INFLUENCE OF STRONTIUM ADDITION ON OXIDATION KINETICS OF INDUSTRIAL CAST ALUMINUM ALLOYS AL2, AL4 AND AL9

Abstract

When melting cast aluminum alloys, their waste is observed, or more precisely, oxidation by the gas phase of the furnace. To select the optimal regime for melting alloys, it is necessary to know the physicochemical laws of this process, which are little studied. To study the kinetics of oxidation of metal melts, the method of continuous sample weighing is used, which is usually used in the study of high-temperature corrosion of solid metals. The mechanism of interaction of liquid metals with oxygen is similar in nature to high-temperature gas corrosion of solid metals. In both cases, adsorption of gas molecules on the metal surface, nucleation, and then growth of an oxide film take place. The kinetics of oxidation of strontium-modified AL2, AL4, and AL9 melts with atmospheric oxygen was studied by thermogravimetry. It is shown that the addition of strontium up to 0.1 wt % increases the oxidizability of melts. An increase in temperature promotes an increase in the rate of oxidation of these melts. The process of oxidation of the investigated melts obeys the parabolic law. The true rate of oxidation is on the order of 10–4 kg/m2 · s. The apparent activation energy of oxidation, depending on the amount of modifiers in the alloys, is: for AL2 alloy – 56.52–43.75, for AL4 alloy 59.74–37.09, for AL9 alloy 61.40–39.90 kJ/mol. The mechanism of influence of strontium on the kinetics of oxidation of melts AL-2, AL4 and AL9 has been established. Aluminum oxide Al2O3 plays a dominant role in the formation of a protective oxide film.