Low-cost high-toughness high-heat-resistance die-casting magnesium alloy and preparation method thereof

According to the low-cost, high-toughness and high-heat-resistance die-casting magnesium alloy and the preparation method thereof, on the basis of a conventional AZ91D magnesium alloy, Si and La or Ce elements are added in a composite mode, and on the premise that no expensive rare earth element is added and it is guaranteed that the alloy has the excellent casting performance, the high-strength, high-toughness and high-heat-resistance die-casting magnesium alloy is obtained; the problem that high heat resistance and high toughness of an existing magnesium alloy cannot be considered at the same time is solved, the mechanical property of the magnesium alloy at the room temperature and the high temperature (175 DEG C) is effectively improved, and the magnesium alloy has good heat resistance. The room temperature yield strength of the magnesium alloy is 190-200 MPa, the tensile strength of the magnesium alloy is 270-280 MPa, and the ductility of the magnesium alloy is 5-7%. Under the high-temperature condition o