Dislocation dipoles in cyclically deformed Ti₃Al single crystals

Dislocation dipoles and debris in Ti₃Al single crystals fatigued at 300 and 77 K were examined focusing on geometric configuration and formation mechanism of superlattice dislocation dipole (superdipole). Longer and lower density debris were observed more at 77 than at 300 K. Although the superdipoles composed of S-type and Z-type configurations may exist, all superdipoles observed in present Ti₃Al had Z-type stable configuration. Geometric configuration of superdipoles was calculated on the basis of elastic theory. The superdipole height was estimated from the relation between the height and the separation distance of each superpartial in the superdipole. Debris (short superdipoles) formation is triggered dominantly by jog formation due to the double cross slip and it is controlled by the thermally activated pinching off process.