Metastable phases formed by ion mixing in the Hf-Nb system with a positive heat of formation

Amorphization was achieved in the Hf-Nb system with a positive heat of formation (+6 kJ mol^-1) by room-temperature 200 keV xenon ion mixing of multilayered films. On the basis of thermodynamic calculation, in which the interfacial free energy of multilayered films was specially taken into account, a Gibbs free-energy diagram was constructed and a relevant interpretation to the observed amorphization behaviour was proposed together with the kinetic considerations for the ion irradiation process. Also, two metastable FCC phases of Nb-rich and Hf-rich concentrations with different sizes were obtained by ion mixing.