Investigation On Microstructure And Properities Of Al, Ti-Al-N,Al/Ti-Al-N Films Fabricated On AZ91D Magnesium Alloy By Magnetron Sputtering

Magnesium alloy is the lightest metal structure material which is practical used, with excellent properties, such as low density, high specific strength and stiffness, good shock absorption ability, electromagnetic shielding ability, etc.. So, the magnesium alloy is widely used in the automotive industry, aerospace industry, microelectronics and many other fields. However, its poor corrosion resistance have hindered the wider use of magnesium alloy. At present, the surface treatment used for magnesium alloy are: chemical conversion, anodicoxidation treatment, chemical plating, vapor deposition and so on. Magnetron sputtering is one of the important methods for industrial application owing to its high deposition rate compared with other vapor deposition methods, simple process, good film quality and environmentally friendly.In this thesis, the author deposited Al,Ti-Al-N monolayer films respectively on AZ91D magnesium alloy by magnetron sputtering. On the basis of Al,Ti-Al-N monolayer films preparation experiments, the author selected the optimum parameters to deposite Al/Ti-Al-N bilayer films. This thesis mainly studied the effects of magnetron sputtering parameters, such as substrate temperature, bias voltage and partial pressure ratio of N2/Ar, on the microstructure and properties of the films.The results show that, substrate temperature and negative bias voltage had great influence on the microstructure and properties of Al monolayer films, while the substrate temperature was 150℃, the films with small but uniform grain size had high density, relatively high corrosion potential and lowest corrosion current; while the negative bias voltage was -60V, the films with high density had lowest corrosion current. Partial pressure ratio of N2/Ar and negative bias voltage had great influence on the microstructure and properties of Ti-Al-N monolayer films, while the partial pressure ratio of N2/Ar was 1.5:10, the films with high microhardness and hydrophobicity had high electrochemical impedance, and had better performance of anticorrosion; while the negative bias voltage was -20V, the films with relatively high microhardness and highest hydrophobicity had highest electrochemical impedance, and had best performance of anticorrosionLast, the author deposited Al monolayer film as buffer layer first, and then deposited Ti-Al-N film using the optimum parameters by magnetron sputtering to prepare Al/Ti-Al-N bilayer film. The author studied the differences of microstructure and properties between Ti-Al-N monolayer films and Al/Ti-Al-N bilayer films, and got the result that the Al/Ti-Al-N bilayer films had more excellent anticorrosion ability by comparing the hydrophilicity and electrochemical property between this two kinds of films.