Wetting and reaction characteristics of AL₂O₃/SIC composite refractories by molten aluminum and aluminum alloy

The reactive wetting behavior in molten aluminum (Al) and Al alloy was investigated for alumina-silicon carbide composite refractory materials using an optimized sessile drop method at 900°C in a purified Ar-4% H₂ atmosphere. The time dependent behavior of the contact angle and drop geometry was monitored and the wetting kinetics were determined. The initial contact angle between the liquid Al/Al alloy and the refractory substrates was found to be greater than 90° and to gradually decrease with time. For two of the materials, it was found that the contact angles decreased to and angle less than 90° by the end of the two-hour test. For the third material, the contact angle was still greater than 90° at the conclusion of the two-hour test. The difference in wetting properties among the three types of refractories is attributed to their microstructural and compositional variations. The effect of magnesium in the molten Al alloy drops on the wetting kinetics and the reaction with the refractory substrates are also discussed. The results obtained provide important understanding of the wetting and corrosion mechanisms of alumina and silicon carbide materials in contact with molten aluminum.