Effect of substituting cerium-rich mischmetal with lanthanum on microstructure and mechanical properties of die-cast Mg–Al–RE alloys

Die-cast Mg–4Al–4RE–0.4Mn (RE = Ce-rich mischmetal) and Mg–4Al–4La–0.4Mn magnesium alloys were prepared successfully and their microstructure, tensile and creep properties have been investigated. The results show that two binary Al–RE phases, Al11RE3 and Al2RE, are formed along grain boundaries in Mg–4Al–4RE–0.4Mn alloy, while the phase compositions of Mg–4Al–4La–0.4Mn alloy mainly consist of α-Mg phase and Al11La3 phase. And in Mg–4Al–4La–0.4Mn alloy the Al11La3 phase occupies a large grain boundary area and grows with complicated morphologies, which is characterized by scanning electron microscopy in detail. Changing the rare earth content of the alloy from Ce-rich mischmetal to lanthanum gives a further improvement in the tensile and creep properties, and the later could be attributed to the better thermal stability of Al11La3 phase in Mg–4Al–4La–0.4Mn alloy than that of Al11RE3 phase in Mg–4Al–4RE–0.4Mn alloy.