Cyclic Deformation of a Directionally Solidified Cobalt-Base Superalloy
An investigation has been carried out on the cyclic deformation and changes in microstructure of a directionally solidified cobalt-base superalloy. The tests are conducted at 700 °C and 850 °C in air under different total strain amplitudes. The alloy tested at 700 °C exhibits an initial hardening, a short saturation stage and an evident secondary hardening, while the alloy at 850 °C suffers continuous cyclic hardening until fracture. TEM examinations indicate that the initial hardening of the alloy at 700 °C is caused by the pile-ups of dislocations and stacking faults at the stacking fault intersections, while the stress saturation is due to the weakening of obstacles against the dislocation movement. The secondary hardening has a contribution from the formation of sessile dislocation tangles. The early stage of continuous hardening of the alloy at 850 °C is related to the pile-ups of dislocations and stacking faults at the intersections, and the later stage is controlled by the interaction between precipitates and dislocations.
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Document Type: Research Article
Affiliations: State Key Laboratory for Fatigue and Fracture of Materials, Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang, 110015, P.R. China
Publication date: 1998-12-01