Achieving ultra-high strength in a face-centered-cubic FeCrCoNi high entropy alloy through dense nanotwins bundles structure prepared by cryo-rolling

High/medium-entropy alloys (HEAs/MEAs) with simple single-phase face-centered-cubic (fcc) structures have exceptional tensile ductility and outstanding toughness, but their room-temperature strengths are moderate. Here we introduced a mixed nanostructure, composed of high density nano-scale twins in the form of bundles and nanograins in shear bands, in a single-phase fcc FeCrCoNi HEA by means of cryo-rolling at liquid nitrogen temperature (LNT), which result in a substantial enhancement of tensile strength. The as-prepared nanostructured FeCrCoNi HEA exhibits an ultra-high ultimate tensile strength of ∼1.8 GPa, an elongation-to-failure of ∼10%. The ultra-high strength originates mainly from the effective blockage of dislocation motion by the ultra-high density of internal twin and grain boundaries. The microstructural evolution and formation mechanism of the mixed nanostructure in FeCrCoNi HEA were investigated in detail by transmission electron microscopic characterization.