Joining of dissimilar materials with friction stir welding

Abstract

The welding and joining of dissimilar metals which have very different properties, such as aluminium and carbon steel, is considered to be a subject for research and development in the welding/joining sector continuing into the 21st century. There are also huge requirements and expectations for this sector.¹ Due to the aforementioned, the research and development of welding and joining of dissimilar materials have been carried out over many years; for instance, eutectic bonding of copper pipe and aluminium pipe was developed 30 years ago and this process is still applied for the heat pipes of refrigerators. Recently it has even progressed for applications in joining of wide plate materials of aluminium alloy and stainless steel by means of the vacuum rolling process² and also for weldments of aluminium alloy and carbon steel joined by means of friction welding and employed as automobile components.³ However, there are problems from aspects of cost and restrictions concerning the configurations for which joining is feasible using conventional welding and joining processes and these techniques have not yet reached the stage where they can be applied in a number of industrial sectors. Accordingly, an extensive programme of research and development has been deployed in recent years using fusion welding processes, such as electron beam and laser welding and brazing, diffusion bonding and also friction stir welding (FSW).⁴