Preparation method of high-strength and high-toughness rapidly-degraded magnesium alloy

The invention discloses a preparation method of high-strength and high-toughness rapidly-degraded magnesium alloy. The preparation method comprises the following steps: preheating a crucible to be at a temperature of about 600 DEG C, spreading a small amount of molten salt covering agent on the wall and at the bottom of the crucible, adding a pure magnesium block and spreading a layer of molten salt covering agent on the surface of the magnesium block; heating the crucible, preserving heat when the temperature is raised to 720 DEG C, and adding Cu after magnesium is completely molten; raising the temperature of the crucible to 720-725 DEG C, adding Mg-Y intermediate alloy, and stirring while adding; continuing raising the temperature, raising the temperature of the crucible to740 DEG C, and adding a No. 5 magnesium alloy dedicated agent and a tranquilizer; cooling to 700 DEG C by standing, adding an intermediate phase into the alloy, and starting casting to obtain Mg-4Y-2Cu alloy. An LPSO structural phase cap