剧烈塑性变形对AZ31镁合金微观组织演化的影响

Effect of Severe Plastic Deformation on the Microstructure Evolution of AZ31 Magnesium Alloys

等截面通道角挤压(equal channel angular extrusion,ECAE)是制备无疏松孔洞大块超细晶材料的重要方法之一。通过刚塑性有限元法对ECAE进行三维数值仿真,采用单元点映射方法,结合三维模型转换进行了A,Ba,Bc和C多次挤压路线的有限元连续仿真,得出了圆形截面挤压试样等效应变分布及其变形均匀性规律,同时,给出了多次挤压不同挤压路线等截面通道角挤压晶粒细化机理。通过变换挤压路线可以改变挤压试样内部微观组织结构。随着挤压次数的增加,不同挤压路线对应挤压试样均得到有效细化,与其它挤压路线相比,路线Bc和C能够得到大角度晶界的等轴晶粒分布的挤压试样。同时,通过实验得到的各路线挤压试样对应的微观结构演化规律与模拟分析得到的应变分布规律一致。

Equal channel angular extrusion （ECAE） process has the capability to prodtice bulk nonstructural materials without loose holes. Using commercial metal forming finite element code, ECAE process was analyzed numerically in the present research. It combined the node reflection method and three-dimensional model switching to realize multi-extrusion process of Routes A, Ba, Bc and C by the finite element method. The distribution of accumulated effective strain and the influence rules of deformation uniformity in round billets were obtained, and the grain refining mechanism of equal channel angular multi-extrusion for different processing routes was given. The results show that changing the extrusion route can alter the microstructure of the workpiece, which can be gradually refined in each route with the number of extrusion increasing. It is found that route Bc and C can get larger angle grain boundaries and more uniform equiaxed grain distribution than other routes. In addition, the microstructure evolutions of different multi-pass ECAE processing routes are consistent with FE analyses.