Cross-slip and glide behavior of ordinary dislocations in single crystal gamma-Ti-56Al

Authors
Citation
Q. Feng et Sh. Whang, Cross-slip and glide behavior of ordinary dislocations in single crystal gamma-Ti-56Al, INTERMETALL, 7(9), 1999, pp. 971-979
Citations number
26
Categorie Soggetti
Apllied Physucs/Condensed Matter/Materiales Science","Material Science & Engineering
Journal title
INTERMETALLICS
ISSN journal
09669795 → ACNP
Volume
7
Issue
9
Year of publication
1999
Pages
971 - 979
Database
ISI
SICI code
0966-9795(199909)7:9<971:CAGBOO>2.0.ZU;2-M
Abstract
Single crystals of Ti-56A1 deformed at 873 K in [1 6 3] and [1 12 5] orient ations exhibit anomalous hardening. The anomalous hardening increases with increasing the Schmid factor for cross-slip in (1 1 0) plane as well as a ( 1 1 1) cross-slip plane. The yield stress and CRSS show temperature depende nce as well as orientation dependence. The deformation structure of these c rystals was observed by TEM. The TEM study shows that ordinary dislocations of screw character were the main deformation structure, but these dislocat ions were frequently pinned by "superjogs" in (1 1 0) planes. The alloy wit h a higher flow stress shows a wide spread presence of the (1 1 0) edge dis location segments. These edge segments appear to have formed through a doub le cross-slip mechanism in which a screw dislocation cross-slipped onto (1 1 0)plane from the (1 1 1) primary slip plane and subsequently cross-slip a gain onto a (1 1 1) plane. This double cross-slip leaves a pair of short ed ge segments "superjogs" in (1 1 0) plane. It appears that these superjogs a re immobile in the forward direction, but mobile in the lateral directions. As a result, these (1 1 0) superjogs act as pinning points, but also, prov ide a Frank-Read source for formation of dislocation loops as well as dislo cation dipoles. These loops and dipoles probably contribute to alloy harden ing at high temperatures. (C) 1999 Elsevier Science Ltd. All rights reserve d.