First-principles investigation on solution hardening of interstitial impurity elements (O, N) in gamma-TiA1

We have calculated the electronic structures of O-doped and N-doped gamma -TiAl using the first-principles discrete variational method (DVM) with the aim to understand the solution hardening effects of oxygen and nitrogen in gamma -TiAl. Our combination analysis on the electronic density, density of states (DOS) and the local environment total bond orders (LTBO) will show that, X atom (X is O or. N) can strongly bind with its six surrounding atoms via electronic hybridizations of Ti-3d/X-2p and Al-3p/X-2p. As a sequence, there forms a "hard" cohesive region around the impurity atom. A pinning model based on the calculations is proposed to explain the hardening effects. The consistent results are obtained between the present calculation and formal test experiments.