Utilising a laser-based 3D printing technique, researchers from the University of Massachusetts Amherst and the Georgia Institute of Technology have developed a nanostructured high-entropy alloy that is far more ductile and stronger than other state-of-the-art additively manufactured materials. This could pave the way for building higher-performance components used in aerospace, energy, medicine, and transportation. Such high entropy alloys (HEA) have gained popularity in material science. They have five or more elements in near-equal proportions and enable to create near-infinite number of unique combinations in designing alloys.
3D printing or additive manufacturing, meanwhile, is considered a powerful approach toward material development. Large temperature gradients and high cooling rates can be produced using this laser-based 3-D printing technique which is not possible to achieve through conventional methods.
In the new study, researchers combined the potential of HEA and a 3D printing technique called laser powder bed infusion to develop the new material. In the process, the materials melt and then solidify very rapidly as compared to traditional techniques. Due to this, according to Wen Chen, assistant professor of mechanical and industrial engineering at UMass, a very different kind of microstructure is obtained which is far from equilibrium on the components used.
The microstructure thus created has a structure of a net and consists of alternating layers called face-centred cubic (FCC) and body-centred cubic (BCC) nanolamellar structures embedded in the microscale eutectic colonies having random orientations. The hierarchical nanostructured property of the HEA allows for co-operative deformation of the two phases.
“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 Chen. He is also the lead author of the study published in Nature.
The professor added that, unlike the conventional metal casting, they were able to achieve triple the strength level and that too without using the ductility. “For many applications, a combination of strength and ductility is key. Our findings are original and exciting for materials science and engineering alike,” Chen added.
Researchers highlighted that the study showed 3D printed materials were more robust when it comes to resisting applied deformations. This, according to the team, is crucial in lightweight structural design for energy saving and enhancing mechanical efficiency.