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Development of precipitation-strengthened aluminum alloys and manufacturing processes for next generation automotive powertrains

University of British Columbia

The cumulative global emissions produced by the automotive industry over the last decade have put significant strain on the environment. Consequently, automotive engineers and manufacturers have made tremendous efforts toward increasing the efficiencies of automobiles. Several methods exist for improving efficiencies, but this is typically accomplished by either weight reduction, through use of lightweight materials, or increasing the internal operating pressure and, therefore, the temperature of the combustion engine. Unfortunately, the currently-used lightweight alloys have a high tendency to weaken with increasing temperatures, limiting the alloys’ practical use to applications that operate under 200-250 °C (i.e., the current operating temperature of engines). Consequently, this prevents the transportation industry from increasing the efficiencies of engines and reducing greenhouse gas (GHG) emissions. Thus, it is necessary to investigate new methods of improving the elevated temperature strength and thermal stability of lightweight alloys. Preliminary research on the effects of rare earth element (RE) additions, such as cerium or lanthanum, to aluminum (Al) alloys, has shown tremendous progress toward improving the elevated temperature performance of the alloys. REs are considered a byproduct when mining for more valuable minerals such as scandium or yttrium. Fortunately, contrary to their name, REs are widely abundant, economical feasible, and produce thermally stable compounds in Al alloys. However, due to the lack of published literature on the high temperature properties of Al-RE alloys, a commercially viable option is still unavailable. This research aims to develop a new Al-RE alloy, focused on improving the performance at engine operating conditions. The findings from this research suggest that a 3.5 wt.% RE addition to an A356 alloy can improve the alloy’s strength by 130-175% at 250-300 °C. Further, as compared to one of the most used alloys for engine block production, T7 A319, the new A356RE alloy demonstrated improved strength (i.e., 65-118% higher YS) and creep resistance at 250 and 300 °C. This increase in elevated temperature properties may provide the transportation industry with a potential replacement alloy capable of withstanding the increase in thermo-mechanical loading that is necessary for improving vehicle efficiency and, thereby, improving the sustainability of the global environment.

Text

2021-04-20

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/77841

Mechanical Engineering

University of British Columbia

UBCO

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