Light-Alloy Melt Ultrasonication: Shorter T6 with Higher Precipitation Strengthening

Abstract

In this paper the influence of ultrasonic melt treatment on the T6 heat-treatment of light alloys is studied. An Al–Zn–Mg–Cu alloy is processed to analyze the artificial ageing in cast samples with non-treated and ultrasonic treated melts. Peak-ageing in samples with acoustic activated melts occurs in shorter time spans (saving 75 min) and higher hardness (up to 22 Hv), relatively to samples with non-treated melts. These changes are attributed to the increase in number of vacancies by the stimulation to form monovacancies rather than divacancies and their homogenized distribution within the alloy matrix by ultrasonic vibration. These effects allow the nucleation of a higher number of solute cluster and GPI zones that will grow into the coarse GPII and fine η′ that characterizes the peak-ageing in these 7xxx series alloys. The reported technique presented as promising route for the reduction of energy consumption in industrial scale heat-treatments.