Plastic Deformation in Aluminum Columnar Nanograins

Abstract

The effects of grain size and grain boundary misorientation on the deformation behavior of aluminum columnar nanograins under uniaxial tension in the direction parallel or perpendicular to grain boundaries are studied by molecular dynamics simulation. The results suggest that the average flow stress depends on grain size, grain boundary misorientation and directions of applied loading. The optimal grain size corresponding to the highest average flow strength is lower in columnar models than in the equiaxed random orientation models, and columnar models have higher strength. The formation of shear band occurs in the small grain size models (< 10 nm) with high-angle grain boundaries under columnar directional tension, and the deformation progresses from dislocation activities to shear bands formation. The deformed columnar grains were found to present different dislocation slip systems based on their different crystallographic orientation and load conditions. The high-angle grain boundary models subjected to tension in a direction perpendicular to the grain boundaries exhibit significant variations in plastic strain. These results also indicate that grain boundary activities such as migration and sliding increase in intensity with decreasing grain size.