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Prediction and characterization of variant electron diffraction patterns for γ″ and δ precipitates in an INCONEL 718 alloy

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Abstract

A universal theoretical method has been developed in this article to predict and characterize electron diffraction patterns (EDPs) which contain various variants of precipitate(s) with a matrix. The plane and direction transition matrices for three γ″-phase variants and 12 δ-phase variants precipitated from a γ matrix in the INCONEL 718 alloy were deduced, from which the EDPs for seven low-index zones of γ matrix containing γ″ precipitates were predicted by plotting and were found to be consistent with transmission electron microscopy (TEM) observations, showing that some of the results reported by Quist et al. should be corrected. Meanwhile, three variants of δ phase, precipitated from any one of four {111} matrices in 12 possible orientational variants, were also predicted and confirmed by EDPs. Different from Paulonis’ conclusion, our theoretical calculations indicated that the {1/2 1 0}-type superlattice reflections in the 〈100〉 zone of the γ matrix permitted detection of both γ″- and δ-phase precipitates, but not of γ″-phase precipitates. Therefore, the precipitates shown in dark-field images using these superlattice reflections cannot be unambiguously determined to be γ″ phase. A unique approach for identification of γ″ precipitates in the alloy has been proposed.

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Author notes

  1. Ming Gao (Principal Research Scientist, Engineering Advisor)

    Present address: the Department of Mechanical Engineering and Mechanics, Lehigh University, 18015-3085, Bethlehem, PA

Authors and Affiliations

  1. the School of Materials Science and Engineering, Shanghai Jiao Tong University, 200030, Shanghai, People’s Republic of China

    Yonghua Rong (Associate Professor), Shipu Chen (Professor) & Geng-Xiang Hu (Professor)

  2. Mobil Technology Company, 75244, Dallas, TX

    Ming Gao (Principal Research Scientist, Engineering Advisor)

  3. the Department of Mechanical Engineering and Mechanics, Lehigh University, 18015-3085, Bethlehem, PA

    Robert P. Wei (Professor)

Authors
  1. Yonghua Rong
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  2. Shipu Chen
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  3. Geng-Xiang Hu
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  4. Ming Gao
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  5. Robert P. Wei
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Rong, Y., Chen, S., Hu, GX. et al. Prediction and characterization of variant electron diffraction patterns for γ″ and δ precipitates in an INCONEL 718 alloy. Metall Mater Trans A 30, 2297–2303 (1999). https://doi.org/10.1007/s11661-999-0239-x

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  • DOI: https://doi.org/10.1007/s11661-999-0239-x

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