Improved corrosion resistance of a high-strength Mg–Al–Mn–Ca magnesium alloy made by rapid solidification powder metallurgy

The mechanical property and in particular the corrosion behavior of an Mg–Al–Mn–Ca alloy produced by spinning water atomization process (SWAP) were investigated and compared to those of the alloys made by gravity cast and hot extrusion. It is found that the SWAPed alloy has not only superior mechanical properties but also distinguished corrosion resistance. The corrosion resistance of the SWAPed alloy is about 2.5 and 10 times higher than that of the hot-extruded and as-cast alloys, respectively, when immersed in 0.1 M NaCl solution. Potentiodynamic polarization shows that both the anodic and cathodic current densities of the three alloys in 0.1 M NaCl solution are in the order of SWAPed alloy < hot-extruded alloy < as-cast alloy. The depressed cathodic and anodic reactions of the SWAPed alloy are attributed to the fine dispersed intermetallic phase and the supersaturated composition in α-Mg matrix, respectively. The present results demonstrate that the corrosion resistance of magnesium alloys can be greatly improved via the dispersion of intermetallic phase by the process such as SWAP.