Synergistic creep strengthening by multi-component L12 and MC carbides in an additively manufactured hierarchical heterostructure

An additively manufactured hierarchical triple-phase heterostructure, comprising a face-centred cubic (FCC) matrix, multi-component L12 precipitates, and nanoscale MC carbides, is engineered in a Ni-rich multi-component alloy through the composition-guided design and tailored heat treatments informed by thermodynamic calculations. The chemically complex L12 precipitates with a bimodal-size distribution exhibit markedly increased antiphase boundary energies and critical resolved shear stresses, while the coherent multi-component MC carbides provide persistent Zener-pinning effect, jointly stabilizing grain and phase boundaries during high-temperature creep. These synergistic strengthening pathways suppress dynamic coarsening and dislocation motion, thereby enabling exceptional creep resistance at 900°C under high applied stresses.