INTERFACIAL PHENOMENA IN THE REACTIONS OF AL AND AL-TI MELTS WITH KF-ALF3 AND NAF-ALF3 MELTS

The interfacial phenomena occurring during the contacting of Al and Al -Ti melts with KF-AlF3 liquid fluxes have been investigated by optical examination of quenched metal drops previously immersed in the liquid fluxes. A range of temperatures between 690-degrees-C and 840-degrees -C was employed. Reactions in the Al-Ti/KF-AlF3 system involve the for mation of TiAl3 at the metal/flux interface. This TiAl3 is wetted by t he KF-AlF3 melt, and at 690-degrees-C the TiAl3 is dispersed in the KF -AlF3. At 720-degrees-C and above, a metal/flux emulsion is found in w hich there are high levels of K2TiF6 in the flux as a result of the di spersion of the TiAl3 surface layer in the flux. At low K2TiF6 levels, the TiAl3 is dispersed in the metal. Addition of Mg or Ca to the syst em in the form of MgF2 or CaF2 has been found to inhibit the formation of TiAl3, thus also inhibiting the metal/flux emulsification. A certa in critical level of Mg or Ca is required to prevent emulsification. T he results obtained for the Al-Ti/NaF-AlF3 system were in all cases si milar to those found for the Al-Ti/KF-AlF3 system.