Preferential Growth of Cube-Oriented Grains in Partially Annealed and Additionally Rolled Aluminum Foils for Capacitors

摘要

It is well known that a sharp Cube texture is developed for the producing process of a pure aluminum foil for capacitors. The orientation analysis using scanning electron microscopy/electron backscattered diffraction pattern (SEM/EBSP) method has been performed on the transverse direction (TD) sections of partially annealed (PAed) and additionally rolled (ARed) foils through the thickness in order to reveal how Cube-oriented grains have advantages for growth in comparison with the other grains with orientation components of rolling texture. Samples were annealed repeatedly with increasing the temperature in a vacuum. The Cube grains were distributed throughout foil thickness homogeneously in the PAed and ARed foils. The main mechanism of preferential growth of the Cube grains in the PAed foils was driven by grain boundary energy. However, the growth for ARed foils was caused by strain induced grain boundary migration (SIBM) driven by the difference in stored energy between the Cube and the other grains, because the former store less strain energy than the latter after the additional rolling. Furthermore, the grown-up Cube grains having similar orientations met each other and made a cluster in both the foils. Since the clusters develop to reach the foil surfaces and become stable, the Cube grains are easy to cover all of the foil in the final stage of annealing.