Micromechanisms of deformation in γ-TiAl

ABSTRACTInvestigations conducted in our group on plastic properties of a variety of strained TiAl based alloys and resulting microstructures are reviewed. These include oriented single crystals of Al-rich γ-TiAl and semi-oriented polycrystals with γ + α2 lamellar structure. The wealth of micro-mechanisms encountered in this family of alloys is, to large extent, due to the decomposition of <011] dislocations: <011] ↔ 1/2<112] + 1/2<110]. This transformation sometimes introduces serious uncertainties as to which slip systems were actually operating during deformation. Another transformation involving decomposition is the formation of intralamellar networks during deformation. Mechanisms not involving decomposition include the trailing of faulted dipoles by <011] dislocations and the generation of arrays of prismatic loops of ordinary dislocations. The latter maneuver is at the origin of fundamental processes such as self-organisation in single slip in a variety of crystals.