Deterioration Of Magnetic Properties Research Articles

Optimisation of the magnetic properties of soft-magnetic composites through an interfacial solid-phase reaction based on hot-pressing sintering and secondary-magnetic-phase addition

An effective method to improve the magnetic properties of soft-magnetic composites (SMCs) is insulation coating, which is achieved by inducing an interfacial solid-phase reaction via hot-pressing sintering. Herein, an interfacial solid-phase reaction was induced at the SMC interface through salt compound decomposition and the doping of carbonyl iron powder (CIP). Furthermore, FeSiAl-based SMCs with various CIP amounts were prepared. Results show that during hot-pressing sintering, calcium acetate coated on the FeSiAl matrix decomposes. Furthermore, the generated reactive oxygen species cause Si and Al migrations to the heterogeneous interface; in combination with the decomposition product CaO, these migrations result in the in situ formation of a CaSiO3·SiO2·Al2O3 composite insulation layer on the matrix surface. CIP added to the hydrothermal insulation coating exhibits good plasticity, and its combination with the coating layer improves the compressibility of composite powders and eliminates pores within SMCs. In hot-pressing sintering, CIP addition hinders the conversion of Si to SiO2, resulting in excess reactive oxygen species that react with Al in the FeSiAl matrix to yield a higher Al2O3 content. With an increase in the CIP amount, more Si diffuses into CIP such that the magnetic phase inside FeSiAl-based SMCs changes from a single Al0.3Fe3Si0.7 phase to a mixed phase comprising an Al0.3−xFe3Si0.7−y phase, CIP and CIP–Si. However, excessive CIP addition can cause the re-formation of pores inside SMCs and deterioration of magnetic properties. By changing CIP addition amounts, the magnetic properties of SMCs are precisely regulated. When the CIP addition amount is 9 wt%, the prepared SMCs exhibit optimal magnetic properties, with the highest saturation magnetisation of 134.5 emu/g and permeability of 44.1 at 10 mT and 500 kHz, along with a core loss as low as 198.8 kW/m3 at 20 mT and 100 kHz.

Microstructure evolution and strengthening mechanism of FeCo-1.5V0.5Nb0.4 W soft magnetic alloy rolled strip with high yield strength and low coercivity

The low strength of soft magnetic alloy limits the ability to operate high speed rotors in aero-generators. Strengthening of soft magnetic alloys remains a challenge, as most methods that enhance strength lead to the deterioration of magnetic properties. In this work, a rolled strip of FeCo-1.5V0.5Nb0.4W (wt.%) alloy with high yield strength and low coercivity was developed. We demonstrated that minor additions of Nb and W has a little effect on the magnetic properties. Due to the microalloying has a negligible effect on magnetocrystalline anisotropy, and low content of the secondary phase. Additionally, solute atoms are enriched at the grain boundaries, which reduces the grain boundary energy and promotes the nucleation and growth of Laves-Co2Nb phase at the grain boundary by grain boundary diffusion. These lead to almost stagnation of grain growth during isothermal annealing at 1123 K for 3 h and stabilization at ∼6 μm. Therefore, based on the reduction of dislocation density by high-temperature annealing to restore the magnetic properties of the alloy, fine-grain strengthening coupled with solid solution strengthening, and a certain amount of Orowan bypass effect and dislocation strengthening contribution, provide for the high strength of the alloy. The yield strength of the rolled strip reached 742 MPa under the conditions of no significant decrease in the saturation magnetization of 2.39 T and an extremely low coercivity of 152 A/m. These results are of great significance for understanding the relationship between the strengthening mechanisms of metallic materials and further developing high-performance FeCo-based soft magnetic alloys.

