Site preference of Zr in Ti3Al and phase stability of Ti2ZrAl

Abstract

The site preference of Zr atoms in Ti3Al and the phase stability of Ti2ZrAl are examined using first-principles electronic structure total energy calculations. Of the sixteen possible ways in which Ti, Zr and Al atoms can be arranged, in the lattice sites corresponding to D019 structure of Ti3Al, to obtain Ti2ZrAl, it is shown that Zr atoms prefer to get substituted at the Ti sites. It is further shown that among the seven crystal structures considered, D019-like and L12-like are the competing ground-state structures of Ti2ZrAl. The above results are in agreement with the experimental results reported in the literature. Calculated values of equilibrium lattice parameters, heat of formation and bulk modulus of Ti2ZrAl are presented. The basis for the structural stability and bonding are analysed in terms of the density of states. Between the two possible B2-like structures, Ti2ZrAl shows enhanced stability for the one where Zr is substituted in the Ti sublattice, which again is in agreement with the experimental observation.