Effect of heat treatment on corrosion behaviour of magnesium alloy AZ91D in simulated body fluid

The research explored ways of improving corrosion behaviour of AZ91D magnesium alloy through heat treatment for degradable biocompatible implant application. Corrosion resistance of heat-treated samples is studied in simulated body fluid at 37 °C using immersion and electrochemical testing. Heat treatment significantly affected microgalvanic corrosion behaviour between cathodic β-Mg17Al12 phase and anodic α-Mg matrix. In T4 microstructure, dissolution of the β-Mg17Al12 phase decreased the cathode-to-anode area ratio, leading to accelerated corrosion of α-Mg matrix. Fine β-Mg17Al12 precipitates in T6 microstructure facilitated intergranular corrosion and pitting, but the rate of corrosion was less than those of as-cast and T4 microstructures.