Grain boundary motion during high temperature cyclic deformation of high purity aluminium bicrystals

Abstract

During cyclic deformation of polycrystals at elevated temperatures conspicuous microstructural changes, in particular grain boundary motion and grain boundary alignment have been reported for a variety of metallic materials. The current study addressed this issue by investigating in detail the motion of grain boundaries during cyclic deformation of bicrystals of very high purity aluminium. Bicrystals containing different types of grain boundaries were investigated to probe the influence of grain boundary character on their behaviour under cyclic loading. The displacement of the grain boundaries was recorded using optical microscopy without additional preparation. The evolution of microtexture was measured by the electron backscatter diffraction technique (EBSD) using a scanning electron microscope. During cyclic deformation a deformation structure occurred within each grain. The character of deformation structure, in particular the difference in dislocation density on both sides of the grain boundary was found to be responsible for the displacement of the boundaries. A model is proposed to explain the grain boundary motion and the grain boundary alignment during cyclic deformation of aluminium bicrystals. The relevance of these results for grain boundary behaviour in polycrystals is discussed.