DEvice for the study of Critical LIquids and Crystallization - Directional Solidification Insert (DECLIC-DSI) - 01.09.14
Science Objectives for Everyone DEvice for the study of Critical LIquids and Crystallization (DECLIC) is a multi-user facility utilized to study transparent media and their phase transitions in microgravity onboard the International Space Station (ISS). The Directional Solidification Insert (DSI) portion of the DECLIC multi-user facility experiment will study a series of benchmark experiments on transparent alloys that freeze like metals under microgravity onboard the International Space Station (ISS) using SCN (succinonitrile-a transparent organic substance in the liquid state that is used to study the phenomena related to solidification processes) based alloys. The DSI insert will be installed for the second run of the three series of DECLIC experiments.
Science Results for Everyone
Pardon me, your liquid-solid interface is showing. Studying the process of solidification can improve our understanding of metallurgical processes, important in design and processing of materials. In a series of experiments using transparent alloys that freeze like metals in microgravity, researchers recorded three-dimensional images of the micro-structures that form at the liquid-solid interface. These interface patterns govern mechanical and physical properties, so understanding them could enable design of improved materials. Researchers captured 7,000 images from a large range of experimental conditions and are analyzing the data.
Centre National d'Etudes Spatiales, Toulouse, , France
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
For supercritical fluids (HTI, ALI), DECLIC is a continuation of one conducted aboard the Mir Space Station and the Space Shuttle. For solidification of transparent model alloys, DECLIC-DSI is the first mission in space environment, following series of intensive studies on ground.
- DECLIC-DSI (DEvice for the study of Critical LIquids and Crystallization-Directional Solidification Insert) involves the in situ and real-time observation of the microstructures that form at the liquid-solid interface when transparent materials solidify. This will make it possible to simulate metallic alloys, with the advantage of recording the dynamical formation and selection of the microstructures. Another practical advantage is that only images will be transferred to the ground instead of heavy samples for post mortem characterization since the transport into orbit and the return to Earth greatly increases the cost of missions.
- The study of cellular and dendritic (growth shape with tree-like side branches like snowflakes) solidification patterns associated with DECLIC-DSI provides an opportunity to gain an insight into the general problem of pattern formation since the three-dimensional pattern evolution dynamics can be quantitatively studied under well-defined conditions.
- The DECLIC-DSI experiment intends to provide a better understanding of the relationship between micro- and macrostructure formation during solidification processes. For the first increments on ISS, DECLIC-DSI contains a cell filled with a dilute SCN - Camphor alloy, which will be moved from a hot zone to a cold zone at various speeds and temperature gradients.
Directional Solidification Insert (DSI) involves the study of directional solidification in relation to transparent model alloys. This involves investigating the birth and growth of morphological instabilities at the solid-liquid interface and the effects of coupling between the solidifying interface and the convection. By observing these phenomena in a microgravity environment, it will be possible to refine the theoretical models and numerical simulation predictions, which will ultimately result in the improvement of the industrial ground-based material development processes. The ambition of the reduced-gravity experiments on ISS, which will consist of directional solidification of SCN-based bulk alloys in the Directional Solidification Insert (DSI) of the DECLIC facility with a systematic variation of the process parameters, is to obtain benchmark data on cellular and dendritic microstructure formation under diffusive transport conditions. Precise measurement of interface shape and geometrical characterization of cellular and dendritic patterns, as well as of individual cell or dendrite will be carried out as a function of time for different values of composition, growth rate and temperature gradient. These measurements will be used in combination with modeling and numerical simulations of the temperature field to establish the physics that govern the dynamics of interface pattern selection, and to quantitatively determine the conditions for the planar to cellular and cellular to dendritic transitions. Optical observations of the solidification front will be done either directly or by interferometry (imaging using the interference fringes resulting from the recombination of reference and object light beams issued from the same coherent source) with the cartridge placed in one arm of a Mach-Zehnder interferometer (a device used to determine phase shifts caused by the solidifying sample which is placed in the optical path of the object beam).
The DECLIC facility provides power, communications, command/control, data storage, and multiple, flexible optical capabilities in support of each experiment. DECLIC-DSI involves investigating the birth and growth of morphological instabilities and the effects of coupling between the solidifying interface and the convection. By observing these phenomena in a microgravity environment, it will be possible to refine the theoretical models and numerical simulation predictions, which will ultimately result in the improvement of the industrial ground-based material development processes.
DECLIC-DSI will establish the fundamental physics that govern the formation and selection of solidification patterns. This will provide an opportunity to gain an insight into the general problem of pattern formation, as solidification patterns are recognized to be similar to those forming in many other branches of science.
In order to adjust the parameters and optimize the scientific results, some data must be downloaded in real-time or near real-time. For complete analysis by the scientists, the data will be retrieved either via telemetry in deferred time, or via the removal of hard disks which will be brought back by the crew. The DECLIC-DSI Experiment is scheduled for a period of 75 days.
The ISS crew will install the DECLIC hardware into an EXPRESS Rack in the U.S. Laboratory. The DSI insert will be installed into DECLIC for the second run of the series of DECLIC experiments. Crew participation is not required during the run(s). Tape change-out will be required by the crew at some stage during the run(s).
DECLIC-DSI is dedicated to the study of solidification to improve the understanding of metallurgical processes. It uses a an organic alloy that freezes like metals but which is transparent to visible light so that the whole process of solidification is visible.
DECLIC-DSI completed four successful solidifications by the end of November 2010. The research team captured 7000 images during the final session meeting all scientific objectives. DECLIC-DSI contains a crucible filled with a dilute succinonitrile-camphor alloy of a well-defined concentration, which is solidified by motion from a hot zone to a cold zone at a constant pulling rate. In these runs, a large range of experimental conditions were explored to vary the resulting microstructure. Both long solidifications and solidifications with jumps in pulling rates had been performed to get the whole dynamics and mechanisms of microstructure formation or change, spacing adjustment, and pattern ordering. During two solidification runs at very low speeds, two types of exotic cellular patterns became evident. Latest data are currently under treatment.
The study of solidification microstructure formation is very important in the design and processing of new material. The interface patterns formed by solidification largely govern mechanical and physical properties, thus materials and processing conditions can be designed to obtain specific patterns which give optimum properties and better reliability of the finished product. Experiments such as DECLIC provide a better understanding of the relationship between micro- and macrostructure formation during solidification processes. The experiment ultimately could result in new and better materials for use in manufacturing on Earth (Bergeon et al., 2011).
Ramirez A, Chen L, Bergeon N, Billia B, Gu J, Trivedi R. In situ and real time characterization of interface microstructure in 3D alloy solidification: benchmark microgravity experiments in the DECLIC-Directional Solidification Insert on ISS. IOP Conferene Series: Material Science and Engineering. 2011; 27(1).
Bergeon N, Ramirez A, Chen L, Billia B, Gu J, Trivedi R. Dynamics of interface pattern formation in 3D alloy solidification: first results from experiments in the DECLIC directional solidification insert on the International Space Station. Journal of Materials Science. 2011; 46: 6191-6202. DOI: 10.1007/s10853-011-5382-2.
Ground Based Results Publications
Ames Laboratory senior metallurgist Rohit Trivedi will be studying how crystals, such as these nickel-based superconductors, grow in low gravity experiments on board the International Space Station. Image courtesy of USDOE's Ames Laboratory.
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