Structure and Stability of Quasicrystalline Al–Mn Alloys

Kimura, Kaoru; Hashimoto, Takashi; Suzuki, Kunio; Nagayama, Katsuhisa; Ino, Hiromitsu; Takeuchi, Shin

doi:10.1143/jpsj.55.534

Cited by 59 publications

(7 citation statements)

References 17 publications

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“…1 and 2(a) indicates an unconstrained growth in the liquid suggesting nucleation of quasicrystals prior to the nucleation of a-aluminium. There is now a consensus that the I phase composition is around 20 at% Mn (Kimura et al, 1986;Krishnan et al, 1986). Therefore the driving force for homogeneous nucleation in dilute A1-5% Mn melt will be very low and consequently a very high undercooling will be required for homogeneous nucleation.…”

Section: Morphology Of Icosahedral Quasicrystalsmentioning

confidence: 99%

Electron microscopy and diffraction of icosahedral and decagonal quasicrystals in aluminium‐manganese alloys

Thangaraj

Subbanna

Ranganathan

et al. 1987

Journal of Microscopy

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SUMMARY Electron microscopic observations on the morphology of icosahedral and decagonal quasicrystals in aluminium‐manganese alloys have been interpreted in favour of a heterogenous nucleation mode. The transition of icosahedral quasicrystals from nonfacetted dendrites to facetted particles occurs as a function of composition. While the variety of electron diffraction patterns to be expected from icosahedral quasicrystals has been demonstrated for a number of alloys, subtle intensity differences exist among analogous patterns from Al‐Mn, Al‐Cr, Al‐Mn‐Si and Mg‐Al‐Zn‐Cu alloys. Electron diffraction patterns from decagonal quasicrystals can be understood on the basis of an edge‐centred icosahedron as opposed to a vertex‐centred icosahedron for icosahedral quasicrystals. Truncation from two‐dimensional quasicrystals is discussed.

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Section: Morphology Of Icosahedral Quasicrystalsmentioning

confidence: 99%

Electron microscopy and diffraction of icosahedral and decagonal quasicrystals in aluminium‐manganese alloys

Thangaraj

Subbanna

Ranganathan

et al. 1987

Journal of Microscopy

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“…Considering the improved mechanical properties of Al-based alloys compared to commercially available equivalents (which is due to the presence of an I-phase in the microstructure), efforts are being made to obtain two-phase microstructure comprised solely of quasicrystalline particles embedded in an Al matrix, by casting methods involving less severe cooling conditions [14][15][16][17][18]. After the discovery of quasicrystals by Shechtman [19], the solidification of Al-Mn binary alloys was widely studied, including rapid solidification experiments [20][21][22][23][24], casting at intermediate cooling rates [25,26] and reinvestigation of the Al-Mn equilibrium phase diagram [27,28]. Based on the previous results, a metastable icosahedral phase can be obtained in alloys containing 2.5-21 at.% of Mn [19][20][21][22][23][24][25][26]29] using rapid solidification techniques, especially a melt spinning with cooling rates in the range of 10 4 -10 7 K/s [30] and electron beam melting [21,31].…”

Section: Introductionmentioning

confidence: 99%

Formation of a quasicrystalline phase in Al–Mn base alloys cast at intermediate cooling rates

et al. 2017

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Al-rich 94Al-6Mn and 94Al-4Mn-2Fe alloys were suction-cast to evaluate the feasibility of obtaining bulk quasicrystal-strengthened Al-alloys at intermediate cooling rates alloyed with non-toxic, easily accessible and affordable additions. The influence of different cooling rates on the potential formation of a quasicrystalline phase was examined by means of scanning and transmission electron microscopy, X-ray diffraction and differential scanning calorimetry. Increased cooling rates in the thinnest castings entailed a change in sample phase composition. The highest cooling rates turned out to be insufficient to form an icosahedral quasicrystalline phase (I-phase) in the binary alloy. Instead, an orthorhombic approximant phase occurred (L-phase). The addition of Fe to the 94Al-6Mn binary alloy enhanced the formation of a quasicrystalline phase. At intermediate cooling rates of 10 2 -10 3 K/s, various metastable phases were formed, including decagonal and icosahedral quasicrystals and their approximants. Rods (1 mm in diameter) composed of I-phase particles embedded in Al matrix exhibited a hardness of 1.5 GPa, much higher than the 1.1 GPa of 94Al-6Mn.

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“…In contrast, when metastable QC is formed by rapid solidification, it can be characterized by an uneven distribution of quenched phasons, which is a quasiparticle representing the movements of atoms just like phonon, and chemical disorder 17 The amount of disorder in metastable QC is known to increase as the cooling rate increases and it is also dependent on the alloy composition. Finally, metastable QC can be transformed into a stable AC at high temperatures, as recorded in the reported result that Al-Mn metastable QC with the same basic structural units, called the Mackey cluster, was transformed with little changes in composition 31 . Therefore, the interface www.nature.com/scientificreports/ energy between the newly formed AC and QC matrices is expected to be small, even though the exact value of the interface energy is not yet known.…”

Section: Discussionmentioning

confidence: 67%

Quasicrystalline phase-change memory

Lee

Yoo

Yoon

et al. 2020

Sci Rep

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phase-change memory utilizing amorphous-to-crystalline phase-change processes for reset-to-set operation as a nonvolatile memory has been recently commercialized as a storage class memory. Unfortunately, designing new phase-change materials (PCMs) with low phase-change energy and sufficient thermal stability is difficult because phase-change energy and thermal stability decrease simultaneously as the amorphous phase destabilizes. This issue arising from the tradeoff relationship between stability and energy consumption can be solved by reducing the entropic loss of phase-change energy as apparent in crystalline-to-crystalline phase-change process of a Gete/Sb 2 te 3 superlattice structure. A paradigm shift in atomic crystallography has been recently produced using a quasi-crystal, which is a new type of atomic ordering symmetry without any linear translational symmetry. This paper introduces a novel class of PCMs based on a quasicrystalline-toapproximant crystalline phase-change process, whose phase-change energy and thermal stability are simultaneously enhanced compared to those of the Gete/Sb 2 te 3 superlattice structure. This report includes a new concept that reduces entropic loss using a quasicrystalline state and takes the first step in the development of new PCMs with significantly low phase-change energy and considerably high thermal stability.

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Structure and Stability of Quasicrystalline Al–Mn Alloys

Cited by 59 publications

References 17 publications

Electron microscopy and diffraction of icosahedral and decagonal quasicrystals in aluminium‐manganese alloys

Electron microscopy and diffraction of icosahedral and decagonal quasicrystals in aluminium‐manganese alloys

Formation of a quasicrystalline phase in Al–Mn base alloys cast at intermediate cooling rates

Quasicrystalline phase-change memory

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