Microstructure, corrosion and mechanical properties of as-cast Mg-Zn-Y with different Zn-to-Y ratios

As-cast Mg-8Zn-xY (x = 1.4, 3.4, and 6.7; wt%) alloys containing I-phase, mixed I- and W-phases, W-phase were prepared, respectively. With the decrease of Zn/Y ratio, the second phase gradually changes from discontinuous network structure to continuous network structure. The effect of second phase on the corrosion resistance of MgZn-Y alloy was studied in detail by testing the hydrogen evolution, polarization curve, corrosion morphology and Volta potential. The results show that Mg-8Zn-3.4Y alloy containing mixed W- and I-phases has the best corrosion resistance. The good corrosion resistance can be attributed to the network structure of mixed W- and I-phases which can prevent the extension of corrosion. In addition, Mg-8Zn-3.4Y alloy exhibits the yielding strength of 123 MPa, ultimate strength of 219 MPa, and elongation to fracture of 14 %. The good combination of corrosion and mechanical properties for the current alloy is helpful for the further application.