Decagonal quasicrystal of a new structural type

Abstract

A stable decagonal phase of a new structural type was discovered in Al—Pd—Re. This is the second Al-based alloy system after Al—Pd—Mn where both stable icosahedral and decagonal phases are formed. In contrast to the isostructural icosahedral phases of similar Al and Pd concentrations in both systems, the new decagonal phase exhibits periodicity of ∼2.57 vs. ∼1.25 nm in Al—Pd—Mn and is formed at significantly higher Al concentration than that in Al—Pd—Mn. In the tenfold plane, the structural unit of the Al—Pd—Re decagonal phase assumed from the high-resolution electron images is

Reinvestigation of the Al–Mn–Pd alloy system in the vicinity of the T- and R-phases

“…The line-up of phases observed is in good agreement with previous works on the Al-rich region of the bounding binary AleMn and AlePd alloy systems [6,25,30,31]. We confirm the formation of the binary AleMn phases Al 6 Mn, m-, T-Al 11 Mn 4 (low-temperature triclinic modification of the orthorhombic T-phase), g 1 , and g 2 , and the binary AlePd phases d-Al 3 Pd 2 , 3 6 , and 3 28 in the compositional and temperature range investigated.…”

“…A structural relation between the 3 6 and T-phase exists also with respect to the formation of specific defects, which can be represented by additional tiles, the so-called ''boat-shaped heptagon'' in the case of T and the ''banana-pentagon'' in the case of 3 6 [2,12,21]. The latter defects play a pivotal role in plasticity and phase transformation of 3 6 -phases: the banana-pentagons may be arranged in the form of (001) planes in the 3 6 -matrix, forming the so-called phason planes [12,22]. Several periodic and aperiodic superstructures based on specific ordering of phason planes in 3 6 -matrix are known in the Ale(TM)ePd (TM ¼ Cr, Mn, Fe, Co) alloy systems (cf.…”

“…Refs. [22,23]). A novel type of complex defect, the so-called metadislocation, forms by association of a specific number of phason planes to partial dislocations [24].…”

Formation of Complex Intermetallics in the Al-Rich Part of Al-Pt-Ru

“…In Al-based alloy systems only the Al-Pd-Re decagonal phase is known to be stable at such a high Al concentration, but it belongs to the D 6 structural type (2.57 nm periodicity in the specific direction). [13] The D 6 -phase composition is Al 78.0 Pd 7.8 Re 14.2 . No decagonal phase was revealed in Al-Pd-Ru (Ref 14 and references therein).…”

Physical properties of the complex metallic alloy phases in the Al–Pd–Mn system

“…Among the CMA materials, an interesting family of related structures was revealed in the Al-Pd alloys system [3,4] and its ternaries with transition metals (Mn, Fe, Co, Rh) [5][6][7][8][9]. The simplest regular structure discovered first in the Al-Pd-Mn [5,6] system, designated as ξ', contains 320 atoms in its orthorhombic unit cell.…”