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.