Effect of grain boundary atomic density and temperature on <110> symmetric tilt grain boundaries in tungsten: An atomistic study

The grain boundaries (GBs) play an important role in absorbing the point defects (interstitials and vacancies) generated by irradiation, and thus have significant effects on the resistance of materials to irradiation damage. In this work, considering the change of GB atomic density caused by absorbing point defects and irradiation temperature, 19 <110> symmetric tilt grain boundaries (STGBs) in tungsten were systematically studied with different GB atomic densities and different temperatures, based on the Molecular Dynamics simulations. The GBE difference caused by the change of GB atomic density, ΔGBE[n], are different for different STGBs. Our calculations show that the STGBs with large ΔGBE[n] are generally poor sinks for interstitials, while those with small ΔGBE[n] are generally strong sinks. The STGBs acting as strong sinks are generally those high-angle and high-GBE GBs. High temperature may lead to the formation of GB complexions containing local close-packed hexagonal (HCP) or face-centered cubic (FCC) structures at some special STGBs, which is not only related to the preferred lattice misorientations, but also associated with the symmetry of STGBs. These GB complexion transitions may reduce the GBEs of these special STGBs. Compared with GB atomic density, high temperature may significantly further promote the formation of local HCP or FCC structures at these special STGBs. Furthermore, a new GB structure analysis method based on the stacking of effective interstices was proposed to assess the absorption capacity of the 19 STGBs to interstitials. It was found that the absorption capacity of GBs to interstitials is negatively related to effective interstice density, while positively correlated with effective interstice size. This effective interstice analysis method offers a new way to assess the absorption capacity of GBs to interstitials, which is valuable in materials designing of irradiation resistance.