PHILOSOPHICAL MAGAZINE LETTERS, 2001, VOL. 81, NO. 4, 259±264 Titanium segregation mechanism in deformed vanadium±titanium alloys M. Varela, B. Fernandez, A. Mun Äoz,T. Leguey , R. P areja and C. Ballesteros y Departamento de FõÂsica, EPS Universidad Carlos III, Avenida de la Universidad 30, 28911 LeganeÂs, Madrid, Spain [Received in Wnal form 14 November 2000 and accepted 17 November 2000] Abstract Deformed V±Ti alloys with 0.3±5 at.% Ti have been characterized by transmission electron microscopy and X-ray diŒraction. A mechanism for Ti segregation during annealing, related to the formation of deformation twins, has been identi®ed. Energy-dispersive X-ray spectroscopy indicates strong local changes in Ti content along the twins. Samples post-deformation annealed at 1473 K show Ti segregation and the formation of Ti-rich precipitates which have been identi®ed using electron microdiŒraction and X-ray spectroscopy. X-ray diŒraction measurements reveal changes in the lattice parameter of the alloys induced by the Ti segregation and the precipitation processes. } 1. Introduction V-based alloys have been identi®ed as high-performance structural materials for fusion power devices. Knowledge and understanding of the defect structure of these alloys are of considerable importance to optimize desired physical properties. The addition of Ti to V alloys is useful for improving the mechanical properties, to increase their creep resistance and to suppress irradiation swelling (Gold and Harrod 1980, Loomis et al. 1992, Matsui et al. 1993, 1996). This improvement in mechanical properties has been associated with the microstructure of defects induced by the Ti atoms. The eŒect of Ti solute on the recovery characteristics of cold-rolled V±Ti alloys has been investigated by positron annihilation spectroscopy (Leguey et al. 1999). The results indicate the formation of certain Ti-rich precipitates during the ®rst recovery stage. These precipitates are very ecient vacancy sinks and they are apparently induced by dislocation climb. Other positron annihilation measurements performed on neutron-irradiated V±Ti alloys at low temperatures show a large dislocation bias for vacancies and solute Ti (Leguey and Pareja 2000). The above results suggest a precipitate nucleation assisted by Ti segregation on dislocations. In this paper, transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy and X-ray diŒraction (XRD) have been used to analyse the defect microstructure in deformed V±Ti alloys and to characterize the Ti segregation pro- cesses. Philosophical Magazine Letters ISSN 0950±0839 print/ISSN 1362±3036 online # 2001 Taylor & Francis Ltd http://www.tandf.co.uk/journals DOI: 10.1080 /0950083001002295 6 yE-mail: balleste@fis.uc3m.es