Tensile response of (110) twist grain boundaries in tungsten: A molecular dynamics study

Molecular dynamics simulations are performed to investigate the tensile behavior of W bicrystals with different twist grain boundaries (TGBs): the low-angle grain boundary (LAGB), the ordinary high-angle grain boundary (HAGB) and the Sigma 3 TGB. Owing to the initial hexagonal dislocation network (HDN), the LAGB can directly emit dislocations without dislocation nucleation: the 1/2 < 1 1 1 > dislocations in HDN are pinned by bilateral nodes or < 0 0 1 > dislocations and form Frank-Rend dislocation sources, which continually emit dislocations and remain the structure of HDN under tensile loading. Once the HDN become disordered, Frank-Rend dislocation sources are broken and dislocations in HDN can be directly emitted. In the ordinary HAGB and Sigma 3 TGB, dislocations are nucleated from interfaces accompanied with apparent stress decrease at nucleation sites. Supplied with enough stress, emitted dislocations can freely pass through adjacent boundaries. By measuring dislocation densities, we find that the Sigma 3 TGB becomes more active at high temperature and easier to nucleate dislocations, while the LAGB and ordinary HAGB are less affected by temperature. Besides, it is found that 1/2 < 1 1 1 > dislocations play a dominate role in the plastic deformation of W bicrystals regardless of TGB structures and temperature.