The Modelling of Irradiation Embrittlement in Submerged-Arc Welds

Abstract

Until very recently, the irradiation embrittlement behaviour of submerged-arc welds has been interpreted in terms of two mechanisms, namely a matrix damage component and an additional component due to the irradiation-enhanced production of copper-rich precipitates. However, some of the weld specimens from a recent accelerated re-irradiation experiment have shown high Charpy shifts which exceeded the values expected from the measured shift in yield stress. Microstructural examination has revealed the occurrence of intergranular fracture (IGF) in these specimens, accompanied by grain boundary segregation of phosphorus. Theoretical models were developed to predict the parametric dependence of irradiation-enhanced phosphorus segregation on experimental variables. Using these parametric forms, along with the concept of a critical level of segregation for the onset of IGF instead of cleavage, a three mechanism trend curve has been developed. The form of this trend curve, taking into account IGF as well as matrix and copper embrittlement, is thus mechanistically based. The constants in the equation, however, are obtained by a statistical fit to the actual Charpy shift database.

Hardening and microstructural evolution of A533b steels irradiated with Fe ions and electrons

“…3 (a) through (d), respectively. The dashed line indicates the temperature dependence proposed by Bolton et al [19] for matrix defects normalized to the observed RT hardening. In this previous study, a qualitatively similar general trend was observed at 0.1 dpa, with the hardness decreasing as the irradiation temperature increased, and the level of radiation-induced hardness was nearly the same with or without added Cu at all temperatures.…”

Influence of manganese on mechanical properties, irradiation susceptibility and microstructure of ferritic steels, alloys and welds

“…For Charpy shifts, Δ T 41 J was given by a two or three term equation37 where B ΔT and A ΔT represented Cu precipitation and matrix displacement damage as before; the third term represented the possibility of intergranular embrittlement from grain boundary P segregation as affected by dose, irradiation temperature, time and %P. In many C–Mn steel applications the third term was small, hence both embrittlement and hardening arose from similar two-term mechanisms.…”

Charpy Impact Energy Data: A Markov Chain Monte Carlo Analysis

“…The relationship adopted to model Charpy impact energy data has a form which re¯ects the physical processes involved in neutron radiation damage. Mechanistic models for the eect of neutron irradiation on mechanical properties of steels have been developed by Buswell and Jones (1993) and Bolton et al (1994). According to these models, the changes in Charpy impact energy are due to two dierent hardening processes, copper precipitation and dislocation, and one non-hardening mechanism, grain boundary embrittlement.…”