Improved corrosion resistance of magnesium alloy prepared by selective laser melting through T4 heat treatment for biomedical applications

Selective laser melting (SLM) technology has broad prospects for developing magnesium alloys in structural and biomedical applications. The effects of T4 heat treatment on microstructure, mechanical properties and corrosion resistance of as-built AZ91D alloy were investigated. The results showed that after T4 treatment, β-Mg17Al12 phases distributed around the matrix changed from networks to diffuse dots and then disappeared at 420°C for 1h. The tensile strength and hardness of AZ91D alloy decreased after T4 treatment. In addition, electrochemical and immersion experiments showed that the corrosion resistance was greatly improved after solution. Compared with the as-built AZ91D alloy, the solution-treat sample exhibited higher corrosion resistance in Hanks' solution, and its corrosion current density was reduced by 70%, hydrogen evolution rate by 57%, and corrosion rate by about 78% in the weightless experiment. In this study, after solution-treat, the corrosion resistance of as-built AZ91D can be significantly improved while meeting the mechanical requirement of degradable alloys, and has great potential for biomedical applications.