Solid-solution hardening with nitrogen of CoCrFeMnNi high-entropy alloy single crystals

In this study, we found that during tensile strain alloying with nitrogen up to 1.2 at % of the [001]- and [1̅11]- oriented crystals of the fcc CoCrFeMnNi high-entropy alloy (HEA) leads to strong solid-solution hardening, an increase in the temperature dependence of critical resolved shear stresses (CRSS) τcr(T) and an increase in the stacking fault energy γ0 relative to crystals without nitrogen. CRSS tcr in the CoCrFeMnNi HEA single crystals without nitrogen and with nitrogen were found to be independent of the crystal orientation within a wide temperature range of 77–973 K. In the [001]- and [1̅11]-oriented crystals of the fcc CoCrFeMnNi HEA, alloying with nitrogen leads to the development of a planar dislocation structure with dislocation pile-ups at T = 296 K, whereas there were no dislocation pile-ups in these crystals without nitrogen. The strain hardening coefficient (Θ = dσ/de) at the linear hardening stage was found to depend on the crystal orientation due to the influence of crystal orientation and nitrogen alloying on the nature of the developing dislocation structure and deformation twinning.