Detection of point defects upon ion irradiation by means of precipitate coherency Z.C. Li a, * , H. Abe b , N. Sekimura c a Advanced Materials Laboratory, Department of Materials Science and Engineering, Tsinghua University, Beijing 100084, China b Nuclear Professional School, School of Engineering, University of Tokyo, Ibaraki 319-1188, Japan c Department of Quantum Engineering and Systems Science, School of Engineering, University of Tokyo, Tokyo 113-8656, Japan Received 29 August 2005; accepted 28 October 2006 Abstract Transmission electron microscopy has been widely used to investigate the radiation-damage microstructures, but has limitations when observing point defects due to its resolution limit. In the present study, a dilute Cu–Co alloy, which is a typical precipitation-hardened alloy, has been selected to investigate the formation and the mobility of point defects upon ion irradiation, during which the coherent precipitates lose their coherency and exhibit incoherent strain contrast, and the coherency loss can be used to detect the point defects. Ó 2006 Published by Elsevier B.V. PACS: 28.52.Fa 1. Introduction It is well known that ion beams interact with materials introducing change of material properties. This has been attracting attentions from both points of view of its basic understandings and applications. In order to understand the phenomena, great efforts have been performed, however, the process of the interaction and the material property change induced by ion irradiation has not yet been fully understood and still remains as a scientific issue. It is also well known that collision cascade initiated from MeV heavy ion irradiation produces highly concentrated point defects, which can affect the micro-structural evolution [1–6] and, hence, the properties of materials including dimensional stabil- ity, changes in strength, ductility and fracture toughness, etc. According to simple theoretical considerations, the depth of damage is expected to be comparable to the ion projected range. This relationship is nor- mally found in semiconductors and insulators, while in some metals the observed radiation damage extends significantly deeper into the bulk, especially in those with fcc structure. The fact of the deep radi- ation damage of metals was mentioned by Linker et al. [7] and Sood and Dearnaley [8]. As the origin of the deep radiation damage, possible dislocation movement and atom movement mechanisms were proposed [9,10] through the observations of damage 0022-3115/$ - see front matter Ó 2006 Published by Elsevier B.V. doi:10.1016/j.jnucmat.2006.10.025 * Corresponding author. E-mail address: zcli@tsinghua.edu.cn (Z.C. Li). Journal of Nuclear Materials 362 (2007) 87–92 www.elsevier.com/locate/jnucmat