Effects of Li Content on Phase Evolution and Mechanical Properties of Mg-xLi-6Zn-1.5Y Alloy

To investigate systematically the phase evolution and mechanical properties of the alloys, the Mg-xLi-6Zn-1.5Y alloys with different matrices were studied from different scales. The results show that the volume fraction of the α-Mg phase is decreased with more Li addition. Moreover, the change of Li content also leads to a change in the morphology and size of primary phases, which has an adverse effect on strength. The as-cast Mg-5Li-6Zn-1.5Y alloy has the highest ultimate tensile strength of 221 MPa. With the Li content increasing to 8 wt.%, the ultimate tensile strength is reduced by 41 MPa, and the elongation reaches the maximum value of 24.1%, which is increased by 13.7%. The decrease in tensile strength is attributed to the fine-grain strengthening effects of different matrices and the weakening of the second phase strengthening effect. In contrast, the increase in elongation is attributed to the change in the morphology and size of the matrix and primary phases.