First-principles investigation of the elastic properties and phase stability of (Ti1-xNix)C1-y ternary metastable carbides

Abstract

Recently, (Ti1-xNix)C1-y ternary metastable carbides have attracted considerable attention owing to their unique material properties; however, few studies have been conducted to reveal their elastic and phase stability properties. The present investigation revealed the elastic properties and phase stability of (Ti1-xNix)C1-y metastable carbides, depending on the nickel (Ni) and carbon (C) vacancy concentrations (x and y), using first-principles calculations. The results indicated that increasing the Ni and C vacancies generally reduced lattice parameters and elastic characteristics, particularly in the directional properties of carbides, such as shear and Young’s modulus. Debye temperature and Pugh’s criteria indicated that the rigidity and brittleness of carbides were effectively reduced by increasing the Ni and C vacancy concentrations. The degradation of the elastic properties caused by increasing the Ni content was explained by the low affinity of Ni and C, as well as the electron filling in the high-energy antibonding states of Ti–C bonds. First-principles thermodynamic analyses demonstrated that the generation of the C vacancy inevitably led to the formation of (Ti1-xNix)C1-y ternary metastable carbides based on thermodynamic stability. The results will elucidate the investigations on Ti-based ternary metastable carbide phases.