The Effect of Tool Geometry on Strength of Friction Stir Welding

In this research, attempt has been made to understand the effect of tool shape on thestrength of aluminum alloy (AA2024-T3). Seven different tool pin profiles (straight cylindrical, threaded cylindrical, tapered cylindrical, threaded taper, triangular, hexagonal and square) with two different shoulder surfaces (flat and concave) that have been used to fabricate the joint. The effect of tool geometry on the strength of welded joints was investigated using different mechanical tests including (tensile, bending and microhardness tests). Also, a nondestructive tests including (visual and liquid penetration tests) were achieved. Microstructural characteristics during friction stir weldingprocess were studied and the welding joints were investigated using optical microscope. The best mechanical properties obtained in this research were observed in the hexagonalpin profile with concave shoulder where the maximum welding efficiencies were (89.4%) and (85.71%) in terms of ultimate tensile strength and bending force respectively. The weakness tensile strength and bending force were found in the straight cylinder pin profile with flatshoulder as compared with the other tool shapes. The hardness values are higher in the weld zone compared to that in base metal. The maximum value of hardness is observed in the nugget zone of welded sample with hexagonal pin and concave shoulder profile. A fine equiaxed grains size is formed along the parent metal grain structure.