The Development Status of Rare Earth in Casting Aluminum Alloy
Abstract
Suitable rare earth (RE) elements have been developed and adopted in aluminum alloys for many years. This paper reviews the development of rare earth elements in aluminum alloys. The study found that rare earth elements can improve aluminum alloy properties such as strength, corrosion resistance, thermal stability, and plasticity. Although the amount of rare earth added to aluminum alloys is getting bigger and bigger, it still can’t meet the needs of some special products. Therefore, it is necessary to further study and optimize the alloys of rare earth and aluminum, it conducive to the development of aluminum alloy products.
1. Introduction
Aluminum alloy is a kind of metal raw material which has a wide range of applications in many fields such as aviation, military industry, chemical industry, and electric power. Its properties such as good thermal conductivity, high strength, good corrosion resistance, and easy processing and forming, have made it one of the most widely used materials in industrial production. In order to improve the performance of aluminum alloy, a lot of researchers have tried to optimize the composition of aluminum alloy by adding various elements. Rare earth elements are one of the additives which are developed and adopted most in aluminum alloy.
2. Rare earth elements in aluminum alloy
Rare earth elements are non-ferrous chemical elements with atomic number 57 to 71, which are generally referred to as lanthanide elements and yttrium elements. Rare earth elements mainly refer to lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb) and lutetium (Lu).
In the aluminum alloy, rare earth elements are usually added in a certain amount as alloy elements, so that the alloy performance is greatly improved. The addition of rare earth elements can promote the formation of alumina particles in aluminum alloy, which has a great effect on improving the performance of aluminum alloy. Rare earth elements can effectively improve the hot working performance, wear resistance, heat resistance and corrosion resistance of aluminum alloy [1], and can also reduce the hot brittleness of aluminum alloy and prevent the occurrence of intergranular corrosion.
3. Application of rare earth elements in aluminum alloy
3.1 Strength
Adding a certain amount of rare earth elements to aluminum alloy can significantly improve the strength, plasticity and hardness of aluminum alloy. With the addition of rare earth elements, the grain size of aluminum alloy will become finer, the strength of aluminum alloy will be improved, and the maximum deformation capacity of aluminum alloy will be increased [2]. The addition of rare earth elements to aluminum alloy can also significantly reduce the degree of recrystallization and grain growth at high temperature and make the aluminum alloy have better thermal stability.
3.2 Corrosion resistance
Rare earth elements can also effectively improve the corrosion resistance of aluminum alloy. Rare earth elements can react with trace impurity elements in aluminum alloy, forming compounds insoluble in water, thus preventing the micro-galvanic corrosion of aluminum alloy caused by trace impurities [3]. In addition, rare earth elements can also form dense surface films on the surface of aluminum alloy, which has a good protective effect on the aluminum alloy against corrosion.
3.3 Thermal stability
The addition of rare earth elements to aluminum alloy can effectively improve the thermal stability of aluminum alloy. Rare earth elements can form a dense protective film on the surface of aluminum alloy, which can effectively prevent the infiltration of molten aluminum into the micro-pore or porosity of aluminum matrix and prevent the occurrence of thermal embrittlement. In addition, rare earth elements can also react with impurity elements in aluminum alloy to form insoluble compounds, which can effectively prevent the formation of dendritic crystal structure in aluminum alloy and improve the thermal stability of aluminum alloy.
4. Conclusion
Due to its excellent performance, rare earth elements have been widely used in aluminum alloys. With the addition of rare earth elements, the properties of aluminum alloys can be significantly improved. Rare earth elements can effectively improve the hot working performance, wear resistance, heat resistance and corrosion resistance of aluminum alloy, and can also reduce the hot brittleness of aluminum alloy and prevent the occurrence of intergranular corrosion. Although the amount of rare earth added to aluminum alloys is getting bigger and bigger, it still cant meet the needs of some special products. Therefore, it is necessary to further study and optimize the alloys of rare earth and aluminum, it conducive to the development of aluminum alloy products.
