Study and suppression of the microstructural anisotropy generated during the consolidation of a carbonyl iron powder by field-assisted hot pressing

Published OnlineA spherical carbonyl iron powder was consolidated by the field-assisted hot pressing technique using graphite tools at two different temperatures, both above the austenitizing temperature. The microstructures obtained exhibited a compositional gradient in carbon along the consolidated material. Thus, the outer rim of the cylindrical samples was composed of cementite and pearlite that gradually turned to pearlite, leading to a fully ferritic microstructure at the core of the sample. The increase in the temperature has led to a higher introduction of carbon within the sample. The interposition of a thin tungsten foil between the graphite die/punches and the powders has significantly reduced the diffusion of the carbon through the iron matrix and has suppressed the microstructural anisotropy.Publicad

Advances in Powder Metallurgy Soft Magnetic Composite Materials

Powder metallurgy has grown with the expansion of various industry. Automotive industry had the most strong influence. Today, more than 90% of PM products are used in the transportation industry. Development of new materials such as magnetic materials is expected to meet the new trends of automotive industry, electric and hybrid vehicles. Soft magnetic composites (SMC) are PM materials based on ferromagnetic powder particles covered by electric insulation layer. Concept of SMC’s and PM technologies offer possibility to become faster, use higher frequencies, become smaller and denser, save more energy, achieving high permeability and lower core loss in high frequency region, which is required for soft magnetic materials. Investigation of correlations among compaction parameters, inner structure, magnetic and mechanical properties are presented

AC Magnetic Properties of Vitroperm Based Composite Materials

The aim of this work was to investigate the influence of resin content on AC magnetic properties of Vitroperm 800-based composite material to extend possibilities for application of this kind of material at higher frequency (up to 100 kHz). The samples of composite material were prepared in the form of the ring with outer diameter of 25 mm, inner diameter of 18 mm and height approximately 3 mm. Powder mixtures were prepared from Vitroperm 800 in partial nanocrystalline state and commercial termoset resins by mechanical mixing. The AC magnetic properties (losses) at maximum induction up to 0.5 T were measured by MATS-2010SA loop tracer in frequency range 1-100 kHz. The specific resistivity of the material was measured by the van der Pauw method. The magnetic properties of the composite rings were compared with the properties of the material prepared from Fe based powder supported by Höganäs. It was found out that the total losses of the Vitroperm-based soft magnetic composite are more than 10 times lower (at 10 kHz) than that for Fe-based one

Magnetic Properties of Soft Magnetic FeSi Composite Powder Cores

Soft magnetic composites (SMCs), which are used in electromagnetic applications, can be described as ferromagnetic powder particles surrounded by an electrical insulating film. These composite materials offer several advantages over traditional laminated steel cores such as reduction in weight and size. They have some unique properties, including three-dimensional isotropic ferromagnetic behaviour, very low eddy current loss, relatively low total core loss at medium and high frequencies, high electrical resistivity and good relative magnetic permeability. FeSi powder was used as a base ferromagnetic material for preparation of soft magnetic composites. The commercial FeSi particles of a precise spherical shape were prepared in two granulometric fractions (up to 150 μm or up to 356 μm). The phenol-formaldehyde resin modified by $SiO_{2}$ nanoparticles was used as an electroinsulating layer. The FeSi particles covered by the synthesized resin were compacted at 800 MPa into the ring samples for magnetic measurements. The final samples were treated thermally under the curing schedule, which was suggested according to thermal degradation of the modified resin

Influence of Vitroperm Content on the Energy Losses in Composite Materials Based on the Mixture of Two Ferromagnets

Soft magnetic composites offer several advantages such as 3D isotropic magnetic properties and relatively small energy losses, finding use in electrical devices like electromotors, transformers or sensors. The aim of this work was to investigate the dc and ac magnetic properties of composites based on the mixture of two different ferromagnets: iron based material Somaloy® 700 and Vitroperm® 500 alloy. The analysis of total losses into dc losses, classical losses and excess losses showed that the classical and excess losses were negligibly small. The specific resistivity was increasing with the increasing fraction of Vitroperm (VPM). The coercivity exhibited maximum at 20% of VPM

Investigation of Magnetization Processes from the Energy Losses in Soft Magnetic Composite Materials

