Materials Science Laboratory - Columnar-to-Equiaxed Transition in Solidification Processing and Microstructure Formation in Casting of Technical Alloys under Diffusive and Magnetically Controlled Convective Conditions (MSL-CETSOL and MICAST) - 04.10.14
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Science Objectives for Everyone The Materials Science Laboratory - Columnar-to-Equiaxed Transition in Solidification Processing and Microstructure Formation in Casting of Technical Alloys under Diffusive and Magnetically Controlled Convective Conditions (MSL-CETSOL and MICAST) are two investigations that support research into metallurgical solidification, semiconductor crystal growth (Bridgman and zone melting), and measurement of thermo-physical properties of materials. This is a cooperative investigation with the European Space Agency and NASA for accommodation and operation aboard the International Space Station.
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This investigation examined different growth patterns and evolution of microstructures during crystallization of metallic alloys to improve understanding of physical principles that govern solidification. When a molten metal or alloy cools and crystallizes, the resulting solid generally has two competing types of grain structures: columnar grains and grains with axes of equal lengths, called equiaxed. These structures play a critical role in the physical properties and behavior of metallic products. Data were used to predict position of columnar-to-equiaxed transition, with reasonably strong agreement between model simulation and experiment. This suggests that transition is related to velocity jump and resulting temperature change.
Developer(s) Project User Group
Snecma - Safran S.A., , , France
Transvalor S.A., , , France
Alcan CRV, Voreppe, , France
Arcelor Research S.A., Paris, , France
GROHNO-Guss GmbH, , , Germany
Project User Group
Hydro Aluminium GmbH, , , Germany
Nemak Hungary, , , Hungary
Alcoa-Köfem Kft, , , Hungary
INOTAL, , , Hungary
Project User Group
Dunaferr Zrt., , , Hungary
MAL Magyar Aluminium Rt., Budapest, , Hungary
Femalk Rt., Budapest, , Hungary
Honeywell International Technologies Ltd., , , Ireland
Aleris, , , Netherlands
Project User Group
CorusTechnology BV, , , Netherlands
European Space Agency (ESA), Noordwijk, , Netherlands
Sponsoring Space Agency
National Aeronautics and Space Administration (NASA)
Human Exploration and Operations Mission Directorate (HEOMD)
ISS Expedition Duration
October 2009 - May 2012
Previous ISS Missions
CETSOL and MICAST hardware are delivered to the ISS during Expedition 18.
- Columnar-to-Equiaxed Transition in Solidification Processing (CETSOL) and Microstructure Formation in Casting of Technical Alloys under Diffusive and Magnetically Controlled Convective Conditions (MICAST) are two investigations which will examine different growth patterns and evolution of microstructures during crystallization of metallic alloys. The aim of these experiments are to deepen the quantitative understanding of the physical principles that govern solidification processes in cast alloys by directional solidification. Microgravity offers a unique opportunity to obtain well-controlled solidification conditions for these alloys.
Aluminum alloys are a standard cast metal used in a number of automotive and transportation applications, allowing manufacturers to reduce vehicle weight, increase the strength of components and improve emission controls. One of the most challenging problems associated with aluminum casting is the influence of convection during all stages of solidification. The strength of fluid flow changes the "as cast" internal structure (microstructure) such that the yield, fracture and fatigue strengths of the cast ingot can vary considerably. Although the importance of fluid flow has been recognized for decades, not even a simple model has been developed to predict the effect on microstructure.
Materials Science Laboratory - Columnar-to-Equiaxed Transition in Solidification Processing (CETSOL) and Microstructure Formation in Casting of Technical Alloys under Diffusive and Magnetically Controlled Convective Conditions (MICAST) are two investigations which will examine different growth patterns and evolution of microstructures during crystallization of metallic alloys in microgravity.
