Effects of rare earth neodymium (Nd) and heat treatment on anti-corrosion behaviors of the AZ80 magnesium alloy

The effect of rare earth neodymium (Nd) and heat treatment on the corrosion resistance of AZ80-xNd ( x = 0, 0.5, and 1.0 wt.%) magnesium alloys was investigated. Compared to the as-cast AZ80 magnesium alloy, new rod-shaped Al 3 Nd phase and block-shaped Al 2 Nd phase were observed in AZ80-Nd alloy. Moreover, β-Mg 17 Al 12 phase becomes fine and discontinuous. The reduction of the β-Mg 17 Al 12 phase and the formation of the Al-Nd binary phase significantly reduced the corrosion rate of the AZ80-Nd alloy by suppressing micro-galvanic corrosion of the alloy. However, with increase in the the wt.% of Nd, the Al-Nd binary phase content increases, and the grain size become coarser, thereby lowering the corrosion resistance of the alloy. Therefore, the as-cast 0.5% Nd alloy with fine grain structure has a good corrosion resistance. After the solution treatment, the β-Mg 17 Al 12 phase and part of the Al-Nd binary phase were dissolved in the magnesium matrix, which facilitates the occurrence of corrosion. Therefore, the corrosion rate of solution treated alloys is higher than that of the as-cast alloys. After aging treatment, the β-Mg 17 Al 12 phase and Al-Nd binary phase are re-precipitated along the grain boundaries and within the grains, respectively. The fine and uniformly distributed β-Mg 17 Al 12 phase, rod-shaped Al 3 Nd phase and block-shaped Al 2 Nd phase effectively improve the corrosion resistance of the alloy, so that the corrosion rate of the aged alloy is the lowest. The electrochemical and immersion measurements revealed that the aged AZ80-0.5%Nd alloy had the best corrosion resistance. Graphical abstract