highly adherent and repassivating oxide layer makes titanium alloys highly corrosion resistant in many environments; their presumed immunity to corrosion-enhanced fatigue in typical aerospace environments was another initial attraction. The inaccuracy of this assumption was first revealed in the 1960s. Later, numerous studies found titanium to be vulnerable to stress corrosion cracking, particularly in the presence of molten salts. This thesis concerns the fatigue behaviour of titanium alloys used for aeroengine gas turbine compressor discs, specifically Ti-6246 and IMI 834. This research originally arose from the unexpected premature cracking of a spinning rig test component, suffered by Rolls-Royce plc, with a mysterious blue spot at the fatigue crack origin. The same macroscopic appearance of the crack origin could also be found in some test specimens held within the company's specimen archives. Initial discussions led to a parallel investigation of (i) the blue spot origins and (ii) the rate of crack growth in subsurface, naturally initiated cracks. Chemical characterisation of the blue spot origin was undertaken using focussed ion beam-secondary ion mass spectrometry and scanning-transmission electron microscopy based energy dispersive X-ray analysis as the principle techniques. The blue spot cracking phenomenon is found to be due to a hot salt stress corrosion cracking mechanism. Evidence from chemical analysis on the fracture surface and adjacent specimen surface suggests that in the presence of moisture, stress and elevated temperatures, NaCl deposits react with and disrupt the protective titanium oxide scale, producing byproducts of sodium titanate and HCl(g). In subsequent reactions the HCl attacks the newly exposed bare titanium metal, forming volatile titanium chlorides and atomic hydrogen, as well as a regenerating cycle of gaseous HCl. The resulting hydrogen segregating to the crack tip causes the crack to advance in a brittle manner, until the finite supply of corrodant is exhausted leading to a transition back to conventional low cycle fatigue. Importantly, it is inferred that because HSSCC requires both low pressures (so the alloy chlorides are volatile) and high temperatures, this is a mechanism that will operate in spin rig tests and under laboratory conditions, but not in compressors during flights where the localised air pressure is much higher. Post-mortem examination of electron transparent specimens lifted directly from the fracture surface enabled comparisons of the dislocation morphology and density beneath a hydrogen assisted origin (blue spot), low cycle fatigue origin and low cycle fatigue propagation region. A distinct change in dislocation mechanism is observed in the presence of hydrogen, where a lower dislocation density is observed compared to the LCF origin and propagation region. The results are consistent with the hydrogen enhanced localised plasticity (HELP) mechanism, and reference is also made to the competing theories of hydrogen enhanced decohesion (HEDE) and adsorption induced dislocation emission (AIDE). X-ray microtomography was used to monitor the growth of naturally initiated surface and subsurface fatigue cracks in air and vacuum environments at elevated temperatures. Surprisingly, this appears to be the first time that naturally initiated subsurface fatigue cracks have been examined using synchrotron X-ray microtomography. It is found that subsurface cracks grow more slowly than surface breaking cracks, even in vacuum, whilst air-exposed cracks grow fastest of all. In all three cases, cracking initiates at the primary alpha grains. The topic is of interest, as while it has long been known that cracks grow more slowly in laboratory vacuum than in air, the vacuum found in a subsurface crack would be much better, and potentially so good that hydrogen could be desorbed from the matrix material.
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Mavros, Nicholas C. "Advanced Manufacturing of Titanium Alloys for Biomedical Applications." Cleveland State University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=csu1527771497260907.
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Keralavarma, Shyam Mohan. "A micromechanics based ductile damage model for anisotropic titanium alloys." [College Station, Tex. : Texas A&M University, 2008. http://hdl.handle.net/1969.1/ETD-TAMU-2620.
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Lee, Wing-cheung, and 李永祥. "Functional coatings on Ti-6A1-4V and NiTi shape memory alloy for medical applications." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2011. http://hub.hku.hk/bib/B4715052X.
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Due to its excellent biocompatibility and mechanical properties, Ti-6Al-4V alloy has been extensively used in the medical field, especially as a material for hard tissue replacement. Owing to the unique shape memory and superelastic properties, NiTi shape memory alloy (SMA, with 50.8 at.% of Ni) has been investigated for load-bearing applications in orthopedics and dentistry. Since the longevity of current metal implants is approximately 10 to 15 years, many patients need to have revision surgeries in their lifetime. Therefore, there is great interest in the long-term stability, biocompatibility, bioactivity and other properties of Ti-6Al-4V and NiTi SMA implants. Implant-associated infections also pose serious threat to the success of metal implants. The goal of this project was to investigate several low-temperature surface modification techniques, including anodization and electrochemical deposition, and formulate coatings for potential clinical applications. Accordingly, several types of coatings were synthesized on Ti-6Al-4V and NiTi SMA substrates. Various aspects of the coatings, such as morphology, chemical composition, crystallinity, phase and bioactivity, were analyzed.
Firstly, a systematic study on the formation of titania nanotubes on Ti-6Al-4V by anodization was performed. Anodizing voltage and time were varied for comparisons. A dense and compact titania nanotube layer was synthesized on Ti-6Al-4V by anodizing at 25 V for 20 min. The titania nanotubes formed were rutile. After annealing at 500oC for 1 h, the titania nanotubes became anatase. The anatase phase exhibited better wettability than the rutile phase.
Secondly, dense and compact apatite coatings were formed on NiTi SMA samples through electrochemical deposition using mainly double-strength simulated body fluid (2SBF) as the electrolyte. The deposition conditions were varied and apatite coating characteristics studied. With the inclusion of collagen molecules (0.1 mg/ml) in the electrolyte (2SBFC), apatite/collagen composite coatings were fabricated. Collagen fibrils were not only observed on the surface of composite coatings but also were embedded inside in the coatings and at the coating-substrate interface. Results obtained from transmission electron microscopic and X-ray diffraction analyses showed that the apatite crystals in apatite coatings and apatite/collagen composite coatings were calcium-deficient carbonated hydroxyapatite. Apatite/collagen composite coatings exhibited excellent hydrophilicity, whereas apatite coatings displayed hydrophobic surfaces.
