Identification of Nature of Dislocation Loops Grown as Vacancy Source after Up-Quenching

The dislocation loops grown as vacancy source after up-quenching in 99.9999 % aluminum single crystals with a low dislocation density were examined by synchrotron topography in order to determine the Burgers vector and the nature directly. The specimen crystal was heated to 295°C and hold for 15min. at the temperature, then cooled down to room temperature to freeze the loops in the specimen. Topographs were taken on the high-speed X-ray topographic station (BL-15B) at the Photon Factory (KEK-PF). White beam topographs were taken using four of symmetrically equivalent 111 and 220 reflections for the determination of the Burgers vector. Monochromatic section topographs were also taken with 111, 222, 333 and 444 reflections at a wavelength of 0.62Å. The image of the loops was simulated by numerical solution of the Takagi-Taupin equations. Burgers vector of the frozen loops was determined to be a /2 . And comparison between the observed loop image and the simulated one showed that the dislocation loop grown as a vacancy source was interstitial-type and the size ranged from 3 µ m to 10 µ m in radius.