Solidification of Containerless Undercooled Melts

All metallic materials are prepared from the liquid state as their parent phase. Solidification is therefore one of the most important phase transformation in daily human life. Solidification is the transition from liquid to solid state of matter. The conditions under which material is transformed determines the physical and chemical properties of the as-solidified body. The processes involved, like nucleation and crystal growth, are governed by heat and mass transport. Convection and undercooling provide additional processing parameters to tune the solidification process and to control solid material performance from the very beginning of the production chain. To develop a predictive capability for efficient materials production the processes involved in solidification have to be understood in detail. This book provides a comprehensive overview of the solidification of metallic melts processed and undercooled in a containerless manner by drop tube, electromagnetic and electrostatic levitation, and experiments in reduced gravity. The experiments are accompanied by model calculations on the influence of thermodynamic and hydrodynamic conditions that control selection of nucleation mechanisms and modify crystal growth development throughout the solidification process.

Table of Contents:
PREFACE CONTAINERLESS UNDERCOOLING OF DROPS AND DROPLETS Introduction Drop Tubes Containerless Processing Through Levitation Summary and Conclusions COMPUTER-AIDED EXPERIMENTS IN CONTAINERLESS PROCESSING OF MATERIALS Introduction Planning Experiments Operating Experiments Data Reduction, Analysis, Visualization, and Interpretation Conclusion DEMIXING OF CU - CO ALLOYS SHOWING A METASTABLE MISCIBILITY GAP Introduction Mechanism of Demixing Demixing Experiments in Terrestrial EML and in Low Gravity Demixing Experiments in a Drop Tube Spinodal Decomposition in Cu - Co Melts Conclusions SHORT-RANGE ORDER IN UNDERCOOLED MELTS Introduction Experiments on the Short-Range Order of Undercooled Melts Conclusions ORDERING AND CRYSTAL NUCLEATION IN UNDERCOOLED MELTS Introduction Nucleation Theory - Some Background Liquid Metal Undercooling Studies Coupling of Ordering in the Liquid to the Nucleation Barrier Conclusions PHASE-FIELD CRYSTAL MODELING OF HOMOGENEOUS AND HETEROGENEOUS CRYSTAL NUCLEATION Introduction Phase-Field Crystal Models Homogeneous Nucleation PFC Modeling of Heterogeneous NuCleation Summary EFFECTS OF TRANSIENT HEAT AND MASS TRANSFER ON COMPETITIVE NUCLEATION AND PHASE SELECTION IN DROP TUBE PROCESSING OF MULTICOMPONENT ALLOYS Introduction Model Effect of Transient Heat and Mass Transfer on Nucleation and Crystal Growth Competitive Nucleation and Phase Selection in Nd - Fe - B Droplets Summary CONTAINERLESS SOLIDIFICATION OF MAGNETIC MATERIALS USING THE ISAS/JAXA 26-METER DROP TUBE Introduction Drop Tube Process Undercooling Solidification of Fe - Rare Earth (RE) Magnetostriction Alloys Undercooling Solidification of Nd - Fe - B Magnet Alloys Concluding Remarks NUCLEATION AND SOLIDIFICATION KINETICS OF METASTABLE PHASES IN UNDERCOOLED MELTS Introduction Thermodynamic Aspects and Nucleation of Metastable Phases Metastable Phase Formation from Undercooled Melts in Various Alloy Systems Summary and Conclusions NUCLEATION WITHIN THE MUSHY ZONE Introduction Incubation Time Cluster Formation Transient Development of Heterogeneous Sites Comparing Critical Nucleus Development Mechanisms Concluding Remarks MEASUREMENTS OF CRYSTAL GROWTH VELOCITIES IN UNDERCOOLED MELTS OF METALS Introduction Experimental Methods Summary and Conclusions CONTAINERLESS CRYSTALLIZATION OF SEMICONDUCTORS Introduction Status of Research on Facetted Dendrite Growth Twin-Related Lateral Growth and Twin-free Continuous Growth Containerless Crystallization of Si Summery and Conclusion Appendix 12.A: LKT Model MEASUREMENTS OF CRYSTAL GROWTH DYNAMICS IN GLASS-FLUXED MELTS Introduction Methods and Experimental Set-Up Growth Velocities in Pure Ni Growth Velocities in Ni3Sn2 Compound Crystal Growth Dynamics in Ni - Sn Eutectic Alloys Opportunities with High Magnetic Fields Summary INFLUENCE OF CONVECTION ON DENDRITE GROWTH BY THE AC - DC LEVITATION TECHNIQUE Convection in a Levitated Melt Static Levitation Using the Alternating and Static Magnetic Field (AC - DC Levitation) Effect of Convection on Nucleation and Solidification MODELING THE FLUID DYNAMICS AND DENDRITIC SOLIDIFICATION IN EM-LEVITATED ALLOY MELTS 321 Introduction Mathematical Models for Levitation Thermofluid Dynamics Thermoelectric Magnetohydrodynamics in Levitated Droplets Concluding Remarks FORCED FLOW EFFECT ON DENDRITIC GROWTH KINETICS IN A BINARY NONISOTHERMAL SYSTEM Introduction Convective Flow in Droplets Processed in Electromagnetic Levitation The Model Equations Predictions of the Model Quantitative Evaluations Summary and Conclusions ATOMISTIC SIMULATIONS OF SOLUTE TRAPPING AND SOLUTE DRAG Introduction Models of Solute Trapping Solute Drag MD Simulations Implications for Dendrite Growth PARTICLE-BASED COMPUTER SIMULATION OF CRYSTAL NUCLEATION AND GROWTH KINETICS IN UNDERCOOLED MELTS Introduction Solid - Liquid Interfaces in Nickel Homogeneous Nucleation in Nickel Crystal Growth Conclusions SOLIDIFICATION MODELING: FROM ELECTROMAGNETIC LEVITATION TO ATOMIZATION PROCESSING Introduction Electromagnetic Levitation Impulse Atomization Modeling EML Sample IA Particles Conclusion PROPERTIES OF P-SI-GE THERMOELECTRICAL MATERIAL SOLIDIFIED FROM UNDERCOOLED MELT LEVITATED BY SIMULTANEOUS IMPOSITION OF STATIC AND ALTERNATING MAGNETIC FIELDS Introduction Simultaneous Imposition of Static and Alternating Magnetic Fields Experimental Results and Discussion Summary and Conclusions QUANTITATIVE ANALYSIS OF ALLOY STRUCTURES SOLIDIFIED UNDER LIMITED DIFFUSION CONDITIONS The Need for an Instrumented Drop Tube Description of IA Powder Characteristics Quantification of Microstructure Modeling COUPLED GROWTH STRUCTURES IN UNIVARIANT AND INVARIANT EUTECTIC SOLIDIFICATION Introduction Historical Perspective and Background Basic Theory of Eutectic Solidification Eutectic Solidification Theory for Ternary Systems Solidification Paths and Competitive Growth Considerations Recent Developments, Emerging Issues, and Critical Research Needs SOLIDIFICATION OF PERITECTIC ALLOYS Introduction Peritectic Equilibrium and Transformation Peritectic Reactions in the Ternary System Nucleation Studies Growth Conclusions