Finally, gentamicin-loaded, tobramycin-loaded, and vancomycin-loaded apatite coatings and apatite/collagen composite coatings were synthesized on NiTi SMA samples through electrochemical deposition using different drug concentrations in the electrolytes. A comparative study of apatite coatings and apatite/collagen composite coatings as drug delivery vehicles were conducted. Different aspects of antibiotic-loaded coatings (surface characteristics, chemical composition, wettability, etc.) and in vitro release behaviour were investigated. The antibiotics were physically embedded in coatings during coating formation. Upon sample soaking in phosphate-buffered saline (PBS), the release profiles established for antibiotic-loaded coatings demonstrated different levels of initial burst release and subsequent steady release characteristics. Apatite coatings and apatite/collagen coatings displayed preferential incorporation of specific antibiotics. For instance, apatite/collagen coatings showed better vancomycin incorporation than apatite coatings and the incorporation of vancomycin was better than tobramycin for apatite/collagen coatings. Apatite coatings demonstrated better tobramycin incorporation than apatite/collagen composite coatings.published_or_final_version
Mechanical Engineering
Master
Master of Philosophy
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Zuo, Yong Qiang. "Advanced titanium based laminates for high temperature applications." Thesis, University of Bristol, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389135.
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Turner, Mark W. "The Laser Cleaning of Aerospace Titanium Alloys for Electron Beam Welding and Diffusion Bonding." Thesis, University of Manchester, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.518438.
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Jerrard, Peter George Eveleigh. "Selective laser melting of advanced metal alloys for aerospace applications." Thesis, University of Exeter, 2011. http://hdl.handle.net/10036/3576.
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Research focused on the selective laser melting (SLM) of stainless steels and aluminium alloys. For steels, the possibility of creating a magnetically graded material was demonstrated as well as the ability to improve consolidation with austenitic and martensitic stainless steel powder mixtures. Stainless Steel/CoCr hybrid samples were also manufactured and tested to investigate the advantages of functionally graded materials (FGMs). Al alloy research began with examining the requirements for successful Al alloy consolidation in SLM and through experimentation it was found that Al alloys with good welding properties were the best choice: pure Al was found to be completely unsuitable. 6061 Al alloy was then used as a base material to manufacture Al-Cu alloy samples. Single layer SLM samples were produced first, which resulted in recognised Al-Cu microstructures forming. Multilayer Al alloy SLM research resulted in the discovery of the theorised ability to manufacture Al-Cu alloy parts with a nanocrystalline Al matrix with dispersed Al2Cu quasicrystals, resulting in a material comparable to a metal matrix composite that showed excellent corrosion resistance and compressive strength. Finally, a demonstration part was made to test the capability of the SLM process producing an aerospace type geometry using a customised Al alloy. Observations during manufacture and post process analysis showed that Al alloys were susceptible to changes in mechanical properties due to the geometry of the manufactured part.
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Zhang, Yue. "Corrosion of titanium, zirconium and their alloys for biomedical applications." Thesis, University of Birmingham, 2018. http://etheses.bham.ac.uk//id/eprint/8033/.
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in vivo degradation of Ti implants has remained as a concern despite its perceived excellent corrosion resistance. Elevated levels of metal have been detected both locally and systemically, often leading to unfavourable biological responses. Corrosion of Ti, Zr and their alloys (Ti6Al4V and TiZr) were studied in simulated physiological solutions. It was found that albumin, the most prevalent tissue fluid protein, induced a time dependent dissolution of Ti6Al4V in the presence of H2O2, an inflammatory biomolecule commonly found in peri implant sites, in 0.9% NaCl. However, the corrosion of Zr was observed to be unaffected by the presence of H2O2 and/or albumin in 0.9% NaCl. Furthermore, TiZr alloys have been shown to possess enhanced passivity in comparison to CP Ti in the various exposure conditions including highly acidic (HCl), oxidative environments (H2O2 in 0.9% NaCl) and cell cultures (macrophage). Corrosion products of Zr were characterised in situ by synchrotron X ray methods, which were found to be ZrOCl2 ∙ 8H2O, tetragonal ZrO2, and Zr metal fragments in 0.9% NaCl regardless of the presence or absence of H2O2 and/or albumin. The presence of Zr metal fragments as a result of a corrosion process indicates the generation of metal species in the absence of wear.
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Blackburn, Jonathan. "Understanding porosity formation and prevention when welding titanium alloys with 1μm wavelength laser beams." Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/understanding-porosity-formation-and-prevention-when-welding-titanium-alloys-with-1-micro-metre-wavelength-laser-beams(d8708b46-50ac-42f1-8f5e-a26ebdfc8ae6).html.
