In aerospace industry, alloys have become the engineering materials of great concern due to their high strength and easy welding. By analyzing the application of niobium alloy, aluminum lithium alloy, titanium aluminum alloy and magnesium alloy in aerospace engineering, this paper reveals the irreplaceable role of alloy materials in this field, and points out the deficiency of the alloy and the improvement measures. At the same time, the author thinks that the future development direction of alloy is light weight, and puts forward to carry on the technical treatment to the existing alloy, and promote the development of alloy.
Niobium is located in the VB group in the fifth period of the periodic table. Niobium is a gray - white metal with stable chemical properties, paramagnetic properties, high melting point and low density. It can be directly combined with sulfur, carbon and other elemental materials at high temperature, and can form alloys with titanium, zirconium, tungsten and other metals, which can be used as new aerospace engineering materials. Niobium alloys are divided into high-strength niobium alloys and low-density niobium alloys.
Solid solution strengthening and dispersion strengthening are the main methods. Generally, tungsten, molybdenum, hafnium and 0.06%-0.12% carbon are added for solid solution strengthening. The alloy strengthened by solid solution has high strength at high temperature and is an ideal material for aerospace engineering. However, as niobium hardens with the increase of impurity content, the plasticity at room temperature is poor (elongation after fracture ≤10%). For this purpose, we generally add a large amount of hafnium and a small amount of carbon to make WC3009 niobium alloy. In addition, we can use the method of dispersion strengthening to solve this problem. In the process of dispersion strengthening, 5%-10% molybdenum or tungsten are generally added, so that the plasticity of the alloy is greatly improved, the elongation after fracture is ≥25%, and the characteristic of high specific strength is not lost.
Low density niobium alloy, which has better oxidation resistance than niobium alloy with high niobium content (mass fraction Nb+W > 80%), can not be oxidized without any antioxidant coating in the atmosphere of 550℃ to 800℃. There are many preparation methods of low density niobium alloy, such as powder metallurgy and plasma smelting. Compared with other methods, powder metallurgy can easily obtain alloy materials with very uniform composition. With the continuous development of science and technology, 3D printing technology is becoming more and more mature. It can become a new research direction to prepare alloys with complex shapes by using this technology.
