In order to clarify the controversies of hardening mechanism for TiN/SiNx-based nanocomposite films, the microstructure and hardness for TiN/SiNx and TiAlN/SiNx nanocomposite films with different Si content were studied. With the increase of Si content, the crystallization degree for two series of films firstly increases and then decreases. The microstructural observations suggest that when SiNx interfacial phase reaches to a proper thickness, it can be crystallized between adjacent TiN or TiAlN nanocrystallites, which can coordinate misorientations between nanocrystallites and grow coherently with them, resulting in blocking of the dislocation motions and hardening of the film. The microstructure of TiN/SiNx-based nanocomposite film can be characterized as the nanocomposite structure with TiN-based nanocrystallites surrounded by crystallized SiNx interfacial phase, which can be denoted by nc-TiN/c-SiNx model ('c’ before SiNx means crystallized) and well explain the coexistence between nanocomposite structure and columnar growth structure within the TiN/SiNx-based film.

FeNi/V nanomultilayered films with different V layer thicknesses were synthesized by magnetron sputtering. By adjusting the thickness of the V layer, different interfacial compressive stress were imposed on FeNi layers and the effect of interfacial stress on martensitic transformation of the FeNi film was investigated. Without insertion of V layers, the FeNi film exhibits a face-centered cubic (fcc) structure. With the thickness of V inserted layers up to 1.5 nm, under the coherent growth structure in FeNi/V nanomultilayered films, FeNi layers bear interfacial compressive stress due to the larger lattice parameter relative to V, which induces the martensitic transformation of the FeNi film. As the V layer thickness increases to 2.0 nm, V layers cannot keep the coherent growth structure with FeNi layers, leading to the disappearance of interfacial compressive stress and termination of the martensitic transformation in the FeNi film. The interfacial compressive stress-induced martensitic transformation of the FeNi nanofilm is verified through experiment. The method of imposing and modulating the interfacial stress through the epitaxial growth structure in the nanomultilayered films should be noticed and utilized.