Effect of carbon addition and recrystallization on the microstructure and mechanical properties of CoCrFeMnNi high entropy alloys

Abstract

The effect of carbon addition on the cast and rolled microstructures of CoCrFeMnNi high entropy alloys were studied. Both as-cast CoCrFeMnNi and CoCrFeMnNiCo.i alloys have a dendritic microstructure. Small carbide particles were observed at the inter-dendritic region in the as-cast CoCrFeMnNiC0.1 and elongated-grained structure with aligned carbides were developed at grain boundaries in CoCrFeMnNiCo.i after homogenization. The grain size decreased from 9.2 μm to 5.8 μm with the addition of 0.1 wt% carbon. The decrease in grain size is due to its high stored cold work energy during deformation processing, resulting in more active recrystallization in CoCrFeMnNiC0.1 and the pinning effect of carbides. The strengthening in CoCrFeMnNiC0.1 is most likely attributed to solid solution strengthening and nanoscale carbide strengthening, because grain size strengthening was found to be not as effective.