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To better understand microstructure evolution during thermal mechanical processes, electrical conductivity tests were introduced to evaluate microstructure change in a spray formed ultra-high strength aluminum alloy. The results showed that porosity significantly influenced electrical conductivity in as-deposited state, and dissolution of alloying elements was the main factor for the variation during heat treatments. Microstructure observations revealed that porosity closure led to the increase in electrical conductivity after hot extrusion. The depletion of these atoms from Al matrix through precipitation nucleation, growth and coarsen contributed to the increase in electrical conductivity during aging treatments. Each contribution of microstructure matched well with Matthiessen rule. [ABSTRACT FROM AUTHOR]

The quenching condition of aluminum alloy can affect the mechanical property and corrosion resistance of the profile. This paper is aimed at the low quench sensitivity of aluminum alloys. Scanning electron microscopy and transmission electron microscopy were used to analyze precipitate behaviors of the 7A46 aluminum alloy under different isothermal cooling conditions and microstructure evolutions of quench-induced precipitations. The effect of the different isothermal time on the corrosion resistance of the alloy, and the relationship between microstructure and corrosion resistance after quenching were revealed through electrochemical impedance spectroscopy and potentiodynamic polarization tests. Results show that corrosion sensitivity of the quenching-aged alloy is much higher than that of the double-aged (DA) alloy, and the corrosion resistance of the quenched alloy decreases firstly and then increases. Due to the high density of the matrix precipitates, the increased content of the impurity element, the discontinuity of the grain boundary precipitates and the widening of the precipitates free zone, the most serious degree of corrosion performance among the quenched alloys is 295 °C at 800 s, and the self-corrosion potential and self-current density is −0.919 V and 2.371 μA/cm2, respectively. [ABSTRACT FROM AUTHOR]