Saarland Team to Levitate Molten Metal Alloys on the ISS to Refine 'Metallic Glass'

A research team led by materials scientist Ralf Busch of Saarland University in Germany is preparing to study metallic-glass alloys aboard the International Space Station for the first time. Working with the European Space Agency (ESA) and the German Aerospace Center (DLR), the team will remotely run week-long experiments from August 31, melting droplets of the alloys without a container and observing them as they levitate in near-weightlessness.

Metallic glasses are metals that solidify with a disordered, glass-like atomic structure instead of the regular lattice found in ordinary crystalline metals. Despite the name, they are not fragile: Busch says the alloys are stronger than steel, elastic, and can be shaped like plastics at high temperatures using techniques such as injection molding or metal 3D printing. His lab holds several patents for such ultra-high-strength alloys, which are being developed for uses including more energy-efficient electric-motor components and complex parts for aerospace applications.

Producing an alloy that solidifies into a disordered, glass-like state rather than crystallizing takes years of fine-tuning its atomic composition, Busch said, describing the work as designing within "a multidimensional compositional space" to find combinations that crystallize more slowly. The ISS environment lets molten droplets remain stable and stationary for measurement — something gravity makes difficult on Earth — because the orbiting station is in continuous free fall around the planet.

The experiments, scheduled to run from August 31 to September 4, will focus on nickel-niobium and nickel-niobium-sulfur alloys heated to temperatures of up to 1,700 degrees Celsius (3,100 degrees Fahrenheit). The nickel-niobium alloy was first developed at the Massachusetts Institute of Technology in 1967, while the nickel-niobium-sulfur alloy comes from Busch's own laboratory in Saarbrücken. A follow-up series of ISS experiments involving other alloys is already in preparation.