eng Oriental Scientific Publishing Company Material Science Research India 0973-3469 2025-09-30 22 2 167 174 23682 article Jaime Hinojosa-Torres 1 Diego Sánchez-García 1 Víctor Manuel Castaño-Meneses 2 Department of Engineering, National Autonomous University of Mexico, Mexico State, Mexico Department of Nanotechnology, National Autonomous University of Mexico, Querétaro, Mexico Flat plates of AA 6061 alloy were welded by using friction-stir welding technique. The plates were placed in direct contact to the bench of the tool holder machine and mechanically fixed, with the bench functioning as a cooling substrate. For the friction-stir welding tool, the optimal values of spindle speed and feed rate were 1045 rpm and 18.6 mm/min, respectively. The welded plates were mechanically characterized in terms of Vickers microhardness (HV), ultimate tension strength (UTS), yield point (YP) and elongation to failure (EF). The weld bead showed a decrease in hardness of 33 % approximately. Tension test results of the welded plates showed UTS, YP and EF were reduced to 66, 60 and 33 % in relation to those of the base metal. X-ray diffraction analysis revealed the presence of q (Al2Cu), Q' (Al3Cu2Mg9Si7), β² (Mg5Si6), β¢ (Mg9Si5), aAl and Al phases inside the weld bead, while the base metal showed to contain β² and β¢ precipitates inside the Al-rich matrix. Heat treatment of solid solution and ageing at 433 K by 18 hours increased the weld bead hardness to 110 HV in the welded plates. https://www.materialsciencejournal.org/vol22no2/mechanical-behavior-and-phase-analysis-of-friction-stir-welded-aa-6061-alloy/ Deformation and fracture Friction-stir welding Metastable phases Phase transformation Second phase Weld bead