Effect of hydrogen environment on the separation of Fe grain boundaries. (1st April 2016)

• Record Type: Journal Article
• Authors: Wang, Shuai; Martin, May L.; Robertson, Ian M.; Sofronis, Petros
• Is Part Of: Acta materialia. Volume 107(2016)
• Page Start: 279
• Page End: 288
• Publication Date: 2016-04-01
• Subjects: Hydrogen embrittlement -- Intergranular failure -- Iron; Materials -- Periodicals; Materials science -- Periodicals; Materials -- Mechanical properties -- Periodicals; Metallurgy -- Periodicals; Chemistry, Inorganic -- Periodicals; 620.112
• DOI: 10.1016/j.actamat.2016.01.067
• Languages: English
• ISSNs: 1359-6454

Abstract

Abstract: A density-functional theory based empirical potential was used to explore the energies of different types of Fe grain boundaries and free surfaces in thermodynamic equilibrium with a hydrogen environment. The classical model for calculating the ideal work of separation with solute atoms is extended to account for every trapping site. This yields the lowest-energy structures at different hydrogen chemical potentials (or gas pressures). At hydrogen gas pressures lower than 1000 atm, the reduction of the reversible work of separation is less than 33% and it increases to 36% at a gas pressure of 5000 atm. Near the hydride formation limit, 5 × 10 4 atm, the reduction is 44%. Based on the magnitude of these reductions for complete decohesion, and accounting for experimental observations of the microstructure associated with hydrogen-induced intergranular fracture of Fe, it is posited that hydrogen-enhanced plasticity and attendant effects establish the local conditions responsible for the transition in fracture mode from transgranular to intergranular. The conclusion is reached that intergranular failure occurs by a reduction of the cohesive energy but with contributions from structural as well as compositional changes in the grain boundary that are driven by hydrogen-enhanced plasticity processes. Graphical abstract: