Metallurgical and Materials Transactions A

, Volume 32, Issue 12, pp 2975–2984

Evaluation of a threshold-based model of the elevated-temperature fatigue of impact-damaged γ-TiAl

  • Trevor S. Harding
  • J. Wayne Jones
Article

DOI: 10.1007/s11661-001-0172-0

Cite this article as:
Harding, T.S. & Jones, J.W. Metall and Mat Trans A (2001) 32: 2975. doi:10.1007/s11661-001-0172-0

Abstract

Step-loading fatigue tests have been conducted on two γ-TiAl alloys with differing microstructures following quasi-static indentations intended to simulate assembly-related impact damage to low-pressure turbine blades. Fatigue tests were conducted at 600 °C using computer-controlled servohydraulic loading at a frequency of 20 Hz. Reasonably good agreement was achieved between the fatigue data and calculated fatigue strength based on the fatigue threshold and measured impact severity. In certain cases, the fatigue threshold model fails to completely describe the data. These discrepancies may be related to residual stresses, variations in crack-shape morphology, and small-crack effects. Residual stresses could not be directly measured, given the small size of the damage zones. However, a comparison of fatigue threshold approximations based on a through-thickness crack geometry and a corner-crack geometry suggests that these two models may represent the upper and lower bounds of the actual fatigue behavior. In addition, the behavior of small cracks was examined by modeling the stress-lifetime response of lightly damaged specimens of the duplex alloy. This effort indicates the need for small-crack fatigue threshold values when designing fatigue-critical γ-TiAl components.

Copyright information

© ASM International & TMS-The Minerals, Metals and Materials Society 2001

Authors and Affiliations

  • Trevor S. Harding
    • 1
  • J. Wayne Jones
    • 2
  1. 1.the Manufacturing Engineering DepartmentKettering UniversityFlint
  2. 2.Department of Materials Science and EngineeringUniversity of MichiganAnn Arbor

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