npj：倪勇相场模型——预测位错独特相互作用

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相交位错之间的长程弹性相互作用和短程芯结构反应，对理解晶态固体中基于位错的应变硬化机制来说至关重要。相场模型通过连续统细观弹性理论来描述弹性相互作用，并将γ-表面结合到晶体能中，以使位错芯结构反应成为可能，因而在位错动力学建模中显示出巨大的潜力。由于以前的相场模型中晶体能近似表示为各滑移平面的层间势的线性叠加，所以它不能完全描述相交滑移平面中滑移位错之间的反应。

中国科学技术大学倪勇教授团队对相场模拟中的晶体能项作了改进，以便在立方金属的相交滑移面模拟中加入滑移位错间相互作用。他们通过耦合两个相交平面的层间势来更新晶体能，提出了一种改进的位错相交的相场模型，将其应用于共线相互作用研究，并与之前采用离散位错动力学模拟的结果进行比较。在新的模拟中，晶体能修改后成功地描述了应变硬化中最强的位错相互作用：共线相互作用过程中的位错湮灭现象。这种位错湮灭只有在改进的相场模型中被预测到。改进后的相场建模方法可以更好地预测金属晶体的位错相互作用和塑性流动。该文近期发表于npj Computational Materials 4: 20 (2018);  doi:10.1038/s41524-018-0075-x。英文标题与摘要如下，点击阅读原文可以自由获取论文PDF。

Improved phase field model of dislocation intersections

Songlin Zheng, Dongchang Zheng,

 Yong Ni & Linghui He

Revealing the long-range elastic interaction and short-range core reaction between intersecting dislocations is crucial to the understanding of dislocation-based strain hardening mechanisms in crystalline solids. Phase field model has shown great potential in modeling dislocation dynamics by both employing the continuum microelasticity theory to describe the elastic interactions and incorporating the γ-surface into the crystalline energy to enable the core reactions. Since the crystalline energy is approximately formulated by linear superposition of interplanar potential of each slip plane in the previous phase field model, it does not fully account for the reactions between dislocations gliding in intersecting slip planes. In this study, an improved phase field model of dislocation intersections is proposed through updating the crystalline energy by coupling the potential of two intersecting planes, and then applied to study the collinear interaction followed by comparison with the previous simulation result using discrete dislocation dynamics. Collinear annihilation captured only in the improved phase field model is found to strongly affect the junction formation and plastic flow in multislip systems. The results indicate that the improvement is essential for phase field model of dislocation intersections.   

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