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Precipitates of the topologically close-packed (TCP) phases can significantly impact a material’s mechanical and fracture properties. This theoretical study uses ab initio modeling to investigate the phase of WOs, focusing on composition-dependent mechanical and fracture-related properties. We find the effect of Os on WOs to be stronger than that of Re in WRe phase, with the WOs phase exhibiting peak hardness at the ideal concentration. This difference is attributed to variations in -orbital filling, causing Os to favor low-coordination sites more strongly than Re. While ductility may improve at high Os contents, brittle fracture of the phase is still predicted. For Os concentrations above 78 at.%, the phase becomes mechanically unstable. These results indicate that subtle changes in -orbital filling between Os and Re significantly affect the stability and mechanical properties of the phase and may apply to similar TCP phases.
Vesti et al. (2026) studied this question.