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Microstructural evolution of monocrystalline Co–Al–W-based superalloys by high-temperature creep deformation

Published online by Cambridge University Press:  28 December 2012

Takahiro Sumitani
Affiliation:
Department of Mechanics, Kobe University, Rokkodai-cho, Nada-ku, Kobe 657-8501, Japan
Katsushi Tanaka
Affiliation:
Department of Mechanics, Kobe University, Rokkodai-cho, Nada-ku, Kobe 657-8501, Japan
Haruyuki Inui
Affiliation:
Department of Materials Science and Engineering, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
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Abstract

Creep tests of monocrystalline Co–Al–W-based alloys with a tensile stress of 137 MPa at 1000 °C were carried out. The microstructures of the crept specimens were investigated by scanning electron microscope (SEM) and transmission electron microscope (TEM). The γ′ phase in the specimens was not only elongated along the stress direction as expected by the sign of the lattice misfit but also elongated in one of the <100> directions perpendicular to the stress direction. As a result, the shape of the γ′ phase is not a rod but a plate. In the TEM images, it was observed that many SISFs are induced in the γ′ phase by creep. A similar microstructure is also observed in Ni-based superalloys, but the microstructure was formed under relatively lower temperatures and higher applied stresses. The observation of numerous stacking faults in the γ′ phase is a clear indication that the γ′ phase precipitated in the present alloy is weaker than that in many modern Ni-based superalloys.

Type
Articles
Copyright
Copyright © Materials Research Society 2012 

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References

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