EXPERIMENT RECORD N° 9661
Transparent Alloys - SETA-Solidification along an Eutectic Path in Ternary Alloys
  1. 2018 • ISS Increments 55-56
  2. 2020 • ISS Increment 63
Physical Sciences:
  • Material Sciences
  • Solidification dynamics
MSG (Microgravity Science Glovebox)
Wim Sillekens
wim.sillekens@esa.int
S. Akamatsu (1), S. Bottin-Rousseau (1), G. Faivre (1), U. Hecht (2), V.T. Witusiewicz (2), M. Serefoglu (3), L. Froyen (4), A. Genau (5), L. Ratke (6), R. Napolitano (6)
(1)  
INSP-UPMC
4 place Jussieu
75005 Paris
FRANCE
Tel:  
+33(0)1.44.27.63.99
e-mail:  
akamatsu@insp.jussieu.fr
bottin@insp.jussieu.fr
(2)  
ACCESS e.V.
Intzestrasse 5
52056 Aachen
GERMANY
Tel:  
+49(0)2418098014
e-mail:  
u.hecht@access-technology.de
v.vitusevych@access-technology.de
(3)  
Koç University
Istanbul
TURKEY
(4)  
KU Leuven
Department of Materials Engineering
BELGIUM
(5)  
University of Alabama at Birmingham
1720 2nd Ave South
Birmingham, AL 35294
USA
BACKGROUND 
Solidification is a classical example of pattern formation outside of equilibrium, in which a structured final state forms by self-organization processes from a structureless initial state. The solidification of metallic alloys results in the spontaneous development of a large variety of microstructures: dendrites, cells, multi-phase eutectic or peritectic composites, and multi-scale architectures that are made of combinations of several subunits. These structures are a frozen trace of interfacial patterns that exhibit a complex spatio-temporal dynamics. Although solidification is only the first stage of materials fabrication, and is often followed by heat treatments, rolling, or other processing steps, the material usually keeps a memory of the initial structuration, and therefore the solidification microstructures largely influence materials properties. For a physicist, it is a challenge to understand by which mechanisms these structures form, and how their genesis can be controlled and guided towards desirable target structures.

The solidification of binary eutectic alloys produces two-phase composite materials in which the microstructure, that is, the geometrical distribution of the two solid phases, results from complex pattern-formation processes at the moving solid-liquid interface. Since the volume fraction of the two solids depends on the local composition, solidification dynamics can be strongly influenced by thermosolutal convection in the liquid.

The phase diagram of a eutectic alloy exhibits a particular point, the so-called eutectic point, at which two solid phases of distinct compositions are in equilibrium with the liquid. The composition of the liquid lies in between the compositions of the two solids, and therefore solidification of a liquid of near-eutectic composition yields a two-phase solid. While the global volume fraction of the two phases is fixed by the sample composition, as imposed by mass conservation, their spatial distribution is determined by self-organization processes that take place at the crystallization front. The two solids exchange components by diffusion in the liquid, while diffusion in the solid can usually be neglected. For alloys with non-faceted solid–liquid interfaces, local equilibrium at the growth front fixes the interface shape. In particular, the Gibbs-Thomson effect, which describes the displacement of the local equilibrium temperature by the interface curvature, and the equilibrium at the trijunction points (Young´s law) need to be taken into account.

A well-controlled method to study eutectic microstructures is directional solidification: a sample is placed between two furnaces of different temperatures and pulled with controlled velocity V into the colder zone. In steady-state conditions, the crystallization front advances with velocity V. The two kinds of microstructures that are most frequently found in the resulting solid are lamellae and rods, that is, alternating platelets of the two solid phases that grow roughly along the temperature gradient, and cylinders of the minority phase embedded in a matrix of the majority phase, respectively. They correspond to solidification front patterns with banded (or striped) and hexagonal arrangements, respectively.

GOAL
  • Study the formation and relaxation of defects in rod-like structures, and the transition rod-to-lamellar in eutectic growth patterns.
  • The analysis of forcing effects due to the thermal gradient.

