The effect of changes in Al-based amorphous phase structure on structure forming upon crystallization

Abstract

The influence of heat treatment and deformation on structural changes of Al-based amorphous alloys in the amorphous state and at early stages of crystallization has been studied using the methods of X-ray diffraction, differential scanning calorimetry and transmission electron microscopy. It is shown that isothermal annealing and multiple cold rolling bring about formation of an inhomogeneous amorphous phase with the areas of different chemical composition. The formation of an inhomogeneous amorphous phase accelerates the process of nanocrystallization of Al-based alloys. The conditions of treatment of the amorphous alloy in the amorphous state affect the size and fraction of nanocrystals forming in the amorphous phase upon subsequent heating. The size of nanocrystals in the case of preliminary deformation is smaller than that upon preliminary isothermal annealing. We discuss the reasons for the formation of nanostructures containing smaller nanocrystals in the case of thermal and deformation treatments before the onset of crystallization.