First 3D-printed High-performance Nanostructured Alloy Combines Ultra-strength And Ductility

A team of scientists has 3D printed a dual-phase nanostructured high-entropy alloy that surpasses other state-of-the-art additive manufacturing materials in strength and ductility. This breakthrough could lead to higher performance components for applications in aerospace, medicine, energy and transportation. The work was done by researchers at the University of Massachusetts Amherst and Georgia Tech. Led by Wen Chen, associate professor of mechanical and industrial engineering at UMass Amherst, and Ting Zhu, professor of mechanical engineering at Georgia Tech, it was published Aug. 3 in the journal Nature.

Over the past 15 years, high-entropy alloys (HEAs) have grown in popularity as a new paradigm in materials science. They are composed of five or more elements in near equal proportions, giving alloy designs the ability to create nearly limitless unique combinations. Traditional alloys, such as brass, stainless steel, carbon steel and bronze, contain a combination of one major element and one or more trace elements.

3D printing, also known as additive manufacturing, has recently emerged as a powerful material development method. Laser-based 3D printing can generate large temperature gradients and high cooling rates, which cannot be achieved by conventional approaches. However, "the potential of leveraging the combined advantages of additive manufacturing and HEA to achieve new properties is largely untapped," Zhu said.

Wen Chen and his team in the UMass Multiscale Materials and Manufacturing Laboratory combined HEA with the state-of-the-art 3D printing technology, laser powder bed fusion, to develop new materials with unprecedented properties. Because the process melts and solidifies the material very quickly compared to traditional metallurgical processes, "you get a very different microstructure that's far from equilibrium," Chen said. This microscopic structure looks like a web, consisting of alternating layers of nanostar structures known as face-centered cubic (FCC) and body-centered cubic (BCC), embedded in microscopic eutectic crystals with random orientations group. The hierarchical nanostructured HEA enables the cooperative deformation of the two phases.

Chen Wen said: "The atomic rearrangement of this unusual microstructure produces ultra-high strength as well as enhanced ductility, which is uncommon because generally strong materials tend to be brittle. This is in contrast to traditional metal casting. ratio, we get almost three times the strength, not only without losing ductility, but actually increasing ductility at the same time. For many applications, the combination of strength and ductility is key. Our findings have implications for both materials science and engineering It's original and exciting."

"The ability to produce HEAs with high strength and ductility means that these 3D printing materials are stronger in resisting applied deformation, which is important for the design of lightweight structures with improved mechanical efficiency and energy savings," said Jie Ren, the paper's first author.

Ting Zhu's group at Georgia Tech led the computational modeling for the study. They developed a computational model of the plasticity of the two-phase crystals to understand the mechanical role played by the FCC and BCC nanoparticles and how they work together to give the material increased strength and ductility.

"Our simulation results show the surprising strength and hardening response of BCC nanoparticles, which are key to achieving the excellent synergy of strength and ductility in our alloys." Zhu Ting said, "This mechanistic understanding can guide future The development of 3D printed HEAs with special mechanical properties provides an important foundation."

Furthermore, 3D printing provides a powerful tool to manufacture geometrically complex and custom parts. In the future, leveraging 3D printing technology and the huge alloy design space of HEA offers numerous opportunities for the direct production of end parts for biomedical and aerospace applications.