Effects Of Heat Treatment Process On Microstructure And Tensile Properties Of Ti662 Alloy

Ti662 alloy has a nominal composition of Ti-6Al-6V-2Sn-0.5Fe-0.5Cu,which is a two-phase high-strength titanium alloy rich inβ-phase stabilizing elements developed from Ti-6Al-4V(TC4)alloy.Compared with TC4 alloy,the content ofβ-phase stabilizing element V is increased,and theβ-phase stabilizing elements Fe and Cu are added,thereby increasing the hardenability of the alloy,which can make its hardened thickness to 38.1~50.4 mm.The engineering application makes up the shortcomings of poor hardenability of TC4 alloy.In addition,the alloy also adds the neutral element Sn,which can increase its application temperature to 315℃.This article takes Ti662 alloy as the research object,systematically studies the effects of annealing,solid solution and aging heat treatment processes on the microstructure and tensile properties of the alloy,and analyzes the reasons for the effects of different heat treatment systems on the microstructure and tensile properties.It helps to increase the theoretical research value of the alloy and has guiding significance for engineering applications.The effects of annealing temperature on the microstructure and tensile properties of Ti662 alloy were studied,and the reasons were analyzed.The results showed that the microstructures of the samples were all equiaxed after annealing at 680~770℃.Theα_p phase content decreased with increasing annealing temperature,theβphase volume fraction increased,and theβphase grain size became larger.Noα_s phase was observed in any of the phases.As the size of both phases becomes larger,the tensile strength of the sample decreases with increasing temperature.Due to the full recovery and recrystallization of the two phases,the plasticity slightly increases.The effect of solution temperature change on the microstructure and tensile properties of Ti662 alloy was studied,and the reason was analyzed.The results show that after solid solution at 860℃,fine needle-shaped orthorhombic martensiticα″phase appears on theβ-transformed microstructure.As the solution temperature rises,theβ-phase grain size becomes larger.The volume fraction increases,and theα″phase becomes coarser and longer.When the solution temperature exceeds theβphase transition temperature(T_β),theα_p phase and theα″phase disappear,and the alloy microstructure is all coarse acicular hexagonal martensiteαphase.After the solution treatment sample was further aged at 540℃,α_s andβphases were precipitated in theβphase transformation structure.As the solution temperature increased,the volume fraction of theα_s phase increased after aging treatment,and the size became coarser and longer.Tensile properties increase with increasing solution temperature.This is because the increase in the volume fraction of theα_s phase contributes to the strength more than the weakening effect of the increase in size;the decrease in theα_p phase leads to a decrease in plasticity.When the solution temperature exceeds T_β,because The coarseβphase transformation structure causes the tensile properties of the alloy to decrease sharply and brittle fracture occurs.The effects of aging temperature changes on the microstructure and tensile properties of the solid solution(900℃/1 h/WQ)Ti662 alloy were studied,and the reasons were analyzed.The results show that as the aging temperature increases,the sheet thickness of theα_s phase increases,and the strength of the alloy decreases.As the volume fraction of theα_s phase does not change significantly,the increase in theα_s phase size weakens the strength.In addition,the increase in theα_s phase size causes dislocation slip Increased moving distance and improved plasticity.