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Keyhole laser welding is a joining technology characterised by the high focussed power density applied to the workpiece, facilitating deep penetration at high processing speeds. High aspect-ratio welds produced using this process invariably have narrow heat-affected-zones and minimal thermal distortion compared with traditional arc welding processes. Furthermore, the ability to process out of vacuum and the easy robotic manipulation of fibre optically delivered 1μm wavelength laser beams, allow keyhole laser welding to process geometrically complex components. The widespread uptake of keyhole laser welding for the production of titanium alloy components in the aerospace industry has been limited by the stringent weld quality requirements. Producing welds with levels of subsurface weld metal porosity content meeting the required weld quality criteria has been the primary obstacle. Here, three techniques for controlling the levels of weld metal porosity when welding titanium alloys with Nd:YAG rod lasers have been developed. Characterisation of the welding processes using high speed photography and optical spectroscopy, have allowed an original scientific understanding of the effects these methods have on the keyhole, melt pool and vapour plume behaviour. Combining this with a thorough assessment of the weld qualities produced, has enabled the effects of these process behaviours on the formation of weld metal porosity to be determined. It was found that with the correct process parameters a directed gas jet and a dual focus laser welding condition can both be used to reduce the occurrence of keyhole collapse during Nd:YAG laser welding. The directed gas jet prevents the formation of a beam attenuating vapour plume and interacts with the molten metal to produce a stable welding condition, whereas the dual focus laser welding condition reduces fluctuations in the process due to an enlarged keyhole. When applied, both techniques reduced the occurrence of porosity in the weld metal of full penetration butt welds produced in titanium alloys. A modulated Nd:YAG laser output, with the correct waveform and modulation frequency, also reduced the occurrence of porosity in the weld metal compared with welds produced with a continuous-wave output. This was a result of an oscillating wave being set-up in the melt pool which manipulated the keyhole geometry and prevented instabilities in the process being established. In addition, the potential for welding titanium alloys to the required weld quality criteria with state-of-the-art Yb-fibre lasers has been assessed. It was found that the high power densities of suitably focussed laser beams with excellent beam quality, were capable of producing low-porosity full penetration butt welds in titanium alloys without the techniques required for laser beams with a lower beam quality. These new techniques for keyhole laser welding of titanium alloys will encourage the uptake of keyhole laser welding for producing near-net-shape high-performance aerospace components. The advantages offered by this joining technology include high productivity, low heat input and easy robotic automation.
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Sun, Tao, and 孙韬. "Surface modification of titanium metal for medical applications." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2010. http://hub.hku.hk/bib/B45457694.
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Cherukuri, Balakrishna. "Microstructural Stability and Thermomechanical Processing of Boron Modified Beta Titanium Alloys." Wright State University / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=wright1229656783.
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Chan, Yee-loi. "Surface modification of NiTi for long term orthopedic applications." Click to view the E-thesis via HKUTO, 2007. http://sunzi.lib.hku.hk/HKUTO/record/B39557406.
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Vicente, Nerio. "Spark Plasma Sintering of Titanium and Cobalt Alloys For Biomedical Applications." Doctoral thesis, Università degli studi di Trento, 2012. https://hdl.handle.net/11572/369162.
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This work was carried out in the frame of an industrial research project in cooperation with the Eurocoating SpA and K4Sint Srl, aiming at developing the commercial pure titanium, the Ti-6Al-4V and the Co-28Cr-6Mo alloys by Spark Plasma Sintering (SPS) for biomedical application. The definition of the process parameters for the production of a highly porous (cp-Ti), full density materials (Ti-6Al-4V and Co-28Cr-6Mo), and their combination in a surface functionalized full density substrate was the central focus. The SPS parameters were optimized to obtain the Co-28Cr-6Mo alloy in full density state for matching the international standards. Tensile and fatigue were the main properties under investigation. In the case of Ti-6Al-4V alloy the best SPS parameters was defined in a previous work by means of densification curve and tensile properties. Therefore, the fatigue resistance was the main property under investigation. The optimization of the sintering parameters was evaluated by the interdependence between the density, microstructure and hardness. Co-sintering of the cp-Ti with the Co alloy and the cp-Ti with the Ti alloy was carried in order to obtain a porous coated full density substrate in one single step. The SPS parameters were optimized in order to achieve a coating like structure containing macropores with specific range of size and highly interconnected. To that, the space holder technique was chosen since it allows a very good control of the pores characteristics. The interactions at the interfaces were characterized and the best SPS strategy was defined. Subsequently, fatigue tests were carried out in order to assess the influence of the porous coating on the fatigue resistance of the full density substrates. As a general conclusion it may be assessed that the process parameters for the production of the investigated biomaterials have been defined and the microstructural characteristics, as well as mechanical, corrosion properties and wear resistance satisfy the requirements on the international standards. These results have been used to produce implants which are under test.
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Vicente, Nerio. "Spark Plasma Sintering of Titanium and Cobalt Alloys For Biomedical Applications." Doctoral thesis, University of Trento, 2012. http://eprints-phd.biblio.unitn.it/783/1/PhD_THESIS_-_N.Vicente_Jr_-_revised.pdf.
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This work was carried out in the frame of an industrial research project in cooperation with the Eurocoating SpA and K4Sint Srl, aiming at developing the commercial pure titanium, the Ti-6Al-4V and the Co-28Cr-6Mo alloys by Spark Plasma Sintering (SPS) for biomedical application. The definition of the process parameters for the production of a highly porous (cp-Ti), full density materials (Ti-6Al-4V and Co-28Cr-6Mo), and their combination in a surface functionalized full density substrate was the central focus. The SPS parameters were optimized to obtain the Co-28Cr-6Mo alloy in full density state for matching the international standards. Tensile and fatigue were the main properties under investigation. In the case of Ti-6Al-4V alloy the best SPS parameters was defined in a previous work by means of densification curve and tensile properties. Therefore, the fatigue resistance was the main property under investigation. The optimization of the sintering parameters was evaluated by the interdependence between the density, microstructure and hardness. Co-sintering of the cp-Ti with the Co alloy and the cp-Ti with the Ti alloy was carried in order to obtain a porous coated full density substrate in one single step. The SPS parameters were optimized in order to achieve a coating like structure containing macropores with specific range of size and highly interconnected. To that, the space holder technique was chosen since it allows a very good control of the pores characteristics. The interactions at the interfaces were characterized and the best SPS strategy was defined. Subsequently, fatigue tests were carried out in order to assess the influence of the porous coating on the fatigue resistance of the full density substrates. As a general conclusion it may be assessed that the process parameters for the production of the investigated biomaterials have been defined and the microstructural characteristics, as well as mechanical, corrosion properties and wear resistance satisfy the requirements on the international standards. These results have been used to produce implants which are under test.
