Monitoring High-Pressure Fe Recrystallization Kinetics In Situ using High-Energy X-ray Diffraction during Multi-anvil Compression

Pressures often exceeding several times the yield strength of an alloy are encountered in many metal forming processes. These pressures alter the thermodynamics and kinetics of microstructural evolution which is generally not accounted for in microstructure predictions due to the challenges of quantitative characterization. Here we quantitatively observe changes with pressure in recrystallization kinetics of pure Fe in situ through adaptation of synchrotron X-ray compatible multi-anvil presses, originally designed for studying mineral deformation in the mantle. Recrystallization of pure Fe is monitored using in situ high-energy X-ray diffraction at 675 {\deg}C with 1 and 2 GPa applied. Principal component analysis applied to the in situ diffraction data is used to quantify the transition from a fine-grained microstructure with high dislocation content to a coarse-grained microstructure with low dislocation content. The recrystallization rates are characterized by fitting Avrami functions to the first principal component of the diffraction data and showed significantly slowed transformation kinetics with increasing pressure, despite indications of an increased recrystallization nucleation rate.