Toward a Microgravity Research Strategy (1992) / Chapter Skim
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Appendix F: Metals and Alloys
Appendix F: Metals and Alloys
Pages 47-53
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From page 47... ...
REPORT MENU NOTICE Containerless Science MEMBERSHIP SUMMARY Containerless science deals with experimental and theoretical studies of CHAPTER 1 competitive nucleation and growth kinetics of undercooled systems, especially in CHAPTER 2 the molten state when removed from physical contact with containers. Among CHAPTER 3 such studies are thermophysical measurements, x-ray diffraction, and heat flow CHAPTER 4 modeling to predict and control microstructural development.
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From page 48... ...
A goal of many ground based calculations is to assist investigators in designing equipment and experiments for low-gravity environments. A major area of scientific and technological progress in solidification processing entails the development of quantitative, predictive, microstructural "scaling laws." For dendritic growth under diffusion control, scaling laws predict the growth speed, tip radius, and branch spacing as functions of the material parameters.
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From page 49... ...
Over a range of temperatures below the critical point, one of the liquids exhibits perfect welting behavior so that it essentially encapsulates the other liquid and will coat any container. If final freezing occurs within the temperature range of perfect welting, massive segregation will be produced in the microstructure.
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From page 50... ...
Theoretical modeling is playing an important role in designing useful experiments to be performed in space. RESEARCH PROSPECTS AND OPPORTUNITIES General The future of NASA's microgravity program lies in the continuation of its Spacelab flight program up to and beyond the commissioning of Space Station Freedom, scheduled for the year 2000.
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From page 51... ...
Even quite familiar terrestrial situations transferred to an apparently simple space environment require an extensive development program on Earth with theoretical, numerical, and experimental modeling and an open mind to cope with the unpredictable. For example, current models of the instability at solid and/or liquid interfaces have demonstrated the complexity of this problem and the various methods of treatment.
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From page 52... ...
Also, because electromagnetic levitation is one of the current techniques employed in containerless processing, it is important to assess quantitatively the role played by residual electromagnetic forces in producing convection and the decay rate of such convection. Many metals-processing operations involve the simultaneous transfer of matter and thermal energy and the coupling of other transport phenomena.
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From page 53... ...
Last update 7/13/00 at 4:24 pm Site managed by Anne Simmons, Space Studies Board The National Academies Current Projects Publications Directories Search Site Map Feedback file:///C|/SSB_old_web/cmgr92appendf.htm (7 of 7)
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