Enhanced ductility in hot compression tests by tailoring microstructure in the refractory high-entropy alloys MoNbTaTiV_xZr

Due to their brittleness, refractory high-entropy alloys (RHEAs) are still limited in industrial applications. Modifying the alloy composition to tailor the microstructure has been identified as a promising approach to enhance the ductility of RHEAs. In this study, assisted by the CALPHAD-method, we investigate the effect of vanadium addition to the base composition MoNbTaTiZr (V₀). We find that the introduction of soft V-rich inclusions in the interdendritic region of the alloy MoNbTaTiV_0.6Zr (V_0.6) changes the brittle fracture behavior of V₀ at 800 °C to ductile while maintaining a yield strength above 800 MPa. This enhanced ductility is due to the strain localization caused by the V-rich inclusions and their refinement during plastic deformation. The refined inclusions also exhibit the ability to impede crack propagation, resulting in the transformation of straight cracks into branched cracks. This work not only presents an approach to improve the ductility of RHEAs, but also provides new insights into exploring the wide range of RHEAs.