Effects of ytterbium addition and heat treatment on the mechanical properties and biocorrosion behaviors of Mg–Zn–Zr alloy

Mechanical properties and biocorrosion behaviors in simulated body fluid (SBF) of newly developed Mg–5.8 Zn–0.5 Zr–x Yb (ZK60–x Yb, x = 0, 1.0, 2.0 wt%) magnesium alloys in the solution-treated (T4) and artificially-aged (T6) conditions were investigated. The results of mechanical properties show that with Yb addition, the microhardness and the ultimate tensile strength (UTS) of the tested alloys are significantly increased despite a slight decrease in tensile elongation in both T4 and T6 conditions. Especially, after the T6 treatment, the microhardness and the UTS of the samples were further improved, which was mainly attributed to the precipitation strengthening. The biocorrosion behaviors of the tested alloys were studied using electrochemical examinations and immersion tests. The results indicate that the biocorrosion resistance of the tested alloys is significantly improved by Yb addition in both T4 and T6 conditions. Although the corrosion resistance was slightly deteriorated after T6 treatment, the aged ZK60–2.0 Yb alloy still exhibited a favorable corrosion behavior, which was mainly ascribed to the corrosion barrier effect of a more compact and uniform protective film induced by the dispersed nano-scale precipitates. Electrochemical measurements also confirmed these observations. Given the favorable comprehensive performance in mechanical and biocorrosion behaviors, the T6 treated ZK60–2.0 Yb alloy may be considered as a promising candidate for biomedical applications.