Influence of uniaxial tensile strain on magnetization behavior of Fe-9wt%Ni steel

This study investigated the effects of uniaxial tensile strain on the magnetization process of an Fe-9wt%Ni (9Ni) alloy to increase understanding of its magnetic behavior. As the applied strain was increased from 0 to 14 %, the magnetization curve changed remarkably, particularly under a high-intensity magnetic field, and magnetic flux density, relative permeability, remanence, and coercive force degraded significantly, especially at strains greater than the upper yield point. Increase in tensile strain caused increase in hysteresis losses, primarily because strain induced crystal defects, which affected the rearrangement of magnetic domains. Increased dislocation density was the primary contributor to the observed deterioration in magnetic properties; changes in texture and phase had little influence. This finding indicates that strain-induced deformation strongly affects the magnetic behavior of 9Ni alloys; this insight will be useful in research aimed at mitigating welding defects such as arc blow, that are attributed to the magnetization of Ni steel.

Thickness dependent magnetic anisotropy studies in sputtered Fe-Co-Al thin films

In this paper, an attempt has been made to evolve a structure-magnetic microstructure – magnetic property correlations in sputtered Fe-Co-Al thin films grown at different thicknesses. Fe-Co-Al thin films with various thicknesses viz., 25, 50, 100, 150 and 200 nm were deposited on Si 〈100〉 substrates at room temperature. Structural studies revealed that the films are crystalline in nature with bcc type structure. The crystallinity and average crystallite size deduced from X-ray diffraction studies were found to increase with increase in film thicknesses. Surface microscopy investigations also showed an increase in grain size with film thickness. All the films exhibited a predominant in-plane (IP) magnetic anisotropy. While the saturation magnetization was found to decrease with increase in film thickness, the coercivity exhibited an increasing trend. A maximum saturation magnetization of about 1300 emu/cc has been realized for the 50 nm thick film. Angular dependent magnetization studies indicated anisotropic magnetic behaviour along the plane of the film. Magnetic microscopy studies carried out using Longitudinal magneto-optical Kerr microscopy showed presence of 180° band domain along the easy direction of magnetization for lower thickness films. With subsequent increase in film thickness a combination of ripple and band domains were observed. With further increase in film thickness, presence of only ripple domains has been observed. The deterioration of IP magnetic properties with increase in film thickness was correlated with the magnetic microstructural observations.

Properties Optimization of Soft Magnetic Composites Based on the Amorphous Powders with Double Layer Inorganic Coating by Phosphating and Sodium Silicate Treatment

Core-shell structured amorphous FeSiBCr@phosphate/silica powders were prepared by phosphating and sodium silicate treatment. The soft magnetic composites (SMCs) were fabricated based on these powders. The effects of phosphoric acid (H3PO4) concentration and annealing temperature on their properties were investigated. During the phosphating process, the powder coated with a low concentration of H3PO4-ethanol solution leads to uneven phosphate coating, while the peeling of phosphate coating occurs for the high H3PO4 concentration. Using 0.5 wt.% phosphoric solution, a uniform and dense insulation layer can be formed on the surface of the powder, resulting in increased resistivity and the reduced eddy current loss of the amorphous soft magnetic composites (ASMCs). This insulation layer can increase the roughness of the powder surface, which is beneficial to the subsequent coating of sodium silicate. By optimizing sodium silicate treatment, a complete and uniform SiO2 layer can be formed on the phosphated powders well, leading to double layer core-shell structure and excellent soft magnetic properties. The magnetic properties of amorphous SMCs can be further improved by post annealing due to the effectively released residual stress. The enhanced permeability and greatly reduced core loss can be achieved by annealing at 773 K, but the deterioration of magnetic properties occurs as the annealing temperature over 798 K, mainly due to the increase of α-Fe(Si) and Fe3B phases, which hinder the domain wall displacement and magnetic moment rotation. The excellent soft magnetic properties with permeability μe = 35 and core loss Ps = 368 kW/m3 at 50 mT/200 kHz have been obtained when the SMCs prepared with the powders coated by 0.5 wt.% H3PO4 and 2 wt.% sodium silicate were annealed at 773 K.

