Synergistic reinforcement of Cu–Ni–Al films with dual nanostructure

Abstract

ABSTRACT Nanocrystalline-strengthened surface layer significantly improves the surface hardness and wear resistance of Cu or Cu alloys and avoids the reduction of conductivity. However, the poor thermal stability limits its industrial application. Herein, a series of Cu-Ni-Al films were prepared by radio frequency magnetron sputtering, which shows γ (∼20 nm) + γ′΄ phase (∼10 nm) dual nanostructure. Compared with pure Cu film, γ′ phase precipitation-strengthened films possess higher hardness, outstanding wear resistance and a certain electrical conductivity. The strengthening mechanisms have been discussed in detail. After annealing at 450°C/20 h, the hardness of Cu-Ni-Al films decreases slightly, but their wear resistance remains essentially unchanged, exhibiting superior thermal stability, the main reason of which is that the growth of nanocrystalline Cu can be retarded through the precipitation of γ′ phases.