Ultra-strong nanostructured CrMnFeCoNi high entropy alloys

Equiatomic CrMnFeCoNi high-entropy alloy (HEA) known as Cantor alloy was extensively studied because of intriguing mechanical properties and fracture toughness. However, the HEA exhibits relatively low yield strength due to its intrinsic face-centered cubic lattice structure. In the present letter, crystalline/amorphous dual-phase CrMnFeCoNi alloy was deposited via magnetron sputtering technique. NC HEA with grain size of only ~7.2 nm was derived from low temperature annealing. The hardness reaches to 13.76 GPa, which is the maximum ever reported for CrMnFeCoNi HEA, and the contributions of the NC HEA microstructural characteristics to the ultra-high hardness were revealed. It was proposed that the quasi-dislocation-free crystalline structures and fully relaxed grain boundaries result in the significantly enhanced hardening and thermostability derived in the annealed NC HEA.