Microstructure and texture evolution after twin roll casting and subsequent cold rolling of Al-Mg-Mn aluminium alloys

Twin roll casting is an established route to produce aluminium sheet (10-0.5 mm thick) directly from the melt. Various microdefects (bleeds, centre segregates,...) and inappropriate texture arise during casting which limit the range of operating conditions suitable for use commercially. In this study, the as-cast texture gradient running from a shear texture ([100] < 011 > and [III] < u v w >) in the sub-surface towards a weak beta-fibre in the centre has been investigated. During the first stages of cold rolling, the surface shear components rotate towards stable rolling orientations; meanwhile, hard eutectic-like structures in the centre segregates are not affected by the deformation; only, the surrounding Al-matrix is subjected to a high level of plastic deformation. On the other hand, the surface bleed (where a high density of hard intermetallic has been found) follows the overall behaviour of the Al-matrix. This behaviour is mainly due to the fine primary alpha-Al structure inside the bleed that is able to sustain a large amount of cold deformation (up to 95%) without cracking. (c) 2005 Elsevier B.V. All rights reserved.