SANS Investigation of Irradiated A533-B Steels Doped with Phosphorus

Abstract

Small angle neutron scattering (SANS) techniques have been employed to study the nature of the radiation damage and its dependence on phosphorus concentration at two different copper levels (0.002 and 0.3%) in a set of laboratory melts of A533-B steel irradiated to ˜2.5 × 1019 n/cm2 at 288°C under test reactor conditions. In all materials, distributions of clusters were found with number densities ˜ 1017 to 1018 cm-3 and diameters ˜ 1 to 2 nm. Cluster volume fractions were approximately an order of magnitude higher in the 0.3% Cu steels, which were associated with greater radiation strengthening and embrittle-ment. Magnetic and nuclear scattering data are best interpreted in terms of mixed clusters containing Cu, Mn, and Ni; increasing P content leads to some refinement of the cluster distributions. In the low-Cu steels embrittlement is also associated with radiation hardening via cluster formation promoted by increasing phosphorus content.

The Dominating Mechanisms for the Formation of Solute-Rich Clusters in Steels under Irradiation

“…The data to which these correlations are fit come from vessel surveillance [3], decommissioned vessels [4], or irradiation campaigns in materials testing reactors (MTR) [5][6][7]. For a longer-term application, effort has been put to develop fully physically informed suites of computer simulation codes, aimed at predicting RPV steel radiation hardening [8,9], including microstructural examination studies in support of modelling [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28]. These studies revealed that radiation hardening in RPV steels, as well as in other types of iron alloys such as high-Cr ferritic-martensitic (F-M) materials, is mainly the consequence of the formation of high densities (~10 23 m -3 ) of nanometre-size solute-rich clusters (NSRC), which act as obstacles to dislocation motion [29,30].…”

“…Due to their small size and coherence with the matrix (body centred cubic -bcc -structure), they are not easily resolvable to conventional transmission electron microscopy (TEM). Their existence has been revealed mainly through other microstructural characterization techniques, such as atom probe tomography (APT) [10][11][12][13][14][15][16][17][18][19][20][21]32] and small angle neutron scattering (SANS) [24][25][26][27][28]. Recently, though, modern scanning TEM (STEM) techniques coupled with energy dispersive spectroscopy (EDS) allowed these clusters to be resolved as well [33].…”

Influence of manganese on mechanical properties, irradiation susceptibility and microstructure of ferritic steels, alloys and welds

“…Small angle neutron scattering showed that Cu rich precipitates developed and then saturated in size with increasing dose in irradiated steels. [103][104][105] These irradiations were between 190 and 290uC and the resulting precipitates had mean diameters of y2 nm. To interpret the SANS signals, and the influence of applied magnetic fields on the SANS response, it was necessary to assume that the precipitates also contained other elements, e.g.…”

“…Precipitates with 25Mn/75Cu (at-%) occurred in C-Mn SAWs 94 while 23Mn/11-17Ni/balance Cu (at-%) were found in variants of A533B steel with 0?70%Ni and differing P levels. 105 Finally, from the work of Buswell et al 106 on Cu bearing model Mn-Mo steels with increasing Ni levels of 0?10, 0?4, 0?59, 0?8 and 1?12 wt-%, precipitates with 29-35Mn/5Ni/balance Cu occurred in steels with ,0?59%Ni, while 26Mn/24Ni/balance Cu and 34Mn/32Ni/balance Cu (at-%) respectively occurred in higher Ni steels. These analyses fell within two differing compositional bands in the Cu-Ni-Mn ternary diagram.…”

Small Angle Neutron Scattering Modeling of Copper-Rich Precipitates in Steel

“…The sin2a factor arises from the scattering interaction between the neutron and the atomic magnetization of the scattering material, sinla= I--(?. ;)~ (2) where K is the unit magnetization vector and E is the unit diffraction vector and a is the angle between the two unit vectors. The scattering densities are given by the nuclear or magnetic scattering amplitude per volume and are usually calculated on a per atom basis.…”