Achieving significant strength–ductility synergy in a multicomponent alloy via L1₂ precipitates and twins dispersed in fine grains

Face-centered cubic (FCC)-structured multicomponent alloys typically exhibit good ductility but low strength. To simultaneously improve strength and ductility, a multicomponent alloy, Ni_43.9Co_22.4Fe_8.8Al_10.7Ti_11.7B_2.5 (at%) with a unique microstructure was developed in this work. The microstructure, which includes 17.8% nanosized L1₂ precipitates and 26.6% micron-sized annealing twins distributed within ~ 8 μm fine FCC grains, was achieved through cryogenic rolling and subsequent annealing. The alloy exhibits a yield strength (YS) of 1063 MPa, ultimate tensile strength (UTS) of 1696 MPa, and excellent elongation of ~ 26%. The L1₂ precipitates and high-density grain boundaries act as a barrier to the dislocation movement, resulting in a substantial strengthening effect. In addition, the dislocations can cut through the L1₂ precipitates that are coherent with the FCC matrix, whereas the twin boundaries can effectively absorb and store dislocations, leading to a high work-hardening rate. Furthermore, the stacking faults, Lomer–Cottrell locks, and 9-layer rhombohedral stacking sequence (9R) structures formed during tensile deformation significantly enhance strain hardening by blocking dislocation movement and accumulating dislocations, resulting in excellent comprehensive tensile properties. Theoretical calculations reveal that the grain boundaries, L1₂ precipitates, and twin boundaries contribute the strengths of 263.8, 412.6, and 68.7 MPa, respectively, accounting for 71.9% of the YS. This study introduces a promising strategy for developing multicomponent alloys with significant strength-ductility synergies.