Space station experiment gives hope of stronger metals on Earth

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

The mechanism by which liquids turning to solids is more complex that previously thought and understanding it better could improve design and production of metals, scientists say.

A recent series of experiments conducted aboard the the International Space Station used transparent alloys to observe microstructures that form at the point the material solidifies.

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.

Alloy solidification involves crystallizing or freezing a liquid mixture of different atomic constituents. In the experiment, the liquid was pulled towards a cold source to solidify, a technique known as directional 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 – finer-sized structures generally yield stronger materials.

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 could help scientists design and produce more reliable materials and materials with specific properties.

Cell and dendrite characteristics and their effect on materials were recently published in the journal Acta Materiala.

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