The role of rhenium and tantalum alloying on the mechanical behaviors of tungsten-based micropillars

Tungsten (W) and its alloys are widely used in micro-nano electronic fields, making the understanding of size and alloying effects on mechanical properties and deformation behaviors at these scales increasingly significant. In this study, the mechanical properties and deformation mechanisms of pure W, tungsten-rhenium (W-3Re), and tungsten-tantalum (W-3Ta) alloys were systematically investigated via micropillar compression. The results reveal that Re and Ta alloying exert distinct effects on the yield strength of micropillars with diameters ranging from 1 μm to 5 μm (Re decreases, Ta increases this property), with the strength value is positively correlated with the stress required for dislocation nucleation. Deformation behavior exhibits a marked dependence on both micropillar size and alloying. At the 1 μm scale, the size effect plays a dominant role. The pronounced surface image force enhances the mobility of screw dislocations, inducing localized slip deformation dominated by mixed dislocations in all specimens. At larger diameters of 3 μm and 5 μm, the plastic deformation of pure W is governed by the cross-slip of screw dislocations, resulting in homogeneous slip deformation. In constant, the plastic deformations of W-3Re and W-3Ta alloys are dominated by localized slip, which is attributed to the increased mobility of screw dislocations. Further analyses show that Re alloying reduces the Peierls barrier for screw dislocations motion and thereby enhances their mobility. Differently, Ta alloying increases this barrier but reduces the activation volume required for kink pair nucleation, ultimately improving the mobility of screw dislocations.