Co-effect of heat and direct current on growth of intermetallic layers at the interface of Ti-Ni diffusion couples

The growth of the intermetallic layers at the interface of Ti-Ni diffusion couples was investigated under the co-effect of heat and direct current. Isothermal diffusion treatments for Ti-Ni couples were conducted at 500, 600 and 700 °C for 5, 10 and 15 h with and without the passage of DC current of 10 A intensity. It was found that both Ti₂Ni and TiNi₃ layer form at the Ti-Ni interface in all couples treated by different process, but TiNi layer forms in the couples annealed above 600 °C without current or at 500 °C with current. The growth of the whole interfacial layer shows a parabolic relationship with time. The apparent activation energy of growth for the whole interfacial layer is 83.76 kJ/mol in the couple treated by heating without a current, and it decreases to 42.11 kJ/mol in the couple treated with a direct current of 10 A during heating. The effect of the current on the growth of different intermetallic layers varies with its direction.