Probing the balance between ductility and strength: transition metal silicides

The adjustment of the balance between strength and ductility is still a great challenge for ultrahigh temperature materials. Essentially, the strength depends on the valence electron density of transition metals and the bond strength of chemical bonding. However, the ductility of a solid is mainly determined by the symmetrical slips and crystal structure. Based on the above design principles, we apply first-principles calculations to investigate the structure, elastic properties and brittle-or-ductile behavior of TM₃Sis with a cubic structure. Two new TM₃Si structures: Ti₃Si and W₃Si (space group: Pmn) are predicted. The calculated results show that W₃Si exhibits strong volume deformation and shear deformation resistances in comparison to TM₅Si₃. In particular, W₃Si also exhibits excellent ductility due to the symmetrical structure. The calculated electronic structure reveals that a high elastic modulus derives from the strong and symmetrical W–Si and W–W bonds. Therefore, we can control a crystal structure with symmetrical slips and choose a TM metal with a high valence electron density, to improve the correlation between ductility and strength.