Ab initio study of Ti–C precipitates in hcp titanium: Formation energies, elastic moduli and theoretical diffraction patterns

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

“…Speaking about the possible mechanisms of thermal stabilisation in nanocrystalline pure titanium, the results of the present work are in favour of grain boundary pinning by bulk precipitates formed from solid solution [15].…”

“…The computational setup ensures that differences in the segregation energies of interstitials and formation energies of Ti grain boundaries are converged to within 25 meV and 0.05 J/m 2 , respectively. The method of calculation and Ti-C PAW potentials were checked by computation of lattice and elastic constants of several Ti and Ti-C phases in our previous study [15].…”

“…The calculations were performed under threedimensional periodic boundary conditions. An orthorhombic supercell containing 56 Ti atoms was constructed using calculated in our previous work [15] lattice constants of hcp Ti. The volume of cell was subsequently relaxed to account the influence of cell sizes and refine the values of lattice constants.…”

“…formed from solid solution) and (ii) lowering of driving force for grain growth and reduction of grain boundary mobility due to segregation of existing impurities [2]. The possibility of formation of Ti-C precipitates in α-Ti was considered in our recent work [15]. The purpose of the current work is to continue the investigation of thermal stability mechanisms in CP-nTi, considering the case of light impurity segregation at α-Ti grain boundaries in comparison with previous results of Ti-C particles formation.…”

“…Due to a technologically necessary heat treatment of implants during production, an improvement of their microstructure stability is a significant task, which needs first of all a detailed understanding of existing mechanisms of grain boundary stabilisation. CP titanium alloys (Grade 1-4) contain a sufficiently large amount of light element impurities such as C, N and O [15]. Hence, two most probable mechanisms of thermal stability are possible in nTi: (i) grain boundary pinning by precipitates (dispersed particles of carbides, nitrides, etc.…”