Effect of Mn addition and refining process on Fe reduction of Mg?Mn alloys made from magnesium scrap

The Fe reduction, microstructure evolution and corrosion susceptibility of Mg?Mn alloys made from magnesium scrap refining with Mn addition were investigated. The results show that significant Fe content change occurs during near-solid-melt treatment (NSMT) process even in the absence of Mn, because of the high saturation of Fe in the melt. Furthermore, in the NSMT process, even a small amount of Mn addition can lead to a sharp deposition of Mn atoms. The NSMT process can increase the growth rate of the Fe-rich particles, and then accelerate their sinking movement. Nevertheless, the addition of Mn hinders the coarsening process of Fe-rich particles. Besides, the corrosion susceptibility of the alloys is mainly affected by the solubility of Fe, which can be significantly reduced by Mn addition. Moreover, the presence of more Fe-rich particles does not necessarily increase the corrosion susceptibility of the alloy. Consequently, in the refining process of Mg?Mn alloys made from magnesium scrap, on the basis of NSMT process and adding an appropriate Mn content (about 0.5 wt.%), the purity of the melt can be improved, thereby obtaining an alloy with excellent corrosion resistance.