A Co-rich chemically complex intermetallic alloy with extraordinary strength-ductility synergy

High-strength ordered intermetallic alloys are always sought-after in sophisticated structural applications. However, their practical applications have long been hindered by the severe grain-boundary embrittlement. Here, we designed a Co-rich chemically complex intermetallic alloy (CCIMA) with the L1₂-type ordered structure, which exhibits an ultrahigh tensile strength of ∼1,611 MPa and a substantial ductility of ∼37%. These exceptional strength-ductility combination outperforms the majority of common Co-rich intermetallic alloys. The multi-addition of Ta, Ti, and V elements is largely responsible for the significantly increased antiphase boundary energy of the L1₂ superlattice, which accounts for the high strength. This high degree of ductility is attributed to both the increased fracture resistance of grain boundaries brought about by co-segregation-induced order-to-disorder phase transformation, as well as the high work-hardening capability. © 2023 Acta Materialia Inc.