Uncertainties and assumptions associated with APT and SANS characterisation of irradiation damage in RPV steels

Comparison between SANS and APT measurements in a thermally aged Fe-19 at.%Cr alloy

“…However that was not sufficient for removing the discrepancy on α′ particles' composition. Prior work of Hyde et al [20] on radiation induced clusters in Reactor Pressure Vessel (RPV) steels using APT and SANS lead to similar conclusions. Recently, Couturier et al [23] developed a common framework for comparing SAXS (Small Angle X-ray Scattering) with APT results when applied to spinodal decomposition in Fe-Cr steels.…”

“…Moreover, APT relying on physics of field evaporation of atoms, artefacts may appear that can artificially modify shape and composition of the observed particles [14][15][16][17][18][19]. Respective weaknesses and strengths of SANS and APT make them complementary techniques and cross-checking results obtained for the same alloys is of a large interest [20][21][22]. Nevertheless, one very important point is still pending.…”

“…Except in the case of Couturier et al [23], the main issue between APT and SANS concerns the composition of precipitates. As stressed by Hyde et al [20], solution of this issue is hidden behind the limitations of the two techniques and assumptions used for data treatment. One of the most obvious explanation could be the so called local magnification effect [14,27] observed in APT experiments when two phases present different evaporation fields.…”

“…Another possible explanation of the discrepancy between SANS and APT results is that classical assumptions on which SANS data treatment relies are not appropriate for this system. Hyde et al [20] showed that, depending on the assumptions made very different results can be obtained using SANS. It must be pointed out that only reasonable assumptions were considered.…”

A combined APT and SANS investigation of α′ phase precipitation in neutron-irradiated model FeCrAl alloys

“…First, both techniques were unable to resolve small clusters. SANS has an instrument-dependent physical resolution limit for observed cluster diameters that is usually in the range of 0.51.5 nm [63,64]. APT is able to resolve precipitates smaller than this, but clusters that are on the same length scale as those found as a result of composition uctuations in a random solid solution are not considered.…”