Initial crystallization processes of Hf-Cu-M (M=Pd, Pt or Ag) amorphous alloys

Abstract

Hf₇₀Cu₃₀, Hf₇₀Cu₂₀Pd₁₀, Hf₇₀Cu₂₀Pt₁₀, Hf₇₀Cu₂₀Ag₁₀, Hf₇₃Pd₂₇ and Hf₇₃Pt₂₇ amorphous alloys were prepared by a single roller melt-spinning method and the crystallization process was studied by differential scanning calorimetry (DSC), X-ray diffraction and transmission electron microscopy. A single exothermic peak was observed in the DSC curves of Hf₇₀Cu₃₀, Hf₇₀Cu₂₀Ag₁₀ and Hf₇₃Pt₂₇ amorphous alloys, which corresponds to the precipitation of stable crystalline phases. Multiple exothermic peaks were observed in the DSC curves of Hf₇₀Cu₂₀Pd₁₀, Hf₇₀Cu₂₀Pt₁₀ and Hf73Pd27 alloys, of which the low-temperature one corresponds to the precipitation of nanoscale icosahedral quasicrystalline phase (I-phase). The I-phase is in a metastable state since further annealing leads its transformation to other stable crystals. The relation among the atomic configurations of the amorphous alloy, I-phase and stable crystalline phases is discussed.