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The purpose of the study detailed in this paper is to investigate the evolution of microstructural defects in the Fe‐9Cr binary alloy induced by isochronal annealing from 373 to 1223 K. Positron annihilation lifetime spectroscopy (PALS), Doppler broadening spectroscopy (DBS), positron annihilation lifetime calculation, and transmission electron microscope (TEM) are used to analyze and characterize the change of defect concentration, defect type and the micro‐morphology in the Fe‐9Cr alloy as a function of the annealing temperature. The experimental results showed that, a large number of vacancies and dislocations were found to exist in the untreated Fe‐9Cr alloy. The monovacancy (186.2 ps) in the Fe‐9Cr alloy migrated during annealing from room temperature to 573 K. The annealing temperature at 773 K produce aggregation of dislocations and the formation of dislocation networks, as well as their heterogeneous distribution. When the temperature is further increased to 1073 K, most of the vacancies and dislocations are recovered and a bcc‐fcc phase transmition occurred in Fe‐9Cr model alloy. The dislocation density is continuous decreased with the increase of annealing temperature, the recovery is obvious from 773 K annealing to 1073 K annealing in Fe‐9Cr alloy. [ABSTRACT FROM AUTHOR]

Fe-Cu systems, model alloys of nuclear reactor pressure vessel (RPV) steels, heat treatments by annealing and quenching, are studied by the positron annihilation technique and high-resolution SEM. The different effect of annealing and quenching on the formation of Cu precipitates was discussed. The ultrafine Cu precipitates, which are formed in Fe- x wt.% Cu ( x = 1.0 and 1.5) alloys after thermal annealing, are observed clearly and no obvious Cu precipitates were found in the quenched alloys. The annealing temperature has an effect on the concentration of Cu precipitates, which leads to a change of the proportion of positron annihilation in the Cu precipitates, and this can be reflected by the change of the W parameters. Positron annihilation Doppler broadening spectroscopy results show that Cu precipitates formed during annealing at 1173 K still exist when the annealing temperature is higher than 1453 K. SEM measurements were used to observe the size and the distribution of Cu precipitates in the samples, after using different annealing temperature. [ABSTRACT FROM AUTHOR]