SETA - Solidification along an Eutectic Path in Ternary Alloys
GOAL
  • Observation of the microstructure formation to analyze different aspects.
  • Improve and validate numerical simulations of the eutectic microstructure formation in a ternary alloy using the in-house phase-fields code MICRESS.

METCOMP - Metastable Solidification of Composites: Novel Peritectic Structures and In-situ composites
GOAL
  • Study the influence of gravitational effect on the microstructures evolution and determine microstructure selection maps, correlated to particle size, growth dynamics and fluid flow processes parameters.
  • Improve the control of peritectic solidification of industrial relevance.

CETSOL 1&2 - Columnar to Equiaxed Transition in Solidification Processing 1&2
GOAL
  • Investigate the time-dependent solidification rate in columnar and equiaxed regimes, including the temperature gradient and the temperature of the solid/liquid interface.
  • Study the occurrence of nucleation events and mechanism of fragmentation.

AIM of SETA
The aim of this experiment is to study the pattern formation during univariant eutectic reaction in directional solidification in transparent ternary alloys. This pattern formation process shall not be affected by wall effects or by convective contributions to the heat and mass transport during the phase formation. The first aim is achieved by using a sample cross-section of 1 mm × 6 mm, at least 10 times larger in the smaller dimension than the eutectic cells which are expected to form. This rather large cross-section allows for a real 3D-formation of the microstructure, but leads under Earth’s gravity conditions to unavoidable and unknown thermal-solutal convection in the liquid phase.

Thus the space experiments under microgravity shall for the first time enable the observation of the dynamics of the pattern formation in an univariant two-phase eutectic alloy. The results will be used to improve and validate numerical simulations of the eutectic microstructure formation in a ternary alloy using the inhouse phase-field code MICRESS.

SPECIFIC GOALS of SETA
- Observation of the microstructure formation in univariant two-phase eutectic growth along the different eutectic grooves
- To study nucleation of eutectic phases on pre-existing phases in transient growth
- Observation of the origin of fault lines in eutectic structures and changes of the faultless eutectic structure.

SPACE APPLICATIONS
The Space Application for this investigation has yet to be identified.

EARTH APPLICATIONS
The solidification of organic transparent substances represents an analogue for that of metallic alloys; its study thus adds to the knowledge base for solidification dynamics and microstructure formation with possible technological implications for industrial casting processes and the metallic products manufactured therewith.
The microgravity experiment, using the multi-user TRANSPARENT ALLOYS apparatus, will be processed in the Materials Science Glovebox on board of the International Space Station.
The instrument is a Bridgman Furnace that permits the monitoring and control of solidification-melting processes in plastic samples confined in experimental cartridges on micro-scale resolution. These recipients are positioned and can be translated between clamps, whose temperatures can be selected. Temperature setting aims to achieve a desired thermal gradient in the adiabatic zone where the solidification takes place.

The alloy used in the Transparent Alloys - SETA Experiment is the (D)camphor-neopentylglycol-succinonitrile (DC-NPG-SCN) system (75.3wt% SCN -24.2wt% DC- 0.5wt% NPG). Experiment operations are five to six experiment runs per cartridge/sample, with subsequent solidification phases; upload of samples within -20°C and +80°C; the duration of each run is 60 hours, and 15 days of science operations.

Sample geometryFlat sample geometry 100 x 6 mm, thickness of 1 mm

Sample material
Requirement: One alloy of the DC-NPG-SCN system
Comment: exact composition: 75.3 wt.% SCN - 24.2 wt.% DC - 0.5 wt.% NPG (TL=310.6 K; Ts=306.1 K; 20% fraction liquid at 309 K)

PROTOCOL
The experiments as outlined below include two cartridges.
All three experiments for both cartridges are mandatory to provide for a fully exploitable set of science data (they provide complementary information). There is no specific preferred experiment order for the cartridges. The experiment runs can be performed without delay in between or with a break if operationally convenient (as long as operational coverage is ensured for optical adjustments). The experiment runs cannot be performed “back-to-back”, meaning that intermediate melting is required.

