Excellent creep resistance with synergistic strengthening mechanisms of a lightweight single-crystal high-entropy superalloy

Developing lightweight superalloys with excellent high-temperature creep resistance has long been a significant challenge for aerospace and energy applications. In this study, we present a single-crystal high-entropy superalloy (HESA) characterized by a pronounced dual-high-entropy effect where both the γ and γʹ phases feature multi-component configurations. The resulting HESA exhibits a remarkable synergy of low mass density (8.16 g cm⁻³) and an elevated γʹ solvus temperature (1238 °C), with an outstanding creep performance at 850–900 °C under compressive stress of 500–400 MPa. Notably, the minimum creep rate at 850 °C/400 MPa (∼4.0 × 10⁻⁹ s⁻¹) is nearly two orders of magnitude lower than that of conventional W-free Co-based alloys and comparable to that of Re-containing Ni-based single crystals. Such superior creep resistance could be attributed to a dual high-entropy effect on both thermodynamic stability and deformation kinetics. Thermodynamically, the entropy-driven stabilization enhances the microstructural stability of the alloy and suppresses the formation of detrimental phases during the prolonged creep process. Kinetically, the atomic-scale, chemically complex environment creates a rugged fault energy landscape that effectively influences dislocation dynamics, promoting multiple deformation mechanisms, including dense interfacial dislocation networks, antiphase-boundary-coupled superpartials, and microtwins. These substructures and their interactions further inhibit the motion of dislocations for a sustained creep resistance. Furthermore, we identified a novel microtwinning mechanism mediated by the coordinated glide of a pair of dissimilar 90° and 30° 1/6〈112〉 Shockley partials on consecutive {111} planes, coupled with a unique one-step atomic shuffling process. Our findings offer mechanistic insights into creep behaviors of HESAs and demonstrate a promising strategy for the development of lightweight superalloys with superb high-temperature capabilities.