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

Abstract

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, Al 11RE 3 and Al 2RE, 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 Al 11La 3 phase. And in Mg–4Al–4La–0.4Mn alloy the Al 11La 3 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 Al 11La 3 phase in Mg–4Al–4La–0.4Mn alloy than that of Al 11RE 3 phase in Mg–4Al–4RE–0.4Mn alloy.