Microstructural Evolution in Partially Homogenized AZ91 Alloy during Hot Rolling and Interpass Annealing

Abstract

The as-cast AZ91 Mg alloy ingot with mean grain size of 98 μm after solution treatment was subjected to plastic deformation by multi-pass hot rolling. The process facilitated steady grain refinement by dynamic recrystallization with increasing rolling passes, and the final grain size was reduced to 6.4 μm by 4 rolling passes. Optical microscopy demonstrated that in the beginning of the rolling process twin DRX was the major dynamic recrystallization mechanism. In contrast, in 3rdand 4thpasses of rolling new grains nucleated at grain boundaries, due to low grain size of the alloy.