Microstructure and mechanical properties of reactive sputtered nanocrystalline (Ti,Al)N films

Abstract

Nanocrystalline (Ti,Al)N thin films with different Al contents were prepared by alternatively sputtering Ti and Al targets in N2 gas atmosphere at 600°C and by mutual diffusion between Ti and Al atoms during film deposition. The microstructure and mechanical properties of the thin films were investigated by X-ray diffraction, field emission scanning electron microscopy and nanoindenter. The film surface was smooth and dense with an obvious column grain growth. The grain sizes of the deposited (Ti,Al)N films were approximately 11–12nm independent of the Al content. The preferential orientation of the (Ti,Al)N films varied from (200) to (111) plane and the lattice constant reduced with increasing Al content, associated with Ti atom substitution by smaller Al atoms during alternative deposition. The nanohardness of the (Ti,Al)N films remarkedly increased, the elastic modulus slightly decreased and thus H3/E*2 values greatly increased compared to the TiN film. The enhancement of nanocrystalline (Ti,Al)N films was interpreted in terms of solid solution hardening and preferential orientation effects.