Effect of heat treatment on microstructure and properties of TC11 titanium alloy

The effects of heat treatment temperature and cooling mode on the microstructure and mechanical properties of TC11 titanium alloy with equiaxed initial microstructure were studied. The results show that for TC11 titanium alloy, the content of equiaxed α phase decreases gradually with the increase of heat treatment temperature under air cooling condition. When the heat treatment temperature exceeds 980℃, the microstructure of the alloy begins to change from the initial equiaxed state to the α+β two-state structure, and the equiaxed structure completely transforms into lamellar structure with the increase of temperature. When the heat treatment temperature is above 980℃, the lamellar thickness of β transition structure gradually decreases with the increase of cooling rate, and the quenched martensite is formed when the cooling rate is faster (water cooling). The tensile test results show that the microstructure obtained at 980~1020℃ and air-cooled (or oil-cooled) has better comprehensive mechanical properties at high temperature. The microstructure obtained at 980~1000℃ has the best mechanical properties due to the equiaxed α-phase content of about 50%.

Microstructure analysis of TC11 alloy under different heat treatment conditions

Abstract: The microstructure of TC11 alloy samples under different heat treatment conditions was observed by metallographic microscope, and the results were analyzed. The microstructure of TC11 alloy obtained by different heat treatments is obviously different. After heating at 950℃ for 1 h and then heating at 550℃ for 4h, the microstructure of TC11 alloy is a small amount of massive α phase, β phase and fine α phase. After heating and holding at 950℃ for 1 h and then oil cooling, and then heating at 550℃ for 4 h and air cooling, the microstructure obtained is fine needle-like α and β phases.

Effect of high temperature deformation behavior and heat treatment process on microstructure and properties of TC11 titanium alloy

Wang Jinhui

[Abstract] : TC11 titanium alloy is the best thermal strength alloy under 500℃, with high specific strength, good medium temperature performance, good corrosion resistance and other advantages, has been widely used in the field of aerospace, mainly used in the manufacture of compressor disc, blade, annular parts and fasteners and other parts and aircraft structural parts. In this paper, by means of optical microscopy, X-ray diffractometry, scanning electron microscopy, energy spectrum analyzer, transmission electron microscopy, tensile mechanical property test and thermal simulation test, the influence of high temperature deformation behavior and heat treatment process on the microstructure and properties of TC11 titanium alloy was studied. The main research results are as follows: (1) The thermal deformation behavior of TC11 titanium alloy was studied by thermal/compressive simulation test. The INFLUENCE OF HOT DEFORMATION PARAMETERS ON THE FLOW STRESS OF THE ALLOY DURING HIGH TEMPERATURE PLASTIC DEFORMATION WAS ANALYZED, AND THE MATERIAL CONSTANT OF THE ALLOY DURING HIGH TEMPERATURE deformation WAS OBTAINED BY COMBINING WITH THE STRESS-strain curve OF hot compression deformation, AND THE FLOW stress constitutive equation OF the alloy during high temperature deformation was established. The results show that the deformation resistance of the alloy decreases with the increase of deformation temperature and increases with the increase of strain rate. With the increase of deformation temperature, the flow stress softening amplitude of the alloy decreases, the corresponding peak strain εp decreases gradually, and the time to start dynamic softening also decreases. (2) The deformation mechanism during high temperature plastic deformation of TC11 titanium alloy was studied, and the relationship between the hot deformation conditions and the deformed microstructure was analyzed. The results show that the softening mechanism of TC11 titanium alloy is mainly dynamic recrystallization when it is deformed in α+β phase region. In the β-phase region, the main softening mechanism is dynamic recovery, with a certain degree of dynamic recrystallization at higher strain rates. With the decrease of strain rate, the size of α phase gradually increases and the proportion of α phase gradually decreases. With the increase of deformation temperature, the primary α phase gradually coarsenes and turns into β phase, and its proportion decreases. (3) The effects of solution temperature, solution time, aging temperature and aging time on the mechanical properties and microstructure of TC11 titanium alloy at room temperature were investigated by orthogonal test. The results show that solution temperature has the greatest effect on the strength and plasticity of the alloy at room temperature, followed by aging time, while solution time and aging temperature have no significant effect. With the increase of solution temperature, the strength level of the alloy gradually decreases, and the elongation and section shrinkage of the alloy increase first and then decrease. The highest ductility can be obtained at 960℃. With the extension of aging time, the strength of the alloy decreases first and then increases. The highest strength can be obtained at 4 hours of aging, while the plastic shape of the alloy gradually increases and remains unchanged after a certain time. High plasticity can be obtained at 6 hours and 8 hours. Using the heat treatment system of 960℃/30min(AC)+530℃/8h(AC),TC11 titanium alloy can get the optimal strong plastic combination, with tensile strength of 1140MPa, yield strength of 1048 MPa, elongation of 18.72%, and section shrinkage of 54.90%. (4) The high temperature tensile test of TC11 titanium alloy samples after heat treatment by different processes shows that the tensile strength increases with the solution temperature, the yield strength is basically unchanged, while the elongation and fracture expansion rate increase first and then decrease. With the aging time, the tensile strength decreases, while the elongation and fracture expansion increase. After heat treatment at 960℃,30min+560℃ and 8h, the optimal high temperature tensile properties of TC11 titanium alloy can be obtained. The mechanical properties of TC11 titanium alloy after high temperature tensile at 500℃ are σB =805 MPa,σ0.2=667MPa,δ=22.09%, ψ =69.67%.

[Key words] : TC11 titanium alloy high temperature compression orthogonal test high temperature tensile mechanical properties microstructure heat treatment