Nanoparticle-strengthened multi-principal-element alloy with strength-ductility synergy over a wide temperature range

Achieving concurrent high strength and ductility across a wide temperature range remains a fundamental challenge in structural materials design. In this study, a Co 40 Ni 30 Cr 20 Al 5 Ti 5 multi-principal element alloy (MPEA) was developed using a CALPHAD-guided strategy to optimize phase stability and promote the formation of coherent L1 2 nanoprecipitates. High-resolution transmission electron microscopy (HRTEM) and atom probe tomography (APT) confirmed the presence of a high volume fraction (∼40%) of ∼20 nm L1 2 nanoprecipitates with minimal lattice mismatch embedded in an FCC matrix. These nanoprecipitates and grain structure exhibit excellent thermal stability upon long-term aging. Mechanical testing across a wide temperature range (-196 °C to 700 °C) revealed exceptional strength-ductility synergy, achieving a yield strength of 750 MPa, ultimate tensile strength of 1080 MPa, and elongation of 26% at 700°C. This superior performance is attributed to the intrinsically low stacking fault energy, which enables sustained activation of stacking faults and deformation twins, even at elevated temperatures. The combination of low SFE and thermally stable L1 2 precipitates governs the evolution of deformation mechanisms, from twinning and SF-mediated strengthening at cryogenic temperatures to dynamic strain aging and dislocation glide at high temperatures, while preserving planar defect activity up to 700 °C. This work establishes a thermodynamic and mechanistic framework for designing precipitation-strengthened MPEAs with exceptional performance in extreme environments.