Kuo, I.Y., B. Hete, and K.K. Shung, , “A Novel Method for the Measure- ment of Acoustic Speed,” The Journal of the Acoustical Society of America, Vol. , https://doi.org/./. Kupperman, D.S., and K.J. Reimann, , “Ultrasonic Wave- Propagation Characteristics and Polarization Effects in Stainless Steel Weld Metal,” Technical Report, Argonne National Laboratory, https://doi.org/./ Kurgan, N., , “Effect of Porosity and Density on the Mechanical and Microstructural Properties of Sintered L Stainless Steel Implant Mate- rials,” Materials & Design, Vol. , pp. –, https://doi.org/./j .matdes... Ledbetter, H.M., , “Austenitic-Steel Elastic Constants,” R.P. Reed and T. Horiuchi (eds), Austenitic Steels at Low Temperatures, Springer, Boston, MA, pp. –, https://doi.org/./----_ Lerch, T.P., R. Cepel, and S.P. Neal, , “Attenuation Coefficient Estima- tion Using Experimental Diffraction Corrections with Multiple Interface Reflections,” Ultrasonics, Vol. , pp. –, https://doi.org/./j .ultras... Lopez, A., R. Bacelar, I. Pires, T.G. Santos, J.P. Sousa, and L. Quintino, , “Non-destructive Testing Application of Radiography and Ultrasound for Wire and Arc Additive Manufacturing,” Additive Manufacturing, Vol. , pp. –, https://doi.org/./j.addma... Mandache, C., , “Overview of Non-destructive Evaluation Techniques for Metal-Based Additive Manufacturing,” Materials Science and Technology, Vol. , pp. –, https://doi.org/./.. Pinkerton, J.M.M., , “The Absorption of Ultrasonic Waves in Liquids and its Relation to Molecular Constitution,” Proceedings of the Physical Society. Section B, Vol. , https://doi.org/./-/// Qu, J., and M. Cherkaoui, , Fundamentals of Micromechanics of Solids, John Wiley & Sons Inc., https://doi.org/./ Slotwinski, J.A., E.J. Garboczi, and K.M. Hebenstreit, , “Porosity Measurements and Analysis for Metal Additive Manufacturing Process Control,” Journal of Research of the National Institute of Standards and Technology, Vol. , pp. –, http://dx.doi.org/./jres.. Sotelo, L.D., H. Hadidi, C.S. Pratt, M.P. Sealy, and J.A. Turner, , “Ultra- sonic Mapping of Hybrid Additively Manufactured  Stainless Steel,” Ultrasonics, Vol. , https://doi.org/./j.ultras.. Thompson, A., I. Maskery, and R.K. Leach, , “X-ray Computed Tomog- raphy for Additive Manufacturing: A Review,” Measurement Science Tech- nology, Vol. , https://doi.org/./-/// Wilson-Heid, A.E., T.C. Novak, and A.M. Beese, , “Characterization of the Effects of Internal Pores on Tensile Properties of Additively Manu- factured Austenitic Stainless Steel L,” Experimental Mechanics, Vol. , pp. –, https://doi.org/./s--- Yu, L., Y. Guo, F.J. Margetan, and R.B. Thompson, , “Effect of Microstructure on Backwall Signal Attenuation Measurements Using Focused Transducers,” AIP Conference Proceedings, Vol. , https://doi. org/./. Zhu, Y., Z. Wu, W. Douglas Hartley, J.M. Sietins, C.B. Williams, and H.Z. Yu, , “Unraveling Pore Evolution in Post-Processing of Binder Jetting Materials: X-ray Computed Tomography, Computer Vision, And Machine Learning,” Additive Manufacturing, Vol. , https://doi.org/./j. addma.. ME | BINDERJETAM 44 M A T E R I A L S E V A L U A T I O N • A P R I L 2 0 2 2

NDTREVIEWPAPER | ME A PERSPECTIVE OF THE NEEDS AND OPPORTUNITIES FOR COUPLING MATERIALS SCIENCE AND NONDESTRUCTIVE EVALUATION FOR METALS-BASED ADDITIVE MANUFACTURING BY M.J. QUINTANA*†, Y. JI*‡, AND P.C. COLLINS*†‡§ ABSTR ACT This paper presents a perspective of the needs and opportunities associated with the multidisciplinary problem of nondestructive evaluation (NDE) of additive manufacturing (AM). Recognizing the multidisciplinary nature of the problem, as well as the need to bridge knowledge between the different communities, the paper is structured to provide brief backgrounds and details relevant to both communities, as well as present an assessment of the state of the art. This paper, in some respects, is meant to be a primer of the different landscapes, as well as a catalyst for making future connections. At the end, it will be clear that there is much more work to be done, but that the work that is ongoing is exciting, and the potential to exploit NDE techniques for metals-based AM is very high. KEYWORDS: additive manufacturing, nondestructive evaluation, materials state, measurement techniques, materials physics Introduction Increasingly, there is an awareness that the paradigm-changing nature of additive manufacturing (AM) requires a reassess- ment of both materials science and nondestructive evaluation (NDE). Traditionally, these technical specialties/disciplines are separated, as their role in the development, manufac- ture, and use of parts and components in advanced technical systems, such as vehicles, aircraft, defense, and energy systems, is notably different. However, it is also becoming clear that there is a significant opportunity if these traditionally separate subject matter experts can collaborate in the area of AM. The causes associated with why these technical experts are separated is worth a brief discussion. First, there is the typical role that these experts play in any organization. A materials scientist plays important roles in the development and opti- mization of new materials, often long before those materials are qualified and become part of the design and manufacturing ecosystem. A materials engineer may then be highly involved in certain aspects of the manufacturing ecosystem, providing subject matter expertise related to process controls and destruc- tive testing to assure specific metrics of quality (for example, mechanical testing or microscopy). The NDE experts often receive a handoff of parts and components, and then apply their skill sets to ensure that the quality of parts is known to an acceptable degree of uncertainty, monitoring parts over their lifetime in service. In certain organizations, the NDE experts can play a role in the design of the parts if philosophies such as design for inspectability are part of the organization’s culture. Second, there are the types of data these different subject matter experts typically manage. For the materials scientist or engineer, the spatial domain dominates the characterization techniques, enabling the direct observation of grains, texture, precipitates, and defects. For the NDE expert, the tools invariably rely upon measurements involving time, and are thus in the frequency domain, which can be converted into the spatial domain using various techniques. Lastly, the NDE experts are trained to use statistics (that is, probability of detection) to pursue rare events and are, by their occupation, risk averse. Conversely, the research of many materials scientists is primarily focused on the initial stages of new materials development, where it is not uncommon to imagine in an almost unbridled sense the possi- bilities of the new materials under study. * Department of Materials Science and Engineering, Iowa State University, Ames, IA 50011, USA † The Center for Advanced Nonferrous Structural Alloys, a joint NSF I/UCRC between Iowa State University and the Colorado School of Mines ‡ The Center for Nondestructive Evaluation, a graduated NSF I/UCRC § Ames Laboratory, Ames, IA 50011, USA pcollins@iastate.edu Materials Evaluation 80 (4): 45–63 https://doi.org/10.32548/2022.me-04256 ©2022 American Society for Nondestructive Testing A P R I L 2 0 2 2 • M A T E R I A L S E V A L U A T I O N 45