Crystal plasticity-phase–field based analyses of interfacial microstructural evolution during dynamic recrystallization in a dual phase titanium alloy

In this study, an integrated crystal plasticity finite element–phase–field (CPFE–PF) model is developed to examine dynamic recrystallization (DRX) in a dual phase Ti alloy. The CP framework is coupled with PF by updating the free energy density with energy contributions due to plasticity. The evolution of grain boundaries through evolving non-conserved order parameters in the PF model is tracked using the Allen–Cahn equation. Nucleation is allowed to occur if the dislocation density exceeds a critical value. DRX is studied in various Ti morphologies such as an $\alpha -$Ti single crystal containing a stiff elastoplastic particle, $\alpha$-Ti bicrystals with low and high misorientation between grains, an $\alpha -\beta$ bicrystal and a globular $\alpha -\beta$ Ti structure with $\beta$ phase at $\alpha -\alpha$ interfaces. For an $\alpha -$Ti bicrystal, a high misorientation facilitates the onset of DRX at the $\alpha -\alpha$ interface at a significantly lower strain than the bicrystal with low misorientation. In an $\alpha -\beta$ bicrystal, DRX is only observed at the $\alpha -\beta$ interface. For the globular morphology, nucleation is observed at both $\alpha -\beta$ interfaces and inside $\alpha$ grains, which is consistent with previous experimental observations for a similar morphology. Nucleation inside $\alpha$ grains is explained by the correlation between SSD density and misorientation indicators such as KAM and GROD at the nucleus site. To correlate slip activity with nucleation propensity immediately prior to different nucleation events, the dislocation density, shear rate and Schmid factors on different slip systems are evaluated at nucleation sites.