A comprehensive molecular dynamics study of low-angle grain boundary mobility in a pure aluminum system

Molecular dynamics (MD) simulations have been utilized to determine the low-angle grain boundary (LAGB) mobility of [1 1 2] tilt boundaries in pure aluminum. The mobility data were extracted from two different MD techniques as a function of temperature and misorientation. The artificial driving force method (ADF) and the random walk method were analyzed critically and a detailed comparison of the two techniques was conducted. Within numerical uncertainties, both techniques provide the same magnitude of mobility at 300 K for a grain boundary with low misorientation in Al and the two techniques also agree at 700 K for the highest misorientation studied. For other misorientations, however, there are considerable discrepancies between the two techniques and reasons for the differing results are presented. The results indicate that considerable care must be taken in applying the ADF method to the case of low-angle boundaries. The temperature dependence of LAGB mobility is studied and, consistent with previous MD studies, the activation energy is found to be approximately 10 times lower than the experimental observations.