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Showing 1 to 13 of 13 for “"dislocation structure"”.
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TEM study of dislocation structure in grain boundaries in metals
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1985.
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Relationship between flow stress recovery and dislocation structure in polycrystalline alpha-titanium
Cell structure was observed in polycrystalline alpha-titanium deformed up to 10% true strain at room temperature. These cells appeared to be slightly elongated rather than equiaxed. The cell boundaries were identified to be the {101̄0} type planes. Flow stress recovery of alpha titanium at 500 and …
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A study of dislocation structures in bulk-strained and in situ TEM strained nickel aluminide alloys
… the research work presented in this thesis, the dislocation structures in bulk strained and in situ TEM strained alloys of hypo-stoichiometric Ni$\sb3$Al with and without boron, and hyper-stoichiometric Ni$\sb3$Al with boron have been studied. Bulk samples were deformed in tension to 3% and 9% …
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Microstructure evolution in Alloy 709 at 550 and 650 °C
… after thermal aging at 550°C and 650°C. The microstructure is characterized using variety of techniques. The alloy shows excellent thermal stability at its working temperature 550°C, while its microstructure evolves rapidly at 650°C with complex precipitation behaviors. NbX particles are of large …
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Growth and characterization of high quality relaxed graded silicon germanium layers for integrated photodetectors
… a high surface roughness, (ii) the formation of dislocation pile-ups, (iii) an increase in the threading dislocation density, (iv) tensile strains and micro-cracking due to thermal mismatch, and (v) particulate contamination from germane gas phase nucleation. We have grown relaxed graded SiGe/Si …
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The microstructural evolution of fatigue cracks in FCC metals
… compared the measured strain to the microstructure. Overall, the strain measured via DIC and EBSD was only weakly correlated to the density of planar slip bands in the microstructure. The second set of experiments concerned the dislocation structure around crack tips. This set of …
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On the plastic deformation behaviour of nickel-based superalloys: low cycle fatigue and stress orientation effects
… in nickel-based superalloys, with a focus on dislocation mechanisms and the effect of microstructure. The two main topics treated are the evolution of the dislocation structure during low cycle fatigue and the effect of loading orientation on the propagation of stacking faults. A series of …
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Dislocation slip and twinning stress in shape memory alloys- theory and experiments
… Precisely determining Peierls stress in dislocation slip and critical twin nucleation stress in twinning is essential to facilitate the design of new transforming alloys. This thesis presents an advanced energetic approach to investigate the attributes of phase transformation, slip and …
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Aspects of serrated flow in aluminium alloys
… in the case of 6061, were also tested. Microstructures of materials were varied by prior heat treatments but, for comparison, all materials, were initially tested in the solution treated and quenched condition. Mechanical testing was undertaken at room temperature throughout the course of the …
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Structural Evolution in the Dynamic Plasticity of FCC Metals
… contribution. Chapter 2 outlines the basics of dislocation plasticity, based on the seminal works of Taylor and Orowan. It then progresses on to discuss recent experimental and theoretical work on the understanding of slip as avalanche behaviour. Chapter 3 summarises traditional modelling …
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Constitutive modelling of the strain hardening behaviour of metastable AISI 301LN austenitic stainless steel as a function of strain and temperature
… which is related not only to the generation of a dislocation structure but transformation and twinning hardening as well depending on the deformation temperature. Strain hardening curves were derived at different temperatures and were found to be following the same basic mathematical equation for …
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Radiation-induced microstructural and mechanical property modifications in advanced alloys
… into thermodynamic nonequilibrium and the microstructure can be modified in many ways: dislocation loops are formed due to the aggregation of self-interstitial atoms (SIA), the accumulation of vacancies leads to the nucleation of voids, preferential coupling between alloying elements and the …
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Zyklische Plastizität von mikro- und submikrokristallinem Nickel
Im Rahmen der vorliegenden Arbeit wurde der Einfluss der Korngröße und der Gefügestabilität auf die zyklische Plastizität von mikro- und submikrokristallinem Nickel, hergestellt durch ECAP und PED, untersucht. Zur Gefügecharakterisierung kamen verschiedene elektronenmikroskopische und …