Effects of Nanoscale precipitates on mechanical properties, corrosion resistance, and biocompatibility in Zn-Mn alloy.

Controlling degradation rate is essential for the biomedical application of biodegradable Zn alloys. Alloying with soluble elements is an effective way to regulate formation of second phases, which differ in potential from the Zn matrix. The potential difference exhibits positive or negative effects on corrosion resistance. This study successfully forms MnZn phase with nano size by altering ECAP temperature. Subsequently, MnZn phase promotes grain refinement, improvement of elongation, and corrosion resistance. Higher elongation in Zn-Mn alloy with MnZn phase is attributed to the grain boundary sliding, deformation twins in MnZn phase. Meanwhile, grain boundary corrosion in Zn-Mn alloy with MnZn phase is incomplete. Corrosion mode of Zn-Mn alloys without MnZn phase is dominated by grain boundary corrosion, accompanied by pitting corrosion. The increased corrosion resistance from MnZn phase stems from its higher potential than Zn matrix. Zn-Mn alloys with and without MnZn phase show a comparable cytocompatibility and osteogenic properties. Our findings provide an effective way to regulating mechanical properties and corrosion resistance of Zn alloys via controlling precipitation.