Wettability of carbon by aluminum and aluminum alloys

Wetting (both equilibrium contact angle and spreading kinetics) of aluminum and aluminum alloys with silicon and titanium on carbon substrates is investigated as a function of temperature and carbon microstructure. Experiments are carried out by the sessile drop technique under high vacuum, in the range from 1023 to 1250 K. Three different types of carbon substrates are examined: vitreous carbon, pyrolytic carbon and graphite pseudo single crystals. It is shown that an increase in temperature and a decrease in the preferred orientation of the graphite basal planes with respect to the substrate surface greatly enhance the three-phase line reactivity and the spreading kinetics. From a practical point of view the results obtained in this study show that in processes involving short-time contact (up to a few minutes) between deoxidized molten Al (or Al–Si and Al–Ti alloys) and carbon at T<1273 K, aluminum (or aluminum alloys) does not wet carbon whatever the microstucture and texture of graphite material.