Measurement of Thermophysical Properties for the Advancement and Development of Production Processes on Earth and in Space

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Metallic glasses are a class of materials where the atoms lack the long range order of crystalline materials. This leads to excellent properties that make metallic glasses interesting for a wide range of applications on the earth and in space. Demanding applications can profit from metallic glasses unique properties. Their high strength, corrosion and wear resistance is beneficial for robotics and other mechanisms for space exploration, as well as sports equipment, automotive and medical applications on earth.

Metallic glasses can be obtained, when the liquid metal is cooled fast enough, but a detailed understanding of the process that prevents the crystallization and leads to glass formation is still lacking. A major challenge for the study of glass formation is the interaction with the container, since the contact of the metallic melt with a container typically induces nucleation. The high reactivity of liquid metallic melts in contact to any container also leads to reactions that make the precise measurement of the thermophysical properties impossible. Such thermophysical properties are important in order to model and simulate manufacturing processes, such as casting or additive manufacturing on earth.

Hence, a containerless method, such as electromagnetic levitation is needed for the study of glass formation and for the measurement of thermophysical properties of the liquid phase. Our study was performed in microgravity to achieve a stable positioning of the sample without considerable heating or convection.

In our work, we measured the thermophysical properties for a Zirconium-based bulk metallic glass using the electromagnetic levitator on board the international space station. Furthermore, we demonstrated, for the first time, the vitrification (glass formation) of a perfectly round 6.5 mm sphere while cooling during levitation in a helium atmosphere in space. This signifies the clean process conditions available at the electromagnetic levitator on board the space station. Our results also show the capabilities of the facility to measure thermophysical properties needed to optimize and develop processes for new and better materials. Our findings also show the potential to use similar techniques for manufacturing processes of metallic glass in space.

Markus Mohr

Scientist, Ulm University