Ti-Al-Si-N nanocrystalline composite films synthesized by reactive magnetron sputtering

A series of Ti-Al-Si-N nanocrystalline composite films with different Si contents were synthesized in a mixture gas composed of Ar, N2 and SiH4 by reactive magnetron sputtering. Energy dispersive spectroscopy, Auger electron spectroscopy, X-ray diffraction and transmission electron microscopy were employed to characterize the microstructures of these films; a nanoindenter was used to measure their mechanical properties. The results show that by changing the SiH4 partial pressure in the mixture gas, Si content in the films can be easily controlled. After Si is added into the films, an interface phase TiSix appears. It prevents (Ti,Al)N and AlN grains from growing, as a result, the (Ti,Al)N and AlN phases exist as nanocrystals. Correspondingly, the films' hardness and elastic modulus arrive at their maximum values of 36.0 and 400 GPa, respectively, at 3.5 at.% Si. With a further increase of Si content, the films' mechanical properties decrease gradually.