Atomistic modelling of hydrogen segregation to the Σ9{2 2 1}[1 1 0] symmetric tilt grain boundary in Al

Abstract

The paper establishes a quantitative link between the bulk hydrogen content and the local concentration in the core of the symmetric tilt grain boundary in Al. A detailed map of approximate segregation energies is obtained by combined semi-empirical and ab initio calculations. Even if the density of trap sites and the binding to the core are large, it is shown that segregation alone is not expected to lead to a significant loss of cohesion below 1000 ppm bulk concentration. Other mechanisms should be involved, like H-induced structural changes, to explain the experimentally observed failure of the interfaces at low H concentration. An example of such mechanism is reported.

Keywords:

• ab initio
• brittleness
• grain boundary structure
• hydrogen in metals

Notes

This work is supported by the French Agence Nationale de la Recherche (ANR) under grant (Blanc 1019424). This work was granted access to the HPC resources of CALMIP (CICT Toulouse, France) under the allocation 2013-p0749 and PSMN at the ENS de Lyon. CNRS (INP) is also gratefully acknowledged for additional funding.