Atomic Structures of Linear Singularities at Close-Packed {111}γ∥(0001)α2 Interfaces in a 60Ti–40Al (at%) Alloy

Abstract

Linear singularities at or near close-packed {111}γ∥(0001)α2 interfaces in two-phase γ–α2 alloys play a crucial role in the plastic deformation at submicron scale. This paper presents an analysis of their atomic structures by high resolution electron microscopy using a two-phase 60Ti–40Al (at%) alloy deformed at 600 °C. Linear singularities appear as dislocation ledges (DLs) sparsely distributed for electron beam along 〈110〉γ, unlike in the case of beam parallel to 〈101〉γ. Most of them correspond to already reported Shockley DLs that are two or four {111}γplanes high. New singularities are investigated, namely: undissociated 1/2〈110〉γ (or less probably 1/2〈101〉γ) dislocations without ledge, dissociated 1/6〈112〉γ DLs, undissociated and dissociated 1/3〈111〉γ DLs, undissociated and slightly dissociated 1/6〈411〉γ DLs, and slightly dissociated 1/6〈521〉γ DLs. It is shown that some of these DLs separate interfacial facets with different atomic structural units, a point that prior analyzes have suggested. Image simulations using multislice and elasticity calculations are performed to determine unambiguously the positions of the core singularities in the vicinity of each ledge.