Microstructure and mechanical behavior of Mg-Y-Zn alloys with respect to varying content of LPSO phase

Mg-Y-Zn alloys with different contents of alloying elements were prepared. The microstructure and mechanical properties of these Mg-Y-Zn alloys were investigated by using scanning electron microscopy, X-ray diffraction and tensile testing. The results show that the as-cast Mg-Y-Zn alloy is mainly composed of alpha-Mg, Mg12YZn and Mg3Y2Zn3 phases. After Mn addition, a small quantity of Mn phase arises in the as-cast Mg-Y-Zn-Mn alloy. After extrusion, the microstructure of the alloys is of an inhomogeneous character showing fine grains produced due to dynamic recrystallization. Tensile strength of as-extruded Mg-9Y-1Zn, Mg-9Y-3Zn and Mg-9Y-3Zn-lMn reached 249.86 MPa, 303.19 MPa and 322.15 MPa, respectively. The gradually increasing strength can be attributed to fine grain strengthening, second phase strengthening and LPSO structure. Additionally, the tensile fracture surfaces were examined under scanning electron microscopy, and all of their fracture morphologies exhibit dimple facture character.