A continuous net-like eutectic structure enhances the corrosion resistance of Mg alloys

Mg alloys degrade rather rapidly in a physiological environment, although they have good biocompatibility and favorable mechanical properties. In this study, Ti was introduced into AZ61 alloy fabricated by selective laser melting, aiming to improve the corrosion resistance. Results indicated that Ti promoted the formation of Al-enriched eutectic α phase and reduced the formation of β-Mg₁₇Al₁₂ phase. With Ti content reaching to 0.5 wt.%, the Al-enriched eutectic α phase constructed a continuous net-like structure along the grain boundaries, which could act as a barrier to prevent the Mg matrix from corrosion progression. On the other hand, the Al-enriched eutectic α phase was less cathodic than β-Mg₁₇Al₁₂ phase in AZ61, thus alleviating the corrosion progress due to the decreased potential difference. As a consequence, the degradation rate dramatically decreased from 0.74 to 0.24 mg·cm^-2·d^-1. Meanwhile, the compressive strength and microhardness were increased by 59.4% and 15.6%, respectively. Moreover, the Ti-contained AZ61 alloy exhibited improved cytocompatibility. It was suggested that Ti-contained AZ61 alloy was a promising material for bone implants application.