Microstructural and micromechanical characterization of IN718 theta shaped specimens built with electron beam melting

• Published in: Acta materialia 2016-04, Vol.108 (C), p.161-175
• Main Authors: Cakmak, Ercan, Kirka, Michael M., Watkins, Thomas R., Cooper, Ryan C., An, Ke, Choo, Hahn, Wu, Wei, Dehoff, Ryan R., Babu, Sudarsanam S.
• Format: Article
• Language: English
• Subjects: Additive manufacturing; Construction; Electron beam melting; Lattice strains; MATERIALS SCIENCE; Microstructure; Neutron diffraction; Nickel base alloys; Nickel-based superalloys; Strain; Strategy; Superalloys; Surface layer; Texture
• ISSN: 1359-6454; 1873-2453
• DOI: 10.1016/j.actamat.2016.02.005

Theta-shaped specimens were additively manufactured out of Inconel 718 powders using an electron beam melting technique, as a model complex load bearing structure. Two different build strategies were employed; producing two sets of specimens. Microstructural and micro-mechanical characterizations were performed using electron back-scatter, synchrotron x-ray and in-situ neutron diffraction techniques. In particular, the cross-members of the specimens were the focus of the synchrotron x-ray and in-situ neutron diffraction measurements. The build strategies employed resulted in the formation of distinct microstructures and crystallographic textures, signifying the importance of build-parameter manipulation for microstructural optimization. Large strain anisotropy of the different lattice planes was observed during in-situ loading. Texture was concluded to have a distinct effect upon both the axial and transverse strain responses of the cross-members. In particular, the (200), (220) and (420) transverse lattice strains all showed unexpected overlapping trends in both builds. This was related to the strong {200} textures along the build/loading direction, providing agreement between the experimental and calculated results. [Display omitted]