Fatigue-induced Reversible/Irreversible Structural-transformation Study of a Ni-based Superalloy Using Combined In-situ Neutron-Diffraction and Thermal Approaches
- ORNL
- National Tsing Hua University, Taiwan
- University of Tennessee, Knoxville (UTK)
Cyclic loading and the subsequent fatigue damage have been investigated with the in-situ neutron-diffraction and thermal characterization for a single-phase, polycrystal nickel-based alloy. The lattice-strain evolution is compared with the bulk parameters, such as the applied stress and the thermal response as a function of the fatigue cycles. The in-situ neutron-diffraction and thermal-evolution results identify the development of the five fatigue-damage stages. Fatigue damage is observed with bulk hardening, softening, and eventual saturation evident in both the diffraction patterns and the thermal-evolution features. An increase in the dislocation density and the formation of the patterned-dislocation structure are responsible for hardening within the early cycles. With further cyclic loading, the rearrangements of the dislocations result in the cyclic softening. The transition to saturation cycles is characterized by the anisotropy of the lattice strain evolution. The nonmonotonic thermal response and the irreversible anisotropy of the lattice-strain evolution are observed in the final saturation fatigue cycles. The fatigue-damage microstructure and dislocation-substructure evolution are studied with diffraction-profile analyses and complemented by the transmission-electron microscopy. The fluctuations of the differential dislocation density and size of the patterned substructure along with the in-situ thermal measurements reveal a second-order-kind structural transition and indicate the development of the irreversible fatigue-induced microstructure.
- Research Organization:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC)
- DOE Contract Number:
- DE-AC05-00OR22725
- OSTI ID:
- 984378
- Journal Information:
- International Journal of Plasticity, Vol. 26, Issue 8; ISSN 0749-6419
- Country of Publication:
- United States
- Language:
- English
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