Intralamellar dislocation networks formed by glide in γ-TiAl. I. The mechanism of formation

In a lamellar TiAl alloy deformed at room temperature under an orientation that activates slip parallel to the interfaces, the γ phase exhibits intralamellar dislocation networks parallel to the primary slip plane and entirely glissile in their habit plane. Their meshes are mainly rectangular with branches all coplanar, screw or near-screw in character and with Burgers vector of 1/2 〈110] and 1/2〈112] types. Dislocation organization at and in the near-vicinity of these intralamellar networks suggests a reaction between a family of primary coplanar <011] dislocations that slip in the network habit plane and a family of 1/2〈110] dislocations that cross-slip from a plane inclined to the lamellae into the network. The reactions result in junctions with 1/2〈112] Burgers vector that subsequently transform into rectangular units. The presence of these networks is consistent with that of a residual elastic twist between adjacent γ lamellae.