Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 51 for “"stacking fault"”.
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Hydrogen Effects on Crystal Dislocations and Stacking-Fault Energy
… Finally, the effect of hydrogen on the stacking-fault energy of an austenitic stainless steel is presented. Measurements done on dislocation nodes reveal a reduction of approximately 19% when comparing the stacking fault energies in vacuum and 40 torr of hydrogen.
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The Effect of Local Conditions on Deformation Processes in Low Stacking -Fault Energy FCC Alloys
The nucleation and propagation of deformation twins has been examined in samples of a nitrogen-strengthened austenitic steel alloy deformed at room temperature under quasi-static and high strain rate compression. Post-mortem analysis of the deformed microstructures at different levels of applied …
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X-ray study of the stacking fault density near the hardness maximum of the Au-Ag-Pd system
… hardness map. In addition, lattice parameters, stacking fault densities, and spacing change fractions have been determined for those alloys. The lattice parameters were found to deviate negatively from Vegard's Law. For the alloys studied, the maximum deviation of 0.0091 A occurred at 20 weight …
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Investigating Dislocation Behavior in High Entropy Alloys Using Atomistic Simulations
… compared to conventional alloys. Its negative stacking fault energy and high yield strength allows unique dislocation behavior. Also, the annealing temperature of NiCoCr system leads to a wide range of short range orders which directly affect the energy barrier of dislocation movement.[22] This …
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Primary creep of polycrystalline copper and determination of the activation volume
… in terms of the dislocation density and the stacking fault width.
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Development of advanced numerical algorithms for kinetic and dynamic simulations of irradiated systems : kinetic Monte Carmelo and dislocation dynamics
… simulate plastic processes in crystals with low stacking fault energy where perfect dislocations split into partials, leaving a stacking fault between them. The algorithm has been applied to fcc systems. The model explicitly accounts for all slip systems and Burgers vectors observed in fcc …
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An evaluation of grain boundary engineering technology and processing scale-up
… boundary engineering is the manipulation of low stacking-fault energy, face- centered cubic material microstructures to break the connectivity of the general grain boundary network through the addition of special grain boundaries. Grain boundary engineering processing consists of thermomechanical …
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Mechanism for Gamma-Precipitation in Aluminum-Silver Alloys and Self-Assembly of Polyelectrolytes: Modeling of Complex Layered Materials
In fcc Al, stacking fault energy (SFE) is high at ∼150 mJ/m 2, inhibiting stacking fault (SF) formation and dislocation motion. Yet hcp precipitates form rapidly in Al-rich face centered cubic (fcc) Al-Ag, even as the energy difference DeltaEhcp-fcc between hcp and fcc solid solution increases …
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Understanding the Yield Behaviour of Single Crystal Ni-based Superalloys
… in the γ channels are able to climb, and stacking fault shear of the precipitates becomes much more prevalent. Upon changing the strain rate of the tensile tests, deformation mechanisms akin to creep were observed which was associated with a drop in the stress. The stress drop is …
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Structural Characterisation of Heteroepitaxial Zincblende Gallium Nitride
… zincblende GaN lattice. Defects, including stacking faults and dislocations, are found to relax the heteroepitaxial zincblende GaN film in both nucleation layers and epilayers. Miscut of the 3C-SiC/Si substrate, used to avoid the formation of antiphase domains, results in the preferential …
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Investigation of the mechanical properties and phase stability of Ti-transition metal alloys using first-principle calculations
… Young’s modulus, higher Pugh’s ratio, and lower stacking fault energies compared to TiB, we compute the mechanical properties of monoborides with different compositions (X11−xX2x)B using density functional theory. Among all (X10.5X20.5)B, we find that mixed (Ti0.5Mo0.5)B and mixed (Ti0.5V0.5)B as …
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Synthesis and characterization of nanocrystalline alloys in the binary Ni-Co system/
… to refine the grain structure. Owing to the low stacking fault energy of Co, many of the alloy deposits exhibited a large density of nanoscale twins. The unique dual-scale grain and nano-twin structure found here caused apparent discrepancies in the grain size measured by XRD and by other …
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Grain boundaries and creep deformation mechanisms in a high performance nickel-based superalloy
… on the testing temperature. Dislocation and stacking fault formation are the main mechanisms at 700°C. or below, whereas perfect dislocations glide and bypass of secondary γˈ particles is predominant at 800°C. However, deformation always initiated at grain boundaries independently from the …
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Investigating the Effect of Austenite Grain Size and Grain Boundary Character on Deformation Twinning Behavior in A High-Manganese TWIP Steel: A TEM In-Situ Deformation Study
… contrast reversal associated with a sequential stacking faults emission from Σ3{111} boundary was observed by in-situ transmission electron microscopy (TEM) deformation experiments, proving the successive layer-by-layer stacking fault emission was the deformation twin nucleation mechanism. The …
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Shear-induced homogeneous deformation twinning in FCC aluminum and copper via automistic simulation
… Calculations of the multiplane generalized stacking fault energy in both materials reveal that aluminum has a longer range of atomic interaction than copper. Using molecular dynamics and static energy calculations, deformation twins are shown to form by homogeneous nucleation, slip and …
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Overcoming the limits of strain-induced martensitic transformation in metastable face-centered cubic alloys
… transformation, a plastic deformation-driven stacking fault formation concept is also assessed, which contributes to latent strain hardening while mitigating the formation of blocky HCP-martensite. Future suggestions for metastable alloy design are also proposed based on the current …
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Monolithic heteroepitaxial integration of III-V semiconductor lasers on Si substrates
… chosen V/III gas flow ratio yields high-quality, stacking fault-free GaAs films on Ge/GeSi/Si substrates, but also encourages the vapor-phase transport of Ge from the substrate into the active regions of integrated GaAs devices. A new two-step GaAs nucleation process was developed that enabled the …
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Dislocation slip and twinning stress in shape memory alloys- theory and experiments
… L21. The results show that the unstable stacking fault energy barriers for slip by far exceeded the transformation transition state barrier permitting transformation to occur with little irreversibility. This explains the experimentally observed low martensitic transformation stress and …
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Strength and ductility of Mg alloys from first-principles
… these cores based on solute interactions with stacking faults and strain. We show that the calculated misfit parameters are highly correlated so that only a few parameters are necessary to describe solute interactions in the dislocation cores. The geometric solute interaction models are …
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