Effects of Nd on Tensile Properties of Mg-6Al As-Cast Alloy

The effects of Nd on the tensile properties of Mg-6Al as-cast alloy were studied. Results show that the yielding strengths of Mg-6Al-xNd (x=0, 2, 4, 6; mass fraction) alloys at room temperature and 175 degrees C increased with the Nd content increasing and reached the maximum value at the content of 6.0%Nd. The ultimate tensile strengths and elongations of these alloys at room temperature and 175 degrees C reached their maximum values at the content of 4.0%Nd. Both the ultimate strength and the elongation decreased slightly when the content of Nd increased from 4.0% to 6.0%, which is mainly due to the increase in the brittle phase of Al2Nd. The microstructure analysis indicates that Nd exists in the Mg-6Al alloy in the form of needle-like Al11Nd3 phase and polygonal Al2Nd phase and the amount of Al11Nd3 is much more than that of Al2Nd. The Al11Nd3 phase precipitates at the dendritic and grain boundaries resulting in the obvious refinement of the interdendritic space and grains. The improvement in tensile properties of Mg-6Al-xNd (x=2, 4, 6) alloys is mainly attributed to the grain refinement strengthening and the second phase strengthening caused by the Al11Nd3 phase, which is concluded from the mechanics analysis of the tensile process by hard-soft section model and the tensile fracture observation.