Metadislocations in Complex Metallic Alloys

Complex Metallic Alloys (CMAs) represent a large group of crystalline intermetallics comprising some hundreds of known phases in various alloy systems. They are characterized by the presence of icosahedral atom coordination, large lattice constants, and a correspondingly large number of atoms per unit cell, typically ranging between a few tens and some thousand [1]. In recent years, CMAs have attracted increasing research interest and exceptional properties have been found e.g. [2]. Several CMAs also show unusual plastic properties, the occurrence of new plastic-deformation mechanisms and novel defects [3]. Most prominent among those novel defects are metadislocations [3,4], which are considered the most complex defects in materials science as they involve several hundreds of atoms in their core. They are partial dislocations which are not associated to conventional planar defects but to slabs of a structurally transformed complex phase or a certain number of so-called phason planes. Metadislocations were first observed in the CMAs ε6and ε28-Al–Pd–Mn [3,4], later in ε-type Al–Pd–Fe [5], Al13Co4 [6], and in T-Al-Mn-Pd [7,8].