The major objective CETSOL is to improve and validate the modelling of Columnar-Equiaxed Transition (CET) and of the grain microstructure in solidification processing. This aims to give industry confidence in the reliability of the numerical tools introduced in their integrated numerical models of casting, and their relationship. To achieve this goal, intensive deepening of the quantitative characterization of the basic physical phenomena that, from the microscopic to the macroscopic scales, govern microstructure formation and CET will be pursued. This endeavor will be based on the benchmark data obtained from systematic series of critical experiments under diffusive conditions (critical experiments under convective conditions), with fluid flow in the melt due to natural buoyancy-driven convection (convection controlled by applying an external field, magnetic field or vibration).
CETSOL provides science teams and industrial partners confidence in the reliability of the numerical tools introduced in their integrated numerical models of metallic alloy casting. To achieve this goal, intensive deepening of the quantitative characterisation of the basic physical phenomena that, from the microscopic to the macroscopic scales, govern microstructure formation and CET will be pursued.
Columnar-to-equiaxed transition (CET) occurs during columnar growth when new grains grow ahead of the columnar front in the undercooled liquid. Under certain conditions, these grains can stop the columnar growth and then the solidification microstructure becomes equiaxed. Experiments planned in the framework of the CETSOL experiment are expected to take place in facilities on board the International Space Station (ISS). This is justified by the long-duration required to solidify samples with the objective to study the columnar-to-equiaxed transition. Indeed, the length scale of the grain structure when columnar growth takes place is of the order of the casting scale rather than the microstructure scale. This is due to the fact that, to a first approximation, it is the heat flow that controls the transition rather than the solute flow. Experimental programs are being carried out on ground by the science team and industrial partners on aluminium-nickel and aluminium-silicon alloys.
MICAST studies microstructure formation during casting of technical alloys under diffusive and magnetically controlled convective conditions. The experimental results together with parametric studies using numerical simulations, will be used to optimize industrial casting processes.
MICAST identifies and controls experimentally the fluid-flow patterns that affect microstructure evolution during casting processes, and to develop analytical and advanced numerical models. The microgravity environment of the International Space Station (ISS) is of special importance to this project because only there are all gravity-induced convections eliminated and well-defined conditions for solidification prevail that can be disturbed by artificial fluid flow being under full control of the experimenters. Design solutions that make it possible to improve casting processes and especially aluminum alloys with well-defined properties will be provided.
MICAST studies the influence of pure diffusive and convective conditions on aluminium-silicon (AlSi) and aluminium-silicon-iron (AlSiFe) cast alloys on the microstructure evolution during directional solidification with and without rotating magnetic field.
Industry partners to the projects are seeking to optimise ground processes and have a direct interest in the knowledge that will be gained from the experiments. This could in turn find its way into the development of new light-weight, high-performance structural materials for space applications.
The generation of vitally important benchmark data on orbit that will improve numerical models on Earth describing solidification processes. The ultimate goal of this research is to increase our understanding in materials solidification processes in order to help develop new stronger lighter-weight materials which will have a significant impact on industry for solving the most significant issues facing our planet such as fuel efficiency and consumption and recycling of materials. Results of this research will have cost reducing effects across numerous industries and in turn make these industries more competitive and attractive to investment.
Each sample cartridge assembly (SCA) shall be fully processed in the MSRR MSL LGF furnace, including final solidification step. After return on Earth, the SCA's are destructively analyzed by the investigators. The structure of the solidified metallic alloy is then compared to predictions derived from complex numerical codes. This comparison helps to adapt and improve the numerical codes developed by scientists.
