Strengthening of Mg-Li alloy dominated by continuously hardened Mg phase during room temperature rolling

Abstract

The process of room temperature rolling is a straightforward and efficient method for producing high strength Mg-Li alloys, but the underlying strengthening mechanism remains unclear. In this study, we successfully enhanced the tensile properties of a novel dual-phase Mg-Li alloy through room temperature rolling, with a remarkable yield strength of 201 MPa and an elongation-to-failure of 14 %. Microhardness testing was conducted to evaluate the contribution of the Mg- and Li- phases to the improvement in strength. The results demonstrate that the hardness of Mg-phase reaches 60 HV, which is significantly higher than the 49 HV observed in Li-phase, indicating that the Mg-phase after rolling plays a pivotal role in enhancing material strength. The presence of a high density of dislocations stored in the Mg-phase emerges as the dominant factor contributing to improved strength in Mg-Li alloys. In-situ compression testing reveals that 〈c + a〉 slip activation and twinning-induced slip serve as internal mechanisms for continuous deformation and hardening within the Mg-phase. Despite numerous precipitated Mg-phase particles within the Li-phase matrix, the hardness analysis reveals minimal strain-induced phase transformation effects on the overall strength of the Al-free and Zn-free Mg-Li alloy. These findings provide valuable insights for designing and fabricating high-strength dual-phase Mg-Li alloys.