| TC4 titanium alloy is an ?+? two-phase titanium alloy similar to Ti-6Al-4V in the United States.Due to its good corrosion resistance,high strength ratio and good corrosion resistance,it is widely used in aerospace and other industrial fields.In this paper,the hot deformation properties of TC4 titanium alloy during deformation process were studied by Gleeble hot compression test.Titanium alloy has the disadvantages of narrow processing window,poor thermal conductivity,and easy oxidation at high temperature,which makes it difficult to shape rolling.if using the traditional experimental method to solve the problem of shape rolling of titanium alloy,it will consume considerable time and money,and the traditional experiments can not accurately obtain the stress,strain and temperature data of various parts of the billet during the rolling process.The finite element thermo-mechanical coupling system can replace the physical experiment to simulate the rolling process,and through the analysis of the results,the process parameters can be optimized and the metal properties can be predicted.At the same time,it can reduce costs and improve efficiency.In this paper,the finite element software Deform-3D was used to study the forming law of TC4 titanium alloy thin-walled shape rolling.The true stress-true strain curve of TC4 below the phase transition point is dynamic recrystallization type,the true stress-true strain curve near and above the phase transition point is dynamic recovery type.High temperature rise of materials is found at low temperatures.The larger the strain rate and degree of deformation,the smaller the grain size,the smallest grain size is in the 900?920? range,and the grain distribution is more uniform in this temperature range.The constitutive equation of TC4 titanium alloy with peak stress ?p as the characteristic value is established by regression processing of the hot compression data,based on the Sellars-Tegart constitutive model.The material constant values A,n,? and activation energy Q at different strains were calculated.The nonlinear fitting of them was used to obtain the constitutive equation of TC4 titanium alloy considering the strain.The average errors of the calculated and experimental values of the two constitutive equations are verified to be 10.11%and 9.9%,respectively.The hot working diagram of TC4 titanium alloy is obtained.The hot working range of TC4 titanium alloy is 850?1000?,and the strain rate is less than 1s-1.The instability zone is mainly distributed in the low temperature zone below 850? and the high strain rate zone near the phase transition point.The finite element model of the 13th pass shape rolling of TC4 titanium alloy with high precision is established.The simulation results show that the K8 pass longitudinal rolling plays an important role in the improvement of the temperature distribution of the rolling stock:K13-K9 pass rolling,The temperature rise on the side of the rolling stock is serious,and the temperature gradient in the central part is large.The temperature distribution after K8 pass rolling is obviously improved.The rolling stress of the first few passes is concentrated on the surface.The stress distribution is gradually uniform with the rolling times.The largest part of the strain is the 1/4 width of the rolling piece,the surface strain is larger than the internal strain;The material damage law of the rolling process was obtained,and it was predicted that material damage occurred at the edge of the material in K2 and K1 pass thin wall rolling.A suitable rolling speed of 3 rad/s was determined,at which the rolling process temperature was maintained above 850?,in the safe processing area shown in the hot working diagram. |
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