Deformation by dislocations, twinning, and phase transformations in compositionally complex FCC solid solutions

The equiatomic CrCoNi alloy is an fcc solid solution that exhibits intriguing behaviors including very large strain hardening and cyclic hardening rates, large fracture toughness, and strong dependence of the yield strength at low temperature. Detailed characterization using a variety of electron microscopy methods has revealed that these behaviors are closely linked to the interplay between dislocation-mediated plasticity, microtwinning, and an fcc-to-hcp transformation. The development of these mechanisms as a function of deformation for both ambient and cryogenic temperatures is discussed. The effect of Al and Ti, and the formation L1₂ short-range ordering domains, on the deformation mechanisms will also be presented. Fundamental insights into these experimental results are also provided by density functional theory, atomistic, and continuum-level calculations. (author)