Effect of microalloyed Ca on the microstructure and corrosion behavior of extruded Mg alloy AZ31

Abstract The present work investigated the effect of microalloyed Ca on the microstructure and corrosion properties of extruded Mg alloy AZ31. The microstructure and corrosion behaviors were examined using optical and electron microscopies, immersion tests and electrochemical measurements. The grain size of AZ31 was refined by the addition of Ca and complete recrystallization occurred in AZ31-0.2Ca which had fine uniform grains. AZ31–0.05Ca showed a small number of Mg–Al–Ca phase particles, which may lead to severe microgalvanic corrosion and a higher corrosion rate than AZ31. AZ31-0.1Ca and AZ31-0.2Ca possess many dispersed fine Al2Ca phase particles, which could be beneficial to form continuous corrosion products and a more protective corrosion products film. Thus, AZ31-0.1Ca and AZ31-0.2Ca had a somewhat lower corrosion rate than AZ31.