Fabrication of Silumins Using Silicon Production Waste

A survey of occurring methods of silumin production is presented. The possibility of fabricating casting alloys using amorphous microsilica is shown. Various methods of introducing silicon dioxide particles into the aluminum melt are studied and approved, notably, in the form of pelleted “aluminum powder–SiO₂” master alloys, by admixing particles into the melt at the liquidus temperature and by introducing SiO₂ into the melt jointly with the argon flow. Calculations of the formation enthalpies and variations in the Gibbs energy of the reduction of silicon from its oxide by aluminum are performed. The thermodynamic probability of formation of silumins using amorphous microsilica is shown based on these calculations. The influence of alloying additives and impurities on the process flow of silicon reduction is determined. The possibility of using magnesium as the surfactant additive, making it possible to remove oxygen from the surface of dispersed particles and reduce silicon from its oxide, is revealed. It is determined that the fabrication method of casting silumins by introducing amorphous silica preliminarily heated to 300°C into the aluminum melt (t = 900°C) jointly with the argon flow (with the subsequent intense stirring) jointly with the argon flow (with subsequent intense stirring) possesses the largest efficiency, because it makes it possible to fabricate aluminum–silicon alloys with a Si content higher than 6 wt % and microstructure corresponding to hypoeutectic casting silumins. The industrial implementation of the proposed method will make it possible to increase the efficiency of the occurring production process of silumins due to the economy of resources spent on purchasing commercial crystalline silicon. Moreover, this technology will promote lowering the environmental load to the surrounding medium due to the reduction of volumes and subsequent elimination of sludge fields, which are landfills for storing dust from gas purification systems of silicon production that contain up to 95 wt % amorphous microsilica.