Maybe not fictional but cool: Titanium (this name!)
quotes from wikipedia
Titanium
"The two most useful properties of the metal form are corrosion resistance and the highest strength-to-weight ratio of any metal. In its unalloyed condition, titanium is as strong as some steels, but 45% lighter."
Hunter process
"The process begins by preparing a mixture of rutile (a mineral consisting of titanium dioxide, TiO2) with chlorine (Cl2) and coke. The coke serves as a source of carbon which reacts with the oxygen (O2) in the TiO2 when extreme heat is applied, producing titanium tetrachloride (TiCl4) and carbon dioxide (CO2).
The titanium tetrachloride is reduced with sodium (Na) to form pure metallic titanium (99.9%) by heating TiCl4 with Na in a steel bomb at 700–800 °C. This final step is the actual Hunter process. It successfully produces very high quality titanium, but it was replaced in all but the most demanding applications by the more economical Kroll process in the 1940s."
So it can be used in alchemy ("corrosion resistance") or as armour ("Due to their high tensile strength to density ratio,[7] high corrosion resistance,[3] fatigue resistance, high crack resistance,[52] and ability to withstand moderately high temperatures without creeping, titanium alloys are used in aircraft, armor plating, naval ships, spacecraft, and missiles.[3][4]").
In general I strongly dislike fictional metals - and real life ones are interesting enough.