The cyclic deformation behaviour of [21•0]-oriented Ti-5at%Al single crystals was investigated at total (elastic+plastic) axial strain amplitudes of 0.195 to 0.798% at room temperature in air. The crystals exhibited initial cyclic hardening, followed by a striking softening period. A saturation stage was then reached at different cyclic strain amplitudes; except at the lowest (0.195%), where the initial hardening stage was absent. The cyclic stress-strain curve for a Ti-5at%Al single crystal, with double prism slip, exhibited a clear plateau with a saturation shear stress of 86 to 89MPa over the entire range of applied strain amplitudes. The (10•0) and (11•0) double-prism slip systems could be distinguished from their traces on the (00•1) surface. The slip marking was planar, and became denser as the cyclic strain amplitude increased. Two groups of planar dislocation lines, lying along the (10•0) and (11•0) prism plane traces, were identified in the (00•1) reflection by using transmission electron microscopy. The typical dislocation configuration was that of planar dislocation bands lying parallel to the [00•1] direction in a foil with a (10•0) normal. However, long straight dislocations were formed in a (11•0) foil. The widths and spacings of the slip bands in the (10•0) primary slip plane decreased with increasing cyclic strain amplitude.

Cyclic Deformation Behaviour and Dislocation Structure of Ti-5at%Al Single Crystals Oriented for Double Prism Slip. L.Xiao, Y.Umakoshi: Philosophical Magazine A, 2002, 82[12], 2379-96