In the quest for more efficient commercial aircraft to help reduce fuel consumption, weight reduction without compromising safety is one of the most obvious areas of focus. Researchers at the European Space Agency (ESA) working in the Intermetallic Materials Processing in Relation to Earth and Space Solidification (IMPRESS) Project have used hypergravity to help develop an aircraft-grade alloy they claim is twice as light as the nickel superalloys currently used in conventional jet engines, but boasts equally good properties.
According to the ESA, reducing the weight of an aircraft by one percent will generally result in a 1.5 percent reduction in fuel usage. This might not sound like much, but quickly adds up to significant financial savings for commercial airlines and benefits for the environment.
Titanium aluminide alloys, which are lighter than nickel superalloys and can withstand temperatures of up to 800° C (1,472° F), have long been of interest to aircraft engine manufacturers. However, the difficulties faced in casting the material into shapes such as turbine blades has made it unsuitable for use in engines. Until now.
To gain a greater understanding of the natural processes that take place during casting, the ESA scientists heated aluminum samples to over 700° (1,292° F) in a small furnace carried on a sounding rocket and monitored the samples using X-rays as they were cooled during a six-minute free fall. The removal of external variables, such as gravity, is a common practice by scientists making observations so they can concentrate on the core interactions.
However, when the scientists looked at the results from the free fall observations, they thought they might have better luck opting for an opposite approach – hypergravity. To test their theory, the IMPRESS team turned to the ESA’s Large Diameter Centrifuge in the ESTEC research and technology center in the Netherlands.
They found that casting the metals in the centrifuge at up to 20 times normal gravity produces a perfectly cast alloy in even complex shapes. This is because the additional gravitational force helps the liquid metals fill every part of the mold. They say the experiments provided the foundation to allow them to refine and commercialize the industrial process used to manufacture the alloy.
The researchers say using titanium aluminide would reduce the weight of the more than one million jet turbine blades that are expected to be produced in the next eight years by over 45 percent. They add that the alloy is also of interest to the automotive industry, which could use it to create lighter car components.
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