Effect of heating rate during annealing on microstructure and texture evolution of AA8021 aluminum foil

Abstract

The microstructure and texture evolution of AA8021 aluminum foil during annealing at 270 °C with heating rates of 10 °C h-1 and 40 °C h-1 were investigated by the optical microscope (OM), microhardness tester, field emission scanning electron microscope (FE-SEM) and x-ray diffractometer (XRD). The results show that the microhardness of aluminum foil gradually decreases during the heating process, and the microhardness of aluminum foil with the heating rate of 40 °C h-1 is higher than that of 10 °C h-1. After annealing at 270 °C for 16 h, the average grain size of aluminum foil with the heating rate of 10 °C h-1 is 13.0 μm and the maximum grain size does not exceed 35 μm, while the average grain size with the heating rate of 40 °C h-1 is 14.6 μm and its fraction of the grain area of greater than or equal to 40 μm is 2.4%. The slow heating rate is beneficial to grain refinement of AA8021 aluminum foil due to the release of most deformation energy in the low temperature stage during heating, which leads to the decrease of driving force for crystal nuclei growth. Under the two heating rates, the texture components of the material after annealing are basically the same, mainly the recrystallized Cube, R textures and the residual rolling textures.