Ex-situ and in-situ investigations of the microstructural evolution of AA6082 aluminum alloy during heat treatment

The present study investigated the microstructural evolution of AA6082 aluminum alloy using ex-situ and in-situ methods. Microstructural characterization was performed for the individual steps of the heat treatment parameters. To identify the morphology and kinetics of changes in precipitation and grain, the microstructure of the alloy was examined using scanning electron microscopy/electron backscatter diffraction in combination with energy dispersive X-ray spectrometry. Analysis of the microstructural changes revealed coarser β-Mg2Si nucleation and growth activity, but it showed no changes related to grain growth or α-Al(FeMn)Si precipitation activity. Additionally, the formation of rod-shape β' precipitates was evaluated. Higher temperature promoted the growth and increase in length of β' rods and the appearance of β' rods outside of contact with the intermetallic precipitation. The influences of different isothermal holding temperatures on the relative change in signal velocity generated by a laser ultrasonics for metallurgy (LUMet) system were evaluated. The strong correlation between the findings of microstructural analysis and the results derived from ultrasonic measurement confirmed the efficacy of the novel in-situ model test for predicting microstructural changes.