For my last smart as* comment, I offer this:
"Scandium is number 21 on the periodic table of elements. It was discovered over 120 years ago but gained importance during the Cold War, when Soviet scientists and engineers began experimenting with it as an aluminum alloying element. They discovered that it allowed them to weld high-strength aluminum alloys they previously could not.
In the bicycle world, Scandium refers to frame tubing made from an aluminum alloy that includes the element Scandium. In most cases, the tubing base is a high-strength, 7000-series aluminum alloy. The addition of Scandium allows the stronger, non-weldable base aluminum alloy to be welded. Previously, these and similar base alloys could only be made into a frame by bonding them together using high-strength adhesives and cast or machined lugs–almost like high-tech tinker toys.
Compared to standard 7000 series aluminum, the addition of scandium gives this new alloy the following added benefits:
• Improved strength
• Better fatigue and failure properties
• Enhanced weld strength
Scandium opens up new opportunities for frame engineers. In the past, aluminum tubing required larger diameter tubes to achieve the strength necessary to support riding. The larger diameter tubes resulted in stiff ride characteristics, which are fine for time trials but less than ideal for century rides. With Scandium tubing, frame engineers are able to use smaller diameter tubes, thinner cross sections, and shaped tubes to tune the ride characteristics of each frame while using less material. This results in comfortable, efficient, and light frames.
Scandium frame tubing also has increased fatigue life and improved failure modes when compared to traditional aluminum frame tubing. These added benefits come as a result of the same complex metallurgical reasons Scandium allows non-weldable alloys to be welded.
This technology and these benefits do not come free and easy. Raw Scandium is not as abundant as many other alloying elements and is difficult to extract from raw ore. Production of Scandium alloys is relatively new and is being done on a much smaller scale than other aluminum alloys. Welding Scandium requires the use of new technologies and different materials than other aluminums. Proper heat treatment is critical to frame strength and integrity, which prohibits many aluminum frame manufacturers from being able to work with Scandium. Most importantly, knowledge of the frame building material and proper design are still vitally necessary."