Scandium (Sc) is an element which when added to Aluminum creates a strong, lightweight alloy with excellent resistance to corrosion and good weldability. These alloy properties can be achieved with Scandium additions in the range of 0.1% to 1.0% by weight. Sc-Al alloys were originally developed for aerospace applications and have also been used to manufacture high-performance sports equipment, including baseball bats, bicycle frames and lacrosse sticks. More recently, scandium has been used as a key component in advanced solid oxide fuel cells that generate reliable electrical power with virtually no pollution. Wider adoption of Scandium materials in the aerospace, shipbuilding and transportation sectors has been limited by the lack of a reliable supply of primary scandium products.
Latent demand for Scandium in the aerospace industry alone has been estimated to exceed several hundred tonnes per year by OnG Commodities LLC, an independent scandium market research firm. OnG estimates that the use of Scandium by commercial airline manufacturers can help those companies potentially achieve hundreds of millions of dollars annually in savings. OnG's estimates of these benefits can be seen here.
How does Scandium deliver these potential benefits to commercial avation? The following are a few of the qualities it imparts to aluminum alloys:
- Greater strength: Aluminum-scandium (AlSc) alloys can be 10-100% stronger than conventional aluminum alloys, allowing more performance with less material, and hence with reduced weight and greater fuel savings.
- Improved welding: It is hard to control the strength of aluminum in the region of welds because the metal tends to form very large grains after welding is completed, and large grains can lead to brittleness. This is why aluminum aircraft are riveted rather than welded. Scandium transforms the weld-ability of aluminum alloys by virtue of its grain-refining properties. With AlSc alloys, airframe manufacturers can eliminate the assembly time, cost, and weight of rivets in aircraft.
- Better corrosion resistance: In saline environments aluminum is prone to higher rates of corrosion. Scandium imparts to AlSc alloys much greater resistance to salt water corrosion.
- Superplasticity: The very fine grain size of AlSc alloys permits these alloys to survive very high degrees of strain (bending), a characteristic called superplasticity. For environments where bending forces are common and failure would be catastrophic (e.g., commercial aviation), this additional characteristic of AlSc alloys is both desirable and, for the frequent traveler, comforting.
- Higher working temperatures: Scandium potentially enables aluminum to be used in applications requiring higher service temperatures. This is due to the influence of scandium in creating and maintaining a fine grain structure in the metal. Applications in jet engines – at least in the less extreme environments of the engine -- are a very real future possibility.