Phase competition in ternary Ti–Ni–Al system

•Ti–Ni–Al Wagner integral diffusion coefficients.•Experimental results of Ti–Ni–Al diffusion at 1173 K.•Diffusion couple technique in studying the phase relations.•Entropy production hypothesis of choosing the diffusion path.

In this paper the reactive diffusion in Ti–Ni–Al system is discussed at 1173 K. The calculation method based on the binary approach is presented. The key kinetic parameter is Wagner integral diffusion coefficient. The experimental and simulation results of reactive diffusion between pure Ti and ββ-NiAl are compared at 1173 K after 100 h.