Understanding Interfacial Reactions in Ti–Ni Diffusion Couple

The diffusion phenomenon in the Ti–Ni binary system was investigated at a temperature of 1173 K. Microstructure and texture analysis revealed the formation of three stable intermetallic compounds, namely Ti(2)Ni, TiNi, and TiNi(3), as well as two metastable intermetallic compounds, including Ti(3)Ni(4) and Ti(2)Ni(3), at the interfacial diffusion zone. The nucleation surface energy increase was analytically estimated, and marker experiments were conducted using thoria particles, both of which showed that Ti(2)Ni was the first compound to form at the Ti–Ni diffusion interface. At a temperature of 1173 K, using the Wagner method, the integrated diffusion coefficients for the Ti(2)Ni, TiNi, and TiNi(3) phases were calculated to be 3.53 × 10(−12), 18.1 × 10(−15), and 6.2 × 10(−15) m(2)/s, for, respectively.