Frontiers in Solidification Science VIII: Dendritic Growth
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Chemistry and Physics of Materials Committee, TMS: Phase Transformations Committee, TMS: Solidification Committee, TMS: Computational Materials Science and Engineering Committee
Program Organizers: Damien Tourret, IMDEA Materials Institute; Amy Clarke, Los Alamos National Laboratory; Ulrike Hecht, Access e.V.; Nana Ofori-Opoku, Canadian Nuclear Laboratories; Melis Serefoglu, Marmara University; Tiberiu Stan, Asml
Monday 8:30 AM
March 15, 2021
Room: RM 56
Location: TMS2021 Virtual
Session Chair: Charles-Andre Gandin, MINES ParisTech CEMEF UMR CNRS 7635; Damien Tourret, IMDEA Materials; Tomohiro Takaki, Kyoto Institute of Technology; Amy Clarke, Colorado School of Mines
8:30 AM
Introductory Comments: Frontiers in Solidification Science VIII: Damien Tourret1; 1IMDEA Materials
Introductory Comments
8:35 AM Invited
In-situ Measurement of Dendrite Tip Shape in a Metallic Alloy: Christoph Beckermann1; H. Neumann-Heyme2; N. Shevchenko2; J. Grenzer2; S. Eckert2; 1University of Iowa; 2Helmholtz-Zentrum Dresden-Rossendorf (HZDR)
The size and shape of the primary dendrite tips determine the principal length scale of the microstructure evolving during solidification of alloys. In-situ measurements of the tip shape in metals have been unsuccessful so far due to insufficient spatial resolution or high image noise. Here we report on quantitative in-situ measurements of the geometry of dendrite tips in a thin sample of a directionally solidifying Ga-35wt.%In alloy. The measurements are based on a combination of high-resolution synchrotron radiography and advanced image processing techniques. Dendrite tips are observed during the fast initial transient and the subsequent steady growth period, with tip velocities ranging over almost two orders of magnitude. The dendrite tip shape selection parameter is measured to be σ≈0.075, suggesting a somewhat higher interface energy anisotropy than in aluminum alloys. The non-axisymmetric shape amplitude is found to be A_4≈0.004, which is in agreement with the universal value previously established.
9:05 AM
Microstructural Evolution in Metallic Alloys during Solidification: Tiberiu Stan1; Peter Voorhees1; 1Northwestern University
Many thermo-mechanical properties of metallic alloys are controlled by the microstructures left behind after solidification. We use time-resolved x-ray computed tomography (XCT) and serial sectioning to provide insights into solidification processes. The XCT datasets are reconstructed using TIMBIR to achieve high spatial (0.55 micron) and temporal (0.25 second) resolutions, and segmented using a variety of convolutional neural network machine learning architectures. The resulting 3D and 4D experiments give new insights into the evolution of dendritic morphologies, tip radii, crystallographic growth directions, and interfacial curvatures. Unlike dendrites in Al-Cu which have primary and secondary branches, we show that free-growing dendrites in Al-Zn alloys are hyperbranched and approximately self-similar during growth. We also capture dendrite arm fragmentation events and subsequent motion both with and against gravity, largely due to changes in solid and liquid densities.
9:25 AM
Shapes of Dendritic Tips at Small and Large Undercoolings: Andrew Kao1; Liubov Toropova2; Dmitri Alexandrov2; Peter Galenko3; 1University of Greenwich; 2Ural Federation University; 3Friedrich Schiller University Jena
This paper investigates the shapes of dendritic tips occurring in undercooled pure systems in the absence of convection. Analytical treatment shows, circular/globular shape appears in limiting cases of small and large Péclet numbers. A parabolic/paraboloidal shape describes the tip regions of dendrites whereas a fractional power law defines a shape behind their tips in the case of low/moderate Péclet number. The parabolic/paraboloidal and fractional power law shapes are sewed together in the present work to describe the dendritic shape in a broader region adjacent to the dendritic tip. Such a generalised law is in good agreement with the parabolic/paraboloidal and fractional power laws of dendritic shapes. A special case of the angled dendrite is considered and analysed in addition. Using the enthalpy method for numerical solutions we test and compare analytical results with the data of computational modelling on dendritic growth in pure undercooled liquids.
9:45 AM
A Model for Dendrite Fragmentation in Alloy Solidification: Hieram Neumann-Heyme1; Kerstin Eckert1; Christoph Beckermann2; 1Helmholtz-Zentrum Dresden-Rossendorf (HZDR); 2University of Iowa
The quantitative prediction of dendrite fragmentation has remained a major issue in the modeling of solidification processes. A model is proposed that predicts detachment of dendritic sidebranches by linking the local dynamics of the collapsing necks of sidebranches to global solidification parameters. Validation of the model is carried out by careful analysis of existing data from in-situ x-ray imaging experiments. Although the basic model operates on the assumption of purely diffusive transport, flow effects and other important contributions can be be incorporated into the model in an efficient way.
