Novel Type of Dislocation in an Al-Pd-Mn Quasicrystal Approximant

Abstract

A single crystal of the ${\ensuremath{\xi}}^{\ensuremath{'}}$-AlPdMn phase was plastically deformed in a three-point bending geometry. The deformed crystal shows a periodic lattice of phason lines. In a high-resolution electron microscopy (HREM) study a novel dislocation type, termed metadislocation, was observed for the first time. The magnitude of its Burgers vector is 171 \AA{}. At the core of the metadislocation a dislocation of the ${\ensuremath{\xi}}^{\ensuremath{'}}$ structure is found. For the first time its structure and Burgers vector were determined by HREM. In magnitude and direction it is equivalent to the most common Burgers vector in the icosahedral quasicrystal. The structural relationship between the dislocation and the metadislocation is discussed.