Investigation of metallurgical characterization and mechanical properties of double-sided friction stir welding of aluminum 6061 T6 alloy

In the present study, the effect of tool tilt angle was investigated to appraise the metallurgical and mechanical behavior of double-sided friction stir welded joints of AA-6061 T6 alloy of 6 mm thick plates, using scrolled shoulder and frustum tool pin geometry. Two friction stir welded joints, with 0 degrees (Joint J(1)) and 2 degrees (Joint J(2)) tool tilt angles were fabricated using a fixed travel speed of 50 mm/min and tool rotational speed of 800 rpm. The metallurgical studies carried out by the electron backscattered diffraction showed that the incorporation of tool tilt angle resulted in the refinement of grains within the stir zone to a larger extent. The transverse tensile test results revealed that the joint efficiency of the J(2) welded joint improved by 12% as compared to the J(1) joint. The layered tensile specimens extracted from the different regions (first pass, second pass, and overlap region) of the stir zone of both the welded joints showed an appreciable variation in mechanical and metallurgical properties. The V-notch Charpy impact toughness test for J(2) joint showed 16% higher toughness, with the presence of a 55% shear area fraction in the fractured impact specimens, as compared to the 30% for the J(1) joint.