Effect of prior strain on continuous recrystallization in AZ31 magnesium alloy after hot deformation

The effect of prior strain on static recrystallization of hot-deformed magnesium alloy AZ31 was investigated at temperatures of 497, 503 and 513 K by optical and SEM/OIM metallographic observation. Ultrafine grains (UFGs) were evolved by grain fragmentation due to continuous dynamic recrystallization (cDRX) during hot deformation. Irrespective of the different microstructures developed at strains of 0.3 and 1.2, the kinetics of grain coarsening taking place during annealing are very similar, while the deformation texture scarcely changes even at longer times. The grain size changes at both the strains are categorized into three stages: i.e. an incubation for grain growth, a rapid and limited grain growth and then normal grain growth. It is concluded that the annealing process occurring in the regions of UFGs evolved is primarily controlled by grain growth accompanied with static recovery, that is continuous static recrystallization.