Sheet AA2024-T3: a new investigation of microstructure and composition

Sheet AA2024-T3 is probably one of the most studied aluminium alloys in the corrosion field, because, with copper as an alloying addition, it is one of the most corrosion-prone aluminium alloys. This paper reports new findings on the composition and distribution of intermetallic (IM) particles in AA2024-T3 through the examination of over 80 000 compositional domains in nearly 18 000 IM particles. This work was achieved by using an electron microprobe to map out 2 x 2 mm(2) at a step size of 400 nm. This study revealed that the composition of individual particles can vary considerably from 'accepted' compositions. Domains within particles were extensive across the surface. Because such a large area was mapped, it was possible to subdivide this area and to look at the variation of particle statistics from region to region, providing some information on the statistical variation for small electrodes. (C) Copyright 2010 John Wiley & Sons, Ltd.