Metallurgical characterization of natural aging effects on pre-deformed Al 7075/T651 alloy during retrogression and re-aging heat treatment

In this study, a new heat treatment route was designed, and the effects of pre-deformation on the retrogression and re-aging (RRA) and 17500 h natural aging (NA) heat treatment were investigated.The specimens that were pre-deformed during the RRA heat treatment and the subsequent NA specimens were compared.As a result of the heat treatments, the phase volume ratios in each specimen were calculated and compared with two different methods.Firstly, the distributions of the phases and the geometrical changes of the precipitates were interpreted by scanning electron microscopy (SEM).Elemental ratios in the precipitates were obtained by energy-dispersive X-ray spectrometry (EDS).Particle size, dislocation density, lattice strain, and texture coefficient values were calculated by the X-ray diffraction method (XRD), and their effects on crystallography were examined in detail.As a result of the differential scanning calorimetry (DSC) analysis, it was observed that the transformation temperatures of the phases changed with the heat treatment route.As a result of all analyses, the connections between the hardness values were interpreted.The results showed that the hardness values, dislocation densities, and lattice strain of the pre-deformed RRA + NA specimens were increased compared to the pre-deformed RRA specimens.K e y w o r d s : natural aging, retrogression and re-aging heat treatment, dislocation density, texture coefficient, 7075 aluminum alloys