Effect of creep strain on microstructural stability and creep resistance of a TiAl/Ti{sub 3}Al lamellar alloy
- Univ. of Virginia, Charlottesville, VA (United States). Dept. of Materials Science and Engineering
- Reynolds Metals Co., Richmond, VA (United States). Corporate Research and Development Lab.
Creep of a TiAl/Ti{sub 3}Al alloy with a lamellar microstructure causes progressive spheroidization of the lamellar microstructure. Microstructural observations reveal that deformation-induced spheroidization (DIS) occurs by deformation and fragmentation of lamellae in localized shear zones at interpacket boundaries and within lamellar packets. Deformation-induced spheroidization substantially increases the interphase interfacial area per unit volume, demonstrating that DIS is not a coarsening process driven by reduction of interfacial energy per unit volume. Creep experiments reveal that DIS increases the minimum creep rate ({dot {var_epsilon}}{sub min}) during creep at constant stress and temperature; the activation energy (Q{sub c}) and stress exponent (n) for creep are both reduced as a result of DIS. Values of n and Q{sub c} for the lamellar microstructure are typical of a dislocation creep mechanism, while estimated values of n and Q{sub c} for the completely spheroidized microstructure are characteristic of a diffusional creep mechanism. The increase in {dot {var_epsilon}}{sub min} associated with DIS is thus attributed primarily to a change of creep mechanism resulting from microstructural refinement.
- OSTI ID:
- 203524
- Journal Information:
- Metallurgical Transactions, A, Journal Name: Metallurgical Transactions, A Journal Issue: 1 Vol. 27; ISSN 0360-2133; ISSN MTTABN
- Country of Publication:
- United States
- Language:
- English
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