First-Principles Prediction of the Elastic Anisotropy, Thermodynamic and Tensile Properties of Ti2ax (a = Al and Ga, X = C and N) Max Phases

In this paper, the structure properties, elastic anisotropies, thermodynamic and tensile properties of Ti 2 AX (A = Al and Ga, X = C and N) MAX phases are studied by first-principles calculations. The results show that these MAX phases have thermodynamical, dynamical, and mechanical stabilities. The calculated anisotropy indexes indicate that the MAX phases are anisotropic in elastic modulus. Ti-X chemical bonds possess covalent-ionic mixed nature. Moreover, the sound velocities and thermal conductivities of these Ti 2 AX MAX phases are also anisotropic. According to the tensile calculation, the tensile strength along the [110] direction is greater than that along the [001] direction, and fracture failure will occur in the [110] direction.