Structure stability and mechanical properties of Mg-Al-based alloy modified with Y-rich and Ce-rich misch metals

Mg-3.4 wt.% Al-based alloy modified with 2.4 wt.% Ce-rich and 0.3 wt.% Y-rich misch metals was prepared by high-pressure die-casting. The microstructure, thermal stability of intermetallic phases and mechanical properties were investigated. The cross-section of test bar is divided into the fine skin region and the wide core region by a narrow band. Two intermetallic phases Al11RE3 and Al2RE, with the former being the dominant one, are mainly distributed at the interdendritic regions. The Al11RE3 intermetallics possess high volume fraction, fine acicular/lamellar morphology and layered arrangement. It is suggests that each rare earth element has the individual preference for the above two Al-RE intermetallics. The thermal stability of Al11RE3 is conditioned. It is basically stable at temperature up to 200 degrees C within 800 h, while almost all Al11RE3 intermetallics transform to Al2RE at higher temperature of 450 degrees C for 800 h. The alloy exhibits remarkably improved tensile and compressive yield strengths at room temperature and 200 degrees C and they are the results of the reinforcement of dendrite boundaries with Al11RE3 intermetallics, the fine dendritic arm spacing effect as well as the solid solution strengthening with various rare earth elements. (C) 2011 Elsevier B.V. All rights reserved.