With the aim of obtaining a refining flux that is stable and provides effective refining of aluminum melt, a new strategy of designing the flux composition has been proposed. Ten fluxes were designed, by selecting ten molten salt compounds according to their thermophysical parameters, physical properties, and thermodynamic analysis. The melting points of the ten fluxes, and the phases transformation of the fluxes after melting, were studied by DSC and XRD, respectively. The contact angles between four groups of fluxes and alumina at refinement temperatures were studied, and the effect of refinement was characterized by a metallographic microscope. The process of the fluxes removing inclusions and degassing was analyzed thermodynamically. The research findings indicate that flux #10 (11.0 wt.%NaF, 29.5 wt.%NaCl, 46.5 wt.%Na2CO3, 3.0 wt.%CaF2, 10.0 wt.%Na3AlF6) has a melting point (562.2 °C) below the refining temperature. At the refining temperature (760 °C), flux #10 has the lowest contact angle, of 12.78°. In addition, compared to that of flux STJ–A3, currently used in practice, flux #10 has a better refining effectiveness, with the pores and inclusions content of the sample being reduced to 1.11% from 2.96%.
The kinetic mechanism of hydrogen absorption of the AA6111 alloy melt in different melting environments, and the in-situ real-time observation of the oxide film structure during the hydrogen absorption process were studied. The results show that the hydrogen absorption process of the aluminum alloy melt is related to the melting environment and the oxide film on the melt surface. The hydrogen content in the melt increases with the extension of time when the melting environment humidity and temperature are constant. The initial hydrogen content is also higher and the hydrogen absorption capacity of the melt is larger when the melting temperature is constant with an increasing melting environment humidity. The oxide film will fold over on itself and become porous, due to the change in the structure of the melt surface during heating. The surface of the melt is similar to the double-oxide-film defect hydrogen absorption carrier, which leads to the aggravation of hydrogen absorption. Hydrogen absorption kinetic equations for the aluminum alloy melt under different melting environments are obtained based on the experimental results.
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