Authors: J C Hou H J Liu Y Q Zhao
Publish Date: 2014/05/11
Volume: 73, Issue: 5-8, Pages: 1073-1079
Abstract
A 6061T6 aluminum alloy was selfreacting friction stir welded by using the specially designed tool with unequal shoulder diameters at a constant welding speed of 150 mm/min to investigate the effect of rotation speed on microstructure and mechanical properties of the joints Excessive flash on the bottom surface of the joint and groove defects on both surfaces of the joint were formed when the lower shoulder diameter was much smaller The suitable shoulder sizes were determined as 16 and 18 mm in lower shoulder diameter and upper shoulder diameter respectively The grain size and the dislocation density in the weld nugget zone WNZ increased with increasing rotation speed The tensile strength of joints first increased with increasing rotating speed and then decreased remarkably as a result of the formation of void defect The joints welded at lower rotation speeds were fractured in the thermal mechanically affected zone TMAZ However the fracture locations of the defectfree joints were changed to the heat affected zone HAZ at higher rotation speeds
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