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

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 Al 2 Ca 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. • Effects of microalloying addition of Ca on corrosion behavior of extruded AZ31 were studied. • The microstructure of AZ31 was refined by alloying of Ca and complete recrystallization occurred in AZ31-0.2Ca. • AZ31-0.05Ca had a higher corrosion rate than AZ31, which may attribute to severe microgalvanic corrosion. • AZ31-0.1Ca and AZ31-0.2Ca had a lower corrosion rate due to the modified microstructure and a more protective corrosion film. [ABSTRACT FROM AUTHOR]