Crystal structure of rhombohedral λ-AlFeSi

Sugiyama, Kazumasa; Kaji, N.; Hiraga, Kenji

doi:10.1016/j.jallcom.2003.08.065

Cited by 10 publications

(4 citation statements)

References 18 publications

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“…Powder XRD patterns indicate that a single phase is present for the binary compositions θ (Al 13 Fe 4 ) and η (Al 5 Fe 2 ) but contaminants in all ternary phases (τ 2 –τ 6 ; Figure A). Such impurities in the ternary phases are to be expected, given the complex interaction between many phases in the aluminum-rich corner of the ternary phase diagram for Al-Fe-Si. ,, Rietveld refinements on each XRD pattern nonetheless confirm that the majority component of each characterization standard is the desired phase: θ can be refined to the C 2/ m space group (ICSD 57795), η to Cmcm (ICSD 57796), τ 2 to R -3 (ICSD 99169), τ 3 to Cmma (ICSD 40317), τ 4 to I 4/ mcm (ICSD 199347), and τ 5 to P 6 3 / mmc (ICSD 422224) . Refinements on attempted syntheses of τ 6 showed a small amount of the expected A 2/ a (ICSD #54050) phase (Figure B and Figures S1–S6) but always as a minor component.…”

Section: Resultsmentioning

confidence: 96%

Raman Spectroscopic Analysis of the Reaction between Al-Si Coatings and Steel

2023

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Hot-stamped ultrahigh strength steel components are pivotal to automotive light-weighting. Steel blanks, often coated with an aluminum-silicon (Al-Si) layer to protect them from oxidation and decarburization, are austenitized within a furnace and then simultaneously quenched and formed into shape. The Al-Si coating melts within the furnace and reacts with iron from the steel to yield an intermetallic phase that provides some long-term corrosion protection. During the intermediate liquid phase, some of the coating may transfer to the furnace components, leading to maintenance costs and operational downtime. A detailed understanding of the coating transformation mechanism is needed to avoid such production issues while ensuring that final intermetallic coatings conform to specifications. We introduce cross-sectional Raman microscopic mapping as a method to rapidly elucidate the coating transformation mechanism. Raman spectroscopic fingerprints for relevant intermetallic compounds were determined using synthesized Al-Fe-Si ternary and Al-Fe binary compounds. These fingerprints were used to map the spatial distribution of intermetallic compounds through cross sections of Al-Si-coated 22MnB5 specimens that were heated at temperatures between 570 and 900 °C. These chemical maps show that the intermetallic fraction of the coating does not grow significantly until formation of η (Al5Fe2) at the steel interface, suggesting that η facilitates extraction of iron from the steel and subsequent diffusion through the coating. Under the heating conditions used here, a series of reactions ultimately lead to a silicon-rich τ2 (Al3FeSi) phase on top of the binary η phase. The technique presented here simplifies structural analysis of intermetallic compounds, which will facilitate prototyping of strategies to optimize hot stamping.

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Section: Resultsmentioning

confidence: 96%

Raman Spectroscopic Analysis of the Reaction between Al-Si Coatings and Steel

2023

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“…Our original interest in TM–Al–Si phases began with a casual examination of the structure of Fe 25 Al 78 Si 20 (Figure ) . In looking at the connectivity between the main-group atoms in this structure, we noticed a intriguing pattern: the Fe 25 Al 78 Si 20 structure is based on a primitive cubic lattice similar to the Si-sublattices of the fluorite-type structures of CoSi 2 and NiSi 2 . , However, this pattern is interrupted by inclusions of the fcc structure, a theme noted earlier by Häussermann et al in the V 8 Ga 41 structure type …”

Section: Introductionmentioning

confidence: 77%

Fragmentation of the Fluorite Type in Fe₈Al_17.4Si_7.6: Structural Complexity in Intermetallics Dictated by the 18 Electron Rule

Fredrickson

2012

Inorg. Chem.

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This Article presents the synthesis, structure determination, and bonding analysis of Fe(8)Al(17.4)Si(7.6). Fe(8)Al(17.4)Si(7.6) crystallizes in a new monoclinic structure type based on columns of the fluorite (CaF(2)) structure type. As such, the compound can be seen as part of a structural series in which the fluorite structure-adopted by several transition metal disilicides (TMSi(2))-is fragmented by the incorporation of Al. Electronic structure analysis using density functional theory (DFT) and DFT-calibrated Hückel calculations indicates that the fluorite-type TMSi(2) phases (TM = Co, Ni) exhibit density of states (DOS) pseudogaps near their Fermi energies. An analogous pseudogap occurs for Fe(8)Al(17.4)Si(7.6), revealing that its complex structure serves to preserve this stabilizing feature of the electronic structure. Pursuing the origins of these pseudogaps leads to a simple picture: the DOS minimum in the TMSi(2) structures arises via a bonding scheme analogous to those of 18 electron transition metal complexes. Replacement of Si with Al leads to the necessity of increasing the (Si/Al):TM ratio to maintain this valence electron concentration. The excess Si/Al atoms are accommodated through the fragmentation of the fluorite type. The resulting picture highlights how the elucidating power of bonding concepts from transition metal complexes can extend into the intermetallic realm.

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“…For (I), (III) and (V), queries for structures with the Pearson symbols oS250-254, oP200-204 and oS88, respectively, were made, but no entries for isotypic crystals were found. For (II), a query for hR41 was made, and three nearly identical structures (ICSD 99169; Sugiyama et al, 2004;ICSD 423182, 423183;Roger et al, 2011) of the crystal �Fe 9 (Al,Si) 32 were found. Although isotypism is indicated between (II) and �Fe 9 (Al,Si) 32 , unlike in (II), the centres of the cuboctahedra are not occupied solely by transition-metal atoms in these structures.…”

Section: Database Surveymentioning

confidence: 99%

Crystal structures of five compounds in the aluminium–ruthenium–silicon system

Kitahara,

Takakura,

Iwasaki

et al. 2023

Acta Cryst E

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Single crystals of five compounds with approximate compositions ∼Ru16(Al0.78Si0.22)47, (I), ∼Ru9(Al0.70Si0.30)32, (II), ∼Ru10(Al0.67Si0.33)41, (III), ∼Ru(Al0.57Si0.43)5, (IV), and ∼Ru2(Al0.46Si0.54)9, (V), were obtained from polycrystalline lumps mainly composed of the target compounds, and their crystal structures were determined by means of single-crystal X-ray diffraction. The crystal structure of (I) can be related to that of a cubic rational crystalline approximant to an icosahedral quasicrystal through crystallographic shear and then unit-cell twinning. The crystal structure of (II) is isotypic with that of a phase with composition ∼Fe9(Al,Si)32. The crystal structure of (III) is comprised of edge-sharing Ru(Al,Si)9–11 polyhedra with disordered chains along edges of polyhedra. The crystal structure of (IV) is of the LiIrSn4 type. The crystal structure of (V) can be viewed as a crystallographic shear structure derived from that of (IV).

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Crystal structure of rhombohedral λ-AlFeSi

Cited by 10 publications

References 18 publications

Raman Spectroscopic Analysis of the Reaction between Al-Si Coatings and Steel

Raman Spectroscopic Analysis of the Reaction between Al-Si Coatings and Steel

Fragmentation of the Fluorite Type in Fe₈Al_17.4Si_7.6: Structural Complexity in Intermetallics Dictated by the 18 Electron Rule

Crystal structures of five compounds in the aluminium–ruthenium–silicon system

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Crystal structure of rhombohedral λ-AlFeSi

Cited by 10 publications

References 18 publications

Raman Spectroscopic Analysis of the Reaction between Al-Si Coatings and Steel

Raman Spectroscopic Analysis of the Reaction between Al-Si Coatings and Steel

Fragmentation of the Fluorite Type in Fe8Al17.4Si7.6: Structural Complexity in Intermetallics Dictated by the 18 Electron Rule

Crystal structures of five compounds in the aluminium–ruthenium–silicon system

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Fragmentation of the Fluorite Type in Fe₈Al_17.4Si_7.6: Structural Complexity in Intermetallics Dictated by the 18 Electron Rule