High-throughput nanoindentation study on annealing-induced microstructural evolution and local creep behavior of NiAlCrFeMo high-entropy alloy

High-entropy alloys (HEAs) exhibit excellent mechanical properties at room temperature, yet their microscale creep behavior and the associated thermo-mechanical stability mechanisms remain insufficiently understood. This study employs high-throughput nanoindentation to systematically investigate the influence of high-temperature annealing on the microstructural evolution and localized creep behavior of a NiAlCrFeMo HEA. After annealing at 700 °C, the precipitation of a cross-lamellar L1₂’ phase and α-Cr particles within the interdendritic B2 phase, coupled with the contraction of the L1₂-envelope, collectively enhances hardness and creep resistance in this region. At higher annealing temperatures of 1000 °C and 1200 °C, coarsening of the L1₂ phase and dissolution of precipitates within the B2 phase occur, which markedly weaken the pinning effect on dislocations and consequently reduce the creep resistance. Nanoindentation creep tests reveal that both phases and phase boundaries undergo predominantly transient and steady-state creep stages. Kinetic analysis based on stress exponents and activation volumes indicates that the creep mechanism is primarily governed by dislocation motion. This study reveals the micromechanism by which annealing-induced precipitation phase evolution modulates dislocation activity to influence the local creep behavior of multi-phase HEAs. This research provides a theoretical basis and process guidance for designing high-performance creep-resistant HEAs.