Microstructure and Mechanical Properties of Friction Stir Dissimilar Welding of Pure Ti and 6061 Aluminum Alloy

Abstract

Taking the advantage of its low density, high specific strength and strong corrosion resistance, titanium and aluminum alloys have high marine adaptability and can be directly used in various marine engineering equipment that will expose to seawater or directly contact with seawater. The seawater heater has to withstand 90~120°C corrosion in seawater. This unique working condition makes titanium and aluminum alloys are superior materials which can significantly lower the heater construction cost. In this study, the technology of friction stir welding was used to join the dissimilar materials of aluminum alloy 6061 and commercially pure titanium by means of butt joint. High-speed steel stir rod was used for the friction stir welding, and a 2o title was applied to the stir rod during friction stir welding. To discuss the influence of different rotating speeds and travel speed, the specimens were analyzed for their microstructure, mechanical properties, and elemental analysis was carried out followed by the friction stir welding. Experimental results showed that the best mechanical properties of the butt joint can be obtained by setting the rotational speed of 1000 rpm and the travel speed of 100 mm/min. After welding, grain refinement can be observed in the stirring zone. However, the grains in the heat-affected zone had become larger, and there had a tendency of hardness decreasing, causing failure in this area during tensile testing.