Grain boundary sliding in the presence of grain boundary precipitates during transient creep

Journal Article · Sat Apr 01 04:00:00 EST 1995 · Metallurgical Transactions, A

DOI:https://doi.org/10.1007/BF02649087· OSTI ID:42863

Wu, X J; Koul, A K ^[1]

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1. National Research Council of Canada, Ottawa, Ontario (Canada)

A constitutive rate equation for grain boundary sliding (GBS), in the presence of grain boundary precipitates, is developed. Langdon`s GBS model is modified by incorporating physically defined back stresses opposing dislocation glide and climb and by modifying the grain size dependence of creep rate. The rate equation accurately predicts the stress dependence of minimum creep rate and change in activation energy occurring as a result of changing the grain boundary precipitate distribution in complex Ni-base superalloys. The rate equation, along with the mathematical formulations for internal stresses, is used to derive a transient creep model, where the transient is regarded as the combination of primary and secondary stages of creep in constant load creep tests. The transient creep model predicts that the transient creep strain is dependent on stress and independent of test temperature. It is predicted that a true steady-state creep will only be observed after an infinitely long time. However, tertiary creep mechanisms are expected to intervene and lead to an acceleration in creep rate long before the onset of a true steady state. The model accurately predicts the strain vs time relationships for transient creep in IN738LC Ni-base superalloy, containing different grain boundary carbide distributions, over a range of temperatures.

• Sponsoring Organization: USDOE
• OSTI ID: 42863
• Journal Information: Metallurgical Transactions, A, Journal Name: Metallurgical Transactions, A Journal Issue: 4 Vol. 26; ISSN 0360-2133; ISSN MTTABN
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ACTIVATION ENERGY
CREEP
GRAIN BOUNDARIES
INCLUSIONS
MATHEMATICAL MODELS
NICKEL BASE ALLOYS
STRAINS
STRESSES