Reaction diffusion in the Au-Ti system between 1110K and 1150K

The growth kinetics of the intermetallic compounds and of the β-Ti phase in the diffusion couples composed of Au and α-Ti were investigated in the narrow temperature range between the eutectoid temperature (α-Ti, β-Ti and AuTi₃ ) and the temperature of the α-β allotropic transformation of Ti. Four intermetallic compounds, Au₄Ti, Au₂Ti, AuTi and AuTi₃, predicted from the Au-Ti phase diagram have been observed in the diffusion zone. The Au₂Ti and AuTi₃ phases are not the stoichiometric compounds but have a narrow concentration range of about 1 at%. The layer growth of the four intermetallic compounds and the β-Ti phase obeys a parabolic law, namely the value of time exponent of layer growth is nearly equal to 1/2. The layer growth of the β-Ti phase is much faster than that of intermetallic phases. The Arrhenius relation of the growth rate constants of these layers have been observed. The activation energies for the layer growth of intermetallic compounds are found to be extremely high.