Magnesium alloy, preparation method thereof, magnesium alloy cast ingot and application

The invention discloses a magnesium alloy and a preparation method thereof, a magnesium alloy cast ingot and application, the magnesium alloy comprises, by weight, 5%-12% of gadolinium, 1%-5% of yttrium, 1%-5% of samarium, 0.1%-0.8% of zirconium, 0.01%-0.5% of metal A and 80%-90% of magnesium, and the metal A is selected from one or more of lanthanum and strontium. According to the magnesium alloy material, the raw material components are regulated and controlled, the matrix metal magnesium is strengthened by means of dispersed nanoscale rare earth phases separated from rare earth metal samarium, gadolinium and yttrium at the grain boundary, and coarsening and growth of crystal grains in the heat treatment process are inhibited by means of high-temperature stable phases separated from lanthanum or strontium. The metal raw materials can give full play to the solid solution strengthening, aging strengthening, fine grain strengthening and synergistic strengthening effects of elements, so that the heat resistance