The Avengers #66

"Betrayal!"

The Avengers (joined by their long-absent members Iron Man and Thor) are invited to attempt to destroy a cylinder of Adamantium created by scientist Myron MacLain aboard S.H.I.E.L.D.'s helicarrier. While discussing the potential use of the metal, the Vision soon finds his mind being taken over and he disappears.  Shortly afterward, as the Avengers return home, Iron Man is suddenly trapped in the training room, and while the other Avengers are occupied getting him out, the Vision travels to the helicarrier and steals the cylinder of Adamantium.

When the Avengers find out they begin to speculate why Vision would betray them, just as the Vision returns and attacks the Wasp. The Avengers gang up and attack the Vision, until the Vision tells them that, for reasons beyond his control, he'd used the Adamantium to rebuild his creator: Ultron.

• 1st metion of Adamantium