Metallic materials used in extremely cold environments must maintain high strength, ductility and fracture toughness to support applications in aerospace, clean energy, superconducting systems and deep-space exploration. However, traditional alloys often suffer performance degradation at ultralow temperatures because of the long-standing trade-off between strength, ductility and toughness. Although metals may become stronger at lower temperatures, they can also become more brittle and prone to fracture.