With new manufacturing techniques comes the opportunity for brand new metal alloys with a huge range of possible properties. A team of researchers has now developed a new 3D-printable alloy with a specific nanostructure that makes it ultra strong and ductile.
Most common alloys, like stainless steel or bronze, are made with one primary metal mixed with smaller amounts of other elements. But an emerging class of materials known as high entropy alloys (HEAs) involves mixing five different elements together in roughly equal proportions. The resulting alloys end up with intriguing and useful properties, like high strength-to-weight ratios and stiffness that rises with the temperature.
The new study focuses on a HEA containing aluminum, cobalt, chromium, iron and nickel in equal measures. This particular mix has been experimented with for a few years now, but the team made it using a technique that hadn’t been applied to it yet – laser powder bed fusion. Essentially, powdered forms of the original metals are laid out on a surface, then blasted with a high-powered laser that causes them to rapidly melt and resolidify.
This technique, a form of 3D printing, gives the final alloy a very different microstructure than it gets from other manufacturing methods. The team describes it as looking like a net, with alternating layers of different cubic crystalline structures. This gives the HEA a yield strength of around 1.3 Gigapascals, almost three times stronger than when it’s made using conventional casting methods. At the same time, it’s also more ductile, countering a common trade-off.
“This unusual microstructure’s atomic rearrangement gives rise to ultrahigh strength as well as enhanced ductility, which is uncommon, because usually strong materials tend to be brittle,” said Wen Chen, lead researcher on the study. “For many applications, a combination of strength and ductility is key. Our findings are original and exciting for materials science and engineering alike.”
This specific combination of strength and ductility could make this alloy useful for components in aerospace, energy, transportation or other engineering fields.
The research was published in the journal Nature.
Source: Georgia Tech
