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In situ observation of morphological changes of γ′ precipitates in a pre‐deformed single‐crystal Ni‐base superalloy
Author(s) -
Strunz Pavel,
Schumacher Gerhard,
Klingelhöffer Hellmuth,
Wiedenmann Albrecht,
Šaroun Jan,
Keiderling Uwe
Publication year - 2011
Publication title -
journal of applied crystallography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.429
H-Index - 162
ISSN - 1600-5767
DOI - 10.1107/s0021889811028147
Subject(s) - materials science , superalloy , precipitation , anisotropy , in situ , morphology (biology) , composite material , crystallography , microstructure , geology , chemistry , optics , paleontology , physics , meteorology , organic chemistry
Exposure of a superalloy to an external load results in anisotropic coarsening of the γ′ precipitates, so‐called rafting. It was reported in the past that γ′ rafting can also occur as a result of purely thermal treatment, without the simultaneous presence of an external load, if the specimen has been pre‐deformed at relatively low temperature. The evolution of γ′ morphology in pre‐deformed specimens of SCA425 Ni‐base superalloy was examined in the present study. Unlike in the previous experiments, the compressive stress was used for pre‐straining. In situ small‐angle neutron scattering (SANS) was employed, which enabled the determination of the morphology directly at high temperature. Both for strong and for weak pre‐straining, rounding of the originally cuboidal precipitates towards an ellipsoidal shape on heating was observed. Weak pre‐straining (0.1, 0.5%) does not cause rafting on subsequent heating. On the other hand, the detailed evaluation of SANS data provides some indication of rafting during the subsequent heating after severe compressive pre‐straining (2%). The experiment indicates the role of dislocation rearrangement at the matrix/precipitate interface during pre‐straining.