Insights into factors that affect non-Arrhenius migration of a simulated incoherent S3 grain boundary

A Verma and OK Johnson and GB Thompson and I Chesser and S Ogata and ER Homer, ACTA MATERIALIA, 258, 119210 (2023).

DOI: 10.1016/j.actamat.2023.119210

Non-Arrhenius grain boundary migration, sometimes referred to as antithermal migration where temperature and GB velocity values are inversely related to each other, is examined in an incoherent twin & sigma;3 111 60 degrees (11 8 5) nickel grain boundary. Molecular dynamics is used to simulate migration and examine the effect of various factors on the migration, including interatomic potential, system size, driving force, and variation of atomic grain boundary structure. A classical model for grain boundary migration, in its unsimplified form, is used to analyze the results. The grain boundaries exhibit migration mechanisms with very low apparent barrier heights to migration. As a result, the boundaries migrate quickly but exhibit a velocity saturation similar to that of dislocations. The various interatomic potentials exhibit different migration velocities, but their similarities suggest they all predict similar overall behaviors of migration. The variation of atomic structure in the same incoherent twin grain boundary leads to diverse behaviors with barrier heights that vary from non-Arrhenius to Arrhenius migration. Facet nucleation is confirmed not to be a requirement for this boundary based on an examination of simulation cell size; however, the presence and/or interaction between numerous facets does suggest a slowing and increased barrier height to migration for larger boundaries.

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