Cyclic deformation behavior and dislocation structure of Ti-2 at. Pct Al single crystals oriented for double prism slip

Abstract

Cyclic deformation behavior and dislocation substructure in the single crystals of Ti-Al alloy containing 2.0 pct Al (by atom) with double prism slip at different cyclic strain amplitudes were examined. The testing results showed that Ti-2Al displayed an initial slight cyclic hardening followed by a striking softening period, and a saturation stage was reached finally. Secondary cyclic hardening was observed for most specimens before failure, specifically at the high cyclic strain amplitudes. The cyclic resolved shear stress-strain curve (CSSC) was observed to contain a plateau in the testing strain range with a saturation plateau stress of about 55 MPa. Trace analysis on the surface of specimens with an optical microscope shows that the (10 $$\bar 1$$ 0) and (1 $$\bar 1$$ 00) double prism slips can be distinguished from the traces on the (0001) surface of the fatigued specimens. The dislocation substructure in the fatigued specimens was examined using a transmission electron microscope (TEM). The typical dislocation configuration is the saturated dislocation bundles, which are tangled on the (10 $$\bar 1$$ 0) and (1 $$\bar 1$$ 00) slip planes and arranged parallel to the [0001] direction.