Exceptional thermal stability of additively manufactured CoCrFeMnNi high-entropy alloy with cellular dislocation structures

CoCrFeMnNi high-entropy alloy (HEA) was additively manufactured (AM) by laser powder-bed fusion (L-PBF). The AM CoCrFeMnNi has prominent cellular dislocation structures with a small number of Mn-rich oxides. The thermal stability of the AM CoCrFeMnNi was investigated by isochronal annealing treatment at various tem-peratures from 400 to 1300 degrees C for 1 h. Microstructural analysis shows slow dislocation recovery, retarded recrystallization process, and precipitation of additional Cr-Mn based oxides during thermal annealing, resulting in exceptional thermal stability and retained high hardness at elevated temperatures. By thermodynamic cal-culations, a low stored energy of 1.31 MJ/m3 and a high activation energy of 353 kJ/mol for recrystallization were estimated for the AM CoCrFeMnNi. The exceptional thermal stability of the AM CoCrFeMnNi HEA is mechanistically attributed to the low crystallographic misorientations across the dislocation cell walls, sluggish atomic diffusion, and the pinning effects of the oxide nanoprecipitates.

Automated summary

The AM CoCrFeMnNi alloy, produced by laser powder-bed fusion, exhibits prominent cellular dislocation structures and exceptional thermal stability with high hardness at elevated temperatures. The low crystallographic misorientations across the dislocation cell walls, sluggish atomic diffusion, and pinning effects of oxide nanoprecipitates are the key factors contributing to this outstanding thermal stability.