Exploring the compositional parameter space of high-entropy alloys using a diffusion couple approach

In this paper the phase stability and solubility limits of high-entropy alloys are studied, using a diffusion couple approach. Diffusion couples have been fabricated using the established Cantor alloy (CrMnFeCoNi) and a commercial fcc CoNiCrMo alloy (MP35N®) with constituent or foreign elements as diffusion partners. Chemical gradients within the interdiffusion zone as well as the phase stability are quantified using EDX and EBSD. For comparability of the results, new phase stability diagrams are presented. The experimental results show no general correlation between maximum solubility of individual elements and atomic size mismatch, whereas the valence electron concentration model (VEC) seems to be a good approximation for fcc to bcc phase transitions for most of the investigated diffusion couples.