Determination of Optimum Zn Content for Mg-xZn-0.5Mn-0.5Sr Alloy in Terms of Mechanical Properties and In Vitro Corrosion Resistance

This study investigated the microstructure, compressive properties and in vitro corrosion behavior of biodegradable Mg-xZn-0.5Mn-0.5Sr (ZMJ) alloy with Zn content of 0 to 5 wt% in the as-cast state. Increasing the Zn content in ZMJ alloy refined the grains from 215 to 95 mu m and changed the secondary particles from Mg17Sr2 to Mg6Zn2Sr and MgZn phases. As the Zn content increased, the compressive yield strength increased from 44 to 67 MPa due to grain boundary strengthening. At immersion in phosphate-buffered saline for 7 days, the addition of Zn from 0 to 0.1 wt% reduced the corrosion rate from 0.71 to 0.48 mm/y, and 0.85 wt% Zn was alloyed to obtain the lowest corrosion rate of 0.45 mm/y. However, adding more Zn significantly increased the corrosion rate up to 3.31 mm/y. Thus, the best anti-corrosion performance can be obtained at 0.85 wt% Zn, which was attributed to its lowest Volta potential difference between the main secondary particles and the alpha-Mg matrix among ZMJ alloy. Based on this, the optimal Zn content for ZMJ alloy can be determined to be about 1 wt% by comprehensively considering the mechanical properties and in vitro corrosion behavior for biomedical applications.