Microstructure And Mechanical Properties Of Dual-supersaturated Solid Solution(Ti,N)/Al Nanocomposite Films By Magnetron Sputtering

Aluminum matrix film has a wide range of applications in the field of corrosion protection of metals. It is one of the valuable research directions to enhance the mechanical properties of Al alloy films through forming supersaturated solid solution based on the non-equilibrium characteristics of vapor deposition. In order to study the strengthening effect of adding Ti and N simultaneously on aluminum matrix composite film, a series of films with Ti:N≈1 have been prepared by magnetron co-sputtering Al and Ti N targets. The influence of(Ti,N) content, substrate temperature, annealing process on the microstructure and mechanical properties of(Ti,N)/Al composite films has also been investigated.The results indicate that:1. As for films deposited at room temperature(RT), under the non-equilibrium condition of magnetron sputtering, Ti, N atoms dissolve in Al lattice as substitutional and interstitial solutes respectively, thereby the(Ti,N)/Al nanocomposite film was generated in the form of a "dual-supersaturated solid solution" exhibiting both features of substitutional and interstitial solid solution. Grains in the film were significantly refined after doping Ti, N. With(Ti,N) content increasing, the film transformed from nanocrystalline to amorphous. Stacking fault and twinning could be observed in grains and solute atoms might enrich at certain grain boundaries. The hardness of RT film raised rapidly with increasing(Ti,N) content and reached 8.9 GPa at 17.1at.%(Ti,N).2. The investigation on film annealing indicated that, under annealing at 250°C, RT film hardness increased slightly. The hardness began to decrease as annealing temperature elevated to 450°C. When RT sputtering(Ti,N)/Al film with 6at.%(Ti,N) was heated to 430°C, it transformed from metastable state to equilibrium state.3. As the substrate temperature elevated to 400°C,the hardness of high temperature(HT) sputtering film was a little lower than RT film with 450°C annealing. RT, HT sputtering films and films after annealing all showed high elastic modulus of ~120GPa. The chemical environment around Ti atoms in RT and 400°C sputtering films was similar to that of Ti-Al alloy, and compared with Al atoms, Ti atoms didn’t take precedence of bonding with N atoms.These results above demonstrate the significant grain refining and strengthening effect of Ti and N dual-supersaturated solid solution on aluminum film and the excellent high temperature stability of this kind of films.