The nucleation and growth of a nano-icosahedral phase from a supercooled liquid region of Zr65Al7.5Ni10Cu7.5M10 (M = Ag or Pd) glasses have been examined by differential scanning calorimetry and transmission electron microscopy. The growth rate of the icosahedral phase is nearly constant at the initial stage and much slower than that of the Zr2Ni phase in the Zr65Al7.5Ni10Cu17.5 metallic glass. The homogeneous nucleation rate has a maximum value of 4.4 × 1020 m-3 s-1 at 695 K in the Zr65Al7.5Ni10Cu7.5Ag10 glass, which is approximately 102 times higher than that for the formation of quasicrystalline phase in the Zr69.5Al7.5Ni11Cu12 glass and 104 times higher than that of the Zr2Ni phase in the Zr65Al7.5Ni10Cu17.5 glass. With increasing Pd content, the nucleation rate of the primary phase increases significantly and the growth rate decreases at the crystallization temperature. Thus, the addition of Ag and Pd is effective for an increase in the number of nucleation sites and the suppression of grain growth, which is the main reason for the formation of icosahedral nanoparticles. The significant increase in the nucleation rate is due to an increase in the number of nucleation sites resulting from the short-range ordering consisting of Zr-(Ag or Pd) strong pairs. It is implied that the strong pair Zr-(Ag or Pd) also contributes to the restraint of the long-range rearrangements of the constitutional elements. The formation of the nano-icosahedral phase suggests that icosahedral short-range order exists in the glassy state in the present alloys.
ASJC Scopus subject areas
- Condensed Matter Physics