Hot-deformation-induced α2/γ interfacial structure in a two-phase γ-TiAl-based alloy

The occurrence of nonequilibrium semi-coherent alpha(2)/gamma interfaces is an important microstructural feature of hot-deformed Ti-45Al-10Nb-2.5Mn-0.05B alloys. The feature of the alpha(2)/gamma interfaces is the misorientation from the conventional orientation relationship{111}(gamma) {0001}(alpha 2), (1 (1) over bar 0)(gamma) (11 (2) over bar 0)(alpha 2), as well as the asymmetry in the sense of interfacial boundary planes deviating from the equilibrium atomic planes (111)(gamma) or (0001)(alpha 2). Numerous interfacial ledges containing 1/3[111] Frank partial dislocations exist in this nonequilibrium semi-coherent alpha(2)/gamma interface. The analysis points toward the formation of this type of nonequilibrium alpha(2)/gamma interface accommodating the relative rotation of alpha(2) and gamma plates in the hot-deformation-induced bent lamellar structure. In the sharply bent lamellae, there even occur largely misoriented non-coherent alpha(2)/gamma interfaces with the {111}gamma plane no longer being parallel to the {0001}(alpha 2) plane. These interfaces result from the lamellae bending/kinking during heavy deformation. (C) 1998 Elsevier Science B.V. All rights reserved.