Influence of residual deformation fields on microstructural evolution during powder metallurgy hot isostatic pressing

The objective of this study is to understand how deformation fields and residual defects influence microstructure evolution during powder metallurgy hot isostatic pressing (PM-HIP). In this work, gas-atomized Fe-10Cr-6.1Al powders are consolidated at 750°C and 1050°C at 100 MPa and 150 MPa for 3 hours. The lower consolidation temperature corresponds to a kinetically intermediate stage of PM-HIP microstructure evolution, enabling observation of dynamic consolidation mechanisms through parametric effects. Numerous low-angle grain boundaries are observed at intermediate stages of the consolidation process. Results show that strain energy (from entrained low-angle grain boundaries and contact stresses) drives rapid recovery and recrystallization at the early stages of PM-HIP. But as strain energy is dissipated through defect annihilation and relaxation of contact stresses, microstructural evolution slows, and grain growth dominates the later stages of PM-HIP. In PM-HIP microstructure, isolated fine-grained particle artifacts are observed, which remain relatively undeformed, due to delayed recovery-recrystallization kinetics potentially associated with localized stress and strain variations. This work reveals that residual deformation fields, together with PM-HIP processing parameters, can be used to kinetically trap the consolidated microstructure at desired stages along the recovery-recrystallization-grain growth process. Harnessing this concept enables our ability to design controlled material microstructure through advanced manufacturing.