World-first 'super alloy' is 2x as strong as steel

Combining metals to produce alloys that are stronger or tougher requires extremely high temperatures as part of the process. Researchers in Australia recently found that a radically different approach could yield even better alloys with a lot less heat.

Engineers at Monash University have created the first ever large piece of Refractory High-Entropy Alloy (RHEA). This alloy is not only twice as strong as steel with a compressive yield strength of more than 2 gigapascals, but it's also the result of a method that uses lower temperatures, and that could be easier and cheaper to scale.

The RHEA is composed of titanium, hafnium, tantalum, niobium and zirconium. Thanks to a slower heating process at a lower temperature than what you'd apply to melt metals in conventional alloy production, the atoms of these elements organized themselves into a strongly connected structure comprising three distinct components with nanocrystals in different periodic arrangements.

Professor Jian-Feng Nie, one of the authors of the RHEA paper that appeared in Science this month, said that last bit is the major discovery here: "... 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."

This is wholly different from the way alloys have been developed in the past, where composition has been the primary focus. The "atomic architecture" that resulted from the team's controlled heating process made for a defect-free product; the alloy is also ductile, which means it can be stretched, drawn, or deformed without breaking.

Beyond this one RHEA, the scientists' work could help pave the way for "more efficient, sustainable and cost-effective alloy production," as well as the development of more novel materials with specific capabilities enhanced to far greater degrees than before.

"The implications could be felt for decades to come, from aerospace and energy systems to advanced manufacturing and technologies that have yet to be imagined," said Professor Yiannis Ventikos from Monash.

As you'd expect, there's plenty of work ahead on this for the researchers. The current focus is on the atomic-scale interactions that cause these nanostructures to form the way they do, so they can understand how the materials evolve and perform throughout the heating process.

Source: Monash University