INTERGRANULAR IMPURITY SEGREGATION AND EMBRITTLEMENT IN NEUTRON-IRRADIATED IRON-ALLOYS

Intergranular solute segregation and embrittlement induced during neutron irradiation (9.4 x 10(22) n/m2 at 668 K) in iron alloys doped with copper (Cu), phosphorus (P) and/or carbon (C) have been investigated using small punch (SP) test techniques and scanning Auger microscopy (SAM). It was found that Cu and/or P containing alloys exhibited a greater effect of irradiation on hardening than C-containing alloys. The neutron irradiation increased more greatly the ductile-brittle transition temperature (DBTT) in the Cu-doped alloy compared with the other alloys. Intergranular and transgranular fracture occurred in the alloys without and with C, respectively. The neutron irradiation did not change the fracture mode. Fracture surface SAM analyses demonstrated that while the neutron irradiation enhanced S-segregation in the Cu-doped alloy without P-segregation, it decreased S-segregation and increased P-segregation in the P-containing alloys. The relationship of neutron irradiation-induced intergranular solute segregation to embrittlement is discussed.