Solid-state reactive diffusion between Ti and Al was investigated at 520 to 650C by using multi-laminated Ti/Al diffusion couples. In samples which were annealed at up to 150h, TiAl3 was the only phase which was observed in the diffusion zone. The preferential formation of this compound in Ti/Al diffusion couples was predicted by using an effective heat-of-formation model. The present results indicated that Ti and Al diffused into each other, and that the growth of TiAl3 layers occurred mainly towards the Al side. The TiAl3 growth kinetics changed from parabolic to linear between 575 and 600C, and were characterized by activation energies of 33.2 and 295.8kJ/mol, respectively. It was suggested that the low-temperature kinetics were dominated by the diffusion of Ti atoms along the grain boundaries of the TiAl3 layers. Reaction at TiAl3/Al interfaces in the high-temperature regime was limited by the diffusion of Ti atoms in the Al foils. This was the result of an increasing solubility of Ti in Al with increasing temperature.

Growth of Intermetallic Layer in Multi-Laminated Ti/Al Diffusion Couples. L.Xu, Y.Y.Cui, Y.L.Hao, R.Yang: Materials Science and Engineering A, 2006, 435-436, 638-47