Due to its high specific strength, light weight, wide operating temperature range and excellent corrosion resistance, titanium alloy has been widely used in aerospace industry. At present, the titanium alloy used in aerospace industry accounts for about 70% of the total production of titanium. High purity titanium has good plasticity, but when impurity content exceeds a certain amount, brittle compounds will be formed, which makes the plasticity of titanium alloy decrease sharply. The microstructure of titanium alloys is an important factor in determining the mechanical properties such as tensile strength, fatigue strength and fracture toughness. Its structure is mainly composed of and phase, and its structure can be divided into Weissner, net basket, two-state and isoaxial structure.
(1) Tensile properties
The coarse grains are generally distributed along the boundary of the original grains, and the coarse grains are generally located in the Weinberger structure and distributed in approximately parallel weinberger bars. General Weinberg structures are the least plastic at room temperature because they have very large grains. The two-state tissues are generally composed of relatively small primary phase and -transformed tissues. If the two-state tissues are obtained by "solid solution + aging" treatment, the tensile strength at room temperature is higher than that of the other three kinds of tissues.
(2) Fracture toughness and crack growth rate
Generally speaking, the fracture toughness of Weissner's structure is greater than that of equiaxial structure and two-state structure. The fracture toughness of the alloy is greatly influenced by the number and size of the primary phase. The fracture toughness increases with the decrease of the primary phase.
(3) Fatigue performance
Among the above four different types of tissues, the fatigue limit of equiaxial tissues is the highest, while that of Weissner tissues is the lowest. Secondly, for both low cycle fatigue and high cycle fatigue of the same alloy, the fatigue performance of two-state structure is the best, while the fatigue performance of Weissner structure is relatively poor.