Composition and property optimization of rare-earth-free Mn-Al-C magnet by phase stability and magnetic behavior analysis

Mn-Al-C system offers a possibility of rare-earth-free permanent magnets with the reduced temperature-dependent deterioration of magnetic properties. The Mn-Al-C alloy composition and magnetic properties have been optimized via calculations of electronic structures and phase stability of L 1 0 -ordered ferromagnetic τ-phase (Mn 0 . 5 Al 0 . 5 ) 100−x C x . The WIEN2k program package, Vienna Ab-initio simulation package (VASP), and Alloy Theoretic Automated Toolkit (ATAT) were used to calculate and identify the optimal carbon content for the most stable τ-phase of the L 1 0 -structured Mn-Al-C. We used the Brillouin function and Callen-Callen semiempirical relation to obtain the saturation magnetization and magnetocrystalline anisotropy constant at elevated temperatures. It was found that a carbon content of 2.33 at% gives the most stable τ-phase L 1 0 (Mn 0 . 5 Al 0 . 5 ) 100−x C x that has the lowest formation energy and highest saturation magnetization among the studied carbon contents (x = 0–3.03 at %). The magnetocrystalline anisotropy constant at 0 K increases with increasing the carbon content. Therefore, the carbon-doped Mn-Al becomes magnetically harder than the pure Mn 50 Al 50 . However, the anisotropy constant decreases at 300 K as the carbon content increases. The Curie temperature decreases to 590 K at x = 2.33 from 685 K at x = 0.0. The estimated saturation magnetization was approximately 130 emu/g at 300 K, leading to 18 MGOe under B s = B r and H ci > B r /2. Therefo r e, it is highly probable that Mn-Al-C potentially fills the gap between 10 and 30 MGOe magnets. The results in this study quantify and explain the reason for widely studying the approximately 2 at% carbon-doped Mn-Al systems. • A rare-earth-free, ferromagnetic L10 τ-phase (Mn0.5Al0.5)100-xCx was designed by first-principle calculations. • The calculated carbon content of 2.33 at% gives the lowest formation energy. • Theoretically optimized carbon content was in good agreement with experimental results. • The results explain the reason for widely studying the approximately 2 at% carbon-doped Mn-Al systems. • Rare-earth-free Mn-Al-C potentially fill the gap between 10 and 30 MGOe magnets.

Optimized microwave absorption properties of FeCoCrAlGdx high-entropy alloys by inhibiting nanograin coarsening

High-entropy alloys (HEAs) with nanoscale crystal structure have supposed to be good microwave absorbers due to their excellent soft magnetic properties. Annealing is typically employed to optimize microwave absorption, however, grain coarsening motivated by temperature will lead to serious deterioration of soft magnetic properties. Herein, we introduce the rare earth (RE) element Gd into FeCoCrAlGdx (x = 0, 0.1, 0.2, 0.3) HEAs, which is expecting to inhibit the nanograin coarsening through dispersing Gd2O3. The incorporation of Gd results in a low coercivity (Hc), high saturation magnetization (Ms), and high complex permeability (μ′ and μ″) of the HEAs. Especially, the Hc for as-annealed FeCoCrAlGd0.2 (114 Oe) is only 60.6 % of that for as-annealed FeCoCrAl (188 Oe). Owing to the remarkable magnetic properties, all Gd-doped HEAs have a larger effective absorption bandwidth at lower thicknesses. The reflection loss (RL) of as-annealed FeCoCrAlGd0.1 reaches a maximum absorption of −45 dB and an effective absorption bandwidth of 5 GHz (thickness is 1.5 mm). In addition, DFT (density functional theory) calculations are performed to analyze the energies and magnetic moments of the systems. This article provides guidance for design of high performance soft magnetic microwave absorbers.

