Heating aging behavior of Al–8.35Zn–2.5Mg–2.25Cu alloy

Abstract In the present work, the influence of heating aging treatment (HAT) on the microstructure and mechanical properties of Al–Zn–Mg–Cu alloy was investigated. When the final aging temperature (FAT) was lower than 180 °C, the hardness increased with the decreasing of heating rate, however, in the case of the FAT was higher than 180 °C, the variation of hardness was opposite. The electrical conductivity of Al–Zn–Mg–Cu alloy increased with the decrease of heating rate regardless of FAT. The tensile strength, yield strength and conductivity of the Al alloy after (100–180 °C, 20 °C/h) HAT increased by 1.6%, 4.5% and 14.1% than that after T6 treatment, respectively. The precipitates sequence of HAT was coincident with that of isothermal aging, which is SSS → GP zone →  η ′ →  η . With the increase of FAT and the decrease of heating rate, the fine precipitates became larger and the continuous η phase at grain boundary grew to be individual large precipitates. The HAT time was decreased about 80% than that for T6 treatment, indicating HAT could improve the mechanical properties, corrosion resistance and production efficiency with less energy consumption.