Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Freeze! Watching alloys change from liquid to solid could lead to better metals

09.03.2015

If you put a camera in the ice machine and watched water turn into ice, the process would look simple. But the mechanism behind liquids turning to solids is actually quite complex, and understanding it better could improve design and production of metals. A recent investigation aboard the International Space Station contributed to that understanding.

A series of experiments conducted in the Directional Solidification Insert (DSI) of the Device for the study of Critical Liquids and Crystallization (DECLIC) used transparent alloys to observe microstructures that form at the point the material solidifies.


This image shows the dendritic pattern of the Succinonitrile-Camphor alloy grown in microgravity, seen from the top.

Credit: Nathalie Bergeon

These alloys, or "plastic crystals," freeze or solidify the same way metals do and form the same microstructures in the process. But because metals are opaque, researchers have to analyze the process of solidification after the fact.

With the transparent alloys, they can observe solidification as it happens. Using transparent alloys also makes it possible to perform multiple experiments on the same sample, and transferring images to the ground for analysis, rather than actual samples, greatly reduces the cost.

The DSI recorded images during the entire solidification process. Top views clearly show the microstructure pattern forming at the interface between liquid and solid, and side views provide the shape and motion of that interface.

Alloy solidification involves crystallizing or freezing a liquid mixture of different atomic constituents. For example, a mixture of iron and carbon hardens into steel.

"The distribution of these constituents in the solid depends on the growth process and behavior at the interface between solid and liquid," explains principal investigator Nathalie Bergeon, Ph.D., Institut Materiaux Microelectronique Nanosciences de Provence in France.

The process can be controlled by applying a temperature gradient and pulling the liquid toward the cold part to solidify, a technique known as directional solidification and one of the key ways to study solidification.

During directional solidification, the liquid-solid interface develops either three-dimensional cell-like structures or snowflake-like dendrites. Their pattern and size play key roles in the mechanical and physical properties of the material; for example, finer-sized structures generally yield stronger materials. These characteristics play a role in all materials processed by commercial solidification techniques, such as continuous casting and laser welding.

Gravity has a strong effect on those characteristics, but that influence is greatly reduced in the microgravity environment of the space station, offering controlled conditions for study. Better understanding of these microstructure formations will, in turn, help scientists design and produce more reliable materials and materials with specific properties, as well as help to develop and test solidification models.

Observing these processes in a microgravity environment also helps scientists refine theoretical models and numerical simulations of metallic alloys. Ultimately, this work could result in new and better materials for use in manufacturing on Earth. Cell and dendrite characteristics and their effect on materials were recently published in the journal Acta Materiala.

Investigators also found that the cells and dendrites that form during solidification sometimes adopt surprising behaviors. For example, for certain growth parameters, the three-dimensional cellular structures moved or oscillated as they grew, expanding and contracting rhythmically much like lungs do when someone breathes.

The cells oscillate according to the underlying pattern they formed. These breath-like oscillations can split cells if they expand too much or cause them to disappear if they contract too much. These findings were published in Physical Review Letters.

In addition to the directional solidification study, DECLIC has been used to investigate low and high temperature critical fluids behavior, chemical reactivity in supercritical water, and transparent media under microgravity. The tool was developed by the French Space Agency (CNES) and operates as a joint project between CNES and NASA. Researchers at Aix Marseille Universite, France; Iowa State University; and Northeastern University, Massachusetts, collaborated on the DECLIC-DSI investigation.

We may not be interested in watching the water in our ice machine freeze, but understanding the solidification process will help researchers improve metal materials used for pipes, airplane wings, turbine blades and other applications.

Laura Niles | EurekAlert!

More articles from Physics and Astronomy:

nachricht Seeing the quantum future... literally
16.01.2017 | University of Sydney

nachricht Airborne thermometer to measure Arctic temperatures
11.01.2017 | Moscow Institute of Physics and Technology

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

Im Focus: How to inflate a hardened concrete shell with a weight of 80 t

At TU Wien, an alternative for resource intensive formwork for the construction of concrete domes was developed. It is now used in a test dome for the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur).

Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of...

Im Focus: Bacterial Pac Man molecule snaps at sugar

Many pathogens use certain sugar compounds from their host to help conceal themselves against the immune system. Scientists at the University of Bonn have now, in cooperation with researchers at the University of York in the United Kingdom, analyzed the dynamics of a bacterial molecule that is involved in this process. They demonstrate that the protein grabs onto the sugar molecule with a Pac Man-like chewing motion and holds it until it can be used. Their results could help design therapeutics that could make the protein poorer at grabbing and holding and hence compromise the pathogen in the host. The study has now been published in “Biophysical Journal”.

The cells of the mouth, nose and intestinal mucosa produce large quantities of a chemical called sialic acid. Many bacteria possess a special transport system...

Im Focus: Newly proposed reference datasets improve weather satellite data quality

UMD, NOAA collaboration demonstrates suitability of in-orbit datasets for weather satellite calibration

"Traffic and weather, together on the hour!" blasts your local radio station, while your smartphone knows the weather halfway across the world. A network of...

Im Focus: Repairing defects in fiber-reinforced plastics more efficiently

Fiber-reinforced plastics (FRP) are frequently used in the aeronautic and automobile industry. However, the repair of workpieces made of these composite materials is often less profitable than exchanging the part. In order to increase the lifetime of FRP parts and to make them more eco-efficient, the Laser Zentrum Hannover e.V. (LZH) and the Apodius GmbH want to combine a new measuring device for fiber layer orientation with an innovative laser-based repair process.

Defects in FRP pieces may be production or operation-related. Whether or not repair is cost-effective depends on the geometry of the defective area, the tools...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

Nothing will happen without batteries making it happen!

05.01.2017 | Event News

 
Latest News

Multiregional brain on a chip

16.01.2017 | Power and Electrical Engineering

New technology enables 5-D imaging in live animals, humans

16.01.2017 | Information Technology

Researchers develop environmentally friendly soy air filter

16.01.2017 | Power and Electrical Engineering

VideoLinks
B2B-VideoLinks
More VideoLinks >>>