Enhancing magnetic properties of the Co66Fe6Si13B15 metallic glass through DC annealing

Excellent soft magnetic properties of Co-based metallic glasses (MGs) can be achieved by appropriate annealing treatments. In this study, the Co66Fe6Si13B15 MG was annealed by direct current (DC) with densities ranging from 67 to 333 A/mm2 for varied periods of time. The magnetic properties of both the as-prepared and annealed samples were compared, which were further correlated with microstructure evolution. When the current density is lower than 167 A/mm2, themagnetization increases from 43 emu/g for the as-prepared state to over 60 emu/g for the annealed samples, and the coercivity sharply declined due to the stress release and structural relaxation caused by current annealing. Increasing current density leads to the formation of nanocrystalline particles of the size smaller than 5 nm, and the magnetic properties of the composite material further improve, which could be interpreted in terms of the random anisotropy model. The best soft magnetic performance with Ms of 72 emu/g and Hc of 4 Oe was obtained in the sample after annealed with a current density of 217 A/mm2 for 60 s. Larger grains result in the deterioration of magnetic properties once the current density exceeds 233 A/mm2. The results also imply that high-density but short-time current annealing can realize more efficient and precise treatment with respect to industrial application.

Influence of the cutting process, heat treatment, and maximum magnetic induction on the magnetic properties of highly oriented electrical steels

In this work, the dynamic losses of modern high-permeability grain-oriented (HGO) electrical steel were investigated as a function of the clearance used during the shear cutting process and the frequency of the applied magnetic field from 3 up to 1000 Hz. The strips were shear cut at clearances of 0.01, 0.04, 0.05, 0.10 and 0.15 mm, and after cutting the samples were heat treated at 850 °C for 1 h. The edge regions were analysed using optical microscopy before and after the heat treatment, and a significant mechanical deformation and consequently a deterioration of magnetic properties was observed, which can be restored through stress-relief annealing. Clearances of 0.01, 0.04, 0.05 and 0.10 mm exhibit the same total magnetic loss; however, for the clearance of 0.15 mm, it increases by ≈10% due to the crack in the fracture zone and greater rollover region. The heat treatment improves the magnetic performance of the as-cut HGO steel strips by ≈8% and ≈15% for 1.5 and 1.7 T, respectively, at frequency of 60 Hz. Finally, a detailed study of the dependence of the losses (hysteresis Ph, classical eddy current Pc, and excess Pe) on frequency and maximum induction was performed. Interestingly, it was observed that Ph is much more influenced by clearance than other losses. In addition, the role of the maximum induction Bmax on each loss component was investigated as a function of frequency. Our findings show that below 0.2 T Pc is larger than Pe and Ph, however, above this threshold there is an inversion where Pe is larger than the other two components in the entire frequency range, even with 1.5 T of magnetic induction. This can indicate that different physical mechanisms that constitute the permeability spectrum exhibit different relaxation times, therefore, they are activated at different frequencies and magnetic field intensities.

Simulation of the effect of segmented axial direction magnets on the efficiency of in-wheel permanent magnet brushless DC motors used in light electric vehicles based on finite element method

Energy efficiency is primary target for electric motor designers. The Eddy current losses can cause deterioration of permanent magnet machines magnetic properties and increase rotor temperature. Therefore the rotor eddy current loses can decrease efficiency of permanent magnet brushless DC (PM BLDC) motors. Permanent magnets when designed with axial segmentation help reduce the eddy current losses. This paper presents an investigative study on calculating eddy current losses of in-wheel permanent magnet brushless direct current motors and the effect of segmented axial direction magnets on the efficiency of these motors used in light electric vehicle. In this study in-wheel PM BLDC motor has been designed and analyzed on with slot/pole combinations 24/20, 36/30, and 42/36, that the motor is rated power of 4 kW at rated speed of 1500 rpm. Finite Element Method (FEM) is used to carry out numerical analysis for an accurate result. The magnet losses and efficiency are calculated for segmented magnets with different quantity of magnets in the axial direction. Changing the number of axial magnet segment from 1 to 20 causes approximately 1% increase in the efficiency. Following the change in number of axial magnet segment, the shaft power values increment is about 40 W, while shaft torque is between 0.25 and 0.30%.

