Constitutive modeling and microstructure research on the deformation mechanism of Ti-6Al-4V alloy under hot forming condition

The hot tensile tests of Ti-6Al-4V alloy sheet at different temperatures (650, 700, 750 degrees C) and different strain rates (0.1 s(-1), 0.01 s(-1), 0.001 s(-1)) were carried out, five phenomenological models are established (Arrhenius with strain compensation(ARR), Johnson-Cook(JC), modified JC(m-JC), Hensel-Spittel(HS), modify HS(mHS)). A new JC model considers the softening coefficient m as a function of strain rate and adds a temperature correction function is proposed. The electron backscatter diffraction (EBSD) test was used to observe the microstructure evolution after thermal deformation at 700 degrees C-0.1 s(-1). After high-temperature tensile loading, the proportion of beta phase increased, the average grain size decreased by 67.69%. The macroscopic softening phenomenon is caused by dynamic recrystallization (DRX), dynamic recovery (DRV), and the formation of beta phase. The prediction accuracy of the six models was discussed by comparing the AARE value and the R-value. The comparison results show that the HS model has the best prediction accuracy, and its AARE value and R-value are 5.24% and 0.98794; the JC model has the worst prediction ability, and its AARE value and R-value are 41.1% and 0.84726. The prediction accuracy of the n-JC model is higher than that of the other JC models. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

The hot tensile properties of Ti-6Al-4V alloy sheet were studied, and it was found that high-temperature loading results in a decrease in grain size, an increase in the proportion of the beta phase, and macroscopic softening phenomenon.