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Title: Microstructure Development in Electron Beam-Melted Inconel 718 and Associated Tensile Properties

During the electron beam melting (EBM) process, builds occur at temperatures in excess of 800°C for nickel-base superalloys such as Inconel 718. When coupled with the temporal differences between the start and end of a build, a top-to-bottom microstructure gradient forms. Characterized in this study is the microstructure gradient and associated tensile property gradient that are common to all EBM Inconel 718 builds. From the characteristic microstructure elements observed in EBM Inconel 718 material, the microstructure gradient can be classified into three distinct regions. Region 1 (top of a build) and is comprised of a cored dendritic structure that includes carbides and Laves phase within the interdendritic regions. Region 2 is an intermediate transition zone characterized by a diffuse dendritic structure, dissolution of the Laves phase, and precipitation of δ needle networks within the interdendritic regions. The bulk structure (Region 3) is comprised of a columnar grain structure lacking dendritic characteristics with δ networks having precipitated within the grain interiors. Mechanically at both 20°C and 650° C, the yield strength, ultimate tensile strength, and elongation at failure exhibit the general trend of increasing with increasing build height.
 [1] ;  [1] ;  [2] ;  [3] ;  [1] ;  [4]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  2. Univ. of Tennessee, Knoxville, TN (United States)
  3. Arcam AB, Molndal (Sweden)
  4. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Univ. of Tennessee, Knoxville, TN (United States)
Publication Date:
Grant/Contract Number:
Accepted Manuscript
Journal Name:
JOM. Journal of the Minerals, Metals & Materials Society
Additional Journal Information:
Journal Volume: 68; Journal Issue: 3; Journal ID: ISSN 1047-4838
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Manufacturing Demonstration Facility (MDF)
Sponsoring Org:
USDOE Office of Energy Efficiency and Renewable Energy (EERE)
Country of Publication:
United States
36 MATERIALS SCIENCE; Electron Beam Melting; Inconel 718; Superalloy; Additive Manufacturing; Tensile Properties
OSTI Identifier: