Reducing the yield asymmetry in Mg-5Li-3Al-2Zn alloy by hot-extrusion and multi-pass rolling

Abstract

Reducing the yield asymmetry is very important concern for wrought Mg-Li alloys. In this study, Mg-5Li-3Al-2 Zn (LAZ532) alloy was successfully produced by hot-extrusion followed by multi-pass rolling at 573 K. Microstructure evolution, mechanical properties and yield asymmetry reducing of LAZ532 alloys at different rolling passes were studied. By observing microstructure using transmission electron microscopy showed that a small amount of ultra-fine AlMg4Zn11 and nano Li3Al2 phases existed in the alloy. With the increasing of rolling passes, the grains of the alloys were obviously refined, and comprehensive mechanical properties were dramatically improved. Meanwhile, it also showed an excellent tension and compression yield symmetry (TYS/CYS was about 1). The results showed that the combined action of the weak {0001} basal lamellar texture, grain refinement and addition of Li element could effectively improve the yield symmetry. Furthermore, based on theoretical analysis, the yield strength in the alloys mainly depended on the strengthening contributions of LAGBs and HAGBs, and strengthening effect of HAGBs most (∼50%) to the yield strength improvement.

Keywords

• Mg-Li alloy
• Tension and compression yield asymmetry
• Dynamically recrystallized
• Texture evolution