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McCarty, David Hughes Mary Leigh. "Durability of nitinol for structural applications." Auburn, Ala., 2006. http://repo.lib.auburn.edu/2006%20Summer/Theses/MCCARTY_DAVID_39.pdf.
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Khan, Maqsood Ahmad. "Titanium alloys : in-vitro corrosion and wear within varying biological environments." Thesis, University of Liverpool, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266093.
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Dixit, Vikas. "Grain-Boundary Parameters Controlled Allotriomorphic Phase Transformations in Beta-Processed Titanium Alloys." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1357240292.
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KRAMER, KEVIN ALBERT. "FEASIBILITY STUDY OF THERMAL-ELASTOGRAPHIC DETECTION OF NON-VOIDED HARD-ALPHA INCLUSIONS IN TITANIUM ALLOYS." University of Cincinnati / OhioLINK, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1100552079.
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Chan, Yee-loi, and 陳以來. "Surface modification of NiTi for long term orthopedic applications." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2007. http://hub.hku.hk/bib/B39557406.
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Farinha, Marques Vitor Manuel. "Lead free solders for aerospace applications." Thesis, University of Oxford, 2010. http://ora.ox.ac.uk/objects/uuid:85707054-bc46-44f3-b9c6-9fd29358ad25.
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The factors controlling the reliability of Pb-free solders when subject to thermomechanical regimes relevant to the harsh aerospace environment have been studied. Ball grid array (BGAs) typical of microelectronic devices have been manufactured in-house and subjected to isothermal ageing and thermal cycling. The BGAs comprised both Cu and Ni-Au metallizations, Pb-free Sn-Ag-Cu 400 and 600μm solder balls, FR4 and Al2O3 boards, and included circuits to measure resistance changes due to damage in the joints during thermal cycling. Microstructural evolution within the solders balls and complex interfacial reactions were studied in all configurations using various types of electron microscopy. The mechanical properties of the different phases formed within solder joints were studied using nanoindentation at room and elevated temperatures up to 175°C for the first time. Intermetallic compounds (IMCs) were stiff, hard and brittle with very low creep rates, while the softer primary Sn, eutectic regions and Cu metallization readily underwent creep. Two-dimensional finite element analysis (FEA) of nanoindentation was used to understand better the physical meaning of nanoindentation creep data. Reliability experiments comprised both thermal cycling and FEA of BGAs. The difference in coefficient of thermal expansion (CTE) in the BGA materials caused interfacial fatigue damage in the solder joints, which was detected primarily at the solder/metallization interface of the outermost, most strained solder joint. Accumulated creep strain per cycle at this interface was evaluated using 3D FEA of the stress-strain state of the BGA and results calibrated against experimental BGA mean lifetimes using the Coffin-Mason relationship. Nanoindentation combined with FEA has been shown to be a viable route for the rapid assessment of creep performance and lifetime in lead-free solders under aerospace thermal cycles.
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McGillicuddy, K. "Evaluation of the GTA and plasma welding process applied to Ti-6Al-4V for aerospace applications." Thesis, Cranfield University, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.250495.
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Khasawneh, Firas Abdallah. "Characterization of drillability of sandwich structure of carbon fiber reinforced epoxy composite over titanium alloy." Diss., Columbia, Mo. : University of Missouri-Columbia, 2006. http://hdl.handle.net/10355/5871.
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Thesis (M.S.)--University of Missouri-Columbia, 2006.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on September 13, 2007). Vita. Includes bibliographical references.
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Goodwin, Paul S. "Microstructures and properties of rapidly solidified Al-Cr-Fe alloys for aerospace applications." Thesis, University of Surrey, 1992. http://epubs.surrey.ac.uk/842855/.
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The development of aluminium alloys capable of elevated temperature service by utilization of Rapid Solidification (RS) processing techniques has been an area of intense study during the past decade. The ternary alloy system, Al-Cr-Fe, has displayed very promising mechanical properties when produced by an evaporation-vapour deposition technique, but little indication exists of whether similar properties may be achievable by using other, more commercially applicable, RS techniques. This work comprises a study of the microstructure and tensile properties of a range of Al-Cr-Fe alloys (Al-2.93 to 8.43 wt% Cr-0.67 to 2.07 wt% Fe) processed by high pressure gas atomisation (HPGA), supplemented by additional experiments using melt-spinning and chill-casting techniques in order to allow the effects of a wide range of cooling rates (< 1k/s to 106K/s) to be examined. A series of binary Al-Cr alloys (Al-1.99 to 5.50 wt% Cr) were also processed in order to facilitate comparison with the ternary alloys. The variety of microstructures observed in the atomised powders were consistent with the different cooling rates and nucleation temperatures experienced by droplets of different diameters. The cooling rate necessary to suppress formation of the Ali3Cr2 phase was found to be consistently higher in the ternary alloys than in the corresponding binaries. No evidence was found of partitionless solidification having occurred in the Al-Cr-Fe powders, the estimated solidification front velocities being insufficient to prevent the partitioning of the iron to the infinity-aluminimum cell boundaries. The infinity-aluminium phase was found to be divided into two co-existing, but distinct, solid solutions with different chromium solute levels. A fine spherical phase was observed in the finest particles of the most concentrated alloy (Al-8.43 wt% Cr-1.26 wt % Fe), which was found to be similar to the icosahedral phase identified in the melt-spun ribbon. A relationship has been determined between the thickness of wedge shaped chill castings and powder particle diameters for similar microstructural transitions. A procedure is proposed by which the determination of alloy compositions designed to give a particular microstructure in a specific powder size fraction can be accomplished by a simple chill casting technique. The mechanical properties of the atomised powders consolidated by extrusion have been determined and related to the microstructures and strengthening mechanisms operative in the materials. A large contribution to the strength of the extruded materials is derived from their fine grain size. However, none of the atomised Al-Cr-Fe alloys matched the properties obtained in the Al-7.5 wt% Cr-1.2 wt% Fe alloy material produced by the vapour deposition technique. None of the alloys investigated retained its strength after prolonged thermal exposure at or above 350°C, nor possessed adequate tensile strength properties at 350°C. The results do suggest, however, that a service temperature of 300°C may be possible.
