Plastic deformation mechanisms in severely strained eutectic high entropy composites explained via strain rate sensitivity and activation volume

Eutectic high entropy composites (EHECs) are novel class of material with excellent combination of strength and ductility, thus having a large potential for industrial applications. However, the mechanisms operating behind the trade-off between strength and ductility has not been investigated in detail. In this work, the influence of severe straining imposed by high-pressure torsion (HPT) was evaluated for a series of CoCrFeNiNbx alloys with varying Nb content (x molar ratio), hypoeutectic (x = 0.25), eutectic (x = 0.65) and hypereutectic (x = 0.80) compositions. Strain rate sensitivity (m) and activation volume (V*) calculations were calculated from constant strain rate (CSR) nanoindentation experiments, revealing that dislocation interaction with lamellae interfaces become the rate-limiting step for the strength-ductility trade-off in these EHECs.