The quasicrystalline transformation in the AlCr system

Lilienfeld, D. A.; Nastasi, M.; Johnson, H. H.; Ast, D. G.; Mayer, J. W.

doi:10.1557/jmr.1986.0237

Cited by 33 publications

(6 citation statements)

References 19 publications

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“…Phase formation of a quasicrystalline phase in an Al-Cr alloy by ion irradiation of an amorphous film was reported by Lilienfeld et al (1986). The structure of the binary phase Al 45 Cr 7 (-Al 7 Cr) phase was determined by Cooper (1960) in the space group C2/m, with a = 25.196, b = 7.574, c = 10.949 Å , = 128 43 0 .…”

Section: Structure Descriptionmentioning

confidence: 98%

Crystal structure of Al₄₅Cr₇C_0.32

Liu

Fan

2018

IUCr Data

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During a high-pressure sintering (HPS) process of a stoichiometric Al 7 Cr mixture, the ternary phase Al 45 Cr 7 C 0.32 (pentatetracontaaluminium heptachromium carbide) was obtained serendipitously. The C atom (occupancy 0.32) is irregularly surrounded by six Al atoms. Structure descriptionPhase formation of a quasicrystalline phase in an Al-Cr alloy by ion irradiation of an amorphous film was reported by Lilienfeld et al. (1986). The structure of the binary phase Al 45 Cr 7 (-Al 7 Cr) phase was determined by Cooper (1960) . During a project aimed at formation of quasicrystalline material in the Al-Cr system under high-pressure conditions, we obtained the title compound and learned that light atoms can be incorporated into the Al 45 Cr 7 host structure. We attribute the slight increase in the unit-cell lengths and the decrease in the monoclinic angle in comparison with the values of the binary phase reported by He et al. ) to the presence of partially occupied light atoms that must have been diffused into the crystal structure during the HPS process, or were present as impurities in the employed metals. In principle, the light atoms could be boron, nitrogen (from the BN crucible), or carbon (from the graphite liner). In fact, we found that the educts were contaminated by small amounts of carbon (see Supplementary information).The asymmetric unit of Al 45 Cr 7 C 0.32 comprises of sixteen Al, three Cr and one partially occupied C sites (occupancy 0.32). Since the host structure has been described in detail (Cooper, 1960; He et al., 2006), we discuss here only the role of the additional carbon atom in Al 45 Cr 7 C 0.32 . The position of the C1 atom in the crystal structure can be seen in Fig. 1. It is located on a site with symmetry m (Wyckoff position 4i) and is connected to six

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Section: Structure Descriptionmentioning

confidence: 98%

Crystal structure of Al₄₅Cr₇C_0.32

Liu

Fan

2018

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“…However, an orthorhombic phase was prepared by in situ heating of the -Al 11 Cr 2 phase at 1072 K for 2 h (Cao & Kuo, 2008b). The -Al 11 Cr 2 phase and the related orthorhombic phase are crucial for understanding the formation and stability of the Al-Cr icosahedral quasi-data reports crystal firstly reported by Lilienfeld et al (1986) shortly after the discovery of quasicrystals in rapidly solidified Al-Mn alloys (Shechtman et al, 1984). Inoue et al (1987) found that single-phase icosahedral quasicrystals have formed in the vicinity of about 15.4 at.% Cr in rapidly quenched Al-Cr alloys, and the quasicrystal can be approximately formulated to have the composition Al 11 Cr 2 .…”

Section: Structure Descriptionmentioning

confidence: 99%

Crystal structure of Al_2.95Cr_0.59, a phase closely related to the η-phase in the binary Al–Cr system

Geng¹,

Wen²,

Fan³

2020

IUCrData

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The monoclinic η-phase in the binary Al–Cr system was initially named by Bradley & Lu [Bradley & Lu (1937). J. Inst. Met. 60, 319–337] as having the composition Al11Cr2 (Al:Cr ratio = 5.5:1). Its crystal structure was later refined [Cao & Kuo (2008). J. Alloys Compd. 458, 30, 319–337] to have a slightly lower Al content (Al:Cr ratio = 5.16:1). In the present work, a monoclinic phase with composition Al2.95Cr0.59 (Al:Cr ratio = 5.04:1) was obtained by high-pressure sintering (HPS) of a stoichiometric Al11Cr2 mixture. Structure analysis of this phase, hereafter named η′, revealed a close relationship to the previously reported η-Al11Cr2 structure, but with different mixed-occupied sites. Five fully occupied sites exhibit refined site occupation factors of 0.899 (5), 0.984 (4), 0.977 (5), 0.946 (4) and 0.945 (4) for the corresponding Al atoms. Moreover, there are no split Al sites in the η′-structure as reported for the η-structure. The refined chemical composition of the η′-phase revealed that it comprises two Al atoms fewer and two Cr atoms more than the previously reported η-Al11Cr2 phase.

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“…So far, at least 20 binary quasicrystal systems have been found. [1][2][3][4][5][6] However, almost all binary quasicrystals were produced by rapid solidification, and they were in a metastable state. 7 Only one decagonal quasicrystal obtained by slow solidification in an Al-Co alloy was found to be a stable binary decagonal quasicrystal up to now, 8 although many stable decagonal quasicrystals have been obtained by a slow solidification and directional growth method in Al-Cu-Co, 9 Al-Cu-Co-Ge, 10,11 and Al-Co-Ni ͑Ref.…”

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Formation of a stable decagonal quasicrystal in cobalt ion implanted aluminum

Chen

Wang

1997

Applied Physics Letters

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A binary Al–Co decagonal quasicrystal has formed after 100 keV Co+-ion implantation into pure Al with a dose of 1.5×1017 ion/cm2, and the quasicrystal has shown a high thermal stability. The composition of stable decagonal quasicrystal is believed to be Al11Co4. Co+ ion implantation into Al first produced a multiple layer surface structure. The first layer was an amorphous layer. The second layer consisted of a decagonal quasicrystal and a coexisting amorphous phase. The amorphous phase in the implanted region where composition is close to Al11Co4 was transformed into the decagonal quasicrystal during annealing in a temperature range between 550 and 600 °C. Possible transformation mechanisms for the experimental results are discussed.

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The quasicrystalline transformation in the AlCr system

Cited by 33 publications

References 19 publications

Crystal structure of Al₄₅Cr₇C_0.32

Crystal structure of Al₄₅Cr₇C_0.32

Crystal structure of Al_2.95Cr_0.59, a phase closely related to the η-phase in the binary Al–Cr system

Formation of a stable decagonal quasicrystal in cobalt ion implanted aluminum

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The quasicrystalline transformation in the AlCr system

Cited by 33 publications

References 19 publications

Crystal structure of Al45Cr7C0.32

Crystal structure of Al45Cr7C0.32

Crystal structure of Al2.95Cr0.59, a phase closely related to the η-phase in the binary Al–Cr system

Formation of a stable decagonal quasicrystal in cobalt ion implanted aluminum

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Crystal structure of Al₄₅Cr₇C_0.32

Crystal structure of Al₄₅Cr₇C_0.32

Crystal structure of Al_2.95Cr_0.59, a phase closely related to the η-phase in the binary Al–Cr system