Features of structure formation processes in AA2024 alloy joints formed by the friction stir welding with bobbin tool

OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 23 No. 2 2021 In turn, this process leads to the outstripping destruction of the joint structure in the tool outlet area. It is possible to reduce the defectiveness of the structure at the end of the joint, presumably, by an increase in the local heat and deformation influence on the material (to increase the fragmentation degree) by reducing the welding speed (12 in Fig. 4, c ). Differences in the stir zone formation at the tool inlet and outlet areas were investigated using optical microscopy (Fig. 5). Boundaries of the stir zone on the advancing side of the joint are more clearly Fig. 5. Structure formation at joint obtained by BFSW: a, b, e, i, g, h, k, l – structure in the stir zone (SZ) and thermomechanically affected zone (TMAZ) of sub-shoulder region ( a, b, e, f ) and central region ( g, h, k, l ) at advancing ( b, f, k, l ) and retreating ( a, e, g, k ) side of the joint; c, d, i, j – schematics of studied structures а b d g h j k e f i l c