The dependence of void swelling bias factor on iron concentration in V-Fe alloys

From data on the microstructure of pure V, V-2 at.% Fe and V-5 at.% Fe alloys 50 keV V-51(+)-ion irradiated at 450, 560 and 625 degrees C and 5 x 10(-3) dpa/s to damage doses up to 40 dpa, the bias factor of swelling has been determined. This factor increases from similar to 1% to similar to 6% as the square of iron concentration and depends slightly on temperature and dose. To explain such a behavior the bias factor for V-Fe alloys has been calculated taking into account the radiation-induced segregation (RIS) phenomenon. Model segregation profiles as well as simple interaction potentials between point defects and sinks have been used in the calculations. It is shown that a strong bias factor dependence on iron concentration can be obtained by assuming that RIS of iron atoms influences the void bias but not the dislocation bias, i.e. if RIS does not follow fast climbing dislocations.