Ultrafine-grained CoCrFeMnNi high-entropy alloy produced by cryogenic multi-pass caliber rolling

The ultrafine-grained (UFG) structure (∼100 nm) of CoCrFeMnNi high-entropy alloy was achieved using cryogenic multi-pass caliber rolling at 77 K to impose less deformation (ε = 1) compared to severe plastic deformation (SPD, ε > 4). Highly increased twinning activity at 77 K caused the grain interiors to fragment significantly, so UFG structure could be induced without imposing SPD. Intersected twin morphology and secondary twins played a key role in twinning-induced grain refinement to achieve UFG structure. The processed material showed an exceptional high yield strength of ∼1.5 GPa with a reasonable fracture elongation of ∼10% at room temperature. [Display omitted] •Ultrafine grained structure was achieved using cryogenic multi-pass caliber rolling.•Highly increased twinning activity at 77 K caused grains to fragment significantly.•Specifically, intersected twins and secondary twins refined grains very effectively.•So, UFG structure could be achieved without imposing severe plastic deformation.•The processed material showed an exceptional high yield strength of ∼1.5 GPa.