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 α-Mg matrix and Mg2Sn phase. The number of the Mg2Sn particles significantly increased and the grains were gradually refined (14.2 ± 1.5, ~10.7 ± 0.7 and ~6.6 ± 1.1 μm), 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.