About the Author :
Dieter Herlach is leader of the group "Undercooling of Materials" and Senior Scientist at the Institute of Materials Physics in Space of the German Aerospace Center (DLR) in Cologne. He is full professor of physics at the Ruhr-University Bochum. Dieter Herlach has authored more than 300 scientific publications in refereed journals and organized sixteen conferences and symposia. He is author and editor of six books and member of the advisory board of Advanced Engineering Materials (Wiley-VCH). He was member of the advisory board of directors of the German Physical Society and deputy chairman of the German Society of Materials Science and Engineering. Two priority programs of the German Research Foundation (DFG) and several European projects of the European Space Agency and the European Commission were coordinated by him. He was lead scientist for NASA Spacelab missions IML2 and MSL1 and granted as honorary professor of four Chinese Universities and Research Centers. Douglas M. Matson is Vice Chairman and Associate Professor in the Mechanical Engineering Department at Tufts University, Medford MA, USA. He is an internationally recognized expert with over fifty peer reviewed articles in thermal manufacturing, machine design, materials processing, solidification research, and microgravity experimentation. He has organized five symposium, is the former president of the North Alabama Chapter of the American Society for Materials (ASM) and received an Erskine Fellowship at the University of Canterbury, Christchurch, New Zealand. He has served as lead scientist for the MSL-1 Spacelab mission and currently is the NASA facility scientist for the MSL-EML project aboard the International Space Station.