X-rays reveal microstructural fingerprints of 3D-printed alloy

October 10, 2023

,nanowork news) Cornell researchers took a new approach to exploring how microstructures emerge in a 3D-printed metal alloy: They bombarded the material with X-rays while it was being printed.

key takeaways

Table of Contents

  • Researchers used X-rays during 3D printing of a metal alloy to study the evolution of its microstructure in real time.
  • This new approach provides insight into how microstructures are formed, which are critical to the performance of printed parts.
  • The findings could influence the development of stronger materials and provide a framework for optimizing 3D-printed metals for specific applications.
  • Research

    By observing how the process of thermomechanical deformation creates localized microscopic phenomena such as bending, fragmentation and oscillation in real time, researchers will be able to produce optimized materials that incorporate such performance-enhancing characteristics.

    Group’s paper published communication material (“Dendritic distortion modes in additive manufacturing revealed by operando X-ray diffraction”). The lead author is doctoral student Adrita Das, MS ’20.

    “We always see these microscopic structures after processing, but only doing postmortem characterization misses a lot of information. We now have the tools to be able to see these microstructural evolutions, said Atieh Moridi, an assistant professor in the Sibley School of Mechanical and Aerospace Engineering at Cornell Engineering and senior author of the paper. “We want to be able to understand how these tiny patterns or microstructures are formed because they dictate everything about the performance of printed parts.”

    The group focused on a form of 3D printing in which a powder – in this case, nickel-based superalloy IN625, which is widely used in additive manufacturing and the aerospace industry – is applied through a nozzle and a Melted by a high-power laser beam, then cooled and solidified.

    Since access to high-energy X-rays is not possible in the laboratory, the researchers created a portable twin of their 3D-printing setup and brought it to the Center for High Energy At Wilson Laboratory.

    The facility had never conducted this type of 3D-printing experiment before, so CHESS beamline scientist Darren Pagan, now an assistant professor at Pennsylvania State University, worked with researchers to integrate the printer setup into one of the facility’s experiment hutches. Worked with. The CHESS team also developed critical safety protocols for handling flammable powders as well as high-powered lasers.

    During the experiment at the fast beamline, a focused X-ray beam was sent into the hutch, where it passed through IN625 as it heated, melted and cooled. A detector on the other side of the printer captured the patterns of diffraction resulting from the interaction of the X-rays with the material.

    “The way these diffraction patterns are formed gives us a lot of information about the structure of the material. They are microstructural fingerprints that capture the history of the material during processing,” Moridi said. “Depending on the interaction and what causes it, we get different patterns, and from those patterns, we can calculate the structure of the material.”

    Typically, researchers will attempt to consolidate a volume of diffraction data in order to analyze it. But Moridi, Das and doctoral student and co-author Chenxi Tian, ​​MS ’22, took on a more challenging task and studied raw detector images. Although this approach required more time and was more labor-intensive, it provided a richer, holistic picture of how IN625 took shape, revealing “the unique features that we are missing most of the time.” ,” Moridi said.

    The group identified key microstructural features that were created by the thermal and mechanical effects of the process, including: torsion, bending, fragmentation, assimilation, oscillation, and interplanetary growth.

    The researchers anticipate that their method could be applied to other 3D-printed metals, such as stainless steel, titanium and high-entropy alloys, or any material system with a crystal structure.

    The method could also help inform the development of stronger materials. For example, pulsing a laser beam will increase fragmentation inside the crystal and reduce its grain size, making the material stronger.

    “The ultimate goal is to get the best material system for that particular alloy for a particular application,” Das said. “If you know what’s happening during processing, you can choose how to process your materials so that you get those specific features.”

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