Precipitation of icosahedral phase from a supercooled liquid region in Zr₆₅Cu_7.5Al_7.5Ni₁₀Ag₁₀ metallic glass

The formation of an icosahedral phase from the rapidly quenched Zr₆₅Cu_7.5Al_7.5Ni₁₀Ag₁₀ metallic glass was confirmed and the kinetics of the precipitation upon isothermal annealing in the supercooled liquid region were examined by differential scanning calorimetry. Based on the kinetic analysis, it is clarified that the precipitation in the supercooled liquid region takes place by an interfacial controlled growth with a nearly steady-state nucleation rate. The Arrhenius plot between effective time lag, τ, of nucleation and isothermal annealing temperature yields a single linear relation, in which the activation energy for nucleation is evaluated to be 366 kJ/mol. It is concluded that the transformation of amorphous to quasicrystal proceeds by a homogeneous nucleation mode, which is different from those of Pd-U-Si and Al-Cu-V quasicrystals arising from an inhomogeneous distribution of quenched-in nuclei.