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Abstract Wire-arc directed energy deposition (DED) processed Inconel (IN) 718 is known to have coarse columnar grains, strong texture, and significant chemical and microstructural inhomogeneity in the as-fabricated condition. Homogenization treatment is commonly used prior to aging to eliminate the inhomogeneity and detrimental precipitation for better mechanical properties. In this study, however, direct aging (DA) at 700 °C without homogenization has resulted in room-temperature yield strength, ultimate tensile strength (UTS), and elongation that are comparable to wrought condition and among the highest reported properties for wire-arc DED IN718. The DA samples at between 650 and 750 °C aging also demonstrates remarkable ductility when deformed at elevated temperatures. In addition, when aged below 750 °C the DA IN718 possesses significantly higher UTS compared to those with homogenization treatment. These superior mechanical properties are highly likely due to the non-uniform and hierarchical precipitation consisting of disk-shaped γ″ in diameter from a few to tens of nm in the dendritic core area and micron-sized Laves phase and carbides in the inter-dendritic region.
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Radial Deposition for Mechanical Bonding of Dissimilar Metals in Wire Arc Additive Manufacturing
High energy input creates enormous challenges for direct fusion bonding between dissimilar metals in wire‐arc directed energy deposition (DED). Vast differences in material properties, such as those between aluminum and stainless steel, cause significant compatibility issues. Their combination for higher performance is a compelling goal, but attempts are usually limited to nonadditive mechanical fastening. Wire‐based additive for direct fusion has never been attempted, and only powder‐based additive metal fusion manufacturing (AM) has shown any promise. Concentric radial deposition patterns are used in a wire‐arc DED system to produce a layer‐by‐layer in situ bimetallic coupling between AA5356 and SS308L to address this. The additively generated mechanical bond is held together by residual pressure, created by different thermal expansion coefficients between the concentric material bands during cooling. This produces a purely additive yet viable mechanical joint with minimal metallurgical bonding. Destructive testing defines the integrity of the additively coupled unit, with the radial overlap sustaining 732.96 Nm in torsion, 34.17 kN in tension, and a maximum of 475 MPa in compression. Fracture modes confirm the importance of concentric residual loads in creating the mechanically viable joint. Interfacial characterization shows a 300× reduction in crack width for concentrically constrained interfaces with narrowed diffusion zones.
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- Award ID(s):
- 1934230
- PAR ID:
- 10644713
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Engineering Materials
- Volume:
- 27
- Issue:
- 7
- ISSN:
- 1438-1656
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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