Transmission electron microscopy observation of 〈101] superdislocation decomposition in Ti-Al deformed at −196°C

Abstract

A polycrystalline Ti-52at.% Al alloy has been deformed in compression at -196°C and its microstructure has been examined by transmission electron microscopy. The <101] superdislocations were frequently observed to decompose into two inequivalent units with smaller orthogonal Burgers vectors of 1/2 <112] and - <110] respectively. Observation of local decomposition of <101] superdislocation dipoles and dislocation triple nodes formed by the three dislocations are presented. Arguments based on the observation have ruled out the possibilities that several alternative dislocation reactions are responsible for the observation. Possible factors whichMayinfluence the decomposition are discussed. It is concluded that the decomposition could occur in Ti-Al deformed over a wide temperature range if the <101] superdislocation lies in a favourable orientation.