Interaction of dislocations and interstitial solute in γ-TiAl

Abstract

Interactions between interstitial impurities and dislocations in γ-TiAl have been observed by transmission electron microscopy. Diffraction contrast images showed evidence of the decoration of ordinary dislocations with Burgers vectors b, given by b = ½〈110], present both in subgrain boundaries and isolated in the grain interiors, by small precipitates. Electron-energy-loss spectroscopy indicated that these precipitates are enriched in oxygen with respect to the TiAl matrix and may have formed oxides. Based on the contrast exhibited by these decorated defects in suitable weak-beam images a maximum diameter of about 10 nm has been determined for these precipitates. Furthermore, a model for the nature of the interaction between interstitial solute atoms and dislocations in γ-TiAl has been proposed. The implications of these findings for the mechanical behaviour of γ-TiAl-based alloys have been discussed.