3D printed ultrastrong and ductile alloy developed by UMass Amherst and Georgia Tech

A team of researchers from University of Massachusetts Amherst (UMass) and Georgia Tech have 3D printed a dual-phase, nanostructured, high-entropy alloy that they say exceeds the strength and ductility of other state-of-the-art additively manufactured materials.

The research, led by Wen Chen, Assistant Professor of Mechanical and Industrial Engineering at UMass, and Ting Zhu, Professor of Mechanical Engineering at Georgia Tech, was published in the August issue of the journal Nature.

High entropy alloys (HEAs) have become increasingly popular as a new paradigm in materials science over the past 15 years. They are comprised of five or more elements in near-equal proportions and offer the ability to create a near-infinite number of unique combinations for alloy design.

Zhu said: “The potential for harnessing the combined benefits of additive manufacturing and HEAs for achieving novel properties remains largely unexplored.”

Chen and his team in the Multiscale Materials and Manufacturing Laboratory combined an HEA with laser powder bed fusion to develop new materials with unprecedented properties. 

“You get a very different microstructure that is far-from-equilibrium,” on the components created, said Chen. This is because of the process that causes materials to melt and solidify very rapidly compared to traditional metallurgy.

The microstructure looks like a net and is made of alternating layers known as face-centred cubic (FCC) and body-centred 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, Chen claims that almost triple the strength was achieved and the material didn’t only not lose ductility, but actually increased it simultaneously. 

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

Dual-phase crystal plasticity computational models were developed by the team. This helped them to understand the mechanistic roles played by both the FCC and BCC nano-lamellae and how they work together to give the material added strength and ductility.

Zhu said: “This mechanistic understanding provides an important basis for guiding the future development of 3D printed HEAs with exceptional mechanical properties.”

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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