Effect of Sn Content on the Microstructure, Mechanical Properties and Corrosion Behavior of Biodegradable Mg-x ( 1, 3 and 5 wt.%) Sn-1Zn-0.5Ca Alloys

The microstructure, mechanical properties and corrosion behavior of hot-rolled Mg-xSn-1Zn-0.5Ca (x = 1, 3 and 5 wt.%) alloys were investigated for possible application as biodegradable implants. The hot-rolled Mg-xSn-1Zn-0.5Ca alloys consisted of alpha-Mg matrix and Mg2Sn phase. The number of the Mg2Sn particles significantly increased and the grains were gradually refined (14.2 +/- 1.5, similar to 10.7 +/- 0.7 and similar to 6.6 +/- 1.1 mu m), while the recrystallized fraction significantly decreased with the increase in the Sn content, the Mg-1Sn-1Zn-0.5Ca alloy was almost completely recrystallized. Ultimate tensile strength (UTS) and tensile yield strength (TYS) increased slightly, reaching maximum values of 247 MPa and 116 MPa, respectively, for the Mg-5Sn-1Zn-0.5Ca alloy, and the elongation decreased with the increase in the Sn content; the Mg-1Sn-1Zn-0.5Ca alloy showed the highest elongation (15.3%). In addition, immersion tests and electrochemical measurements in Hank's solution revealed that the corrosion rates of Mg-xSn-1Zn-0.5Ca alloys increased with the increase in the Sn content. A model of the corrosion behavior was discussed for hot-rolled Mg-xSn-1Zn-0.5Ca alloys in Hank's solution. Among the Mg-xSn-1Zn-0.5Ca (x = 1, 3 and 5 wt.%) alloys, Mg-1Sn-1Zn-0.5Ca alloy exhibits optimal corrosion resistance and appropriate mechanical properties.