Application of rare earth elements in casting magnesium alloy

Magnesium alloy has the characteristics of low density, high specific strength, good rigidity, high modulus of elasticity, as well as good electromagnetic shielding and cutting performance, so it is widely used in aerospace and modern electronic industry.

Rare earth elements are located in the third group of periodic table. The outermost layer of atoms has the same electronic structure, and the second outer layer has similar electronic structure, similar chemical properties and active chemical properties. Both magnesium alloy and rare earth elements have close packed hexagonal crystal structure, which makes the solid solubility of rare earth elements in magnesium alloy larger. Almost all rare earth elements have a better solid solution strengthening effect on α – mg. The difference of atomic size radius between most rare earth elements and magnesium is within ± 15%. The solubility of various rare earth elements in magnesium is different. The order of increase is La, mixed rare earth, CE, PR, nd. Rare earth elements can enhance the bonding force between atoms of magnesium alloy and reduce the diffusion rate of atoms [1].

In recent years, due to the increasingly extensive application of magnesium alloy, the performance requirements of magnesium alloy are higher and higher, and the research on the influence of various elements on the performance of magnesium alloy has been carried out very carefully; due to the special role of rare earth in magnesium alloy, the research on the influence of rare earth on the structure and performance of magnesium alloy has also done a lot of work. Rare earth elements are widely used in magnesium alloys, especially in cast magnesium alloys. Rare earth elements are used as strengthening elements, fire-retardant elements, modifying agents, purifying agents and so on. At present, the application of rare earth in casting magnesium alloy is extensive, but the system is not strong, and the adding method of rare earth is not mature. Therefore, the application of rare earth in casting magnesium alloy is systematically summarized in this paper.

China is rich in rare earth resources, accounting for more than 80% of the world’s proven rare earth reserves. The application and development of rare earth is very important for the rational utilization of rare earth resources. Therefore, the development of high quality magnesium alloy materials containing rare earth has unique advantages in China. The high strength, heat resistance and corrosion resistance of rare earth magnesium alloy can not only further increase the application of magnesium alloy materials in the existing automotive industry, communication, electronic industry and other industries, but also promote the further development and utilization of magnesium alloy materials in the new field, and also open up a very broad field for the application of rare earth materials. Continuous improvement and improvement of the existing rare earth magnesium alloy, as well as the development of new rare earth magnesium alloy with low cost and good performance, will greatly promote the development of magnesium alloy materials and rare earth materials.

Compared with Japan, the United States and other developed countries, there is a considerable gap in the development and application of new rare earth materials in China, and the research on wrought magnesium rare earth alloys is still insufficient. The research on rare earth alloying is not mature in the world, and the mechanism of its action is still controversial. There are interactions between light rare earth and heavy rare earth elements, and between rare earth and impurity elements, It is necessary to further study the inhibition of element segregation, purification and metamorphism, the formation of GP region, precipitation hardening and precipitation strengthening.

The laboratory of light alloy, School of materials science and engineering, Harbin University of science and technology has made a series of researches on rare earth flame retardant cast magnesium alloy, rare earth heat-resistant cast magnesium alloy, rare earth high strength cast magnesium alloy and rare earth semi-solid formed magnesium alloy, and gained some experience.

However, at present, rare earth elements are still used as auxiliary elements, and their mass fraction is generally less than 11%. Furthermore, the alloying mechanism between rare earth elements, magnesium alloy and other elements (such as Ca, Zn, etc.) was studied, so as to develop a special magnesium alloy with the best alloy ratio. In recent years, the research of rare earth alloys has made great progress, and the application and development conditions of rare earth in magnesium alloys are gradually mature. With the excellent characteristics of rare earth magnesium alloys gradually accepted by people, its application market will be wider, and the development of high-quality magnesium alloy materials containing rare earth has unique advantages in China. The high strength, heat resistance and corrosion resistance of rare earth magnesium alloy can not only further increase the application of magnesium alloy materials in the existing automotive industry, communication, electronic industry and other industries, but also promote the further development and utilization of magnesium alloy materials in new fields, and also open up a very broad field for the application of rare earth materials. Continuous improvement and improvement of the existing rare earth magnesium alloy, as well as the development of new rare earth magnesium alloy with low cost and good performance, will greatly promote the development of magnesium alloy materials and rare earth materials.

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