The formation mechanism and characterization of al-si master alloys from sodium fluosilicate

Abstract

A modified Al-Si alloy containing up to 15 wt.% Si has been obtained from the reaction of sodium fluosilicate (Na2SiF6) with molten aluminum. This work attempted to estimate the mechanism of the reaction of Na2SiF6 with molten aluminum to produce Al-Si alloys. The effect of temperature, Na2SiF6/Al Wt ratio and reaction time on the formation of Al-Si alloy were investigated. The thermodynamic data, kinetic and rate of the reaction were studied. The results showed the possibility of the reaction between Na2SiF6 and molten aluminum thermodynamically, and that this reaction might be controlled chemically. The current study aims to optimize the factors that affecting the preparation of a modified Al-Si alloy from a reduction of sodium fluosilicate using molten aluminium. Temperature 950oC, reaction time 20 – 25 min and Na2SiF6/Al Wt ratio related to the applied Si percentage. The prepared alloys could be modified due to the presence of Na2SiF6 in the used material as a source of sodium in response to modifying the produced Al-Si alloys. The microstructure by using LOM, SEM, and EDX proved that the needle-like silicon converts to fine fibrous. The volume fraction of primary Si reduces and the eutectic point moves to a higher silicon concentration. The modification improves the wear characteristics and increases the tensile and hardness.