Achieving High Tensile Strength and Ductility in Refractory Alloys by Tuning Electronic Structure

Energy efficiency of heat engines (gas and steam turbines) for electricity production and propulsion scale with operating temperature following the Carnot cycle. Commercial Ni- and Co-based superalloys melt near 1500°C and rapidly lose mechanical strength beyond 1000°C. Refractory metals melt well above 2000°C but have inherent manufacturability challenges, like high ductile-to-brittle transition temperatures, that are significant barriers to adoption. Using density-functional theory guided design, we demonstrate tailored local lattice distortions that promote phase-stable, non-equiatomic refractory concentrated solid-solutions with both high ductility and strength. We exemplify this for single-phase, body-centered cubic Nb4Ta4V3Ti that exhibits castability, excellent room-temperature tensile yield strength (>1 GPa) and ductility (>20% uniform elongation), and exceptional high-temperature tensile strength (500 MPa at 1000°C). These findings illustrate a path for designing materials that hold great potential for advancing next-generation technologies like Gen-IV fission reactors, first-generation fusion-plasma reactors, and more efficient gas turbines for electricity generation and propulsion.