ADVANCED MATERIALS & PROCESSES | JULY/AUGUST 2024 19 alloy exceeded those of conventional 6061 while still retaining reasonable ductility. These tensile properties are listed in Table 2. GOING FORWARD This work represents the first steps toward discovering the potential for ShAPE to reach deep into the aluminum scrap stream and upcycle low-value scrap directly into high-value wrought products without adding primary aluminum. One promising application of ShAPE with aluminum scrap is for the building and construction (B&C) industry, where decarbonizing the built environment is a major objective. The ability of ShAPE to extrude post- consumer scrap has the potential to be a game-changing technology in light of tightening government regulations, commitments to corporate sustainability goals, and increasing incentives for reducing embodied energy and lifecycle CO2 emissions[12]. Another advantage for the B&C industry is that most components are finished with surface coatings like anodization, powder coating, or polyvinylidene fluoride (PVDF), which can mitigate the lower corrosion resistance of Twitch-based alloys caused by high Cu and Si contents[13]. ShAPE of post-consumer scrap also offers the potential for reduced product cost since the price of scrap is a fraction of the cost of primary aluminum alloys. With >50% of the global aluminum extrusion market consumed by the B&C industry and the majority of B&C alloys being 6061 and 6063, there is a sizable opportunity for ShAPE of post-consumer scrap to meet performance requirements while simultaneously offering a cheaper and more sustainable alternative[14]. Another application that has the potential for high impact is the automotive industry. As more aluminum is used in vehicles, the amount of scrap being recycled from these vehicles will also increase. This “scrap wave” has the potential to meet up to 80% of the U.S. automotive industry needs for aluminum by 2050, if manufacturing approaches can be identified that can convert near 100% scrap streams to high-performance automotive components[15]. It is expected that vehicles will continue to increase in aluminum content in the future, either to improve fuel efficiency in gas/diesel vehicles or to increase range in electric vehicles. In this application, the requirements for formability, corrosion resistance, and strength can be more stringent than those in the B&C industry. The solution to this challenge is to further diversify scrap sourcing to create compositions that are lower in tramp element content and are more similar to existing alloy specifications. Twitch would continue to be an inexpensive and plentiful scrap source for this application, but the high Si and Cu contents would likely cause issues with formability and corrosion resistance. One solution that industry is exploring is sorting Twitch into wrought and cast fractions. Although sorting is imperfect, an 80 to 90% efficiency yields a composition considerably lower in Si and Cu compared to mixed Twitch. The wrought fraction can be combined with a variety of other scrap streams such as used beverage cans, conductors, building demolition, and cuttings/ trimmings from industrial extrusion and stamping processes. These scrap streams could then be blended to create compositions similar to on-spec alloys for the automotive industry as a replacement with sharply reduced embodied energy and carbon. PNNL will continue to push the envelope for ShAPE of scrap alloys, reaching into sectors such as B&C, automotive, aerospace, marine, electrical transmission, and feedstock for additive manufacturing. The novel ShAPE machinery constructed by Bond Technologies and PNNL’s development of scrap alloys, process know-how, tooling designs, and post-processing techniques are a promising new approach for sustainable metals manufacturing. ~AM&P For more information: Scott Whalen, chief scientist, Pacific Northwest National Laboratory, 902 Battelle Boulevard, Richland, Washington, 509.372.6084, scott.whalen@pnnl.gov, www.pnnl.gov. References 1. U.S. Department of Energy, 2023 DOE Critical Materials List, 2023, www. govinfo.gov/content/pkg/FR-2023-0804/pdf/2023-16611.pdf. 2. T.G. Gutowski, et al., A Global Assessment of Manufacturing: Economic Development, Energy Use, Carbon Emissions, and the Potential for Energy Efficiency and Materials Recycling, Annual Review of Environment and Resources, 38, p 81–106, 2013, doi.org/10. 1146/annurev-environ-041112-110510. 3. Brian Taylor, Hydro Says Circal’s Carbon Footprint is Shrinking, Recycling Today, 2024. www.recyclingtoday.com/ news/hydro-circal-aluminum-recycling- europe-usa-brazil-low-carbon. TABLE 2 — MECHANICAL PROPERTIES OF ShAPE-PROCESSED TWITCH SCRAP COMPARED TO THE ASTM MINIMUM STANDARD FOR COMMON 6000-SERIES ALUMINUM ALLOYS Specimen Yield strength, MPa UTS, MPa Strain at break, % ShAPE-Twitch 284 ± 6 356 ± 4 10.4 ± 0.8 6063-T6 Min. 172 207 8 6061-T6 Min. 241 262 8 6082-T6 Min. 250 295 8 Note: The yield strength was determined with the 0.2% offset method. The error represents the standard deviation of the four specimens tested.
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