Orientation Dependent Strength and Cross-Slip Structure of Ordinary Dislocations in Single Crystal γ-Ti-56A1

ABSTRACTThe temperature as well as orientation dependence in anomalous hardening occurs in single crystal Ti-56AI between 673K and 1073K under single slip of ordinary dislocations. The ordinary dislocations (1/2<110]) are gliding not only on (111) plane but also on (110) plane in the temperature range where the anomalous hardening occurs in single crystal Ti-56A1. The TEM study shows that the (110) cross-slip of ordinary dislocations is a double cross-slip in nature in which first, the dislocations cross-slip from the primary (111) slip plane to (110) plane followed by cross-slipping again onto another primary slip plane. This double cross-slip leaves a pair of edge segments 'superjogs' in (110) planes. It appears that these superjogs are immobile in the forward direction and act as pinning points. Furthermore, these pinning points would act as a Frank-Read source for the double cross-slipped dislocations, which generate dislocation loops as well as dislocation dipoles. The pinning structure, multiplane dislocation loops, and dipoles of double cross-slip origin all contribute to anomalous hardening at high temperatures in this material.