Direct observation of orientation change by channel die compression of polycrystalline aluminum—Use of a split sample

Abstract

The orientation changes of a set of grains in a 2 × 2 mm region on an “internal” surface of a two-part polycrystalline aluminum sample were measured by the Backscattered Kikuchi Diffraction (BKD) technique before and after 40% height reduction in a channel die. Bulk textures determined by both BKD and X-ray diffraction showed moderate agreement with predictions from a rate dependent, Taylor like, polycrystal model. However, the predicted local orientation changes agreed with the experiments for only a few of the 58 grains studied. In most cases, the average orientation change was different in magnitude and direction from this prediction. The observations also showed large in-grain misorientations sometimes as large as 25°, while the model assumes a single orientation for each grain. Although the orientations of many grains were along the rolling texture fiber after deformation, they were not at the positions predicted by the model. Thus homogeneous uniform strain, a common assumption in deformation texture models cannot be used to predict structural changes at grain level.