Open Collections

Pasqualini, Amanda

University of British Columbia

The potential for the secondary recycling of aluminum alloys to bridge the gap between current open loop recycling processes and the closed loop processes necessary to establish a circular economy within the aluminum metallurgy sector was evaluated. Six recycling friendly alloys were experimentally developed and their microstructural properties and age hardening responses were characterized, to quantify the impact of recycled contents on typical commercial alloy behaviours. All alloys were designed to contain estimated typical compositions of aluminum alloys found in scrap yards and were developed using lab-scale casting methods, where 1xxx, 2xxx, 3xxx, 5xxx, 6xxx, and 7xxx series alloys were remelted and cast in an air furnace. Each alloy was comprised of a majority of either AA6111 or AA3003, so these commercial alloys were also cast to serve as baseline comparisons. The alloys were thermomechanically processed via homogenization heat treatments (1 hour at 560/600°C), hot and cold rolling, quenching, and solution treatments (10 minutes at 560°C). The microstructural evolution during each processing stage was characterized using scanning electron microscopy. Particular emphasis was placed on constituent particle formation to evaluate whether the altered recycled content in the alloys impacted the expected intermetallic phases of their AA6111 or AA3003 base alloys. Energy dispersive x-ray spectroscopy was used to characterize the elemental composition of these particles to determine whether anticipated phases appeared. The age hardening responses were quantified and evaluated via Vickers micro-hardness measurements. It was determined that two alloys exhibited similar hardening responses as AA6111, therefore, aging curves were developed for all three alloys. They were artificially aged at 0.1, 0.5, 4, 7, 9, 24, and 30.5 hours, and hardness measurements at each time were converted to strength values. A class-based Preciso Precipitation Strengthening Model was developed for each alloy under the assumption that Mg₅Si₆ was the main strengthening phase. The model prediction and Tabor approximations strongly correlated at longer aging times, while the solution treated hardness agreed with a Power Law found in literature.

Text

2024-07-24

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/88682

Materials Engineering

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/