ABSTRACT
The equimolar multicomponent alloys, recently dubbed as the medium-entropy alloys (MEAs) and high-entropy alloys, are emerging as an interesting class of structural materials. The single-phase CrCoNi and FeCrMnCoNi alloys of the face-centered cubic structure, in particular, have exhibited a combination of high ultimate tensile strength, ductility, and fracture toughness. The loading-unloading-reloading tensile tests were conducted to unveil the underlying strain hardening mechanism and defect behaviors. The dynamic generation of nanograined (NG) in our heterogeneous grain structure is further confirmed by TEM observations. A fully recrystallized grain structure would primarily store stacking faults, and not be as conducive to load partitioning and dynamic nucleation of many NGs at GBs and TJs via dynamic recrystallization. Scanning electron microscopy was used to characterize the cross-sectional microstructural evolution of the annealed CrCoNi MEA before and after tensile tests. A high-spatial resolution analytical electron microscope operating at 200 kV was used for examination of the microstructural features after tensile testing at designated strains.
