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Metallurgical Transactions A

, Volume 23, Issue 6, pp 1663–1677 | Cite as

Influence of microstructure on crack-tip micromechanics and fracture behaviors of a two-phase TiAl alloy

  • K. S. Chan
  • Y.-W. Kim
Mechanical Behavior

Abstract

The tensile deformation, crack-tip micromechanics, and fracture behaviors of a two-phase (γ + α2) gamma titanium aluminide alloy, Ti-47Al-2.6Nb-2(Cr+V), heat-treated for the microstructure of either fine duplex (gamma + lamellar) or predominantly lamellar microstructure were studied in the 25 °C to 800 °C range.In situ tensile and fracture toughness tests were performed in vacuum using a high-temperature loading stage in a scanning electron microscope (SEM), while conventional tensile tests were performed in air. The results revealed strong influences of microstructure on the crack-tip deformation, quasi-static crack growth, and the fracture initiation behaviors in the alloy. Intergranular fracture and cleavage were the dominant fracture mechanisms in the duplex microstructure material, whose fracture remained brittle at temperatures up to 600 °C. In contrast, the nearly fully lamellar microstructure resulted in a relatively high crack growth resistance in the 25 °C to 800 °C range, with interface delamination, translamellar fracture, and decohesion of colony boundaries being the main fracture processes. The higher fracture resistance exhibited by the lamellar microstructure can be attributed, at least partly, to toughening by shear ligaments formed as the result of mismatched crack planes in the process zone.

Keywords

Fracture Toughness Tensile Ductility Lamellar Microstructure Duplex Microstructure Interface Delamination 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© The Minerals, Metals & Materials Society and ASM International 1992

Authors and Affiliations

  • K. S. Chan
    • 1
  • Y.-W. Kim
    • 2
  1. 1.Department of Materials and MechanicsSouthwest Research InstituteSan Antonio
  2. 2.Metcut-Materials Research GroupWright-Patterson AFB

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