Phase Stability of Crystalline and Amorphous Phases and Formation of Nanostructure in Zr-Pd and Zr-Pt Alloys Under Elect
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1048-Z08-03
Phase Stability of Crystalline and Amorphous Phases and Formation of Nanostructure in Zr-Pd and Zr-Pt Alloys Under Electron Irradiation Yukichi Umakoshi, Takeshi Nagase, and Takashi Hosokawa Division of Materials and Manufacturing Science, Graduate School of Engineering, Osaka University, 2-1, Yamada-oka, Suita, 565-0871, Japan ABSTRACT Electron irradiation induced phase transition behavior of Zr-Pd and Zr-Pt alloys was investigated focusing on phase selection in crystallization by thermal annealing and electron irradiation. Nano quasi-crystalline (QC) phase was formed by thermal crystallization in Zr66.7Pd33.3 and Zr80Pt20 alloys, while nano two-type f.c.c. super-saturated solid solutions were formed by irradiation induced crystallization at 298K. In Zr66.7Pt33.3 alloy, polycrystalline Zr5Pt3 and Zr9Pt11 phases transformed to two-type f.c.c. nano-crystalline phase through an amorphous state by crystal-to-amorphous-to-crystal (C-A-C) transition during electron irradiation. Nano-composite phase composed of f.c.c. super-saturated solid solution and residual amorphous phase was formed by electron irradiation induced phase transition. INTRODUCTION Electron irradiation technique is well known to introduce the simplest type lattice defect in crystalline phase and results in the crystal-to-amorphous (C-A) transition in intermetallic compounds [1-4]. Electron irradiation induced solid-state amorphization behavior in Zr-based alloy systems was summarized in the previous paper [5]. In contrast, electron irradiation can introduce free volume in metallic glass, resulting in the occurrence of amorphous-to-crystal (A-C) in some metallic glasses. Electron irradiation induced crystallization of an amorphous phase in Zr-based alloys has been systematically investigated and the following features are revealed: (1) nano-crystallization, (2) suppression of coarsening of nano-crystalline precipitates, (3) different phase selection between electron irradiation and thermal annealing, and (4) anomaly of phase selection in electron irradiation induced nano-crystallization in quasi-crystal (QC) former type alloys [5,6]. Focusing on the above described feature (4) about the phase selection in the crystallization, the formation of two-type f.c.c. supersaturated solid solutions was confirmed through electron irradiation induced crystallization at 298K only in Zr-Pd alloy [7-9]. In the present study, electron irradiation induced crystallization of an amorphous phase in Zr80Pt20 and C-A-C transition in Zr66.7Pt33.3 alloy was investigated to confirm the anomaly in phase selection of the irradiation induced crystallization in Zr-based QC-former alloys.
EXPERIMENT Master ingots of Zr80Pt20 and Zr66.7Pt33.3 (at.%) alloys were prepared by arc melting in purified Ar atmosphere. Rapidly quenched ribbon was produced from the ingots at a rotation speed of 42 ms-1 by a single roller melt-spinning method in this atmosphere. Thermal properties and crystallization behavior of the melt-spun ribbon were examined by differential scanning calorimet
