Investigation On The Preparation And Corrosion Resistance Of Al-Mg Intermetallic Coatings

Intermetallic compounds, as its well strength at high temperature, high hardness and good corrosion resistance, are usually used to strengthen the common alloy, or used as alternative materials in high temperature or corrosive environment, where general metal and alloy cannot be employed. In addition, some intermetallic compound materials which have special properties show high application value in electrical, magnetic or optical fields. However, as a result of brittleness it is so difficult to be plastic processing. Therefore, there is no intermetallic used as structural material in the past. Today, it is recognized that intermetallic in structural materials has strengthen function. Obviously, due to high hardness and good stability, intermetallic compounds have the potential for other structural materials to be more widely used. Another important research direction of intermetallic compound is as a protective coating to increase the corrosion resistance or wear performance of the substrate, as its good corrosion resistance or high wear performance.In this study, Al-Mg composite coating is prepared on ZL102 Al alloy substrate. Then heat diffusion treatment and gas tungsten arc melting are employed as post-processing, respectively. The microstructure and phase composition are analysis by optical microscope (OM), scanning electron microscopy (SEM), electron probe microanalysis (EPMA) and X-ray diffraction (XRD). The influence of heat treatment parameters on microstructure and properties of the coating and the feasibility of GTAM in the preparation of Al-Mg intermetallic coating is analysis. The corrosion resistance of Al-Mg composite coating and Al-Mg intermetallic coating are tested by short/long-term immersion test and polarization curves.The results show that uniform and compact Al-Mg composite coatings are successfully prepared on ZL102 Al substrate the coatings. The coatings are organized of aluminum layers and magnesium layers and the coating is mechanical chimera to the substrate. After heat diffusion treatment at different temperatures, aluminum layer and magnesium layer are diffusion to each other when the heat treatment temperature is above 320℃. Al-Mg intermetallic compound phase (Al3Mg2 and Al12Mg17), are generated in the coating and the corrosion resistance of the coating is significantly increased. The hardness of the coating is also increased significantly, indicating the wear resistance of the coating is improved. The bonding mode between coating and substrate is change to local metallurgical bonding. By adjusting the twin-wire arc spraying and GTAM process parameters, Al-Mg intermetallic compound coating are deposited on ZL102 Al alloy substrate successfully. The intermetallic coating is composited of uniform Al-Mg intermetallic compounds. Compared with the coating prepared by heat diffusion treatment, the GTAM coating are more uniform. The corrosion resistance of intermetallic coating after GTAM is significantly improved through polarization curves, and it can provide corrosion protection to light alloy. After GTAM the coating are metallurgical bond with substrate in large area, and compared with the heat treatment coating the bond strength of the coating are further improved.