Evolution of precipitates during creep deformation for alloy 718
This study investigated the microstructural evolution of the γ′′, γ′, and δ phases during creep for alloy 718. Creep tests on two-step aged samples were conducted under different stresses and temperatures ranging from 600 to 700 °C. Analysis of precipitates was performed on two-step aged and crept s...
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| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Published: |
Elsevier
2025-01-01
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| Series: | Journal of Materials Research and Technology |
| Subjects: | |
| Online Access: | http://www.sciencedirect.com/science/article/pii/S2238785424030412 |
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| Summary: | This study investigated the microstructural evolution of the γ′′, γ′, and δ phases during creep for alloy 718. Creep tests on two-step aged samples were conducted under different stresses and temperatures ranging from 600 to 700 °C. Analysis of precipitates was performed on two-step aged and crept samples using scanning electron microscopy and transmission electron microscopy. The creep rupture lives were decreased with increasing stresses and temperatures and showed a linear correlation between experimental data and Larson-Miller parameter curve predictions. The γ′′ phase was formed as a disc shape in the grain interior and had an orientation relationship of (001)γ′′//{001}γ and [100]γ′′//<100>γ with γ matrix. The length of the γ′′ phases increased with increasing temperatures and creep exposure time. The activation energy for γ′′ lengthening was 323 kJ/mol, similar to that for lattice diffusion of Nb in Ni. It was found that the formation mechanisms of δ phase were different from temperatures. The δ phase was formed in grain interiors and grain boundaries and had a blocky shape during a sub-δ solvus annealing process. On the other hand, the δ phase was formed as a plate shape and had an orientation relationship of (010)δ//(111¯)γ and [102]δ//[011]γ with γ matrix at creep temperatures. The growth rates of plate δ phase were faster than blocky δ phase at all creep temperatures. |
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| ISSN: | 2238-7854 |