Effect of Li Addition on the Microstructure and Mechanical Properties of AZ31 Based Alloy

Effects of Li addition on the microstructure and mechanical properties of as-cast and as-extruded AZ31-xLi alloys were investigated. AZ31 alloys with different Li addition(0, 2, 5, 8 and 11 wt%) were cast under atmosphere at 720 ℃ and extruded at 200 ℃. Li addition to AZ31 resulted in the formation of AlLi and MgLi₂Al intermetallic compounds and random texture. With increasing Li addition from 5 to 8 and 11 wt%, ultimate tensile strength was decreased from 264 to 232 and 193 MPa. On the other hand, the elongation was improved remarkably from 15.6% to 14.2% and 38.6% at room temperature due to the transformation from HCP to BCC crystal structure and a weaker basal texture. With increasing Li addition from 5 to 8 and 11 wt%, compression yield strength was increased from 156 to 193 and 178 MPa. MgLi₂Al intermetallic compounds played a significant role for the increase of the mechanical properties.