Phase-field investigation on the grain evolution and mechanical response during dynamic recrystallization of deforming tungsten

Abstract

In this work, the microstructural evolution and mechanical response during tungsten’s dynamic recrystallization (DRX) processes were studied by multiphase-field simulations coupling a dislocation density model for plastic deformation. We found that the deforming tungsten could reach a dynamic balanced state characterized by converged stress-strain curve and average radius of refined grains. This balance is determined by the deformation temperature and strain rate, instead of the initial averaged grain size. When the deformation parameters change during DRX, the final dynamically balanced state is solely determined by the final values of deformation parameters, while irrelevant to the history of their changes. Moreover, we find that such dynamic balance is essentially caused by the offset effects of grain growth and grain nucleation. The former leads to the increase of stored plastic energy and grain size while the latter leads to the opposite effects. Finally, a novel constitutive equation considering initial grain size, temperatures and strain rate is established, and generally agrees well with experimental results for the DRX of tungsten. These results clarify the synchronous relationship between mechanical response and microstructure evolution, and could help us to predict and tailor the microstructures of deforming alloys.