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1
Hanna, Ivil. "Mechanical Properties of Niobium Alloyed Gray Iron". Thesis, KTH, Fordonsdynamik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-39691.
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The influence of adding an amount of 0.1% and 0.3% niobium to the gray iron alloy used for brake discs, these disc materials are called disc 16 respective 17, have been investigated at RT (room temperature). That is together with two other alloys, the reference disc which contains 0.32% molybdenum but lacks niobium and another one with neither niobium nor molybdenum in it, this is called disc material 15. Focus in this thesis work is on the mechanical properties of the studied materials and for this purpose the low cycle fatigue (LCF) properties of the mentioned alloys are investigated. The strain controlled LCF were done at strain amplitudes varying from 0.05 to 0.43%. According to the results, all the materials become survivors when the applied strain was 0.05%. For the other applied strain ranges the reference disc material shows the shortest life-span, while it is difficult to distinguish the other three materials. However, on average material 16 and 17 show a slightly better performance compared to material 15. This means that niobium can be used to replace molybdenum in this application. However, an obvious difference between disc material 16 and 17 cannot be observed when material disc 16 showed to be the superior at some applied strains and material disc 17 at the others. For this reason, it is more profitable to replace the 0.32% molybdenum with 0.1% niobium. The results also show that if the loading is mainly in the elastic region the life increases dramatically. It is also obvious that the static properties of gray iron increases with increasing niobium content and the fracture stress increases with about 30 MPa when the niobium contents go from 0.1% to 0.3%.
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COELHO, RODRIGO E. "Obtencao das ligas Al-Fe-X-Si (X = V ou Nb) por moagem de alta energia e extrusao a quente". reponame:Repositório Institucional do IPEN, 2001. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10870.
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Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
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DUVAIZEM, JOSE H. "Estudo das propriedades mecanicas e microestruturais de ligas a base de titanio-niobio-zirconio processados com hidrogenio e metalurgia do po para utilizacao em implantes dentarios". reponame:Repositório Institucional do IPEN, 2009. http://repositorio.ipen.br:8080/xmlui/handle/123456789/9429.
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Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Hailer, Benjamin Thomas. "Effect of Heat Treatment on Magnetic and Mechanical Properties of an Iron-Cobalt-Vanadium-Niobium Alloy". Thesis, Virginia Tech, 2001. http://hdl.handle.net/10919/32135.
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Iron-cobalt-vanadium alloys can be processed to have excellent soft magnetic properties for use in high performance power generation applications such as the rotors and stators of aircraft integrated power units. These soft magnetic properties are, however, developed at the expense of mechanical strength and toughness. Small additions of niobium are reported to increase the strength of these Fe-Co-V alloys. This study evaluates the effects of heat treatment on the mechanical and magnetic properties of heavily cold work strip of a 48 wt.% iron-48 wt.% cobalt-2 wt.% vanadium alloy with a 0.3 wt.% addition of niobium.
For heat treatments between 640 and 740°C for 1 hour the tensile and yield strengths and ductility of the alloy were all found to be superior to a similar alloy found in the literature without the addition of Nb and processed in a similar manner. Magnetic permeability, remnant induction, saturation induction, coercivity and core loss were only slightly degraded at all annealing temperatures when compared with the non-niobium containing alloy. All properties were shown to depend primarily on degree of recrystallization of the sample, which was found to fully recrystallize between 720 and 740 °C for 1 hour anneals. No significant change in measured properties were found when annealing time was increased to 2 hours. Full recrystallization was observed for samples annealed for as short of times as 10 minutes at 800 °C.Master of Science
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DUVAIZEM, JOSE H. "Obtenção de ligas à base de titânio-nióbio-zircônio processados com hidrogênio e metalurgia do pó para utilização como biomateriais". reponame:Repositório Institucional do IPEN, 2013. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10604.
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Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Talbot, Diane. "The effects of plate processing parameters on the microstructure, mechanical properties and precipitation characteristics of niobium-containing high strength low alloy steels". Thesis, University of Birmingham, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.251877.
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Pounder, Neill Malcolm. "The electrical transport properties of niobium-silicon amorphous alloys". Thesis, University of Leeds, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.305616.
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Stasiak, Tomasz. "High Entropy Alloys with improved mechanical properties". Thesis, Lille 1, 2020. http://www.theses.fr/2020LIL1R050.
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Les Alliages à Haute Entropie (AHEs ou HEAs en anglais) sont un nouveau type d'alliages multi-élémentaires. Ils contiennent au moins cinq éléments de teneur comprise entre 5 et 35 at %. L'entropie de configuration élevée, qui est une raison du nom de cette famille d'alliages, ainsi que d'autres paramètres, tels que l'enthalpie de mélange, la différence de taille atomique, la différence d'électronégativité ou la concentration d'électrons de valence, stabilisent une solution solide plutôt que des composés intermétalliques. L'attention de la communauté scientifique a été attirée par les propriétés prometteuses et les microstructures intéressantes des HEAs.Dans ce travail, une nouvelle famille de HEAs Al-Cr-Fe-Mn-Mo a été étudiée. Les analyses microstructurales et chimiques ont été menées par DRX, spectrométrie Mössbauer, MEB, MET, EDX, EBSD. Dans un premier temps, des calculs basés sur une approche paramétrique ont été réalisés pour optimiser la composition chimique. Les compositions sélectionnées ont été préparées par mécanosynthèse dans différents types broyeurs. Les conditions optimisées garantissant une homogénéité chimique maximale de la poudre et une faible contamination par les matériaux des billes et des jarres ont été déterminées. Deux phases cubique centrée (cc) se forment pendant la mécanosynthèse avec les paramètres de maille 3,13 Å (cc#1) et 2,93 Å (cc#2). Le traitement thermique de la poudre entraîne plusieurs transformations de phase (la formation de la phase χ). Le recuit à 950 °C/1 h favorise l'augmentation de la fraction volumique de la phase cc#2, tandis que les cc#1 et χ disparaissent. Néanmoins, de petites fractions de carbures et d'oxydes ont été trouvées.Les échantillons massifs ont été fabriqués par frittage à chaud des poudres mécanosynthétisées. Les conditions de consolidation ont été évaluées et optimisées pour favoriser la formation de la phase cc et réduire la formation de carbures et d'oxydes résultant de la contamination. Les échantillons massifs optimisés présentent une phase majoritaire cubique centrée (> 95 % volumique) avec un paramètre de maille de 2,92 Å et une très petite quantité de carbures (M6C, M23C6) et d'oxydes (Al2O3). La phase cc est stable après recuit à 950 °C pendant 10 h. De plus, l'alliage présente une dureté très élevée jusqu'à 950 HV2N. Les essais de compression de l'échantillon massif optimisé, entre la température ambiante et 800 °C, révèlent des propriétés prometteuses, en particulier entre 600 et 700 °C. L'alliage présente un comportement fragile entre la température ambiante et 400 °C. Cependant, l'alliage commence à démontrer un certain degré de plasticité à 500 °C. À 600 °C, la limite d'élasticité est de 1022 MPa, tandis que la déformation à la rupture est d'environ 22 %High Entropy Alloys (HEAs) are a new type of multicomponent alloys. They contain at least five elements with the content of each between 5 and 35 at. %. The high configuration entropy, which is the source of the name of the whole family of alloys, together with other parameters, such as mixing enthalpy, atomic size difference, electronegativity difference, or valence electron concentration, stabilize a solid solution instead of complex intermetallic compounds. Promising properties and interesting microstructures focus the attention of the scientific community to HEAs.In this work, the novel Al-Cr-Fe-Mn-Mo high entropy alloy family was studied. The microstructural and chemical analyses were performed by XRD, Mössbauer spectrometry, SEM, TEM, EDX, EBSD. In the first stage, parametric approach calculations were carried out to optimize the chemical composition of the alloy. The selected compositions were prepared by mechanical alloying in different devices. The optimized conditions that ensure maximum chemical homogeneity of powder and the small contamination from balls and vial materials were chosen. In most of the powders, two bcc phases form during mechanical alloying with the lattice parameters about 3.13 Å (bcc#1) and 2.93 Å (bcc#2). The heat treatment of powder results in several phase transformations (e.g., the formation of the χ phase). The annealing at 950 °C for 1 h promotes the significant increase of volume fraction of the bcc#2 phase, while the bcc#1 and χ disappear. Nevertheless, small fractions of carbides and oxides were found. The bulk samples were fabricated by hot press sintering of the optimized mechanically alloyed powders. The conditions of consolidation were evaluated and optimized to promote the formation of the bcc phase and reduce the formation of carbides and oxides resulting from the contamination during mechanical alloying and sintering. The optimized bulk samples present a major disordered body-centered cubic phase (> 95 % of volume fraction) with a lattice parameter of 2.92 Å and a very small fraction of carbides (M6C, M23C6) and oxides (Al2O3). The bcc phase is stable after annealing at 950 °C for 10 h. Moreover, the alloy presents very high hardness up to 950 HV2N. The compression tests of the optimized bulk sample from room temperature to 800 °C reveal promising properties, especially between 600 and 700 °C. The alloy shows brittle behavior between room temperature and 400 °C. However, the alloy starts to demonstrate some degree of plasticity at 500 °C. At 600 °C, the yield strength is 1022 MPa, while strain to failure is about 22 %
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Poerschke, David L. "Mechanical Properties of Oxide Dispersion Strengthened Molybdenum Alloys". Cleveland, Ohio : Case Western Reserve University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=case1238018041.
