Study the effect of welding pass number on the mechanical and metallurgical properties of Aluminum type Al 1050 H14 produced by friction stir welding


Friction Stir Welding (FSW) is a solid state welding technique with nonfusible rotary welds. Heat is generated by the friction produced between the weldtool and the two opposite surfaces of the two welded parts and the tool works onmechanical mixing with the presence of heat, pressure, and heat generated,reaching approximately (80-90%) of the melting point of the metal to be welded.In this study, Al 1050 H14 aluminum with a thickness of (6mm) was used for thepurpose of welding it by means of the friction stir welding process in a buttwelding method to obtain similar welding joints. A set with a square stitching toolMade of alloy steel was used by using a milling machine, with fixed (rotationalspeed of 1008 rpm and linear velocity of 40mm / min), an inclination angle of(2o), and counterclockwise rotation. The efficiency of welded joints wasevaluated through static mechanical tests. Tensile tests, microscopic hardness,and visual examination. The results for all welds showed that the mixing zone(NZ) consists of fine grains of equal axes compared to the base metal. Whenwelding on one side and in one path, the microstructure of HAZ was similar tothe base metal. TAMZ was a transition region between HAZ and NZ. As forwelding on one side, with two paths and three paths, the structure turned into afine crystalline structure. By increasing the number of paths per side, the weldingefficiency of the welded sample increased as the best efficiency was from oneside and three paths (76.215%). Through the results, the tensile strength increaseswith the increase in the number of paths, as the best tensile strength was obtainedwhen conducting the welding process from one side and by three paths, which is(93.653 MPa). It is equivalent to 76.21% of the tensile strength of the base metal.The hardness value in the weld zone (NZ) is higher than the other two zones(HAZ, TMAZ) due to the occurrence of dynamic recrystallization, which resultsin very fine and equiaxial crystals, but the hardness value in the weld zoneremains less than the hardness value of the base metal.