Effects of Alloying Elements on the Dissolution and Precipitation Behaviour of Fe in Mg-Al Alloy Melts

It is necessary to strictly control the iron (Fe) impurity in Mg-Al alloys to guarantee good corrosion resistance and mechanical properties. In this work, the effects of alloying elements and temperatures on the solubilities of Fe in the Mg-Al-based alloy melts (Mg-rich liquid phases) at 963–1033 K were studied by combining the in situ sampling method for the high precision solution values and the multiple regression numerical analysis method for the feature analysis. The solubilities of Fe in Mg-xAl (x = 1 and 3 wt.%) alloy melts could be significantly reduced by adding the yttrium (Y) or manganese (Mn) elements. However, the solubilities of Fe in Mg alloy melts were not in a monotonous relationship with the contents of the alloying elements in the Mg alloys. For the addition of Mn or Y, the lowest solubilities of Fe presented in the Mg-rich liquid phases were for the Mg-xAl alloys with the addition of 2 wt.% Mn or 1 wt.% Y, respectively. Additionally, the Fe-containing precipitations in the related systems were analysed and the Fe was mainly combined with Mn or Y and precipitated, which contributed to the removal of Fe from the Mg melt. The present study provides fundamental thermodynamic information regarding Mg-Al-Fe based systems and the design principle for the removal of Fe in Mg alloys.