Experimental analysis reveals non-additive hardening in prestrained reactor steel, suggesting dislocations trap solutes and mitigate radiation damage.
The combined effects of prestrain and neutron irradiation on reactor pressure vessel (RPV) steel remains an understudied area, particularly for surveillance samples. Here SA508 grade 3 steel is investigated in four conditions: baseline, prestrained (5%), irradiated (approximately 0.1 dpa at 293 o C) and irradiated prestrained. Tensile tests showed that whilst both prestrain and irradiation increased yield stress, the combined case experienced a lower increase than the sum of the individual contributions indicating a partial mitigation effect. Atom probe tomography (APT) detected limited solute clustering in the irradiated samples. However, significant amounts of co-segregation was found with Mn, Si, Cu, Ni and P. The limited clustering was attributed to the lower neutron flux of surveillance samples relative to test reactor data of the same material. The APT showed a depletion of solutes around dislocations, indicating that prestrain-induced dislocations act as solute traps and that prestrain and irradiation hardening are not additive.
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Stroud et al. (2026) studied this question.
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