FIELD-ION MICROSCOPY OBSERVATIONS AND ATOMISTIC SIMULATIONS OF RIGID-BODY SHIFTS AT TILT GRAIN BOUNDARIES IN TUNGSTEN

Field-ion microscopy and molecular dynamics simulation were used for the characterization of the translation states at special grain boundaries in tungsten. It is revealed that rigid-body displacement had the component of displacement parallel to the [110] direction equal to 0 or 1 interplanar spacing. Full vectors of lateral shifts are described by broad statistical distribution. The mathematical simulation revealed two mirror-symmetry-breaking lateral translations along the $[{\bar{2}21}]$ direction of the Σ9 grain boundary corresponding to different atomic structures. It is shown that the partial disconnection with the $(a/18)[{\bar{2}21}]$ Burgers vector can be considered as the elemental carriers of grain-boundary polymorphic transformation.