The properties and microstructures of irradiated 4N- or 2N8-purity Fe-9Cr alloys were studied. The irradiation was usually performed, at 255 or 290C, to 0.3dpa. The increment in the yield strengths of the high-purity and low-purity alloys, due to irradiation, was 225 and 170MPa, respectively. The elongation of the high-purity alloy was markedly reduced by irradiation, and was smaller than that of the low-purity alloy. Transmission electron microscopic observations revealed dislocation loops in the high-purity and low-purity alloys. Precipitates which were about 6nm in diameter were observed on loops in the high-purity alloy, but only dislocation loops were observed in the low-purity alloy. On the basis of the theory of dispersed-barrier hardening, the barrier strength factors of the dislocation loops in the high-purity and low-purity alloys were estimated to be about 0.4 and 0.3, respectively. The increase in the strength factor of the loops in the high-purity alloy was suggested to be related to the formation of the precipitates on the loops. A decrease in the ductility of the alloy was also attributed to the formation of precipitates on loops.

Damage Structures and Mechanical Properties of High-Purity Fe-9Cr Alloys Irradiated by Neutrons. E.Wakai, A.Hishinuma, K.Usami, Y.Kato, S.Takaki, K.Abiko: Materials Transactions, 2000, 41[9], 1180-3