The effects of pre-annealing treatments on the soft magnetic properties of the corresponding Fe78Si9B13 amorphous powder cores were investigated. The amorphous powder cores prepared from pre-annealed powder have better soft magnetic properties compared with unpretreated powder core in the as-cast state. The result shows that the powder after pre-annealing in a magnetic field presents a regular domain structure and the soft magnetic properties of the corresponding powder cores are greatly improved. As the result, the magnetic-field annealed powder core has the highest effective permeability (μe) of 37, which is 23 % higher than the as-cast one and 7 % than only vacuum-annealed one. The total core loss (Pcv) for the core annealed in magnetic field is only 141 W/kg (100 kHz, 50 mT) and as low as 36 % of the Pcv for the powder core in the as-cast state. The one annealed in magnetic field also exhibits the best DC bias properties of 92 %. This work provides a novel approach to realizing low Pcv and high μe for Fe78Si9B13 powder cores and also validates the application prospect of powder cores in the work condition of different ripple currents, different loads and a wide frequency (f) range (10 kHz–10 MHz).

•Fe-based amorphous powder cores were annealed in transverse magnetic field of 0.5 T.•The cores shown an enhanced and stable effective permeability of 90 up to 2 MHz.•The core loss of the core decreased from 260 to 235 W/kg at 100 kHz and 0.1 T.The effects of transverse magnetic field annealing on the magnetic properties of Fe78Si9B13 amorphous powder cores were investigated. The cores annealed at 400 °C under an external transverse magnetic field of 0.5 T show an enhanced and stable effective permeability of 90 in the high frequency range up to 2 MHz. Meanwhile, the permeability was improved by about 5% and the core loss was decreased by about 10% compared to the core with zero field annealing, which is attributed to the relief of internal stress and the variation of domain structure. It also shows superior DC bias property with a “percent permeability” of 70% at an external field of 100 Oe. Transverse magnetic field annealing is an effective way to improve the soft magnetic properties of the amorphous powder cores. The improvement of soft magnetic properties of the Fe-based amorphous powder cores is encouraging for future applications as functional materials.Download high-res image (125KB)Download full-size image

Corrosion resistance and passivation behavior of Fe63Cr8Mo3.5Ni5P10B4C4Si2.5 amorphous coatings prepared by the activated combustion high-velocity air fuel (AC-HVAF) and high-velocity oxygen fuel (HVOF) processes have been studied in detail by cyclic potentiodynamic polarization, electrochemical impedance spectroscopy, cathodic polarization and Mott–Schottky approach. The AC-HVAF coating shows higher corrosion resistance than the HVOF coating in 3.5 wt.% NaCl solution, as evidenced by its lower corrosion current density and passive current density. It is found that the superior corrosion resistance of the AC-HVAF coating is attributed to the enhanced formation of a dense passive film with less defective structure, higher pitting resistance and passivity stability, as well as stronger repassivity.

•Mo addition improves formation of an amorphous phase in low vacuum atmosphere.•Mo containing alloys have better frequency properties than Mo free alloy.•Decreasing wheel speed can widen annealing temperature range for Mo-free ribbons.•All alloys exhibit a similar excellent soft-magnetic properties after annealing.Fe82Cu1Si4B11.5Nb1.5−xMox (x = 0, 0.75 and 1.5 at. %) nanocrystalline alloys were prepared using a melt-spinning technique and the effects of Mo content on thermal stability, soft magnetic properties and microstructure evolution were investigated. It was found that the Mo addition can improve the amorphous-forming ability and inhibit surface crystallization in a low vacuum atmosphere which may be due to better oxidative resistance. All the alloys exhibited excellent soft-magnetic properties with low coercivity of 8.9–10.8 A/m, high effective permeability of 11,500–11,900 at 1 kHz and high saturation magnetic flux density of 1.67–1.72 T after annealing at optimal annealing conditions. In addition, the alloys containing Mo have better transient effective permeability stability with increase in frequency. Decreasing the melt-spinning wheel speed can widen the annealing temperature range for Fe82Cu1Si4B11.5Nb1.5 ribbon. Results indicate that these soft-magnetic nanocrystalline materials have good manufacturability for industrial production.Download high-res image (288KB)Download full-size image

