Medium-entropy CoCrNi alloy with a face-centered cubic (FCC) structure has high ductility but low yield strength at temperatures above 293 K. Alloying with Nb and Mn can overcome this drawback through solid-solution strengthening. However, the risk of forming intermetallic compounds requires careful selection of compositions to maintain ductility. In this work, based on three independent thermodynamic criteria, an analysis was carried out on more than 194 thousand alloys, from which 31 compositions with a stable FCC solid solution were determined. The yield strength was calculated in the temperature range from 77 to 673 K using a theory of solid-solution strengthening for disordered alloys, which takes into account the elastic interaction of dislocations with solute atoms. Co-alloying of Nb (2 at.%) and Mn (2–6 at.%) in the Nb–Co–Cr–N–Mn system allows for a 1.5–1.6 times increase in yield strength at 673 K compared to the CoCrNi alloy. At the same time, the selected compositions are predicted to have a stable FCC solid solution without embrittling intermetallics.
Osintsev et al. (Wed,) studied this question.