Effect of Icosahedral Phase on Crystallographic Texture and Mechanical Anisotropy of Mg-4%Li Based Alloys

Through investigating and comparing the microstructure and mechanical properties of the as-extruded Mg alloys Mg-4%Li and Mg-4%Li-6%Zn-1.2%Y (in wt%), it demonstrates that although the formation of I-phase (Mg3Zn6Y, icosahedral structure) could weaken the crystallographic texture and improve the mechanical strength, the mechanical anisotropy in terms of strength remains in Mg-4%Li-6%Zn-1.2%Y alloy. Failure analysis indicates that for the Mg-4%Li alloy, the fracture surfaces of the tensile samples tested along transverse direction (TD) contain a large number of plastic dimples, whereas the fracture surface exhibits quasi-cleavage characteristic when tensile samples were tested along extrusion direction (ED). For the Mg-4%Li-6%Zn-1.2%Y alloy, typical ductile fracture surfaces can be observed in both “TD” and “ED” samples. Moreover, due to the zonal distribution of broken I-phase particles, the fracture surface of “TD” samples is characterized by the typical “woody fracture”.