Spacing characterization in Al–Cu alloys directionally solidified under transient growth conditions

Amoorezaei, Morteza; Gurevich, S. M.; Provatas, Nikolas

doi:10.1016/j.actamat.2010.07.029

Cited by 66 publications

(31 citation statements)

References 19 publications

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“…A logical test of the phase-field theory would be to calculate the so-called "pinch-off time" for the filaments here, that is, the time it takes for a Rayleigh instability in the filament to amplify and cause the filament diameter to reduce to zero locally [41] . This class of topological singularity has been the subject of recent theoretical interest [42] , and a framework has been developed allowing pinch-off to be predicted, verified through measurements of the µm-scale evolution of dilute binary alloys using x-ray tomography [43] .…”

Section: Cellular Breakdown Dynamicsmentioning

confidence: 99%

Single‐Phase Filamentary Cellular Breakdown Via Laser‐Induced Solute Segregation

Akey

Recht

Williams

et al. 2015

Adv Funct Materials

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Nanosecond melting and quenching of materials offers a pathway to novel structures with unusual properties. Impurity-rich silicon processed using nanosecond-pulsed-laser-melting is known to produce nanoscale features in a process referred to as "cellular breakdown" due to destabilization of the planar liquid/solid interface. Here, we apply atom probe tomography combined with electron microscopy to show that the morphology of cellular breakdown in these materials is significantly more complex than previously documented. We observe breakdown into a complex, branching filamentary structure topped by a few nm of a cell-like layer. Singlephase diamond cubic silicon highly supersaturated with at least 10% atomic Co and no detectable silicides is reported within these filaments. In addition, the unprecedented spatio-chemical accuracy of the atom probe allows us to investigate nanosecond formation dynamics of this 2 complex material. Previously-reported properties of these materials can now be reconsidered in light of their true composition, and this class of inhomogeneous metastable alloys in silicon can be explored with confidence.

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Section: Cellular Breakdown Dynamicsmentioning

confidence: 99%

Single‐Phase Filamentary Cellular Breakdown Via Laser‐Induced Solute Segregation

Akey

Recht

Williams

et al. 2015

Adv Funct Materials

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“…25 Phase-field simulations are thus capable of predicting stable dendritic spacing ranges in the steady state, 14,[26][27][28] as well as the dynamical selection of spacings by elimination during the transient stage of solidification. [28][29][30] Recent PF studies have also shown that, in polycrystalline columnar growth, the dynamical evolution of dendritic spacing at converging grain boundaries is closely linked to the unusual overgrowth mechanism of a favorably oriented grain. 16,31,32 While PF remains the method of choice for simulation of dilute alloy solidification, quantitative predictions of dendritic growth dynamics with PF require an accurate morphological description of each dendrite tip.…”

Section: Introductionmentioning

confidence: 99%

Three-Dimensional Multiscale Modeling of Dendritic Spacing Selection During Al-Si Directional Solidification

Tourret

Clarke

Imhoff

et al. 2015

JOM

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We present a three-dimensional extension of the multiscale dendritic needle network (DNN) model. This approach enables quantitative simulations of the unsteady dynamics of complex hierarchical networks in spatially extended dendritic arrays. We apply the model to directional solidification of Al-9.8 wt.%Si alloy and directly compare the model predictions with measurements from experiments with in situ x-ray imaging. We focus on the dynamical selection of primary spacings over a range of growth velocities, and the influence of sample geometry on the selection of spacings. Simulation results show good agreement with experiments. The computationally efficient DNN model opens new avenues for investigating the dynamics of large dendritic arrays at scales relevant to solidification experiments and processes.

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“…The linear growth rate and wavelength selection of cellular flame fronts are examined numerically, validating the recent analytical predictions of Brailovsky et al [24]. In the non-linear regime, we explore the growth of combustion morphologies that vary from cells to seaweed dendrites analogous to those observed in directional solidification [28,29]. This is seen to happen for low Le, a regime separating cellular/dendritic patterns from oscillatory modes prevalent at high Le.…”

Section: Introductionmentioning

confidence: 90%

“…A detailed analysis of spacing selection in the non-linear regime is beyond the scope of this work. Spacing selection in the non-linear regime has a long history in solidification studies [54,55] and while insight can be gained from analyses like the one above, it still represents a largely unsolved problem. front corresponds to isotherm θ(x, y) = θ ig for model parameters MM(n = 1; Le = 0.05; θ ig = 0.75).…”

Section: Effect Of Lewis Number On the Morphologymentioning

confidence: 99%

Analysis of thermodiffusive cellular instabilities in continuum combustion fronts

2017

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We explore numerically the morphological patterns of thermo-diffusive instabilities in combustion fronts with a continuum fuel source, within a range of Lewis numbers and ignition temperatures, focusing on the cellular regime. For this purpose, we generalize the model of Brailovsky et al. to include distinct process kinetics and reactant heterogeneity. The generalized model is derived analytically and validated with other established models in the limit of infinite Lewis number for zero-order and first-order kinetics. Cellular and dendritic instabilities are found at low Lewis numbers thanks to a dynamic adaptive mesh refinement technique that reduces finite size effects, which can affect or even preclude the emergence of these patterns. This technique also allows achieving very large computational domains, enabling the study of system-size effects. Our numerical linear stability analysis is consistent with the analytical results of Brailovsky et al. The distinct types of dynamics found in the vicinity of the critical Lewis number, ranging from steady-state cells to continued tip-splitting and cell-merging, are well described within the framework of thermo-diffusive instabilities and are consistent with previous numerical studies. These types of dynamics are classified as "quasi-linear" and characterized by low amplitude cells and may follow the mode selection mechanism and growth prescribed by the linear theory. Below this range of Lewis number, highly non-linear effects become prominent and large amplitude, complex cellular and seaweed dendritic morphologies emerge.

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Spacing characterization in Al–Cu alloys directionally solidified under transient growth conditions

Cited by 66 publications

References 19 publications

Single‐Phase Filamentary Cellular Breakdown Via Laser‐Induced Solute Segregation

Single‐Phase Filamentary Cellular Breakdown Via Laser‐Induced Solute Segregation

Three-Dimensional Multiscale Modeling of Dendritic Spacing Selection During Al-Si Directional Solidification

Analysis of thermodiffusive cellular instabilities in continuum combustion fronts

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