Investigation of Mechanical Properties of AA7075 Alloys Aged by Various Heat Treatments

Abstract: In this study, annealing (O), artificial aging (T6), retro-regression aging (RRA) and high temperature pre-precipitation (HTPP) heat treatments were applied to AA7075 aluminium alloys. The effects of these treatments on the mechanical properties of AA7075 alloy were investigated. The microstructures of the samples were examined by Optical Microscope (OM), Scanning Electron Microscope (SEM) and Energy Dispersive X-ray (EDX) analysis. Then, X-ray diffraction analysis (XRD) was conducted to identify intermetallics formed in the microstructure of the samples. Tensile and hardness tests were carried out to investigate the mechanical properties. Results showed that secondary phase particles such as Al2Cu, Al2CuMg and MgZn2 are formed in the microstructures. In terms of the mechanical properties, T6 applied samples showed the best results. The HTPP applied alloy which presented optimum ductility behaviour among the other heat-treated samples. Dimples and some cleavage surfaces were observed on the fracture surfaces of the samples. Therefore, it is concluded that a ductile/semi-ductile fracture occurred on the samples.