Dissimilar friction stir welding of Ti-6Al-4V alloy and aluminum alloy employing a modified butt joint configuration: Influences of process variables on the weld interfaces and tensile properties

Friction stir welding (FSW) technique is considered to offer advantages over fusion welding in terms of dissimilar jointing. However, some challenges still exist in the butt FSW of dissimilar Ti and Al metals. The present research employed a modified butt joint configuration into the FSW of Ti-6Al-4V alloy to Al-6Mg alloy with a special pin plunge setup, aiming to obtain a high-quality Ti-to-Al joint, avoid butt flaw or Al melting, and reduce the tool shoulder attrition. Under different FSW process conditions, the examinations and analyses of macro/micro-structures, mechanical tensile properties and fractographies of the dissimilar joints were conducted. The joint mechanical tensile strength can reach more than 92% of the parent Al alloy strength, with a tensile fracture path within the Al alloy butt side. The characteristics and formation mechanisms of the diffusion typed and reaction typed Ti-Al butt-welded interface structures were detailed. The bulky intermetallic compounds (IMC) interlayer at the butt-welded interface had a negative effect on the joint tensile strength, comparing with the Ti-Al diffusion bonding interlayer of similar to 2 mu m in thickness, which was produced via lower tool rotating speed and lower pin-offset value towards Ti alloy butt side. (C) 2013 Elsevier Ltd. All rights reserved.