PLASTIC-DEFORMATION BEHAVIOR AND DISLOCATION-STRUCTURE IN TI3AL SINGLE-CRYSTALS CYCLICALLY DEFORMING BY PRISM SLIP

The effect of prism slip on cyclic hardening and deformation substruct ure in Ti3Al single crystals cyclically deformed was examined. Fatigue tests were carried out in a symmetrical tension/compression mode at a fixed total strain amplitude (Delta epsilon) of +/- 0.2% to +/-0.4% a t room temperature. As Delta epsilon and the number of cycles increase d, the stress amplitude rose depending on crystal orientation. The cyc lic hardening was more accelerated for specimens deformed by double pr ism slips than for those deformed by single prism slip. At the saturat ed stage, the edge dipoles and/or multipoles gathered at a localized r egion and formed bundles with a high residual stress field in specimen s deforming by double prism slips, while a high density of dislocation s existed the bundled structure did not develop under operation of sin gle prism slip. The peculiar structure containing bundles was called s aturated bundled structure (SBS). The formation process of the SBS and the role of the bundled structure on the plastic behaviour are descri bed. (C) 1998 Acta Metallurgica Inc. Published by Elsevier Science Ltd . All rights reserved.