Thermal-Ageing and Ion-Irradiation Enhanced Intergranular P Segregation in Low Alloy Steel Welds

Quantitative study of solute segregation phenomenon is crucial in material science. In the present study, the influence of thermal ageing and ion irradiation (both at 400°C) on intergranular P segregation behavior was studied by a correlative Electron Backscattering Diffraction (EBSD)/Transmission Kikuchi Diffraction (TKD)/Atom Probe Tomography (APT) methodology. The co-segregation of P, C, Si, Mn, Ni, Cr and Mo appears at Grain Boundaries (GBs). There is an increased P segregation for all the detected GB types in both thermally-aged and ion-irradiated welds. Thermodynamic and kinetic predictions confirm the Radiation Enhanced Segregation (RES) mechanism of P at GBs under ion irradiation. The ternary Fe-P-C model overestimates P segregation level in a multicomponent system.