•Ni76-xFexP14B6Ta4 (x = 10, 20, 30 at.%) BMGs are synthesized by combining fluxing treatment and J-quenching technique.•The critical diameter of the present Ni-based BMGs reaches the maximum value of 3 mm when x = 20.•The present Ni-based BMGs still exhibit good corrosion resistance after the Fe addition.•The compressive strength and plastic strain of the present Ni-based BMGs of x = 20 are 2.78 GPa and 6.6%.•The GFA and compressive plasticity of Ni-based BMGs can be enhanced significantly through the Fe addition.Bulk Ni76-xFexP14B6Ta4 (x = 10, 20, 30, all in at.%) glassy alloy rods with diameters of 1.5–3.0 mm are synthesized by combining fluxing treatment and J-quenching technique, and the effects of Fe substitution for Ni on the glass forming ability (GFA), thermal stability, mechanical properties, and corrosion resistance of the present Ni-based bulk metallic glasses (BMGs) have been studied systematically in this work. It is found that the appropriate substitution of Fe for Ni can greatly enhance the GFA of the present Ni-based alloys, and the critical diameter for fully glass formation gets to the maximum value of 3.0 mm when the substitution content of Fe for Ni is 20 at.%. The corrosion tests show that the substitution of Fe for Ni causes a certain reduction of the corrosion resistance of the present Ni-based BMGs, but the corrosion current densities in both 1 M NaCl and 1 M HCl solutions are below the order of magnitude of 10−5 A/cm2 and the corrosion rate in1 M HCl solution is in the order of magnitude of 0.1 mm/year, still exhibiting a good corrosion resistance. The present Ni-based BMGs exhibit a compressive strength of more than 2.6 GPa and, more significantly, the substitution of Fe for Ni greatly enhances the compressive plasticity of the present Ni-based BMGs and the compressive plastic strain gets up to 6.6% when 20 at.% of Ni is substituted by Fe. This work indicates that the GFA and mechanical properties of Ni-based BMGs can be enhanced significantly through the Fe addition.

•The induction and remanence at 80 A/m decline with increasing operating temperature.•Temperature below 160 °C impacts slightly on core loss with induction is < 1.1 T.•The peaks of the imaginary part shift to higher frequency with decreasing real part.•The variations of permeability dispersion fits to Havriliak-Negami (H-N) model.The alternation of dynamic magnetic characteristics with operating temperature and magnetizing frequency in annealed Fe73.5Cu1Nb3Si15.5B7 nanocrystalline alloy core was systematically studied by AC B-H loop tracer and complex permeability approach. It is found that the operating temperature below 160 °C has little influence on core loss when the induction (B) is less than 1.1 T. As B becomes higher, core loss measured at higher temperature becomes larger. The B and remanence (Br) at 80 A/m under power frequency both decline slightly as the temperature goes up. Furthermore, the real part of permeability (μ') increases at first and then decrease with the rise of temperature. The peaks of the imaginary part of permeability (μ'') shift to higher frequency side with decreasing μ' over operating temperature. In addition, the variations of permeability dispersion with the elevated in the operating temperature of the annealed nanocrystalline core are explained by fitting to Havriliak-Negami (H-N) model, revealing that temperature impact on the magnetic relaxation time.

