A yield-stress anomaly was observed for ½[¯112](1¯11) slip in single crystals of γ-phase 54.5at%Al alloy. Weak-beam electron microscopy was used to determine the origin of this anomaly. At room temperature, screw and 60º dislocations dissociated on the glide plane, and 30º dislocations dissociated by glide on intersecting {111} planes to form weak locks. At high temperatures, ½[¯112] dislocation loops were elongated along their edge direction. These edge dislocations were dissociated, by climb and glide, into sessile configurations which consisted of Frank and Shockley partials on different intersecting {111} planes; with a stair-rod dislocation along the line of intersection. There was some evidence for further dissociation of the Frank partial. These strong locks were responsible for the yield-stress anomaly. The driving force for the anomaly was the reduction in dislocation energy. The mechanism involved climb, and this became easier with increasing temperature.

Yield Stress Anomalies in Single Crystals of Ti-54.5at%Al: II ½[¯112](1¯11) Slip. S.Jiao, N.Bird, P.B.Hirsch, G.Taylor: Philosophical Magazine A, 1999, 79[3], 609-25