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

摘要

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 vit.% Ce/La exhibits high tensile properties and good heat resistance until 200 °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-AI-RE alloys designed to serve at temperature up to 200 °C.