Mechanical Characterization of an Additively Manufactured Inconel 718 Theta-Shaped Specimen

Ercan Cakmak; Thomas R. Watkins; Jeffrey R. Bunn; Ryan C. Cooper; Paris A. Cornwell; Yanli Wang; Lindsay M. Sochalski-Kolbus; Ryan R. Dehoff; Sudarsanam S. Babu

doi:10.1007/s11661-015-3186-8

Mechanical Characterization of an Additively Manufactured Inconel 718 Theta-Shaped Specimen

Ercan Cakmak, Thomas R. Watkins, Jeffrey R. Bunn, Ryan C. Cooper, Paris A. Cornwell, Yanli Wang, Lindsay M. Sochalski-Kolbus, Ryan R. Dehoff, Sudarsanam S. Babu

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Abstract

Two sets of “theta”-shaped specimens were additively manufactured with Inconel 718 powders using an electron beam melting technique with two distinct scan strategies. Light optical microscopy, mechanical testing coupled with a digital image correlation (DIC) technique, finite element modeling, and neutron diffraction with in situ loading characterizations were conducted. The cross-members of the specimens were the focus. Light optical micrographs revealed that different microstructures were formed with different scan strategies. Ex situ mechanical testing revealed each build to be stable under load until ductility was observed on the cross-members before failure. The elastic moduli were determined by forming a correlation between the elastic tensile stresses determined from FEM, and the elastic strains obtained from DIC. The lattice strains were mapped with neutron diffraction during in situ elastic loading; and a good correlation between the average axial lattice strains on the cross-member and those determined from the DIC analysis was found. The spatially resolved stresses in the elastic deformation regime are derived from the lattice strains and increased with applied load, showing a consistent distribution along the cross-member.

Original language	English
Pages (from-to)	971-980
Number of pages	10
Journal	Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science
Volume	47
Issue number	2
DOIs	https://doi.org/10.1007/s11661-015-3186-8
State	Published - Feb 1 2016

Funding

This research was sponsored by the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory, managed by UT-Battelle, LLC, for the U. S. Department of Energy. Research at MDF was sponsored by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Advanced Manufacturing Office, under contract DE-AC05-00OR22725 with UT-Battelle, LLC. Research at ORNL’s High Flux Isotope Reactor was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy. EC and TRW would like to thank Dr. E. Andrew Payzant for the neutron beam time, Mr. Christopher O. Stevens for his help with the ex situ mechanical testing, and Mr. Tom Geer for optical microscopy measurements. Further, the authors gratefully acknowledge Dr. Donald L. Erdman III, Mr. Stephen Kulan, and Dr. Ke An for their timely help with the load frame during our measurements at HFIR. EC would also like to thank Dr. Michael M. Kirka for his valuable input and Mr. Cemal Kizildag for his assistance with image processing.

Funders	Funder number
Scientific User Facilities Division
U.S. Department of Energy
Advanced Manufacturing Office	DE-AC05-00OR22725
Office of Energy Efficiency and Renewable Energy
Basic Energy Sciences
Oak Ridge National Laboratory

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Cakmak, E., Watkins, T. R., Bunn, J. R., Cooper, R. C., Cornwell, P. A., Wang, Y., Sochalski-Kolbus, L. M., Dehoff, R. R., & Babu, S. S. (2016). Mechanical Characterization of an Additively Manufactured Inconel 718 Theta-Shaped Specimen. Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science, 47(2), 971-980. https://doi.org/10.1007/s11661-015-3186-8

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abstract = "Two sets of “theta”-shaped specimens were additively manufactured with Inconel 718 powders using an electron beam melting technique with two distinct scan strategies. Light optical microscopy, mechanical testing coupled with a digital image correlation (DIC) technique, finite element modeling, and neutron diffraction with in situ loading characterizations were conducted. The cross-members of the specimens were the focus. Light optical micrographs revealed that different microstructures were formed with different scan strategies. Ex situ mechanical testing revealed each build to be stable under load until ductility was observed on the cross-members before failure. The elastic moduli were determined by forming a correlation between the elastic tensile stresses determined from FEM, and the elastic strains obtained from DIC. The lattice strains were mapped with neutron diffraction during in situ elastic loading; and a good correlation between the average axial lattice strains on the cross-member and those determined from the DIC analysis was found. The spatially resolved stresses in the elastic deformation regime are derived from the lattice strains and increased with applied load, showing a consistent distribution along the cross-member.",

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Cakmak, E , Watkins, TR , Bunn, JR, Cooper, RC, Cornwell, PA , Wang, Y, Sochalski-Kolbus, LM, Dehoff, RR & Babu, SS 2016, 'Mechanical Characterization of an Additively Manufactured Inconel 718 Theta-Shaped Specimen', Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science, vol. 47, no. 2, pp. 971-980. https://doi.org/10.1007/s11661-015-3186-8

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AU - Watkins, Thomas R.

AU - Bunn, Jeffrey R.

AU - Cooper, Ryan C.

AU - Cornwell, Paris A.

AU - Wang, Yanli

AU - Sochalski-Kolbus, Lindsay M.

AU - Dehoff, Ryan R.

AU - Babu, Sudarsanam S.

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N2 - Two sets of “theta”-shaped specimens were additively manufactured with Inconel 718 powders using an electron beam melting technique with two distinct scan strategies. Light optical microscopy, mechanical testing coupled with a digital image correlation (DIC) technique, finite element modeling, and neutron diffraction with in situ loading characterizations were conducted. The cross-members of the specimens were the focus. Light optical micrographs revealed that different microstructures were formed with different scan strategies. Ex situ mechanical testing revealed each build to be stable under load until ductility was observed on the cross-members before failure. The elastic moduli were determined by forming a correlation between the elastic tensile stresses determined from FEM, and the elastic strains obtained from DIC. The lattice strains were mapped with neutron diffraction during in situ elastic loading; and a good correlation between the average axial lattice strains on the cross-member and those determined from the DIC analysis was found. The spatially resolved stresses in the elastic deformation regime are derived from the lattice strains and increased with applied load, showing a consistent distribution along the cross-member.

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Mechanical Characterization of an Additively Manufactured Inconel 718 Theta-Shaped Specimen

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