A strong-yet-ductile high-entropy alloy in a broad temperature range from cryogenic to elevated temperatures

Developing strong-yet-ductile alloys with wide temperature capabilities is crucial for modern industrial and scientific applications; however, this is often difficult to realize using conventional wisdom. In this work, we innovatively designed a nanoparticle-strengthened high-entropy alloy (HEA) through elaborate compositional design and thermomechanical regulation. The designed HEA exhibits extraordinary mechanical properties across a wide temperature range (−196∼1000 °C), resulted from the unique microstructures consisting of high-density hierarchical L1₂ nanoparticles combined with serrated grain boundaries. A high ultimate tensile strength of 1355 MPa combined with a ductility of 35.0 % were achieved when tested at 25 °C. The tensile strength and ductility were enhanced simultaneously with the decrease of temperature from 25 to −196 °C. More prominently, the intermediate-temperature intergranular embrittlement, a severe ductility loss at 600∼800 °C for most conventional superalloys, is effectively suppressed even under high tensile stress, which is attributed to the high resistance to crack propagation of serrated grain boundaries. An apparent anomalous yielding behavior occurred at 700 °C, leading to an ultrahigh yield strength of ∼1045 MPa while maintaining a large ductility of ∼22.1 %. Meanwhile, an excellent strength of 325 MPa can still be maintained even at 1000 °C combined with a good ductility over 25 %. Systematic characterizations revealed that such a temperature-dependent mechanical behavior is highly related to various deformation substructures activated at different temperatures. This work would open a pathway to developing a series of advanced alloys with superior strength and ductility over a wide temperature range. © 2024 Acta Materialia Inc.