L12 nanoparticles-strengthened Co2Ni2Cr medium entropy alloy showing an outstanding tensile property.

In this paper, we designed a new L1 2 nanoparticles-strengthened fcc-structured (Co 2 Ni 2 Cr) 85 Al 7.5 Ti 7.5 MEA. The high-density L1 2 nanoparticles with an average size of ∼57 nm are uniformly distributed in the grain with an average size of ∼37 μm. The volume fraction of L1 2 nanoparticles is up to ∼45%. The L1 2 nanoparticles can be identified as the (Ni,Co,Cr) 3 (Ti,Al) multi-component phase. Compared to the single-phase Co 2 Ni 2 Cr base alloy with a yield strength of ∼208 MPa and an ultimate tensile strength of ∼660 MPa, (Co 2 Ni 2 Cr) 85 Al 7.5 Ti 7.5 MEA possesses a much higher yield strength of ∼1125 MPa and an ultimate tensile strength of ∼1540 MPa while retaining an excellent ductility of ∼38%. The precipitation strengthening by L1 2 nanoparticles takes the largest contribution to the yield strength, and the contribution value is up to ∼712 MPa. The deformation mode is dominated by mechanical twins for Co 2 Ni 2 Cr base alloy and (Co 2 Ni 2 Cr) 85 Al 7.5 Ti 7.5 MEA, and the mechanical twins are more prevalent in the Co 2 Ni 2 Cr base alloy. • A new L1 2 nanoparticles-strengthened (Co 2 Ni 2 Cr) 85 Al 7.5 Ti 7.5 MEA is well designed. • The volume fraction of L1 2 nanoparticles with a mean size of ∼57 nm is up to ∼45%. • (Co 2 Ni 2 Cr) 85 Al 7.5 Ti 7.5 MEA has an excellent property (σ s ∼ 1125 MPa, σ b ∼ 1540 MPa, δ ∼ 38%). • L1 2 nanoparticles precipitation strengthening takes the largest contribution to strength. • The deformation mode is dominated by mechanical twins for (Co 2 Ni 2 Cr) 85 Al 7.5 Ti 7.5 MEA. [ABSTRACT FROM AUTHOR]