High strength magnesium alloy and preparation method thereof

The present invention relates to a high strength magnesium alloy and a preparation method thereof. The magnesium alloy comprises the following components, by mass: 1.0-15.0% of Cd, 2.0-10.0% of Bi, 5.0-13.0% of Zn, 7.0-15.0% of Y, 0.4-1.0% of Zr, 0.1-5.0% of Nb, impurity elements, and the balance of Mg, wherein the total amount of the impurity elements such as Si, Fe, Cu and Ni is less than 0.02%. The preparation method comprises: adopting an electromagnetic semi-continuous casting method to prepare a magnesium alloy ingot billet, sequentially carrying out uniformization annealing and surface turning on the ingot billet, heating, adopting a reverse extrusion device to carry out reverse extrusion on the ingot billet, and carrying out a heat treatment on the extruded rod material. According to the prepared magnesium alloy material, room temperature mechanical properties can be that a tensile strength is 410-450 MPa, a yield strength is 350-380 MPa, and an elongation rate is more than 6%.