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.
Highlights
At present, aluminum matrix composites are developed, and commercially produced [1]
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
As is shown in paper [2], hydrogen porosity is the main problem in the production of aluminum matrix molded composites
Summary
Aluminum matrix composites are developed, and commercially produced [1]. As is shown in paper [2], hydrogen porosity is the main problem in the production of aluminum matrix molded composites. The second type of porosity in a metal matrix originates from a significant decrease in hydrogen solubility in aluminum during crystallization [6]. The paper shows a direct dependence of the oxide particles’ surface area on the formation of hydrogen porosity. The oxide particle surface is a solid support whereon hydrogen atoms settle out, and the generation of pores begins at their critical concentration, while deep over-saturation without the formation of pores can be possible at high purity (that is, low percentage of non-metallic inclusions) of the melt. In the process of bblowing, an oxygen bbubble iss ffoorrmmeed oonn tthhee ttuuyyeerree flflaatt;; ffrroomm iinnssiiddee,, the menttiioonneedd bbuubbbblleeisisccoovveerereddwwitihthananalaulmuminiunmumoxoidxeidfeilmfilm(Fi(gFuigreu1reA1).AA).s Athse tohxeyogxeyngbeunbbbulebbflloeafltsouatps,udpis,sdoilsvseodlvheyddhroygdernogisenadissoardbseodrboendito(nFitg(uFriegu1Bre).1TBh)e.
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