This video shows an alloy of iron, chromium and nickel solidifying in weightlessness. It was taken with the high-speed camera that is part of ESA’s Electromagnetic levitator (EML) on the International Space Station.
The solidification moves from the bottom to the top of the video. The brighter part is the solidified sample, the darker part is still liquid.
The levitator is a furnace that can heat metals up to 2100°C and then cool them rapidly. Observing liquid metals cooling in weightlessness reveals the core processes of physics, without gravity interfering with results. The electromagnetic levitator takes things a step further and suspends the metals in mid-air as they melt and solidify.
Astronaut load the levitator with cartridges holding the metals. The microgravity furnace takes care of the rest, processing the metals and recording data automatically. The metals can be heated in a vacuum or in a gas. A high-speed camera records the forging and sensors record the temperature and other variables. The metals formed are retrieved and returned to Earth for analysis.
Read more about the Electromagnetic levitator: http://www.esa.int/Our_Activities/Human_Spaceflight/Blue_dot/Electromagnetic_levitator