Bamboo-like dual-phase nanostructured copper composite strengthened by amorphous boron framework

Abstract

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.

Amorphous Thickness-Dependent Strengthening–Softening Transition in Crystalline–Amorphous Nanocomposites

“…Concurrently, nanosized amorphous metals exhibit an enhanced ability to suppress localized shear bands, thereby contributing to an ideal strength with enhanced ductility. , Building upon the success of introducing structural heterogeneity to improve strength, − a new strategy has emerged that combines the structural advantages of crystalline and amorphous nanostructures in a complementary manner. This strategy has led to the development of crystalline–amorphous nanocomposites, − where nanograins are encapsulated by nanosized thick amorphous GBs. In these nanocomposites, the ultrastrong amorphous GBs effectively impede or absorb dislocation activities within nanograins, , preserving the Hall–Petch strengthening effect even at extremely refined grain sizes .…”