Unraveling the solid solution effects of rhenium and tantalum alloying on the strength and ductility of tungsten single crystals

Tungsten (W) is a critical material for extreme environments, yet its inherent room-temperature brittleness significantly limits engineering applications. Alloying represents an effective strategy for improving its properties. Rhenium (Re) alloying enhances ductility, while tantalum (Ta) alloying increases strength. However, exploring the intrinsic effects of these alloying elements remains experimentally challenging, primarily due to the influence of extrinsic factors in polycrystalline W materials, such as grain boundaries. In this work, high-quality single crystals of pure W, W-3Re, W-3Ta, and W-3Re-3Ta alloys were successfully prepared using electron beam floating zone melting technique. The individual and synergistic mechanisms of Re and Ta elements were elucidated by means of room-temperature compression properties, post-deformation dislocation structures, and fracture morphologies of these single crystals. The softening observed in the W-3Re alloy is attributed to enhanced screw dislocation mobility, resulting in plastic deformation dominated by mixed dislocations. Conversely, the strengthening observed in the W-3Ta alloy stems from reduced screw dislocation mobility, with plastic deformation governed by long, straight screw dislocations. Benefiting from Re and Ta synergy, compared to pure W, the W-3Re-3Ta alloy exhibits higher yield strength (increased from 536.3 ± 5.4 MPa to 702.5 ± 8.2 MPa) and comparable compressive strain (40.0 ± 0.6 % vs. 41.2 ± 1.1 %).