Amorphous and Nanocrystalline Structure of Aluminium

Abstract is not availableJRC.F.4-Nuclear design safet

Mössbauer Spectrometry Applied to Soft Magnetic Alloys Influenced by External Factors

ABSTRACT A review of recent 57Fe Mössbauer Spectrometry (MS) studies of external influence on the properties of amorphous and nanocrystalline Fe-based alloys is presented in this paper. Two types of Fe-containing alloys (FeCuNbSiB and CoFeZrB) in the form of original amorphous and nanocrystalline ribbons were subjected to different external factors: high temperatures, different annealing atmosphere, mechanical and tensile stress. It will be shown that the Mössbauer Spectrometry is a suitable tool for such studies because the measured spectral parameters are very sensitive to the changes in the vicinity of the probe 57Fe-nuclei and thus, this technique provides a wide variety of information about structural and magnetic behaviour of Fe-containing materials. The most sensitive parameters were hyperfine magnetic field in crystalline component, average hyperfine field in amorphous component and direction of net magnetic moment. The considered external factors modified the amorphous as well as nanocrystalline structure, which was determined by MS phase analysis.JRC.F.4-Nuclear design safet

Model Steels with Parametric Variation of Ni, Mn, Si and Cr Content - Correlation between Magnetic Barkhausen Noise & Charpy Impact Test Results

In order to understand the role and influence of Ni, Mn, Si and Cr alloying elements and certain impurities on the mechanical properties of steels a large spectrum of ferritic steels with parametric variation of alloying elements as well as impurities content were prepared in the frame of the SAFELIFE Action of JRC-IE and the AMES Network. The composition of the 12 prepared model steels were inspired by typical base compositions of WWER-1000 and PWR base metal materials. In the present work the results of Magnetic Barkhausen Noise measurements are discussed and correlated with the results of Charpy impact tests.JRC.DG.F.4-Safety of future nuclear reactor

Model Steels with Parametric Variation of Ni, Mn, Si and Cr Content: Correlation between Magnetic Barkhausen Noise & Charpy Impact Tests Results

In order to understand the role and influence of Ni, Mn, Si and Cr alloying elements and certain impurities on the mechanical properties of steels a large spectrum of ferritic steels with parametric variation of alloying elements as well as impurities content were prepared in the frame of the SAFELIFE Action of JRC-IE and the AMES Network. The composition of the 12 prepared model steels were inspired by typical base compositions of WWER-1000 and PWR base metal materials. In the present work the results of Magnetic Barkhausen Noise measurements are discussed and correlated with the results of Charpy impact tests.JRC.F.4-Nuclear Reactor Integrity Assessment and Knowledge Managemen

Magnetic Barkhausen Technique Applied to the Characterization of As-Cast Model Steels with Parametric Variation of Ni, Mn, Si and Cr Content

The present work is aimed to investigate the capability and the optimisation of magnetic Barkhausen techniques to support the characterisation study of model steels. The task is within the frame of a project aimed to determine the role and influence of Cr, Ni, Mn and Si as alloying elements on the radiation stability of reactor pressure vessel steels. A large spectrum of ferritic steels with basic typical composition representative of WWER-1000 and PWR reactor pressure vessel materials were manufactured and different testing on miniaturised Charpy V-notch samples was performed. For the Magnetic Barkhausen Noise (MBN) measurements a sinusoidal exciting magnetic field with magnetising voltage of 10 Vpp was used, the applied magnetizing frequency being 10 Hz. The signal of the pick-up coil was processed by a 5 – 500 kHz band pass filter and the gain of amplification was set at 20. The root mean square values (RMS) of the noise signal were determined and were used to characterise the 12 model steels and to analyse the correlation with the available material's mechanical properties; ductile-to brittle transition temperature (DBTT) and hardness (HV10) values. The results are very promising and the next step will be to repeat the measurements after neutron irradiation of such model steels in the HFR-LYRA irradiation facility up to accumulated neutron fluence in the order of 1019 n.cm-2 and the further comparison of material properties before and after irradiation.JRC.F.4-Safety of future nuclear reactor

DESTRUCTIVE AND NON-DESTRUCTIVE TECHNIQUES APPLIED TO THE CHARACTERIZATION OF AS-CAST MODEL STEELS WITH PARAMETRIC VARIATION OF Ni, Mn, Si AND Cr CONTENT

