Studies of accumulative roll bonding of aluminum and stamping of ultra-fine grain specimens of material

摘要

This article presents the results of accumulative roll bonding (ARB) of annealed, technically pure aluminum with a thickness of 1.2 mm. Specimens - tapes with an ultra-fine grained structure and thickness of approx. 1 mm, were obtained through multiple rolling. Specimens were observed after the 8th ARB pass using EBSD (Electron Back-scatter Diffraction Analysis), which made it possible to preliminarily determine grain size to be less than 1 um. Average crystallite size was also assessed using Scherrer's X-ray diffraction method, and it amounted to 180 nm. Next, stamping and redrawing tests were performed on several sets of punches and dies (several draws) in order to obtain a deep drawpiece with a very small diameter (drawpiece similar to capacitor housing). It was observed that, by using the combined methods of accumulative roll bonding and stamping (as well as several redrawing operations), very deep drawpieces can be obtained, with both improved mechanical properties (compared to conventional materials - e.g. annealed, technically pure aluminum) and greater depths than specimens made from annealed material. Specimens collected from tapes after the ARB process had double the yield point and tensile strength compared to specimens cut out fromannealed material. This result is concurrent with the assumptions of the ARB method. Improved mechanical properties should translate to improved operational durability of capacitor housings. Aluminum tapes subjected to ARB also had greater drawability than tapes that were not rolled.