Composition-dependent interdiffusivity matrices of ordered bcc_B2 phase in ternary Ni-Al-Ru system at 1273∼1473 K

In this paper, 5 Ni-Al-Ru ternary and 2 NiAl/RuAl binary equilibrium alloys were prepared, and their lattice parameters were evaluated by using the X-ray diffraction technique. The relation between the lattice parameters and Ru content satisfies Vegard's law, confirming that a continuous single bcc_B2 phase exists between NiAl and RuAl in the ternary Ni-Al-Ru system. After that, three diffusion couples located in the bcc_B2 phase region were prepared at 1273, 1373 and 1473 K, respectively. With the presently measured concentration profiles, the composition-dependent interdiffusivity matrices along the entire diffusion paths were efficiently determined by using the High-throughput Determination of Interdiffusion Coefficients (HitDIC) software. The obtained interdiffusivities show a good agreement with the limited experimental data in the literature. Furthermore, the present results show that the addition of Ru to bcc_B2 NiAl alloys can significantly inhibit the interdiffusion rate of Ni, indicating that the bcc_B2 Ru-containing NiAl bond coats can serve as a potential diffusion barrier for Ni-based superalloy substrate.