Oscillatory growth of directionally solidified ammonium chloride dendrites

Gudgel, Katherine A.; Jackson, K. A.

doi:10.1016/s0022-0248(01)00847-8

Cited by 24 publications

(11 citation statements)

References 19 publications

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“…This eliminates the contribution of attachment kinetics anisotropy in the present experiments, thus supporting a continuous change of steady-state dendrite orientation dictated only by the surface energy anisotropy variation, as in the phasefield simulations. This is in contrast to other DS experiments where abrupt velocity-dependent transitions between slow 100 and fast 111 growth modes have been related to the anisotropic departure from local chemical equilibrium at the solid-liquid interface for ammonium chloride dendrites 44 . For concentrations between 25 and 55 wt% Zn, the misorientation of the dendrite trunks continuously increases from 0 to 45 • .…”

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confidence: 81%

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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confidence: 81%

Orientation selection in dendritic evolution

et al. 2006

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“…In fact the co-existence of mixed secondary branches which are both symmetrical and non-symmetrical, and either periodic or erratic, were observed on the same dendrite. Further studies into the NH 4 Cl-H 2 O system show that developing dendrites will transition from slow <100> to fast <111> type growth when there is a significant drop in interface temperature [20]. Similar observations have been made in Cu-Sn alloys [21], wherein a transition from <111> to <100> growth was observed above a critical value of undercooling, ∆T'.…”

Section: Introductionsupporting

confidence: 56%

Evidence for an extensive, undercooling-mediated transition in growth orientation, and novel dendritic seaweed microstructures in Cu–8.9wt.% Ni

Castle

Mullis

2014

Acta Materialia

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Paper:Castle, EG, Mullis, AM and Cochrane, RF (2013) Evidence for an extensive, undercooling-mediated transition in growth orientation, and novel dendritic seaweed microstructures in 8-fold growth at low undercooling whilst <111> character begins to dominate at high undercooling, accompanied by a switch to 6-fold growth. It is believed that this range of undercooling represents an extended transition between fully <100> oriented growth at low undercooling and fully <111> oriented growth at high undercooling. It is suggested that an observed positive break in the velocity-undercooling relationship at high undercooling is therefore coincident with the transition to fully <111> growth, though this could not be confirmed microstructurally. The existence of competing anisotropies in the growth directions at intermediate undercoolings appears to be giving rise to a novel form of the dendritic seaweed structure, characterised by its containment within a diverging split primary dendrite branch. In addition, at the highest undercoolings achieved, an equiaxed-to-elongated grain structure is observed, in which an underlying dendritic seaweed substructure exists. We suggest that this structure may be an intermediate in the spontaneous grain refinement phenomenon, in which case dendritic seaweed appears to play some part.

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“…However, a number of cubic systems have been shown to undergo a change in growth direction from Ͻ100Ͼ through Ͻ110Ͼ to Ͻ111Ͼ as the growth velocity is increased and, in particular, this has been observed in situ in the transparent NH 4 Cl-H 2 O system. [1] It has been suggested that this type of behavior is due to a competition between the surfaceenergy anisotropy, which favors Ͻ100Ͼ growth at low velocity, and the kinetic anisotropy, which favors Ͻ111Ͼ growth at high velocity. [2] Such phenomena have also been observed in viscous fingering in Hele-Shaw cells.…”

Section: Introductionmentioning

confidence: 99%

The solidification of undercooled melts via twinned dendritic growth

Dragnevski

Mullis

2004

Metall Mater Trans A

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The solidification of undercooled Cu-x wt pct Sn (x ϭ 1, 2, 3, or 4) alloys has been studied by a meltencasement (fluxing) technique. It was found that below undercoolings of ⌬T Ϸ 90 K, the preferred dendrite growth orientation in each of these alloys was along the Ͻ111Ͼ direction: moreover, the 2 and 3 wt pct Sn alloys also displayed evidence of twinned growth. Above ⌬T Ϸ 90 K, the preferred growth direction returned to the more usual Ͻ100Ͼ orientation.

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Oscillatory growth of directionally solidified ammonium chloride dendrites

Cited by 24 publications

References 19 publications

Orientation selection in dendritic evolution

Orientation selection in dendritic evolution

Evidence for an extensive, undercooling-mediated transition in growth orientation, and novel dendritic seaweed microstructures in Cu–8.9wt.% Ni

The solidification of undercooled melts via twinned dendritic growth

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