Originally Posted by mikejo
So scandium makes the welds stronger, as strong as the alloy frame material.
However, isn't it also put in the frame alloy as well? If so, what is the point of being in the frame material and not just in the welds?
Yes, it is. The reason is simple. You do not weld stainless steel with mild steel filler wire, and if you want a homogeneous bike frame, you do not weld a tube with a disimilar filler. This is exactly the reason I am unhappy with Reynolds' approach to 953. They have made that mistake, and it demonstrates they don't know what they're doing.
In the case of Sc alloyed aluminium alloys, you add Sc to the tube to ensure there's no weld-pool dilution of the alloyed filler wire with parent metal, to below the point it has any effect. You don't alloy the tube for the tube's sake, you alloy it for the weld's sake.
Originally Posted by mikejo
Here is what Salsa has on their website:
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.
...also has increased fatigue life and improved failure modes when compared to traditional aluminum frame tubing
And that's just bullshot. It's about as metallurgically sound as the 'welding non-"thermophilic" steels weakens them'.