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Nnamchi, Paul Sunday Ugwu. "A novel approach to property driven design of titanium alloys for biomedical applications." Thesis, University of Sheffield, 2014. http://etheses.whiterose.ac.uk/6212/.
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Almushref, Fares R. "Design and manufacture of engineered titanium-based materials for biomedical applications." Thesis, Loughborough University, 2017. https://dspace.lboro.ac.uk/2134/25517.
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Metallic materials have gained much attention recently from the areas of medical devices and orthopaedics. Artificial organs, dental implants, prostheses and implants that replace damaged or malfunctioning parts in the body are, or contain, metal components. Our ageing society poses an increased demand to provide devices and implants that can demonstrate better performance than those presented by traditional solutions. Matching the mechanical properties (i.e. stiffness and strength) of the device to those of the host tissue is a major challenge for the design and manufacture of engineered metal materials for biomedical applications. Failure in doing so provokes implant loosening, patient discomfort and repeated surgeries. Therefore, tailoring physical properties and biocompatibility of those materials is the main final aim of this research programme. This PhD study has focused on the tailoring of the mechanical properties of titanium-based materials and titanium-based alloys. Titanium inertness and the selection of biocompatible alloying elements were set as the baseline. Two approaches were employed to decrease stiffness (i.e. Young s modulus): one, by introducing porosity in a titanium matrix and therefore, reduce its Young s modulus, and two, by designing and manufacturing beta-titanium-based alloys with a reduced Young s modulus. Titanium scaffolds were manufactured using powder metallurgy with space holder technique and a sintering process. Different space holder sizes were used in four different categories to study the effect of pore size and porosity on the mechanical properties of the porosity engineered Ti scaffolds. Ti-based alloys were manufactured using manufacturing techniques such as sintering and arc-melting. The effect of different fabrication processes and the addition of beta-stabilising elements were studied and investigated. The obtained results of mechanical properties for pore size and porosity were within the values that match bone properties. This means these materials are suitable for biomedical application and the beta-Ti alloys results show that the mechanical properties can be decreased via tailoring the crystal structures. The characterisation of the Ti-based alloys helps to develop this material for its use in biomedical application.
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Tinl, Nicholas E. "An Investigation of the Bearing Strength of Bolted Connections in Aluminum and Titanium Alloys." University of Akron / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=akron1322506214.
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Weeks, Carrell Elizabeth. "Evaluation of a Gamma Titanium Aluminide for Hypersonic Structural Applications." Thesis, Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/6955.
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Titanium matrix composites have been extensively evaluated for their potential to replace conventional superalloys in high temperature structural applications, with significant weight-savings while maintaining comparable mechanical properties. The purpose of this investigation is the evaluation of a gamma titanium aluminide alloy with nominal composition Ti-46.5Al-4(Cr,Nb,Ta,B)at.% as a matrix material for use in intermediate temperature applications (400-800㩠in future aerospace transportation systems, as very light-weight structures are needed for cost and weight reduction goals.
Mechanical characterization testing was performed over the potential usable temperature range (21-800㩮 Thermal expansion behavior was evaluated, as thermal mismatch of the constituents is an expected problem in composites employing this matrix material. Monotonic testing was conducted on rolled sheet material samples to obtain material properties. The alloy exhibited good strength and stiffness retention at elevated temperatures, as well as improved toughness. Monotonic testing was also conducted on specimens exposed to elevated temperatures to determine the degradation effects of high temperature exposure and oxidation. The exposure did not significantly degrade the alloy properties at elevated temperatures; however, room temperature ductility decreased.
Analytical modeling using AGLPLY software was conducted to predict the residual stress state after composite consolidation as well as the potential mechanical behavior of [0]4 laminates with a 㭍ET matrix. Silicon carbide (Ultra-SCS) and alumina (Nextel 610) fibers were selected as potential reinforcing materials for the analysis. High residual stresses were predicted due to the thermal mismatch in the materials. Laminates with Nextel 610 fibers were found to offer the better potential for a composite in this comparison as they provide a better thermal match. Coupons of SCS-6/㭍ET were manufactured with different volume fractions (10% and 20%). Both manufacturing attempts resulted in transverse cracking in the matrix from the residual thermal stress.
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Zhao, Dapeng [Verfasser], and Florian [Akademischer Betreuer] Pyczak. "Metal Injection Moulding of Titanium-Niobium alloys for biomedical applications / Dapeng Zhao. Betreuer: Florian Pyczak." Cottbus : Universitätsbibliothek der BTU Cottbus, 2014. http://d-nb.info/1050099133/34.
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Clem, William Charles. "Mesenchymal stem cell interaction with nanonstructured biomaterials for orthopaedic applications." Birmingham, Ala. : University of Alabama at Birmingham, 2008. https://www.mhsl.uab.edu/dt/2009r/clem.pdf.
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Thesis (Ph. D.)--University of Alabama at Birmingham, 2008.Additional advisors: Yogesh K. Vohra, Xu Feng, Jack E. Lemons, Timothy M. Wick. Description based on contents viewed July 8, 2009; title from PDF t.p. Includes bibliographical references.
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BAUDANA, GIORGIO. "γ-Titanium Aluminide Alloys for Aircraft and Automotive Engine Components Applications Processed by Electron Beam Melting." Doctoral thesis, Politecnico di Torino, 2018. http://hdl.handle.net/11583/2699607.
