Evaluation of dislocation activities and accumulation in cold swaged CoCrFeMnNi high entropy alloy

The CoCrFeMnNi high entropy alloys (HEAs) performs large work strengthening with excellent deform ability. The work strengthening and deformation mechanism are facilitated by dislocation activities and dislocation accumulation. In this study, the dislocation density and microstructure of the CoCrFeMnNi HEA were characterized by the neutron line profile analysis using convolution multiple whole profile (CMWP) method and EBSD in a comparison with a binary FeNi alloy. The CoCrFeMnNi HEA and FeNi alloy were plastically deformed by rotary swaging until 85% area reduction. The characteristics (e.g., low stacking fault energy, local variation with different atom species) rising from the high compositional complexity of the CoCrFeMnNi HEA cause different dislocation activities and levels of dislocation accumulation from the binary FeNi alloy. The dislocation density of the CoCrFeMnNi HEA continuously increased during the cold swaging and was significantly larger than the FeNi alloy. The larger dislocation accumulation of the CoCrFeMnNi HEA is facilitated by higher compositional complexity, extensive dislocation arrangement, and strong grain fragmentation. The increasing heterogeneity of dislocation distribution in the CoCrFeMnNi HEA was contributed by dislocation cell formation and increasing geometrically necessary dislocations (GNDs). The larger work strengthening in CoCrFeMnNi HEA is correlated with large total dislocation density during cold swaging. (c) 2021 Elsevier B.V. All rights reserved.

Automated summary

The CoCrFeMnNi high entropy alloy shows large work strengthening and excellent deformability due to dislocation activities and accumulation. The study uses neutron line profile analysis and EBSD to compare the dislocation density and microstructure of CoCrFeMnNi HEA with a binary FeNi alloy, finding differences in dislocation activities and accumulation. The larger work strengthening in CoCrFeMnNi HEA is correlated with a continuously increasing dislocation density during cold swaging.