Preparation, Simulation And Properties Of Titanium Aluminum Nitride Thin Films

As most promising alternative materials,(Ti, Al) N film has a better performancethan that of TiN.(Ti, Al)N film was widely applied in the field of cutting tools andmolds. The nanohardess of (Ti, Al) N largely depend on the Al content of the film.When the Al content exceeds the solid solubility of the TiN, the cubic phase (c)(Ti,Al) N transforming to hexagonal phase (h) significantly reduced its mechanicalproperties. Therefore, the controlling of the Al content of the film is especiallyimportant.(Ti, Al)N films were grown on WC-Co cemented carbides by DC and RF reactivemagnetron sputtering using Ti-Al composite target. The mechanical properties of (Ti,Al) N films with variable Al content were investigated by applying nanoindentation.The relationship between Al content with the nanohardness and friction coefficient ofthe (Ti, Al) N films was investigated. The mechanism of formation of its excellentmechanical properties is explored. The influence of annealing temperature on the filmproperties was studied. Based on Density Functional Theory, the structure, opticalproperties and band of AlN, TiN and (Ti, Al) N were calculated using CASTEPpackage of Materials Studio. The following conclusions are reached:(1) The mechanics and high-temperature stability of (Ti, Al) N film is better by RFreaction Magnetron Sputtering. Maximum nanohardness of the film is27.5GPa.Maximum elastic modulus is297GPa.The lowest friction coefficient is0.140.(2) When the Al content is low, the performance of the (Ti, Al) N has greatlyimproved.As the Al content exceeds the solid solubility of TiN, the crystal structure of(Ti, Al) N is transformed from fcc to hexagonal structure to result in its mechanicsdecrease.(3) The nanohardness of TiN film decreased rapidly after400°C, which may berelated to its surface oxidation.As the internal residual stress release,the nanohardessof the (Ti, Al)N films decreased with the annealing temperature increased.(4) The band gap of AlN is4.103eV that less than theory6.2eV. When the wavelengthis greater than200nm, the absorption coefficient of AlN is0, indicated that in thelong-wavelength transparent. When the wavelength is less than200nm, the absorptioncoefficient decreases as the wavelength increasing, indicated that the AlN lighttransmittance is not very high at short wavelength.(5) There is no apparent bandgap of TiN and DOS is not0at Fermi surface, whichindicates that TiN is metallic. We obtained the elastic constant, Young’s modulus andbulk modulus of TiN.(6) Ti doped AlN crystal band gap is smaller than that of AlN. As the doping amountincreases, the band gap is smaller.