Effect of Quasicrystal I-Phase on Microstructure and Mechanical Properties of Hot-Rolled Diphasic Mg-8 wt.% Li Alloy

The microstructure and mechanical properties of hot-rolled Mg-8 wt.% Li and Mg-8 wt.% Li-6 wt.% Zn-1.2 wt.% Y alloys were investigated, and it was demonstrated that due to the formation of the I-phase (Mg3Zn6Y, icosahedral structure), the crystallographic texture and strength of the alloys is weakened and increased, respectively. At different hot-rolled ratios, the anisotropy (plasticity) of Mg-8 wt.% Li alloy exhibits obviously stronger than the Mg-8 wt.% Li-6 wt.% Zn-1.2 wt.% Y alloy. Failure analysis indicated that ductile fracture occurs along the rolling direction (RD), while quasi-cleavage fracture occurs along the transverse direction (TD). Cracks in the Mg-8 wt.% Li were found to be mainly initiated at the alpha-Mg phase and the two-phase boundary, which were respectively generated by tensile testing along the RD and TD. The cracks in the Mg-8 wt.% Li-6 wt.% Zn-1.2 wt.% Y alloy were confirmed to be located in the rich I-phase region of the alpha-Mg phase and at the junction site of the matrix phases.