Microstructure and bio‐corrosion behavior of Mg–Zn and Mg–Zn–Ca alloys for biomedical applications

Abstract

The microstructure and bio‐corrosion behavior of binary Mg– x Zn ( x = 1.25, 2.5, 4) and ternary Mg–Ca– x Zn ( x = 1.25, 2.5, 4) alloys have been studied using scanning electron microscopy (SEM), electrochemical, and immersion tests. Microstructure analysis indicated that the binary Mg–Zn alloys are composed of primary α‐Mg matrix and Mg 12 Zn 13 phases, while, ternary Mg–Ca–Zn alloys are composed of α‐Mg, Mg 2 Ca, and IM1 (Ca 3 Mg x Zn 15− x ) (4.6 ≤ x ≤ 12) phases or α‐Mg, IM1 and IM3 (Ca 2 Mg 5 Zn 13 ) phases. Electrochemical results showed that Mg–4Zn alloy has lowest corrosion rate among binary alloys. At constant Ca content of 0.8 wt.%, the addition of Zn up to 1.25 wt.% decreased the corrosion rate, while further addition of Zn increased the corrosion rate of ternary alloys. Immersion tests results demonstrated that the formation of Zn oxide layer in binary Mg–Zn alloy and evolution of eutectic phase (α‐Mg + IM1 + Mg 2 Ca) significantly retard the bio‐degradation rate of the ternary alloys.