The Blue Dot mission saw the installation of the electromagetic levitator on the International Space Station in ESA’s Columbus laboratory. This is a furnace that can heat metals up to 2100°C and then cool them rapidly. Blacksmiths have been using this technique for centuries, creating steel tools and weapons by heating, hammering and quenching in water. This process sets the steels structure and causes it to be hard and stay sharp.
Understanding the underlying physics of this simple example is complicated and factors such as gravity and the mould used to hold the metal in place influence the process making it difficult to get to the fundamentals. For example, gravity pulls on atoms in different ways and heat is transferred to the mould.
For scientists observing liquid metals cooling in weightlessness removes unnecessary complexity to reveal the core processes of physics. 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.
The electromagnetic levitator arrived at the Space Station after Alexander on Europe’s ATV-5 space freighter. Alexander installed the 360 kg unit ready for his colleague ESA astronaut Samantha Cristoforetti to use.
Most of the metals we use are not pure but alloys of different materials. By combining different metals, scientists and metalsmiths can concoct materials that offer the best of their component parts. The stainless steel used in knives and forks is actually an alloy of one part chromium to 10 parts steel that is resistant to corrosion.
Super-alloys using the latest space technology are now being used in smartphones and jet engines but scientists and industrial partners are always looking for better, lighter, stronger, cheaper materials.
Some metals and materials do not mix easily. Coolcop investigates cobalt and copper, two metals that do not mix easily on Earth. By observing the process in the electromagnetic levitator and looking specifically at surface tension, scientists and ESA’s industrial partners hope to improve casting processes on Earth.
This experiment uses the electromagnetic levitator’s high-speed camera to observe magnetic alloys such as iron, cobalt and nickel. Of particular interest for this experiment is the instant when a material reaches a new state such as liquid or solid.
Metcomp investigates how weightlessness affects the metallic structure of a nickel–titanium alloy. When particles come into contact with a liquid they can be pushed away or engulfed, like a ball floating on the sea. Depending on the size of an incoming wave, the ball could be pushed forwards like a surfer or be submerged. A similar process occurs with metals on an atomic scale as they come into contact with other liquid metals. Understanding this process better could lead to more exotic metal alloys or improve existing complex alloy creation.
Nequisol will focus on the microscopic structure of nickel–aluminium and aluminium–copper alloys as they form around a needle inserted into their liquid form. The alloys will grow like sugar crystals on a stick and scientists are eager to assess the speed of growth in weightlessness.
This experiment takes a closer look at a material that helped cell phones become ubiquitous: silicon–germanium semiconductors. These computer chips are found in almost all smartphones, and creating them requires forming the alloy at specific temperatures. Semitherm is set to investigate the underlying properties of a mix of silicon and germanium as it liquifies and melts in microgravity to see how weightlessness affects the end results.
Thermolab will improve models to help industrial casting and solidification techniques. It investigates the temperature and physical properties of industrial alloys in weightlessness in their liquid state. Industrial partners are keen to know more as the results could help them create existing alloys quicker, cheaper and with less waste.