Paracrystalline state achieved in the diamond system guides a direction to explore the missing link between amorphous and crystalline states. However, such a state is still challenging to reach in alloy systems in a controlled manner. Here, based on the vast composition space and the complex atomic interactions in the high-entropy alloys (HEAs), we present an “atomic-level tailoring” strategy to create the paracrystalline HEA. The addition of atomic-level Pt with the large and negative mixing enthalpy induces the local atomic reshuffling around Pt atoms for the well-targeted local amorphization, which separates severe-distorted crystalline Zr-Nb-Hf-Ta-Mo HEA into the high-density crystalline MRO motifs on atomic-level. The paracrystalline HEA exhibits high hardness (16.6 GPa) and high yield strength (8.37 GPa) and deforms by nanoscale shear-banding and nanocrystallization modes. Such an enthalpy-guided strategy in HEAs can provide the atomic-level tailoring ability to purposefully regulate structural characteristics and desirable properties.

Grain boundary engineering is a versatile tool for strengthening materials by tuning the composition and bonding structure at the interface of neighboring crystallites, and this method holds special significance for materials composed of small nanograins where the ultimate strength is dominated by grain boundary instead of dislocation motion. Here, we report a large strengthening of a nanocolumnar copper film that comprises columnar nanograins embedded in a bamboo-like boron framework synthesized by magnetron sputtering co-deposition, reaching the high nanoindentation hardness of 10.8 GPa among copper alloys. The boron framework surrounding copper nanograins stabilizes and strengthens the nanocolumnar copper film under indentation, benefiting from the high strength of the amorphous boron framework and the constrained deformation of copper nanocolumns confined by the boron grain boundary. These findings open a new avenue for strengthening metals via construction of dual-phase nanocomposites comprising metal nanograins embedded in a strong and confining light-element grain boundary framework.