Study on Hot Flow Behaviors and Deformation/Diffusion Mechanisms of V and V-Ti Microalloyed Steels by Physical Constitutive Modeling

The hot compression tests of medium carbon V and V-Ti microalloyed steels are carried out at the temperature of 900-1100 degrees C and strain rate of 0.01-10 s(-1). Three physical constitutive models based on creep theory are studied, the prediction accuracy is compared and analyzed by employing the correlation coefficient (R) and average absolute relative error (AARE), and the deformation/diffusion mechanisms are discussed. The results show that Ti has obvious hardening effect in V microalloyed steel and retards the onset of dynamic recrystallization. The physical constitutive model containing the theoretical value of creep exponent 5 can accurately describe the hot flow behavior of both steels, the prediction accuracy of which is comparable to that of the model containing exponent n, reflecting that the dominant deformation mechanism of both steels is dislocation climbing. Furthermore, a modified physical constitutive model combining diffusion mechanisms of lattice diffusion and grain boundary diffusion shows higher accuracy (R = 0.996, AARE = 3.81% of V steel and R = 0.994, AARE = 4.52% of V-Ti steel), indicating that the diffusion mechanism is controlled not only by lattice diffusion but also by grain boundary diffusion.

Automated summary

This study conducted hot compression tests on medium carbon V and V-Ti microalloyed steels at temperatures of 900-1100 degrees C and strain rates of 0.01-10 s(-1). Three physical constitutive models based on creep theory were examined, with their prediction accuracy compared and analyzed using correlation coefficient (R) and average absolute relative error (AARE). The results showed that Ti has a significant hardening effect in V microalloyed steel and delays the onset of dynamic recrystallization. The physical constitutive model with a theoretical creep exponent of 5 accurately described the hot flow behavior of both steels, with comparable prediction accuracy to the model with exponent n, indicating that the dominant deformation mechanism for both steels is dislocation climbing. Furthermore, a modified physical constitutive model incorporating diffusion mechanisms of lattice diffusion and grain boundary diffusion exhibited higher accuracy, suggesting that diffusion mechanisms are controlled by both lattice diffusion and grain boundary diffusion.