Friction stir welding of accumulative roll-bonded commercial-purity aluminium AA1050 and aluminium alloy AA6016

Ultrafine-grained sheets of the commercial-purity aluminium AA1050 and the aluminium alloy AA6016 were processed by accumulative roll bonding. As-received, conventionally grained and ultrafine-grained aluminium sheets with an average grain size ranging from 20 mu m to 30 mu m and 200 nm, respectively, were successfully joined by friction stir welding, and the microstructure and the mechanical properties of the welded zone were investigated. Ultrafine-grained materials showed softening in the nugget, although the hardness remained comparable to the as-received, conventionally grained aluminium sheets. (c) 2008 Elsevier B.V. All rights reserved.