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.