High-resolution electron microscopy study of γ-γTtwin interfaces in the lamellar structure of TiAl-based alloys

Abstract

Abstract The so-called TiAl/Ti3Al lamellar structure has been studied in a two-phase TiAl-based alloy by using high-resolution transmission electron microscopy, in order to verify the existence of various mixed boundaries (MBs) in the γ-phase of the lamellar structure. In this investigation, particular attention was paid to the atomic structure of {111} twin boundaries (TBs) γ-γT. Although only a few cases allowed us to examine this kind of interface, the existence of mixed twin boundaries could be confirmed under particular conditions of specimen orientation. This result strongly suggests that the other boundaries, namely order-domain boundaries (ODBs) and pseudo-twin boundaries (PTBs), can also exist in the mixed form. All these MBs can be formed through two distinct mechanisms: firstly the coupling of rather mobile antiphase boundaries with the other less mobile boundaries such as ODBs, TBs and PTBs which are primarily introduced in the lamellar structure and secondly the meeting of two separately nucl...