ABSTRACT
Equiatomic CoCrFeMnNi high entropy alloy has been very well-known in scientific community as a material offering outstanding structural properties at a wide range of temperature. To realize this potential, interstitial alloying with various elemental additions has been employed in the past. Carbon has been the primary and the most popular interstitial addition to CoCrFeMnNi so far. This review summarizes the large body of work which has been done to establish the structural benefits of carbon addition to CoCrFeMnNi. The effect of carbon addition to CoCrFeMnNi is discussed at different length scales starting from the lattice level to the microstructural level and finally at the macro-mechanical level. At the lattice level, the effect of carbon addition on stacking fault energy and its effect on deformation mechanisms like TWIP and TRIP are discussed. The effect of carbide precipitation on the microstructure is reviewed at the microstructural level, along with the concurrent changes in mechanical properties like strength, hardness, and strain hardening rate at the macro level. In the second part of this review, the effect of 2 wt.% graphite flake addition on the microstructure of CoCrFeMnNi synthesized by mechanical alloying and spark plasma sintering is presented.
