Research On Control And Simulation Of Microstructure During Hot Deformation For Titanium Alloy TC21

Titanium alloy TC21 is a alloy which has important application in aviation. In this paper, using the lamellar microstructure as the research object,combined the processing map technology with FEM, the change and development of unstable deformation microstructure and dynamic recrystallization microstructure was simulated and predicted during the hot compression of titanium alloy TC21 at different deformation condition, and the critical condition model of the dynamic recrystallization was established.By this method,the hot processing parameters could be optimizated in actual foring process and had certain practical guiding value for good performance foring.Using the hot compression experiment data, the instability map of titanium alloy TC21 was plotted in light of Murty unstable criterion and the boundary condition of hot deformation parameter for unstable deformation microstructure was determined. Combining the boundary condition with the finite element software of Deform-3D,and twice development of this finite element software, the appearance and change of unstable deformation microstructure was simulated and predicted at the deformation condition of 820℃/0.001s-1~0.1s-1during the hot compression process, and the distribution of hot deformation parameters in the sample was analyzed.The results shows that: when the deformation condition was 820℃/0.001s-1,it was stable microstructure during whole hot compression process; when the deformation condition was 820℃/0.01s-1~0.1s-1, the unstable deformation microstructure was obtained at the end of the compression stage. It was shown that the unstable deformation area and the stable deformation area which was obtained by instability map, could not be directly used to guide the actual production, especially in the stable deformation area of the nearby boundary condition of the hot deformation parameter, the unstable deformation microstructure could be produced easyly in this area. The microstructure observation showed that the simulation results are in good agreement with the experimental results.Using the hot compression experiment data, the power dissipation map of titanium alloy TC21 was plotted and the dynamic recrystallization critical strain condition model was established under different deformation conditions. Combining this modle and the boundary condition of hot deformation parameter for dynamic recrystallization deformation microstructure which was determined by power dissipation map, then imported this result into a finite element software of Deform-3D, and twice development of this finite element software, the appearance and change of dynamic recrystallization deformation microstructure was simulated and predicted at the deformation condition of 880℃/0.01s-1~1s-1during the hot compression process, and the distribution of hot deformation parameters in the sample was analyzed. The results shows that: when the deformation condition was 880℃/0.01s-1,the dynamic recrystallization microstructure was obtained during compression; when the deformation condition was 880℃/0.1s-1~1s-1,the non dynamic recrystallization microstructure was obtained during compression.Although the deformation conditions(880℃, 0.1s-1)was occurred the globalization phenomenon in the early stage of compression,which was beyonded the boundary condition of hot deformation parameters for dynamic recrystallization deformation microstructure, the non dynamic recrystallization(globalization) deformation microstructure was mainly obtained at the end of compression. The reliability of the simulation was verified by the microstructure observation.