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 in?-phase stabilizing elements developed from Ti-6Al-4V(TC4)alloy.Compared with TC4 alloy,the content of?-phase stabilizing element V is increased,and the?-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?.The?_p phase content decreased with increasing annealing temperature,the?phase volume fraction increased,and the?phase grain size became larger.No?_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 martensitic??phase appears on the?-transformed microstructure.As the solution temperature rises,the?-phase grain size becomes larger.The volume fraction increases,and the??phase becomes coarser and longer.When the solution temperature exceeds the?phase transition temperature(T_?),the?_p phase and the??phase disappear,and the alloy microstructure is all coarse acicular hexagonal martensite?phase.After the solution treatment sample was further aged at 540?,?_s and?phases were precipitated in the?phase transformation structure.As the solution temperature increased,the volume fraction of the?_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 the?_s phase contributes to the strength more than the weakening effect of the increase in size;the decrease in the?_p phase leads to a decrease in plasticity.When the solution temperature exceeds T_?,because The coarse?phase 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 the?_s phase increases,and the strength of the alloy decreases.As the volume fraction of the?_s phase does not change significantly,the increase in the?_s phase size weakens the strength.In addition,the increase in the?_s phase size causes dislocation slip Increased moving distance and improved plasticity.