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γ-TiAl alloys are a family of intermetallic compounds which, thanks to their excellent physical and mechanical properties, are arousing big interest in the aerospace and automotive industries. In particular, they are considered an attractive alternative to nickel-based superalloys due to a lower density (about 4 g/cm3 for γ-TiAl alloys and 8 g/cm3 for Ni-based superalloys) that makes their specific mechanical properties comparable to those of nickel-based superalloys. The low weight of these materials allows to reduce the overall weight of the aircraft engine component or automotive engine component. As a result, it is possible to enhance the components performances and reduce fuel consumption and emissions. The low weight of γ-TiAl alloys, it will also contribute to achieve the targets for fuel-burn and emission reduction proposed by the European Commission and NASA.
The most applied conventional industrial scale processing routes for titanium aluminides include ingot casting, ingot forging, hot-rolling sheet production, investment and permanent mold casting and powder metallurgy processing. The processing of titanium aluminide via these conventional manufacturing methods can be complex due to the low ductility and fracture toughness of the material and casting process is an expensive solution and presents several problems such as the reactivity of the molten material with ceramics. The Electron Beam Melting (EBM) additive manufacturing technology is well known and considered for the processing of TiAl alloys, in particular for the aerospace application. This additive manufacturing technology uses an electron beam to generate parts by selectively melting the powder layer by layer according to CAD data. EBM technology allows to produce lighter and complex-shape components with a minimum material and energy waste.
The goal of this thesis was to investigate and characterize both γ-TiAl specimens and components produced by EBM and the heat treatments set-up in order to optimize the material properties. Since the starting material for the EBM process is the pre-alloyed powder, the characterization and the optimization of the powders was a fundamental preliminary step in order to guarantee a successful production of the final parts.
The experimental activities are related to four different TiAl alloys, three of which for aircraft engine application that are the 48-2-2 alloy (Ti-48Al-2Cr-2Nb (at.%)), the High-Niobium alloy (Ti-(45-47)Al-2Cr-8Nb (at.%)) and the TNM alloy (Ti-43.5Al-4Nb-1Mo-0.1B (at.%)) and one of automotive interest that is the so called RNT650 alloy (Ti-48Al-2Nb-0.7Cr-0.3Si (at.%)).
The TiAl 48-2-2 powder reuse investigation has demonstrated the possibility to reuse the powder up to six EBM cycles without a significant pick-up of contaminants, modification of particle size distribution, flowability and apparent density during the subsequent EBM jobs. This achievement means that, by reusing the powders for several cycles it is possible to obtain a considerable advantage in terms of cost and material saving. However, it is important to specify, that it is possible to mix the recycled powder with new powder between different cycles in order to maintain the proper powder characteristics.
The effect of the EBM processes parameters on the TiAl 48-2-2 material properties has been investigated by varying certain building parameters according to a Design Of Experiment (DOE) matrix. The study has shown that i) there is a parameters combination window in which the amount of process defects in the built material is very limited, ii) inside this window it is possible to perform a further fine parameters tuning in order to obtain an homogeneous microstructure and limit the evaporation of low-melting elements such as aluminum. In fact, this study has confirmed that the aluminum content and microstructure are very sensitive to the parameters variation.
Regarding the 3rd generation TNM alloy for aircraft engine application, it has been demonstrated the possibility to process it by EBM obtaining fully densified parts and, after a proper heat treatment, it has been possible to obtain the desired microstructures in order to improve the mechanical properties of the material according to the application.
The RNT650 alloy for the automotive application has been successfully processed by EBM and both massive specimens and lightweight hollow turbocharger wheels have been produced and characterized. Also in this case, a proper microstructure for the application has been obtained by means of a proper heat treatment. In addition, the characterization of a turbocharger wheel-shaft assembly prototype has been performed and it has shown a promising junction quality with a complete adhesion and without the presence of any defects at the interface.
Regarding the aircraft engine application of γ-TiAl, big part of the research activity was done in collaboration with AvioAero, within some European and Regional research projects. In particular, the 48-2-2 alloy as well as new generation alloys such as High Niobium alloy and TNM alloy produced by Electron Beam Melting were investigated in the frame of the European project E-BREAK.
Considering the automotive application, the part of the work on the RNT650 alloy was done within the European project TIALCHARGER.
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Corrado, Gaetano. "Design and optimization of a protection device for laser weld beads of metal alloys for aerospace applications." Doctoral thesis, Universita degli studi di Salerno, 2013. http://hdl.handle.net/10556/803.
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2011 - 2012In the present thesis an automated laser welding apparatus was designed and developed in order to perform laser , that allows to achieve laser welding in a controlled, versatile, efficient, reliable, simple, and economical way. This system allows to shield not controlled from oxidation and nitriding process, both the melted pool and the material portion just after welding when the oxidation or nitriding critical temperatures, generally between 200 °C and 500 °C are still in place. Oxidation is even more serious when welding titanium, nickel superalloy, zirconium, molybdenum, stainless steel and other gas-reactive metals and alloys. Most of these materials are used for a wide range of applications in aerospace and biomedical fields as well as for piping in petrochemical, food, semiconductor, nuclear, and chemical industries. These metals can be used in contact with corrosive or sensitive materials without contaminating them, thus making them the number one choices for applications requiring long service life and non-contamination. The resulting oxidized surfaces are not longer corrosion resistant and further treatment may be necessary. Removing the oxidation using mechanical means, such as grinding, also removes the metal’s passive protective layer. The automated laser welding apparatus (patent number: SA2012A000016) was tested with three different joints: butt welding of 3 mm thick Ti6Al4V plates; dissimilar butt welding of 1.5 mm thick of Haynes 188 and Inconel 718 and edge joint of 0.7 mm thick Inconel 625 sheets. All of the tests were performed with automated laser welding apparatus; the bead quality was discussed in terms of geometrical features, porosity content, microstructure, hardness and strength. This work is divided in three parts. In the first part, the principles of operation and the different types of laser are discussed, with mention to the advantages of a disk laser source, which is employed in the experimental part. Also, the types of laser welding, the influence of process parameters and the advantages compared to traditional welding techniques are explained. The second part presents the issue of oxidation caused by welding and the relative solutions proposed in the literature for shielding the bead. Then, the development and the implementation of the automated laser welding apparatus with its components is described. Finally, the capabilities of the automated laser welding apparatus on three different types of joint are discussed in the last part and the relative results are provided. [edited by author]
XI n.s.
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Golozar, Mehdi. "Plasma electrolytic oxide coatings on low-modulus [beta]-type titanium alloys : applications to load-bearing orthopaedic implants." Thesis, University of Cambridge, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.709079.
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Nguyen, QuynhGiao N. "High Temperature Volatility and Oxidation Measurements of Titanium and Silicon Containing Ceramic Materials." Abstract only. Full text release has been delayed at the author's request until December 31, 2010, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=csu1239291812.
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Thesis (Ph.D.)--Cleveland State University, 2008Abstract. Includes bibliographical references (p. 110-111). Electronic full text release has been delayed at the author's request until December 31, 2010.
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Martin, Alexander Charles. "Initial Weldability of High Entropy Alloys for High Temperature Applications." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1555496040477991.
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Gray, Alyn M. "An Initial Study of Binary and Ternary Ti-based Alloys Manufactured Using Laser Engineered Net Shaping (LENSTM)." Thesis, University of North Texas, 2015. https://digital.library.unt.edu/ark:/67531/metadc822823/.
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In this study an initial assessment of the composition – microstructure – property relationships in binary and ternary Ti – based systems are made possible using LENSTM technology. Laser Engineering Net Shaping (LENSTM), a rapid prototyping, directed laser deposition methodology of additive manufacturing (AM) was used to create bulk homogenous specimens that are compositionally graded. Compositionally graded specimens were made possible by incorporating elemental blends of powder during the LENSTM process. While there have been numerous studies assessing the influence of common elements (e.g., V, Mo, Al, and Cr) on the resulting microstructure in titanium alloys, other elements have been neglected. A systematic study of the Ti – Fe – Al ternary system based upon varying compositions of the eutectoid former, Fe with Al to stabilize the a and b phases respectively has also been neglected. This research effort focuses on exploiting the LENSTM process by rapidly assessing the composition – microstructure – property relationships in a combinatorial approach for the Ti – W, Ti – Fe, and Ti – Fe – Al systems. Compositionally graded specimens of Ti – xW (0
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Owusu-Danquah, Josiah Sam Owusu-Danquah. "MODELING AND CHARACTERIZATION OF A GENERAL MULTIMECHANISM MATERIAL MODEL FOR ADVANCED ENGINEERING APPLICATIONS OF SHAPE MEMORY ALLOYS." University of Akron / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=akron149936399244747.
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Thomas, Joshua Michael. "Simulating the mechanical response of titanium alloys through the crystal plasticity finite element analysis of image-based synthetic microstructures." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1325088641.
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Brice, David. "An Assessment of Uncommon Titanium Binary Systems: Ti-Zn, Ti-Cu, and Ti-Sb." Thesis, University of North Texas, 2015. https://digital.library.unt.edu/ark:/67531/metadc799482/.
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The current study focuses on phase stability and evolution in the titanium-zinc titanium-copper and titanium-antimony systems. The study utilized the Laser Engineering Net Shaping (LENS™) processing technique to deposit compositionally graded samples of three binary system in order to allow the assessment of phase stability and evolution as a function of composition and temperature the material is subjected to. Through LENS™ processing it was possible to create graded samples from Ti-xSb (up to 13wt%) and Ti-xCu (up to 16wt%). The LENS™ deposited gradient were solutionized, and step quenched to specific aging temperature, and the resulting microstructures and phase were characterized utilizing XRD, EDS, SEM, FIB and TEM. The Ti-Zn system proved incapable of being LENS™ deposited due to the low vaporization temperature of Zn; however, a novel processing approach was developed to drip liquid Zn onto Ti powder at temperatures above β transus temperature of Ti (882 ◦C) and below the vaporization temperature of Zn (907 ◦C). The product of this processing technique was characterized in a similar way as the graded LENS™ depositions. From measurements performed on Ti-Sb it seems that Sb could be a potential α stabilizer in Ti due to the presence of a mostly homogeneous α grains throughout the gradient; however, from XRD it can be understood that a titanium antimonide phase is present. From results obtained from the Ti-Zn samples, it can be surmised that the eutectoid reaction seems to be active, i.e. The eutectoid reaction is kinetically fast, as concluded by the presence of pearlitic structures. Finally, for the Ti-Cu system this work has been attempted to prove or disprove the existence of the Ti3Cu through the use of XRD and TEM SAD patterns. From XRD spectra collected there are peaks belonging to the Ti3Cu orthorhombic phase along with Ti2Cu and α-Ti phase. In addition to the Ti-Cu system displayed structures associated with divorced eutectoid decomposition mechanism, and at low undercooling seems to be prone to forming solid state dendrites.
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Nyamukamba, Pardon. "Preparation of photocatalytic TiO₂ nanoparticles immobilized on carbon nanofibres for water purification." Thesis, University of Fort Hare, 2011. http://hdl.handle.net/10353/367.
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Titanium dioxide nanoparticles were prepared using the sol-gel process. The effect of temperature and precursor concentration on particle size was investigated. The optimum conditions were then used to prepare carbon and nitrogen doped titanium dioxide (TiO2) nanoparticles. Doping was done to reduce band gap of the nanoparticles in order to utilize visible light in the photocatalytic degradation of organic compounds. A significant shift of the absorption edge to a longer wavelength (lower energy) from 420 nm to 456 nm and 420 nm to 428 nm was observed for the carbon doped and nitrogen doped TiO2 respectively. In this study, the prepared TiO2 photocatalyst was immobilized on carbon nanofibres to allow isolation and reuse of catalyst. The photocatalytic activity of the catalyst was tested using methyl orange as a model pollutant and was based on the decolourization of the dye as it was degraded. The doped TiO2 exhibited higher photocatalytic activity than the undoped TiO2. The materials prepared were characterized by XRD, TEM, SEM, FT-IR, DSC and TGA while the doped TiO2 was characterized by XPS, ESR and Raman Spectroscopy.