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Engman, Alexander. "Mechanical properties of bulk alloys and cemented carbides". Thesis, KTH, Materialvetenskap, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-230897.
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The usage of cobalt (Co) as binder phase material in cemented carbides has been questioned becauseof the potential health hazards associated with cobalt particle inhalation. Cobalt is used because ofits excellent adhesive and wetting properties, combined with adequate mechanical properties. Thepurpose of this work is to investigate the mechanical properties of Fe-Ni bulk alloys and WC-Cocemented carbides using Integrated Computational Materials Engineering (ICME) methods com-bined with FEM data. The report investigates the mechanical properties of several bulk alloys inthe Fe-Ni system as a function of void size and fraction. FEM indentation and FEM fracture datais interpolated and used to model the hardnessHand fracture toughnessKIc. A precipitationhardening model based on the Ashby-Orowan’s equation is implemented to predict the e↵ect on theyield strength from precipitated particles. A model for solid solution hardening is also implemented.Existing models are used to simulate the properties of WC-Co cemented carbides together with thesolid solution hardening model. Results show that the simulated properties of the Fe-Ni bulk alloysare comparable to those of cobalt. However, the results could not be confirmed due to a lack ofexperimental data. The properties of WC-Co cemented carbides are in reasonable agreement withexisting experimental data, with an average deviation of the hardness by 11.5% and of the fracturetoughness by 24.8%. The conclusions are that experimental data for di↵erent Fe-Ni bulk alloys isneeded to verify the presented models and that it is possible to accurately model the properties ofcemented carbides.Anv¨andandet av kobolt (Co) som bindefas-material i h°ardmetall har blivit ifr°agasatt som en f¨oljdav av de potentiella h¨alsoriskerna associerade med inhalering av koboltpartiklar. Kobolt anv¨ands p°agrund av dess utm¨arkta vidh¨aftande och v¨atande egenskaper, kombinerat med tillr¨ackliga mekaniskaegenskaper. Syftet med detta arbete ¨ar att unders¨oka de mekaniska egenskaperna hos Fe-Ni bulklegeringarochWC-Co h°ardmetall genom att anv¨anda Integrated Computational Materials Engineering(ICME) metoder kombinerat med FEM-data. Rapporten unders¨oker de mekaniska egenskapernahos flera bulklegeringar i Fe-Ni systemet. FEM-indentering och FEM-fraktur data interpoleras ochanv¨ands f¨or att modellera h°ardheten H och brottsegheten KIc. En modell f¨or utskiljningsh¨ardningbaserad p°a Ashby-Orowans ekvation implementeras f¨or att f¨oruts¨aga e↵ekten p°a brottgr¨ansen av utskiljdapartiklar. ¨Aven en modell f¨or l¨osningsh¨ardning implementeras. Existerande modeller anv¨andsf¨or att simulera egenskaperna hos WC-Co h°ardmetall tillsammans med modellen f¨or l¨osningsh¨ardning.Resultaten visar att de simulerade egenskaperna hos Fe-Ni bulklegeringar ¨ar j¨amf¨orbara medde f¨or kobolt. Dock kan de inte bekr¨aftas p°a grund av avsaknad av experimentell data. Egenskapernahos WC-Co h°ardmetall st¨ammer rimligt ¨overens med existerande experimentell data, meden genomsnittlig avvikelse av h°ardheten med 11.5% och av brottsegheten med 24.8%. Slutsatserna¨ar att det beh¨ovs experimentell data f¨or Fe-Ni bulklegeringar f¨or att kunna verifiera modellernasnoggrannhet och att det ¨ar m¨ojligt att f¨oruts¨aga egenskaperna hos h°ardmetall.
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Dighe, Manish D. "Quantitative characterization of damage evolution in an Al-Si-Mg base cast alloy". Thesis, Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/20219.
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Esho, Faris Nora. "Creep Properties of Magnesium Alloys AE44 and AZ91". Thesis, Högskolan i Jönköping, Tekniska Högskolan, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-44261.
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Wang, Guisheng. "Ab initio prediction of the mechanical properties of alloys". Doctoral thesis, KTH, Tillämpad materialfysik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-169511.
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At the time of the 50th anniversary of the Kohn-Sham method, ab initio calculations based on density functional theory have formed an accurate, efficient, and reliable method to work on the properties of engineering materials. In this thesis, we use the exact muffin-tin orbitals method combined with the coherent-potential approximation to study the mechanical properties of high-technology materials. The thesis includes two parts: a study of long-range chemical order effects and a study of alloying effects on the mechanical properties of alloys. In the first part, we concentrate on the impact of chemical ordering on the mechanical properties. The long range order effect on the elastic constants behaves in a very different way for non-magnetic materials and ferromagnetic materials. For a non-magnetic Cu3Au, the long-range order effect on the elastic constants is very small. The Debye temperature does not show a strong chemical order dependence either. For a ferromagnetic material, on the other hand, the long-range chemical order produces considerable influence on C' in the ferromagnetic state, but negligible effect on C' in the paramagnetic state. The lattice parameter, bulk modulus $B$, and shear elastic constant C44 change slightly with the degree of long-rang order for both magnetic states. The Young's modulus E and the shear modulus G increase significantly with the degree of order in the ferromagnetic state, but the effect becomes weak as the system approaches the random regime.In the second part, the alloying effect of Mn/Ni on the lattice parameter, elastic constants, surface energy, and unstable stacking fault energy of bcc Fe is examined. The calculated results show that the lattice parameter of ferrite Fe is slightly altered upon Ni/Mn alloying the trend of which can be explained by the magnetism-induced pressure. Nickel addition decreases C' but has a negligible effect on C44, whereas manganese addition increases C44 and has a weak influence on C'. In both systems, the bulk modulus B shows a smooth second order variation. On the other hand, the surface energy and the unstable stacking fault (USF) energy decrease by adding Mn or Ni to Fe. For both planar fault energies, Ni shows a stronger effect than Mn. Segregation seems to have a minor effect on the surface and USF energies for dilute Fe-Ni and Fe-Mn alloys. The ductility can be estimated using available physical parameters via traditional phenomenological criteria like the Pugh ratio B/G, the Poisson ratio ν, the Cauchy pressure C12-C44, and the Rice ratio γs/γu .According to dislocation theory, a dislocation can not cross a grain boundary. Therefore, the study of dislocations is assumed to be limited to single-crystals. Several theoretical studies indicate that the cleavage plane is {001} in bcc crystals. Based on these information, we suggest that the resolved single-crystal tensile strength E[001] and the resolved single crystal shear strength G{110}<111> should be used to describe brittle cleavage and dislocation movement rather than polycrystalline parameters such as B and G. We demonstrate that all shear moduli G{lmn}<111> associated with the <111> Burgers vector take the same value 3C44C'/(C'+2C44), which could in fact explain the observed multiple slip in bcc systems. Due to the discrepancy between the resolved single-crystal elastic constants and the averaged polycrystalline elastic constants, the Pugh ratio B/G and the traditional criteria based on polycrystalline elastic constants lead to large differences for magnetic systems. Finally, we propose a new measure of the ductile-bittle behavior based on the ratio σclevage/Gresolved which gives the right experimental trend for Fe-Mn and Fe-Ni system.QC 20150616
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Xiaoqing, Li. "Mechanical Properties of Transition Metal Alloys from First-PrinciplesTheory". Doctoral thesis, KTH, Tillämpad materialfysik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-169493.