•Fe(Co)SiBPCCu nanocrystalline alloys were successfully developed.•The FeSiBPCCu alloy exhibits high Bs of 1.83 T and low Hc of 5.4 A/m.•Excessive substitution of Co for Fe drastically deteriorates magnetic properties.•The FeSiBPCCu alloy exhibits good frequency properties and temperature stability.•The excellent properties stem from the uniform microstructure and wide domains.Fe84.75-xCoxSi2B9P3C0.5Cu0.75 (x = 0, 2.5 and 10) nanocrystalline alloys with excellent magnetic properties were successfully developed. The fully amorphous alloy ribbons exhibit wide temperature interval of 145–156 °C between the two crystallization events. It is found that the excessive substitution of Co for Fe greatly deteriorates the magnetic properties due to the non-uniform microstructure with coarse grains. The alloys with x = 0 and 2.5 exhibit high saturation magnetization (above 1.83 T), low core loss and relatively low coercivity (below 5.4 A/m) after annealing. In addition, the Fe84.75Si2B9P3C0.5Cu0.75 nanocrystalline alloy also exhibits good frequency properties and temperature stability. The excellent magnetic properties were explained by the uniform microstructure with small grain size and the wide magnetic domains of the alloy. Low raw material cost, good manufacturability and excellent magnetic properties will make these nanocrystalline alloys prospective candidates for transformer and motor cores.Download high-res image (179KB)Download full-size image

•Ni77 − x − yMoxCryNb3P14B6 (x = 5–9, y = 0–5) BMGs were prepared by fluxing treatment and J-quenching technique.•The Dmax for fully glass formation reaches to the maximum of 1.5 mm for Ni67Mo5Cr5Nb3P14B6.•The present Ni-based BMGs exhibit the excellent corrosion resistance with a Icorr of ~ 10− 6 A/cm2 and a Rcorr < 10− 3 mm/year in 1 M HCl and 1 M NaCl solutions.•The present Ni-based BMGs exhibit the strength of 2.5–3.4 GPa, but almost no compressive plasticity.Bulk Ni77 − x − yMoxCryNb3P14B6 (x = 7 y = 0; x = 8 y = 0; x = 9 y = 0; x = 5 y = 3; x = 5 y = 5; x = 5 y = 8; x = 8 y = 3; x = 8 y = 5, all in at.%) glassy alloy rods with the diameters of 1.0–1.5 mm were synthesized by combining fluxing technique and J-quenching technique. The effects of Mo and Cr substitution for Ni on the glass forming ability (GFA), thermal stability, mechanical properties and corrosion properties of the present Ni-based bulk metallic glasses (BMGs) had been studied systematically. It is found that the substitution of an appropriate amount of Cr and Mo for Ni can enhance the GFA of the present Ni-based alloys, while excessive substitution will lead to the degradation of the GFA. The corrosion tests show that the corrosion current density and corrosion rate of most of the present Ni-based BMGs in 1 M NaCl and 1 M HCl solutions are in the order of 10− 6 A/cm2 and 10− 2 mm/year, respectively, exhibiting very high corrosion resistance. The addition of the appropriate Mo content and the Cr content as much as possible are benefit for the enhancement of the corrosion resistance of the present Ni-based BMGs. The compressive tests show that that the present Ni-based BMGs exhibit a compressive strength of 2.5–3.4 GPa, but nearly zero compressive plasticity.

•Flexural strength reliability of bulk metallic glasses (BMGs) plates is analyzed for the first time using Weibull statistics.•The m value of the Zr48Cu45Al7 BMG (m = 34) is much higher than the values of fine ceramics.•Only m values obtained by flexural strength statistics can be used to make a convincible comparison with those of ceramics.The flexural strength reliability of bulk metallic glasses (BMGs) plates is analyzed using Weibull statistics. The Weibull modulus (m) and characteristic strength (σ0) of the Zr48Cu45Al7 BMG are 34 and 2630 MPa, respectively, which are much higher than the values of fine ceramics (m < 30, σ0 < 1600 MPa). In particular, the m values obtained by flexural strength and compressive strength statistics of the Mg61Cu28Gd11 BMG are 5 and 33, respectively, indicating that the m values of BMGs are test method dependent, and only the m values obtained by flexural strength statistics can be used to make a convincible comparison with those of ceramics.

