Aluminum-induced impediment of edge dislocation for high-temperature strengthening in the single-phase refractory high entropy alloy

Achieving high-temperature strengthening in single-phase refractory high-entropy alloys (RHEAs) is critical for structural applications, yet the strengthening mechanism of Al remains unclear. Here, the effect of Al on the high-temperature behavior of single-phase BCC Ti₃₅V₃₅Nb₁₀Mo₂₀ RHEA is investigated through combined experiments and simulations. The Al-containing alloy exhibits significantly enhanced yield strength and specific strength at 800–1000 °C. Microstructural analysis reveals that plastic deformation is dominated by dislocation slip, with the dominant carriers transitioning from screw to edge dislocations as temperature increases. Calculations show that Al markedly raises the critical activation stress for dislocations, especially screw dislocations. Moreover, Al does not strengthen via conventional elastic or chemical solid-solution effects, but hinders edge dislocation motion through localized electronic interactions and suppresses edge dislocation climb by increasing vacancy migration barriers. These findings clarify the electronic and diffusion origins of Al-induced high-temperature strengthening in single-phase BCC RHEAs.