Effect of a single overload on the cyclic R-curve behaviour of a γ-TiAl TNM alloy

https://doi.org/10.1016/j.ijfatigue.2022.107083Get rights and content
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Highlights

  • Fatigue threshold behaviour of semi-brittle γ-TiAl was investigated.

  • Tensile overloads led to very steep R-curves in subsequent fatigue tests.

  • The long-crack threshold was not affected by the previous overload.

Abstract

The effect of single overloads on the threshold of stress intensity range of a semi-brittle material, a γ-titanium aluminide, was analysed. This material class exhibits a pronounced R-curve behaviour, which is mainly caused by the formation of shear ligaments, crack deflection and branching. Samples with short cracks on deep sharp notches were subjected to overloads of 80 % of the fracture toughness. Contrary to ductile materials, the experiments revealed no significant increase in the long-crack threshold, however a pronounced increase in the slope of the R-curve for the threshold of stress intensity range.

Keywords

Titanium aluminide
R-curve
Fatigue threshold
Overload

Abbreviations

BSE
Backscatter Electron
DC
Direct Current
DCPD
Direct Current Potential Drop
EDM
Electro Discharge Machining
HIP
Hot Isostatic Pressing
R-curve
Resistance Curve
SE
Secondary Electron
SEM
Scanning Electron Microscope
SENT
Single Edge Notched Tension

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