Forming method of chemical conversion film of Mg alloy melt

Abstract

The invention provides a forming method of a chemical conversion film of a Mg alloy melt. The method comprises the following steps: (1) simultaneously adding a prefabricated alloy (Mg-Al-Zn-Ce / Sc) and a magnesium ingot which is taken as a raw material; (2) adding the prefabricated alloy (Mg-Al-Zn-Nd / Y-Y / Ce) at a high-temperature phase; (3) forming a low-temperature conversion film by a mixed atmosphere in a furnace and the surface of an alloy liquid during a low-temperature melting process (650 DEG C to 760 DEG C); (4) forming a high-temperature conversion film containing rare earths during a high-temperature homogenization and deterioration process (760 DEG C to 840 DEG C), thereby effectively inhibiting high-steam pressure metal elements such as Mg, Zn and the like in the alloy from being volatilized. According to the forming method of the chemical conversion film of the Mg alloy, the precision of designed elements is effectively ensured. Thus, the prepared Mg alloy has excellent comprehensive performances of high strength (greater than 350MPa), high toughness (the elongation is greater than 20%), low density, good corrosion resistance and fire resistance, and the like.

Description

technical field [0001] The invention relates to a metal material and the field of metallurgy, in particular to a method for forming a chemical conversion film of a molten magnesium alloy. Background technique [0002] Magnesium alloys have broad application prospects in aerospace, military, electronics, machinery, automobiles and other industries, mainly due to their low density, impact resistance, excellent electromagnetic shielding performance, high specific strength and rigidity, and good machinability Features. Our country vigorously develops the magnesium alloy industry, not only has a strong resource advantage, but also has a huge market demand. [0003] However, in recent years, magnesium alloys have replaced aluminum alloys and other materials, and the application development in various industries has been relatively slow. The main reason is that magnesium alloys still have the following obvious shortcomings: [0004] (1) Low strength: At present, the tensile stren...

AI Technical Summary

Problems solved by technology

[0004] (1) Low strength: At present, the tensile strength of commercial magnesium alloys is less than 280MPa, especially the high-temperature mechanical properties are poor. When the temperature rises, its strength and creep resistance decrease greatly, which limits its application in structure, load-bearing, etc. applications in the field;

[0005] (2) Poor plasticity: At present, the elongation of commercial magnesium alloys is generally less than 10%, which limits its processing and forming properties

If the strength is increased, the elongation will be greatly reduced. For example, the highest strength ZK61 magnesium alloy, although its strength can reach 275-305MPa, its elongation is only 4-7%;

[0006] (3) High chemical activity, easy to oxidize and burn, difficult to form by thermal processing;

[0007] (4) Poor corrosion resistance: the substrate is easily oxidized in the air, and is easily corroded in a humid atmosphere

(5) Poor thermal strength: Magnesium alloys that have undergone solid solution-aging treatment cannot be used in an environment higher than 120°C for a long time due to the accumulation and growth of aging precipitates.

[0008] (5) Due to the high vapor pressure of magnesium, it is very volatile during smelting, which will not only pollute the environment, but also increase the risk of production

At present, it is generally used to use F 6 S+N 2 (Ar) for protection, although this method can achieve better results, but F 6 S pyrolysis will produce toxic decomposition products F 2 S, this decomposition product will not only cause serious pollution to the production environment, but more importantly, cause damage to the health of production personnel. Foreign countries have explicitly banned the use of F 6 S as protective gas medium