In-situ study of room temperature tensile deformation of a CrMnFeCoNi high-entropy alloy

Emerging high-entropy alloys (HEAs) exhibit high strength, high ductility and high toughness relative to traditional alloys based on one or two principal elements. The superior mechanical properties are derived from a synergy of multiple deformation mechanisms and their interactions at different stages of plastic straining. It is thus important to uncover the activation and operation of deformation mechanisms in these materials for property optimization and potential structure applications. The present work carried out in-situ tensile deformation of a CrMnFeCoNi HEA at room temperature. The strain hardening rate did not change monotonically during tensile deformation. Surface morphology evolution revealed the effects of massive dislocation activity, activation of multiple slip bands and their interactions on the strain hardening rate. Crack-tip-opening-angle measurements show that the current alloy possesses high fracture toughness. Cracks initiated at dense slip zones and grain boundaries, and propagated gradually, eventually coalescing into main cracks and resulting in final fracture.