Influence of carbon addition on neutron-induced void swelling of Fe-15Cr-16Ni-0.25Ti model alloy

Addition of 0.05 wt% C to a model Fe-15Cr-16Ni-0.25Ti quaternary model alloy leads to a reduction in neutron-induced swelling at 430 oC. The transient regime of swelling is prolonged by carbon addition, most strongly at lower dpa rates. Contrary to the swelling behavior observed in carbon-free Fe-15Cr-16Ni and Fe-15Cr-16Ni-0.25Ti model alloys irradiated in the same experiment, Fe-15Cr-16Ti-0.25Ti-0.05C does not exhibit a strong dependence of swelling on dpa rate. It appears that carbon's role, while not yet well-defined, operates via a solute-based or TiC complex mechanism rather than by a precipitate-based mechanism. A model is proposed whereby carbon stabilizes loop microstructures against unfaulting, where unfaulting is known to be a prerequisite to formation of the glissile dislocation network needed to establish a high swelling rate. This stabilization is proposed to counteract the tendency of loop unfaulting to occur more strongly at low dpa rates