Effect Of Pre-deformation Aging Process On Microstructure And Mechanical Properties Of TA15 Titanium Alloy

TA15 titanium alloy has the advantages of both α-type and α + β-type titanium alloys.It has good plasticity,high creep resistance and long-term strength at high temperature.It can work for 3000 h at 500 °C for a long time,and has a wide application prospect in the aerospace field.However,at present,the requirements for the comprehensive mechanical properties of titanium alloys are getting higher and higher.The traditional solution aging process can improve the strength but the plasticity decreases more,and the strength-plasticity matching is poor.In this paper,pre-deformation before aging is used to change the aging precipitation behavior of the alloy,and the purpose of improving the strength and toughness of the alloy is achieved by regulating the microstructure.Taking TA15 titanium alloy as the research object,the effects of rolling pre-deformation at different temperatures(500 °C and 900 °C)on the microstructure and mechanical properties of TA15 titanium alloy were studied.The effects of different pre-deformation methods(rolling pre-deformation and tensile pre-deformation)on the microstructure and mechanical properties of TA15;the effect of rolling pre-deformation on different initial structures(bimodal structure,equiaxed structure and widmanstatten structure).The results show that the primary α phase of the alloy after rolling deformation at different temperatures is greatly reduced.The higher the rolling deformation temperature is,the more the reduction is,and there is less secondary α phase precipitation.Rolling predeformation promotes the precipitation of secondary α phase during aging.The tensile properties of the alloy rolled at 500 °C are the best.Compared with the solid solution aging alloy,the tensile strength is increased by 15.9 %,the yield strength is increased by 22.5 %,and the elongation is 12.9 %.At 500 °C,compared with the solution-aging alloy,the tensile strength increased by 22.4 %,the yield strength increased by 28.9 %,and the elongation increased by 15.8 %.The strengthening effect of pre-deformation temperature at 500 °C on the alloy is better than that at 900 °C.The alloy after rolling deformation changes from equiaxed structure to bimodal structure.After tensile deformation,the equiaxed primary α phase of the alloy becomes a long strip αphase,and many granular α phases appear in the β matrix and are arranged in a certain direction.Compared with the solid solution aging alloy,the tensile strength of the rolled alloy at room temperature is increased by 15.1 %,the yield strength is increased by 19.4 %,and the elongation is 11.7 %.At 500 °C,compared with the solid solution aging alloy,the tensile strength increased by 11.2 %,the yield strength increased by 26.5 %,and the elongation was14.3 %.The strengthening effect of rolling pre-deformation on the alloy is better than that of tensile pre-deformation.The microstructure of TA15 titanium alloy with widmanstatten structure is transformed into basketweave structure at room temperature after rolling deformation,and a small part of lamellar α phase is transformed into equiaxed α phase.Compared with the solid solution aging alloy,the tensile strength at room temperature of the alloy after rolling deformation is increased by 29.3 %,the yield strength is increased by 34.7 %,and the elongation is 8.9 %.At 500 °C,the tensile strength increased by 44.1 %,the yield strength increased by 48.1 %,and the elongation was 11.9 %.The pre-deformation aging process has a significant improvement effect on three different initial microstructure alloys.