Effect of Si and P on Microstructure and Mechanical Properties of Mg-7Al-1Zn-3.597Cu-xSi Alloys

In order to improve the heat resistant properties of magnesium alloys, the effects of P modification on phase constituent, microstructure and mechanical properties of Mg-7Al-1Zn-3.597Cu-xSi (x=1, 2, 3) alloys were investigated by means of x-ray diffractometer (XRD), scanning electron microscopy (SEM), and universal electronic testing machine. The results indicate that the Mg2Si phase presented in the form of Chinese script shape was observed in the microstructure of the alloy without P element. The addition of P element can refine the microstructure by making Mg2Si phase change from Chinese script shape into block shape. The optimum properties with tensile strength, yield strength and elongation of 192.91 MPa, 115.42 MPa and 4.6% respectively are obtained for the alloy by adding 0.5% P and 1% Si elements. The mechanical properties of the alloys decrease with further increasing the Si content.