On the solidification of Al₆₂Cu₂₀Co₁₅Si₃ and Al₆₁Cu_19.5Co_14.5Si₅ alloys

Abstract

The solidification behavior of Al62Cu20Co15Si3 and Al61Cu19.5Co14.5Si5 alloys was studied by means of optical metallography, scanning and transmission electron microscopy, energy-dispersive x-ray analysis, powder x-ray diffraction, and differential thermal analysis. Slowly as well as rapidly cooled ingots of both alloys contained a decagonal quasicrystalline phase as the dominant phase with, additionally, several minor crystalline phases. The structure of the rapidly solidified Si-containing alloys was similar to that of the ternary Al65Cu20Co15 alloy. In the slowly solidified alloys the substitution of 3 at. % Al by Si did not change the basic phase constitution. Si was only partially incorporated in the decagonal phase and a significant quantity of Si was found in elemental form. The increase of Si concentration to 5 at. % resulted in the appearance of new minor phases.

Instability of Al‐Cu‐Co single quasicrystals at low temperature

“…The reflection was originated in the cubic τ-phase and identified in Ref. [9] as 100 reflection (the remaining reflections of the τ phase agree with the reflections of the decagonal phase).…”

“…This peak, of interplanar distance d = 0.29 nm, identified in Ref. [9] as 100 reflection, corresponds to the τ phase. Fig.…”

Twenty years of structure research on quasicrystals. Part I. Pentagonal, octagonal, decagonal and dodecagonal quasicrystals

“…A stability range of the d-phase 973 < T < 1350 K was found as well as a higher thermal expansion for the quasiperiodic plane than for the periodic direction. Some of the results of these authors were differently interpreted by Grushko, Wittmann, Urban (1992). The SAED patterns of an Al 62 Co 14 Cu 24 alloy annealed 1290 h at 700 C and 3500 h at 550 C were differed significantly from each other (Grushko, 1993c).…”

X‐ray topography study of deformed composites obtained by directional solidification of Al‐Cu‐Co alloy

“…Figure 2b presents the back-scattering electron image of the composite layer, which was cut as a microsection parallel to the ZY plane. The cross-sections of the fibres with irregular (F 1 −F [12,14], tetragonal Θ phase (stoichiometric formula Al 2 Cu) [11,12] and regular β phase (stoichiometric formula Al(Cu,Co)) [11][12][13]. The nomenclature of phases used above complies with [12].…”

“…The average errors in the estimated chemical composition was about 0.5 at% for Al and about 0.3 at% for Cu and Co. Figure 3 shows an example of the X-ray diffraction pattern of the material of the composite layer. From the calculated interplanar distances the following phases were identified: the D phase [11], the T phase [11,15,16], the Θ phase [17] and the β phase [18]. The electron diffraction pattern (insert in fig.…”