The deformation mechanisms in fully lamellar material which was crept at 760C were investigated. It was found that, due to the fine structure, the motion and multiplication of dislocations within both γ and α2 lamellae were limited at creep stresses below 400MPa. The glide and climb of lattice dislocations therefore made an insignificant contribution to creep deformation. On the other hand, the motion of interfacial dislocations on γ/α2 and γ/γ interfaces (interface sliding) dominated deformation at low stresses. It was found that the main obstacles which impeded the motion of interfacial dislocations were lattice dislocations that impinged upon lamellar interfaces. The number of impinging lattice dislocations increased as the applied stress increased, and caused the pile-up of interfacial dislocations at the interfaces. The pile-ups then led to the formation of deformation twins. Deformation twinning which was activated by the pile-up of interfacial dislocations was suggested to be the predominant deformation mechanism at stresses above 400MPa.

Role of Interfacial Dislocations on Creep of Fully Lamellar TiAl. T.G.Nieh, L.M.Hsiung: Key Engineering Materials, 2000, 171-174, 685-92