Stoichiometry in Al-Mn-based icosahedral phases

Janot, Chr.; Pannetier, J.; Dubois, Jean‐Marie; Houin, J.P.; Weinland, P.

doi:10.1080/13642818808211244

Cited by 15 publications

(5 citation statements)

References 14 publications

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“…Thus, CT must be introduced as an adjustable parameter whose best value is chosen to minimize the presence of negative minima in both gTT and 9AIAl PPDF. A by product of the PPDF calculation is thus the most probable value of CT = 0.18 which defines the icosahedral phase composition as AI8o.94Si1.06 T 18 or A14.50S.06T, in good agreement with our previous estimations [37,38]. Such a composition of the icosahedral phase, when compared to the nominal compositions of the asprepared alloys, leads to a molecular fraction of the residual fcc-Al equal to 5.9 %, in good consistency with the range of values estimated from the subtraction procedure described in section 2.…”

supporting

confidence: 90%

“…Fortunately enough, the substitution of an equiatomic FeCr mixture (the so-called o-phase) for Mn happens to be isomorphous and random [36,37], a point further advocated and confirmed in the next section of this paper.…”

supporting

confidence: 53%

“…All the samples contained, in addition to icosahedral phase, a dispersed fraction of fcc-Al whose concentration has been determined elsewhere [37]. The diffraction peaks due to the icosahedral phase can be indexed after Cahn et al [39], as already done with high resolution powder diffraction data [24,36].…”

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confidence: 99%

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Partial pair distribution functions in icosahedral Al-Mn studied by contrast variation in neutron diffraction

Dubois¹,

Janot

1987

J. Phys. France

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Des phases icosaédriques des systèmes Al-Mn et Al-(MnFeCr) ont été étudiées par diffraction des neutrons, jusqu'à des vecteurs de diffusion de 16 Å-1. Les trois fonctions de distribution de paires partielles ont été calculées. On a pu ainsi confirmer sans ambiguïté le caractère parfaitement isomorphe de la substitution du Mn par 03C3-FeCr. Les corrélations de paires atomiques apparaissent très semblables à celles de la phase cristalline 03B1(AlMnSi). En particulier, les plus courtes distances Mn-Mn sont trouvées à 4,47 et 4,97 A. Abstract.-Icosahedral Al-Mn and Al-(MnFeCr) alloys were studied by neutron diffraction with scattering vectors up to 16 Å-1. The three partial pair distribution functions (PPDF) were obtained and the actual isomorphous substitution of the 03C3-FeCr mixture for Mn was confirmed. The PPDF for Mn-Mn indicates the existence of a manganese subnetwork rather similar to that found in the 03B1(AlMnSi) crystalline phase. In particular the shortest Mn-Mn distances were found at 4.47 and 4.97 A.

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confidence: 90%

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confidence: 53%

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Partial pair distribution functions in icosahedral Al-Mn studied by contrast variation in neutron diffraction

Dubois¹,

Janot

1987

J. Phys. France

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“…The calculation demonstrated the importance of including the 'glue' atoms for a realistic estimate of the diffraction intensities for the model. No attempts were made to include manganese among the 'glue' atoms in the a" structure in order to achieve the reported chemical composition for quasicrystals (Janot, Pannetier, Dubois, Houin & Weinland, 1988), nor was any refinement of atomic positions tried. Despite these limited efforts, the calculated X-ray powder diagram of the simple cubic model seems to fit with the published powder X-ray diagram as well as other published models.…”

Section: P(x Y O) = ~-]~[Ij/i1(qj)] Exp[27ri(hjx + Kjy)] Jmentioning

confidence: 99%

Approximants and Intermediate Stages during Transformation from a Quasicrystalline to a Crystalline Phase in an Al–Mn–Si Alloy

Hansen¹,

Gjønnes²

1996

Acta Cryst Sect A

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In precipitate particles formed by heat treatment of industrially cast Al-(1.8-1.6wt%)Mn alloys, a sequence of stages intermediate between the quasicrystalline I phase and the cubic a-A1MnSi phase have been found. Their electron diffraction patterns and images can be interpreted in terms of faults on { 110}~ planes, with a fault vector [350]/16 or [iTO]/2T 2, where 7-= 1.618 is the golden mean. A lattice generated by such faults on every (110)~ plane has as its unit cell a prolate rhombohedron (a') that is complementary to the oblate rhombohedron (a) that describes the packing of the MacKay icosahedra in a-A1MnSi. Domains of this new lattice have been observed. Based on the two rhombohedra, a cubic Pa3 structure model (a") with cell dimension 7-times aA1MnSi and nearest-neighbour intericosahedral vectors along all threefold axes of the icosahedron is proposed as a second approximant to the I phase in the system, with a-A1MnSi as the first approximant. Calculations of diffraction patterns and Patterson sections are presented as support for this proposal.

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“…However, it is believed that in many intermetallics including quasicrystals, the combined effect of these two elements in regard to phase formation is similar to the effect produced by a single element. Janot et al (1986Janot et al ( , 1988, while studying the icosahedral Al-Mn structure, have successfully substituted (isomorphous) Mn by (Fe, Cr) and found that the equiatomic mixture of Fe and Cr produces effects similar to those expected from Mn. But substitution of Fe by Cr shows that regarding phase formation these two elements behave differently e.g.…”

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confidence: 99%

Role of Fe substitution and quenching rate on the formation of various quasicrystalline and related phases

2001

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We have investigated Fe substituted versions of the quasicrystalline (qc) alloy corresponding to Al 65 Cu 20 (Cr, Fe) 15 with special reference to the possible occurrence of various quasicrystalline and related phases. Based on the explorations of various compositions it has been found that alloy compositions Al 65 Cu 20 Cr 12 Fe 3 and Al 65 Cu 20 Cr 9 Fe 6 exhibit interesting structural phases and features at different quenching rates. At higher quenching rates (wheel speed ~ 25 m/sec) all the alloys exhibit icosahedral phase. For Al 65 Cu 20 Cr 12 Fe 3 alloy, however, both the icosahedral and even the decagonal phases get formed at higher quenching rates. At higher quenching rate, alloy having Fe 3 at% exhibits two bcc phases, bccI (a = 8⋅ ⋅9 Å) and bccII (a = 15⋅ ⋅45 Å). The orientation relationships between icosahedral and crystalline phases are: Mirror plane || [001] bcc I and [351] bcc II , 5-fold || [113] bcc II and 3-fold || [110] bcc II. At lower quenching rate, the alloy having Fe 6 at% exhibits orthorhombic phase (a = 23⋅ ⋅6 Å, b = 12⋅ ⋅4 Å, c = 20⋅ ⋅1 Å). Some prominent orientation relationships of the orthorhombic phase with decagonal phase have also been reported. At lower quenching rate (~ 10 m/sec), the alloy (Al 65 Cu 22 Cr 9 Fe 6) shows the presence of diffuse scattering of intensities along quasiperiodic direction of the decagonal phase. For making the occurrence of the sheets of intensities intelligible, a model based on the rotation and shift of icosahedra has been put forward.

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Stoichiometry in Al-Mn-based icosahedral phases

Cited by 15 publications

References 14 publications

Partial pair distribution functions in icosahedral Al-Mn studied by contrast variation in neutron diffraction

Partial pair distribution functions in icosahedral Al-Mn studied by contrast variation in neutron diffraction

Approximants and Intermediate Stages during Transformation from a Quasicrystalline to a Crystalline Phase in an Al–Mn–Si Alloy

Role of Fe substitution and quenching rate on the formation of various quasicrystalline and related phases

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