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The aim of the thesis is to investigate the alloying and temperature effects on the mechanical properties of body-centered cubic (bcc) random alloys. We employ the all-electron exact muffin-tin orbitals method in combination with the coherent-potential approximation. The second-order elastic constants reflect the mechanical properties of materials in the small deformation region, where the stress-strain relations are linear. Beyond the small elastic region, the mechanical properties of defect-free solids are described by the so called ideal strength. These two sets of physical quantities are the major topic of my investigations. In part one (papers I and II), the elastic constants and the ideal tensile strengths (ITS) are investigated as a function of Cr and Ti for the bccV-based random solid solution. We find that alloys along the equi-composition region exhibit the largest shear modulus and Young’s modulus, which is a resultof the opposite alloying effects obtained for the two cubic shear elastic constants C′ and C44. The classical Labusch-Nabarro solid-solution hardening (SSH) model extended to ternary alloys predicts a larger hardening effect in V-Ti than in V-Cr alloy. By considering a phenomenological expression for the ductile-brittle transition temperature (DBTT) in terms of Peierls stress and SSH, we show that the present theoretical results can account for the observed variations of DBTT with composition. Under uniaxial [001] tensile loading, the ITS of V is 12.4 GPa and the lattice fails by shear. Assuming isotropic Poisson contraction, the ITSs are 36.4 and 52.0 GPa for V in the [111] and [110] directions, respectively. For the V-based alloys, Cr increases and Ti decreases the ITS in all principal directions. Adding the same concentration of Cr and Ti to V leads to ternary alloys with similar ITS values as that of pure V. We show that the ITS correlates with the fcc-bcc structural energy difference and explain the alloying effects on the ITS based on electronic band structure theory. In part two (paper III), the alloying effect on the ITS of four bcc refractory HEAs based on Zr, V, Ti, Nb, and Hf is studied. Starting from ZrNbHf, we find that the ITS decreases with equimolar Ti addition. On the other hand, if both Ti and V are added to ZrNbHf, the ITS is enhanced by about 42%. An even more captivating effect is the ITS increase by about 170%, if Ti and V are substituted for Hf. We explain the alloying effect on the ITS based on the d-band filling. We explore an intrinsic brittle-to-ductile transition, which arises due to an alloying-driven change of the failure mode under uniaxial tension. Our results indicate that intrinsically ductile HEAs with high intrinsic strength can be achieved by controlling the proportion of group four elements to group five elements. In part three (papers IV and V), the ITS of bcc ferromagnetic Fe-based random alloys is calculated as a function of compositions. The ITS of Fe is calculated to be 12.6 GPa under [001] direction tension, which is in good agreement with the available theoretical data. For the Fe-based alloys, we predict that V, Cr, and Co increase the ITS, while Al and Ni decrease it. Manganese yields a weak non-monotonic alloying behavior. We show that the previously established ideal tensile strengths model based on structural energy differences for the nonmagnetic V-based alloys is of limited use in the case of Fe-bases alloys, which is attributed to the effect of magnetism. We find that upon tension all investigated solutes strongly alter the magnetic response of the Fe host from the unsaturated towards a stronger ferromagnetic behavior. In part four (paper VI), the temperature effect on the ITS of bcc Fe and Fe0.9Co0.1alloy is studied. We find that the ITS of Fe is only slightly temperature dependent below∼500K but exhibits large thermal gradients at higher temperatures. Thermal expansion and electronic excitations have an overall moderate effect, but magnetic disorder reduces the ITS with a pronounced 90% loss in strength in the temperature interval∼500 - 920K. Such a dramatic temperature effect far below the magnetic transition temperature has not been observed for other micro-mechanical properties of Fe. We demonstrate that the strongly reduced Curie temperature of the distorted Fe lattices compared to that of bcc Fe is primarily responsible for the onset of the drop of the intrinsic strength. Alloying additions, which have the capability to partially restore the magnetic order in the strained Fe lattice, push the critical temperature for the strength-softening scenario towards the magnetic transition temperature of the undeformed lattice. This can result in a surprisingly large alloying-driven strengthening effect at high temperature as illustrated in our work in the case of Fe-Co alloyQC 20150616
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Zander, Johan. "Modelling mechanical properties by analysing datasets of commercial alloys". Licentiate thesis, Stockholm : Industriell teknik och management, Kungliga Tekniska högskolan, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4527.
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Kar, Sujoy Kumar. "Modeling of mechanical properties in alpha/beta-titanium alloys". The Ohio State University, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=osu1122570452.
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Sun, Ning. "Friction stir processing of aluminum alloys". Worcester, Mass. : Worcester Polytechnic Institute, 2009. http://www.wpi.edu/Pubs/ETD/Available/etd-050109-144331/.
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Bird, Nigel. "The mechanical properties of #gamma#-TiAl based single crystals". Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.244598.
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Keraan, Tauriq. "High temperature mechanical properties and behaviour of platinum-base alloys". Master's thesis, University of Cape Town, 2004. http://hdl.handle.net/11427/5524.
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Paray, Florence. "Heat treatment and mechanical properties of aluminum-silicon modified alloys". Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=41146.
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The commercial applications of cast Al-Si alloys depend to an important extent on controlling the morphology of the eutectic silicon through thermal modification in the solid state and/or chemical modification of the melt before the production of the casting. The effects of modification and/or heat treatment on the microstructure and the mechanical properties of 356 alloy have been investigated on both permanent mold and sand cast samples. Strontium (0.02%) and sodium (0.01%) were used to produce well modified microstructures. The importance of the amount of modifier used was also examined in producing castings with 0.002% Sr and 0.08% Sr. Production parameters such as solution heat treatment time and artificial aging time were examined.Microstructural assessment was done by quantitative metallography using image analysis coupled to SEM while mechanical testing comprised tensile testing, hardness and microhardness measurements as well as impact tests.
The greatest improvement in mechanical properties obtained with modification was observed for the lower rates of solidification, i.e sand casting. The effect of modification on the heat treatment response of 356 alloy was investigated. The differences between unmodified and modified microstructures were more important in sand cast samples than in permanent mold cast samples. After one hour of solution heat treatment at 540$ sp circ$C, both permanent mold unmodified and modified microstructures became similar in terms of silicon particle size and sphericity. The processes which led to this were different. Silicon platelets in the unmodified structures segmented while silicon particles in the modified alloy coarsened. The final result was however the same. In sand cast alloy, the initial microstructural differences persisted after up to 12 hours of solution treatment. The coarser the initial as-cast microstructure, the greater the improvements associated with modification and heat treatment.
It was also found that porosity caused by modification can negate many of the microstructural benefits by decreasing tensile strength and percent elongation. It was demonstrated that modification also has an influence on the aluminum matrix. The hardness of modified alloy was found to be less after the T6 temper than in unmodified alloy. This was reflected in a lower yield strength of modified 356 alloy.
Quantitative microstructure-mechanical property relationships were established for the permanent mold samples. The best silicon-structure characteristics to predict the tensile properties were found to be the particle count per unit area and the particle area.
It was also determined that hardness can be a simple and inexpensive means whereby ultimate tensile strength and yield strength of 356 alloy in the T4 condition or T6 condition can be estimated.
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Li, Dongfa. "Microstructures and mechanical properties of palladium-silver dental casting alloys". Columbus, Ohio : Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1143105462.
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Seifeddine, Salem. "Characteristics of cast aluminium-silicon alloys : microstructures and mechanical properties /". Linköping : Univ, 2006. http://www.bibl.liu.se/liupubl/disp/disp2006/tek1058s.pdf.
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Cao, Haiping. "Characteristics of cast magnesium alloys : microstructures, defects and mechanical properties /". Jönköping : Linköping : Div. of Component Technology - Castings ; Dept. of Mechanical Engineering, Univ, 2005. http://www.bibl.liu.se/liupubl/disp/disp2005/tek955s.pdf.
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Ouyang, S. "Effect of hydrogen on the mechanical properties of titanium alloys". Thesis, University of Newcastle Upon Tyne, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239044.
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Jing, Wu. "Microstructure and mechanical properties of Mg-Zn-(Y/Gd) alloys". Thesis, University of Birmingham, 2016. http://etheses.bham.ac.uk//id/eprint/7100/.
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As-cast Mg\(_9\)\(_4\)Zn\(_2\)Y\(_4\) alloy has been subjected to compression and equal channel angular pressing (ECAP) separately. The as-cast alloy contains mainly a long-period stacking ordered (LPSO) phase and a Mg\(_2\)\(_4\)Y\(_5\) phase as secondary phases. During compression, kinking occurs in the LPSO phase and LPSO/Mg mixture. Most kink boundaries of LPSO are composed of basal < a > type dislocations. The rotation axes of the kink boundaries in LPSO/Mg are preferentially located in the (0001) plane. ECAP processing develops a bimodal microstructure consisting of large deformed grains and sub-micron dynamically recrystallised (DRXed) grains. The DRXed grains are mainly located along the original grain boundaries. Kink boundaries also acts as DRX nucleation sites. The ECAP processing increased significantly the strength of the alloy. In the as-cast Mg-Zn-Y alloys, the main secondary phase changes when different ratios of Zn/Y are applied: LPSO (Zn/Y ratio is 0.5) → LPSO+W (Zn/Y ratio is 1, W is Mg\(_3\)Zn\(_3\)Y\(_2\)) → W (Zn/Y ratio is 2.33). When Y is half replaced by Gd, the types of phases are similar. When Y is replaced fully by Gd, W phase becomes the main secondary phase. The structure of the LPSO also changes with different Zn/Y ratios and the presence of Y or Gd.
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El-Sayed, Mahmoud Ahmed Mahmoud. "Double oxide film defects and mechanical properties in aluminium alloys". Thesis, University of Birmingham, 2012. http://etheses.bham.ac.uk//id/eprint/3924/.
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Double oxide films (bifilms) are significant defects in light alloy castings which were reported to have detrimental effects on the reliability of the castings. The research reported here was aimed at studying how these defects develop with time. The results suggested that both O and N inside the bifilm would be consumed by reaction with the surrounding melt, and that H might be diffused into the defect. Based on the estimated reactions rates the time required for the consumption of the atmosphere inside a bifilm entrained in pure Al, Al-7wt.%Si-0.3wt.%Mg and Al-5wt.%Mg alloy melts, was determined to be 538, 1509 and 345 seconds respectively. The results also suggested the occurrence of two competing mechanisms during holding of the castings in the liquid state before solidification. The first mechanism was related to the consumption of the bifilm atmosphere, which might reduce the size of bifilms and therefore increase the Weibull moduli the UTS and the % elongation. The other mechanism was the diffusion of H into the bifilms, which would be expected to increase their sizes and reduce the moduli. This research therefore could lead to the development of new techniques by which bifilms might be deactivation in light alloy castings.
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Li, Xiaoqing. "Mechanical Properties of Transition Metal Alloys from First-Principles Theory". Licentiate thesis, KTH, Tillämpad materialfysik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-142666.
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The aim of the thesis is to investigate the alloying effect on the mechanical properties of random alloys using the all-electron exact muffin-tin orbitals methodin combination with the coherent-potential approximation. The second-order elastic constants describe the mechanical properties of materials in the small deformation region, where the stress-strain relations arelinear. Beyond the small elastic region, the mechanical properties of dislocation-free solids are described by the ideal strength. The elastic constants and ideal tensile strengths have been investigated as a function of Cr and Ti for the body centered cubic V-based random solidsolution. Alloys along the equi-composition region are found to exhibit the largest shear and Young’s modulus as a result of the opposite alloying effectsobtained for the two cubic shear elastic constants C' and C44.Classical solid-solution hardening (SSH) model predicts larger hardening effect in V-Ti thanin V-Cr alloy. By considering a phenomenological expression for the ductile-brittle transition temperature (DBTT) in terms of Peierls stress and SSH, itis shown that the present theoretical results can account for the variations of DBTT with composition. Under uniaxial [001] tensile loading, the ideal tensilestrength of V is 12.4 GPa and the lattice fails by shear. Assuming isotropic Poisson contraction, the ideal tensile strength are 36.4 and 52.0 GPa for V inthe [111] and [110] directions, respectively. For the V-based alloys, Cr increases and Ti decreases the ideal tensile strength in all principal directions. Addingthe same concentration of Cr and Ti to V leads to ternary alloys with similar ideal tensile strength values as that of pure V. The alloying effects on the idealtensile strength are explained using the electronic band structure. The ideal tensile strengths of bcc ferromagnetic Fe-based random alloys have been calculated as a function of compositions. The ideal tensile strength of Fe in the [001] direction is calculated to be 12. 6GPa,in agreement with the available data. For the Fe-based alloys, we predict that V, Cr, and Co increase the ideal tensile strength, while Al and Ni decrease it. Manganese yields a weak non-monotonous alloying behavior. We show that the limited use of the previouslyestablished ideal tensile strengths model based on structural energy differences in the case of Fe-bases alloys is attributed to the effect of magnetism. We find that upon tension all the investigated solutes strongly alter the magneticresponse of the Fe host from the unsaturated towards a stronger ferromagnetic behavior.QC 20140312
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Yu, Hao. "The microstructure and tribo-mechanical properties of HIPed stellite alloys". Thesis, Heriot-Watt University, 2007. http://hdl.handle.net/10399/2159.
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Kerry, S. "Microstructure and mechanical properties of high strength cast aluminium alloys". Thesis, University of Bath, 1987. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.376328.
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Matulich, Ryan Douglas. "Post-fire Mechanical Properties of Aluminum Alloys and Aluminum Welds". Thesis, Virginia Tech, 2011. http://hdl.handle.net/10919/32727.
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The focus of this research was to quantify the post-fire mechanical properties of 5083-H116 and 6082-T6 aluminum alloys. Post-fire exposure is considered heating the material to a particular temperature then cooling the material back to room temperature. The research included evaluating parent materials as well as welded samples.
Post-fire mechanical properties of parent materials were evaluated at temperatures ranging from ambient to 500oC with isothermal and transient heating. Changes in material properties were evaluated through static tensile tests and hardness testing on cooled samples. Using this data, an assessment was performed to investigate the relationship between hardness and mechanical properties. For the alloys evaluated, empirical relationships were found between Vickers hardness and post-fire strength.
Testing was also performed on butt welded samples of 6082-T6 exposed isothermally to temperatures ranging from ambient to 500oC. Vickers hardness profiles were measured across a sample to quantify the hardness of the weld, heat affected zone, and parent material. This was performed at room temperature and following different heat exposures. Static tensile tests were used to evaluate the effect of reheating on the welded samples. Post-fire strength of welded samples was strongly affected by weld geometry. Parent material hardness varied with reheating while weld hardness remained constant. At select temperatures, this resulted in the weld having a higher Vickers hardness than the parent material. Despite this tensile failure always occurred within the weld.Master of Science
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Mohit, Joshi. "Fabrication of Fine-Grained Magnesium Alloys and Their Mechanical Properties". 京都大学 (Kyoto University), 2017. http://hdl.handle.net/2433/225561.
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Clopet, Caroline Roberta. "Microstructural evolution and mechanical properties of deeply undercooled eutectic alloys". Thesis, University of Leeds, 2016. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.713488.
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An experimental investigation has been undertaken in an attempt to determine the mechanism of formation of anomalous eutectics. A melt fluxing method and a drop tube technique have been used to undercool eutectic Ag-Cu alloy. During the fluxing experiments, the growth fronts of the undercooled alloy samples have been monitored using high speed camera imaging. The evolved microstructures of the fluxed samples undercooled ≤ 60 K exhibit a trizonal structure consisting of mixed anomalous and lamellar eutectic. The high speed camera imaging reveals that the growth front propagates in a spasmodic manner, where periods of rapid growth are separated by significant intervals in which growth totally arrests. Depending upon undercooling, growth is either continuous or spasmodic. Continuous growth is characteristic of the advancement of a planar front, while during spasmodic growth a double recalescence occurs, the first of which is characteristic of the propagation of a dendritic front. The microstructure of drop tube processed Ag-Cu samples comprises of a mixture of lamellar and anomalous eutectic structures and a silver-rich phase, which appears as spherical inclusions at the eutectic cell boundaries. It is concluded that, during spasmodic growth, the propagation of eutectic dendrites is observed, which subsequently remelt to form the anomalous eutectic, while the lamellar eutectic grows during post-recalescence cooling. It is also postulated that this eutectic dendrite may be growing away from the eutectic point at high growth rates, which could lead to silver building up ahead of the interface that, in the drop tube samples, leads to the formation of the silver-rich phase observed at the cell boundaries. In the fluxed samples, as the silver builds up, the dendrite is no longer viable and growth arrests until sufficient silver atoms have diffused into the bulk liquid for the transient growth cycle to restart.
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Church, Benjamin Cortright. "High conductivity alloys for extruded metallic honeycomb". Thesis, Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/21283.
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Fan, Zhongyun. "Microstructure and mechanical properties of multiphase materials". Thesis, University of Surrey, 1993. http://epubs.surrey.ac.uk/776187/.
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A systematic method for quantitative characterisation of the topological properties of two-phase materials has been developed, which offers an effective way for the characterisation of twophase materials. In particular, a topological transformation has been proposed, which allows a two-phase microstructure with any grain size, grain shape and phase distribution to be transformed into a three-microstructural-element body (3-E body). It has been shown that the transformed 3·E body is mechanically equivalent along the aligned direction with the original microstructure. The Hall·Petch relation developed originally for single-phase metals and alloys has been successfully extended to two~ductile-phase alloys. It has been shown that the extended Hall- Petch relation can separate the individual contribution to the overall efficiency of different kinds of boundaries as obstacles to dislocation motion. A new approach to deformation behaviour of two-ductile-phase alloys has been developed based on Eshelby's continuum transformation theory and the microstructural characterisation developed in this thesis. In contrast to the existing theories of plastic deformation, this approach can consider the effect of microstructural parameters, such as volume fraction, grain size, grain shape and phase distribution. In particular, the interactions between particles of the same phase have also been taken into account by the topological transformation. Consequently, the newly developed theory can be applied in principle to a composite with any volume fraction. This approach has been applied to various two-ductile-phase alloys to predict the true stress·true strain curves, the internal stresses and the in situ stress and plastic strain distribution in each microstructural element. It is found that the theoretical predictions are in very good agreement with the experimental results drawn from the literature. A new approach has also been developed for the prediction of the Young's moduli of particulate two-phase composites. Applications of this approach to AVSiCp and Co/WCp composite systems and polymeric matrix composites have shown that the present approach is superior to both the Hashin and Shtrikman's bounds and the mean field theory in terms of the good agreement between the theoretical predictions and the experimental results from the literature. Furthermore, this approach can be extended to predict the Young's moduli of multiphase composites by iteration. This iteration approach has been tested on some Ti-6Al- 4V-TiB composites. An experimental investigation has being carried out to study the in situ Ti-6AI-4V-TiB (hereafter, Ti/TiB is used for convenience) metal matrix composites produced through a rapid solidification route. Production of in situ Ti/fiB metal matrix composites through rapid solidification route can completely exclude problems such as wetting and chemical reaction encountered by alternative production routes. The relevant microstructural phenomena in in situ Ti/TiB metal matrix composites, such as the growth habit of TiB phase and the w-phase transformation, have also been investigated. The TiB phase in the consolidated composites exhibits two distinguished morphologies: needle-shaped TiB and nearly equiaxed TiB. The needle-shaped TiB phase formed mainly from the solidification process always grows along the [010] direction of the B27 unit cell, leaving the cross-section of the needles consistently enclosed either by (100) and {101 1 type planes or by (100) and {102l type planes. It is also found that the cross-sections of the nearlyequiaxed TiB particles formed from the B supersaturated Ti solid solution are also bounded by the same planes as above, although the growth rate along the [010] direction has been considerably reduced. Experiments have also been perfonned to investigate the effect of pre-hipping heat treatments on the microstructure of RS products. It is found that pre-hipping heat treatments at a temperature below 800°C can lead to the precipitation of fine equiaxed TiB particles from the B super-saturated Ti solid solution, which are uniformly distributed throughout the a+B matrix. The majority of those TiB precipitates do not grow up by Ostwald ripening process after long time exposure at higher temperature. Microstructural examination has confirmed the existence of a B to w transformation in RS Ti- 6AI-4V alloys with and without B addition after consolidation. In addition, the B to w transformation has also been observed in RS Ti-Mn-B alloys after consolidation. Systematic electron diffraction work on the B-phase offers a strong experimental evidence for the B to W transformation mechanism proposed by Williams et al.
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Cain, Victoria. "High temperature creep behaviour niobium bearing ferritic stainless steels". Thesis, Cape Peninsula University of Technology, 2005. http://hdl.handle.net/20.500.11838/1249.
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A thesis submitted to the Faculty of Engineering in
fulfilment of the requirements for the degree of Master of
Technology in Mechanical Engineering
2005The objective of this project was to monitor the high temperature creep behaviour of 441 stainless steel. Two different alloys of 441 were investigated; the main difference between them being the Niobium content. Particularly imporlant to the project was how the Niobium content and grain size affected the creep resistance of the material. Creep tests were performed using purpose built constant load creep test rigs. Initially the rigs were not suitable for the testing procedures pertaining to this project. This was due to persistent problems being experienced with regards the reliability and reproducibility of the rigs. After various modifications were made the results produced from the rigs were consistent. Creep test data was used in order to determine the mechanism of creep that is operative within the material (at a predetermined temperature) under a predetermined load. Particular attention was paid to the resulting stress exponents. in order to identify the operative creep mechanism. The identification of the operative creep mechanisms was also aided by microscopical analysis. This analysis was also necessary to monitor how the grain size had altered at various annealing temperatures. Heat treatment was used as a method to alter the high temperature strength and microstructure of the material. Heat treatments were performed at various temperatures in order to determine the ideal temperature to promote optimum creep resistance of 441. All heat treatments were performed in a purpose designed and built high temperature salt bath furnace. The commissioning of the salt bath formed part of the objectives for this project. Sag testing was also conducted, using purpose built sag test rigs. It was necessary to design and manufacture a sag test rig that could be comparable to the industry accepted method of sag testing known as the two-point beam method, as this method is believed to produce inconsistent results. Conclusions have been drawn from the results of the data and from previous research on the subject matter.
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Hill, Glen. "Phase equilibria in the La₂O₃-MoO₂-MoO₃ and Y₂O₃-M₀O₂-M₀O₃ systems". Thesis, Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/20744.
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GONCALVES, VALERIA de S. "Influencia de agentes controladores de processo na sintese por combustao mecanicamente ativada do NbAlsub(3)". reponame:Repositório Institucional do IPEN, 2008. http://repositorio.ipen.br:8080/xmlui/handle/123456789/9351.
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Made available in DSpace on 2014-10-09T12:26:11Z (GMT). No. of bitstreams: 0Made available in DSpace on 2014-10-09T14:10:39Z (GMT). No. of bitstreams: 0
Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Yao, Yingshan. "The influence of niobium content and cooling rate on mechanical properties of grey cast iron". Thesis, KTH, Materialvetenskap, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-244999.
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This project mainly investigated how the niobium(Nb) content influences the microstructure and mechanical properties of grey cast iron. Considering the mechanism, the study also analyzes the relationship between microstructure and mechanical properties. Generally, the work is based on 127 test bars/samples from two cylinder heads and three batches of plates, which were studied by measuring tensile strength, microhardness, graphite size, carbide amount and chemistry. The result data has been evaluated with statistical methods. The experiments mainly included the preparation of the samples for test and analysis. The mechanical properties in this study are evaluated by the tensile strength of the grey cast iron. Meanwhile, various microscopies were applied to observe how niobium and cooling rate influence the microstructure. Finally, from the analysis results, it tells that the niobium does affect the tensile strength of grey cast iron. Higher the niobium content is, higher the tensile strength is. The computed result based on the data also shows niobium’s strong effect. The faster cooling rate will increase the tensile strength and pearlite microhardness of grey cast iron as well. The carbide amount of grey cast iron can be increased by the addition of niobium content. Furthermore, some future work needs to be done to explain the unsolved problem in this result. The reasons of why a specific position A-2-d of plates has high values of tensile strength demand more microstructure investigation. For the niobium influence, more experiments and data containing a larger range of niobium content also need to be done to prove the mathematics results in this report.Detta projekt undersökte huvudsakligen hur innehållet av niob (Nb) påverkar gråstålens mikrostruktur och mekaniska egenskaper. Med tanke på mekanismen analyserar undersökningen även förhållandet mellan mikrostruktur och mekaniska egenskaper. Arbetet baseras i allmänhet på 127 provstänger / prover från två cylinderhuvuden och tre satser av plattor, vilka studerades genom mätning av draghållfasthet, mikrohårdhet, grafitstorlek, karbidmängd och kemi. Resultatdata har utvärderats med statistiska metoder. Experimenten inbegriper huvudsakligen beredningen av proven för test och analys. De mekaniska egenskaperna i denna studie utvärderas av gråstålets draghållfasthet. Under tiden applicerades olika mikroskopier för att observera hur niob- och kylhastigheten påverkar mikrostrukturen. Slutligen, från analysresultaten, berättar den att niobet påverkar draghållfastheten hos grågjutjärn. Ju högre niobinnehållet är, desto högre är draghållfastheten. Det beräknade resultatet baserat på data visar också niobins starka effekt. Den snabbare kylhastigheten ökar också draghållfastheten och pearliten-mikrohårdheten hos grågjutjärn. Karbidmängden av grågjutjärn kan ökas genom tillsats av niobhalt. Vidare måste vissa framtida arbeten göras för att förklara det olösta problemet i detta resultat. Skälen till varför en specifik position A-2-d av plattor har höga dragkrafter kräver mer mikrostrukturundersökning. För niobinpåverkan måste fler experiment och data som innehåller ett större antal niobinnehåll också göras för att bevisa matematikresultaten i denna rapport.
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Rudolf, Christopher Charles. "Microstructure and Mechanical Properties of Nanofiller Reinforced Tantalum-Niobium Carbide Formed by Spark Plasma Sintering". FIU Digital Commons, 2016. http://digitalcommons.fiu.edu/etd/2596.
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Ultra high temperature ceramics (UHTC) are candidate materials for high temperature applications such as leading edges for hypersonic flight vehicles, thermal protection systems for spacecraft, and rocket nozzle throat inserts due to their extremely high melting points. Tantalum and Niobium Carbide (TaC and NbC), with melting points of 3950°C and 3600°C, respectively, have high resistivity to chemical attack, making them ideal candidates for the harsh environments UHTCs are to be used in. The major setbacks to the implementation of UHTC materials for these applications are the difficulty in consolidating to full density as well as their low fracture toughness. In this study, small amounts of sintering additive were used to enhance the densification and Graphene Nanoplatelets (GNP) were dispersed in the ceramic composites to enhance the fracture toughness. While the mechanisms of toughening of GNP addition to ceramics have been previously documented, this study focused on the anisotropy of the mechanisms. Spark plasma sintering was used to consolidate both bulk GNP pellets and near full relative density TaC-NbC ceramic composites with the addition of both sintering aid and GNP and resulted in an aligned GNP orientation perpendicular to the SPS pressing axis that allowed the anisotropy to be studied. In situ high load indentation was performed that allowed real time viewing of the deformation mechanisms for enhanced analysis. The total energy dissipation when indenting the bulk GNP pellet in the in-plane GNP direction was found to be 270% greater than in the out-of-plane orientation due to the resulting deformation mechanisms that occurred. In GNP reinforced TaC-NbC composites, the projected residual damaged area as a result of indentation was 89% greater when indenting on the surface of the sintered compact (out-of-plane GNP orientation) than when indenting in the orthogonal direction (in-plane GNP orientation) which is further evidence to the anisotropy of the GNP reinforcement.
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Pauly, Simon. "Phase formation and mechanical properties of metastable Cu-Zr-based alloys". Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-39545.
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In the course of this PhD thesis metastable Cu50Zr50-xTix (0≤ x ≤ 10) and (Cu0.5Zr0.5)100-xAlx (5 ≤ x ≤ 8) alloys were prepared and characterised in terms of phase formation, thermal behaviour, crystallisation kinetics and most importantly in terms of mechanical properties.
The addition of Al clearly enhances the glass-forming ability although it does not affect the phase formation. This means that the Cu-Zr-Al system follows the characteristics of the binary Cu-Zr phase diagram, at least for Al additions up to 8 at.%. Conversely, the presence of at least 6 at.% Ti changes the crystallisation sequence of Cu50Zr50-xTix metallic glasses and a metastable C15 CuZrTi Laves phase (Fd-3m) precipitates prior to the equilibrium phases, Cu10Zr7 and CuZr2. A structurally related phase, i.e. the “big cube” phase (Cu4(Zr,Ti)2O, Fd-3m), crystallises in a first step when a significant amount of oxygen, on the order of several thousands of mass-ppm (parts per million), is added. Both phases, the C15 Laves as well as the big cube phase, contain pronounced icosahedral coordination and their formation might be related to an icosahedral-like short-range order of the as-cast glass. However, when the metallic glasses obey the phase formation as established in the binary Cu-Zr phase diagram, the short-range order seems to more closely resemble the coordination of the high-temperature equilibrium phase, B2 CuZr.
During the tensile deformation of (Cu0.5Zr0.5)100-xAlx bulk metallic glasses where B2 CuZr nanocrystals precipitate polymorphically in the bulk and some of them undergo twinning, which is due to the shape memory effect inherent in B2 CuZr. Qualitatively, this unique deformation process can be understood in the framework of the potential energy landscape (PEL) model. The shear stress, applied by mechanically loading the material, softens the shear modulus, thus biasing structural rearrangements towards the more stable, crystalline state. One major prerequisite in this process is believed to be a B2-like short-range order of the glass in the as-cast state, which could account for the polymorphic precipitation of the B2 nanocrystals at a comparatively small amount of shear. Diffraction experiments using high-energy X-rays suggest that there might be a correlation between the B2 phase and the glass structure on a length-scale less than 4 Å. Additional corroboration for this finding comes from the fact that the interatomic distances of a Cu50Zr47.5Ti2.5 metallic glass are reduced by cold-rolling. Instead of experiencing shear-induced dilation, the atoms become more closely packed, indicating that the metallic glass is driven towards the more densely packed state associated with the more stable, crystalline state.
It is noteworthy, that two Cu-Zr intermetallic compounds were identified to be plastically deformable. Cubic B2 CuZr undergoes a deformation-induced martensitic phase transformation to monoclinic B19’and B33 structures, resulting in transformation-induced plasticity (TRIP effect). On the other hand, tetragonal CuZr2 can also be deformed in compression up to a strain of 15%, yet, exhibiting a dislocation-borne deformation mechanism.
The shear-induced nanocrystallisation and twinning seem to be competitive phenomena regarding shear band generation and propagation, which is why very few shear offsets, due to shear banding, can be observed at the surface of the bulk metallic glasses tested in quasistatic tension. The average distance between the crystalline precipitates is on the order of the typical shear band thickness (10 - 50 nm) meaning that an efficient interaction between nanocrystals and shear bands becomes feasible. Macroscopically, these microscopic processes reflect as an appreciable plastic strain combined with work hardening.
When the same CuZr-based BMGs are tested in tension at room temperature and at high strain rate (10-2 s-1) there seems to be a “strain rate sensitivity”, which could be related to a crossover of the experimental time-scale and the time-scale of the intrinsic deformation processes (nanocrystallisation, twinning, shear band generation and propagation). However, further work is required to investigate the reasons for the varying slope in the elastic regime.
