Modeling of discontinuous dynamic recrystallization of a near-α titanium alloy IMI834 during isothermal hot compression by combining a cellular automaton model with a crystal plasticity finite element method

Abstract

Discontinuous dynamic recrystallization (DDRX) is a common metallurgical phenomenon that occurs in titanium alloys and significantly influences the microstructural evolution and deformation behavior of materials. In this study, the DDRX of the beta phase (β-DDRX) of an IMI834 alloy during isothermal hot compression was simulated by combining a cellular automaton (CA) model with a crystal plasticity finite element (CPFEM) method. The two-dimensional hot compression was conducted using a CPFEM to acquire deformation parameters at the grain level, such as strain and crystal orientation, during the deformation process. These values were used as inputs into the CA model in each simulation step to investigate the effect of non-uniform deformation on the β-DDRX. Nucleation of the β-DDRX and the growth of recrystallized grains (re-grains) were visibly simulated by the CA model. To validate the CA model, the strain distribution predicted by the CA model was compared with that predicted by the CPFEM, and the nucleation mode, which considered the effect of non-uniform deformation at the grain level on deformation, was simulated. The CA model was then used to predict the average growth velocity, average re-grain size, recrystallization kinetics and flow stress. The simulated results showed that (1) the average growth velocity and average re-grain size increased with increasing temperature or decreasing strain rate, whereas the recrystallized volume fraction increased with increasing strain rate or decreasing temperature, (2) the recrystallization kinetics predicted by the current CA model appeared nonlinear, which deviated from the JMAK or CA predictions, which did not consider non-uniform deformation, and (3) non-uniform deformation at the grain level influenced the recrystallized nucleation mode and rate.