Grain Boundary Phosphorous Segregation and Its Influence on the Ductile Brittle Transition Temperature in Reactor Pressure Vessel Steels

2004 ◽  
Vol 1 (9) ◽  
pp. 11369 ◽  
Author(s):  
A Kimura ◽  
M Shibata ◽  
R Kasada ◽  
H Nakata ◽  
K Fujii ◽  
...  
Keyword(s):  
Transition Temperature ◽  
Grain Boundary ◽  
Pressure Vessel ◽  
Reactor Pressure Vessel ◽  
Brittle Transition ◽  
Ductile Brittle Transition Temperature ◽  
Pressure Vessel Steels ◽  
Brittle Transition Temperature ◽  
Reactor Pressure

Bayesian Uncertainty Evaluation of Charpy Ductile-to-Brittle Transition Temperature for Reactor Pressure Vessel Steels

2020 ◽  
Author(s):  
Hisashi Takamizawa ◽  
Yutaka Nishiyama ◽  
Takashi Hirano
Keyword(s):  
Transition Temperature ◽  
Test Temperature ◽  
Pressure Vessel ◽  
Credible Interval ◽  
Irradiation Embrittlement ◽  
Brittle Transition ◽  
Pressure Vessel Steels ◽  
Brittle Transition Temperature ◽  
Ductile To Brittle Transition ◽  
Reactor Pressure

Abstract The irradiation embrittlement of reactor pressure vessel steels can be predicted using the ductile-to-brittle transition temperature (DBTT) shift obtained from Charpy impact tests. For the structural integrity assessment considering irradiation embrittlement, it is necessary to set margins for various uncertainties. It is important to understand what and how much factors contribute to the uncertainty. In the present study, a 34% credible interval value of Charpy DBTT at a 41J energy level (T41J) was evaluated by estimating the probability distributions of Charpy test data using Bayesian statistics. To fit the Charpy transition curves, a hyperbolic tangent with coefficients whose uncertainties depend on the test temperature was used. The probability distribution of T41J was estimated using Monte Carlo sampling and Bayesian inference. It was clarified that 34% of the credible-interval values of T41J before and after irradiation unchanged for base and weld metals when the number of specimens and test temperature were equivalent under un-irradiated and irradiated conditions. When the Charpy transition curve was determined by 12 specimens loaded in a surveillance test capsule, the estimated uncertainty of T41J was about 5 °C.

Ductile-brittle transition temperature shift controlled by grain boundary decohesion and thermally activated energy in Ni-Cr steels

2019 ◽  
Vol 37 (5) ◽  
pp. 455-458
Author(s):  
Jun Kameda ◽  
Martin L. Jokl
Keyword(s):  
Transition Temperature ◽  
Grain Boundary ◽  
Temper Embrittlement ◽  
Temperature Shift ◽  
High Hardness ◽  
Brittle Transition ◽  
Ductile Brittle Transition Temperature ◽  
Brittle Transition Temperature ◽  
Grain Boundary Decohesion ◽  
Medium Hardness

AbstractTemper embrittlement induced by segregation of metalloid solutes to grain boundary (GB) was evaluated by a shift of the ductile-brittle transition temperature (DBTT). DBTT was found to be linearly correlated with the amount of metalloid on the GB (Xgb) for both dynamic and static displacement rates (dδ/dt) in high and medium hardness steels. Recent first-principles calculations have determined the GB embrittling potency (Δep) of segregated Sb, Sn and P. In both high and medium hardness steels, the slope (α) of DBTT vs. Xgb was found to be linearly dependent on Δep regardless of the segregated solutes. In high hardness steels, the slope is independent of dδ/dt, while in medium hardness steels the α is dependent on dδ/dt. An Arrhenius plot of dδ/dt vs. the reciprocal DBTT was used to drive the thermal activation energy (Eact), which represents a barrier to plasticity. It was found that Eact correlates to a reduction in the GB fracture surface energy. The Eact depends strongly on GB decohesion in high hardness steels but only weakly depends on it in medium hardness steels.

Sign in / Sign up

Export Citation Format

Share Document