Interfacial defects and lamellar decomposition in titanium aluminides

Abstract

The interfacial defect content of lamellar interfaces in Ti aluminide alloys has been evaluated by HREM and the data analysed using the Topological Theory of Interfacial Defects. It has been found that the defects observed are all perfect interfacial disconnections, and that the lamellar decomposition is diffusion-controlled. An analysis of the diffusive fluxes required for disconnection motion has been used to reconcile the apparent discrepancy between this conclusion and the martensitic crystallography exhibited by the TiAl lamellae. Moreover, this analysis has been used to explain why disconnections with Burgers vectors b = 1/3(211) have been observed in these interfaces.