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→=-(-τ)-n(001), 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-, ε6-, and ξ-phases is discussed.

► Novel and highly complex dislocations were found in T-Al-Mn-(Pd, Fe) using high-resolution aberration-corrected STEM. ► The dislocations consist of a large core involving about 250 atoms and separated escort defects. ► 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. ► The defects were identified as a new metadislocation variant.