Microstructures and mechanical properties of heat-resistant high-pressure die-cast Mg-4Al-6RE-0.3Mn (RE= La, Ce, Pr, Nd, wt.) alloys

摘要

Mg-4Al-6RE-0.3Mn (RE=La, Ce, Pr, Nd, wt.%) magnesium alloys were prepared successfully by the high-pressure die-casting technique. The microstructures and tensile properties in the temperature range from room temperature to 200°C were investigated. It was confirmed that the Mg-Al-RE-based alloys exhibited an outstanding die-cast character. The cross-section of test bar could be divided into the fine skin region and the relatively coarse interior region by a narrow band with fine structure. Two binary Al-RE (RE=La, Ce, Pr, Nd) phases with the former being the dominant one, Al11RE3 and Al2RE, occupied large grain boundary area. All the four alloys exhibited excellent tensile properties until 200°C, which were mainly attributed to the fine grain size and the strengthening phase Al11RE3 with high volume fraction, fine acicular/lamellar morphology, "orderly stack” distribution and good thermal stability. The results of this work provided a basis for further investigation of the new heat-resistant high-pressure die-cast magnesium alloys designed to serve at temperature up to 200°C.