The present work is aimed to investigate the role and influence of certain elements as Cr, Ni, Mn and Si on the radiation stability of reactor pressure vessel steels. The 12 ferritic steels with basic typical composition of WWER-1000 and PWR reactor pressure vessel materials were manufactured and submitted to Charpy impact, Barkausen Noise, Vickers hardness and SEM testing. Results of Charpy impact test show, that DBTT (ductile-to-brittle transition temperature) values are independent on the tested steels composition and are ranging between -150 and -104 C. Only two steels show extremely high DBTT (-16 and -42 C ); the mentioned steels contain low concentration of Ni and high concentration of Cr and vice versa. For those materials an additional heat treatment is designed in order to increase the DBTT values to values more near to those of the other steels. The results of MBN measurements show that the amount of Cr plays an important role: an increase of Cr content in model steels leads to an increase of RMS (root means square) values independently on Mn and Si contents. The percentage of Ni has also significant influence i.e. low Ni content is responsible for lower RMS values. By comparing the HV10, RMS and DBTT values of the 12 model steels it is not possible to find a general conclusion. However, most of the model steels combine high values of RMS with low values of DBTT. The next step will be the neutron irradiation of such model steels in the HFR-LYRA irradiation facility up to accumulated neutron fluence in the order of 1019 n.cm-2 and the further comparison of material properties before and after irradiation.JRC.F.4-Nuclear Reactor Integrity Assessment and Knowledge Managemen

(FeSm) - (FeAlPCBSiGa) Composites Prepared by Hot-Pressing of Ball Milled Powders

The present study was aimed to prepare a material which combines a high magnetostrictive strain in low magnetic fields with a high mechanical strength. Therefore we prepared composites which consist of soft magnetic Fe77Al2.4P8.64C5B4Si2.6Ga0.8 and high magnetostrictive (Fe2Sm) alloys. Ball milling of the amorphous FeAlPCBSiGa ribbon and a crystalline Fe2Sm ingot and subsequent hot pressing of the resulting powders were used to prepare disc shaped composites. A maximum magnetostrictive susceptibility of 930 ppm T-1 at a field of µ0H = 0.1 T was obtained. The hardness varied from 150 HV10 to 340 HV10 with increasing amount of the amorphous phase.JRC.F.4-Nuclear design safet

Characterisation of As-Cast Model Mn-Si-Cr-Ni Steels for Reactor Pressure Vessel Applications

Initial results are reported from a study aimed to investigate the role and influence of the elements Cr, Ni, Mn and Si on the radiation stability of reactor pressure vessel steels. Twelve as cast model ferritic steels with basic composition typical of those used in Russian WWER-1000 and Western PWR reactor pressure vessel materials were subjected to Charpy impact, magnetic Barkhausen noise (MBN), Vickers hardness tests and SEM examination. Higher Cr content in model steels was found generally to give increased RMS values independent of Mn and Si contents. The ductile¿ brittle transition temperatures (DBTT) and hardness values of the model steels were found to be independent of composition. Two steels, with low concentration of Ni and high concentration of Cr or vice versa, showed high transition temperatures (216 and 242oC respectively). An additional heat treatment to improve the properties is being considered for these compositions. The correlation between DBTT and MBN results has potential for rapid determination of the effect of composition and irradiation on the steel properties. The next stage of the assessment will investigate the effect of irradiation of the model steels to accumulated neutron fluences of ,10to19 cm22.JRC.F.4-Safety of future nuclear reactor

Model Materials for Reactor Pressure Vessel

In this paper we report preliminary results from a study focused on investigation of the role of elements as Cr, Ni, Mn and Si in the radiation stability of reactor pressure vessel steels. Twelve model ferritic steels and eight model welds with basic composition derived from Russian WWER-1000 and Western PWR reactor pressure vessel materials were studied by magnetic Barkhausen noise (BN) and Charpy-V impact measurements. Comparison of this two model materials led to the conclusion that the ductile-brittle transition temperatures and Barkhausen noise RMS values of model steels are shifted to the lower values as those of model welds. The WWER-1000 as reference point is shifted to lower RMS values in comparison with model steels and model welds. The next stage of the assessment will involve the investigation of the radiation effect on the model steels with accumulated neutron fluence of 1019 n/cm2.JRC.F.4-Safety of future nuclear reactor

NDT Study of Oxide Dispersion Strengthened Steels

Various oxide dispersion strengthened (ODS) steels (PM2000, MA956, ODM751 and ODS Eurofer) have been investigated using positron annihilation lifetime spectroscopy. Preliminary characterization of the vacancy type defects and the yttria nanoparticles are reported in this paper. The interpretation of the experimental data considers also the results of magnetic Barkhausen noise (BN) measurements as well as SEM and TEM investigations. Significant differences due to the presence of the yttria oxides (namely Y2O3) were observed in the studied materials in comparison to conventional ferritic/martensitic steels (e.g. Eurofer). Higher positron mean lifetime in ODS steels is, however, not only due to the presence of dispersoids, but also a result of vacancy agglomeration (clusters of 6-8 vacancies) which have been confirmed in recrystallised ODM751 and MA956 materials. On the other hand, positron trapping at dislocations was observed in the as-extruded ODS Eurofer in contrast to the other, recrystallised, materials where the high temperature treatment had led to the static recovery of these defects. It is suggested that some defects which are present (dislocations, vacancy clusters and dispersoids) and affect positron trapping in the materials are also important pinning sites for the magnetic domains. This is reflected by a shift of the signal peak in the BN spectra. The present complementary study provides more comprehensive information about materials microstructure and can support the interpretation of the physical/mechanical testing results (hardness, fracture mechanics etc.) obtained on these materials.JRC.DDG.F.4-Safety of future nuclear reactor