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

Abstract

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 Ti 2Ni and TiNi 3 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.