Ultra‐Strong, Ductile, and Corrosion‐Resistant High Entropy Alloy With Multi‐Scale Heterogeneous Microstructure

Marine engineering materials require excellent mechanical properties and corrosion resistance to ensure safe service. However, balancing mechanical strengthening mechanisms with corrosion resistance in alloy design remains a considerable challenge. Herein, we design a multi‐scale heterogeneous microstructure, characterized by partial recrystallization, a grain‐size gradient, and L1 2 precipitates, by introducing different Al and Ti contents into a non‐equiatomic single phase face‐centered cubic (FCC) Co‐Cr‐Fe‐Ni high‐entropy alloy (HEA), followed by cold rolling and short‐term annealing. The designed Co 15 Cr 20 Fe 28 Ni 30 Al 3 Ti 4 HEA with multi‐scale heterogeneous microstructure exhibits an exceptional combination of mechanical and corrosion properties that surpass those of most reported alloys. It achieves a yield strength ( σ YS ) of 1980 MPa, an ultimate tensile strength ( σ UTS ) of 2005 MPa, and a total elongation of 12.1%. In terms of corrosion performance, it demonstrates a high corrosion potential ( E corr ) of −307.7 mV SCE , a low corrosion current density ( i corr ) of 145.7 nA/cm 2 , and a high pitting potential ( E pit ) of 854 mV SCE . The outstanding performance is attributed to the multi‐scale heterogeneous microstructure, which enhances mechanical properties through HDI and precipitation strengthening and promotes the rapid formation of a stable Cr‐enriched passive film. This work provides a viable pathway for designing high‐performance corrosion‐resistant alloys that simultaneously achieve high strength and good ductility.