Fatigue crack initiation in ULTIMET{reg{underscore}sign} alloy
The process of fatigue crack initiation in ULTIMET alloy, a Co-26Cr-9Ni (wt %) superalloy, by room-temperature cyclic deformation, was studied. The microstructure of the as-received ULTIMET alloy possessed relatively fine, uniform grains with annealing twins, and was essentially a face-centered cubic (fcc or {gamma}) phase. Fatigue testing was coupled with optical microscopy, electron microscopy, and an acoustic emission (AE) system, to study the crack initiation behavior. AE is a nondestructive evaluation technique providing good indications of the fatigue damage of the alloy. Observations of the cracks at the electropolished specimen surface and fractography indicated that the cracks initiated at the specimen surface and then propagated through one grain due to slip. The macrocracks subsequently traversed through the material due to stress concentration from the initiated microcracks.
- Research Organization:
- Univ. of Tennessee, Knoxville, TN (US)
- Sponsoring Organization:
- National Science Foundation
- OSTI ID:
- 20014215
- Country of Publication:
- United States
- Language:
- English
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