Regular aluminum pistol frames are actually some form of "duralumin", which is an alloy of aluminum with a little copper (and maybe other metals, I'm not an expert).
"Scandium" frames are an alloy of aluminum with a little scandium (and once again, probably other stuff). Scandium is a fairly rare atomic element, and I guess the only places where it is found in any quantity used to be behind the Iron Curtain. Once Communism collapsed, the price of scandium in the West went down to the point where it could be used in firearms.
The scandium-aluminum alloy is superior to the copper-aluminum alloy, to the point where scandium can be used for the cylinder of the revolver, which was never practical with duralumin. (They might still use steel chamber inserts in the scandium guns; I don't have one.) But as far as I know, that's why the scandium guns are so much lighter than the older "aluminum" guns, which had steel cylinders.
Apparently scandium-aluminum guns don't resist flame-cutting any better than the duralumin guns.
BTW, if you want to save some typing, it used to be common to abbreviate duralumin as "dural". Dural was the primary material of most WWII airplanes, and it was improved so much during the war that it became possible to make firearms and many other things (like lawn furniture) out of it.