MATERIALS TRANSACTIONS
Online ISSN : 1347-5320
Print ISSN : 1345-9678
ISSN-L : 1345-9678
Isothermal Section of Ga–Ru–Cu Ternary Phase Diagram at 1073 K: Formation of New Ternary Phase, Ga4Ru3Cu, and Its Structural Relation with the GaRu β-Phase
Takanobu HirotoKazuya HondaKazue NishimotoKoichi KitaharaKaoru Kimura
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2018 Volume 59 Issue 4 Pages 575-579

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Abstract

We have investigated the isothermal phase diagram of the Ga–Ru–Cu ternary system at 1073 K by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and transmission electron microscopy to determine whether the stable icosahedral quasicrystal (i-phase) forms, as it does in the similar Al–Ru–Cu system, and new intermetallic phases exist. This is the first systematic investigation of the Ga–Ru–Cu system. No stable i-phase is identified in the Ga–Ru–Cu alloy system. However, we found a new ternary (τ) phase in the Ga–Ru–Cu system, which is characterized as a C-centered orthorhombic lattice with aτ = 11.80 Å, bτ = 6.04 Å, and cτ = 3.07 Å. The (ideal) chemical composition of the τ-phase is Ga50Ru37.5Cu12.5 (Ga4Ru3Cu). This new phase is stable up to 1073 K. Above 1173 K, the τ-phase transforms to the cubic GaRu (β) phase without any secondary phases. Thus, there is an order–disorder transition between the low-temperature τ-phase and the high-temperature cubic β-phase in this temperature range.

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© 2018 The Japan Institute of Metals and Materials
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