A microstructural comparison of two nuclear-grade martensitic steels using small-angle neutron scattering

doi:10.1016/S0022-3115(97)00019-6

Journal of Nuclear Materials

Volume 245, Issues 2–3, June 1997, Pages 131-137

https://doi.org/10.1016/S0022-3115(97)00019-6 Get rights and content

Abstract

Results are presented of a small-angle neutron scattering (SANS) study on two 10–13% Cr martensitic stainless steels of interest for nuclear applications, viz. DIN 1.4914 (MANET specification, for fusion reactors) and AISI 410. The investigation has focussed principally on microstructural effects associated with the differences in chromium content between the two alloys. The size distribution functions determined from nuclear and magnetic SANS components for the two steels given identical heat treatments are in accord with an interpretation based on the presence of ∼ 1 nm size CCr aggregates in the microstructure. Much larger (∼ 10 nm) scattering inhomogeneities with different magnetic contrast are also present and tentatively identified as carbides.

References (19)

R.L. Klueh et al.
J. Nucl. Mater.
(1992)
G. Albertini et al.
J. Nucl. Mater.
(1991)
D. Gavillet et al.
J. Nucl. Mater.
(1992)
G. Albertini et al.
Phys. Rep.
(1993)
R. Coppola et al.
Mater. Lett.
(1995)
G. Albertini et al.
Physica
(1995)
G. Albertini et al.
J. Nucl. Mater.
(1996)
N. Wanderka et al.
J. Nucl. Mater.
(1996)
M. Magnani et al.
Nucl. Instrum. Methods
(1988)

There are more references available in the full text version of this article.

Cited by (10)

