Creep behavior of a β′(NiAl) precipitation strengthened ferritic Fe-Cr-Ni-Al alloy

S. M. Zhu, S. C. Tjong, J. K.L. Lai

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Abstract

Creep in precipitation-strengthened alloys usually exhibits a pronounced transition in the stress vs creep rate relationship due to dislocations bypassing of particles by climb at low stresses. In the present study, a single-slope behavior is observed in creep of β′(NiAl) strengthened ferritic Fe-19Cr-4Ni-2Al alloy in the temperature range 873-923 K. The alloy exhibits anomalously high values of apparent stress exponent (16-18) and activation energy (980 kJ/mol). Transmission electron microscopy examination of the deformation microstructure reveals the occurrence of attractive dislocation/particle interaction, a feature which is usually observed in dispersion-strengthened alloys. Such an attractive dislocation/particle interaction makes the local climb of dislocations over particles a realistic configuration at low stresses. The creep data are analyzed by the back-stress approach and by the recent dislocation-climb theories based on attractive interaction between dislocations and particles. By considering a back stress, all data can be rationalized by a power-law with a stress exponent of 4 and a creep activation energy close to the self-diffusion energy of the matrix lattice. Local climb together with the attractive but not strong interactions between the dislocations and particles is suggested to be the operative deformation mechanism at low stresses and to account for the single-slope behavior in the stress/creep rate relationship of this alloy.

Original languageEnglish
Pages (from-to)2969-2976
Number of pages8
JournalActa Materialia
Volume46
Issue number9
DOIs
Publication statusPublished - 22 May 1998
Externally publishedYes

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