A. G. Lipnitskii

Grain boundary segregation of C, N and O in hexagonal close-packed titanium from first principles

Grain boundary segregation of light interstitials is one possible mechanism of thermal stability in commercially pure nanostructured titanium alloys. This paper uses first-principles calculations to show that the independent segregation of C, N and O atoms at a ?7 high angle grain boundary in ?-Ti is energetically unfavourable. The presence of interstitial elements near the grain boundary plane increases the grain boundary width and the specific formation energy.

The impact of carbon and oxygen in alpha-titanium: ab initio study of solution enthalpies and grain boundary segregation

The solution, grain boundary (GB) segregation, and co-segregation of carbon and oxygen atoms in α-titanium are studied using density functional theory. For five titanium tilt boundaries, including T1, T2, and C1 twin systems, we determine the GB structure, as well as GB energy and excess volume. The segregation energies and volumes of carbon and oxygen are calculated for 23 inequivalent interstitial voids, while for co-segregation 75 configurations are considered. It is obtained that depending on the type of the segregation void both a positive and a negative segregation process is possible. The physical reasons of segregation are explained in terms of the analysis of the void atomic geometry, excess volume and features of the electronic structure at the Fermi level. Although carbon and oxygen show qualitatively similar properties in α-Ti, several distinctions are observed for their segregation behavior and mutual interactions.