An Indestructible New Alloy Is Defying the Limits of Metal
The material might just revolutionize modern manufacturing.
- A new alloy combines the best of the refractory metals with cutting-edge engineering.
- Even these extremely tough metals can be made to deform and show bands of adjustment.
- These kink bands add strength through subtle shifts in the crystal structure, reducing brittleness.
In newly published research, scientists have revealed a special alloy that could change the game with its combination of temperature tolerance, resistance to wear, and previously unheard of fracture toughness. How do you make one alloy that has it all? The secret is a feature called a kink band, where the material naturally forms a certain way as it is heated and treated. As the saying goes, sometimes our flaws can lead to our greatest strengths. Turns out that’s also true for exotic alloys.
Many metals are soft in their pure form—or, at least, softer than we’d like them to be for applications like manufacturing and heavy machinery. Long ago, humans realized they could combine two metals into one alloy (like bronze) and get results that were tougher, held a sharp edge better, and lasted longer.
Why are alloys so strong? Well, each element has its own atomic mass and particle size. Think about a pure metal like a game of Jenga. When you push on a block (or deform your metal), you know how that block is going to move. But in an alloy, your Jenga tower is built from blocks of different sizes, meaning it’s much harder to simply “push” (deform) them out of place. There are fewer of the neat lines that are prone to breakage.
In this new paper, researchers from Lawrence Berkeley National Laboratory and a handful of west coast universities collaborated on a new refractory alloy. Refractory—used colloquially to mean stubborn—in this case means an alloy that is extremely tolerant of very high heat. They’re made by combining metals from the fifth and sixth period of the periodic table of elements: molybdenum, niobium, tungsten, tangalum, and rhenium.
These elements have some of the highest melting points in the known periodic table. They also have very high hardness among the pure metals—although if we’re talking about materials in general, diamond still leaves them in the dust. That means when alloyed in a particular way, these metals (along with a few others with high melting points, like titanium and iridium) can become even more resistant to heat and wear, forming the family of refractory alloys.
There’s just a few problems. The same toughness and hardness that defines the refractory alloys often means they’re literally too hard to work with, with low ductility and a high likelihood of fracture. In other words, if you’re trying to metalwork a refractory alloy into any kind of shape, it will break instead of bend. We needed to find a middle ground where a very hard refractory alloy could take a hit and deform in the desired way rather than fracturing.
To do this, the Berkeley Lab scientists “specifically engineered” an alloy of niobium, tantalum, titanium, and hafnium, and formed kink bands in the metal. Inside a solid material like an alloy, kinks and jogs are terms referring to types of flaws that affect the alloy’s structure. Their details are more scientific, but a kink in a power cable or a street that jogs over a bit give you the intuitive idea. While the alloy forms, its crystal structures move around just enough to create these “stretch marks” or seams that show a change in crystal orientation.
In cables, a kink is often a sign of damage or unusual wear. In the crystals that we use as gemstones, a kink band might ruin the desired sparkly effect by disrupting how light passes through the material. But in the alloy, researchers found that the kink bands resulted from dislocation tolerance—meaning deformability without breaking. The particles in the alloy were able to adapt to a space where the crystals had shifted around, and those bands of adaptation made the results stronger.
“Our work shows that contrary to conventional understanding, complex concentrated refractory alloys can possess exceptional fracture toughness across extreme temperature ranges, even in the cryogenic regime,” the scientists conclude. The next step is more research, since this is just one exploratory paper.
But in a world waiting on new technologies like quantum computing and nuclear fusion, the cryogenic regime—where materials are cooled to near absolute zero—is vital. The stronger we can make those materials, the better.