Effect of heat treatment on microstructure and corrosion behavior of Az91d magnesium alloy

Abstract

An AZ91D ingot in the as-cast condition was homogenized by heat treatment process. Then, the microstructures produced and corrosion behaviour after heat treatment was studied in detail. As-cast AZ91D was recrystallize by solution treatment at 415°C and then aged at 175°C for various period of time. The corrosion resistance of all the different microstructures was studied in NaCl solution through weight loss measurement in immersion testing. The β phase was found to have a significant influence on the corrosion behaviour. In solution treatment, β phase dissolution decreased the cathode area leading to accelerated corrosion rate. After aging treatment, fine β phase precipitates between grain and microstructure recrystallize causing an increase in the corrosion resistances.