Fatigue crack growth characteristics and effect of microstructure in TiAl intermetallics
Gnanamoorthy Rajappa; Mutoh Yoshiharu; Masahashi Naoya; Mizuhara Yoji
Abstract:Fatigue crack growth tests on four kinds of g-base TiAl alloys with different microstructures were carried out. The basic mechanism of fatigue crack growth and the effect of microstructure on fatigue crack growth properties were discussed in detail. It was found that microcrack nucleation in the near crack tip region, growth and coalescence to a main crack are the dominant mechanism of fatigue crack growth. The fatigue crack growth resistance of lamellar microstructure material was higher than that of duplex micro-structure material, which in turn was higher than that of equiaxed microstructure material. In the lamellar microstructure materials, crack growth resistance was low when the orientation of lamellar lath coincided with the crack growth direction. These differences in crack growth resistance might be induced by the stress shielding effect due to bridging on the crack wake. Key Words:fatigue crack growth, mechanism, stress shielding, titanium aluminide, microstructure