Effects of misorientation and inclination on mechanical response of 〈1 1 0〉 tilt grain boundaries in α-Fe to external stresses

Due to the industrial importance of α-iron-based polycrystalline materials, their grain boundary (GB) structures and properties need to be well characterized and understood in order to optimize the materials through effective GB engineering. In this study, a molecular dynamics (MD) simulation study was performed to investigate a series of 〈1 1 0〉 symmetric tilt grain boundaries (STGBs) and asymmetric tilt grain boundaries (ATGBs) in α-iron. It is shown that the GB energy is proportional to the GB volumetric expansion. During uniaxial deformation, 〈1 1 1〉{1 1 2} twinning appears to be more competitive or easier than 〈1 1 1〉{1 1 2} dislocation emission from the GB at yielding. For bicrystal systems containing STGBs the yield strength obeys the Schmid law, while for ATGB bicrystal systems the yield strengths are mainly determined by the local stress rather than overall stress and average GB energy. The higher degree of atomic disordering in the ATGB regions generates larger local stress fluctuation and thus facilitates local defect emission when subjected to external stresses. (paper)