Microstructures and mechanical properties of heat-resistant high-pressure die-cast Mg–4Al–xLa–0.3Mn (x = 1, 2, 4, 6) alloys

Mg–4Al–xLa–0.3Mn (x = 1, 2, 4 and 6 wt.%) magnesium alloys were prepared successfully by the high-pressure die-casting technique. The microstructures, tensile properties in the temperature range from room temperature to 300 °C and heat resistance were investigated. It was confirmed that the Mg–Al–La-based alloys exhibited outstanding die-cast character. The cross-section of test bar could be divided into two parts by a narrow band, that is, the fine skin region and the relatively coarse center region. When addition of La reached 4 wt.%, the die-cast alloy exhibited high tensile properties and good heat resistance up until 200 °C. It was demonstrated that the outstanding mechanical properties were mainly attributed to the fine grain size and the strengthening phase Al11La3, which was in high volume fraction, fine acicular/lamellar morphology, “orderly stack” distribution and excellent thermal stability. The result of this research provided a basis for further investigation of the new high-pressure die-cast Mg–Al–RE alloys designed to serve at temperature up to 200 °C.