镁合金AZ31动态再结晶行为的取向成像分析

Analysis on behavior of dynamic recrystallization in magnesium alloy AZ31 by orientation mapping

利用背散射电子衍射(EBSD)取向成像技术分析了具有不同初始织构的镁合金AZ31 动态再结晶晶粒的取向特征以及与相邻的形变晶粒的取向关系.结果表明:不同初始织构以 及不同应变量下动态再结晶新晶粒与形变晶粒的取向都相近,说明动态再结晶以连续方式进 行,即亚晶转动方式.随形变量的增加,不同初始织构试样的晶粒都转向基面取向,但菊池带 衬度图像显示大的形变晶粒内部很少有亚晶界存在并且菊池带质量高,说明塑性滑移机制仍 在起很大作用但在靠近晶界处发生,形变晶粒是通过平行于压缩面方向剪切晶界而逐渐消失 的.动态再结晶晶粒与相邻形变晶粒的取向差表明不同初始织构造成不同的取向差,但总的 趋势是相同的.

Orientation mapping based on EBSD technique is applied to reveal the orientation features of dynamic recrystallized grains and their neighboring matrix in a magnesium alloy AZ31 with different initial textures. The results show that, irrespective of initial texture and strain amount, new grains are similarly orientated to their neighboring matrix, illustrating a dynamic recrystallization through progressive subgrain rotation. In addition, the new grains gradually rotate to basal orientation in different samples, which indicates an important role of plastic slip during dynamic recrystallization in stead of superplastic deformation. The less subgrain boundaries in deformed grains under heavy strain were observed and these deformed grains have high quality of Kikuchi bands, which indicates that the deformed grains are consumed by the shear stress of grain boundaries parallel to the compression plane, rather than non-basal slip. The misorientation between the new and the deformed grains are measured and discussed in terms of the influence of initial texture.