The crewmember will insert one SCA into the MSRR MSL LGF. Following power on, the MSRR MSL LGF and vary the power profile of the various furnace heaters to characterize the thermal behavior of the melted metallic alloy in the SCA. Temperature sensors signals will be downlinked to Earth for in-depth assessment by science teams. Numerical codes will provide additional information about the state of the SCA under the thermal constraints on orbit. For each SCA the conditions of the Rotating Magnetic Field (RMF) of the MSL will be varied. Following cool down of the furnace, the SCA is removed from the MSL/LGF furnace and stowed passively until return to Earth. The samples for MSL CETSOL and MICAST are as follows:
- MICAST1 SCA #1:Al-7wt%Si (four solidification velocities, free cooldown;)
- MICAST1 SCA #2: Al-7wt%Si (constant Rotating Magnetic Field (RMF), four solidification velocities, free cooldown)
- MICAST1 SCA #3: Al-7wt%Si-1wt%Fe (four solidification velocities, free cooldown)
- MICAST1 SCA #4: Al-7wt%Si-1wt%Fe (constant RMF, four solidification velocities, free cooldown)
- MICAST1 SCA #5: Al-7wt%Si-1wt%Fe (four RMF settings, four solidification velocities, free cool down)
- MICAST SCA #6: Al-7wt%Si (oriented seed, two solidification velocities, TBD cool down)
- MICAST SCA #7: Al-7wt%Si (oriented seed, two solidification velocities, TBD cool down)
- CETSOL1 SCA #1: Al-7wt%Si-0.5wt%AT5B (short homogenization time, increase of solidification velocity, free cool down)
- CETSOL1 SCA #2: Al-7wt%Si-0.5wt%AT5B (long homogenization time, increase of solidification velocity, free cool down)CETSOL1 SCA #3: Al-7wt%Si (long homogenization time, constant solidification velocity, power down)
- CETSOL3 SCA #4: Al-7wt%Si (constant RMF, constant solidification velocity, power down)
- CETSOL1 SCA #5: Al-7wt%Si-0.5wt%AT5B (short homogenization time, constant solidification velocity, power down)
- CETSOL3 SCA #6: Al-7wt%Si-0.5wt%AT5B (long homogenization time, constant solidification velocity, power down)
When a molten metal or alloy cools and crystallizes, the resulting solid generally has two competing types of grain structures. At first, fast cooling of the melt normally forms columns of long branching grains growing inward from the side walls . Then as internal heat is shed from the remaining liquid fraction, the cooling rate decreases which often leads to seeding and growth of equiaxed (having axes of about the same length) grains. This effect is described as a columnar-to-equiaxed transition (CET) and is very important, and highly studied, in metal forming processes and metallurgy since it greatly affects the physical properties and behavior of virtually all metallic products, including high-value parts such as single crystal turbine blades in aircraft engines. CET experiments to study and control this transitional process have been successfully performed in the Materials Science Laboratory (MSL) with the Low Gradient Furnace (LGF) module onboard the ISS from November 2009 until April 2010.
Turbulent melt flow is minimized in space which enables growth of equiaxed grains free of sedimentation and buoyancy effects. The critical phases of each microgravity experiment, i.e. the homogenization and solidification phases, were performed during sleep periods of the astronauts to reduce, as well, vibrational disturbances. Gravity sensors data close to the MSL confirm that a gravity level below ±0.0005 g was achieved during all experiments, g = 9.8m/s² on Earth. Aluminium-silicon (AlSi) alloys with and without grain refiners (particles added to limit crystal grain branching) were processed successfully in the LGF. First analysis shows that in the non grain refined samples columnar dendritic growth exists, whereas CET is observed in the grain refined samples. critical parameters for the temperature gradient and the cooling rate describing CET are determined from analysis of the thermal data and the grain structure. These data are used for initial numerical simulations to predict the position of the columnar-to-equiaxed transition and will form a unique database for calibration and further development of numerical CET-modeling (Zimmermann et al. 2011).
Preliminary results of an AlSi mixture with grain refiners show that, during solidification, the columnar crystallization front advances forward and an undercooled liquid zone develops ahead the front, thus facilitating equiaxed crystal formation. Equiaxed nucleation with grain refiners follows the free growth model in simulation. In most castings, grain refiner particles may be engulfed or pushed by the growing solid liquid interface. So, these grain refiner particles cannot initiate grains and normally end up in the grain boundaries, thus general grain refiner efficiency is very low. It was found that the efficiency of the grain refiners is at a maximum when addition level is low. Experimental CET, in this case, is at a distance of ~128 ± 2 mm versus the simulation distance of 127.5 mm. Hence the agreement between model simulation and experiment is reasonably strong. The columnar length is approximately equal to the distance the furnace is moving at a slower velocity and, therefore, it is possible to suggest that CET is related to the velocity jump and resulting temperature change. More studies of alloy systems without grain refiners are being conducted, and the influences of grain refiners need to be evaluated further (Mirihanage et al. 2011).