Magnetic properties measurement and analysis of electrical steel sheet under cutting influence

The cutting process of silicon steels is a necessary manufacturing technique in electrical equipment. Different cutting methods have different effects on the internal structure and magnetic properties of the electrical steel sheets. Laser cutting can produce thermal stress during processing, while mechanical cutting may cause plastic deformation near the cutting edge, which both lead to deterioration in the magnetic properties of the material. Therefore, studying the effect of different cutting techniques on magnetic properties is of great significance to accurately predict the iron losses of electrical equipment. In this paper, a mobile B-H sensing structure is designed to sense the distribution of local magnetic properties near the cutting edges. Magnetic properties of the non-oriented (NO) silicon steel samples B35A270 and 50JN470 are measured and characterized with the variation of distance from cutting edges. The results demonstrate that the deterioration of magnetic properties depends on the cutting methods and the material characteristics. Wire cutting has little effect on magnetic performance and the effect can be observed near the cutting edge. As a contrast, the decrease of the relative magnetic permeability can be observed in a deeper width of the steel strips cutting by laser. Moreover, the multiple trends of laser cutting loss which vary with cutting depth are compared and discussed. This research can provide a reference for the application of electrical equipment under actual working conditions.

Influence of annealing temperature on degradation efficiency and iron oxide transformations in CeO2/Fe-oxide sorbents

The microstructural and physical properties of magnetically separable CeO2 (5 wt.%)/Fe-oxide sorbents, applicable for the decomposition of organophosphorus pesticides, are analyzed in dependence on calcination temperature. The sorbents are prepared using a two-step procedure: (1) synthesis of magnetite core from cheap and commercially available raw materials; and (2) the formation of cerium (III) carbonate by precipitation with the ammonium hydrogen carbonate, containing re-dispersed magnetite. The cerous carbonate/magnetite precursor is annealed in a muffle furnace at temperatures ranging from 473 to 1073 K for 2 h to obtain the CeO2/Fe-oxide reactive sorbents. Structural characterization of the samples is performed using X-ray diffraction, scanning electron microscopy, Raman and Fourier transform infrared spectroscopy. Magnetic properties are obtained from hysteresis loops, field-cooled and zero-field-cooled curves, first-order reversal curve (FORC) diagrams, and Henkel plots. Sorbents exhibit an increase in coercivity from 0.2 kA/m to about 20 kA/m and a decrease in saturation magnetization from roughly 50 Am2/kg to 1 Am2/kg after annealing at 973 K. This deterioration of magnetic properties is caused by the transformation of magnetite and maghemite into weakly ferromagnetic hematite, with a typical peak in FORC diagram and a Morin transition at about 200 K. The degradation efficiency towards parathion and paraoxon methyl is about 30% for samples annealed from 473 K to 773 K.

Multiparameter Modeling and Analysis of Mechanical Cutting Process of Grain-Oriented Silicon Steel

The process of mechanical cutting of magnetic materials has many advantages in the form of high efficiency, no generation of thermal stresses or the possibility of shaping materials taking into account long cutting lines. In the literature, there are models that allow to control the technological quality of the mechanical cutting process, e.g. in terms of the obtained quality of the cut surface. However, there is a lack of data on the selection of technological parameters of the mechanical cutting process of grain-oriented silicon electrical sheets in terms of the obtained quality of the cut surface and the obtained magnetic properties of the workpiece. The paper presents a solution to the gradient optimization problem combining issues from the field of structural and magnetic analyzes. Using obtained relationships and results, it is possible to control cutting process to obtain high cut surface quality with minimum deterioration of magnetic properties.

