7050铝合金内部沿晶微裂纹热塑性修复的元胞自动机模拟

摘要

According to experimental data of 7050 aluminum alloy in single­pass hot compression, the relevant parameters of cellular automaton (CA) model for microcrack healing were identified and calculated. Using Microsoft Visual C++platform, the CA rules of microstructural evolution of intergranular microcrack during thermoplastic healing include topological deformation mechanism, the dislocation density evolution mechanisms and dynamic recrystallization kinetics mechanism were programmed. For the different characteristics of crack surface and grain boundary, the crack surface energy and grain boundary energy drive the growth of grain in different ways and the mechanism was proposed in the recrystallization process. The CA simulation results show that the hot thermoplastic deformation and dynamic recrystallization can repair microcracks completely under certain conditions, and the piecewise healing characteristics during crack healing process have a good agreement with the experimental results, but the appearance of crack healing depends on the crack morphology, crack nucleation rate and nucleation site, the growth direction and speed of new grain.%根据7050铝合金单道次热压缩变形实验数据，对建立微裂纹修复的元胞自动机(CA)模型所需相关参数进行辨识和计算。利用Microsoft Visual C++平台编制了包含拓扑变形机制、位错密度演变机制、动态再结晶动力学机制的沿晶微裂纹热塑性修复的微观组织CA演化规则。针对裂纹表面和母相晶界的不同特征，提出再结晶过程中表面能和晶界能驱动下不同的晶粒长大方式。CA 模拟结果表明：一定条件下的热塑性变形和动态再结晶可完全修复材料内部微裂纹，且裂纹愈合过程中出现的分段愈合特征与实验结果相吻合，但裂纹愈合的形貌演化取决于裂纹形态、裂纹表面形核率和形核位置、新晶粒长大方向与速度。