Effect of variable thickness cross rolling on edge crack and microstructure gradient of AZ31 magnesium alloy

变厚度交叉轧制对AZ31镁合金边裂和组织梯度的影响

The hot rolling experiment of AZ31 magnesium alloy was carried out by laying anoverlay mold at the initial temperature of 400℃.According to the Mizushima automatic plan view pattern control system(MAS)rolling theory and the cross rolling process,different reductions in the middle and edges of the magnesium alloy were realized,and the influence of the regional controlled reduction rolling on the edge cracks and microstructure gradient of the magnesium alloy were analyzed.It is shown that this rolling approach has reduced the maximum edge crack depth of the rolled piece by 56.85%,and there is a weakening tendency in the base surface texture of the strip edge,the base surface texture density drops from 23.97 to 17.48 after ordinary flat rolling.It exhibits basal texture gradients from the edge to the middle of the sheet along the RD direction,which reflected the uneven deformation of the sheets.It is suitable for the processing of metal molds that require large edge reductions such as mobile phone shells,and provided a theoretical basis for the variable thickness rolling of the magnesium alloy strip.

在400℃初始温度下,将AZ31镁合金置于衬板模具上进行热轧实验。根据MAS轧制理论和交叉轧制工艺,实现镁合金边部和中部区域的不同压下量轧制,分析分区域控制压下率轧制对镁合金边裂和组织梯度的影响。结果表明,这种轧制方法使轧件的最大边缘裂纹深度减小了56.85%,并且板带边部的基面织构呈现弱化的趋势,其基面织构强度从普通平轧时的23.97下降到17.48。沿RD方向从板带边部到中部呈现出一定的组织梯度,反映了轧板的不均匀变形。这种轧制方法适用于如手机壳等需要进行边部大压下量的金属模具的加工过程,并为镁合金板带的变厚度轧制过程提供了理论依据。