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Open AccessArticle

Investigations into the Surface Strain/Stress State in a Single-Crystal Superalloy via XRD Characterization

1
School of Materials Science and Engineering, Beihang University, Beijing 100191, China
2
ICMMO/SP2M, University Paris-Sud, bat. 410, 91405 Orsay, France
*
Authors to whom correspondence should be addressed.
Metals 2018, 8(6), 376; https://doi.org/10.3390/met8060376
Received: 21 April 2018 / Revised: 19 May 2018 / Accepted: 21 May 2018 / Published: 23 May 2018
The present study was aimed at determining the surface strain/stress state in an Ni-based single-crystal (SC) superalloy that was subjected to two different cooling rates from solid solution temperature through using the X-ray diffraction (XRD) method. The normal stresses σ 11 s and σ 22 s were determined, then the Von Mises stresses ( σ V M s ) were derived from them. Field emission gun scanning electron microscope (FEG-SEM) and transmission electron microscope (TEM) micrographs were taken to illustrate the strain/stress state change. The precipitation of the secondary γ′ phases in the γ phase and the formation of the dislocation in the interphase upon a slower cooling rate caused the γ phase lattice distortion to increase, so a larger σ V M s of the γ phase was realized in comparison to the faster cooling sample. For both of the two cooling modes, we found that the σ V M s of the γ′ phase increased due to the growth of the γ′ phase during the aging process. Also, the aging process led to pronouncedly anisotropic lattice mismatches in the {331} and {004} planes. In addition, the surface strain/stress states of a cylinder sample and a tetragonal sample were also studied using a faster cooling rate, and σ 11 s and σ 22 s were analyzed to explain the influence of the shape factor on the stress anisotropy in the [001] and [ 1 1 ¯ 0 ] orientations. The strain in the [001] orientation of the γ phase is more sensitive to the shape change. View Full-Text
Keywords: Ni-based single-crystal superalloy; XRD; surface strain/stress state; solid solution cooling speed; lattice distortion Ni-based single-crystal superalloy; XRD; surface strain/stress state; solid solution cooling speed; lattice distortion
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MDPI and ACS Style

Duan, H.; Qin, L.; Pei, Y.; Li, S.; Zhao, L.-D.; Ji, V.; Gong, S. Investigations into the Surface Strain/Stress State in a Single-Crystal Superalloy via XRD Characterization. Metals 2018, 8, 376. https://doi.org/10.3390/met8060376

AMA Style

Duan H, Qin L, Pei Y, Li S, Zhao L-D, Ji V, Gong S. Investigations into the Surface Strain/Stress State in a Single-Crystal Superalloy via XRD Characterization. Metals. 2018; 8(6):376. https://doi.org/10.3390/met8060376

Chicago/Turabian Style

Duan, Haodong; Qin, Lu; Pei, Yanling; Li, Shusuo; Zhao, Li-Dong; Ji, Vincent; Gong, Shengkai. 2018. "Investigations into the Surface Strain/Stress State in a Single-Crystal Superalloy via XRD Characterization" Metals 8, no. 6: 376. https://doi.org/10.3390/met8060376

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