Research Progress and Future Prospect on New Low-Alloyed Bake-Hardenable Magnesium Alloys

Magnesium alloys are widely used in aerospace, automotive, and rail transit industries as the lightest structural metallic materials. Minor alloying additions have proven to be effective in enhancing processability and ductility. Recent studies demonstrate that low-alloyed Mg-Zn-Ca(-Al) alloys exhibit exceptional room-temperature formability due to their weak texture after rolling and annealing. This advancement indicates that magnesium alloy sheets could potentially replace steel and aluminum alloy in body panel applications. However, achieving improved strength while maintaining formability remains a substantial challenge, limiting the broader adoption of low-alloyed magnesium alloys. Bake hardening (BH) treatment, a technique commonly employed for steel and Al body panels to enhance post-forming strength, has recently been shown to strengthen Mg-Zn-Ca(-Al) alloy sheets. BH treatment partially ad- dresses the trade-off between formability and strength in low-alloyed magnesium alloys by utilizing the limited solid solution atoms. As the development of BH magnesium alloy sheets progresses, further im- provements in properties or the design of new alloy compositions require a thorough understanding of the relationship between microstructure and mechanical properties and the underlying mechanisms. This re- view examines recent advancements in low-alloyed bake-hardenable magnesium alloys, focusing on three mechanisms: dislocation segregation, twin boundary segregation, and Guinier-Preston (GP) zone- induced bake hardening. Additionally, it provides a brief outlook on the future development trends aimed at expanding the application range of these materials. The insights presented here are expected to guide the design and optimization of BH magnesium alloys with enhanced performance and broader industrial applicability.