Nanoparticles Make Metals Both Strong And Flexible

Strong alloys are typically less ductile, and vice-versa. Researchers have managed to overcome this tradeoff by including nanoparticles in the alloy fabrication process.

AsianScientist (Dec. 6, 2018) – Scientists in Hong Kong have developed a strategy for creating alloys that are extremely strong yet ductile and flexible. They published their findings in Science.

Multiple-principal element alloys, generally referred as high-entropy alloys (HEAs), are a new type of material constructed with equal or nearly-equal quantities of five or more metals. However, most of these alloys share a critical flaw—the higher their strength, the less the ductile they are, which means that strong alloys tend to be less deformable and fracture when stretched.

In this study, researchers led by Professor Liu Chain Tsuan of the City University of Hong Kong devised a method to fabricate HEAs that are not subjected to the strength-ductility tradeoff. They achieved this by adding nanoparticles made of nickel, cobalt, iron, titanium and aluminium atoms to the alloy.

“We are able to make a new high-entropy alloy called Al7Ti7 ((FeCoNi)86-Al7Ti7) with a strength of 1.5 gigapascals and ductility as high as 50 percent at ambient temperature. Strengthened by nanoparticles, this new alloy is five times stronger than that of the iron-cobalt-nickel (FeCoNi)-based alloy,” said Liu.

Liu believes that the alloys developed with this strategy will perform well in temperatures ranging from -200°C to 1,000°C. Hence, they form the foundation for further development of cryogenic devices, aircraft and aeronautic systems, among other applications.

“This research opens up a new design strategy to develop superalloys, by engineering multicomponent nanoparticles to strengthen complex alloys to achieve superb mechanical properties at room and elevated temperatures,” said Liu.

The article can be found at: Yang et al. (2018) Multicomponent Intermetallic Nanoparticles and Superb Mechanical Behaviors of Complex Alloys.


Source: City University Hong Kong.
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