Rustproof alloy discovered accidentally
Researchers have discovered a rustproof, ultralight alloy that could lead to improved fuel efficiency and reduced greenhouse gas emissions. The magnesium-lithium alloy weighs half as much as aluminium and is 30% lighter than magnesium, making it a suitable candidate to replace commonly used metals in vehicles.
Most excitingly, the high-strength alloy forms a protective layer of carbonate-rich film on exposure to air, making it immune to corrosion. This corrosion resistance was observed by chance, when a team comprising UNSW and Monash University researchers noticed a heat-treated sample from a Chinese aluminium-production giant, CHALCO, sitting inert in a beaker of water in their laboratory.
“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,” said Professor Michael Ferry, from UNSW’s School of Materials Science and Engineering.
The team partnered with scientists on the powder diffraction (PD) beamline at the Australian Synchrotron to confirm that the alloy contains a unique nanostructure that enables the formation of a protective surface film. The results of their study have since been published in the journal Nature Materials.
The researchers have now turned their attention to investigating the molecular composition of the underlying alloy and the carbonate-rich surface film, to understand how the corrosion process is impeded. Professor Nick Birbilis, from the School of Materials Science and Engineering at Monash University, said viewing unprecedented structural detail of the alloy through the Australian Synchrotron will enable the team to work towards commercialising 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,” Professor Birbilis said.
“These panels will make many vehicles and consumer products much lighter and, eventually, just as durable as today’s corrosion-resistant stainless steel.”
The research team also includes researchers from CHALCO and Nanjing Tech University in China.
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