An investigation on friction spot welding in AA6181-T4 alloy

Abstract

Friction spot welding is a new solid state welding process, invented and patented by the GKSS Research Centre GmbH in Germany, suitable for spot joining lightweight low melting point materials such as Al and Mg alloys. The process is performed with an especially designed rotating tool (comprised by a clamping ring, sleeve, and pin) that creates a joint between sheets in overlap configuration by means of frictional heat and mechanical work. The result is a spot welded lap joint with minimal material loss and a flat surface with no keyhole. In this work the application of Friction Spot Welding for spot joining the Al alloy 6181-T4 was investigated. Different rotational speeds (1900 to 2900 rpm) and welding times (2 to 3.4 s) were tested with the objective of finding the best suited ones for producing high quality joints in terms of microstructure and mechanical performance. The mechanical behavior of the joints was investigated by means of shear tensile tests and the final microstructure was assessed using OM and micro hardness measurements. Welds with strength in the order of 6.8 kN were obtained with high reproducibility. The results also showed that geometric elements of the weld play an important role on the fracture mechanisms and hence on the mechanical performance of the joints. In sum, the results revealed the potential of this process for industrial applications. Copyright © (2010) by Associação Brasileira de Metalurgia Materiais e Mineração (ABM).