Shear bands play a key role in the plastic deformation of metallic glasses (MGs). Even though there are extensive studies on the initiation and propagation of shear bands, the interactions among them have not been systematically studied yet. The interactions between the primary shear bands (PSBs) and secondary shear bands (SSBs) in a ductile Zr-based MG were studied. The residual stress near PSBs can deflect the propagation direction and reduce the propagation velocity of SSBs, which contributes to the plasticity and toughness of the MG. It was demonstrated that the probability and strength of the interactions between PSBs and SSBs would become stronger for MGs with larger Young's modulus and smaller shear modulus, i.e., larger Poisson's ratio. These results are valuable in understanding the plastic deformation of MGs and may be helpful in designing new MGs with desirable mechanical properties.

•Novel Fe83-xCoxSi2B11P3C1 (x = 0, 5, 10, 15 and 20) amorphous alloys were prepared.•With Co addition, Bs increased to 1.74 T while soft magnetic properties deteriorated.•Temperature intervals between Tx1 and Tc decrease from 130 °C to negative value.•Large Tx1-Tc is crucial for gaining good softness for ferromagnetic amorphous alloys.Effects of Co addition on magnetic properties and thermal parameters of high saturation magnetic flux density (Bs) Fe83-xCoxSi2B11P3C1 (x = 0, 5, 10, 15 and 20) amorphous alloys are investigated. The Bs of the Co-doped alloys can be effectively enhanced to 1.74 T from 1.67 T. Curie temperature (Tc) increases greatly and even exceeds the first crystallization temperature (Tx1) with the increase of Co content to x = 20. The soft-magnetic properties of these high Bs alloys deteriorate with the introducing of Co. It is found that soft-magnetic properties correlate strongly to temperature interval between Tc and Tx1 (Tx1-Tc) of the Co-doped high Bs FeSiBPC amorphous alloys. The domain structures are characterized via the Magneto-optical Kerr Microscope in order to demonstrate the importance of large Tx1-Tc on achieving good soft-magnetic properties.

•FeNiBSiPNb BMGs with high GFA and excellent magnetic properties were developed.•BMGs with maximum diameters of 3 mm are fabricated by copper mold casting method.•The alloys exhibit low Hc of 0.5–0.8 A/m, high μe of 1.6–2.85 × 104.•The Bs changes regularly with the content variations of P, B and Si.•GFA criterions containing Trg, α, β and γ are effective in evaluating the GFA.Fe38Ni38Nb2.5B21.5−x−yPxSiy (x, y = 1–8) bulk metallic glassy alloys with high glass forming ability and excellent magnetic properties were developed. Bulk samples with maximum diameters of 3 mm are fabricated by copper mold casting method. The glassy alloys have large ΔTx of 40–70 K. The alloys exhibit excellent magnetic properties like extremely low Hc of 0.5–0.8 A/m, high μe of 1.6–2.85 × 104 and comparatively high Bs of 0.6–0.8 T which changes regularly with the content variations of P, B and Si. By ascertaining applicability of the empirical GFA criterions, Trg, α, β and γ can be used in evaluating the GFA of FeNiBSiPNb system alloys.

•Observation on fracture surface after compression test of bulk metallic glasses.•A simple mathematical model successfully described the load–displacement behavior.•Planar faults or defects were found to be responsible for the crack initiation.•A new mechanism of how shear bands evolve into micro-cracks was proposed.In the present work, the cracks formation and propagation behavior of a ductile Zr-based bulk metallic glass with single dominant shear band deformation was investigated. From the ideal compressive load–displacement curve of the sample with single shear band deformation, the instant at which the shear band turns into cracks and the total area of cracked-regions prior to failure were analyzed. Further investigations revealed that the micro-cracks might have originated from the local planar faults or defects within the shear plane along the shear direction. The existence of such planar faults (steps) was consistent with the observations of the surfaces of unfractured and fractured samples. Based on these results, a new interpretation of how shear bands evolve into the present micro-cracks was proposed. These novel results provide a new perspective to understand the deformation behavior of metallic glasses.

