The aim of present study is to investigate the effect of precipitation hardening heat treatment at different aging conditions on the mechanical properties and microstructure of similar friction stir welding (FSW) joints ofAA 2024-T3 and AA 7075-T73 aluminum alloys. Friction stir welding was carried out using milling machine with best welding parameters (tool rotation speed 898 rpm, welding speed 45 mm ̸ min and threaded cylindrical pin geometry). Tensile test, microhardness test,microstructure examination,and X-ray radiographic inspection of FSW joints were made.The results indicated that the best aging conditions for similar welded joints of Al2024 and Al 7075 were in sample (natural aging for two week) and sample
(artificial ageing at 120°C for 24 h) respectively. ‏Microhardness in the as-welded samples showed fluctuations across the weld zone and minimum hardnessoccurs in the heat affected zone(HAZ) in both alloys while the hardness after heat treatment at best aging conditions was improved across the whole weldment and increased in stir zone,