Dislocations in a Ni-based superalloy during low temperature creep
1 Department of Materials Science and Metallurgy, Cambridge University, Pembroke Street, Cambridge CB2 3QZ, UK
2 Department of Materials, Imperial College, South Kensington Campus, London SW7 2AZ, UK
3 Pacific Northwest National Laboratory, 902 Battelle Boulevard, Richland, WA, USA
4 Ohio State University, 477 Watts Hall, 2041 College Rd., Columbus, OH 43210, USA
The nature and variety of the dislocations passing through the two-phase γγ′ microstructure of Ni-based superalloys is key to the properties of these materials. The chemistry, size and arrangement of the precipitates greatly affects the nature of these dislocations. We present High Angle Annular Dark Field (HAADF) TEM observations of the structure of dislocations entering, passing through the γ′ precipitates in the single-crystal superalloy CMSX-4®. The creep deformation of the sample was interrupted after 8 hours at 750 °C and 750 MPa, a critical stage just as secondary creep was being established, and shows a range of defects in both phases, not always those predicted by the Schmid factor for the deformation geometry. We show that dislocations lodged in the γγ′ interfaces have a significant effect on the structure of the interface and that they combine to produce stacking faults which cut through the γ′. The implications of these observations for secondary creep deformation are discussed.
CMSX-4® is a registered Trade Mark of the Cannon Muskegon Company.
© Owned by the authors, published by EDP Sciences, 2014
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