A Comprehensive Study on the Room-Temperature Rolling and Tensile Ductility of Refractory High-Entropy Alloys

Many refractory high-entropy alloys (RHEAs) offer exceptional high-temperature strength, yet their widespread application is hindered by limited room-temperature tensile ductility. While numerous intrinsic ductility metrics for RHEAs have been proposed through computation, their applicability to practical processing and tensile behavior remains unclear. This investigation integrates CALPHAD phase stability calculations with experimental arc melting, cold rolling, and standard tensile tests to elucidate the factors that govern the rolling and tensile ductility of a wide range of RHEAs at room temperature under as-cast and annealed conditions. Rolling ductility was established as a rapid screening criterion prior to tensile testing, revealing that the BCC miscibility gap driven by Group VI and Group IV elements, Zr-driven secondary phase formation, and rapid grain boundary Ti-segregation are the dominant extrinsic factors that suppress experimental rolling ductility despite favorable intrinsic metrics. Although rolling ductility identified promising candidates, subsequent tensile testing demonstrated that dendritic segregation and grain boundary embrittlement are more detrimental under tension, underscoring dominant extrinsic effects that are not considered in current ductility metrics based on ideal BCC single-phase materials. These findings provide critical guidelines for future RHEA design that must incorporate the interplay of thermodynamics, kinetics, and thermomechanical processing to achieve room-temperature tensile ductility in RHEAs.