The Effects of Al and Ti Additions on the Structural Stability, Mechanical and Electronic Properties of D8m-Structured Ta5Si3

Abstract

Abstract:In the present study, the influence of substitutional elements (Ti and Al) on the structural stability, mechanical properties, electronic properties and Debye temperature of Ta 5 Si 3 with a D8 m structure were investigated by first principle calculations. The Ta 5 Si 3 alloyed with Ti and Al shows negative values of formation enthalpies, indicating that these compounds are energetically stable. Based on the values of formation enthalpies, Ti exhibits a preferential occupying the Ta 4b site and Al has a strong site preference for the Si 8h site. From the values of the bulk modulus (B), shear modulus (G) and Young's modulus (E), we determined that both Ti and Al additions decrease both the shear deformation resistance and the elastic stiffness of D8 m structured Ta 5 Si 3 . Using the shear modulus/bulk modulus ratio (G/B), Poisson's ratio (υ) and Cauchy's pressure, the effect of Ti and Al additions on the ductility of D8 m -structured Ta 5 Si 3 are explored. The results show that Ti and Al additions reduce the hardness, resulting in solid solution softening, but improve the ductility of D8 m -structured Ta 5 Si 3 . The electronic calculations reveal that Ti and Al additions change hybridization between Ta-Si and Si-Si atoms for the binary D8 m -structured Ta 5 Si 3 . The new Ta-Al bond is weaker than the Ta-Si covalent bonds, reducing the covalent property of bonding in D8 m -structured Ta 5 Si 3 , while the new strong Ti 4b -Ti 4b anti-bonding enhances the metallic behavior of the binary D8 m -structured Ta 5 Si 3 . The change in the nature of bonding can well explain the improved ductility of D8 m -structured Ta 5 Si 3 doped by Ti and Al. Moreover, the Debye temperatures, Θ D , of D8 m -structured Ta 5 Si 3 alloying with Ti and Al are decreased as compared to the binary Ta 5 Si 3 .

First‐principles investigation of solution mechanism of C in TM‐Si‐C matrix as the potential high‐temperature ceramics

“…[22][23][24][25] For example, the melting point of Ta 5 Si 3 is up to 2550 • C, which is much higher than the Ni-based superalloys. 26 Furthermore, the calculated bulk elastic modulus, shear modulus, and Young's modulus of Mo 5 Si 3 are 242 GPa, 126 GPa, and 323 GPa. 27 Unfortunately, the low fracture toughness and poor ductility hinder their high-temperature applications.…”

“…The results shown that the addition of Al and Ti improves the ductility of Ta 5 Si 3 matrix. 26 Guo et al studied the effect of Ag doping on the mechanical properties of Nb 5 Si 3 by using the first-principle method. The results show that Ag doping improves the ductility of Nb 5 Si 3 matrix.…”