Evolution of Grain Orientation in front of the Pin during FSW of the 6082-T6 Aluminium Alloy

Abstract

Friction stir welding (FSW), a new solid-phase connection method, is considered an excellent welding method for aluminium alloys. Grain orientation, grain boundary structure, and texture types in different regions were characterized by a high-resolution electron backscattered diffraction technology. The results revealed that during the welding process, the coarse grains of the base metal are refined, grains in region 1 (600 μm away from the edge of the keyhole) are arranged in a long strip, and the long axis is approximately parallel to the shear direction. The thermal cycle of the welding process causes some grains to recrystallize, further forming a recrystallization (100) [011] rotating-cube texture. The metal in region 2 (100 μm away from the edge of the keyhole) was severely squeezed by the pin, resulting in an increase in the degree of grain breakage in this region, which were mainly equiaxed grains. Due to the eccentric movement of the pin, the (100) [001]-oriented and (110) [001]-oriented grains alternate on the middle layer, forming a banded structure. Plastic deformation and recrystallization occurred in the base metal, within 383 μm in front of the pin, forming a (110) [001] Goss texture and (100) [001] recrystallized cubic texture.