Single crystals of γ-phase material, with 2 different orientations, were deformed at temperatures between ambient and 1223K. Both samples exhibited a yield-stress anomaly. The operating slip systems and dislocation structures were determined by means of optical and transmission electron microscopy, and the dissociation of the [011] super-lattice dislocations was studied by using the weak-beam technique. Most of the slip, in both crystals, occurred via [011] super-dislocations at temperatures below the yield-stress peak. The anomaly therefore mainly reflected an anomaly in [011](1¯11) slip. At room temperature, these dislocations dissociated on the (1¯11) glide plane but, at higher temperatures, the screw dislocations formed Kear-Wilsdorf locks, which were the cause of the anomaly. Above the peak-stress temperature, glide occurred via ordinary slip on {110} planes in one crystal and via [001](¯110) slip and ordinary slip and climb in the other crystal. Evidence was found for a yield-stress anomaly in ½[¯112](1¯11) slip.

Yield Stress Anomalies in Single Crystals of Ti-54.5at%Al: Overview and <011] Super-Dislocation Slip S.Jiao, N.Bird, P.B.Hirsch, G.Taylor: Philosophical Magazine A, 1998, 78[3], 777-802