Grant: Alliance Grants

Rare earth elements (REE), i.e. scandium (Sc) and cerium (Ce) to lutetium (Lu), and aluminum (Al) are defined by Canada as critical minerals. Ce and other secondary rare earth elements (REEs) are by-products of extraction, with few large-scale applications. Canada has potentially 15 million tonnes of rare earth oxides in the ground including Sc, which if extracted leaves about half as unusable and effectively increases the cost of the other valuable REE's. Al, unlike REEs, is not mined domestically, and our expertise is in primary production. Al is a low-density material with excellent electrical properties making it ideal for structural and electrical applications. Al has strong recycling attributes with up to 10 times reduction in CO2 production per kg metal compared to primary smelting. Adding <0.5 wt.% Sc enhances the mechanical and corrosion properties of high technology aluminum alloys, but at $10K/kg, Sc's cost limits its use, driving interest in find a cheaper replacement from the secondary REEs. Al alloys containing ~10% Ce are more castable, but higher density Ce limits light-weight applications. Adding Ce to wrought sheet Al alloys made by the direct chill (DC) process route develops large Ce particles that reduce mechanical properties. In contrast, <1wt.% of Ce reduces corrosion and improves electrical conductivity by removing impurity elements from solid solution such as iron (Fe), and modifies the crystalline texture to make Al more receptive to etch pitting important for battery electrodes. Fe pick-up in Al recycling is a major issue and, so, what is currently waste Ce has potential to extend use in electrical applications. An alternative and more energy efficient process to the DC cast route is thin strip casting where faster cooling rates can prevent large intermetallics forming in Al-REE alloys which will increase strength, conductivity and corrosion resistance. Partnering with Ucore Rare Metals, Kingston Process Metallurgy, CastTechnology and CanmetMATERIALS, researchers at Queen's will investigate the feasibility to develop a domestic circular economy using secondary REEs with aluminum alloys for advanced automotive, aerospace and energy storage applications.