Formation and recovery of Cu precipitates in Fe–Cu model alloys under varying heat treatment

Abstract

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.

Exploration on the Effect of Pretreatment Conditions on Hydrogen-Induced Defects in Pure Titanium by Positron Annihilation Spectroscopy

“…The CDB-PAS spectrum accumulates about 10 7 counts in 8 h by collecting momentum distribution information. Through normalization with the CDB measurement results of the hydrogen-charged samples, the defect structure and element information in the hydrogen-charged samples were obtained [32,33]. In order to further explore the chemical state and phase change of hydrogen in charged samples, the phase structure of all the samples was compared and analyzed with a D8 Advance X-ray diffractometer (XRD).…”

Research of Cu clusters and Cu–V complexes formed at early aging stage in FeCu alloys by low temperature positron spectroscopy

“…The formation of Cu clusters plays a key factor in the reactor pressure vessel (RPV) steels for deterioration of performance caused by neutron irradiation [1][2][3][4][5]. Under strong neutron irradiation conditions, atomic displacement is prone to occur in the material, resulting in a large number of microscopic defects (vacancies, dislocations, and grain boundaries) [6].…”

“…Therefore, it is too difficult to detect the precipitation process of Cu atoms in the early stage of aging. Te Zhu et al has studied the recovery of Cu precipitates in FeCu model alloys after annealed at 1173 K and found the tiny Cu precipitates formed during annealing at 1173 K. However, the Cu precipitate in FeCu alloys with low content is too small to be detected by conventional coincidence Doppler broadening measurement (CDB) [5].…”