The effects of yttrium element on microstructure and mechanical properties of Mg–5 wt.% Zn–2 wt.% Al alloy

The addition of yttrium element to the Mg–5 wt.% Zn–2 wt.% Al alloy leads to the formation of bacillary Al11Y3 phase and polygonal compound Al2Y in the microstructure, and as-cast tensile properties at room temperature are improved substantially when yttrium content is above 1 wt.%. Mg–5 wt.% Zn–2 wt.% Al–2 wt.% Y alloy exhibits a combination of high strength and good ductility, the dominant dispersoid in the microstructure is Al11Y3 phase. Large Al2Y phase becomes dominant when yttrium content is above 2.0 wt.%, and causes an adverse cutting effect. The study also shows that 2.44 wt.% yttrium content in the alloy brings about a mild refining effect.