On the mechanism of ± 13 〈211〉 dipole formation in TiAl

Abstract

$\text{〈}\text{1}\text{01〉>}$ superdislocations in TiAl can dissociate on discrete segments of the dislocation line and generate trailing $\text{±}\text{1}\text{6}\text{〈}\text{11}\text{2〉}$ or $\text{±}\text{1}\text{3}\text{〈}\text{2}\text{11〉}$ dipoles. A mechanism for $\text{±}\text{1}\text{3}\text{〈}\text{2}\text{11〉}$ dipole formation from a $\text{〈}\text{1}\text{01〉}$ superdislocation dissociated on two adjacent (111) planes is discussed. The non-coplanar $\text{〈}\text{1}\text{01〉}$ core structure may arise either from direct dissociation by the cross-slip of a $\text{1}\text{2}\text{〈}\text{1}\text{01〉}$ superpartial, or by an initial $\text{〈}\text{1}\text{01〉 →}\text{1}\text{2}\text{〈}\text{1}\text{10〉 +}\text{1}\text{2}\text{〈}\text{11}\text{2〉}$ decomposition of the superdislocation and the subsequent pinning of the $\text{1}\text{2}\text{〈}\text{1}\text{10〉}$ perfect dislocation by an immobile $\text{1}\text{6}\text{〈}\text{11}\text{2〉}$ delocalised partial associated with a non-coplanar $\text{1}\text{2}\text{〈}\text{11}\text{2〉}$ superdislocation core.