Metadislocations in the structurally complex orthorhombic alloy Al₁₃Co₄

Abstract

The existence of metadislocations in the complex, orthorhombic phase metallic alloy Al₁₃Co₄ has been postulated [Phil. Mag. 86 985 (2006)]. The present work is a microstructural characterization of defects in this phase by means of transmission electron microscopy. A dislocation core region and associated planar defects were investigated in a plastically deformed sample. The planar defects were shown to be (0 0 1) slabs of a monoclinic phase in the orthorhombic Al₁₃Co₄ matrix. Microstructural investigations reveal the presence of an edge dislocation. The strain at the dislocation core is partially compensated by the introduction of the monoclinic phase. A structural model of the core region, based on a tiling description, is developed. The Burgers vector of the dislocation yields −2.9 Å [0 1 0], which is a small irrational fraction of the lattice constant. A comparison with metadislocations and dislocations in Laves phases is made and a definition of a metadislocation, including metadislocation glide, is established.

Keywords:

• complex metallic alloy
• TEM
• aberration-corrected STEM
• dislocation
• metadislocation
• structural transformation

Acknowledgments

This work was supported by the Deutsche Forschungsgemeinschaft (PAK 36), and the 6th Framework EU Network of Excellence ‘Complex Metallic Alloys’ (Contract No. NMP3-CT-2005-500140).