Microstructure and mechanical properties of friction stir welded joints in 2219-T6 aluminum alloy

The microstructure, second-phase particles and mechanical properties of the joint during friction stir welding of 2219-T6 were investigated in this paper. Dynamic recrystallised structures in the weld nugget zone (WNZ) were observed. Grain sizes and second-phase particles through the thickness of WNZ were different. The tensile strength, yield strength, elongation and joint efficiency of joints presented a sharp decline after a peak values with increasing rotary speed from 800 rpm to 1300 rpm. Most of the failures presented different dimples in the tensile fracture. The weld metal presented significant plastic deformation and no surface cracks via the face-bend test. The cracks rising from bottom surface expanded along the boundary between the WNZ and TMAZ in the root-bend test. Max bending angle and maximal bending forces (Fbb) of FSW joints reached to 80° and 3.6 KN, respectively. Microhardness measured across the cross-section of joints slightly increased from 900 rpm to 1100 rpm and the microhardness of different weld zones varied significantly.