Mechanical properties of Ti3AlX (X = C, N): Ab initio study

Elastic properties of the alloys Ti3AlC and Ti3AlN are derived from the first-principles total energy calculations based on the full-potential linear muffin-tin Orbital (FP-LMTO) method. From the computed elastic constants, theoretical values of Young's modulus, shear modulus, Poisson's ratio, sound velocities and Debye temperature are evaluated. By analysing the ratio between the bulk and shear moduli, it is found that Ti3AlN is ductile in nature, whose ductility is expected to be greater than that of Ti3Al, whereas Ti3AlC is found to be brittle. The site-projected density of states and the charge density plots have been used to analyse the chemical bonding between the Ti6N and Ti6C cluster and the surrounding metallic lattice of Al atoms. This further reveals that the strong covalent nature of Ti-C bonds in Ti3AlC, together with the high Young, shear and bulk moduli, make the compound more brittle than Ti3AlN. Copyright (C) EPLA, 2009