As B2 CuZr is the phase, that competes with vitrification, it precipitates in a glassy matrix if the cooling rate is not sufficient to freeze the structure of the liquid completely. The pronounced work hardening and the plasticity of the B2 phase, which are a result of the deformation-induced martensitic transformation, leave their footprints in the stress-strain curves of these bulk metallic glass matrix composites. The behaviour of the yield strength as a function of the crystalline volume fraction can be captured by the rule of mixtures at low crystalline volume fractions and by the load bearing model at high crystalline volume fractions. In between both of these regions there is a transition caused by percolation (impingement) of the B2 crystals. Furthermore, the fracture strain can be modelled as a function of the crystalline volume fraction by a three-microstructural-element body and the results imply that the interface between B2 crystals and glassy matrix determines the plastic strain of the composites. The combination of shape memory crystals and a glassy matrix leads to a material with a markedly high yield strength and an enhanced plastic strain.
In the CuZr-based metastable alloys investigated, there is an intimate relationship between the microstructure and the mechanical properties. The insights gained here should prove useful regarding the optimisation of the mechanical properties of bulk metallic glasses and bulk metallic glass composites.
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Hill, Davion M. "Microstructure and mechanical properties of titanium alloys reinforced with titanium boride". Columbus, Ohio : Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1150402807.
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Okulov, Ilya. "Microstructure and mechanical properties of new composite structured Ti-based alloys". Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-160897.
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The demanding structural applications (e.g. aerospace, biomedical, etc.) require new materials with improved mechanical performance. The novel Ti-based dendrite + nano-/ultrafine-structured (Ti-based DNUS) composites exhibit an advantageous combination of high compressive strength (2000 – 2500 MPa) and large compressive ductility (10 – 30 %) already in the as-cast state [1,2] and, therefore, can be referred as high-performance materials. However, these Ti-based composites frequently exhibit very low or even lack of tensile ductility [3]. Therefore, the aim of this research work is to develop high strength Ti-based DNUS composites with pronounced tensile plasticity and to correlate the mechanical properties with their microstructure. In order to reach the goal, the high-strength Ti66Nb13Cu8Ni6.8Al6.2 (at.%) alloy exhibiting large compressive ductility [4] was selected for the modification. The microstructure of Ti66Nb13Cu8Ni6.8Al6.2 is composed of two metallographic constituents including β-Ti dendrites and an interdendritic component. The β-Ti dendrites are enriched in Nb and, therefore, Nb is referred as “dendritic element” whereas the interdendritic component is enriched in Ni and Cu and, therefore, these are referred as “interdendritic elements”. To perform a systematic study of the “interdendritic elements” (Ni, Cu and Co) effect on microstructure, a number of alloys with different concentration and types of alloying elements (Ti-Nb-Cu-Ni-Al, Ti-Nb-Co-Ni-Al, Ti-Nb-Cu-Co-Al and Ti-Nb-Ni(Co)-Al) were developed. It was shown that a higher concentration of the “interdendritic elements” in a composition within one alloy system corresponds to a higher volume fraction of the interdendritic component. Additionally, the crystal structure of the interdendritic phases is affected by type of the “interdendritic elements”. Since the most advanced applications (e.g. aerospace) require materials with high specific strengths, the new ductile Ti-Nb-Cu-Ni-Al alloys were modified to reduce their density, i.e. the Nb was substituted by lighter V. As a result, a new family of Ti-V-Cu-Ni-Al alloys with improved specific strength compared to the Ti-Nb-Cu-Ni-Al alloys was developed. Additionally, moduli of resilience of the Ti-V-Ni-Cu-Al alloys are superior when compared with those of the commercial Ti-based spring materials. The effect of microstructure on deformation of the newly developed alloys was studied through the in-situ microstructural analysis of samples at different strained states by means of scanning electron microscopy. To reveal the effect of the metallographic constituents on strength, the microhardness mapping of the new alloys was performed. Using the obtained empirical principles of microstructure adjustment, a new Ti68.8Nb13.6Co6Cu5.1Al6.5 (at.%) alloy with a large static toughness (superior to those of the recently developed Ti-based metallic glass composites) was developed. This large static toughness is due to both high strength and significant tensile plasticity. To study the effect of microstructure on tensile plasticity of Ti68.8Nb13.6Co6Cu5.1Al6.5 the in-situ microstructural analysis of samples at different strained states in the scanning electron microscope as well as the transmission electron microscopy studies were performedDer erhöhte Anspruch an strukturelle Anwendungen (z.B. Luftfahrt, Biomedizin, etc.) verlangt neue Werkstoffe mit verbesserten mechanischen Leistungsfähigkeiten. Neuartige Ti-basierte dendritische nano-/ultrafeine Komposite (Ti-basierte DNUS Komposite) besitzen eine vorteilhafte Kombination von hoher Druckfestigkeit mit großer plastischer Verformbarkeit unter Druckbelastung bereits im Gusszustand [1,2] wodurch sie als hochleistungsfähige Werkstoffe angesehen werden. Jedoch besitzen diese Ti-basierte DNUS Komposite heufig eine stark verringerte oder gar keine Duktilität unter Zugbelastung [3]. Deswegen ist es das Ziel dieser Forschungsarbeit neue hochfeste Ti-basierte DNUS Komposite mit ausgeprägter Duktilität unter Zugbelastung zu entwickeln und die mechanischen Eingeschaften mit ihrer Mikrostruktur zu korrelieren. Um dieses Ziel zu erreichen wurde die hochfeste Legierung Ti66Nb13Cu8Ni6.8Al6.2 (at.%) [4], die eine große plastische Verformbarkeit unter Druckbelastung aufweist, ausgewählt. Die Mikrostruktur von Ti66Nb13Cu8Ni6.8Al6.2 setzt sich aus zwei metallographischen Konstituenten, einschließlich β-Ti Dendriten und einer interdendritischen Komponente, zusammen. Die β-Ti Dendriten sind mit Nb angereichert, weswegen Nb als “dendritisches Element” bezeichnet wird, wohingegen die interdendritische Komponente mit Ni und Cu angereichert ist und deswegen diese als “interdendritische Elemente” bezeichnet werden. Um den Einfluss der “interdendritischen Elemente” (Ni, Cu and Co) auf die Mikrostruktur zu untersuchen wurden Legierungen mit verschiedenen Konzentrationen unterschiedlicher Legierungselemente (Ti-Nb-Cu-Ni-Al, Ti-Nb-Co-Ni-Al, Ti-Nb-Cu-Co-Al and Ti-Nb-Ni(Co)-Al) entwickelt. Es wurde gezeigt, dass eine höhere Konzentration “interdendritischer Elemente” in einer bestimmten Zusammensetzung einem höheren Volumanteil der interdendritischen Komponente entspricht. Zusätzlich wird die Kristallstruktur der interdendritischen Phase sehr stark durch die “interdendritischen Elemente” beeinflusst. Da die meisten hoch entwickelten Anwendungen (z.B. Luftfahrt) gesteigerte spezifische Festigkeiten erforden, wurden die neuen duktilen Ti-Nb-Cu-Ni-Al Legierungen modifiziert um ihre Dichte zu reduzieren, indem Nb durch das leichtere V ersetzt wurde. Als Ergebniss wurde eine neue Familie von Ti-V-Cu-Ni-Al Legierungen, mit im Vergleich zu Ti-Nb-Cu-Ni-Al Legierungen verbesserten spezifischen Festigkeiten, entwickelt. Zusäzlich ist die elastische Formänderungsenergiedichte der neu entwickelten Legierungen höher verglichen mit kommerziellen Ti-basierten Federmaterialien. Der Effekt der Mikrostruktur auf das Verformungsverhalten der Legierungen wurde mittels in-situ mikrostruktureller Analysen verschiedener Verformungszustände im Rasterelektronenmikroskop untersucht. Um ein Einfluss der metallographischen Konstituenten auf die Festigkeit zu bestimmen wurden Mikrohärtekarten erstellt. Unter Verwendung der erhalten empirischen Prinzipen zur Einstellung der Mikrostruktur wurde eine neue Legierung Ti68.8Nb13.6Co6Cu5.1Al6.5 (at.%) mit hoher statischer Zähigkeit (besser als die der kürzlich entwickelten Ti-basierten gläsernen metallischen Kompositlegierungen) entwickelt. Diese hohe statische Zähigkeit wird sowohl durch die hohe Festigkeit als auch durch die ausgeprägte Plastizität unter Zugbelastung verursacht. Um den Einfluss der Mikrostruktur auf die Plastizität unter Zug zu untersuchen wurde Transmissionelektronmikroskopie sowie in-situ mikrostrukturelle Analysen verschiedener Verformungszustände im Rasterelektronmikroskop durchgefühlt
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O'Rourke, Jane. "Microstructure and mechanical properties of fibre-reinforced heat-treatable aluminium alloys". Thesis, University of Bath, 1995. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.261348.
