Frontiers in Solidification Science VIII: Convection & Gravity
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 2:00 PM
March 15, 2021
Room: RM 56
Location: TMS2021 Virtual
Session Chair: Sven Eckert, Helmholtz-Zentrum Dresden-Rossendorf; Nana Ofori-Opoku, Canadian Nuclear Laboratories; Christoph Beckermann, University of Iowa; Tiberiu Stan, Northwestern University
2:00 PM Invited
Permeability Prediction of Dendritic Mushy Zone by Phase-field and Lattice Boltzmann Simulations: Tomohiro Takaki1; 1Kyoto Institute of Technology
Permeability, which is a measure of how easily a liquid can flow through a mushy region, is animportant parameter to introduce the information of solidification microstructures into the macroscale casting simulations. Although, over the past half century, many studies have been conducted to predict the permeability of dendritic mushy zone, a definite method, enabling permeability prediction for various dendritic morphologies, has not been established. Recently, we have developed a permeability prediction method by bridging the phase-field and lattice Boltzmann simulations [Acta Mater. 164 (2019) 237-249]. The most distinctive point of this method is utilizing the high-performance computing; we can compute the permeability for realistic dendritic structures. Using this method, we enabled the permeability prediction for liquid flow in the all directions of single-crystal columnar structures [Acta Mater. 188 (2020) 282-287]. Also, the permeability tensor for the columnar structure was developed.
2:30 PM
Multiscale Modeling of Alloy Dendritic Growth with Liquid Convection: Thomas Isensee1; Damien Tourret2; 1IMDEA Materials Institute & Polytechnic University of Madrid; 2IMDEA Materials Institute
The dendritic needle network (DNN) model is designed to bridge the scale gap between phase-field simulations at the scale of individual dendrites and coarse-grained simulations at the scale of entire grain structures. Because melt flow dynamics is in many cases inevitable (e.g. through gravity-induced buoyancy) and plays a crucial role in dendritic pattern formation, the model was recently extended to account for convective transport in the liquid, in both two and three dimensions. Here, we present the latest developments in the DNN modeling approach coupled to fluid flow, and illustrate its potential with two applications: (1) isothermal equiaxed growth within a forced flow to study the effect of dendrite orientation with respect to the flow direction, and (2) directional solidification under natural convection to study the effect of buoyant flow on columnar dendritic array selection.
2:50 PM Invited
Coupling of Solidification Grain Structures with Heat and Mass Transfers: Charles-Andre Gandin1; Vincent Maguin1; Gildas Guillemot1; Chengdan Xue1; Michel Bellet1; Romain Fleurisson1; Yijian Wu1; Orianne Senninger1; 1MINES ParisTech CEMEF UMR CNRS 7635
Modeling of solidification microstructures requires strong coupling with heat and mass transfers. This is an obvious assertion that is not sufficiently put into force. Instead, simple chaining methodologies are usually preferred. The role of coupling will be demonstrated considering several configurations of a cellular automaton – finite element model. When a large temperature gradient applies, e.g. during welding, the role of Marangoni convection on the transport of heat to determine the melt pool shape will be shown. The role of both heat and solute mass by natural convection on the formation of freckles will also be illustrated upon directional solidification of a turbine blade geometry. Finally, upon equiaxed solidification, recalescence obviously proves the importance of coupling with heat and mass transfers upon the development of the grain structure.
