The Radiation Hardening and Embrittlement of a Mild Steel Submerged-Arc Weld

Abstract

This paper provides details of accelerated irradiation experiments on a Magnox mild steel submerged-arc weld at mean irradiation temperatures of 165°C and 269°C. The irradiation-induced changes in mechanical properties and weld microstructure have been determined. Irradiation increased the 40J transition temperature and the yield stress. The increase in transition temperature at a given dose was rather higher in the lower temperature irradiations. Irradiation-induced precipitates of about 2nm diameter were produced in both series of irradiations. Small angle neutron scattering data indicated a precipitate composition of about 75Cu25Mn (at%). Electron microscopy confirmed the presence of copper-rich precipitates of that size. The irradiation dose ranges covered the development stage of the precipitation. The directly measured and (yield stress) derived transition shift data were interpreted satisfactorily using a mechanistically based model involving a matrix damage component and a component attributable to copper precipitation.

Development of an interatomic potential for phosphorus impurities in -iron

“…Phosphorus is one of the major causes of embrittlement of nuclear reactor pressure vessel (RPV) steels [1]. A huge enhancement of the concentration of phosphorus (P) atoms at grain boundaries is observed in samples of RPV steels taken from nuclear reactors [2]. This leads to a decrease in the grain boundary cohesion and consequently to a shift of the ductile-to-brittle transition temperature.…”

Grain Boundary Phosphorus Segregation in Thermally Aged Low Alloy Steels

“…It was reported that grain boundary segregation of phosphorous was observed after re-irradiation of previously irradiated weld surveillance specimens in the Magnox reactors in the UK. 2,3) A remarkable grain boundary phosphorous segregation was also observed in the weld of the pressure vessel of Russian VVER. 4,5) Therefore, several studies on the effects of phosphorus segregation on intergranular fracture 6,7) and on the segregation modeling [8][9][10] have been carried out.…”

Solute effects on edge dislocation pinning in complex alpha-Fe alloys

“…Next, the interaction with dislocation lines of dislocation loops has been studied for different solute concentrations by Terentyev et al [5], concluding that Mn segregated in the core of loops causes an increment in the yield point and finally increases the hardening. P is also known to segregate to heterogeneities in RPV steels, mainly grain boundaries and dislocations, causing embrittlement, grain boundary decohesion and thereupon a shift in the ductile-to-brittle transition temperature [6][7].…”

“…One sample with a dipole of edge dislocations is generated using linear elasticity [12] in a crystallite with the normal axes x, y and z oriented as the [ , where a 0 is the lattice parameter of Fe [4][5][6][7][8][9][10][11][12][13].…”