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Showing 1 to 16 of 16 for “"Dislocation Loop"”.
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Mechanisms of Ductile Fracture: Void Growth by Dislocation -Loop Emission and Hydrogen-Assisted Crack Propagation
… of hydrogen. First the hydrogen effect on dislocation mobility and lattice dilatation was considered to establish the material constitutive law. Simulations in a unit cell containing a void were carried out to devise traction-separation laws reflecting the hydrogen effect on void growth and …
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Dislocation -Obstacle Interactions in Aluminum Alloys
This thesis examines two types of dislocation-obstacle interactions: dislocation-particle interactions during creep deformation, and dislocation-loop interactions during deformation at room temperature. Dislocation-particle interaction studies in Al-Zn-Mg-Cu-Zr, Al-4Mg-0.3Sc, and Al-0.3Sc showed …
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Lattice Strain Measurements of Deuteride Phase Formation in Epitaxial Niobium on Sapphire
Evidence of significant dislocation formation has been confirmed with high-resolution electron microscopy (HREM) for the 1200A Nb film. The HREM images were used to estimate a dislocation density of 1012 cm-2 after repeated cycling. A residual out-of-plane compressive strain was observed in the …
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Modeling Collective Behavior of Dislocations in Crystalline Materials
A part of this work deals with the kinematics of dislocation density evolution. An explicit Galerkin/least-squares formulation is introduced for the quasilinear evolution equation, which leads to a symmetric and well-conditioned system of equations with constant coefficients, making it attractive …
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Stress-mediated reaction pathways for dislocation nucleation in copper
The ductile behavior of metals requires dislocation nucleation, from either homogeneous or heterogeneous sources, in order to produce the large number of dislocations necessary for extensive plastic deformation. As with the majority of the defect processes that comprise deformation and failure of …
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Microstructural investigations of ion (Kr) irradiated UO2
… increases, defects nucleate and grow into dislocation loops and extended networks with increasing dose. At 600°C some dislocation loops form at high dose, but most of the defects remain small and isolated. The in situ 800°C experiment shows the most dislocation loop nucleation and growth. …
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Computer simulation of defect evolution in lanthanum doped cerium dioxide under irradiation
… vacancy-assisted mechanism. The structure of the dislocation loop observed in TEM images are determined to be the planar interstitial cluster in {111} planes. Also, the loop formation and growth mechanisms are studied by means of both the Frenkel pair evolution simulation and the overlapped …
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Advanced characterization of the early-stage evolution of microstructures and mechanical properties in neutron-irradiated commercial steels
… (EDS), the nucleation, growth and stability of dislocation loops, G phase, α’ phase, and other precipitates were quantitatively analyzed. The irradiation hardening in these two materials were characterized using nanoindentation technique. The hardening behaviors were carefully analyzed against …
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Relationship between flow stress recovery and dislocation structure in polycrystalline alpha-titanium
… 6 hours and (2) a leveling off after 6 hours. Dislocation structure was studied by using transmission electron microscopy. During the first stage of recovery, significant rearrangement of dislocations took place. At this stage fairly regular dislocation loops appeared to surround the subgrains. …
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Integration of GaAsP alloys on SiGe virtual substrates for Si-based dual-junction solar cells
… the GaAsP/SiGe heterovalent interface to prevent dislocation loop nucleation and expansion. We were able to attain GaAsP films on Si with a threading dislocation density as low as 1.2x10⁶/cm² . Our GaAsP/SiGe heterovalent interface research advanced the understanding of such structures. We …
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Modeling of Effect of Alloying Elements on Radiation Damage in Metallic Alloys
… Fe-based alloys, including defect production and dislocation loop transformations, and their connections with defect thermodynamics. First, effects of alloying elements on the primary damage in three Fe-based ferritic alloy systems were studied, with a particular focus on the production behaviors …
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Thermally activated dislocation motion including inertial effects in solid solutions
Dislocation motion through an array of obstacles is considered in terms of the potential energy of the dislocation as it moves through the array. The obstacles form a series of potential wells and barriers which can trap the dislocations. The effect of thermal fluctuations and of a viscous drag on …
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Role of nitrogen in the structure and properties of proton irradiated 12Cr1MoWV ferritic/martensitic steel for advanced nuclear reactor cores, The
… that, as N content increases, the average dislocation loop diameter decreases, while the number density of loops increases, a behavior consistent with a reduction in self-interstitial atom (SIA) cluster mobility. Additionally, STEM energy dispersive spectroscopy finds extensive Ni …
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Silicon Carbide - Nanostructured Ferritic Alloy Composites for Nuclear Applications
… and 450oC temperatures. NFA sample showed heavy dislocation damage at both 300oC and 450oC increasing gradually with dose levels (0-10 dpa). Cr3C2@SiC-NFA showed similar behavior as NFA at 300oC. However, at 450oC, Cr3C2@SiC-NFA showed remarkably low dislocation loop density and loop size as …
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Model for the Kinetics of Cluster Nucleation in Irradiated Materials
Made available in DSpace on 2017-07-06T18:59:34Z (GMT). No. of bitstreams: 3 Yacout_Abdel-Latif_M_MS.pdf: 28279943 bytes, checksum: f6da86eb3369f338673530a80d9bae0b (MD5) Yacout_Abdel-Latif_M_MS_ABS.pdf: 817444 bytes, checksum: e27f0c8a0336b93ffb87d557f779d645 (MD5) license.txt: 4813 bytes, …
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Radiation-induced microstructural and mechanical property modifications in advanced alloys
… 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 defect fluxes results in the elemental …