Atomistic Studies of Dislocation Glide in gamma-TiAl

Computer simulation of the core structure and glide of ordinary 1/2<110] dislocations and <101] superdislocations in L10 TiAl has been performed using the recently constructed Bond-Order Potentials. This description of atomic interactions includes explicitly, within the tightbinding approximation, the most important aspects of the directional bonding, namely d-d, p-p and d-p bonds. The ordinary dislocation in the screw orientation was found to have a non-planar core and, therefore, high Peierls stress. The superdislocation was found to possess in the screw orientation either a planar (glissile) or a non-planar (sessile) core structure. However, the glissile core transforms into the sessile one for certain orientations of the applied stress. This implies a strong asymmetry of the yield stress and the break down of the Schmid law when the plastic flow is mediated by superdislocations. At the same time, this may explain the orientation dependence of the dislocation substructure observed in the single-phase gamma-TiAl by electron microscopy. Comments Copyright Materials Research Society. Reprinted from MRS Proceedings Volume 753. 2002 Fall Meeting Symposium BB Defect Properties and Related Phenomena in intermetallic Alloys Publisher URL: http://www.mrs.org/members/proceedings/fall2002/bb/BB4_3.pdf This conference paper is available at ScholarlyCommons: http://repository.upenn.edu/mse_papers/9 ATOMISTIC STUDIES OF DISLOCATION GLIDE IN γγ-TiAl R. Porizek*, S. Znam*, D. Nguyen-Manh**, V. Vitek* and D. G. Pettifor** *Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania, 19104-6272, U.S.A; **Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, UK