排序方式: 共有36条查询结果,搜索用时 78 毫秒
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Dislocation-pairing transitions in hot grain boundaries 总被引:1,自引:0,他引:1
We report the finding of a novel grain-boundary structural phase transition in both molecular-dynamics and phase-field-crystal simulations of classical models of bcc Fe. This transition is characterized by pairing of individual dislocations with mixed screw and edge components. We demonstrate that this type of transition is driven by a combination of factors including elastic softening, core interaction, and core disordering. At high homologous temperatures the occurrence of this transition is shown to prevent premelting at misorientation angles where it would otherwise be expected. 相似文献
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In dendritic solidification, growth morphologies often display a pronounced sensitivity to small changes in composition. To gain insight into the origins of this phenomenon, we undertake an atomistic calculation of the magnitude and anisotropy of the crystal-melt interfacial free energy in a model alloy system featuring no atomic size mismatch and relatively ideal solution thermodynamics. By comparing the results of these calculations with predictions from recent phase-field calculations, we demonstrate that alloying gives rise to changes in free-energy anisotropies that are substantial on the scale required to induce changes in growth orientations. 相似文献
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Although the properties of crystal-melt interfaces have been extensively studied in pure materials, effects of alloying on the interfacial free energy remain relatively poorly understood. In this work we make use of Monte Carlo computer simulations for model binary Lennard-Jones alloys to explore the effects which variations in atomic-size mismatch and the chemical contributions to mixing energies have upon density and composition profiles, as well as the resulting magnitudes of equilibrium adsorption coefficients in concentrated alloys. We study four different model systems covering a range of chemical and size mismatch, finding relatively small adsorption values which are nevertheless statistically different from zero. 相似文献
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C.L. Foiles 《Solid State Communications》1985,53(6):533-536
Electron energy loss data are reported for metallic glasses Fe0.92Zr0.08 and Ni0.5Zr0.5. These data document the sensitivity of the spectra to sample thickness and suggest studies of metallic glasses require samples that are nearly an order of magnitude “thinner” than crystalline alloys. Each electron energy loss spectrum has a dominant loss near 23–25 eV which is similar to the loss function of the pure 3-d metal. This lack of a shift in the location of the dominant loss challenges any simple model of plasmon behavior. The M23 core losses are visible in the “thinner” samples and, in agreement with earlier studies on metal-metalloid glasses, no measureable chemical shift is observed. 相似文献
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Geoffrey H. Campbell Jürgen M. Plitzko Wayne E. King Stephen M. Foiles Christian Kisielowski Gerd J.M. Duscher 《Interface Science》2004,12(2-3):165-174
New insight into the atomic segregation of copper to an aluminum grain boundary has been obtained using multiple, complementary atomic resolution electron microscopy techniques coupled with ab-initio electronic structure calculations. The copper segregation is site specific and changes the structure of the boundary by occupying interstitial sites. Minor elemental constituents in materials can have profound effects on their engineering performance. This change in structure can be associated with these strong effects. The observed structural change will alter the mass transport behavior of the boundary and has implications for the understanding of electromigration mechanisms. 相似文献
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