Heat-resistant magnesium alloy and preparation method thereof

The invention provides a heat-resistant magnesium alloy. The magnesium alloy comprises the following components: 3.5wt%-4.5wt% of Al, 2.5wt%-3.5wt% of La, 1.5wt%-3.0wt% of Sm, 0.2wt%-0.4wt% of Mn, impurity elements of which the total amount is less than 0.03wt% and the balance of magnesium. The invention provides a preparation method of the magnesium alloy. The preparation method comprises the steps of smelting a magnesium source, an aluminum source, a lanthanum source, a samarium source and a manganese sources to obtain an alloy liquid; carrying out press casting on the alloy liquid to obtain the heat-resistant magnesium alloy. Since the heat-resistant magnesium alloy provided by the invention contains rare earth elements, namely, La and Sm, La and Sm inhibit the generation of Mg17Al12 phase, and Sm can have a better solution strengthening effect, and thus the heat-resistant magnesium alloy provided by the invention has the advantages of good mechanical properties and creep resistance at high temperature.