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US team 3D-prints ‘nanostructured, high-entropy’ alloys

04 Aug 2022

Such ultrastrong and ductile high-performance materials have applications in aerospace, medical industries.

Researchers at the University of Massachusetts Amherst and Georgia Institute of Technology have 3D-printed a dual-phase, “nanostructured, high-entropy” alloy that exceeds the strength and ductility of other additively manufactured materials, which, they say, could lead to higher-performance components for applications in aerospace, medicine, energy and transportation.

The work, led by Wen Chen, assistant professor of mechanical and industrial engineering at UMass, and Ting Zhu, professor of mechanical engineering at Georgia Tech, is described in Nature.

Over the past 15 years, high entropy alloys (HEAs) have become increasingly popular in materials science innovations. Comprising five or more elements in near-equal proportions, they offer the ability to create a near-infinite number of combinations for alloy design.

Laser-based 3D printing can produce large temperature gradients and high cooling rates that are not readily accessible by conventional manufacturing methods. However, “the potential of harnessing the combined benefits of additive manufacturing and HEAs for achieving novel properties remains largely unexplored,” commented Zhu.

Chen and his team in the Multiscale Materials and Manufacturing Laboratory combined an HEA with laser powder bed fusion to develop new materials. Because the process causes materials to melt and solidify very rapidly as compared to traditional metallurgy, “you get a very different microstructure that is far-from-equilibrium” on the components created, said Chen.

This microstructure resembles a net and is made of alternating layers of face-centered cubic (FCC) and body-centered cubic (BCC) nanolamellar structures. This enables co-operative deformation of the two phases. Chen added that, compared to conventional metal casting, “we got almost triple the strength and not only didn’t lose ductility, but actually increased it. Our findings are original and exciting for materials science and engineering alike.”

‘Resisting deformation’

“The ability to produce strong and ductile HEAs means that these 478 3D-printed materials are more robust in resisting applied deformation, which is important for lightweight structural design for enhanced mechanical efficiency and energy saving,” says Jie Ren, Chen’s Ph.D. student and first author of the paper.

Zhu’s group at Georgia Tech led the computational modeling for the research. He 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 addition, stated the team, 3D printing offers a powerful tool to make geometrically complex and customized parts: “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,” said the group’s announcement.

Additional research partners on the paper include Texas A&M University, the University of California Los Angeles, Rice University, and Oak Ridge and Lawrence Livermore national laboratories.

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