Type of presentation: Poster

MS-11-P-1776 In situ TEM observation of Crystal-to-Amorphous-to-Crystal (C-A-C) transition in Cr2Ti

Nagase T.1, 2, Anada S.1, Yasuda H.1, Mori H.1
1Research Center for Ultra-High Voltage Electron Microscopy, Osaka University, Japan, 2Division of Materials and Manufacturing Science, Graduate School of Engineering, Osaka University, Japan
t-nagase@uhvem.osaka-u.ac.jp

In situ TEM observation of Crystal-to-Amorphous-to-Crystal (C-A-C) transition in Cr2Ti was reported focusing on the temperature dependence and the crystallization behavior. Figure 1 shows In situ TEM observation of the change in BF images and corresponding SAD patterns of Cr2Ti stimulated by MeV electron irradiation at 103 K (a) and room temperature of 298 K (b) [1]. At 103 K, a crystalline-to-amorphous (C-A) transition occurred under the irradiation (a1→a3), resulting in the formation of an amorphous single phase. Further irradiation, an amorphous-to-crystalline (A-C) transition occurred as the subsequent structural change (a3→a5) and bcc solid solution single phase was formed. This type of amorphization-crystallization phase transition was called a crystalline-to-amorphous-to-crystalline (C-A-C) transition. At 298 K, black dot contrast appeared in BF image after 60 s irradiation (b2). After irradiation for 180 s (b3), nano-granular contrast appeared at the center of the irradiated area, as seen in the BF image, and discontinuous Debye rings began to appear in the SAD pattern. Upon further irradiation, the nano-granular contrast changed to conventional polycrystalline contrast in the BF images due to bcc solid solution formation (b3→b5). Thermal crystallization of a Cr-Ti amorphous phase obtained by C-A transition and the irradiation induced crystallization during C-A-C transition was also investigated for clarifying the origin of C-A-C transition.

[1] S. Anada, T. Nagase, H. Yasuda, H. Mori: J. of Alloys and Compounds, 579, 646-653 (2013).

This work was supported in part by Grants for Excellent Graduate Schools, the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan.

Fig. 1: Figure 1 In situ TEM observations of the change in BF images and SAD patterns in Cr2Ti intermetallic compounds stimulated by MeV electron irradiation at 103 K at a dose rate of 3.7 × 1024 m-2s-1 (a) and at 298 K at a dose rate of 6.7 × 1024 m-2s-1 (b).