1. It has the effect of aging precipitation and strengthening. The high solid solubility of rare earth elements in magnesium decreases as the temperature decreases. When the single-phase solid solution at high temperature is rapidly cooled, an unstable supersaturated solid solution is formed. After a long period of aging, fine and dispersed solid solutions are formed. of precipitation phase. The interaction between precipitated phases and dislocations increases the strength of the alloy.
2. The effect of fine grain strengthening. The enrichment of rare earth elements at the front edge of the solid-liquid interface causes supercooling of the components, and a new nucleation zone is formed in the supercooling zone to form fine equiaxed crystals. In addition, the enrichment of rare earth elements prevents the growth of α-Mg grains. further promotes grain refinement.
3. Melt purification effect. Rare earth elements can remove hydrogen, oxygen, sulfur, iron and inclusions in magnesium alloy melts, achieving the effects of degassing, refining and purifying the melt.
4. Melt protection effect. Magnesium alloys are very easy to oxidize and burn during the smelting process. Industrial production of magnesium alloys is generally smelted by flux covering or gas protection methods, but both have many shortcomings. If the ignition temperature of the magnesium alloy melt itself can be increased, it is possible to achieve magnesium alloy Direct smelting under atmosphere is of great significance to the further promotion and application of magnesium alloys. Rare earth is a surface-active element of magnesium alloy melt, which can form a dense composite oxide film on the surface of the melt, effectively preventing the contact between the melt and the atmosphere, and greatly increasing the ignition temperature of the magnesium alloy melt.
