The effect of ageing on the microstructural stability and microhardness of samples prepared from a cast turbine blade with nominal chemical composition Ti-46Al-2W-0.5Si (at.%) was studied. Ageing experiments were performed at three temperatures of 973, 1023, and 1073 K for various times ranging from 10 to 7300 h in air. Microstructure of the ageing samples consisted of lamellar, feathery and gamma-rich regions. Microstructural analysis revealed that the lamellar regions are composed of alpha2(Ti3Al) and gamma-TiAl lamellae, coarse B2 particles and fine needle-like B2 precipitates. The feathery regions contain gamma-matrix with alpha2, B2 and Ti5Si3 particles. Coarse Ti5Si3 particles are identified within the gamma-rich regions. During ageing the alpha2-phase in the lamellar and feathery regions transforms to the gamma-phase and fine needle-like B2 precipitates. The microstructural instabilities lead to a softening of the alloy, which is characterized by a faster microhardness decrease of the lamellar regions comparing with that of the feathery ones. The measured time exponents and activation energies for softening are discussed from the point of diffusion-controlled transformations and coarsening of the coexisting phases. A possible effect of such microstructural changes on the kinetics of softening is analysed.


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    Title :

    Stability of the microstructure and microhardness of a cast TiAl-based intermetallic alloy for turbine blades


    Additional title:

    Stabilität des Mikrogefüges und der Mikrohärte von gegossenen intermetallischen TiAl-Basis-Legierungen für Turbinenblätter


    Contributors:
    Lapin, J. (author) / Pelachova, T. (author)

    Published in:

    Metallic Materials ; 42 , 3 ; 97-104


    Publication date :

    2004


    Size :

    8 Seiten, 10 Bilder, 28 Quellen



    Type of media :

    Article (Journal)


    Type of material :

    Print


    Language :

    English




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