Twin-transformed lattice defects in γ-TiAl

Abstract

We study the transformation of lattice defects in γ-TiAl upon intersection by deformation twins. A faulted dipole is chopped forming a dislocation loop faulted on the cube plane of the twin; faulted dipoles and twin loops may shrink at different rates. Dislocations with 1/2<110] and <011] Burgers vectors gliding on octahedral planes are transformed into configurations with low mobility on {010} plane. Elementary mechanisms involved in the transformation are considered and a pole mechanism for twin growth at forest dislocations is proposed.

Acknowledgements

Professor Marek Niewczas is thanked for enlightening discussions on the principles of lattice defect transformation by twinning during the stay of one of us (P.V.) at McMaster University. Professor Georges Saada is gratefully acknowledged for having provided us with a copy of the chapter on twinning before the publication of his book, for having drawn Gérard Fontaine's pioneering work on twinning to our attention and for ever challenging comments.