Research on hot deformation behavior and constitutive relation of diffusion bonded TC4 titanium alloy

摘要

To characterize the forming technology and service performance of diffusion bonded TC4 titanium alloy under high temperature, the isothermal constant strain rate tensile experimental were carried out at temperature 600-840 degrees C and strain rate 0.0001-0.1 s(-1). The thermal deformation behavior of high temperature tensile was analyzed. On the basis of strain compensation of Arrhenius constitutive, physically-based constitutive and PSO-BP neural network constitutive model were used to predict the high temperature flow behavior. Finally, the prediction accuracy of the three constitutive models were evaluated by cross-validation method. The conclusion show that the true stress-strain curves of diffusion bonded TC4 alloy are coordinated by temperature and strain. According to the nonlinear fitting results and thirty-five cross-validation tests indicate that the PSO-BP model can provide the most accurate prediction for diffusion bonded TC4 alloy hot deformation behavior, and the value of correlation coefficient (R) and average relative error (ARE) for the PSO-BP neural network model were 0.998 and 3.2. In addition, as revealed by micrographs, spheroidization appeared at lower temperature (600-760 degrees C) and strain rate (0.01 s(-1)), while the fraction of lamina secondary alpha phase decreased. At the same time, dynamic recrystallization and superplasticity began to occur of alpha phase at higher temperature (760-840 degrees C) and lower strain rate (0.0001 s(-1)).