Effect Of Heat Treatment On Microstructure And Mechanical Properties Of High Strength β Titanium Alloy Sheets

Titanium alloy has good properties of high specific strength, excellent corrosion resistance, heat-and-cold resistance and other properties, which has become the very promising application and potential development as the structural material using in aerospace. Compared with the α+β titanium alloy, β titanium alloy has more excellent deep hardening ability and cold workability and easily to forge, suitable for the production of sheet metal structure and large forgings. With the rapid development of the β titanium alloy in the aerospace industry, national development for new high-strength β titanium alloy causes more and more attention. In this paper, the new type β titanium alloy of Ti-3.5Al-5Mo-6V-3Cr-2Sn-0.5Fe as the research object to study the effects of different heat treatment process on microstructure and mechanical properties of high strength β titanium alloy.High strength titanium alloy plate by rolling temperature of 790℃ and 870℃ after solution treatment, found that the alloy in the(α+β) two-phase region and the β single phase solution treatment with high strength and excellent plasticity. When solution temperature below the phase transformation point, grain boundary precipitates the packed hexagonal structure of the primary alpha phase, which limits the growth of beta grains, with the solution temperature rising to β single-phase region, the primary alpha phase with strong effect will disappears and the single beta phase grain size is larger. The alloy in the(α+β) two-phase region after solution treatment the strength and plasticity of matching is obviously stronger than that of single-phase region.The high strength β titanium alloy during the aging process from 400 to 600℃, the secondary alpha phase precipitated in the grains, significantly improves the strength of the alloy, the volume fraction of the secondary alpha phase will decreases as the aging temperature increases, while the size of the secondary alpha phase will gradually increase, and the strength of the alloy will decreases with the increase of aging temperature, on the contrary, its plasticity increases.By analyzing the heat-treated property of the high-strength titanium alloy which rolled in 790℃ and 870℃, found that the alloy after solution treated at(α+β) field and different temperature aging obtained a good match of strength and ductility, which obviously better than solution treated at β field, the solution temperature suitable choice in the(α+β) field; the property of the alloy which rolled in 790℃ and 870℃ after solution treated at(α+β) field and different temperature aging, found that the alloy which rolled of 790 ℃ receive a better match of strength and ductility, thence the rolling temperature should be under the phase transition temperature.