Heat-crack-resistant high-strength high-plasticity rare earth magnesium alloy and preparation method thereof

The invention discloses a heat-crack-resistant high-strength high-plasticity rare earth magnesium alloy and a preparation method thereof. The magnesium alloy comprises the following specific components of 0.1-6.0 wt% of Y, 0.1-6.0 wt% of Sm, 0.01-2.0 wt% of Zn, 0.01-2.0 wt% of Sn, 0.01-2.0 wt% of Ca, 0.01-1.0 wt% of Sr, 0.1-1.0 wt% of Zr and the balance Mg and inevitable impurities, the impurity content is less than or equal to 0.1 wt%, and the preparation method comprises the steps of alloy casting and heat treatment. According to the heat-crack-resistant high-strength high-plasticity rare earth magnesium alloy and the preparation method thereof, cheap light and heavy rare earth elements such as Sm and Y and non-rare earth elements such as Zn, Sn, Ca and Sr are used for multi-element microalloying, the mechanical property of the alloy is improved by generating a long-range ordered phase, a precipitated phase and a dispersed phase with good thermal stability and reducing a solidification interval, the casting