Ordering process of Cu3Pt from short-range order state studied by in-situ TEM observation
✍ Scribed by N Chiwata; T Sakai; A Matsumoto; N Kuwano; K Oki
- Publisher
- Elsevier Science
- Year
- 2000
- Tongue
- English
- Weight
- 868 KB
- Volume
- 31
- Category
- Article
- ISSN
- 0968-4328
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✦ Synopsis
The state of short-range order (SRO) and the ordering process in Cu 3 Pt have been studied by the in-situ transmission electron microscope observation method. In order to detect weak diffraction-patterns and weak image-contrasts, an imaging plate system and/or digital-process of video-recorded signals were applied. It is confirmed that above the critical temperature for ordering, T c , the alloy shows diffuse scattering in its electron diffraction pattern. The appearance of the diffuse scattering indicates that the "disordered" Cu 3 Pt (designated as A1) has an SROstate in thermoequilibrium. Dark field images taken by using the diffuse scattering shows a fine dot-contrast, which indicates the presence of "microdomains". The dot-contrast is flickering at higher temperatures, but the rate of flickering decreases with falling temperature and finally stops before reaching T c . On further decreasing temperature, some of the microdomains grow up to large domains of the long period superstructure (L1 2-s ) phase. This indicates that the transformation to L1 2-s via SRO proceeds without a process of nucleation even though the transformation is of a first-order.