A study of r.f.-sputtered Al and Ni thin films on AZ91D magnesium alloy

Pure Al and Ni thin films have been successfully r.f.-sputtered on AZ91D substrate. After 350 °C×24-h heat treatment in a high vacuum, the 2 μm thickness of the Al film reacted completely with the substrate to form Al12Mg17 phase. However, the Ni film was not observed to form a reactive layer after 350 °C×48-h treatment. Scratch test results indicate that the cohesive strength exhibits a significant improvement after the 350 °C×48-h treatment for the Ni film. The hardness tests demonstrated that the Ni film is harder than the Al film, AZ91D and Al12Mg17 phase. The sliding wear tests also showed that the Ni film has a lower wear rate than the others. The intrinsic brittleness of Al12Mg17 phase has a low cohesive strength with the substrate and a poor wear resistance to grinding.