Microstructure, mechanical properties and bio-corrosion properties of Mg–Zn–Mn–Ca alloy for biomedical application

Microstructure, mechanical properties and bio-corrosion properties of as-cast Mg–Zn–Mn–Ca alloys were investigated for biomedical application in detail by optical microscopy, scanning electronic microscopy (SEM), mechanical properties testing and electrochemical measurement. SEM and optical microscopy observation indicated that the grain size of the as-cast alloys significantly decreased with the increasing of Ca content up to 0.5 wt.%. Further increasing of Ca content did not refine the grain more. The phase constitute was mainly controlled by the atomic ratio of Zn to Ca. When the ratio was more than 1.0–1.2, the alloy was mainly composed of primary Mg and lamellar eutectic (α-Mg + Ca2Mg6Zn3), while the alloy was composed of primary Mg and divorced eutectic (α-Mg + Mg2Ca + Ca2Mg6Zn3) when the atomic ratio was less than 1.0–1.2. The yield strength of the as-cast alloy increased but the elongation and the tensile strength increased first and then decreased with the increasing of Ca content. It was thought that Mg2Ca phase deteriorated the tensile strength and ductility. Electrochemical measurements indicated that Mg2Ca phase improved the corrosion resistance of the as-cast alloy.