Mirihanage WU, Browne DJ, Sturz L, Zimmermann G. Numerical Modelling of the Material Science Lab - Low Gradient Furnace (MSL-LGF) Microgravity Directional Solidification Experiments on the Columnar to Equiaxed Transition. IOP Conferene Series: Material Science and Engineering. 2012 January 12; 27(1): 012010.
Zimmermann G, Sturz L, Billia B, Mangelinck-Noel N, Nguyen-Thi H, Gandin C, Browne DJ, Mirihanage WU. Investigation of columnar-to-equiaxed transition in solidification processing of AlSi alloys in microgravity – The CETSOL project. Journal of Physics: Conference Series. 2011 December 6; 327(1): 012003-12014. DOI: 10.1088/1742-6596/327/1/012003.
Ground Based Results Publications
Zaidat K, Mangelinck-Noel N, Moreau R. Control of melt convection by a traveling magnetic field during the directional solidification of Al-Ni alloys.Comptes Rendus de l'Academie des Sciences - Series IIB - Mechanics. 2007; 335: 330-335.
Sylla L, Duffar T. Numerical simulation of temperature and pressure fields in CdTe growth experiment in the Material Science Laboratory (MSL) onboard the International Space Station in relation to dewtting. Journal of Crystal Growth. 2007; 303: 187-192.
Ratke L, Steinbach S, Muller G, Hainke M, Roosz A, Fautrelle Y, Dupouy MD, Zimmermann G, Weiss A. MICAST-Microstructure Formation in Casting of technical alloys under diffusive and magnetically controoled covection conditions. Material Science Forum. 2006; 508: 131-144. DOI: 10.4028/www.scientific.net/MSF.508.131.
MSL-CETSOL and MICAST Sample Cartridge Assembly, to be processed in the Materials Science Laboratory (MSL) Facility and brought back to Earth for destructive analysis.
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NASA Image: ISS021E023149 - STS-129 Frank De Winne poses for a photo while holding a Materials Science Laboratory (MSL) Mechanical Protection Container (MPC) Tube during MSL commissioning activities in the U.S. Laboratory/Destiny.
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From left to right, Professor Tewari, Francis Chiaramonte, Winfried Aicher, Corky Clinton and Frank Szofran. On the table you is the MSL-CETSOL and MICAST cylinder resting on the aluminum foil. The long white cylinder is a crucible; inside the crucible is the alloy sample of aluminum and silicon. This entire unit was placed into the low gradient furnace in the MSRR. The sample was melted and solidified in controlled manner at a given temperature gradient and solidification speed. The microstructure of the sample will be studied in detail. Image courtesy of David Higginbotham, MSFC.
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NASA Image: ISS021E006202 - European Space Agency astronaut Frank De Winne, Expedition 21 commander, works with Materials Science Laboratory (MSL) hardware in the Destiny laboratory of the International Space Station.
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NASA Image: ISS026E014918 - NASA astronaut Catherine (Cady) Coleman, Expedition 26 flight engineer, removes the Low Gradient Furnace (LGF) and installs the Solidification and Quench Furnace (SQF) in the Material Science Laboratory (MSL) in the Destiny laboratory of the International Space Station
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From left to right: Dr. Petra Neuhause and Dr. Harold Lenski, both with Astrium, Germany accompanied by Jeff Clancy of Teledyne Brown Engineering, use heat guns to open the first U.S. sample cartridge processed in the solidification quench furnace in the Materials Science Research Rack aboard the International Space Station. The sample was returned to Earth on the space shuttle mission STS 133. Image courtesy of NASA/MSFC/Emmett Given.
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Image # 392 for web feature: From left to right: Dr. Alex Lehoczky, materials scientist at the Marshall Space Flight Center, Dr. Surendra Tewari, professor at Cleveland State University, Cleveland, Ohio, and Dr. Petra Neuhause with Astrium, Germany examine the first U.S. sample processed in the solidification quench furnace in the Materials Science Research Rack. Tewari is transporting the sample to Cleveland State University for additional study and analysis. Image courtesy of NASA/MSFC/Emmett Given.
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