Role of low and high angle grain boundaries in the deformation mechanism of nanophase Ni: A molecular dynamics simulation study

Abstract

The microstructure of computer generated Ni nanophase samples is studied by means of pair distribution functions, coordination number, atom energetics, and local crystalline order. The results are analyzed in terms of grain size and texture. Two types of samples are considered: those with random crystallographic orientation, representing a sample with mainly high angle grain boundaries, and those originated from the same seeds as before, but with a limited misorientation, representing samples with mainly low angle grain boundaries. The influence of the presence of many low angle grain boundaries on the high load plastic behavior is discussed in terms of a model based on grain-boundary viscosity controlled by a self diffusion mechanism at the disordered interface, which is activated by thermal energy and stress. Low angle samples have a higher activation energy for deformation and a greater pre-exponential factor. In the low angle samples dislocation loops inside the grains are observed during deformation.