Composition Effects on the Radiation Embrittlement of Iron Alloys

The effect of copper, phosphorus and nickel on the radiation embrittlement was investigated by using an irradiation experiment at surveillance positions in two Russian VVER-type reactors with 8 iron-base testing alloys. Their chemical composition varied between 0.015 to 0.42 % Cu, 0.002 to 0.039 % P, 0.01 to 1.98 % Ni, 0.09 to 0.37 % Si, and 0.35 to 0.49 % Mn. Charpy-V impact tests and tensile tests were performed with specimens machined from these alloys. The specimen were tested in the as-received state, in the irradiated state (fluence: 1×10 19 and 8×10 19 cm -2 [En > 0.5 MeV]) and in the post-irradiation annealed state.
Irradiation produces strong hardening and embrittlement. The effect increases with the Cu and P content. Ni causes an additional embrittlement. It does not depend on the Ni content within the range of 1.1 to 2 % Ni. The irradiation effect can be eliminated by annealing at 475 °C / 100 h but not absolutely in the case of high Cu or P content.
Small angle neutron scattering experiment at these alloys show that not only the volume fraction but also the type of the radiation defects vary in dependence on the composition of the alloys.