Electronic structure and bonding in titanium carbosulphide

摘要

Titanium carbosulphide (Ti2CS) is encountered as an inclusion phase in Ti-containing steels. Ductile fracture in steels is associated with the growth and coalescence of voids initiated at second phase particles such as inclusions. When S in steels is gettered as Ti2CS rather than as the more common manganese sulphide (MnS), a significant improvement in fracture toughness can be obtained when the fracture mode is ductile. This improvement is believed to be associated with the higher strains required for void nucleation ar the particle-matrix interface when the particles are Ti2CS. The enhanced void nucleation resistance of Ti2CS particles may be due to stronger interfacial bonding. To begin to understand the nature of the metal-inclusion interfacial bonding, it is first essential to understand the bonding characteristics within the individual phases present at the interface. This paper investigates the bonding characteristics of bulk Ti2CS. The ground state properties of Ti2CS have been investigated using two ab initio electronic structure calculation techniques, namely, the Layer-Korringa-Kohn-Rostoker and the linear muffin tin orbitals methods. The bonding in the structure is analyzed using the band structure, the electronic density of states and the charge density. The equilibrium lattice constant predicted from the calculations is within 3% of that reported experimentally. The bulk modulus has been calculated to be approximately 2.5 Mbar. Our results indicate that the bonding in the structure is complex, and exhibits covalent, ionic and metallic features. [References: 18]