PRELIMINARY INVESTIGATIONS OF FRICTION STIR WELD JOINTS BETWEEN AN ALUMINIUM BASED METAL MATRIX COMPOSITE AND A MONOLITHIC ALLOY Studio preliminare di giunzioni FSW tra un composito a matrice di alluminio e la corrispondente lega non rinforzata

In this paper, results of preliminary investigations on friction stir welded joints between monolithic AA6061 and AA6061 reinforced with 20% in volume of particulate Al2O3 are described. The present study originates from a co-operation between GKSS Forschungszentrum, the Engineering Faculty of the University of Genoa (Departments of Production Engineering and Naval Architecture), and Fincantieri Genoa. The material has been welded in GKSS research centre, using a NC 5 axis robot. The joints were obtained using the same tool, made of an ultra-hard material, based on TiC carbides dispersed in a nickel martensitic matrix. The joints were instrumented with thermocouples, in order to check that thermal stability had been reached. The welding speed was varied and samples for macro and microstructural analysis, microhardness measurements, bending and tensile tests were provided. Macro and microstructure showed a well defined interface between the two different alloys, where the harder one, the composite, enters the softer one. Microhardness measurements, bending and tensile tests showed were good results.