TEM Study of High-Temperature Precipitation of Delta Phase in Inconel 718 Alloy
Inconel 718 is widely used because of its ability to retain strength at up to 650∘C for long periods of time through coherent metastable 𝛾 Ni3Nb precipitation associated with a smaller volume fraction of 𝛾 Ni3Al precipitates. At very long ageing times at service temperature, 𝛾 decomposes to...
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| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Wiley
2011-01-01
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| Series: | Advances in Materials Science and Engineering |
| Online Access: | http://dx.doi.org/10.1155/2011/940634 |
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| Summary: | Inconel 718 is widely used because of its ability to retain strength at up to 650∘C for long periods of time through coherent metastable 𝛾
Ni3Nb precipitation associated with a smaller volume fraction of 𝛾
Ni3Al precipitates. At very long ageing times at service temperature, 𝛾
decomposes to the stable Ni3Nb 𝛿 phase. This latter phase is also present above the 𝛾
solvus and is used for grain control during forging of alloy 718. While most works available on 𝛿 precipitation have been performed at temperatures below the 𝛾
solvus, it appeared of interest to also investigate the case where 𝛿 phase precipitates directly from the fcc matrix free of 𝛾
precipitates. This was studied by X-ray diffraction and transmission electron microscopy (TEM). TEM observations confirmed the presence of rotation-ordered domains in 𝛿 plates, and some unexpected contrast could be explained by double diffraction due to overlapping phases. |
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| ISSN: | 1687-8434 1687-8442 |