Precipitation of nanoscale icosahedral quasicrystalline phase in Hf-Cu-(Rh, Ir) amorphous alloys

¹ Inoue Superliquid Glass Project, ERATO, JST, Sendai 982-0807, Japan
² Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan

Received: 2 May 2001
Accepted: 19 June 2001
Published online: 15 December 2001

Abstract

Hf₇₀Cu₂₅Rh₅ and Hf₇₀Cu₂₅Ir₅ amorphous alloys were prepared by a single roller melt-spinning method and the crystallization processes were studied by X-ray diffraction, differential scanning calorimetry and transmission electron microscopy. For both of the two alloys, the crystallization proceeds through the reactions of AmI-phaseHf₂Cu+α-Hf, where Am and I-phase represent the amorphous and icosahedral quasicrystalline phases, respectively. Under optimum annealing conditions, the particle size of the I-phase is 10−25 and 10−20 nm for Rh- and Ir-containing alloys, respectively. Considering the fact that the crystallization process of Hf₇₀Cu₃₀ amorphous alloy does not accompany the precipitation of an I-phase, the present result demonstrates that the addition of Rh or Ir is significant. It is suggested that icosahedron-like atomic clusters exist in the amorphous state of Hf₇₀Cu₂₅Rh₅ and Hf₇₀Cu₂₅Ir₅ alloys, which serve as the seeds for the precipitation of the I-phase in the initial crystallization process.