Development of Ductile Refractory Alloys With Excellent High-Temperature Strength for Extreme Environments

The demand for alloys capable of withstanding extremely high temperatures has grown significantly in the aerospace industry. The alloys need to maintain sufficient strength at ultra-high temperatures, while still having adequate forming ability to manufacture the hot-end components. Refractory alloys, including refractory medium- and high-entropy alloys, have been widely recognized as the promising candidates to operate in extreme environments. This review aims to comprehensively assess the mechanical properties of ductile refractory alloys over a broad temperature range. We first present the fabrication methods available for preparing bulk refractory alloys. Several important topics regarding their mechanical properties are then discussed, such as ductile-to-brittle transition, strength-ductility trade-off at room temperature, and high-temperature tensile strength and creep resistance. We also summarize the toughening and strengthening strategies often used towards strength-ductility synergy in refractory alloys. The catastrophic oxidation at elevated temperatures, another critical issue for limiting their widespread applications, is further discussed briefly. Finally, this overview provides an outlook on the challenges and perspectives in this cutting-edge field.