SETA TAC1-1
Present experiment is intended to find the best settings for the temperatures of hot and cold clamps, for the cameras and illumination. These values then will be used for the subsequent experiments with this sample/alloy. For the steps 3–6, optical adjustment actions are needed once per day consisting of refocussing and adjusting of exposure time and thus requiring operational attendance.
1. Switch on the facility
2. Directional melting
3. Homogenisation and adjustment
4. Second adjustment and Directional Solidification (DS) with translation speed v=4.8 μm/min
5. Directional solidification (DS) with translation speed v=2.7 μm/min
6. Directional solidification (DS) with translation speed v=2.4 μm/min
7. DS with v=0.6 μm/min
8. Termination of the experiment:

SETA TAC1-2
1. Switch on the facility
2. Melting of the sample without translation
3. Like in Experiment SETA TAC1-1
4. Like in Experiment SETA TAC1-1
5. DS with linearly decreasing translation speed from v=4.8 to 0.6 μm/min
6. DS with v=0.6 μm/min
7. DS with linearly increasing translation speed from V=0.6 to 4.8 μm/min
8. Termination of the experiment

SETA TAC1-3
1. Switch on the facility
2. Melting of the sample without translation.
3. Like in Experiment SETA TAC1-1
4. Like in Experiment SETA TAC1-1
5. DS with exponentially decreasing translation speed from v=4.8 to 0.6 μm/min
6. DS with v=0.6 μm/min
7. DS with exponentially increasing translation speed from v=0.6 to 4.8 μm/min
8. Termination of the experiment

Sequence for SETA TAC2
SETA TAC2-1
Present experiment is intended to find the best settings for the temperatures of hot and cold clamps, for the cameras and illumination. These values then will be used for the subsequent experiments with this sample/alloy. For the steps 3-6, optical adjustment actions are needed once per day consisting of refocussing and adjusting of exposure time and thus requiring operational attendance.
1. Switch on the facility
2. Directional melting of about 80 mm of the sample
3. Homogenisation and adjustment
4. Second adjustment and Directional Solidification (DS) with translation speed v=4.8 μm/min
5. Directional solidification (DS) with translation speed v=2.4 μm/min
6. Directional solidification (DS) with translation speed v=2.7 μm/min
7. DS with v=4.8 μm/min
8. Termination of the experiment

SETA TAC2-2
1. Switch on the facility
2. Melting of the sample without translation
3. Like in Experiment SETA TAC2-1
4. Like in Experiment SETA TAC2-1
5. DS with linearly increasing translation speed from v=0.6 to 4.8 μm/min
6. DS with v=4.8 μm/min
7. DS with linearly decreasing translation speed from V=4.8 to 0.6 μm/min
8. Termination of the experiment

SETA TAC2-3
1. Switch on the facility
2. Melting of the sample without translation
3. Like in Experiment SETA TAC2-1
4. Like in Experiment SETA TAC2-1
5. DS with exponentially increasing translation speed from v=0.6 to 4.8 μm/min
6. DS with v=4.8 μm/min
7. DS with exponentially decreasing translation speed from v=4.8 to 0.6 μm/min
8. Termination of the experiment

Parameters Measured/Recorded
- All science parameters shall be measured at 1 Hz
- g-Level to be recorded during the entire experiment run as close as possible to the TRANSPARENT ALLOYS instrument, inside MSG work volume. However, a temporary unavailability of micro-g level recordings shall not result in an interruption of the experiments.

- Hot clamps temperature
- Cold clamps temperature
- Sample position
- Camera position in x-direction
- Camera settings
- Illumination settings
- Focus position of camera
- Recording of both camera images

Lifetime of sample material in the cartridgesix months

Planned Analyses
- Image processing to improve contrast and distinguish different eutectic phases
- Compilation of video segments
- Quantitative analysis of imaged microstructure evolution
- Thermal profile analysis

Expected results
Characteristics of pattern formation in eutectic microstructure development during directional solidification of a ternary alloy: stability boundaries, spacing, branching dynamics, grain development, orientation relations, etc.

