Dendrite growth morphologies in aluminium alloys

Henry, S.; Minghetti, T.; Rappaz, M.

doi:10.1016/s1359-6454(98)00308-5

Cited by 118 publications

(98 citation statements)

References 12 publications

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“…They are considered as defects (or undesirable microstructures), due to their strongly anisotropic properties [1,2]. Using electron backscatter diffraction (EBSD), Henry et al [3][4][5][6] clearly identified the crystallographic relationships of such growth morphologies: a feathery grain is made of a series of alternated twinned and untwinned lamellae, separated by coherent-straight and incoherent-wavy twin boundaries (see Fig. 1).…”

Section: Introductionmentioning

confidence: 99%

Influence of Cr on the nucleation of primary Al and formation of twinned dendrites in Al–Zn–Cr alloys: Can icosahedral solid clusters play a role?

2013

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The equiaxed solidification of Al-20 wt.% Zn alloys revealed an unexpectedly large number of fine grains which are in a twin, or neartwin, relationship with their nearest neighbors when minute amounts of Cr (1000 ppm) are added to the melt. Several occurrences of neighboring grains sharing a nearly common h1 1 0i direction with a fivefold symmetry multi-twinning relationship have been found. These findings are a very strong indication that the primary face-centered cubic Al phase forms on either icosahedron quasicrystals or nuclei of the parent stable Al 45 Cr 7 phase, which exhibits several fivefold symmetry building blocks in its large monoclinic unit cell. They are further supported by thermodynamic calculations and by grains sometimes exhibiting orientations compatible with the socalled interlocked icosahedron. These results are important, not only because they provide an explanation of the nucleation of twinned dendrites in Al alloys, a topic that has remained unclear over the past 60 years despite several recent investigations, but also because they identify a so far neglected nucleation mechanism in aluminum alloys, which could also apply to other metallic systems.

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Section: Introductionmentioning

confidence: 99%

Influence of Cr on the nucleation of primary Al and formation of twinned dendrites in Al–Zn–Cr alloys: Can icosahedral solid clusters play a role?

2013

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“…[1][2][3][4][5] Once nucleated, they rapidly overgrow columnar dendrites and even sometimes regular equiaxed dendrites. [6][7][8] Despite numerous studies which have contributed to the understanding of such morphologies since the first observations of Herenguel, [1,9] more than 60 years ago, many open questions remain.…”

Section: Introductionmentioning

confidence: 99%

“…Optical and electronic microscopy observations combined with EBSD and EDX measurements made over the past fifteen years on such microstructures [6,7,10,11] have shown that (1) The primary trunks of twinned dendrites grow along h110i directions and are split in their centers by a straight boundary that corresponds to a coherent {111} twin plane; (2) Secondary arms grow not only along h110i but also sometimes along h100i directions and meet at wavy-like {111} incoherent boundaries; (3) These growth mechanisms create an alternated sequence of twinned and untwinned lamellae, separated by a sequence of coherent/planar and incoherent/wavy twin boundaries.…”

Section: Introductionmentioning

confidence: 99%

Morphology and Growth Kinetic Advantage of Quenched Twinned Dendrites in Al-Zn Alloys

Salgado-Ordorica

Phillion

Rappaz

2013

Metall Mater Trans A

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Twinned dendrites appearing in an Al-26 wt pct Zn alloy have been quenched during growth using a specifically designed setup that is positioned on top of a directional solidification experiment. X-ray tomography performed at the Swiss Light Source (SLS-beamline TOMCAT) allowed us to reconstruct the 3D morphology of these structures and to confirm previous observations performed on single 2D sections (Henry et al., Metall Mater Trans A 35A:2495-2501 Salgado-Ordorica and Rappaz, Acta Mater 56:5708-5718, 2008). Further characterization of these quenched specimens led to a better description of the mechanisms involved in the in-plane and lateral growth propagation of twinned dendrites. These were then put into relation with the competition mechanisms taking place during simultaneous solidification of twinned and regular dendrites.

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“…This theory falls short of predicting a host of other directions that have been observed experimentally, ranging from early observations of 2245 directions off the basal plane and the c axis in Mg alloys with hexagonal crystal symmetry 33,34 as well as 110 and 111 directions for ammonium chloride in aqueous solutions 35 , to more recent observations of 110 , 320 , 211 , and even unsteady curvilinear dendrite paths in face-centred cubic (f.c.c.) Al-based alloys [36][37][38][39][40][41] . These observations raise the question of what the fundamental relationship between dendrite growth directions and the underlying crystal symmetry is.…”

mentioning

confidence: 99%

“…Therefore, it is natural to hypothesize that the change of anisotropy parameters resulting from solute addition is the underlying mechanism for atypical dendrite growth directions observed in some f.c.c. metallic alloys [36][37][38][39][40][41] . This seems likely because only small changes are necessary to shift the anisotropy parameters either above or below this boundary.…”

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confidence: 99%

Orientation selection in dendritic evolution

et al. 2006

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D endritic alloy microstructures are formed during a wide range of solidification processes from casting to welding. These microstructures result from a morphological instability of the solid-liquid interface that produces dendrites, which are highly hierarchical branched patterns with primary-, secondary-and higher-order branches. As alloy impurities segregate in the interdendritic liquid during solidification, the spatially inhomogeneous distribution of impurities in the completely solidified alloy is a direct footprint of the dendritic network that formed and coarsened during the solidification process. It also determines the formation and distribution of secondary phases, and thus has a profound influence on the properties of a wide range of technologically important structural materials, from light-weight aluminium alloys used in the automotive industry to nickel-based superalloys used for turbine blades. The study of dendritic growth 1,2 has also been of long-standing fundamental interest because of the ubiquity of branched structures exhibited by diverse interfacial pattern formation systems [3][4][5] .Major theoretical and computational advances over the past two decades have improved our fundamental understanding of dendrite growth, as well as new capabilities to simulate and predict dendritic microstructures on experimentally relevant length and timescales 6 and to elucidate new pattern formation mechanisms 7,8 that enlarge the scope of our understanding of these structures. The commonly accepted microscopic solvability theory of steadystate dendrite growth 9-12 , which builds on the earlier diffusive transport theory of Ivantsov 13 , has led to the understanding that crystalline anisotropy is a crucial parameter that uniquely determines the growth rate and tip radius of dendrites, which is the basic scaling length for the entire dendritic network. Predictions of this theory have been largely validated by phase-field simulations of dendritic evolution over the past few years for both small [14][15][16][17][18][19] and large 20 growth rate. Moreover, molecular dynamics (MD) simulation methods [21][22][23][24][25][26][27][28][29][30] as well as experimental techniques 31,32 have recently been developed to accurately compute anisotropic interfacial properties that control dendritic evolution.Despite this progress, dendrite growth theory remains limited to predicting the steady-state characteristics of dendrites growing along simple crystallographic directions, such as the 100 directions that correspond to the main crystal axes for materials with cubic symmetry, or the six directions in the basal plane of

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Dendrite growth morphologies in aluminium alloys

Cited by 118 publications

References 12 publications

Influence of Cr on the nucleation of primary Al and formation of twinned dendrites in Al–Zn–Cr alloys: Can icosahedral solid clusters play a role?

Influence of Cr on the nucleation of primary Al and formation of twinned dendrites in Al–Zn–Cr alloys: Can icosahedral solid clusters play a role?

Morphology and Growth Kinetic Advantage of Quenched Twinned Dendrites in Al-Zn Alloys

Orientation selection in dendritic evolution

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