A synergistic strategy for strengthening and corrosion resistance in chromium-modified ductile refractory high-entropy alloys

This work focuses on W₀.₄MoNb₁.₃TaTiCrx (x = 0, 0.25, 0.5, 0.75 at.%) refractory high-entropy alloys produced by vacuum arc melting. Their microstructure, mechanical behaviour and corrosion performance were systematically examined. X-ray diffraction and SEM confirmed a body-centered cubic matrix, with Laves phase formation increasing at higher Cr levels. A slight reduction in the lattice parameter and peak shifts toward higher angles indicated the substitution of larger atoms by smaller Cr atoms. Solid-solution strengthening analysis highlighted Cr’s role in enhancing strength. The alloy with x = 0.75 achieved the highest yield strength (~1550 MPa) but exhibited reduced ductility (~10% fracture strain) due to brittle intermetallic phases. Corrosion tests in 3.5 wt.% NaCl showed improved resistance with Cr addition, attributed to the protective Cr-rich oxide layers. Overall, Cr significantly influences phase stability, mechanical properties, and electrochemical behaviour, offering pathways for optimizing RHEAs for demanding structural applications.