Effect of rolling process on Microstructure and mechanical properties of Ti-62A titanium alloy plate
Ti-62A alloy is a kind of alpha + beta type titanium alloy, belonging to Ti-Al-Sn-Zr-Mo-Si-X alloy. The alloy is a kind of high strength and high toughness Damage Tolerance Titanium Alloy Based on Ti-62222S alloy and through rational composition design. At present, titanium alloys belong to damage tolerance type, such as TC4ELI, Ti-62222S and TC11DT. The yield strength of TC4ELI is 900MPa, which belongs to moderate strength damage tolerant Ti alloy. The yield strength of the other 2 kinds of alloy is 1000MPa, which belongs to high strength damage tolerance titanium alloy. Among them, TC4ELI and Ti-62222S alloys have been widely applied to the fourth generation fighter F-22 in the United states.
The researchers obtained Ti-62A alloy thick plate by two kinds of rolling process, and compared the microstructure and properties of the alloy plate in order to provide reference for the thick plate production of the alloy.
The test titanium alloy is smelted by 3 vacuum self consumption smelting. The chemical composition is controlled by nominal component. The metallography measured alpha + beta, beta phase transition temperature of 970 DEG C + 5.
The beta phase ingot forging into 200 ~ 250mm thickness of the slab, then divided into two kinds: process of rolling process of A: two-phase region open billet, rolling process of two-phase region to 40mm; B: Open Beta billet, two-phase treatment, two-phase region rolling to 40mm. After rolling in two processes, the sample is treated by 750 /2hAC heat treatment, and the properties of the sample are tested.
The experimental results show that the microstructure of the wrought alloy has been transformed into uniform and fine equiaxed structure after the alloy has been opened in two phase zone. After rolling to 40mm by A, the total deformation increases further, and the equiaxed structure is even and small, which is typical equiaxed structure. The rolling process of B to 40mm, beta grains were broken during deformation, the grain in the alpha sheet becomes shorter, the alpha layer staggered form lamellar structure. Due to the small amount of deformation after beta treatment, there is an incomplete Beta grain boundary. After 750 /2h AC heat treatment, the microstructure of the sheet changed little.
When the sheet is rolled by process A, the tensile strength reaches 1138Mpa and the elongation is 19%, all higher than that of the process B rolling plate. After the process B rolling, the impact toughness value of the sheet is highest, which is 39J/cm2. The strength and plasticity of the sheet with A are higher, but the impact toughness is lower. After 750 /2h AC heat treatment, the strength, plasticity and impact toughness of sheet metal all decreased.
