Synthesis and Characterization of Hypoeutectic Al-Si Alloys by Reduction of Sodium-Fluosilicate Using Powdered Aluminium [ READ ]
H. S. Wasly, Moatasem M. Kh, Mohamed M. Ali, A. M. Omran
Al-Si alloys and sodium aluminum fluorides were obtained by reduction of Sodium-Fluosilicate (S.F) with Al powder and molten aluminum. Different factors affecting the composition of the produced Al-Si alloys are studied. These factors are sodium fluosilicate to aluminum weight ratio, Al powder to S.F weight ratio and reaction time. The produced Al-Si alloys are self-modified due to sodium fluoride existence in the reaction's bath, which changed the morphology of Si crystals. This modification process assists in improving the mechanical properties. Microstructure examination, chemical analysis, x-ray diffraction, and Differential Thermal Analysis (DTA) are performed to characterize the as received materials and the produced alloys. The results indicated that the mechanism of the reaction was taken place as follows; when S.F is added to Al, the S.F decomposes to produce SiF4 gas which reduced in the presence of Al powder to silicon ion. The silicon ions combine with Al to form the Al-Si alloy and the fluorine ions react with Al and the residue of sodium fluoride to produce cryolite. The produced Al-Si alloy in this study is a high quality containing Si up to 12%, with less than 0.2 total impurities and the produced cryolite can be used in aluminium electrolysis.
H. S. Wasly, Moatasem M. Kh, Mohamed M. Ali, A. M. Omran
Al-Si alloys and sodium aluminum fluorides were obtained by reduction of Sodium-Fluosilicate (S.F) with Al powder and molten aluminum. Different factors affecting the composition of the produced Al-Si alloys are studied. These factors are sodium fluosilicate to aluminum weight ratio, Al powder to S.F weight ratio and reaction time. The produced Al-Si alloys are self-modified due to sodium fluoride existence in the reaction's bath, which changed the morphology of Si crystals. This modification process assists in improving the mechanical properties. Microstructure examination, chemical analysis, x-ray diffraction, and Differential Thermal Analysis (DTA) are performed to characterize the as received materials and the produced alloys. The results indicated that the mechanism of the reaction was taken place as follows; when S.F is added to Al, the S.F decomposes to produce SiF4 gas which reduced in the presence of Al powder to silicon ion. The silicon ions combine with Al to form the Al-Si alloy and the fluorine ions react with Al and the residue of sodium fluoride to produce cryolite. The produced Al-Si alloy in this study is a high quality containing Si up to 12%, with less than 0.2 total impurities and the produced cryolite can be used in aluminium electrolysis.
