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 21 for “"Stacking-fault Energy"”.
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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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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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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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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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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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Dislocation slip and twinning stress in shape memory alloys- theory and experiments
… based ab initio calculations, and the role of energy barrier is characterized. Through different length scales incorporating atomistic simulations into dislocation-based mechanics, an extended Peierls-Nabarro (P-N) model is developed to establish flow stresses in SMAs and the predicted Peierls …
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Chemistry, design, and processing of two-stage TRIP steel
… α</sup><sub>Chem</sub>. A model for the strain energy, ΔG<sup>λ→α</sup><sub>str</sub>, was formulated utilizing the Young’s modulus (E), lattice misfit squared (δ²), and molar volume (Ω) which opposed the chemical driving force for α-martensite formation. The M<sup>α</sup><sub>S</sub> was …
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The Effect of Co on the Deformation Response of Fe-Mn Alloys
… While Co is known to have an effect on the stacking fault energy of alloys, its precise effect on the Fe-Mn system is somewhat less explored. This study seeks to understand what effect Co has on the Fe-Mn system in terms of its effect on thermodynamic properties, phase composition, …
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Atomistic Molecular Dynamics Studies of Grain Boundary Structure and Deformation Response in Metallic Nanostructures
… potentials representing fcc materials with low stacking fault energy. Non-planar grain boundary features promote dislocation as deformation mechanisms, and hinder grain boundary sliding. This dissertation also reports the effects of temperature and strain rate on deformation behavior and …
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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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The influence of nitrogen on the deformation behaviour of a modified AISI type 200 series alloy
… and work hardening to the alloy. The low stacking fault energy (SFE) of this alloy range ensured that cross-slip was significantly inhibited during room temperature deformation and the deformation mode was observed to be planar glide. Nitrogen was shown to increase the SFE of this alloy …
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Recrystallisation in Single Crystal Nickel-Based Superalloys
… Co lowers the y' solvus temperature and the stacking fault energy of y. Ru, Mo and W appear to have no direct effect on recrystallisation. The nucleating grains for recrystallisation form in orientations similar to the deformed matrix, and subsequently twin to form high angle boundaries and …
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Hot forging of the nickel-base superalloy ATI 718Plus
… is commonly found in materials with a low stacking fault energy at low temperatures and/or high strain rates. Initial stages of twinning could be captured and allowed a detailed analysis of the underlying processes. In the $\gamma$-$\eta$ microstructure the deformation characteristics of …
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An advanced perspective on twin growth in nickel-titanium
… phases of NiTi are characterized with barrier energy in this thesis. In addition, energetics of dislocation twin boundary interactions in a face centered cubic (fcc) metal (Copper) that contributes to strengthening is investigated. Density Functional Theory based ab initio calculation and …
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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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Atomistic Insights into Alloy Solidification using Machine-Learning Potentials
… of relevance for mechanical properties, such as stacking-fault energy and phase stability. It is demonstrated that energy accuracy on test sets often does not correlate with accuracy in capturing material properties, which is fundamental in enabling large-scale atomistic simulations of metallic …
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Modeling mechanical properties – linking atomistics to continuum
… compression tests on: (a) single crystals of low stacking fault energy Co-33%Ni alloys, (b) polycrystalline nano-twinned Ni-x%Co alloys (x = 1, 1.62, 2.9 and 5.6), and (c) equiatomic NiTi shape memory alloys. The reason these materials are chosen as candidates for study is that these materials …
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Underlying deformation behavior of medium/high entropy alloys using advanced electron imaging and diffraction
… Their complex chemistries create rich defect energy landscapes and multiple pathways for mechanical deformation, yet the link between local structure and deformation mechanisms remains incompletely resolved in M/HEAs. This thesis investigates the local structure and deformation mechanisms in …
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Critical stresses for twinning, slip and transformation in shape memory alloys: modeling and experiments
… that incorporates the transformation shear energy at an atomic scale in conjunction with the heterogeneous dislocation based martensitic transformation theory to predict transformation stresses. We confirm the validity of our formulations by comparing the data obtained from experiments and …
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