Evolution of {0kl} 〈1 0 0〉 texture and microstructure in preparation of ultra-thin grain-oriented silicon steel

In this paper, an ultra-thin grain-oriented silicon steel (UTGO steel) strip was prepared via rolling a commercial glassless grain-oriented silicon steel plate to 0.075 mm and then annealing it at 850 °C for less than 30 min in a protective atmosphere. The resultant UTGO steel strip has magnetic induction B800 higher than 1.80 T and iron loss P1.5/400 lower than 12.0 W/kg. These superior magnetic properties are due to predominant {0kl} 〈1 0 0〉 texture and appropriate microstructure. The study shows that preferential {0kl} 〈1 0 0〉 nucleation occurs either inside shear bands or at in-grain deformation-induced boundaries. The nucleation behavior varies at different nucleation sites. Nuclei inside shear bands are denser and show preferential transitional orientation along {0kl} 〈1 0 0〉, while new grains dispersed at in-grain split boundaries have shown orientations which are suggested to inherit corresponding initial grain orientation prior to rolling. Nucleation behavior is also highly dependent on the orientation of the roll-deformed matrix. Our study finds that shear banding nucleation of {0kl} 〈1 0 0〉 (including Goss and {0 2 1} 〈1 0 0〉) is reduced when the orientation of the deformed matrix deviates from {1 1 1} 〈1 1 2〉. With the extension of annealing time, the growth of {0kl} 〈1 0 0〉 nuclei in cluster is restricted because of orientation pinning effect, whereas the growth of grains with orientations other than {0kl} 〈1 0 0〉 is promoted. This phenomenon weakens the dominance of {0kl} 〈1 0 0〉 texture, causing deterioration in magnetic properties of the final silicon steel.

Effect of Nb content on primary recrystallization microstructure, texture and magnetic properties of grain-oriented silicon steel manufactured by low-temperature slab reheating

The influence of Nb content on the primary recrystallization microstructure, crystallographic texture and magnetic properties of grain-oriented silicon steel manufactured by low-temperature slab reheating were studied. The results show that the effect of grain refining was enhanced with the increase of Nb content. With the increase of Nb content, the total contents of texture {111}〈112〉 and {114}〈481〉 in primary recrystallization which are beneficial to the secondary recrystallization increased, but the contents of deviated Goss component and adverse textures with abnormal growth ability in primary recrystallization also increased, which led to the deterioration of magnetic properties. By adding 0.005% Nb, the average size of the primary grain reduced to 23 μm, the content of {110}〈112〉 increased slightly and the least deviated Goss nuclei were obtained, therefore the final product had the sharpest {110}〈001〉 texture of secondary recrystallization and the best magnetic properties with B800 = 1.873 T , P1.7/50 = 1.21 W/kg.

Influence of shear-slitting parameters on workpiece formation, cut edge quality and selected magnetic properties for grain-oriented silicon steel

The traditional process of mechanical cutting of electrotechnical steels, still have many advantages such as: high efficiency, no thermal deformation zone affected by hot ablation, the possibility of shaping products of any length of the cutting line. However, this process introduces a substantial plastic deformation to the sheet metal and causes premature edge fracture during the subsequent forming process. This causes the deterioration of the magnetic properties of material. The paper studies the effects of the technological parameters of shear- slitting process on residual stresses and strains, quality of sheared edge and selected magnetic properties based on ET 122-30 grain oriented electrical steel. For the study, a simulation model ofthe process using mesh-free method (SPH) is developed. To obtain knowledge of the influence of this parameters on quality of cut surface and magnetic properties of material, experimental research was done using vision-based measurement system, confocal and atomic force microscopes and system for testing soft magnetic materials. Finally, an example of graphical optimization is presented and set of acceptable solutions is developed on the plane of controllable variables. Using obtained relationships and results, it is possible to control cutting process to obtain high cut surface quality with minimum deterioration of magnetic properties.

