A combinatorial experimental approach and modelling of solid solution strengthening in CrMnFeCoNi-based high entropy alloy systems
Concentration dependent solid solution strengthening has been a topic of interest in high entropy alloy (HEA) research for several years. In the present work diffusion couples based on the established Cantor alloy are used to investigate solid solution strengthening in chemically complex alloys. A key approach is related to the continuous variation of the alloying content and the direct correlation of local hardness and composition. The aim was to elucidate solid solution strengthening mechanisms in a continuous manner and to compare experimental data to predictions from conventional (Labusch) and more recent (Varvenne) models over broad concentration intervals. Additionally, atomistic computer simulation show considerable fluctuations in the shear modulus and strong deviations in the elastic constants of the constituents between thermodynamically stable phases and the present FCC phase, challenging the homogeneous average background assumption of the Varvenne model and the usage of the constituents elastic constants of their stable phases as input for solid solution strengthening models. The Labusch model has been fitted to experimental data and confirms Cr as the most potent strengthening element. For comparison of the experimental hardness and the predicted yield strength of the Varvenne model, a concentration dependent correlation factor is introduced to account for strain hardening during indentation, which gives good agreement between experiment and model.