Multi-physics modeling of pore-induced dynamic recrystallization during hot isostatic pressing of additively manufactured Ti alloy

Pore closure during hot isostatic pressing (HIP) is often accompanied by localized microstructural refinement in additively manufactured (AM) Ti alloys. However, the mechanism pathway from thermo-mechanical deformation to dynamic recrystallization (DRX) remains difficult to quantify. Here, a coupled finite-element and phase-field (FE-PFM) framework is developed to link pore-scale inelastic deformation to DRX near pore-affected regions. The FE model resolves HIP-driven pore shrinkage using an elastic-plastic-creep constitutive law and provides spatially and temporally varying inelastic strain-rate histories. These histories are then supplied to a multiphase-field DRX formulation in which dislocation density evolves via a Kocks-Mecking model and drives stored-energy-controlled nucleation and grain-boundary migration. The simulations reproduce key experimental trends of pore closure and pore-associated equiaxed grain clusters. Finite-element results show that densification arises from the combined action of creep and plastic deformation. Parametric studies at 50, 100, and 175 MPa further demonstrate that, while pore closure increases with pressure, the contribution of plastic deformation is regulated by competition between sustained stress concentrations and creep-driven stress redistribution. Moreover, recrystallization is governed by the integrated thermo-mechanical history, specifically the temporal overlap between the availability of potential nucleation sites and the nucleation kinetics, rather than by peak strain rate or pressure magnitude alone. Together, these results provide a mechanistic basis for HIP process optimization aimed at achieving simultaneous densification and microstructural refinement.