Study On Texture Evolution And Mechanical Property Optimization Of Titanium Cylindrical Part Formed By Spinning

The thin-walled titanium alloy tube is one of the important parts for the development of high-end equipment in the aerospace fileds.These components are usually formed by hot spinning.However,during the spinning process,the materials undergo complicated deformation states and significant non-uniform deformation,which results in obvious preferred orientation and creates a strong deformation texture.Finally,the components present significant mechanical anisotropy,which limits the high-performance manufacturing and wide applications of such components.Therefore,in this paper,in-depth studies on the evolution and optimization of texture and mechanical properties for TA15 titanium alloy during hot spinning were conducted by combination of experimental analysis,finite element simulation and theoretical analysis.The main contents and conclusions are as follows:(1)Based on the hot spinning tests,heat treatment tests,and texture simulation using viscoplastic self-consistent polycrystal plastic model,the texture evolution mechanism in the whole process of TA15 titanium alloy was revealed.It was found that the higher degree of basal sliding system in the multi-pass spinning process caused the {0002} poles to be angled toward the radial direction of the cylindrical part.The rotation ratio of prism and pryam slip systems increases first and then decreases,which makes the angle between {0002} poles and radial direction increases first and then decreases,and finally formed the non-standard basal texture.In addition,with the increase of forming passes,the dominant mechanism of recrystallization changes from discontinuous dynamic recrystallization to continuous dynamic recrystallization,which strengthens the basal texture component.During the annealing process,with the increase of spinning deformation passes and annealing temperature,the dominant recrystallization mechanism changed from discontinuous static recrystallization to continuous dynamic recrystallization.The type of annealing texture is similar to that of deformation texture,but its texture intensity decreases significantly.(2)The texture and mechanical properties evolution and their mechanisms under different process parameters were revealed by plane strain tests.It was found that the non-standard basal texture of titanium alloy always exists under different processing conditions,but its intensity depens on the slip system activation and microstructure evolution during deformation.With the increase of deformation amounts,the activation degree of pyram<a+c>slip system increases,and more discontinuous static recrystallization grains are formed during heat treatment,which makes the angle between the {0002} pole and the radial direction of titanium alloy decreases first and then increases.The increase of deformation temperature benefits to the pyram<a+c>slip,and the discontinuous static recrystallization grains is more obvious during heat treatment.These phenomena make the angle between the {0002} pole and the radial direction of titanium alloy increases.In addition,the higher heat treatment temperature will promote the phase transition.These phenomena make the more dispersive texture.The increase of strain rate can facilitate the activation of other slip system except for the basal slip system,and the main recrystallization mechanism changes from continuous to discontinuous static recrystallization,which significantly enhances the dispersion degree of texture.With the increase of heat treatment temperature,the number of continuous static recrystallized grains increase,which leads to the angle between the {0002} pole and the radial direction of titanium alloy increases.The anisotropy degree of the samples increases with the deformation amount and temperature increasing,while it decreases with the heat treatment temperature decressing and the strain rate increasing.(3)Based on NSGA-II algorithm,the process parameters of titanium alloy hot spinning was optimized.By using grey relational analysis,the correlation between the process parameters and the texture and mechanical properties of titanium alloy was determined.Then based on regression analysis,the correlation model beteween process conditions and texture as well as mechanical properties was established.Aiming at the minimum texture intensity and mechanical anisotropy,several groups of process parameters was obtained by NSGA-II algorithm,and the reliability of optimized parameters was verified by regression equation.In this paper,theoretical analysis,experimental research and numerical simulation were used to systematically analyze the evolution law and mechanism of the texture in the whole process of thermal strength spinning of titanium alloy,and then plane strain test was used to reveal the influence of various process parameters on the texture and mechanical properties,and finally complete the whole process optimization of thermal strength spinning of titanium alloy tubular parts.This paper has great significance for promoting the development of flow spinning forming technology and enriching advanced plastic forming theory and technology.