Influence of lanthanum on the microstructure, mechanical property and corrosion resistance of magnesium alloy

The microstructure, mechanical property and corrosion behavior of AZ91D with addition of lanthanum were investigated. With adding 1% lanthanum, the ultimate tensile strength and the elongation increased by 21.1% and by 101.2%, respectively. This mainly caused by the refinement of the b phase and the formation of Al11La3 strengthening phase. With adding 1% lanthanum in AZ91D alloy, the weight loss corrosion rate decreased to 47.2%. But when lanthanum content is over 1%, the corrosion rate increased. Small amount of lanthanum could form the small b phase similar to reticular structure, which could restrain the corrosion at some extent; large amount of lanthanum caused the depletion of aluminum in a matrix, which increased the corrosion rate.