Dehydrogenation of AlSi7Fe1 Melt during In Situ Composite Production by Oxygen Blowing

Abstract

The technology of producing a composite material in situ envisages the pre-saturation of an AlSi7Fe1 melt with hydrogen; afterwards, the melt is blown with oxygen until the hydrogen dissolved in the melt is burned out. The hydrogen content was researched during the manufacturing process of the composite material; before oxygen blowing, and at incomplete and complete burning out of the dissolved hydrogen. The interrelation between the absorbed hydrogen content and the aluminum oxide fraction was identified. A mathematical model was proposed which demonstrated that during the saturation process of the melt with oxide particles, hydrogen was absorbed on their surface as a layer close to monoatomic, which does not lead to the realization of the pores’ heterogeneous nucleation mechanism. Due to this, castings produced from the researched composite material are leakless. Incomplete burning out of hydrogen dissolved in the melt leads to the formation of significant hydrogen porosity. The proposed method of prevention of gas porosity in cast composites is an alternative to the conventional one and offers not only the purging of the melt from oxide inclusions but, on the contrary, a significant increase in their specific surface, which allows for the reduction in hydrogen content on the inclusion surface to the monoatomic level.