Infiltration and wetting of alumina participate preforms by aluminum and aluminum-magnesium alloys

Abstract

The infiltration and wetting of alumina participates by Al and by Al-Mg alloys was studied through pressure infiltration experiments. In these experiments, a noninvasive capacitance technique was used to determine the infiltration front position as a function of time. An unsaturated slug flow model was used to interpret the infiltration results and determine capillary pressures characteristic of the infiltration process. The characteristic capillary pressures for Al, Al-2Mg, and Al-3Mg at 750 °C and Al-2Mg at 850 °C were not significantly different. Therefore, contrary to usual belief, Mg did not significantly aid the pressure infiltration process. At 750 °C, the maximum values of the contact angle calculated from these capillary pressures were 106 deg for Al and 105 deg for Al-2Mg and Al-3Mg. These contact angle values indicate substantial removal of the oxide layer on the surface of the liquid metal during the infiltration process. The small difference in the contact angles indicates that magnesium had little effect on the wetting of alumina by aluminum. The small effect of Mg on the wetting may be due to absence of reactive wetting at the infiltration speeds present in the experiments and to partial disruption of the oxide layer on the surface of the liquid metal during the infiltration process.