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Low cycle fatigue mechanism of René 80 at high temperature-high strain

Rahmani, Kh ; Sharif University of Technology | 2008

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  1. Type of Document: Article
  2. DOI: 10.1016/j.msea.2008.04.067
  3. Publisher: 2008
  4. Abstract:
  5. The low cycle fatigue René 80, a Ni-base superalloy, was studied at temperature of 871 °C, R = (εmin/εmax) = 0 and strain rate of about 2 × 10-3 s-1. The dislocation structure and failure surface observations were evaluated through TEM and SEM. TEM studies showed that at Δεt = 0.8% during the first cycle the dislocations formed a hexagonal network in the γ-phase matrix. When the number of cycles increased, the density of dislocations increased as well. At N = Nf and Δεt = 0.8% the cutting of γ′ precipitates took place. SEM studies at Δεt = 0.8% and N = Nf showed that fatigue crack initiation generally occurred at the surface, where it is depleted of the γ′ phase as a result of oxidation by the high-temperature exposure. In addition to depleted zones, the grain boundary oxidation and oxide spikes were also considered as further crack initiation sites
  6. Keywords:
  7. Nickel ; Cutting mechanism ; Dislocation ; High strains ; High temperature ; LCF ; Low cycle fatigues ; Ni-base super alloys ; Relaxation ; TEM ; Superalloys
  8. Source: Materials Science and Engineering A ; Volume 494, Issue 1-2 , 2008 , Pages 385-390 ; 09215093 (ISSN)
  9. URL: https://www.sciencedirect.com/science/article/abs/pii/S0921509308004589