Metadislocations in the complex metallic alloys T-Al-Mn- (Pd, Fe)

We investigate dislocations in the complex metallic alloys T-Al-Mn-Pd and T-Al-Mn-Fe using high-resolution aberration-corrected scanning transmission electron microscopy. The dislocations consist of a large core and separated escort defects [1]. Upon movement, dislocations and escort defects locally transform the material and introduce stacks of planar faults which represent a slab of a different but related structure. Deformation modes involving glide and climb are observed. We find different types of dislocations with Burgers vectors (b) over bar = -(-tau)(-n)(0 0 1), with n = 2, 3, 4. They are associated to two, four and six planar faults, respectively, and are identified as metadislocations. The structural connection between metadislocations in the present phase and those in R-, epsilon(6)-, and xi-phases is discussed. (C) 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.