Incorporation of Y2O3 Particles into 410L Stainless Steel by a Powder Metallurgy Route

Addition of yttria to steels has been proposed for the fabrication of oxide-dispersion-strengthened materials for nuclear power applications. We have investigated materials prepared from 12 Cr martensitic stainless steel, AISI 410L, produced by powder metallurgy. Materials were produced with and without yttria addition, and two different sizes of yttria were used, 0.9 µm and 50 nm. Tensile and mini-creep tests were performed to determine mechanical properties. Optical microscopy, SEM, TEM, and EDX analysis were used to investigate the microstructures and deformation mechanisms and to obtain information about non-metallic inclusion particles. SiO2, MnS, and Y2Si2O7 inclusion particles were observed. An SiO2 and Y2O3 interaction was seen to have occurred during the ball milling, which impaired the final mechanical properties. Small-angle neutron scattering experiments showed that the matrix chemistry prevented effective dissolution of the yttria. © The Author(s) 201

Imaging of Magnetic Domains and Domain Walls in Spherical Fe-Si Powder Using Magnetic Force Microscopy

The commercial Fe-Si powder, produced by Högänes Corporation, represents promising soft magnetic material for technological applications. The powder consists of spherical particles with diameter up to 150 μm. Internal microstructure of the powder is formed by grains of diameter of about 30 μm. Each separate grain has a random orientation of the easy magnetization axis and is sufficiently large to split into several magnetic domains. A comparative study of the atomic force microscopy (AFM) topography and the corresponding magnetic force microscopy (MFM) images was employed in order to examine the correlation between the grain size, boundaries of grains and characterization of the magnetic domains, which gives us an important knowledge about possible behavior of particles under the influence of the external magnetic field and further utilization of the spherical Fe-Si particles in electrotechnical industry. The grain size and the crystallographic orientation of grains were analyzed by the electron backscattering diffraction (EBSD) technique

FeSiBAlNiMo High Entropy Alloy Prepared by Mechanical Alloying

High-entropy alloys have attracted increasing attentions because of their unique compositions, microstructures, and adjustable mechanical and functional properties. In this work, mechanical and magnetic properties of the FeSiBAlNiMo high-entropy alloy were studied in heat-treated conditions. Influence of temperature and time of sintering was investigated. The lowest coercivity H_c=370 A/m was reached at sintering temperature 580°C, during 20 min in Ar/10H₂ atmosphere. Resistivity decreases from R=0.006 Ωcm at 580°C of sintering temperature to R=0.0004 Ωcm at temperature 1100°C. Transverse rupture strength TRS = 340 MPa as well as the Young modulus E=87 GPa were much higher in the case of sintering at 1100°C in comparison to TRS = 5 MPa and E=7.5 GPa at sintering temperature 580°C. Low temperature consolidation made possible to structure recovery and stress relief of amorphous-nanocrystalline structure. Higher temperature above 1100°C induced sintering processes and formation of complex borides

FeSiBAlNiMo High Entropy Alloy Prepared by Mechanical Alloying

High-entropy alloys have attracted increasing attentions because of their unique compositions, microstructures, and adjustable mechanical and functional properties. In this work, mechanical and magnetic properties of the FeSiBAlNiMo high-entropy alloy were studied in heat-treated conditions. Influence of temperature and time of sintering was investigated. The lowest coercivity H_c=370 A/m was reached at sintering temperature 580°C, during 20 min in Ar/10H₂ atmosphere. Resistivity decreases from R=0.006 Ωcm at 580°C of sintering temperature to R=0.0004 Ωcm at temperature 1100°C. Transverse rupture strength TRS = 340 MPa as well as the Young modulus E=87 GPa were much higher in the case of sintering at 1100°C in comparison to TRS = 5 MPa and E=7.5 GPa at sintering temperature 580°C. Low temperature consolidation made possible to structure recovery and stress relief of amorphous-nanocrystalline structure. Higher temperature above 1100°C induced sintering processes and formation of complex borides

The influence of NiZnFe₂O₄ content on magnetic properties of supermalloy type material

