Nucleation and growth of H blisters in stacking fault on B2–FeAl {100} planes

Abstract

In the present work, the H accumulating behaviors at the stacking fault (SF) on {100} planes in B2–FeAl are studied by first-principles calculations. It is concluded that the SF on B2–FeAl {100} planes can trap H atoms, which serve as nucleation sites for H bubbles. When the areal density (the number of H atoms per the cross-sectional area of the SF) of the trapped H is as high as 5.9 × 10¹⁵ atoms per cm², hydrogen recombines into molecules. With further increasing trapped H atoms, H bubbles grow gradually, yielding a hydrogen pressure of 3.4 GPa and strikingly elongating Al–Al bonds near the SF by 70% which implies the initiation of a crack, and eventually leads to a macroscopic fracture and crack of {100} type observed experimentally with the build-up of high pressures of hydrogen gases. This provides theoretical evidence for a HE mechanism of hydrogen blisters in iron aluminides.