Irradiation-induced structural changes in martensitic steel T91 (original) (raw)
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Microstructure evolution of T91 steel after heavy ion irradiation at 550 °C*
Chinese Physics B, 2021
Fe-Cr ferritic/martensitic (F/M) steels have been proposed as one of the candidate materials for the Generation IV nuclear technologies. In this study, a widely-used ferritic/martensitic steel, T91 steel, was irradiated by 196-MeV Kr+ ions at 550 °C. To reveal the irradiation mechanism, the microstructure evolution of irradiated T91 steel was studied in details by transmission electron microscope (TEM). With increasing dose, the defects gradually changed from black dots to dislocation loops, and further to form dislocation walls near grain boundaries due to the production of a large number of dislocations. When many dislocation loops of primary a 0/2〈 111 〉 type with high migration interacted with other defects or carbon atoms, it led to the production of dislocation segments and other dislocation loops of a 0 〈 100 〉 type. Lots of defects accumulated near grain boundaries in the irradiated area, especially in the high-dose area. The grain boundaries of martensite laths acted as imp...
SANS and TEM of ferritic–martensitic steel T91 irradiated in FFTF up to 184dpa at 413°C
Journal of Nuclear Materials, 2013
Ferritic-martensitic steel T91 was previously irradiated in the Materials Open Test Assembly (MOTA) program of the Fast Flux Test Reactor Facility (FFTF) at 413°C up to 184 dpa. The microstructure was analyzed by small angle neutron scattering (SANS) and transmission electron microscopy (TEM). Both SANS and TEM revealed a large fraction of voids with an average size of 29-32 nm leading to a calculated void swelling of 1.2-1.6% based on the volume fraction of the voids in the sample. SANS gave no indication of second phase particles having formed under irradiation in the material. Using TEM, one zone was found where a few G-phase particles were analyzed. Quantities were however too low to state reliable particle densities. No alpha prime (a 0 ) or Laves phase were observed in any of the investigated zones.
Journal of ASTM International, 2005
Martensitic/ferritic steels (containing 7-13 % Cr) are candidate materials for internal structures in pressurized water, fast breeder, and fusion reactors. Approval for use requires verification of structural stability under neutron irradiation in relation to the evolution of mechanical properties. In this context, several conventional and Reduced Activation (RA) martensitic materials were neutron irradiated at 325°C up to 6 dpa. They were investigated by Small Angle Neutron Scattering (SANS) under a magnetic field after various doses.
Study of irradiated mod.9Cr–1Mo steel by synchrotron extended X-ray absorption fine structure
Journal of Nuclear Materials, 2013
Synchrotron extended X-ray absorption fine structure (EXAFS) spectroscopy measurements were performed to study the dose dependence of and alloying effects on irradiation-induced changes in the local atomic environments in a mod.9Cr-1Mo ferritic-martensitic steel. The measurements were carried out at room temperature on non-irradiated and irradiated specimens exposed to 1, 4, and 10 displacement per atom (dpa) at 40-70°C. The EXAFS data for Fe, Cr, Mo, and Nb K-edges were recorded, and the local structure close to the X-ray absorbing atom was determined. Irradiation caused significant reductions in peak amplitude in the Fe, Mo and Nb K-edge Fourier transformed EXAFS. The data showed a systematic decrease in coordination number of neighbor atoms with increasing irradiation dose, and the dose dependence of the coordination loss was dependent on the specific element. The measured damage around Fe sites can be correlated with the dpa value, while the loss of near neighbors around Mo saturated at 1 dpa. The coordination in the Fe matrix was reduced less by irradiation than either the coordination of Mo in solution or Nb in carbides. It was demonstrated that EXAFS can provide a detailed, atomic level description of radiation damage in complex alloy systems.
Advanced Materials Research, 2013
The paper presents some results of a complex research of 12Cr18Ni10Ti stainless steel in the initial, deformed and irradiated ( 14 84 36 + Kr , E=130MeV, F max =9x10 15 ions/сm 2 ) states using magnetometry, X-ray diffraction (XRD) and scanning electron microscopy (SEM) with electron backscattered diffraction (EBSD -analysis). Application of the EBSD method revealed differences between the non-irradiated and irradiated 12Cr18Ni10Ti steel specimens consisting in the fact that in the surface layer of an irradiated sample α-and ε -phases are formed. It was established that the fluence value affects the amount of magnetic α-phase. The study of the martensite α-phase morphology showed that in the deformed steel specimens there is αʹ-martensite of two scale levels.
Journal of Nuclear Materials, 1995
Tensile, Charpy, and transmission electron microscopy specimens of two conventional steels, modified 9Cr1Mo (9Cr1MoVNb) and Sandvik HT9 (12Cr1MoVW), and two reduced-activation steels, Fe9Cr2W-0.25V-0.1C (9Cr2WV) and Fe9Cr2W0.25V0.07V0.07TaTa0.1C (9Cr2WVTa), were irradiated in the Fast Flux Test Facility. Before irradiation, M23C6 was the primary precipitate in all four steels, which also contained some MC. Neutron irradiation did not substantially alter the M23C6 and
Microstructural evolution of P92 ferritic/martensitic steel under argon ion irradiation
Irradiation damage in P92 ferritic/martensitic steel irradiated by Ar + ion beams to 7 and 12 dpa at elevated temperatures of 290°C, 390°C and 550°C has been investigated by transmission electron microscopy, scanning electron microscopy and atomic force microscopy. The precipitate periphery (the matrix/carbide interface) was amorphized only at 290°C, while higher irradiation temperature could prevent the amorphization. The formation of the small re-precipitates occurred at 290°C after irradiation to 12 dpa. With the increase of irradiation temperature and dose, the phenomenon of re-precipitation became more severe. The voids induced by irradiation were observed after irradiation to 7 dpa at 550°C, showing that high irradiation temperature (≥ 550°C) was a crucial factor which promoted the irradiation swelling. Energy dispersive X-ray analysis revealed that segregation of Cr and W in the voids occurred under irradiation, which may influence mechanical properties of P92 F/M steel.
Journal of Nuclear Materials, 2003
Five reduced activation (RA) and four conventional martensitic steels, with chromium contents ranging from 7 to 12 wt%, were investigated by small angle neutron scattering (SANS) under magnetic field after neutron irradiation (0.7-2.9 dpa between 250 and 400°C). It was shown that when the Cr content of the b.c.c. ferritic matrix is larger than a critical threshold value ($7.2 at.% at 325°C), the ferrite separates under neutron irradiation into two isomorphous phases, Ferich (a) and Cr-rich (a 0 ). The kinetics of phase separation are much faster than under thermal aging. The quantity of precipitated a 0 phase increases with the Cr content, the irradiation dose, and as the irradiation temperature is reduced. The influence of Ta and W added to the RA steels seems negligible. Cold-work pre-treatment increases slightly the coarsening of irradiation-induced precipitates in the 9Cr-1Mo (EM10) steel. In the case of the low Cr content F82H steel irradiated 2.9 dpa at 325°C, where a 0 phase does not form, a small irradiation-induced SANS intensity is detected, which is probably due to point defect clusters. The a 0 precipitates contribute significantly to the irradiation-induced hardening of 9-12 wt% Cr content steels.
Microstructural development under irradiation in European ODS ferritic/martensitic steels
Journal of Nuclear Materials, 2006
Oxide dispersion strengthened steels based on the ferritic/martensitic steel EUROFER97 are promising candidates for a fusion reactor because of their improved high temperature mechanical properties and their potential higher radiation resistance relative to the base material. Several EUROFER97 based ODS F/M steels are investigated in this study. There are the Plansee ODS steels containing 0.3 wt% yttria, and the CRPP ODS steels, whose production route is described in detail. The reinforcing particles represent 0.3-0.5% weight and are composed of yttria. The effect of 0.3 wt% Ti addition is studied. ODS steel samples have been irradiated with 590 MeV protons to 0.3 and 1.0 dpa at room temperature and 350°C. Microstructure is investigated by transmission electron microscopy and mechanical properties are assessed by tensile and Charpy tests. While the Plansee ODS presents a ferritic structure, the CRPP ODS material presents a tempered martensitic microstructure and a uniform distribution of the yttria particles. Both materials provide a yield stress higher than the base material, but with reduced elongation and brittle behaviour. Ti additions improve elongation at high temperatures. After irradiation, mechanical properties of the material are only slightly altered with an increase in the yield strength, but without significant decrease in the total elongation, relative to the base material. Samples irradiated at room temperature present radiation induced defects in the form of blacks dots with a size range from 2 to 3 nm, while after irradiation at 350°C irradiation induced a 0 h1 0 0i{1 0 0} dislocation loops are clearly visible along with nanocavities. The dispersed yttria particles with an average size of 6-8 nm are found to be stable for all irradiation conditions. The density of the defects and the dispersoid are measured and found to be about 2.3 • 10 22 m À3 and 6.2 • 10 22 m À3 , respectively. The weak impact of irradiation on mechanical properties of ODS F/M steel is thus explained by a lower density of irradiation induced defects relative to the density of reinforcing particles.
Journal of Applied Crystallography, 2007
The microstructural effect of low-dose neutron irradiation and subsequent hightemperature tempering in the reduced activation ferritic/martensitic steel F82Hmod. (7.73 Cr, 0.09 C, 0.08 Mn, 0.19 V, 2.06 W, 0.02 Ta, wt%, bal. Fe) has been studied using small-angle neutron scattering (SANS). The investigated samples were irradiated with thermal neutrons at 523 K, to dose levels of 2.4 displacements per atom then tempered for 2 h at 1043 K. The SANS measurements were carried out at the D22 instrument of the High Flux Reactor at the Institut Max von Laue-Paul Langevin, Grenoble, France. The differences observed in nuclear and magnetic small-angle neutron scattering cross-sections after subtraction of the reference sample from the irradiated one suggest that the irradiation and the subsequent post-irradiation tempering produce the growth of non-magnetic precipitates; the results are also compared with those obtained on other ferritic/martensitic steels, with different chemical composition, irradiated under the same conditions.