Phase equilibria and oxidation behavior of Ir-rich Ir-Y binary alloys

The phase equilibria and oxidation behavior of Ir-Y binary alloys have been investigated. A phase diagram at the Ir-rich end in the Ir-Y binary system has been proposed on the basis of experimental results. Iridium is found to dissolve little Y in the FCC solid solution. The pure-Ir and Ir-Y binary alloys exhibit severe weight loss upon air-exposure at 1373 K with elapsed time. Protective oxide layers are not formed on the surface of the alloys with Y up to, at least, 20 at.%. The kinetics of the oxidation is controlled by the formation and sublimation of Ir oxides at the surface.