Superior strength-ductility synergy of CoCrNiFeAlCu multi-component alloys

Based on the well-documented AlCoCrFeNi multi-component alloys (MCAs) systems, herein, superior synergic mechanical performance with ultimate tensile strength of 1.63 GPa and 2.18 GPa, and fracture strain of 18.8 % and 21.0 %, at room and cryogenic temperature (77K), respectively, were achieved by microalloying Cu. The roles of two-type precipitates of L1₂ and B2 precipitates in the Cu-added CoCrNiFe_0.62Al_0.38Cu_0.1 MCAs were characterized and analyzed through a combination of electron microscopy and tensile testing. Specifically, the added Cu element plays crucial role in forming the extremely small L1₂ nanoprecipitates that pronouncedly strengthen the MCAs and trigger plastic deformation in usually un-deformable B2 precipitates; and the interactions between dense/small L1₂ and hard/coarse B2 precipitates attributed to comprehensive strength/ductility behavior. Meanwhile, stacking faults and deformed twins induced by high stress are favorable for improving the plastic stability and extending the strengthening stage, resulting in excellent strain hardening in the MCAs.