Microstructure and mechanical properties of gadolinium- and misch metal-added Mg–Al alloy

The study investigates the effects of individual and combined additions of gadolinium (Gd) and misch metal (MM) on the microstructure and mechanical properties of Mg–4Al and Mg–9Al alloys. The results show that the additions significantly alter the microstructure and grain size of the base alloys. Mg–4Al based alloys have globular morphology, whereas Mg–9Al based alloys have dendritic morphology. The addition of alloying elements, Gd and MM, introduces rectangular-shaped Al2Gd phase and needle-shaped Al11RE3 phase, respectively. The best mechanical properties at room temperature are shown by Mg–9Al–2Gd alloy with tensile strength and elongation of 214 MPa and 6.0%, respectively, whereas Mg–4Al–2Gd alloy exhibits the best properties at elevated temperature (150 °C) with tensile strength and elongation of 172 MPa and 14.0%, respectively. The study also reports the microhardness value of different phases along with the cast alloys. Eutectic Mg17Al12 phase shows the highest hardness (VHN 92) followed by lamellar Mg17Al12 (VHN 83) and α-Mg matrix (VHN 68).