Electron Irradiation Induced Crystal-to-Amorphous-to-Crystal (C-A-C) Transition in Intermetallic Compounds
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1128-U05-49
Electron Irradiation Induced Crystal-to-Amorphous-to-Crystal (C-A-C) Transition in Intermetallic Compounds
Takeshi Nagase1,2, Kazuya Takizawa2, Akihiro Nino3 and Yukichi Umakoshi4 1 Research Center for Ultra-High Voltage Electron Microscopy, Osaka University, 7-1, Mihogaoka, Ibaraki, Osaka 567-0047, Japan 2 Division of Materials and Manufacturing Science, Graduate School of Engineering, Osaka University, 2-1, Yamada-oka, Suita, Osaka 565-0871, Japan 3 Department of Materials Science and Engineering, Faculty of Engineering and Resource Science, Akita University, Tegatagakuen-machi, Akita, Akita 010-8502, Japan 4 National Institute for Materials Science, 1-2-1, Sengen, Tsukuba, Ibaraki, 305-0047 Japan
ABSTRACT Mechanical atomic displacement in intermetallic compounds can be introduced by various processes such as severe plastic deformation, mechanical milling and electron irradiation, resulting in the crystal-to-amorphous (C-A) transition and amorphous-to-crystal (A-C) transition in some alloy systems. Recently, unique atomic displacement-induced-phase transitions containing both amorphization and crystallization was found: a crystal-to-amorphous-to-crystal (C-A-C) transition under electron irradiation and a cyclic C-A transition during mechanical milling. The features and predicting factors of alloy systems which undergo C-A-C transition under MeV electron irradiation are discussed based upon the analysis of experimental data reported to date in intermetallic compounds irradiated by high voltage electron microscope (HVEM). INTRODUCTION It is well known that some intermetallic compounds show crystal-to-amorphous (C-A) transition by using a mechanical process below the glass transition temperature (Tg). The C-A transition can be induced by various methods such as particle irradiation, severe plastic deformation, mechanical milling, hydrogen-absorption, inter-diffusion between multi-layers and so on. Among many C-A transition processes, electron-irradiation induced solid-state amorphization is an attractive method because in situ observation is available without oxidation, contamination, or change in chemical composition, and with negligible temperature increase during C-A transition [1-5]. Mori et al. reported that an amorphous state was realized in 37 among 70 electron irradiated crystalline alloys [4]. Such systematically experimental research works clearly indicate that electron irradiation is an effective technique for revealing the origin of C-A transition. Recently a unique phase transition containing C-A transition was found in metallic glass former alloys during mechanical milling and electron irradiation techniques: cyclic crystal-
line-amorphous (Cyclic-CA) transformation during mechanical milling [6,7], electron irradiation induced crystal-to-amorphous-to-crystal (C-A-C) transitions [8,9], and electron irradiation induced quasicrystal-to-amorphous-to-crystal (Q-A-C) transition [10]. Figure 1 shows the typical example of C-A-C transition in Nd2Fe14B polycrystalline intermetallic compound unde
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