Development of double-side friction stir welding to improve post-welding formability of joints in AA6082 aluminium alloy

An innovative welding methodology, defined as double-side friction stir welding, was developed in order to obtain joints in 2-mm-thick sheets in AA6082 aluminium alloy. Such approach consists in performing the friction stir welding process on both sheet surfaces: the first welding operation is followed by a second one performed by putting the rotating tool in contact with the sheet surface opposite to the one welded by the first pass. The effect of the welding parameters, tool configuration and sheet positioning on the mechanical properties, microstructure and post-welding formability was analysed and discussed in detail. In order to evaluate the advantages offered by the new welding methodology, the experimental results obtained using the double-side friction stir welding were compared with those given by the conventional process.