On the overaging behaviour of tool steel X38 CrMoV 5-3
2008, Materials Science and Engineering: A
In this study, a combination of small-angle neutron scattering, energy-filtered and conventional transmission electron microscopy and X-ray diffraction has been used to characterize the overaging behaviour of the hot-work tool steel X38 CrMoV 5-3. Hot-work tool steels are mainly used for hot-forging dies, casting dies and extruding tools where high strength is required at high service temperatures. As a consequence, thermal fatigue and softening play the most important role with regard to tool life, and they are strongly influenced by coarsening of the nanometer-sized secondary hardening carbides. The microstructural response to three different overaging treatments in the temperature range of 650–680 °C has been analyzed regarding precipitate types, particle size distributions and corresponding volume fractions. The combination of the different methods used in this study enables a very precise determination of these parameters. This allows for a profound discussion on the evolution of particles occurring in the analyzed samples.
The influence of spin-misalignment scattering on the SANS data evaluation of martensitic age-hardening steels
2007, Acta Materialia
Citation Excerpt :
Fits to the experimental SANS cross-sections of samples A and I-1000, recorded at different applied magnetic fields, as well as dΣR/dΩ, and dΣM/dΩ, calculated according to Eq. (9), are displayed in Fig. 3. Fields up to about 2 T are often used for SANS experiments on steel [6–9] because they can be produced easily using conventional electromagnets; therefore dΣM/dΩ is displayed for the field of 1740 mT. In a classical SANS data evaluation dΣ/dΩ∥ is expected to correspond to the nuclear cross-section. The as-quenched sample (sample A) shows a strong dependence of dΣ/dΩ∥ on the applied magnetic field (Fig. 3a).
Small-angle neutron scattering has proved to be a valuable technique for probing precipitates in steels. The investigated sample is thereby exposed to a large magnetic field and is assumed to consist of a single domain with all the magnetic moments perfectly aligned with the external field. In this situation the dominating magnetic scattering contrast is expected to stem from the differences between the magnetization values of matrix and particles. However, the present work shows that strong additional scattering can be present which is due to spin misalignment. The effects of this spin-misalignment scattering are discussed as being exemplary for differently heat-treated martensitic steel samples. It is revealed that the amount of spin-misalignment scattering is very sensitive to the applied heat treatment and is most pronounced in the as-quenched condition. In particular, when considering nuclear scattering curves the influence of spin-misalignment scattering may be very large and must not be neglected.
Morphology of carbide precipitates in solution quenched PH13-8 Mo stainless steel: A small-angle neutron scattering investigation
2005, Materials Science and Engineering: A
This article reports the small-angle neutron scattering (SANS) and the transmission electron microscopy (TEM) investigations on solution quenched PH13-8 Mo stainless steel. The metallic carbide precipitates of parallelepiped like morphology, as revealed by TEM, have been mainly responsible for the strong scattering signal in SANS measurements. Scattering signal from the needle like austenites, which have been also identified by TEM, remains insignificant because of the poor scattering contrast between the austenites precipitates and the martensite matrix. Shape of the normalized scattering profile varies significantly with the specimen thickness. These variations of the scattering profiles could arise due to the two factors, namely: (i) the multiple scattering of the neutrons at small-angles and (ii) the double Bragg reflections. In the present case, it has been established that the contribution in the scattering signal due to the double Bragg reflection is quite insignificant compared to that from the multiple scattering. The single scattering profile, extracted from the multiple scattered profiles of the samples, has been analyzed in the light of polydisperse cylindrical particle model as well as with polydisperse parallelepiped particle model, assuming fixed aspect ratio of the precipitates, in order to obtain the size distribution of the precipitates.
Microstructural characterisation of F82H-mod. steel using small-angle neutron scattering
1998, Journal of Nuclear Materials
Small-angle neutron scattering (SANS) measurements have been carried out on samples of F82H-mod. martensitic steel submitted to different treatments: (a) hardening, (b) tempering and (c) ageing. Size distribution functions referable to the precipitates, formed during the different treatments are obtained both for nuclear and magnetic SANS components. The results, discussed making reference to transmission electron microscopy (TEM) observations and microhardness measurements, show that while samples of groups (a) and (c) exhibit a stable microstructure, marked differences are detected varying the tempering temperature, especially at 550°C (where a fine precipitation is observed) and for temperatures higher than 850°C (formation of delta ferrite).
Microstructural investigation, using polarized neutron scattering, of a martensitic steel for fusion reactors
1998, Acta Materialia
Small- and wide-angle polarized neutron scattering has been used to investigate the microstructure of modified martensitic steel DIN 1.4914 (“MANET”-type) developed as a potential candidate for the “first wall” of future fusion reactors. The nuclear–magnetic interference term and the comparison of the size distribution functions, obtained from the nuclear and from the magnetic scattering components, show that for quench temperatures lower than 1200°C three kinds of microstructural inhomogeneities can be identified: (a) tiny C–Cr elementary aggregates (1 nm or less in size), (b) larger (1–25 nm) Fe-carbides, (c) much larger inhomogeneities arising either from M₂₃C₆ precipitates or from fluctuations in the Cr distribution. The scattering data are also compared with those previously obtained on the same samples from a conventional SANS instrument and the influence of the available Q-range on the accuracy of the obtained size distribution functions is discussed.
Chromium redistribution in thermally aged and irradiated ferritic-martensitic steels
1998, Materials Science and Engineering: A
Ferritic–martensitic steels containing 8–12 at.% chromium are considered as structural materials for spallation sources and fusion reactors. Materials will be subjected to intense damage rates, e.g. 50–100 dpa per year at full power. Therefore, the behavior under irradiation of these steels must be investigated. Our earlier dual-beam irradiation results on the DIN 1.4914 steel showed a decomposition into chromium-enriched and chromium-depleted regions. The mean concentration of the chromium-depleted regions was found to be 5.19±0.32 at.% after irradiation at 500°C to a fluence of 50 dpa, as measured by atom probe field-ion microscopy. The chromium distribution in the matrix of the DIN 1.4914 steel after thermal ageing at temperatures between 400 and 600°C has been investigated for times up to 17 000 h. The carbides were characterized by means of transmission electron microscopy and extraction replicas. The concentrations of the constituents of the matrix were measured by means of atom probe. The mean chromium concentrations in the matrix are found to be 8.66±0.32, 4.5±0.3, and 7.2±0.4 at.%, after ageing at 400, 500, and 600°C, respectively. The matrix contains virtually no carbon. The results are discussed in terms of phase decomposition and species segregation.

View all citing articles on Scopus

View full text

A microstructural comparison of two nuclear-grade martensitic steels using small-angle neutron scattering

Abstract

J. Nucl. Mater.

J. Nucl. Mater.

J. Nucl. Mater.

Phys. Rep.

Mater. Lett.

Physica

J. Nucl. Mater.

J. Nucl. Mater.

Nucl. Instrum. Methods