Work hardening and softening behaviors of Mg-Zn-Gd-Ca alloy regulated by bimodal microstructure

Abstract

The present work mainly focuses on the regulation of the bimodal microstructure (fine recrystallized grains and elongated un-recrystallized grains) on the work hardening and softening behaviors of Mg-6Zn-1Gd-0.3Ca alloy. Meanwhile, the grain refinement mechanism was discussed through EBSD. The results show the work hardening capacity of the alloy increases with improving the volume fraction of fine recrystallized grains, which is mainly due to the increase of dislocation storage rate caused by grain coarsening. The stress reduction (∆P1) value in the early stage of tensile deformation is the biggest for the alloy with fine recrystallized grains of ∼66.8 %, which is attributed to the greater stored energy can provide greater driving force for softeing effect. However, the stress reduction (∆Pi(i=2,3,4)) values of the alloys in the later stage of tensile deformation decrease monotonically with the increase of fine recrystallized grains amount. Moreover, the analysis shows that the fine recrystallized grains of Mg-6Zn-1Gd-0.3Ca alloy are mainly formed by dynamic recrystalliztion (DRX).