A molecular dynamics study of the effect of helium clusters on grain boundary migration in bcc iron

AT Wicaksono and M Militzer and CW Sinclair, PHILOSOPHICAL MAGAZINE, 96, 3746-3774 (2016).

DOI: 10.1080/14786435.2016.1240376

The kinetic interplay between helium (He) segregation, He cluster formation and curvature-driven grain boundary migration in bcc iron (alpha-Fe) has been investigated using molecular dynamics simulations. He atoms that segregate to the migrating boundary are found to be trapped in vacant substitutional sites emitted by the migrating boundary. He atoms that form clusters in the bulk restrain the boundary migration via a pinning mechanism. The pinning pressure of He clusters is proportional to the density and the squared radius of each cluster. A cluster pinning model has been developed by taking into account the two- fold effect of clusters on the boundary migration: (1) reducing the boundary mobility and (2) acting as pinning objects that delay or even completely halt the boundary migration. The model is found to be in agreement with the simulation results.

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