Experiments in space improve the design of materials on Earth

Choosing the right material to build any technical or industrial object out of can be tricky. Objects like aircraft, cars and gas pipelines need to be made out of materials with specific properties for example the ability to withstand large forces. Natural materials, like metals, may not exhibit all of the required properties, and so alloys (or mixtures of materials) can be used.

The production of alloys involves the mechanical mixing of two or more substances in liquid form, which then cool or solidify. However, this transition from the liquid to the solid state is morphologically unstable and so the interface between the solid and the liquid evolves to a complex non-planar structure. These instabilities form in natural and manufactured systems and are responsible for the branched shape of snowflakes. Materials scientists study these propagations carefully in order to observe the micro scale structures of the material (which affects the strength) to subsequently improve the design of the materials.

Recently a collaborative team of researchers from NASA, France and the USA have started to study this solidification processes in space. The International Space Station has a nearly gravity-free environment which allows the growth of these solids in three dimensions to be observed, without the influence of gravity. Gravity can cause mixing via fluid flow within the liquid and disturb the natural solidification process and propagation pattern, and the team of scientists performed experiments under a range of temperature and time scales.

The results of this research indicate that without this buoyancy force, materials actually develop a more organised and regular structure on a micro scale than observed on Earth and will be used in the design for lighter and stronger materials.