Phase diagram of Y-Zr (yttrium-zirconium) system
This chapter provides the phase diagram of Y-Zr (yttrium-zirconium) system.
As can be seen from the phase diagram presented by [Landolt–Börnstein] this system is characterized by a slight tendency of demixing. Nevertheless, Liu et al. [98Liu] succeeded in preparing amorphous alloys using ion mixing and thermal annealing of multilayered films. These films consist of nine alternate layers of Zr and Y. The mixing was performed using 200 keV xenon as irridiating ions. With irridiation at room temperature amorphous alloys were obtained with the stoichiometries: Y35Zr65, Y25Zr75 and Y15Zr85.
By thermal annealing of multilayered films it could be shown that Y25Zr75 became amorphous after 1 h and at about 420–470 K. This amorphous alloy if annealed then at 520 K transforms within 0.5 h into a crystalline phase (Zr-rich, a = 0.462 nm).
The amorphous phase Y75Zr25 – after 0.5 h annealing at 423 K – transforms into a crystalline phase with fcc-II structure (Y-rich, a = 0.494 nm).
A mixture of fcc I and fcc II was obtained by annealing at 523 K for 1 h with Y50Zr50.
The phases fcc I and fcc II are metastable. Liu et al. [98Liu] have shown using thermodynamic considerations that formation of those phases is possible if the interfacial Gibbs free energy is included in the energetic balance.
a, b, c