A team of researchers has 3D-printed a dual-phase, nanostructured high-entropy alloy (HEA) that surpasses the strength and ductility of other state-of-the-art additively manufactured materials. The advance may lead to higher-performance components for applications in aerospace, medicine, energy, and transportation. The work was completed by researchers from the University of Massachusetts Amherst and the Georgia Institute of Technology.
HEAs have become increasingly popular in materials science over the past 15 years; they comprise at least five elements in near-equal proportions and offer the ability to create a near-infinite number of unique combinations for alloy design. Whereas traditional alloys contain a primary element combined with one or more trace elements.
“The potential of harnessing the combined benefits of additive manufacturing and HEAs for achieving novel properties remains largely unexplored,” said the team’s Co-Lead Ting Zhu, Professor of Mechanical Engineering at Georgia Tech.
The team combined an HEA with a state-of-the-art 3D-printing technique — laser powder bed fusion — to develop new materials with unprecedented properties. Since the process causes materials to melt and solidify very rapidly compared to traditional metallurgy, “you get a very different microstructure that is far-from-equilibrium” on the components created, said Wen Chen, Assistant Professor of Mechanical and Industrial Engineering at UMass.
This microstructure looks like a net and is made of alternating layers known as face-centered cubic (FCC) and body-centered cubic (BCC) nanolamellar structures embedded in microscale eutectic colonies with random orientations. The hierarchical nanostructured HEA enables 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,” Chen said. Compared to conventional metal casting, “we got almost triple the strength and not only didn’t lose ductility, but actually increased it simultaneously. For many applications, a combination of strength and ductility is key. Our findings are original and exciting for materials science and engineering alike.”
The Georgia Tech team led the computational modeling for the research. It developed dual-phase crystal plasticity computational models to understand the mechanistic roles played by both the FCC and BCC nanolamellae and how they work together to give the material added strength and ductility.
In the future, harnessing 3D-printing technology and the vast alloy design space of HEAs opens ample opportunities for the direct production of end-use components for biomedical and aerospace applications.