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Metal alloys are used everywhere from aircraft to cutlery, making them an indispensable part of modern life.
Scientists are continuing to try to find ways to improve them – which often comes down to the way they're initially formed.
Steel is one of the classic alloy examples: mostly iron with a dash of carbon and other elements, making it much stronger and harder than iron on its own.
Now, an international team of researchers has come up with a new way of building alloys. The method, described in a new paper published in Science, promises to make metals that are several times stronger than the materials we rely on today.
The trick is using lower, more controlled temperatures than is normal for alloy manufacturing, and letting the metal 'bake' for a specific period.
This leads to a more stable and ordered configuration of atoms, set in blocks known as grains, that are both smaller and more well-packed than usual.
"For more than a century, alloy development has focused on composition and processing," says materials scientist Jian-Feng Nie from Monash University in Australia.
"Our work suggests that how atoms organize during manufacturing may be just as important.
"The real significance is not just this particular alloy, but the demonstration that atoms can self-organize into defect-free structures in a bulk metallic material, meaning a large, continuous piece of metal, not a thin coating, film or microscopic sample."
That note on scaling is important – the idea of smaller, better-organized grains has been explored before, but scaling it up into something usable is challenging.
In the new study, the researchers mixed five metals together: hafnium, niobium, tantalum, titanium, and zirconium. After a brief high-temperature melting stage, the alloy was dropped to a relatively low 550 °C (1,022 °F) and left for several hours and even days.
At around 32 hours was when the researchers got their best result: a 'super alloy' called a Refractory High-Entropy Alloy (RHEAD).
It's two times stronger than steel, three times stronger than aluminum, and twice as strong as the same alloy made in a conventional way.
"By carefully controlling how the atoms organize during processing, we were able to create a highly connected structure with exceptional strength and stability," says materials scientist Yu Zhang from Chongqing University in China.
Both the choice of metals and the method of preparation create the conditions for the alloy atoms to organize themselves into repeating grain patterns, responding to the natural stresses between the mixed materials to create a structure free from defects.
That organization, plus the lack of defects and gaps between the recurring grains, is what gives the added strength.
Tests showed the new alloy achieved a compressive yield strength of more than two gigapascals while retaining its ductility, meaning it bends without breaking.
"If this concept can be applied more broadly, it could open the door to materials with properties that were previously considered unattainable, with implications for alloy design that could be applied across many systems and industries," says Nie.
"Instead of increasing alloy content to achieve better performance, we may be able to design internal structures that deliver superior properties with fewer alloying elements. That could lead to more efficient, sustainable, and cost-effective alloy production."
The researchers say their discoveries open up a wealth of possibilities for future manufacturing, in everything from aerospace to energy systems – and even technologies that haven't been imagined yet.
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There's a lot more work to do though. Next, the team wants to understand not just what the atoms are doing in terms of rearranging themselves, but why they're doing it, which should enable this new technique to be expanded and refined.
"For more than a century, advances in alloys have come from altering the chemical composition and processing, guided largely by empirical trial and error," says Yiannis Ventikos, the Dean of Engineering at Monash University, who was not directly involved in the study.
"This research suggests we can actually engineer how atoms organize themselves, creating opportunities to develop materials with capabilities that were previously out of reach."
The research has been published in Science.
This article was fact-checked by Clare Watson and edited by Peter Dockrill. While we pride ourselves on our process, we are only human. If you spot a mistake, please let us know.
