Achieving extraordinary strength-ductility synergy in Mg-Zn-Zr alloy thin sheet manufactured via load assisted one-step large-strain lowered temperature rolling

Abstract

The Magnesium (Mg) sheet fabrication is extremely challenging due to its poor ductility/formability and manufacturing difficulties requiring multi-pass rolling leading to strength-ductility trade-off. Therefore, the present work is focused on establishing an appropriate manufacturing strategy to develop Mg-Zn-Zr alloy sheets via one-step large-strain lowered temperature rolling (LSLR). By tailoring the underlying microscopic mechanisms viz., shear zone formation along GBs, dislocation twin interaction, formation of dynamically recrystallized (DRXed) grains, and conversion of low angle grain boundaries (LAGBs) to high angle grain boundaries (HAGBs) favourable microstructures were engineered. The combined effect of bimodal grains, weakened bimodal basal texture with simultaneous twin-non basal slip mode deformation mechanisms resulted in extraordinary strength-ductility synergy (∼515 MPa and ∼24%) in the rolled sheet. In addition, a critical processing condition as a function of temperature and strain has been established for the transformation of twin to slip mode of deformation during LSLR. This work provides a new pathway for developing high performance Mg alloy sheets as an alternative structural material for lightweighting applications.