Soft magnetic composite materials are composed of small ferromagnetic particles insulated from each other. It gives them some very good properties e.g. the magnetic isotropy and low total energy losses at medium to higher frequencies. On the other hand, their structure gives rise to the negative aspects as the inner demagnetizing fields, resulting in some specifics in magnetization processes leading to the worsening of soft magnetic properties, particularly the excess losses increase and a lowering of permeability. The frequency dependence of excess losses, the low and high induction loss components and the inner demagnetization factors of soft magnetic composites were investigated in order to reveal the proportions of the reversible and irreversible magnetization processes. Higher excess losses were observed in samples with smaller particles or higher non-ferromagnetic content (resin+pores), in which the inner demagnetizing fields were higher. It was explained by lower effective number of movable domain walls in those samples, thus less irreversible magnetization processes. This was confirmed by low and high induction loss analysis, where total losses were divided into low and high induction loss components and plotted vs. frequency

AC Magnetic Properties of Vitroperm Based Composite Materials

The aim of this work was to investigate the influence of resin content on AC magnetic properties of Vitroperm 800-based composite material to extend possibilities for application of this kind of material at higher frequency (up to 100 kHz). The samples of composite material were prepared in the form of the ring with outer diameter of 25 mm, inner diameter of 18 mm and height approximately 3 mm. Powder mixtures were prepared from Vitroperm 800 in partial nanocrystalline state and commercial termoset resins by mechanical mixing. The AC magnetic properties (losses) at maximum induction up to 0.5 T were measured by MATS-2010SA loop tracer in frequency range 1-100 kHz. The specific resistivity of the material was measured by the van der Pauw method. The magnetic properties of the composite rings were compared with the properties of the material prepared from Fe based powder supported by Höganäs. It was found out that the total losses of the Vitroperm-based soft magnetic composite are more than 10 times lower (at 10 kHz) than that for Fe-based one

Structure and Properties of Composites Based on Mixed Morphology of Ferromagnetic Particles

Application potential of the soft magnetic composites increases with improvement of their functional properties. In addition to the magnetic properties, the mechanical properties of these materials are essential. The aim of this work was to investigate mechanical properties and their dependence on morphology of the ferromagnetic particles. Model composite based on Somaloy® and Vitroperm® powder was prepared using conventional powder metallurgy. The DC magnetic properties of composites based on two types of ferromagnetic particles with different shapes and structures are discussed in the relation with mechanical properties

Influence of Vitrovac Content on Magnetic Properties in Composite Materials Based on the Mixture of Two Ferromagnets

Soft magnetic composite materials play an important role in nowadays industry, replacing the traditional materials such as electrical steels and soft ferrites, especially at medium and higher frequency applications. The material can be tailored for a specific application by changing the composition of the material and by adaptation of the fabrication process. The aim of this work was to investigate the morphology, phase composition and magnetic properties of soft magnetic composite materials with various magnetic content to minimize the total magnetic losses. The prepared sample series was based on the mixture of two different ferromagnets Vitrovac 6155 and Somaloy 700 without addition of insulating material. The samples were prepared by conventional powder metallurgy with particular fraction of Vitrovac in the form of a ring for magnetic measurements in AC fields and electric resistivity measurements. The samples with 5 wt% and 20 wt% fractions of Vitrovac exhibit lower values of total losses in comparison with Somaloy heat treated at 530°C

Wide Frequency Range AC Magnetic Properties of Fe-Based Composite Materials

The aim of this work was to analyze the influence of resin content on contribution of the hysteresis, eddy current and anomalous losses to the total losses in the frequency range from DC to 150 kHz. The samples of composite material were prepared in the form of the ring with outer diameter of 25 mm, inner diameter of 17 mm and height approximately 3 mm and in the form of cylinder with diameter of 25 mm and height approximately 3 mm by a compaction of mixture of iron powder ASC100.29 (90 vol.%) and commercial termoset resins. The DC hysteresis losses were obtained by the measurements of DC hysteresis loops and the total power losses in the frequency range 0.4 Hz-150 kHz from AC hysteresis loops, both at maximum induction 0.05, 0.1 and 0.2 T. The magnetic properties of the composite rings were compared with the properties of the material prepared from the powder supported by Höganäs AB Sweden. By analyzing the frequency dependence of total losses of the Fe-based SMC we found out that hysteresis losses contribute to the total losses as a majority component