Weak-beam study of dislocations in D0₂₂-Al₃Ti deformed at 400°C

Abstract

Polycrystalline samples of Al₃Ti with the D0₂₂-type structure have been plastically deformed at 400°C. Observations using weak-beam transmission electron microscopy show activation of dislocations with <100] or <110] Burgers vectors. The fine structure of [100] and [010] dislocations reveals strong stabilization effect on the pure edge character. [110] superdislocations, resulting from the interactions between [100] and [010] perfect dislocations, are dissociated in two identical superpartials separated by an antiphase boundary (APB). Their segmented shape together with the separation distances between the [110] superpartials point to a large anisotropy of APB energies whose estimated values on (001) and (111) are 13 ± 3 mJ/m² and 64 ± 5 mJ/m², respectively. The low mobility of <100] and <110] dislocations is highlighted and related to the low ductility of this material.

Keywords:

• plastic deformation
• weak-beam transmission electron microscopy
• dislocation
• antiphase boundary
• intermetallic