Tailoring bimodal grain size structures in nanocrystalline compositionally complex alloys to improve ductility

The feasibility of engineering bimodal grain size distributions to achieve superior mechanical properties was explored in two face-centered cubic compositionally complex alloys, namely CrMnFeCoNi and its high-performance subvariant CrCoNi. Therefore both alloys were processed down to the nanocrystalline grain size regime by utilizing high-pressure torsion and subsequently annealed at intermediate temperatures. Especially the CrCoNi alloy is prone to formation of bimodal microstructures and for an annealing treatment at 500 degrees C for 100 h an excellent combination of ultra-high tensile strength, exceeding 1500 MPa, and decent ductility with elongations to failure of 10% could be achieved.