Survey of grain boundary migration and thermal behavior in Ni at low homologous temperatures

Abstract

In this study, we report the migration and thermal behavior of 388 Ni grain boundaries that were surveyed by atomistic simulations using a recently proposed ramped synthetic driving force method. With this approach, the critical driving force required to initiate the grain boundary motion rather than the grain boundary mobility was extracted to evaluate the ability of a specific grain boundary to move. It was found that this method was capable of capturing the migration and thermal behavior of almost all of the 388 Ni grain boundaries regardless of their type at low homologous temperatures, e.g., 100−600K (or ∼ 0.06–0.35 the melting point of Ni), which was not possible by using previous atomistic methods. Rich and complex thermal behaviors were found in this temperature regime, many of which were reported for the first time, for example, in grain boundaries that are typically considered to be immobile such as the well-known coherent twin boundary. Furthermore, strong structure-property relationship was found in the tilt and twist boundaries whose migration and thermal behavior was correlated to their tilt/twist axis and angle. In particular, non-thermally activated behavior was commonly observed in most surveyed tilt and twist Ni grain boundaries in this study when the tilt/twist angle was relatively small.