10:05 AM
Dendritic Spacing Selection during Al-Cu Casting: Experiments and Multiscale Simulations: Barbara Bellon1; Ahmed Boukellal2; Thomas Isensee1; John Coleman3; Matthew Krane3; Michael Titus3; Damien Tourret2; Javier Llorca4; 1IMDEA Materials Institute & Polytechnic University of Madrid; 2IMDEA Materials Institute; 3Purdue University; 4IMDEA Materials Institute & Technical University of Madrid
Dendrite arm spacings have a strong effect on the mechanical properties of cast microstructures. Spacing selection during solidification can be simulated using phase-field. However, three-dimensional quantitative simulations are challenging, in particular for non-dilute alloys, due to the wide separation of scale between dendritic tips and diffusion. For this reason: (1) comparisons of simulations and experiments have mostly focused on thin-sample experiments of dilute alloys and (2) in practice, spacings are typically estimated using phenomenological power laws of the process and alloy parameters. Here, we use phase-field simulations for dilute alloys, and extend them to higher concentrations using a dendritic needle network approach, in order to predict primary spacings in Al-Cu alloys. We compare simulation results to measurements from casting experiments and literature data, and show that this multiscale approach can provide a quantitative predictions of local microstructure length scales in bulk samples solidified under realistic casting conditions.
10:25 AM
Characterization of Dendritic Spatially Extended 3D Patterns in Directional Solidification: Microgravity Experiments in DECLIC-DSI Onboard ISS and 3D Phase-field Simulations: Kaihua Ji1; Fatima Mota2; Louise Strutzenberg3; Rohit Trivedi4; Nathalie Bergeon2; Alain Karma1; 1Northeastern University; 2Aix-Marseille Université; 3NASA Marshall Space Flight Center; 4Iowa State University
To clarify and characterize the fundamental physical mechanisms active in the dynamical formation of three-dimensional (3D) arrays of dendrites under diffusive growth conditions, in situ monitoring of series of experiments on transparent model alloy succinonitrile – 0.46 wt% camphor was carried out under low gravity in the DECLIC Directional Solidification Insert onboard the International Space Station. These experiments offer the very unique opportunity to observe in situ and characterize the dynamics of the microstructure formation and evolution in extended 3D patterns under microgravity environment. The analyses of the dendritic patterns for a broad range of growth velocities displaying different levels of sidebranching will be presented. Especially, the time evolution of primary spacing, in case of solidifications at constant pulling rate as well as for experiments with pulling rate jump, will be compared to 3D phase-field simulations, and the results will be discussed in terms of stable spacing range.
10:45 AM
Comparison of Solidification Characteristics of In-situ X-radiography Experiments and DNN Simulations: Maike Becker1; Laszlo Sturz2; Dirk Bräuer1; Florian Kargl1; 1German Aerospace Center (DLR); 2Access e.V.
We use a combination of experimental analysis and dendrite needle network (DNN) computation to compare the measured and simulated solidification characteristics in a thin Al-Ge alloy. Dendrite tip growth velocities and concentration fields are extracted from in situ X-radiography experiments. We find one parameter set to accurately reproduce all experimentally measured solidification characteristics with the three-dimensional DNN model. It is the first study, which quantitatively compares equiaxed dendritic growth velocities, concentration fields and solid fractions. We use the experimental analysis and a previous phase-field simulation to approximate certain unknown model parameters (initial undercooling, selection constant) and additionally perform a DNN parameter study to eventually find the best fitting parameters. Furthermore, we explore the role of the thin sample geometry. We find that it has a great influence on the solidification characteristics when the undercooling in the system is small (< 15 K).
11:05 AM
Grain Competition in Polycrystalline Columnar Dendritic Solidification: Scale Bridging between Phase Field and Cellular Automaton Methods: Elaheh Dorari1; Kaihua Ji1; Gildas Guillemot2; Charles-Andre Gandin2; Alain Karma1; 1Northeastern University; 2MINES ParisTech
The growth competition amongst different grains during dendritic solidification has a crucial influence on the final microstructure, material properties and performance of the cast parts. A quantitative understanding of the dynamical selection of the grain boundary (GB) orientation during polycrystalline dendritic growth is still lacking. In this study, we present a comprehensive phase-field (PF) investigation of columnar dendritic grain competition in a succinonitrile-1.3 wt% acetone sample in two dimensions. The PF model of alloy solidification exploits a novel rotationally invariant finite-difference scheme of the anti-trapping current to accurately resolve the dendrite tip operating state of misoriented grains. We discuss the combined role of the temperature gradient and the grain orientations in the selection of GB orientation. Comparison with Cellular Automaton results derived under the same conditions as well as different GB selection criteria are performed, and the pertinence of the CA method for predicting the GB selection is discussed.
11:25 AM
Interaction of Hydrogen-bubbles with the Approaching Solidification Front in Al-Cu Melt - An In-situ Study: Thomas Werner1; Juliane Baumann1; Maike Becker1; Christoph Pickmann2; Laszlo Sturz2; Florian Kargl1; 1German Aerospace Center (DLR) - Institute of Materials Physics in Space; 2ACCESS e.V.
Much research has already been focused on the solid/bubble interaction in the interdendritic space for solidifying materials. However, commonly, bubble-nucleation isn’t limited to the mushy zone, but also appears in the melt in front of the advancing solid/liquid interface in directional solidification. In the present study on an Al - 10%wt. Cu alloy, the interaction between this type of bubbles and the approaching solidification front becomes apparent under in-situ X-ray radiography observation and allows for new insights on the influence of bubbles on the solidifying microstructure. The observed effects comprise bulging of the solidification front towards the bubbles, bending of dendrites in front of the bubbles, coronal outgrowths surrounding the bubbles, as well as bubble-growth, -pushing, and -eruption.