Enhancing high-temperature mechanical performance of Mg-Gd-Y alloys via multi-pass cold rolling induced deformation twins

Improving the high-temperature mechanical performance of Mg–RE alloys without increasing rare-earth content remains a critical challenge. In this study, the effect of preset deformation twins on the high-temperature strength of Mg–8.5Gd–3Y–0.5Zr (wt%) and Mg–8.5Gd–3Y–2Cu–0.5Zr (wt%) alloys was investigated. Preset twins and twin networks were introduced via multi-pass cold rolling at room temperature, followed by tensile testing at 300 °C. The results show that the tensile strength of the Mg–8.5Gd–3Y–0.5Zr alloy at 300 °C was significantly improved from 139 MPa to 227 MPa, representing an increase of 63 %. Microstructural analysis revealed that the twins serve as thermally stable interfaces that effectively impede dislocation motion and promote complex interactions among dislocations, stacking faults, and twins. This interaction enhances the work-hardening capability and thus contributes to strength improvement at elevated temperatures. The strengthening effect of preset twins was further validated in the LPSO-containing Mg–8.5Gd–3Y–2Cu–0.5Zr (wt%) alloy, in which the tensile strength increased by 74 MPa, reaching a high level of 256 MPa at 300 °C. These findings demonstrate that twin engineering provides an effective microstructural strategy to improve the thermal performance of Mg–RE alloys without altering their composition.