Titanium

Titanium was an element and a strong metal.

The vault of the bank on Centuria was made of titanium. (COMIC: Time of the Cybermen)

The metal used in Vondraxian orbs shared properties with titanium and zinc, but was neither. (PROSE: Trace Memory)

SERVEYOUinc used titanium vault-like doors to protect their most sensitive research at the United System Research Base. (COMIC: ''The Sound of Our Voices)