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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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Gerrard, Alexander James. "Inclusions and hydrogen and their effects on the quality of direct chill cast and flat rolled aluminium alloys for aerospace applications." Thesis, University of Birmingham, 2014. http://etheses.bham.ac.uk//id/eprint/5373/.
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Flat rolled Al alloys manufactured using the Direct Chill casting process are used in safety critical applications and therefore need to be of the highest possible quality. Liquid metal is cleaned using a mixture of inert Ar and reactive Cl gases before casting. The first section of this work explores the aetiology of defects in hot rolled Al plate, found using ultrasound. Inclusions extracted from 7xxx plate were examined using scanning electron microscopy. A second type of defect found in 7475 alloy plate was established to be a coarse grain structure. The second section aimed to provide a better understanding of the role of Cl on degassing. The effects of Cl on the degassing performance of a Spinning Nozzle Inert Floatation degassing unit were approached statistically using ALSCAN. Finally, 20 kg melts of Al and Al alloys were doped with H and subsequently degassed, and the reduction in H over time was measured using ALSPEKH. In the third section the LECO H determination device was used to degas Al specimens to very low levels. Degassed specimens were melted under air or N\(_2\) atmosphere, so that when cracks formed in the surface oxide layer either Al\(_2\)O\(_3\) or AlN formed. After subsequent exposure to pure H\(_2\) gas the specimens that formed AlN were found to have absorbed more H than those heated in air.
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Young, Avery W. "A Study on NiTiSn Low-Temperature Shape Memory Alloys and the Processing of NiTiHf High-Temperature Shape Memory Alloys." Thesis, University of North Texas, 2018. https://digital.library.unt.edu/ark:/67531/metadc1157642/.
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Shape memory alloys (SMAs) operating as solid-state actuators pose economic and environmental benefits to the aerospace industry due to their lightweight, compact design, which provides potential for reducing fuel emissions and overall operating cost in aeronautical equipment. Despite wide applicability, the implementation of SMA technology into aerospace-related actuator applications is hindered by harsh environmental conditions, which necessitate extremely high or low transformation temperatures. The versatility of the NiTi-based SMA system shows potential for meeting these demanding material constraints, since transformation temperatures in NiTi can be significantly raised or lowered with ternary alloying elements and/or Ni:Ti ratio adjustments. In this thesis, the expansive transformation capabilities of the NiTi-based SMA system are demonstrated with a low and high-temperature NiTi-based SMA; each encompassing different stages of the SMA development process. First, exploratory work on the NiTiSn SMA system is presented. The viability of NiTiSn alloys as low-temperature SMAs (LTSMAs) was investigated over the course of five alloy heats. The site preference of Sn in near-equiatomic NiTi was examined along with the effects of solution annealing, Ni:Ti ratio adjustments, and precipitation strengthening on the thermomechanical properties of NiTiSn LTSMAs. Second, the thermomechanical processability of NiTiHf high-temperature SMA (HTSMA) wires is presented. The evolution of various microstructural features (grain size reduction, oxide growth, and nano-precipitation) were observed at incremental stages of the hot rolling process and linked to the thermal and mechanical responses of respective HTSMA rods/wires. This work was carried out in an effort to optimize the rolling/drawing process for NiTiHf HTSMAs.
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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 biocompatibilitéThis 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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Antonysamy, Alphons Anandaraj. "Microstructure, texture and mechanical property evolution during additive manufacturing of Ti6Al4V alloy for aerospace applications." Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/microstructure-texture-and-mechanical-property-evolution-during-additive-manufacturing-of-ti6al4v-alloy-for-aerospace-applications(03c4d403-822a-4bfd-a0f8-ef49eb65e7a0).html.
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Additive Manufacturing (AM) is an innovative manufacturing process which offers near-net shape fabrication of complex components, directly from CAD models, without dies or substantial machining, resulting in a reduction in lead-time, waste, and cost. For example, the buy-to-fly ratio for a titanium component machined from forged billet is typically 10-20:1 compared to 5-7:1 when manufactured by AM. However, the production rates for most AM processes are relatively slow and AM is consequently largely of interest to the aerospace, automotive and biomedical industries. In addition, the solidification conditions in AM with the Ti alloy commonly lead to undesirable coarse columnar primary β grain structures in components. The present research is focused on developing a fundamental understanding of the influence of the processing conditions on microstructure and texture evolution and their resulting effect on the mechanical properties during additive manufacturing with a Ti6Al4V alloy, using three different techniques, namely; 1) Selective laser melting (SLM) process, 2) Electron beam selective melting (EBSM) process and, 3) Wire arc additive manufacturing (WAAM) process. The most important finding in this work was that all the AM processes produced columnar β-grain structures which grow by epitaxial re-growth up through each melted layer. By thermal modelling using TS4D (Thermal Simulation in 4 Dimensions), it has been shown that the melt pool size increased and the cooling rate decreased from SLM to EBSM and to the WAAM process. The prior β grain size also increased with melt pool size from a finer size in the SLM to a moderate size in EBSM and to huge grains in WAAM that can be seen by eye. However, despite the large difference in power density between the processes, they all had similar G/R (thermal gradient/growth rate) ratios, which were predicted to lie in the columnar growth region in the solidification diagram. The EBSM process showed a pronounced local heterogeneity in the microstructure in local transition areas, when there was a change in geometry; for e.g. change in wall thickness, thin to thick capping section, cross-over’s, V-transitions, etc. By reconstruction of the high temperature β microstructure, it has been shown that all the AM platforms showed primary columnar β grains with a <001>β.