Metallurgical and Materials Transactions A

, Volume 31, Issue 7, pp 1741–1752

The effect of impact damage on the room-temperature fatigue behavior of γ-TiAl

  • Trevor S. Harding
  • J. Wayne Jones
Article

Abstract

The relationship between impact damage and the fatigue behavior of γ-TiAl has been examined. Axial fatigue specimens fabricated from cast Ti-47.9Al-2.0Cr-1.9Nb (to be referred to as 48-2-2) and Ti-47.3Al-2.2Nb-0.5Mn-0.4W-0.4Mo-0.23Si (to be referred to as WMS) alloys were damaged by impact under controlled conditions with a 60 deg wedge-shaped indenter to simulate assembly-related damage in low-pressure turbine blades. The level of damage produced was quantified and found to correlate well with the peak load of the impact event. The WMS alloy exhibited a greater resistance to impact damage due to its higher yield strength and lamellar microstructure. A measure of the ambient-temperature fatigue failure stress in the alloys was obtained by standard fatigue testing employing a step-loading approach. The failure stress of the WMS alloy was greater than that of the 48-2-2 alloy in the undamaged state. The relationship between impact damage and failure stress was examined using a threshold-based approach. These studies indicate that, for damage levels below a transitional flaw size, the failure stress is near that for undamaged specimens. At damage levels greater than the transitional flaw size, the failure stress can be adequately approximated using the threshold stress-intensity range (ΔKTH) from long-crack growth testing. Fractographic studies were performed to investigate impact damage and crack-advance mechanisms, which match those observed in other alloys tested at room temperature.

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Copyright information

© ASM International & TMS-The Minerals, Metals and Materials Society 2000

Authors and Affiliations

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

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