Fundamental role of Σ3(1¯11) and Σ3(1¯12) grain boundaries in elastic response and slip transfer

The techniques of grain boundary engineering are rapidly gaining significance microstructural design. To understand individual grain boundary characteristics, the influence of grain boundaries on the elastic and plastic deformation behaviors of copper bicrystals with Σ3(1¯11) twin and Σ3(1¯12) grain boundaries were investigated by large scale molecular statics simulation. These grain boundaries were chosen as examples of coherent and incoherent grain boundaries. Nanoindentation tests perpendicular to the grain boundary plane were used to investigate local deformation properties. Our results showed that an incoherent boundary experiences a reduction in elastic resistance due to the increase in excess free volume and structure-dependent local indentation modulus, while a coherent boundary has little effect on the elastic deformation. The propagation of plastic deformation is strongly blocked by the dissociation into a displacement shift complete (DSC) lattice dislocation which explains the superficial absorptive ability of a coherent twin boundary. However, plastic deformation of the Σ3(1¯12) indentation demonstrates easy slip transfer across the interface.