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Abstract:
Non-weldable nickel-based superalloys fabricated via electron beam powder bed fusion exhibit pronounced preferential grain growth orientation, resulting in significant anisotropic mechanical behavior. This study demonstrates a methodology for controlling anisotropic microstructures in Inconel 939 through process parameter optimization, specifically by modulating EB-PBF energy density to tailor mechanical properties. Electron backscatter diffraction analysis revealed distinct microstructural characteristics: the lowest energy density sample (E1) displayed elongated columnar grains with strong <001 > texture (aspect ratio similar to 15.86), while the highest energy density sample (E3) contained uniformly oriented near-equiaxed grains (aspect ratio similar to 3.94). Transmission electron microscopy characterization of tensile specimens indicated that along the parallel building direction, E1 exhibited extensive dislocation pile-ups and bypass mechanisms. With increasing energy density, E2 demonstrated enhanced dislocation accumulation with partial shearing at carbide peripheries, whereas E3 showed complete dislocation penetration through entire carbide strengthening phases. Tensile testing quantified the anisotropic ultimate tensile strength differentials: 348.7 MPa for E1, 130.4 MPa for E2, and 47.6 MPa for E3. Regarding anisotropic yield strength differences, E2 exhibited significantly reduced yield strength due to carbide coarsening, resulting in larger anisotropy differentials compared to both E1 and E3 samples. Nevertheless, E1 and E3 still followed the trend of progressively reduced anisotropy. The results establish that strategic energy density control enables microstructural isotropization through combined grain morphology modification and optimization of dislocation-mediated strengthening mechanisms.
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JOURNAL OF ALLOYS AND COMPOUNDS
ISSN: 0925-8388
Year: 2025
Volume: 1041
5 . 8 0 0
JCR@2023
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ESI Highly Cited Papers on the List: 0 Unfold All
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30 Days PV: 0
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