Mechanical properties of Ti₃ AlX (X = C,  N): Ab initio study

Defence Metallurgical Research Laboratory, Kanchanbagh - Hyderabad 500 058, India

Corresponding author: kanchana.vaithee@gmail.com

Received: 14 May 2009
Accepted: 10 July 2009

Abstract

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.