The Transition Of Dynamic Recrystallzation Mechanisms Of As-cast AZ31 Mg Alloys During Hot Compression

The transition of dynamic recrystallization(DRX)mechanisms of casting AZ31 Mg alloys under hot compression was experimentally and theoretically studied.The switch from the twininduced DRX(TDRX)to the grain boundary bulging DRX(GBBDRX)depends on the local strain accumulation within the grains and the average grain size.Based on the EBSD experimental results and a theoretical transition criterion,two cooperating DRX schemes implemented into the viscoplastic self-consistent crystal plasticity model are proposed and employed to simulate the microstructure activities,texture evolution and stress-strain relationships.The simulation results show:(a)according to the enhancement of basal slip activity and the reduction of the extension twinning activity,the deformation basal texture can be weakened by the twin-walled grains that inherit the c-axis orientation of the parent twins;(b)the TDRX can be replaced by the GBBDRX that can decrease local dislocation density,when the local strain accumulation within refined grains achieves the saturation state of secondary twinning.The dominant GBBDRX mechanism can limit pyramidal slip,decrease the activity of basal slip,and increase prismatic slip,strengthening the basal texture;and(c)the DRX transition switches the decrease of the hardening rate to flow softening.