Interaction between lattice dislocations and grain boundaries in f.c.c. and ordered compounds: a computer simulation

The interaction of 1/2<110> screw- and 60° dislocations with symmetric [110] tilt boundaries was investigated by atomistic simulations using many-body potentials representing a pure f.c.c. metal and ordered intermetallic compounds. The calculations were performed with and without an applied shear stress. The observations were: absorption into the grain boundary, attraction of a lattice Shockley partial dislocation towards the grain boundary and transmission through the grain boundary under the influence of a shear stress. It was found that the structural unit model may help to predict the interaction mechanism for long period boundaries and that the interaction in ordered compounds shows similarities to the interaction in f.c.c. metals. Some comparisons with experimental observations have been made.

INTERACTION BETWEEN LATTICE DISLOCATIONS AND GRAIN BOUNDARIES IN FCC METALS AND ORDERED COMPOUNDS

This paper describes a computer simulation study of the interaction between lattice dislocations and tilt grain boundaries. The calculations were carried out using a many-body potential for copper and potentials describing a stable Ll2 type of structure. Two interaction mechanisms were observed : absorption into the boundary by splitting into DSC dislocations and splitting into lattice Shockley partial dislocations, one of which was incorporated in the boundary. If the associated step height for the DSC's is small and (one of) the DSC's can glide in the boundary plane, the lattice dislocation dissociates into DSC dislocations in the boundary. Otherwise, another reaction is favourable, like the incorporation of one lattice partial dislocation in the boundary

Interactions between Lattice Dislocations and Grain Boundaries in Ni3Al Investigated by Means of In Situ TEM and Computer Modelling Experiments

The interaction between lattice dislocations and grain boundaries in Ni3Al has been investigated by means of in situ TEM deformation experiments. The interaction between screw dislocations and a coherent twin boundary could be analyzed in detail. The interaction mechanism found experimentally was compared to the results of a computer modelling study. In the computer modelling study, many-body potentials representing Ni3Al were used. The results of the in situ straining indicate that <110> screw dislocations impinging on a Σ = 3 coherent twin boundary that have a Burgers vector that is parallel to the grain boundary plane can be transmitted to the symmetric slip plane in the other grain under influence of an applied stress. A one-to-one comparison with the results of a computer modelling study of exactly the same system in Ni3Al can be made and the experiment agrees with the simulations. Also, observations were made of superlattice intrinsic stacking faults (SISF) that were formed as a result of the interaction between gliding dislocations and the dislocations of a low angle grain boundary (cell wall). The creation of jogs in the line of the gliding dislocation may be the cause of the SISF formation.