Abnormal alloying behaviour observed in an immiscible Zr–Nb system

For the immiscible Zr?Nb system characterized by a positive heat of formation (+6?kJ?mol?1), thermodynamic calculation showed that the Gibbs free energy of the properly designed Zr?Nb multilayered films could be elevated to a higher level than that of the corresponding amorphous phase as well as the supersaturated solid solutions. Accordingly, nano-sized Zr?Nb multilayered films were prepared and then irradiated by 200?keV xenon ions. It was found that amorphous phases could be obtained within a composition range 12?92?at% of Nb. Also, two metastable crystalline phases of fcc structures with different lattice parameters were also obtained. Molecular dynamic simulation was carried out, based on a proven realistic Zr?Nb potential, to reveal the atomistic mechanism of the solid-state crystal-to-amorphous transition. A brief discussion on the formation of the two metastable crystalline phases is presented.