Soft magnetic composites represent a remarkable kind of materials with wide variety of use. Magnetic properties are dependent on the materials composition and also on the method of preparation. Ni-Fe-Mo alloys (supermalloy) have high complex permeability and low eddy current losses. Soft magnetic NiZnFe₂O₄ ferrites have low coercivity and intermediate saturation magnetization. The Ni_{80}Fe_{14.7}Mo_{4.5}Mn_{0.5}Si_{0.3} (wt%) powder sample was prepared by mechanical alloying of the chemical elements for 24 h. Ni_{0.3}Zn_{0.7}Fe₂O₄ ferrite is commercially available by Sigma Aldrich. Both powders were mixed at selected ratio and uniaxially compacted at 800 MPa. In this paper, we report the experimental observations of the effects of Ni_{0.3}Zn_{0.7}Fe₂O₄ content on the electromagnetic properties of NiFeMoMnSi/Ni_{0.3}Zn_{0.7}Fe₂O₄. The samples contained 5, 10, and 15% of Ni_{0.3}Zn_{0.7}Fe₂O₄ ferrite and were sintered for 30 min at 800°C. An addition of Ni_{0.3}Zn_{0.7}Fe₂O₄ ferrite caused decrease of complex permeability and increase coercivity of the samples. The 5% of Ni_{0.3}Zn_{0.7}Fe₂O₄ sample exhibits the highest value of the real part of complex permeability (48 at 1 kHz). The 10% of Ni_{0.3}Zn_{0.7}Fe₂O₄ sample showed the lowest total magnetic losses

Novel layered architecture based on Al

The paper is focused on a very hot topic of SMART materials and their architectures for energy conversion systems designed for conversion of mechanical to electrical energy using the piezoelectric effect. The aim of the study is to increase both the reliability and efficiency of electromechanical conversion compared to standard concepts. Our new design of piezoelectric cantilever is made with multi-layer ceramic composite, where piezoelectric layer BaTiO3 is covered by protective ceramics layers of different residual stresses, where Al2O3 and ZrO2 is used. Utilization of controlled residual stresses into new multi-layer architecture is the key idea and it is crucial for optimal design of the individual layers of the proposed concept. The multi-layer ceramic composite is fabricated by electrophoretic deposition, where the composite is assembled from different ceramic materials during processing and after sintering we get inseparable ceramic laminate consisting of piezoelectric and protective layers of ceramics. This approach of processing multi-layer ceramic material including lead free piezoelectric layers is innovative and has never been published before

Radiation damage evolution in High Entropy Alloys (HEAs) caused by 3–5 MeV Au and 5 MeV Cu ions in a broad range of dpa in connection to mechanical properties and internal morphology

High Entropy Alloys (HEAs) are prospective materials for nuclear fusion reactors and were irradiated in this study at a broad range of energetic ion fluences. Different ion masses (Cu and Au ions) and energies (3 and 5 MeV) were selected to investigate dpa (displacement per atom) development, radiation defect accumulation based on prevailing collision processes (Au ions) and ionization processes (Cu ions) in various HEAs. The studied HEAs differ in terms of elemental composition, internal morphology (grain structure) and other modifiers. Dpa values of 1 to ∼66 were achieved at Cu and Au ion fluences from 4 × 1014 to 1.3 × 1016 ions.cm−2 at room temperature, which generated varying levels of lattice damage. Theoretical simulations were performed to estimate the energy stopping and dpa depth distribution using SRIM code and compared with Au-concentration depth profiles determined by Rutherford backscattering spectrometry for Au-ions with 3 MeV ion energy. The prevailing energy losses of ions via ionization processes for Cu-5 MeV ions were found to increase the damage through lattice strain and probable lattice distortion, although the main defect introduction is expected to occur via collisions during nuclear stopping. Structural modification and defect accumulation were investigated by positron annihilation spectroscopy (PAS), which revealed a broader damaged layer with defects, where HEA-Nb (NbCrFeMnNi) exhibited the least damage accumulation from chosen alloys with no strong relation to the Au-5 MeV ion implantation fluence, whereas strong defect accumulation was recorded in the Au-ion implanted Eurofer97 used for comparison and HEA-Co (CoCrFeMnNi). PAS analysis also allowed defect sizes to be determined as an additional structural characteristic. The observed trends were also confirmed by thermal property analysis, with a worsening of thermal effusivity recorded after the irradiation in HEA-Co and Eurofer97. The worsening of the thermal properties was confirmed by the layer thickness, where the layer identified by PAS was found to be broader than the SRIM theoretical predictions. Nanoindentation measurements confirmed less pronounced radiation hardening of HEA-Nb relative to that observed in HEA-Co and Eurofer97. Transmission Electron Microscopy (TEM) analysis revealed layer thicknesses in reasonable agreement with the dpa depth profiles. The thermal effusivity decreased in the surface-irradiated layer in all investigated samples, the least influenced material was HEA-Nb