The quest for advanced hard materials with enhanced ductility drives the exploration of novel ternary borides. In this study, we use evolutionary algorithm USPEX combined with ab initio calculations to systematically investigate the ternary W–Nb–B system. Our results successfully reproduce all known stable binary compounds and reveal a new structural motif for NbB2 (space group \(R\bar {3}m\) ). Building on this motif, we predict a series of thermodynamically stable and metastable ternary compounds forming a continuous WxNb1 – xB24 solid solution, with the 50% mixture W6Nb6B24 exhibiting the lowest energy of mixing. Analysis of mechanical properties reveals that tungsten incorporation systematically tunes elastic behavior: while hardness increases with W concentration, all predicted compounds retain remarkable ductility, outperforming traditional hard borides such as TiB2, ZrB2, and even WC according to the Pugh–Pettifor criterion. Fracture toughness values (2.4–3.4 MPa m0.5) are comparable to or exceed those of known refractory borides. These findings establish the W–Nb–B system as a promising platform for designing hard and ductile ceramics, demonstrating that strategic alloying within a common structural framework can reconcile the longstanding trade-off between strength and brittleness in ultra-high-temperature materials.
