Atomistic simulation of Σ3 (111) grain boundary fracture in tungsten containing various impurities

The effect of various impurities and micro-alloying additions (B, N, C, O, Al, Si, S and P) on the intrinsic resistance of the Sigma 3 (111) grain boundary in tungsten has been investigated using the molecular dynamics simulation. The atomic interactions have been accounted for through the use of Finnis-Sinclair interatomic potentials. The fracture resistance of the grain boundary has been characterized by computing, in each case, the ideal work of grain boundary separation, the mode I stress intensity factor and the Eshelby's F-1 conservation integral at the onset of crack propagation. The results obtained suggest that pure tungsten is relatively resistant to grain boundary decohesion and that this resistance is further enhanced by the presence of B, C and N. Elements such as O, Al and Si however, have a relatively minor effect on the cohesion strength of the Sigma 3(111) grain boundary. In sharp contrast, S and P greatly reduce this strength making tungsten quite brittle. These findings have been correlated with the effect of the impurity atoms on material evolution at the crack tip. (C) 1997 Elsevier Science Ltd.