1. The practical application of magnesium alloys is the most structural material material, but the structure, but the alloy alloy alloy alloy
At present, the production of magnesium alloys and aluminum alloys is the largest application of magnesium alloy structures. The use is extremely easy to oxidize and burn during smelting and processing.
, magnesium alloy magnesium alloy is very; It is relatively used in high temperature, high temperature and high temperature occasions; the properties of magnesium alloys, magnesium alloys, magnesium alloys, performance properties, performance properties, performance properties, normal temperature mechanics, especially strength and Plasticity and toughness Plasticity and toughness need to be further improved. Research and development are seriously lagging behind and cannot meet the requirements of different applications.
Magnesium alloys can be divided into cast magnesium alloys and wrought magnesium alloys. Magnesium alloys mainly include Mg-Al-Zn-Mn series (Az), Mg-Al-Mn series (AM) and Mg-Al-Si-Mn series (As), Mg-Al-RE series ( AE), Mg-Zn-Zrn (ZK), Mg-Zn-RE series (ZE) and other alloys. my country is rich in magnesium resources, and the capacity, output and export of primary magnesium rank first in the world.
In the field of research and application of magnesium and magnesium alloys, the gap between my country and developed countries such as Europe and the United States is still quite large. On the one hand, the quality of raw magnesium in my country is poor, the quality of magnesium alloy ingots is not satisfactory, and the export is not competitive. , the domestic consumption of magnesium used as a structural material is very small, and it can only be exported as a primary raw material at a low price. , my country’s research and application of magnesium alloys is even weaker. Therefore, it is an urgent task before us to take advantage of the advantages of magnesium resources in our country, transform the advantages of magnesium resources into technological and economic advantages, promote the development of the national economy, and enhance the international competitiveness of my country’s magnesium derivative industry.
2. New developments in magnesium alloys
(1) Heat-resistant magnesium alloys. Poor heat resistance is one of the main reasons hindering the widespread application of magnesium alloys. When the temperature rises, its strength and creep resistance decrease significantly, making it difficult to be used as a material for key parts (such as engine parts) in industries such as automobiles. be more widely used. The alloying elements used in the developed heat-resistant magnesium alloys mainly include rare earth elements (RE) and silicon (Si). Rare earth is an important element used to improve the heat resistance of magnesium alloys. Rare earth-containing magnesium alloys QE22 and WE54 have high-temperature strength comparable to aluminum alloys, but the high cost of rare earth alloys is a major obstacle to their widespread application. Mg-Al-Si (AS) alloy is a die-casting magnesium alloy developed by German Volkswagen. At 175℃, the creep strength of AS41 alloy is significantly higher than that of AZ91 and AM60 alloys.
However, due to the formation of coarse Chinese-character-shaped Mg2Si phases in the solidification process of AS series magnesium alloys, the casting performance and mechanical properties are damaged. The study found that the addition of a small amount of Ca can improve the morphology of the Chinese character-shaped Mg2si phase, refine the Mg2si particles, and improve the microstructure and properties of the AS series magnesium alloys. Since the 1980s, foreign countries have devoted themselves to using C to improve the high temperature tensile strength and creep properties of magnesium alloys. ZAC8506 (Mg-8Zn-5Al-0.6Ca) recently developed in the United States, and magnesium alloys such as Mg-5Al-0.8Ca researched in Canada, have good tensile strength and creep properties. In 2001, Akihisa Inoue of Tohoku University in Japan, etc., made a high-strength magnesium alloy Mg-2at% Y-1at% Zn with a grain size of 100-200nm by the rapid solidification method. Its strength is three times that of super aluminum alloys, and it also has superplasticity. , High heat resistance and high corrosion resistance.
(2) Corrosion-resistant magnesium alloy. The corrosion resistance of magnesium alloys can be solved in two ways: ① Strictly limit the content of Fe, Cu, Ni and other impurity elements in magnesium alloys. For example, the corrosion resistance of high-purity AZ91HP magnesium alloy in the salt spray test is about 100 times that of AZ91C, surpassing the die-casting aluminum alloy A380, and much better than low-carbon steel. ② Surface treatment of magnesium alloy. According to different corrosion resistance requirements, chemical surface treatment, anodic oxidation treatment, organic coating, electroplating, electroless plating, thermal spraying and other methods can be selected. For example, the corrosion resistance of electroless-plated magnesium alloy exceeds that of stainless steel.
(3) Flame-retardant magnesium alloy. Magnesium alloys are prone to violent oxidative combustion during smelting and casting. Practice has proved that the flux protection method and SF6, SO2, CO2, Ar and other gas protection methods are effective flame retardant methods, but they will cause serious environmental pollution in application, reduce the performance of the alloy, and increase the investment in equipment. Adding calcium to pure magnesium can greatly improve the anti-oxidative combustion ability of magnesium liquid, but because adding a large amount of calcium will seriously deteriorate the mechanical properties of magnesium alloys, this method cannot be applied to production practice. Hinge can prevent further oxidation of magnesium alloy, but when the content of hinge is too high, it will cause grain coarsening and increase the tendency of hot cracking.