The tracer diffusion of 69Ga was measured in pure α-Ti, α2-Ti3Al (33at%Al) and γ-TiAl (54at%Al) over temperature intervals up to the upper limit of stability of the phase. The concentration profiles were determined by secondary ion mass spectroscopy. The diffusion coefficients were described by:

α-Ti:     D(m2/s) = 2.1 x 10-3exp[-295.5(kJ/mol)/RT]

Ti3Al:     D(m2/s) = 6.3 x 10-5exp[-315(kJ/mol)/RT]

TiAl:     D(m2/s) = 4.4 x 10-5exp[-293(kJ/mol)/RT]

The Ga diffusion behavior in the materials was explained in terms of the topology of the Ti sub-lattice in the compounds. The experimental data suggested that Ga behaved as an Al-substituting element in titanium aluminides. It was shown that Ga probably diffused in Ti3Al as antistructure-like defects via the Ti sub-lattice by nearest-neighbor jumps. The experimental data for Ga diffusion in TiAl could be explained by a predominant contribution from anti-structure bridge jumps.

Tracer Diffusion Behavior of Ga as an Al-Substituting Element in Ti3Al and TiAl Intermetallic Compounds. C.Herzig, M.Friesel, D.Derdau, S.V.Divinski: Intermetallics, 1999, 7[10], 1141-51