变形晶粒三叉晶界迁移过程的晶体相场模拟

【目的】研究纳米多晶材料受力变形过程中微观结构(如内部晶界,位错等)的演化过程,揭示纳米多晶材料受应力作用的微观机理。【方法】通过晶体相场(Phase field crystal,PFC)模型,模拟多晶样品在外加应力作用下的变形过程,分析内部畸变能的变化情况。【结果】在外加双轴动态加载作用下,当应变较小时,样品中的晶粒没有发生较大的变形,以位错沿着晶界运动为主。随着应变的增加,样品开始出现晶粒旋转、晶粒吞并、大小角晶界迁移运动、三叉晶界发射和接收位错等现象。晶界释放位错有助于减少晶界表面能;吸收位错则增加了晶界表面能。【结论】晶体相场方法可以有效模拟多晶体材料塑性变形过程的微观结构演化。

Phase Field Crystal Simulation of Trigrain Boundary Migatation of Deformed Grain

Objective] The evolution process of microstructure (such as the internal grain boundaries, dislocations, etc.) during the stress deformation of nanometer polycrystalline materials was studied to reveal the microscopic mechanism of the stress caused by nanometer polycrystalline materials.Methods] The deformation process of polycrystalline samples under external stress was simulated by the phase field crystal (PFC) model and the change of internal distortion energy was analyzed.Results] Under the effect of adding two-axis dynamic loading, the grain in the sample did not undergo large deformation at early stages, and the dislocation was mainly along the grain boundary. With the increase of strain, the samples began to appear the phenomena of the grain rotation, grain swallowing, large-angle angular grain boundary migration, the dislocation in triple junction was emitted and absorbed. Dislocation at the grain boundary helped to reduce the surface energy of the grain boundary. Absorption dislocation increased the surface energy of the grain boundary.Conclusion] The phase field crystal method could effectively simulate the plastic deformation process of polycrystalline materials.