Thermodynamic Coffee Lecture – Augmented tracer-interdiffusion couple method: a high-throughput approach for consistent measurements of the tracer diffusion coefficients

The radiotracer method is used for decades for determination of tracer diffusion coefficients in homogeneous alloys under (quasi)equilibrium conditions. Alternatively, diffusion couples are commonly utilized to determine the interdiffusion coefficients in binary and ternary alloys under chemical gradients and related vacancy fluxes. Recently, we elaborated an augmented tracer-interdiffusion couple approach to measure the compositionally-dependent tracer diffusion coefficients along the whole diffusion paths in multi-component alloys of any complexity. First, the method will be introduced for the binary Fe-Ga and Ni-Fe and ternary Cu–Fe–Ni systems. The comparison of the tracer diffusion data from homogeneous alloys and those from diffusion couples elucidates the importance of accounting for non-equilibrium vacancies in the diffusion couples. Second, diffusion properties of single-phase multi-principal element (often called as “high-entropy”) alloys will be presented and discussed with respect to the interplay of crystalline structure, lattice distortions and point defect properties.