Isochronal annealing behaviors of magnesium alloy AZ31 after hot deformation

Isochronal annealing behaviors of magnesium alloy AZ31 were studied at temperatures of 373 to 673 K by optical and SEM/ EBSD metallographic observation. The alloy had fine-grained structures developed by continuous dynamic recrystallization (cDRX) after hot deformation at 573 K. Temperature dependence of the average grain size (D) is categorized into three temperature regions, i.e. (a) incubation period of grain growth at < 450 K, (b) rapid grain coarsening at 473-523 K, and (c) normal grain growth at T>550 K. The number of fine grains per unit area, however, is reduced remarkably even in region 1. It is concluded, therefore, that grain growth takes place continuously in the whole regions. While, deformation texture scarcely changes even after annealing at high temperatures. It is concluded that the annealing processes operating in the magnesium alloy with cDRX grain structures is mainly controlled by grain growth accompanied with recovery, that is continuous static recrystallization (cSRX).