Influence of Interstitial Impurities (H, B, C) on Grain Boundary Cohesion in B2 Ti-based Alloys

Abstract

The investigation of hydrogen, boron and carbon sorption properties at the Σ5(310) symmetrical tilt grain boundary (GB) and (310) free surface (FS) in B2 Ti-based alloys was carried out by the plane-wave pseudopotential method within density functional theory. The most preferential positions for interstitial impurities at GB were determined. It was shown that impurities sorption energies at GB depend strongly on their local environment. The analysis of electronic properties allows us to establish the microscopic na-ture of chemical bonding of all considered impurities at GB. It was shown that H decreases more signifi-cantly the surface energies than the GB energy in contrast to B and C. This results in decreasing the Grif-fith work that indicates also the decrease of the strength of grain boundary. The segregation of H at the GB makes intergranular fracture much easier because the bonding between metal atoms, which are neigh-bors of H, is weakened. The segregation behavior of hydrogen confirms it as an embrittler for B2 Ti-based alloys. At the same time boron and carbon segregation contrast to hydrogen increase the GB cohesion. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35519