Corrosion resistant and high-strength dual-phase Mg-Li-Al-Zn alloy by friction stir processing

Magnesium is the lightest structural metal, and alloying with lithium makes it even lighter. However, multi-phase Mg-Li alloys typically undergo rapid corrosion, and their strength decreases at room temperature due to natural age-softening. Here, we engineer a rapidly degrading dual-phase Mg-Li-Al alloy to be durable via friction stir processing followed by liquid CO2 quenching. The best performing alloy has a low electrochemical degradation rate of 0.72 mg·cm−2·day−1, and high specific strength of 209 kN·m·kg−1. We attribute this electrochemical and mechanical durability to its microstructure, which consists of a refined grain size of approximately 2 µm and dense nanoprecipitates. This microstructure suppressed the formation of the detrimental AlLi phase, and an aluminium-rich protective surface layer also formed. This processing route might be useful for designing lightweight and durable engineering alloys.

Zhuoran Zeng, Mengran Zhou, Marco Esmaily, Yuman Zhu, Sanjay Choudhary, James C. Griffith, Jisheng Ma, Yvonne Hora, Yu Chen, Alessio Gullino, Qingyu Shi, Hidetoshi Fujii, Nick Birbilis