3:20 PM
Understanding the Role of Magnetic Fields on Freckle Formation during Solidification through In Situ Imaging: Xianqiang Fan1; Natalia Shevchenko2; Samuel Clark1; Sebastian Marussi1; Saurabh Shah1; Robert Atwood3; Sven Eckert2; Andrew Kao4; Peter Lee1; 1University College London; 2Helmholtz-Zentrum Dresden-Rossendorf; 3Diamond Light Source; 4University of Greenwich
During directional solidification, segregation of alloying components may lead to channels of segregate forming, called ‘freckle’. This work aims to understand how the application of a magnetic field effects freckle formation. Using synchrotron X-ray imaging we quantify the influence of magnetic field strength and orientation on the formation, growth and motion of freckle channels and the resulting suppression of the solidification temperature. By increasing the Bz magnetic component (perpendicular to the sample surface), freckle channels can be driven to one side and suppressed elsewhere, giving a freckle free region in otherwise difficult to cast alloys. The freckle motion can be attributed to the thermoelectric Lorentz force acting on the liquid, changing inter-dendritic liquid flow by causing the solute-enriched liquid to accumulate at one side, biasing channel motion. In the bulk liquid electromagnetic damping force prevails, decreasing the solidification temperature.
3:40 PM Invited
Solidification and Fluid Convection - The Story of an Inseparable Couple: Sten Anders1; Natalia Shevchenko1; Andrew Kao2; Sven Eckert1; 1Helmholtz-Zentrum Dresden-Rossendorf; 2University of Greenwich
In numerous processes in nature and technology, convection is caused by density differences resulting from temperature and concentration gradients. If the rates of diffusion of the two variables differ, this is called double-diffusive convection. Solidification processes under the influence of gravitational forces almost always occur in combination with convective flows. In nature, double-diffusive convection is responsible for magma flow in the mantle of planets or occurs during freezing of seawater. Thermo-solutal convection in industrial castings may result in a composition variation over distances comparable to the size of the solidification domain due to transport of rejected solute by fluid flow, the phenomenon being known as macrosegregation. This paper is dedicated to the interplay between solidification and convection, which are usually closely coupled, interacting in many different ways and thus can lead to very complex phenomena. Results from various experiments conducted both in metals and transparent analogues are presented and discussed.
4:10 PM
Directional Solidification of Al-10wt.%Cu Alloy in Hypergravity: Ali Jafarizadeh1; Sonja Steinbach1; Florian Kargl1; 1German Aerospace Center, Institute of Materials Physics in Space
Many studies have investigated the effect of external fields (electric currents, magnetic and ultrasonic fields) on the solidification structures in castings. In contrast, research on the effect of hypergravity fields as in centrifugal casting is lacking. Although some researchers have looked into the impact of supergravity fields or centrifugal fields on refining the as-cast structures, the effect of hypergravity on directionally solidified microstructures is not understood.Therefore at DLR, a new furnace is built up, and the first experiments are performed with Al-10wt.%Cu alloys directionally solidified at different gravity levels on a centrifuge. The samples solidified in hypergravity are evaluated regarding the processing parameters and the primary dendrite spacing. The results are compared with the microstructure from lab in-situ experiments at 1g and accepted steady-state growth models. This will be an important step towards a better theoretical understanding of the influence of hypergravity on the microstructure formation.
4:30 PM
A Comparison of Terrestrial and Microgravity Isothermal Equiaxed Alloy Solidification through Machine Learning, Multi-stage Thresholding and Sub-dendrite-based In Situ X-ray Video Processing: Jonathan Mullen1; Mert Celikin1; Pádraig Cunningham1; David Browne1; 1University College Dublin
The in-situ observation of growing dendrites via X-Ray videos can be used to study alloy solidification under different gravitational conditions. However, due to the constraints involved with conducting data acquisition on-board microgravity flights, the resulting videos can suffer from a number of imaging issues which make automated assessment difficult and susceptible to errors. High levels of noise and variable amounts of blurring linked to the effective shutter speed, both within and between frames, can lead to measurement difficulties and inaccuracies when using non-specialised automated techniques. Our approach uses a combination of machine learning, multi-stage thresholding and sub-dendrite-based processing to automatically quantify the growth and motion of the individual dendrites observed in the spatially isothermal, equiaxed solidification of a thin Al-20wt%Cu alloy in the XRMON-SOL furnace, both on the ground and in near-zero gravity conditions on board the Maser 13 sounding rocket.