Effect of irradiation on phosphorus segregation

Phosphorus strongly segregated to the surface during irradiation of austenitic-type alloys in the temperature range 775-925 K. Much weaker but measurable radiation induced segregation of phosphorus occurred in a Ni + 0.03% P alloy. Irradiation under similar conditions produced no measurable phosphorus segregation in the ferritic HT-9 or Fe + 0.03% P alloy. The lack of segregation in the ferritic alloys was suggested to result from a weak point defect - impurity interaction in the bcc iron structure while a strong interaction was suggested for the fcc iron structure. The slow accumulation of radiation damage in bcc iron alloys is also consistent with a lack of observables segregation. The evidence strongly suggests a radiation induced mechanism but a radiation enhanced, thermally activated equilibrium segregation cannot be ruled out. (orig.)