S. Balanetskyy

Orthorhombic ε-phases and transitional structures in Al-Pd-(Fe)

Abstract The results of an investigation of the structures formed in the range of about Al73Pd27 to Al76Pd14Fe10 by electron diffraction and high-resolution transmission microscopy are reported. The orthorhombic ε6, ε16, ε22 and ε28 phases were observed in specific compositional sub-ranges. Their lattice parameters a ≈ 2.34 and b ≈ 1.62 nm are essentially the same while the c parameters are ≈1.23, 3.24, 4.49 and 5.70 nm, respectively. Apart from these regular structures, also structures aperiodic along the c-direction are revealed at intermediate compositions. Thus, inside the wide ε-phase range only slight continuous variations of the orthorhombic a and b cell parameters are accompanied by complicated modulations of the c cell parameter.

A study of phase equilibria in the Al-rich part of the Al-Mn alloy system

Abstract Following new findings by Y. Du et al. (Int. J. Mater. Res. 98 (2007) 855), the Al-Mn phase diagram was re-examined in the compositional range of ∼4 to 27 at.% Mn using scanning and transmission electron microscopy, energy-dispersive X-ray analysis and differential thermal analysis. The corrections to the Al-Mn phase diagram concerning the reactions involving the Al6Mn and Al4Mn phases reported in the above-mentioned contribution were not confirmed. Instead, our results were in agreement with those reported earlier by Murray et al. (Metall. Trans. A18 (1987) 385): the reaction Al6Mn + μ ↔ λ occurs at 695 °C, and L + μ ↔ Al6Mn at 705 °C. At higher Al concentrations, the reactions μ ↔ L + T, μ + v ↔ T and T ↔ L + γ1 were revealed at ∼923, 913°C and 1001 °C, respectively, in good agreement with the literature data. Kinetic effects during phase transitions of the Al-Mn alloys are discussed on the basis of experimental results.

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 τ times larger in diameter than that in Al—Pd—Mn.

Structural variations in ϵ -type Al–Pd–(Mn, Fe) complex metallic alloy phases

Structural modifications in complex metallic ε-Al–Pd–(Mn, Fe) samples were studied by means of transmission electron microscopy. The modifications were observed in the vicinity of metadislocations and at phase boundaries. They are determined by the density and inclination of phason planes. In the vicinity of metadislocations and at an ε6–ε28 phase boundary, new monoclinic ε-type structures appear locally, which had not been detected as bulk phases in Al–Pd–(Mn, Fe) previously. The present work points out the close entanglement between defects, i.e. metadislocations and phason planes, and structural modifications in ε-type complex metallic alloys. An extended classification of ε-type phases including monoclinic phases is presented on the basis of two different tiling descriptions.

The influence of thermal annealing on structural order in the μ-Al4Mn complex intermetallic

Abstract The influence of cooling rate on structural order in the complex hexagonal μ-Al4Mn phase was investigated. As higher magnetizations are detected in more disordered samples, the short-scale disorder was studied indirectly by magnetic measurements. The magnetizations of as-grown samples and samples subjected to different thermal treatments were compared. It was found that water-quenching increases the disorder in the crystal structure regardless of previous thermal history. Qualitatively the same results were obtained for the quasicrystalline i-Al—Pd—Mn phase where the changes in magnetic properties and consequently in the degree of structural order for different thermal treatments were even more pronounced.