Microstructure Evolution Simulation Of ?20C Titanium Alloy During The Heat Treatment Based On Phase-field Method

Due to the excellent the dynamic strength and plasticity,titanium alloys have been widely used in the missile warhead field.?20C titanium alloy,which is independently developed by Beijing Institute of Technology,has a good match of dynamic strength and plasticity when carried superfine equiaxed grains by means of heat treatment process properly.At present,it's still unclear that the formation mechanism of the superfine-equiaxed microstructure of ?20C titanium alloy,and the stability of the heat treatment process remains to be improved.In this paper,the microstructure evolution of?20C titanium alloy during the heat treatment was simulated by phase field method.It is well known that the microstructure evolution simulation can reduce consumptions,predict solidified microstructure and evolution by fewer experiments,obtain the relationship between heat treatment processing parameters and the microstructures,so as to optimize them.(1)In order to establish the phase field model of the heat treatment process of ?20C titanium alloy,the thermodynamic parameters such as entropy,Gibbs free energy and driving force are calculated by using the Thermo-Calc software.At the same time,a new method was established for the calculation of ?/? interface mobility,respectively,by 1013 K and 1513 K insulation experiment.(2)By analyzing and optimizing the experimental results of two typical heat treatment processes,the phase field model of ?20C titanium alloy was obtained.By comparing the simulation results with the experimental results,the established phase field model was validated and optimized.The microstructure of double-annealing process was simulated,and the simulation results and experimental results were 63.66% and 61%,respectively,and the maximum difference was 4.19%.The microstructure of typical heat treatment process is simulated.The phase compositions of phase field and experiment results were in good agreement with the time variation curve.At last,the content of phase is 54.20% and51.50% respectively.(3)Based on the phase field model of ?20C titanium alloy,the influence of heat treatment parameters was studied.The effection of heating rate and temperature onmicrostructure of ?20C titanium alloy was analyzed.The distribution of Al elements in the process of heating was studied by coupling the concentration field.