In this work, effect of Retrogression and Reaging (RRA) treatment on microstructure, mechanical properties and fatigue properties of 7075-T6 aluminum alloy was investigated. At first forged samples were homogenized at 460°C for 30 min and then T6 treatment was performed on these samples at 120°C for 24 hr. RRA treatment was carried out at various temperatures of 180, 200, 220, 240°C for 5, 10, 20 min. following quenching, T6 temper was performed on all samples. Mechanical properties of all samples were measured. The microstructures of T6 and RRA samples were characterized with optical microscopy and composition of precipitates was found with EDS analysis. Mechanical results showed that hardness and tensile strength increased 13% through RRA at 200°C for 5min with respect to T6. The effect of RRA treatment on Fatigue properties was measured by rotation-bending test with load ratio -1. Fatigue results showed that the RRA treatment can improve the fatigue strength of 7075 alloy. Fractography analysis showed that space between striation lines in RRA samples is less than T6 ones confirming that RRA treatment can improve the fatigue resistance
