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Researchers create exceptionally strong and lightweight new metal

24 December 2015

A team of US researchers has created a super-strong yet light structural metal with extremely high specific strength and modulus, or stiffness-to-weight ratio.

Left: a deformed sample of pure metal; right: the strong new metal made of magnesium with silicon carbide nanoparticles. Each central micropillar is about 4 micrometres across (image: UCLA Scifacturing Laboratory)

The new metal is composed of magnesium infused with a dense and even dispersal of ceramic silicon carbide nanoparticles. It could be used to make lighter aircraft, spacecraft, and cars, helping to improve fuel efficiency, as well as in mobile electronics and biomedical devices.

To create the super-strong but lightweight metal, the University of California at Los Angeles team found a new way to disperse and stabilise nanoparticles in molten metals. They also developed a scalable manufacturing method that could pave the way for more high-performance lightweight metals.

"It's been proposed that nanoparticles could really enhance the strength of metals without damaging their plasticity, especially light metals like magnesium, but no groups have been able to disperse ceramic nanoparticles in molten metals until now," says lead researcher, Xiaochun Li. "With an infusion of physics and materials processing, our method paves a new way to enhance the performance of many different kinds of metals by evenly infusing dense nanoparticles."

The researchers' technique of infusing a large number of silicon carbide particles smaller than 100 nanometres into magnesium adds significant strength, stiffness, plasticity and durability under high temperatures. Ceramic particles have long been considered as a potential way to make metals stronger. However, with microscale ceramic particles, the infusion process results in a loss of plasticity.

Nanoscale particles, by contrast, can enhance strength while maintaining or even improving metals' plasticity. But nanoscale ceramic particles tend to clump together rather than dispersing evenly, due to the tendency of small particles to attract one other.

To counteract this issue, the researchers dispersed the particles into a molten magnesium zinc alloy. The newly discovered nanoparticle dispersion relies on the kinetic energy in the particles' movement, which stabilises their dispersion and prevents clumping.

To further enhance the new metal's strength, the researchers used a technique called high-pressure torsion to compress it.

"The results we obtained so far are just scratching the surface of the hidden treasure for a new class of metals with revolutionary properties and functionalities," says Li.

The new metal (more accurately called a metal nanocomposite) is about 14 percent silicon carbide nanoparticles and 86 percent magnesium. 

The research is described in a paper, published in the journal, Nature.


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