Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
10620891 | Acta Materialia | 2007 | 15 Pages |
Abstract
Creep deformation of the CMSX-4 nickel-base single crystal superalloy is studied in the range 750-850 °C. Emphasis is placed on elucidating the factors causing primary creep when the tensile stress is orientated within 20 °C of the technologically important ã0 0 1ã direction. It is demonstrated unambiguously that primary creep occurs only if a threshold stress of approximately 500 MPa is exceeded; thereafter the accumulated primary creep strain is proportional to the magnitude by which the threshold stress is surpassed. A very high dependence of the strain rate on the applied stress is observed. Transmission electron microscopy confirms that the stress threshold is associated with the movement of aã112¯ã dislocation ribbons through the γⲠprecipitates by so-called stacking fault shearing. The conditions necessary for the nucleation and propagation of aã112¯ã dislocation ribbons and the cessation of their movement are considered; it is demonstrated that the anisotropy of creep deformation for tensile loading within 20 °C of ã0 0 1ã can be rationalised.
Related Topics
Physical Sciences and Engineering
Materials Science
Ceramics and Composites
Authors
C.M.F. Rae, R.C. Reed,