Micromechanical Behaviors of Fe20Co30Cr25Ni25 High Entropy Alloys with Partially and Completely Recrystallized Microstructures Investigated by In-Situ High-Energy X-ray Diffraction

This work conducts a processing strategy to obtain the partially and completely recrystallized microstructures by cold rolling and annealing at different temperatures for a near-equiatomic Fe20Co30Cr25Ni25 high entropy alloy (HEA). The in-situ synchrotron-based high-energy-X-ray diffraction (HE-XRD) technique was adopted to investigate the mechanical behaviors and microstructural evolution of Fe20Co30Cr25Ni25 HEAs with heterogeneous (partially recrystallized) and homogeneous (completely recrystallized) microstructures during tensile deformation. The heterogeneous and homogeneous microstructures were obtained by annealing for 1 hour at 600 degrees C and 650 degrees C, respectively (hereinafter 600 and 650 A, respectively). No obvious phase transformation was found during the tensile deformation. The partially recrystallized HEA has a higher initial dislocation density (2.30 9 1015 m(-2)) than that in the completely recrystallized HEA (9.57 9 1014 m(-2)). The grains orientated with [200] parallel to the loading direction (LD) yield before the macroyielding (under similar to 951 MPa) in 600 A with the incomplete recrystallized microstructures. The results of transmission electron microscopy (TEM) and HE-XRD confirm that the deformation in the partially recrystallized microstructures mainly relies on dislocation slip, leading to a small number of deformation twins and very high-density dislocations at fracture, while a large number of deformation twins occurred in the completely recrystallized structures during deformation, leading to the obvious strain hardening. (C) The Minerals, Metals & Materials Society and ASM International 2021