Effects of dose rate change under irradiation on hardening and microstructural evolution in A533B steel

Abstract

Iron-ion irradiations were carried out for 0.09wt%Cu A533B steel specimens at 2908C to investigate effects of dose rate change during irradiation; the irradiations consisted of the base irradiation (with an unchanged dose rate) and an additional one with changed dose rates from 1 to 50 times that of the base one. Nano-indentation hardness measurements showed that the increase in hardness was higher for lower dose rate of the base irradiation. A similar trend was identified during the additional irradiation. Transmission electron microscope (TEM) and three-dimensional atom probe (3DAP) analyses were carried out for the quantitative characterization of defect features. Mn/Ni/Si/Cu-enriched clusters and dislocation loops were observed in all specimens. The increase in hardness mainly depended on the formation of the solute atom clusters. The square root of the volume fraction of the solute atom clusters provided a good correlation with the increase in hardness. The effects of dose rate and dose rate change during irradiation were explained by the formation of solute atom clusters.

Characterizing accelerated precipitation in proton irradiated steel

“…1). Embrittlement, as measured by a positive shift in ductile-to-brittle transition temperature or an increase in yield stress, correlates well with the square root of precipitate volume fraction [7,[20][21][22][23][24][25]. This relationship follows the ideas of Russell-Brown precipitate hardening [26,27], though more refined hardening models may better describe experimental data [21].…”

“…Taking the sink strength S as the dislocation density, values between 10 13 m −2 and 10 15 m −2 are expected in RPV steels (see e.g. [23,51,54,100]). With S = 10 14 m −2 for example, D v 10 −15 m 2 s −1 at 300 • C, consistent with suppressed D v associated with higher effective vacancy migration energy 1.2 eV in ferrite compared to pure iron.…”

Micromechanical testing of unirradiated and helium ion irradiated SA508 reactor pressure vessel steels: Nanoindentation vs in-situ microtensile testing

“…The dpa rate obtained from this work using helium ions was 1.6 × 10 -6 dpa s -1 , an order of magnitude larger. Usually, lower dose rates induce higher degree of hardening in ion implanted materials [63,64]. In this work, the larger dpa rate used induced a higher hardening, however, this can be related to the different damage induced by helium ions compared to neutrons as the implanted bubbles contributed to approximately 600-800 MPa increase in yield stress.…”

Effect of Heavy Ion Irradiation Dosage on the Hardness of SA508-IV Reactor Pressure Vessel Steel

“…Ion irradiation is one of the best methods for investigation of irradiation embrittlement [7], and provides a rapid and flexible way to achieve high doses without the hazards induced by activation of the materials [8]. Furthermore, the displacement cascades induced by ion irradiation are similar to those induced by neutron irradiation [9].…”