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The goal of this work is to detect flaw formation in the wire-based directed energy deposition (W-DED) process using in-situ sensor data. The W-DED studied in this work is analogous to metal inert gas electric arc welding. The adoption of W-DED in industry is limited because the process is susceptible to stochastic and environmental disturbances that cause instabilities in the electric arc, eventually leading to flaw for-mation, such as porosity and suboptimal geometric integrity. Moreover, due to the large size of W-DED parts, it is difficult to detect flaws post-process using non-destructive techniques, such as X-ray com-puted tomography. Accordingly, the objective of this work is to detect flaw formation in W-DED parts using data acquired from an acoustic (sound) sensor installed near the electric arc. To realize this objec-tive, we develop and apply a novel wavelet integrated graph theory approach. The approach extracts a single feature called graph Laplacian Fiedler number from the noise-contaminated acoustic sensor data, which is subsequently tracked in a statistical control chart. Using this approach, the onset of various types of flaws are detected with a false alarm rate less-than 2%. This work demonstrates the potential of using advanced data analytics for in-situ monitoring of W-DED.(c) 2022 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http:// creativecommons.org/licenses/by/4.0/). Fundacao para a Ciencia e a Tecnologia (FCT-MCTES) [UI/BD/151018/2021, UID/00667/2020]; FCT-Fundacao para a Ciencia e a Tecnologia, I.P. [LA/P/0037/2020, UIDP/50025/2020, UIDB/50025/2020]; European Institute of Innovation and Technology (EIT) - Project Smart WAAM: Microstructural Engineering and Integrated Non-Destructive Testing; European Union; Department of Energy (DOE), Office of Science [DE-SC0021136]; National Science Foundation (NSF) [CMMI-1719388, CMMI-1920245, CMMI-1739696, CMMI-1752069, PFI-TT 2044710, ECCS 2020246]; DOE; NSF [ECCS 2020246, CMMI 1752069]; [CMMI 1920245]; [ECCS: 2025298] Published version Andre Ramalho acknowledges Fundacao para a Ciencia e a Tecnologia (FCT-MCTES) for funding the Ph.D. Grant UI/BD/151018/2021. Andre Ramalho, Telmo G. Santos and J.P. Oliveira acknowledge Fundacao para a Ciencia e a Tecnologia (FCT-MCTES) for its financial support via the project UID/00667/2020 (UNIDEMI). J. P. Oliveira acknowledges funding by national funds from FCT-Fundacao para a Ciencia e a Tecnologia, I.P., in the scope of the projects LA/P/0037/2020, UIDP/50025/2020 and UIDB/50025/2020 of the Associate Laboratory Institute of Nanostructures, Nanomodelling and Nanofabrication - i3N. This activity has received funding from the European Institute of Innovation and Technology (EIT) - Project Smart WAAM: Microstructural Engineering and Integrated Non-Destructive Testing. This body of the European Union receives support from the European Union's Horizon 2020 research and innovation program.Prahalada Rao acknowledges funding from the Department of Energy (DOE), Office of Science, under Grant number DE-SC0021136, and the National Science Foundation (NSF) [Grant numbers CMMI-1719388, CMMI-1920245, CMMI-1739696, CMMI-1752069, PFI-TT 2044710, ECCS 2020246] for funding his research program. This work espousing the concept of online process monitoring in WAAM was funded through the foregoing DOE Grant (Program Officer: Timothy Fitzsimmons), which partially supported the doctoral graduate work of Mr. Benjamin Bevans at University of Nebraska-Lincoln Benjamin, Aniruddha, and Ziyad Smoqi were further supported by the NSF grants CMMI 1752069 (CAREER) and ECCS 2020246. Detecting flaw formation in metal AM using in-situ sensing and graph theory-based algorithms was a major component of CMMI 1752069 (program office: Kevin Chou). Developing machine learning alogirthms for advanced man-ufacturing applications was the goal of ECCS 2020246 (Program officer: Donald Wunsch). The XCT work was performed at the Nebraska Nanoscale Facility: National Nanotechnology Coordinated Infrastructure under award no. ECCS: 2025298, and with support from the Nebraska Research Initiative through the Nebraska Center for Materials and Nanoscience and the Nanoengineering Research Core Facility at the University of Nebraska-Lincoln. The acquisition of the XCT scanner at University of Nebraska was funded through CMMI 1920245 (Program officer: Wendy Crone).

Materials and design 223(111176), 1-18 (2022). doi:10.1016/j.matdes.2022.111176, The AlCoCrFeNi 2.1 eutectic high entropy alloy is of great interest due to its unique mechanical propertiescombining both high strength and plasticity. Here, gas tungsten arc welding was performed for the firsttime on an as-cast AlCoCrFeNi 2.1 alloy. The microstructural evolution of the welded joints was assessedby combining electron microscopy with electron backscatter diffraction, synchrotron X-ray diffractionanalysis and thermodynamic calculations. Microhardness mapping and tensile testing coupled with dig-ital image correlation were used to investigate the strength distribution across the joint. The base mate-rial, heat affected zone and fusion zone are composed of an FCC + B2 BCC eutectic structure, although therelative volume fractions vary across the joint owing to the weld thermal cycle. The BCC nanoprecipitatesthat existed in the base material started to dissolve into the matrix in the heat affected zone and closer tothe fusion zone boundary. Compared to the as-cast base material, the fusion zone evidenced grain refine-ment owing to the higher cooling rate experienced during solidification. This translates into an increasedhardness in this region. The joints exhibit good strength/ductility balance with failure occurring in thebase material. This work establishes the potential for using arc-based welding for joining eutectic highentropy alloys., Published by Elsevier Science, Amsterdam [u.a.]

Fundacao para a Ciencia e Tecnologia (FCT)- project UID/EMS/00667/2019 (UNIDEMI). FMBF acknowledges funding of CENIMAT by FEDER through the program COMPETE 2020 and National Funds through FCT-Portuguese Foundation for Science and Technology, under the project UID/CTM/50025/2019 and FCT/MCTES. This work was supported by the Future Material Discovery Project of the National Research Foundation of Korea (NRF) funded by the Ministry of Science and ICT of Korea (NRF-2016M3D1A1023383). NFFA-Europe Transnational Access Activity (project reference Nf-20010136 EC and ID-806). High entropy alloys have emerged as novel engineering alloys with remarkable mechanical properties in a wide range of temperatures. Among the several high entropy alloys that were already described, the equiatomic CrMnFeCoNi alloy is the most studied one. In this work, gas tungsten arc welding of as-rolled CrMnFeCoNi high entropy alloy sheets was performed. The microstructural characterization encompassed the use of electron microscopy, including electron backscattered diffraction, synchrotron X-ray diffraction analysis, microhardness testing and mechanical evaluation. A comprehensive description of the microstructural evolution, including texture and microstrain determination, of the joint is presented and discussed. Upon mechanical testing, the joints systematically failed in the fusion zone due. The large grain size and low hardness of this region justifies the failure location. The joints' mechanical behaviour is correlated with the material microstructure. publishersversion published