Microstructures and mechanical properties in a Gd-modified high-pressure die casting Mg–4Al–3La−0.3Mn alloy

Abstract

Effects of 2 wt% Gd addition on microstructures and tensile properties of a high-pressure die casting (HPDC) Mg–4Al–3La−0.3Mn (wt.%) alloy were studied. The newly developed alloy owns much finer grains than commercial/experimental HPDC Mg alloys. Furthermore, it contains various intermetallic phases, namely η-Al3(La,Gd), Al2(Gd,La) or Al2(La,Gd), Al7(La,Gd)3 and Al2.12(La,Gd)0.88, among which Al7(La,Gd)3 was experimentally observed in Mg–Al−RE-based alloys for the first time. Moreover, both η-Al3(La,Gd) and Al2(Gd,La) present two or more morphologies due to different chemical compositions. Finally, the studied alloy exhibits more excellent tensile properties than commercial/experimental HPDC Mg–Al-based alloys. The underlying causes for grain refinement, variety of intermetallic phases, as well as excellent tensile properties were discussed and revealed.