Even though these fundamental changes were measured at the nanoscale (in the terms of billionths of a meter), the consequences were certainly sizable. The aluminum alloy they used, known as aluminum 7075 was more than three times stronger than conventional aluminum and equal in strength to many of the strongest steels. A meter-squared plate of the processed alloy could withstand the weight of a fully loaded aircraft carrier.
To find out why the aluminum alloy had gotten so much stronger, the team examined the samples using a process called atom probe tomography. They found that the high-pressure torsion technique had changed the arrangement of the atoms within the metal. In the processed aluminum 7075 alloy, the size of the aluminum grains was reduced and the other atoms within the metal clustered together in groups. A phenomenon, according to the paper’s lead author Peter V. Liddicoat from the Australian Center for Microscopy and Microanalysis at the University of Sydney in Australia, that produced, “a hierarchy of structures that work synergistically to produce superior mechanical properties.”
When asked what makes this particular make-up so strong, co-author Simon Ringer, director of the Electron Microscope Unit at the University of Sydney, said, in a prepared statement, that the scientists were still unclear as to why this arrangement created a stronger aluminum, but that hierarchical structures are “very potent for strengthening.”
Scientists can easily create the alloy in the lab, but according to Dr. Xiashou Laio, co-author of the paper and mechanical engineer from the University of Sydney, at this stage of research, “the high-pressure torsion technique can only produce small sample sizes." Still, Liddicoat said that he expected large-scale production techniques to be developed by others in the future.
The aluminum is likely to be in high demand by industry. For example, the majority of a car’s weight is in its chassis, which is made of steel. If this were made of lightweight aluminum instead, you could cut the car’s weight in half, making it twice as efficient to drive, said Liddicoat.
“It’s good a starting point,” said Ryan Galego, a mechanical engineer for the US Navy, “If it did work on a big scale, you’d have something cheap, that was both light and corrosion resistant…a great building material.”
“The existing manufacturing processes may be difficult to scale up - but that’s fine!” said Liddicoat, “Research needs to explore things in simple and thorough ways…as we begin to understand the mechanics of materials better, we can then design better processing paths to achieve the same structure."