Microstructural evolution and its influence on mechanical and corrosion behaviors in a high-Al/Zn containing duplex Mg-Li alloy after friction stir processing

Ultralight Mg-Li alloys offer promising applications across various fields. Mg-Li alloys enriched with Al and Zn hold theoretical potential for achieving excellent mechanical strength and corrosion resistance. However, the structural and performance characteristics of such Mg-Li alloys, particularly after thermomechanical processing, remain inadequately explored and understood. This study investigated the microstructural evolution of a Mg-9Li-5Al-4Zn alloy after friction stir processing and its consequent effects on the mechanical and corrosion performance. The grain size of the alloy was effectively refined and stabilized during friction stir processing at various heat inputs. The yield strength of the alloy increased by 86.4% after friction stir processing under the highest heat input condition, which was attributed to fine grain strengthening, solid solution strengthening and dispersion strengthening. Concurrently, the alloy experienced a slight decrease in elongation after the friction stir processing. The alloy subjected to friction stir processing with the highest heat input exhibited a minimal corrosion current density of 6.10 x 10-6 A/cm2 , which was only 25% of the base metal. The enhanced anti-corrosion properties can be attributed to the dispersion and distribution of precipitated particles induced by friction stir processing, which hindered the micro-galvanic corrosion and promoted the generation of a compact surface film, leading to minimal and uniform corrosion. This investigation can be significant for understanding the metallurgical mechanisms and performance evolution of Mg-Li alloys during thermomechanical processes. (c) 2023 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.