Microstructure analysis of 7050 aluminum alloy processed by multistage aging treatments

Abstract

In the current study differential scanning calorimetry (DSC) and transmission Electron Microscopy (TEM) analyzes were performed in order to investigate the bimodal microstructure feature by taking into account both density and morphology of precipitates, which are transformed from the retrogression and reaging (RRA) along with interrupted aging (T6I4) conditions within the 7050 aluminum alloy. Results showed that RRA treatment is conducive to a higher density of fine precipitates distributed homogeneously in the Al matrix, with precipitates essentially being shear-resistant η’ in view of a smaller density of shearable GP zone and incoherent η precipitates present. Conversely, the T6I4-65 treatment generated a smaller density of less fine shear-resistant precipitates, but with a higher density of shearable GP zone and incoherent η precipitates. Thus, the RRA treatment might promote a beneficial effect on correlation between yield strength and ductility owing to higher balance of combination mechanisms between shearable GP zones and shear-resistant η’ precipitates with movement dislocations as opposed to T6I4-65 treatment within the 7050 aluminum alloy. Both RRA and T6I4-65 treatments culminated in a slight decrease in either potential or pitting corrosion in comparison to the T7451 treatment.