A new method to model dislocation self-climb dominated by core diffusion
A new method to model dislocation self-climb dominated by core diffusion
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DOI：
10.1016/j.jmps.2019.103783
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发表时间：
2020-02
影响因子：
5.3
通讯作者：
Fengxian Liu;A. Cocks;E. Tarleton
中科院分区：
文献类型：
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作者：
Fengxian Liu;A. Cocks;E. Tarleton
位错核心区原子的迁移速度比周围晶格快许多个数量级。这种原子沿位错核的快速传递在许多材料过程的动力学中起着重要的作用，包括低温蠕变和辐照后退火。本文提出了位错芯扩散过程的有限元分析方法；基于变分原理的微观组织演化。在基于节点的三维离散位错动力学框架中，结合有限元核心扩散公式，建立了位错自爬升模型。简要回顾了bcc铁中孤立回路的行为，并将模拟扩展到包括自爬升加滑行机构的平行和非平行回路的粗化过程，其中爬升和滑行之间的巨大时间尺度分离通过自适应时间步进方案进行桥接。数值模拟结果与刚性棱柱环的理论解与已发表的实验结果吻合良好。模拟了一群环的粗化过程，以研究bcc材料中累积相互作用和大规模图案化的机制。
The mobility of atoms in dislocation core regions is many orders of magnitude faster than in the surrounding lattice. This rapid atomic transport along dislocation cores plays a significant role in the kinetics of many material processes, including low-temperature creep and post-irradiation annealing. In the present work, a finite element based analysis of the dislocation core diffusion process is presented; based on a variational principle for the evolution of microstructure. A dislocation self-climb model is then developed by incorporating this finite element core diffusion formulation within the nodal based three-dimensional discrete dislocation dynamics framework. The behaviour of an isolated loop in bcc iron is briefly reviewed, and simulations are extended to include the loop coarsening processes of both parallel and non-parallel loops by self-climb plus glide mechanisms, in which the huge time scale separation between climb and glide is bridged by an adaptive time stepping scheme. Excellent agreement is obtained between the numerical simulation, the theoretical solution of rigid prismatic loops and published experimental results. The coarsening process of a population of loops is simulated to investigate the mechanisms of the accumulative interactions and large-scale-patterning in bcc materials.