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I just realised that my frame material is SC7 scandium. What does that term mean? Is it aluminium alloyed with other elements?

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Yes. Scandium is an element with atomic number 21. It is rare with the annual worldwide production being 15-20 tonnes total, so the pure metal commands a price of over $140 USD/gram, and Scandium Oxide is about $5 USD/gram in 2019. All of that is from https://en.wikipedia.org/wiki/Scandium

Your bike frame is not made from scandium. Instead it is an aluminium frame with traces of other additives. SC7 is a specific blend/ratio mix of those additives, to enhance lightness and reduce the downsides of aluminium in a frame.

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    FWIW the benefit of scandium on high strength aluminum alloys is small (e.g. typically 5%). It can improve low strength alloys by 150% but they are still only half as strong as high strength alloys. Beware snake-oil marketing! ("SC7" doesn't look like a standard designation for any alumunim alloy)
    – alephzero
    Aug 31 at 18:19
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    @alephzero I don't say you're wrong, but at least from what I gathered from the Wikipedia article the advantages of adding scandium to aluminium have little to do with strength. Rather, they address two specific problems that are common to most Al-alloys: weak welds, and fatigue failure. It's not implausible that this could lead to significantly better bikes. Aug 31 at 20:13

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