The dynamic recrystallization and elevated-temperature work hardening behavior of Mg-Y-Sn alloys

Abstract

The dynamic recrystallization (DRX) and elevated-temperature work-hardening behavior of Mg-Y-Sn alloys with various Y contents were investigated. The results demonstrated that the dynamic crystallization behaviors of Mg-6Y-0.5Sn alloy was dominated by continuous DRX, accompanied by discontinuous DRX during hot extrusion. This mechanism contributed to a small proportion of DRXed grains (59 %) and increased coarse unDRXed grains, compared to Mg-2Y-0.5Sn and Mg-5Y-0.5Sn alloys. Correspondingly, the initial work hardening rate of Mg-6Y-0.5Sn alloy was improved by the raised unDRXed grains component with high-density residual dislocations, contributing to strengthening. At 300 °C, high residual strain provided the driving force and weakened texture promoted slip for subsequent DRX occurrence with dislocation annihilation, leading to a decreased 10 % work hardening rate and obvious dynamic softening in Mg-6Y-0.5Sn alloy. The findings are helpful to provide guidance for the development of heat-resistant Mg alloys.