A first-principles study on the mechanical and thermodynamic properties of (Nb1-xTix)C complex carbides based on virtual crystal approximation

Effects of component and temperature on mechanical and thermodynamic properties of (Nb1-xTix)C complex carbides were studied. The results show that it is easier to mix a small amount of NbC with TiC to form Ti-rich complex carbides than mixing small amounts of TiC with NbC to form Nb-rich complex carbides. Elastic modulus, hardness, ductility and fracture toughness of the complex carbide can be optimized by controlling the fractions of Nb and Ti in the complex carbide. The electronic property analysis on the complex carbides reveals that strong metal-metal and metal-carbon interactions exist in NbC, while strong metal-carbon interactions but weaker metal-metal interactions in TiC. The metal-metal interactions in the complex carbides attenuated when Nb is replaced by Ti. The bulk modulus and linear thermal expansion coefficient of the complex carbides demonstrate that a small amount of Ti atoms in the complex carbides may effectively alleviate the loss of the bulk modulus at elevated temperatures.