Microstructures and mechanical properties of heat-resistant HPDC Mg-4Al-based alloys containing cheap misch metal

Mg-4Al-xCe/La-0.3Mn (Ce/La: mixture of Ce and La, x = 1, 2, 4 and 6 wt.%) alloys were prepared by high-pressure die-casting. The microstructures, mechanical properties and thermal stability were investigated. The cross-section of test bar could be divided into the fine skin region and the relatively coarse interior region. Two binary Al-(Ce. La) phases with the former being the dominant one, Al(11) (Ce, La)(3) and Al(2)(Ce, La), are mainly distributed along the dendrite boundaries, and La prefers to exist in Al(11) (Ce, La)(3). The alloy with 4 wt.% Ce/La exhibits high tensile properties and good heat resistance until 200 degrees C, which were mainly attributed to the fine dendritic arm spacing and the main strengthening phase Al(11) (Ce, La)(3), which is present in high volume fraction, and possesses fine rod-like morphology, network or "orderly stack" distribution and good thermal stability. The results of this research provide a basis for further investigation of the new low cost high-pressure die-cast Mg-Al-RE alloys designed to serve at temperature up to 200 degrees C. (C) 2010 Elsevier B.V. All rights reserved