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RODBARI, Reza Jamshidi. "Magnetic and structural properties Al-based alloys obtained by mechanical alloying". Universidade Federal de Pernambuco, 2016. https://repositorio.ufpe.br/handle/123456789/17996.
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The quasicrystalline alloy which contains the element aluminum present dispersion of particles in nanometric scale that exhibit high values of mechanical strength at room temperatures and high temperatures. The quasicrystalline solids have no crystallographic conventional symmetrical structures; but they are constituted by a unit cell with periodic repetition in space and ordination mode, intermediate between periodic phases and crystalline phases amorphous non-crystalline. The process of Mechanical alloying, a technique of powder metallurgy developed in the 60's, it was established as a viable processing method in the solid state to produce various quasicrystalline phases metastable and stable. The interest in obtaining this material is due to its good structural, electronic and magnetic properties, and the interactions between the properties. In general, the quasicrystalline alloy show resistant to friction and wear, good electrical and thermal insulators, are hard, used in photonic sensors and some formations of quasicrystals are good hydrogen storers. In this work, researched he used the Mechanical alloying to obtain the icosahedral and decagonal phases Al65Mn22Cu13 and Al67,6Cr23,3Fe9,1 in order to study the magnetic properties. Samples of quasicrystalline alloys were obtained by high energy milling with balls mass ratio of 20: 1 with rotation of 200rpm, at time intervals ranging from 1 hour to 40 hours a planetary ball mill Pulverisette 5 Frittsch. Evaluations of physical characterizations were made by scanning electron microscopy showed a microstructure with nonuniform and large nodules symmetries. The X-ray diffraction provides information about identification of phases resulting from Al65Mn22Cu13 Al67,6Cr23,3Fe9,1 and alloys, the formation of icosahedral phases, intermetallic and decagonal and the presence of typical diffraction pattern peaks of their crystallographic network. The magnetic measurements were performed as a function of temperature M (T), and also due to the applied field F (M). It can be concluded that the formation of quasicrystalline phases is possible as grinding time and speed for Al65Mn22Cu13 Al67,6Cr23,3Fe9,1 and alloys obtained by Mechanical alloying process.
As ligas quasicristalinas que contém o elemento o alumínio, apresentam dispersão de partículas em escala nanométrica que apresentam valores elevados de resistência mecânica em temperaturas ambientes e em altas temperaturas. Os sólidos quasicristalinos possuem estruturas simetricas não cristalográfica convencional; mas são constituídos por uma célula unitária com repetição periódica no espaço e ordenação, de modo, intermediário entre as fases cristalinas periódicas e as fases não-cristalinas amofas. O processo de mecanossíntese, uma técnica da metalurgia do pó desenvolvida nos anos 60, foi estabelecido como um método viável de processamento no estado sólido para a produção de várias fases quasicristalinas metaestáveis e estáveis. O interesse de obtenção desse material é devido as suas boas propriedades estruturais, eletrônicas e magnéticas, e a interações entre as propriedades. Em geral, as ligas quasicristalinas mostram resistentes á fricção e ao desgaste, bons isolantes elétricos e térmicos, são duros, utilizados em sensores fotônicos e algumas formações de quasicristais são bons armazenadores de hidrogênio. Neste trabalho, pesquisou o usou da mecanossíntese para a obtenção das fases icosaedral e decagonal Al65Mn22Cu13 and Al67,6Cr23,3Fe9,1 com o intuito de estudar as propriedades magnéticas. As amostras das ligas quasicristalinas foram obtidas por moagem de alta energia com razão massa bolas de 20: 1, com rotação de 200 rpm, nos intervalos de tempo que variou de 1 hora até 40 horas em um moinho de bola planetário Frittsch Pulverisette 5. Avaliação das cararterizções físicas foram feitas por microscopia eletrônica de varredura apresentaram uma microestruturas com simetrias não uniforme e nódulos grandes. Adifração de raios-X fornece informações sobre identificações das fases decorrentes das ligas Al65Mn22Cu13 and Al67,6Cr23,3Fe9,1 as formações das fases Icosaedral, decagonal e intermetálicas e a presença de picos padrões de difração típicos da sua rede cristálografica. As medidas magnéticas realizadas foram em função da temperatura M (T), e também em função do campo aplicado M (H). Pode-se concluir que é possível a formação das fases quasicristalinas conforme o tempo de moagem e da velocidade para ligas Al65Mn22Cu13 and Al67,6Cr23,3Fe9,1 obtido pelo processo mecanossíntese.
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Bond, Trevor. "Microstructure and Mechanical Properties of Cold Sprayed Aluminum and Titanium Alloys". Digital WPI, 2019. https://digitalcommons.wpi.edu/etd-theses/1336.
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A combination of experimental and computational methods is used to explore the microstructure and mechanical behavior of cold sprayed 6061 aluminum alloy and Ti-6Al-4V alloy and their substrate materials. A variety of microscopic methods are used for characterization of the microstructure. The indentation size effect and characteristic length of strain gradient plasticity for the substrate materials are determined. An FEA simulation describes the behavior of a worn Berkovich nanoindenter. Stress strain is studied experimentally in the substrate materials for future comparison with bulk cold-sprayed materials. Abaqus FEA models are used to simulate a single particle impact for a particle with an oxide layer using a linear Johnson-Cook plasticity model and a bilinear Johnson-Cook plasticity model. The implications of the results are discussed for cold spray processes.
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Ji, Zongwei. "First-principles study of the mechanical properties of TiAl-based Alloys". Licentiate thesis, KTH, Materialvetenskap, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-220333.
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Gill, Puneet Kamal S. "Assessment of Biodegradable Magnesium Alloys for Enhanced Mechanical and Biocompatible Properties". FIU Digital Commons, 2012. http://digitalcommons.fiu.edu/etd/714.
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Biomaterials have been used for more than a century in the human body to improve body functions and replace damaged tissues. Currently approved and commonly used metallic biomaterials such as, stainless steel, titanium, cobalt chromium and other alloys have been found to have adverse effects leading in some cases, to mechanical failure and rejection of the implant. The physical or chemical nature of the degradation products of some implants initiates an adverse foreign body reaction in the tissue. Some metallic implants remain as permanent fixtures, whereas others such as plates, screws and pins used to secure serious fractures are removed by a second surgical procedure after the tissue has healed sufficiently. However, repeat surgical procedures increase the cost of health care and the possibility of patient morbidity. This study focuses on the development of magnesium based biodegradable alloys/metal matrix composites (MMCs) for orthopedic and cardiovascular applications. The Mg alloys/MMCs possessed good mechanical properties and biocompatible properties. Nine different compositions of Mg alloys/MMCs were manufactured and surface treated. Their degradation behavior, ion leaching, wettability, morphology, cytotoxicity and mechanical properties were determined. Alloying with Zn, Ca, HA and Gd and surface treatment resulted in improved mechanical properties, corrosion resistance, reduced cytotoxicity, lower pH and hydrogen evolution. Anodization resulted in the formation of a distinct oxide layer (thickness 5-10 μm) as compared with that produced on mechanically polished samples (~20-50 nm) under ambient conditions. It is envisaged that the findings of this research will introduce a new class of Mg based biodegradable alloys/MMCs and the emergence of innovative cardiovascular and orthopedic implant devices.
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Blank, Jonathan P. "Effect of boron additions on microstructure & mechanical properties of titanium alloys produced by the Armstrong process". Columbus, Ohio : Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1198718818.
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Dehoff, Ryan R. "Microstructure, Oxidation Behavior And Mechanical Behavior Of Lens Deposited Nb-Ti-Si And Nb-Ti-Si Based Alloys". The Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=osu1221839511.
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Morgan, David Scott. "A microstructural and mechanical analysis of perforation of aluminum alloys". Thesis, Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/16361.
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