Structural and microstructural analysis of bifunctional TiO2/Al-Zr thin film deposited by hybrid process
Abstract
An Al-Zr (4 at.% Zr) film is deposited on High Speed Steel substrates by pulsed Direct Current magnetron sputtering in order to provide sacrificial corrosion resistance of steel. A TiO2 layer is synthesized on the top by aerosol-assisted metal-organic chemical Vapour Deposition (AA-MOCVD) in order to insure anti-biofouling behaviour. TiO2 coating has a typical CVD microstructure and the film is anatase single phased. The as-deposited Al-Zr film is an extended supersaturated solid solution Al(Zr) of Zr in Al. The AA-MOCVD process is performed at 773 K for 40 min. This annealing leads to a fine precipitation of highly coherent metastable Al3Zr(L12) phase in the Al(Zr) matrix. Larger precipitates with a needle like morphology, which crystallize in the equilibrium tetragonal Al3Zr(D023) phase are also observed. Transmission electron microscopy analysis clearly shows the cube on cube orientation between Al3Zr(L12) phase and Al(Zr) matrix. As the cubic Al3Zr(L12) metastable phase is beneficial for the mechanical properties of bulk aluminium based alloys, this result opens the investigation field on Al-Zr coatings, which can provide sacrificial protection of steels.
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