Structure of Zr₅₂Ti₅Cu₁₈Ni₁₅Al₁₀ bulk metallic glass at elevated temperatures

The structural behavior of the Zr₅₂Ti₅Cu₁₈Ni₁₅Al₁₀ bulk glass has been investigated in situ by means of high-temperature X-ray synchrotron diffraction. The crystallization starts with the formation of an extremely fine nanostructure followed by the transformation into tetragonal NiZr₂-type crystals plus an unknown phase. Both phases are metastable and transform at about 1123 K into the stable equilibrium phases. The temperature dependence of the scattering curve I (q) of the glass can be well described within the framework of the Debye theory. At the glass transition the first derivative dI (q)/dT changes. A Debye temperature θ = 412 K was estimated for the glassy, and θ = 162 K for the liquid state of the Zr₅₂Ti₅Cu₁₈Ni₁₅Al₁₀ alloy. The short-range order of the glass, of the supercooled liquid state, and of the equilibrium melt at T = 1193 K is found to be quite similar. The results point to the formation of complex chemically ordered clusters already in the melt.