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High-strength magnesium-lithium alloy weighs half as much as aluminum
January 01, 2016
Source: ASM International
The University of New South Wales and Monash University, Australia, announce that a team of researchers has developed a high-strength magnesium-lithium alloy with density of 1.4 g/cm3, 50% less than aluminum and 30% less than magnesium. The researchers have shown that the alloy forms a protective layer of carbonate-rich film upon exposure to air, making it immune to corrosion. The finding is published online in the 19 October edition of Nature Materials.
Prof. Michael Ferry, of UNSW's School of Materials Science and Engineering, says that the excellent corrosion resistance of the alloy was observed by chance, when the team noticed that a heat-treated sample in a beaker of salt water showed no corrosion after several hours. Normally magnesium would have been extensively corroded.
The researchers then designed a magnesium-lithium alloy of specific composition together with a processing sequence consisting of hot extrusion, heating and water quenching, low-temperature aging, and cold rolling.
"This is the first magnesium-lithium alloy to stop corrosion from irreversibly eating into the alloy, as the balance of elements interacts with ambient air to form a surface layer which, even if scraped off repeatedly, rapidly reforms to create reliable and durable protection," says Prof. Ferry.
The UNSW team partnered with scientists on the Powder Diffraction beamline at the Australian Synchrotron, to confirm that the alloy contains a unique nanostructure that enables the formation of a protective surface film.
Prof. Nick Birbilis (shown in the photo), School of Materials Science and Engineering at Monash University, says viewing unprecedented structural detail of the alloy through the Australian Synchrotron will enable the team to work toward commercializing the new metal.
‘We're aiming to take the knowledge gleaned at the Australian Synchrotron to incorporate new techniques into the mass-production of this unique alloy in sheets of varying thickness, in a standard processing plant," Prof. Birbilis said.
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