TY - GEN
T1 - Effects of dynamic strain aging on environment-assisted cracking of low alloy pressure vessel and piping steels
AU - Hänninen, Hannu
AU - Seifert, Hans-Peter
AU - Yagodzinskyy, Yuriy
AU - Ehrnsten, Ulla
AU - Tarasenko, Oleksandr
AU - Aaltonen, Pertti
N1 - Project code: H2SU00363
PY - 2003
Y1 - 2003
N2 - Strain aging occurs in alloys containing solutes that
segregate strongly to dislocations. In low-alloy steels
(LAS) static strain aging is a process where aging takes
place after pre-straining and results in return of Lüders
strain. Dynamic strain aging (DSA) is a process where
aging is sufficiently rapid to occur during straining and
it produces inhomogeneous deformation, serrated yielding.
DSA occurs at temperatures of 150-350 °C, where
stress-strain curves show serrations, being most marked
at 250 °C depending on strain rate. The mechanism of DSA
in LAS is explained based on the interstitial (N, C, H)
interactions with dislocations and their immobilization.
The important role of the accumulation of vacancies,
which are diffusion vehicles for the solute atoms, is
also considered in case of EAC. In general, activation
energy of DSA in LAS is equal to that of N/C diffusion in
ferrite. The effects of DSA of LAS are evaluated based on
peaks in UTS, hardness and strain hardening rate in the
DSA temperature range and minimum of ductility (A, Z) and
temperature of peaks decreases with decreasing strain
rate. DSA causes an increase in the ductile-to-brittle
transition temperature following plastic deformation in
the DSA temperature range, lowering of the ductile
fracture resistance (decrease of tearing modulus) at
temperatures within the DSA temperature range, as well as
ductile crack instabilities (crack jumps) in the DSA
temperature range, decreases low-cycle fatigue resistance
and the susceptibility of LAS to EAC coincides with DSA
behavior, in terms of temperature and strain rate ranges.
The present knowledge of DSA on above mentioned
properties of LAS is reviewed and DSA susceptibility of
some pressure vessel steels is demonstrated by internal
friction method and slow-strain rate tensile testing.
AB - Strain aging occurs in alloys containing solutes that
segregate strongly to dislocations. In low-alloy steels
(LAS) static strain aging is a process where aging takes
place after pre-straining and results in return of Lüders
strain. Dynamic strain aging (DSA) is a process where
aging is sufficiently rapid to occur during straining and
it produces inhomogeneous deformation, serrated yielding.
DSA occurs at temperatures of 150-350 °C, where
stress-strain curves show serrations, being most marked
at 250 °C depending on strain rate. The mechanism of DSA
in LAS is explained based on the interstitial (N, C, H)
interactions with dislocations and their immobilization.
The important role of the accumulation of vacancies,
which are diffusion vehicles for the solute atoms, is
also considered in case of EAC. In general, activation
energy of DSA in LAS is equal to that of N/C diffusion in
ferrite. The effects of DSA of LAS are evaluated based on
peaks in UTS, hardness and strain hardening rate in the
DSA temperature range and minimum of ductility (A, Z) and
temperature of peaks decreases with decreasing strain
rate. DSA causes an increase in the ductile-to-brittle
transition temperature following plastic deformation in
the DSA temperature range, lowering of the ductile
fracture resistance (decrease of tearing modulus) at
temperatures within the DSA temperature range, as well as
ductile crack instabilities (crack jumps) in the DSA
temperature range, decreases low-cycle fatigue resistance
and the susceptibility of LAS to EAC coincides with DSA
behavior, in terms of temperature and strain rate ranges.
The present knowledge of DSA on above mentioned
properties of LAS is reviewed and DSA susceptibility of
some pressure vessel steels is demonstrated by internal
friction method and slow-strain rate tensile testing.
M3 - Conference article in proceedings
SN - 951-38-6280-1
T3 - VTT Symposium
SP - 199
EP - 221
BT - Plant Life Management
PB - VTT Technical Research Centre of Finland
CY - Espoo
T2 - Plant Life Management
Y2 - 1 January 2002 through 1 January 2002
ER -