EFFECT OF TOOL ECCENTRICITY ON THE MICROSTRUCTURAL AND MECHANICAL PROPERTY OF FRICTION STIR WELDED ALUMINUM ALLOYS

This paper investigates the effect of tool eccentricity on the material fl ow and mechanical properties of friction stir welded (FSWed) AA5083 and AA6061 aluminum alloy. Samples were butt joined parallel to rolling direction, using a threaded and tapered tool with 3 fl ats, which was mounted with and without intentional eccentricity (or misalignment). The travel speed and tool rotation speed were 63 mm/min and 1120 rpm, respectively. The weld microstructure was characterized using optical microscopy and scanning electron microscopy. Mechanical property was measured using Vickers hardness indentation and tensile testing. Microstructural observations show that tool eccentricity enhances the material fl ow in the nugget zone for both aluminum alloys. The hardness of the AA6061 sample indicates softening at the lower end of the joint due to tool eccentricity, but AA5083 samples exhibited a negligible difference between an aligned versus eccentric tool. Tensile tests for both material show similar tensile strength and behavior for both types of alloy. It can be concluded that tool eccentricity enhances the material fl ow of the nugget zone and promote further softening of heat-treatable aluminum alloys, but show negligible impact on the overall mechanical property.