[1]  
M. Apel, B. Böttger, V. Witusiewicz, U. Hecht, I. Steinbach, (2004), "Lamellar pattern formation during 2-D-directional solidification of ternary eutectic alloys", in: Solidification and Crystallization, Chapter 29, D.M. Herlach, Weinheim: Wiley-VCH - https://doi.org/10.1002/3527603506.ch29, pp. 271-279.
[2]  
L. Sturz, V.T. Witusiewicz, U. Hecht, S. Rex, (2004), "Organic alloy systems suitable for the investigations of regular binary and ternary eutectic growth", Journal of Crystal Growth, 270, 1-2, pp. 273-282.
[3]  
V.T. Witusiewicz, L. Sturz, U. Hecht, S. Rex, (2006), "Phase equilibria and eutectic growth in quaternary organic alloys amino-methyl-propanediol-(D)camphorneopentylglycol-succinonitrile", Journal of Crystal Growth, 297, pp. 117-132.
[4]  
S. Akamatsu, S. Bottin-Rousseau, M. Perrut, G. Faivre, V.T. Witusiewicz, L. Sturz, (2007), "Real-time study of thin and bulk eutectic growth in succinonitrile-(d)camphor alloys", Journal of Crystal Growth, 299, 2, pp. 418-428.
[5]  
A. Ludwig, J. Mogerisch, M. Kolbe, G. Zimmermann, L. Sturz, N. Bergeon, B. Billia, G. Faivre, S. Akamatsu, S. Bottin-Rousseau, D. Voss, (2012), "Advanced Solidification Studies on Transparent Alloy Systems: A New European Solidification Insert for Material Science Glovebox on Board the International Space Station", JOM: Journal of the Minerals, Metals and Materials Society, 64, 9, DOI: 10.1007/s11837-012-0403-4, pp. 1097-1101.
[6]  
S. Akamatsu, M. Plapp, (2015), "Eutectic and peritectic solidification patterns", Current Opinion in Solid State and Materials Science, 20, 1, DOI: 10.1016/j.cossms.2015.10.002, pp. 46-54.
[7]  
M. Plapp, S. Bottin-Rousseau, G. Faivre, S. Akamatsu, (2017), "Eutectic solidification patterns: Interest of microgravity environment", Comptes Rendus Mécanique, 345, 1, pp. 56-65.
click on items to display

Figure 1: Schematic experiment concept diagram. Hot zone and cold zone heater fixed in a defined distance resulting in an adiabatic zone between hot and cold zones. The cold zone heater may also work as cooler, depending on the ambient temperature. Experiment to be planned in such way that the solidification interface will be located within the adiabatic zone and shall be observed by visual means of a camera. Sample moved in relation to the heater assembly (moving to the left for directional solidification; moving to the right for directional melting). The observation of the melting/solidification interface is performed via camera in changing position (optical axis perpendicular and tilted w.r.t. the sample plane). Two different camera angles required only for SETA and SEBA. Camera can be implemented as adjustable or as two fixed cameras.

Figure 2: Sample geometry.

Figure 3: Experiment profiles for SETA TAC1 (timing includes maximum number of iterations; total time for the three experiments is 171 h).

Figure 4: Experiment profiles for SETA TAC2 (timing includes maximum number of iterations; total time for the three experiments is 171 h).

Figure 5: Experiment Timeline

Figure 6: The Transparent Alloys furnace in the Microgravity Science Glovebox-MSG. Credit NASA
http://eea.spaceflight.es
a.int/attachments/spacest
ations/ID5d6ce32308007.pd
f

Figure 7: Scheme of the in-situ observation technique (a) implemented in the facility TRANSPARENT ALLOYS. It allows observing wide interface regions which display lamellar (b) or rod-like (c) eutectic patterns. Credit: Plapp et al., Eutectic solidification patterns: Interest of microgravity environment, C. R.Mecanique 345(2017): 56-65

Fact sheet for "TRANSPARENT" project - in German and English language. Credit: DLR
 
© 2024 European Space Agency