On the mechanism of [formula omitted] dipole formation in TiAl

Abstract

〈 101〉> superdislocations in TiAl can dissociate on discrete segments of the dislocation line and generate trailing ± 1 6 〈 112〉 or ± 1 3 〈 211〉 dipoles. A mechanism for ± 1 3 〈 211〉 dipole formation from a 〈 101〉 superdislocation dissociated on two adjacent (111) planes is discussed. The non-coplanar 〈 101〉 core structure may arise either from direct dissociation by the cross-slip of a 1 2 〈 101〉 superpartial, or by an initial 〈 101〉 → 1 2 〈 110〉 + 1 2 〈 112〉 decomposition of the superdislocation and the subsequent pinning of the 1 2 〈 110〉 perfect dislocation by an immobile 1 6 〈 112〉 delocalised partial associated with a non-coplanar 1 2 〈 112〉 superdislocation core.