Abstract
The interfacial microstructure produced through tool transit of a friction stir welded lap joint between an aluminium alloy and stainless steel was studied by transmission electron microscopy in order to clarify its early stages of formation. Transmission electron microscopy studies of the bottom surface of the exit hole revealed the presence of several mixed layers of an ultrafine intermetallic compound (IMC) and stainless steel. The joining between dissimilar materials was achieved through a continuous flow of the stirred aluminium alloy into the mixed layers and the resultant growth of the ultrafine IMCs due to the heat induced by the friction between the tool and the specimen. The continuous thin reaction layer finally produced at the interface was found to be stronger than the base aluminium alloy.
Acknowledgements
The author would like to thank Professor K. Ito of Osaka University and Professor T. Shibayanagi of Osaka University (now Toyama University) for their significant help with the TEM observations. A part of this work was performed under the Cooperative Research Program of Institute for Joining and Welding Research Institute, Osaka University. This work was partly supported by a Grant-in-Aid for Young Scientists (B) (grant no. 24760599) from the Japan Society for the Promotion of Science.