Effect of Minor Yttrium on Microstructure and Mechanical Properties of Bioimplant Mg-5Zn Alloy

This paper explores cast Mg-5Zn alloy, containing small amounts of yttrium (Y: 0.1-1.5 wt.%), through microstructure evaluation and tensile and hardness tests. The results reveal that addition of Y to the alloy refines microstructure, especially when secondary phases, Mg₃Zn₆Y (I) and Mg₃Zn₃Y₂ (W), form. I-phase is detected when 0.3 wt.% Y is added to the alloy, while W-phase is only observed in Mg-5Zn-1.5Y alloy. The results also show that the addition of Y improves yield and tensile strength as well as the hardness value of the Mg-5Zn alloy at the expense of its formability. The three effects of the solid solution of Y in α-Mg, grain refinement, and the formation of I- and W-phases are the reasons for such behavior. The improvement is more pronounced when W-phase appears in the microstructure. In other words, Mg-5Zn-1.5Y alloy behaves stronger and harder than other alloys and may be considered as a potential candidate for bioimplant applications if its degradation behavior meets the requirements.