Silicon has a corrosive effect on cemented carbide. Although the general will be more than 12% Si aluminum alloy called high silicon aluminum alloy, recommend the use of diamond tools, but this is not absolute, silicon content gradually increased the destructive power of the tool is gradually increased. So some manufacturers in the silicon content of more than 8% recommended the use of diamond tools.
Silicon content between 8% -12% of the aluminum alloy is a transition interval, both can use ordinary carbide, diamond tools can also be used. However, the use of cemented carbide should be used by the PVD (physical coating) method, without aluminum, the film thickness of the smaller tool. Because the PVD method and the thickness of the film to make the tool to maintain a more sharp cutting edge possible (otherwise to avoid the film in the edge of the abnormal growth of the need for adequate passivation of the edge, cutting aluminum alloy will not be sharp) , While the film material containing aluminum may cause the blade film to work with the workpiece material to destroy the film and the tool base of the combination. Because the super-hard coating is mostly aluminum, nitrogen, titanium compounds may be due to the carbide substrate with the film peeling off a small amount of peeling caused by cutting.