Understanding the high temperature oxidation and ignition behaviour of two-phase Mg-Nd alloys and a comparison to single phase Mg-Nd

The oxidation kinetics and the mechanism of two-phase Mg-Nd alloys were investigated via isothermal heating experiments conducted in dry air at 500 degrees C for 12h. The oxidation kinetic curves reveal improved oxidation resistance on neodymium (Nd)-containing alloys compared to pure Mg. A lower mass gain was detected at 2.5-%Nd than at 6-Nd%, which was related to the lower amount of intermetallic phase on the alloy surface. The intermetallic phase has a significant effect on the oxide growth stage. Nd2O3 formation on the intermetallic phases creates diffusion paths for oxygen to the metal/oxide interface, affecting both the oxidation kinetics and the oxidation resistance of the alloys. The formation of a Nd-depleted region at the subsurface due to extensive Nd oxidation at the oxide/intermetallic interface lowers the protective ability of the oxide scale. As increasing the Nd content of binary Mg-Nd alloys above 0.5wt% shifts the alloys from single-phase region to two-phase region, it adversely affects the ignition resistance.