Precipitate behavior in nitrogen-containing CoCrNi medium-entropy alloys

Abstract

The effect of nitrogen addition toward nitride precipitate formation and the corresponding behavior in a medium-entropy alloy system of N-CoCrNi was investigated. It was observed that the addition of N induced the formation of a Cr- and N-rich precipitate of Cr2N. Cr2N and the face-centered cubic (FCC) matrix in the N-CoCrNi system exhibited a Kikuchi orientation relation in the {111}γ//{0001}Cr2N plane and 〈110〉γ//〈11¯00〉Cr2N direction, where Cr2N was observed to be semi-coherent with the FCC matrix. The presence of Cr2N was also observed to contribute in the hindering of grain coarsening via Zener pinning pressure. The distribution of finer and higher fraction of Cr2N in the lower annealing temperatures of N-CoCrNi contributed more toward higher Zener pinning pressure compared to the coarser and lower fraction of Cr2N in the higher annealing temperatures, which subsequently affected grain growth during the annealing treatment.