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

Abstract

Hf 70Cu 30, Hf 70Cu 20Pd 10, Hf 70Cu 20Pt 10, Hf 70Cu 20Ag 10, Hf 73Pd 27 and Hf 73Pt 27 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 Hf 70Cu 30, Hf 70Cu 20Ag 10 and Hf 73Pt 27 amorphous alloys, which corresponds to the precipitation of stable crystalline phases. Multiple exothermic peaks were observed in the DSC curves of Hf 70Cu 20Pd 10, Hf 70Cu 20Pt 10 and Hf 73Pd 27 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.