Pulsed laser welding of laminated electrical steels

Abstract Stator core is one of the parts in the magnetic circuit, which playing an important role in the performance of the electric machine. Commonly the non-oriented electrical steel laminations are assembled into a stator stack by welding to meet the demand of strength at high-speed rotation. However, the effects of residual stress, microstructure change and inter-conduction among laminations introduced during welding process result in a great deterioration in magnetic properties of stator core. The pulsed laser welding of ultra-thin electrical steel laminations is adopted to decrease the iron loss while ensuring sufficient strength simultaneously. As two important indicators of the stator core, peak load after welding determines the maximum load torque and iron loss affects the energy conversion efficiency. There is currently no model that can accurately predict peak load and iron loss of the stator core after pulsed laser welding, and the influence of peak power and duty cycle on peak load and iron loss also needs to be further studied. In this paper, the peak load of stator core is studied based on the tensile test of a novel rectangular specimen which has the same stress state with the ring ones subjected to torsional load. An empirical model of peak load is proposed by the two-step fitting method considering the effect of peak power and duty cycle. Then an analytical model of iron loss of welded laminations is developed considering eddy current circuit in weld seam caused by damage of insulation coating. All peak load and iron loss models with small relative errors can obtain accurate prediction results. Finally, the weld lobe for pulsed laser welding is drawn, whose left and right boundaries are determined by peak load and iron loss, respectively. By selecting the appropriate process parameters, iron loss of the stator core using pulsed laser welding decreases, compared with traditional continuous laser welding.

Effect of Ni and Mo contents on microstructure, magnetic and mechanical properties of Ti(C, N)-based cermets

Ti(C,N)-based cermets were prepared by vacuum sintering. The effect of Ni and Mo contents on microstructure, magnetic and mechanical properties of cermets were investigated using XRD, SEM, EDS, and VSM. The results showed that the proportion of ceramic hard phase decreased gradually, and the core-rim structure became incomplete with Ni content. However, with an increase in Mo content from 6 to 18 wt. %, the thickness of rim phase slightly increased. The complete core-rim structure refined the grain size of cermets, and the particles became the finest when Mo content was about 14 wt. %. The magnetization of cermets increased with Ni content, while their magnetization gradually weakened with Mo content. The deterioration of magnetic properties was caused by the high total content of Mo and Ti alloying elements in the binder phase. Meanwhile, the hardness of cermets decreased, while the TRS initially increased, followed by a gradual decrease with content of Ni. With an increase in Mo content, the hardness and TRS of Ti(C,N)-based cermets increased firstly and then decreased. The fracture toughness of cermets increased with Ni content, while the increasing Mo content reduced the fracture toughness. Due to grain refinement and solid-solution strengthening of the binder phase, the optimal composition of cermet was Ti(C,N)-14Mo-25Ni, whose hardness, TRS, and Kic values were ~90.3 HRA, 2340 MPa and 11.7 MPa·m1/2, respectively.

Effect of blanking on magnetic and mechanical properties of non-oriented electrical steel

World-wide blanking is the most popular technique for producing the non-oriented electrical steel lamination. However, blanking has a great effect on magnetic property and mechanical property, such as the introduction of uneven residual stress, the deterioration of magnetic properties and the increase of micro-hardness. In this research, non-oriented electrical steel sheets are investigated via blanking test by 3 kinds of punches. The blanking edges are examined by the optical microscopy and micro-hardness test to visualize the distribution of micro-hardness. The magnetic properties are also measured. The results show that the blanking clearance has a great influence on magnetic properties and mechanical properties of the blanked material.

Suppression of α-Fe₂O₃ Phase in MgFe₂O₄ Nanoparticles with High Magnetization by Controlling Annealing Process

We report the phase stability, microstructure and magnetic properties of MgFe2O4 nanoparticles under different annealing conditions. Magnetic properties of MgFe2O4 are strongly influenced by the crystal structure and morphology, which in turn, depend on annealing conditions. The as-prepared and samples annealed at 1200 °C show a pure spinel phase. Whereas the samples annealed and quenched at 600 °C-1000 °C exhibit the spinel phase along with a small fraction of the secondary phase of α-Fe₂O₃, which causes deterioration of magnetic properties. On the other hand, samples annealed at 600 °C-1000 °C under Argon atmosphere display superior magnetic properties (M = 44-56 emu/g at room temperature) due to the presence of pure spinel phase. Interestingly, the sample quenched at 1200 °C exhibits large saturation magnetization, MS = 63 emu/g at 5 K which is arising from the optimum cationic distribution (δ = 0.77) grown at elevated temperature is retained in the rapid cooling process.