Enhanced strength and ductility synergy of a CoCrFeMnNi high entropy alloy with a hierarchical structure via severe distortion

Improvement on strength and ductility synergy has always been the unremitting pursuit for structural materials. In this study, the strengthen and ductility of CoCrFeMnNi HEA were improved simultaneously via a designed continuous driven friction process. The results show that a hierarchical structure, which consists of 3 zones: the homogenously distributed ultrafine grains in fusion zone, severely distorted grains in thermal mechanical effect zone and coarsening equiaxed grains with high dislocation density in base zone, was formed in CoCrFeMnNi HEA, leads to the tensile strength enhanced from 598 to 629 MPa with the ductility increased from 27% to 38%. The findings provide new insight into solution to strength and ductility trade-off for structural materials.