•Nanoporous silver (NPS) micro-particles were prepared by dealloying of Mg-Ag alloy.•Ultrasonic irradiation (UI) plays a key role in preparing the NPS micro-particles.•The ligaments size of the NPS is insensitive to H+ concentration and UI intensity.•Smaller NPS particles (50±20 μm) can be obtained in high concentration HCl solution.Nanoporous silver (NPS) micro-particles were prepared successfully by combining high-intensity ultrasonic irradiation (UI) and chemical dealloying process of rapidly solidified Mg-Ag precursors. The length scale of the ligaments in NPS is 100±30 nm, which is insensitive to the concentration of the hydrochloric acid (HCl) solution and the intensity of the UI. However, smaller NPS micro-particles with a size of 50±20 μm can be obtained by dealloying the precursor ribbons in a much more concentrated HCl solution under UI. It is supposed that the cavitation phenomena induced by UI treatment may play a key role in disaggregating the precursor ribbons into the present NPS micro-particles during dealloying.

•(Fe0.76 − xTmxB0.24)96Nb4 amorphous alloys in bulk form were fabricated.•The thermal stability, magnetic and magnetocaloric properties were investigated.•Tm substitution enhances the GFA and tunes the TC to near room temperature.•The Tm2Fe14B1 phase observed at higher Tm additions can influence the MCE.Magnetic properties and magnetocaloric effect in (Fe0.76 − xTmxB0.24)96Nb4 (x = 0, 0.01, 0.05, 0.1, 0.17 and 0.18) metallic glasses have been studied. The appropriate substitution of Fe by Tm increases the glass-forming ability of the alloys and allows tuning the Curie temperature (TC) to near room temperature. A linear relationship between magnetic entropy change and saturation magnetization has been observed. The formation of minority nanocrystalline Tm2Fe14B1 phase has been observed at higher Tm additions, which could influence the magnetocaloric effect of the alloy. These Tm doped Fe-based alloys, with enhanced thermal stability, good magnetocaloric responses and tunable TC, are good candidates for near room-temperature magnetic refrigerants.

•The high-entropy bulk metallic glasses with good MCE were fabricated.•The HE-BMGs show large maximum magnetic entropy changes.•The spin glass behavior makes the magnetic entropy change peaks much broader.•Their magnetic transition temperature can be tuned in a large temperature range.In this article, we report the formation of the high-entropy Gd20Tb20Dy20Al20M20 (M = Fe, Co and Ni) bulk metallic glasses with good magnetocaloric properties. Compared with most of the rare earth based metallic glasses, these alloys are found to have the comparably large maximum magnetic entropy changes (ΔSM), but much broader widths of the ΔSM peaks, and hence larger refrigerant capacity (RC). This can be attributed to the combination of the spin glass behaviors and the complicated compositions in these alloys. Our work show that the high entropy bulk metallic glasses is a promising candidate material as the magnetic refrigerant.

A novel in situ forming Mg66Zn29Ca4Y1 composite comprising microsized icosahedral quasicrystal phase (I-phase) particles dispersed within a Mg-based metallic glass matrix was synthesized. The size and volume fraction of the I-phase particles are ∼25–35 μm and ∼10%, respectively. The I-phase particles can noticeably improve both the strength and plasticity of the composite. The mechanism of the hard I-phase particles on the deformation and fracture behaviors of the composite and the synthesis strategy of the composite are discussed.A novel in situ forming Mg66Zn29Ca4Y1 composite comprising micro-sized icosahedral quasicrystal phase (I-phase) particles dispersed within the Mg-based metallic glass matrix was synthesized.

•Relation between GFA and electronic structure of RE doped BMGs is investigated.•Tm enhances RE–B bonds and decreases the density of states near the Fermi level.•Magnetic properties of the alloys are related to the electronic structure of RE.(Fe0.71RE0.05B0.24)96Nb4 (RE = Gd, Tb, Ho, Er, Tm) bulk metallic glasses (BMGs) were found exhibiting excellent glass-forming ability (GFA) with critical diameters ranging from 3.5 to 6.5 mm, and high compressive fracture strength larger than 4300 MPa. Moreover, they displayed good soft-magnetic properties with saturation magnetic flux density of 0.71–0.87 T, coercive force of 1.23–39.76 A/m and effective permeability of 1500–12,740 at 1 kHz. X-ray photoelectron spectroscopy was performed to clarify the origin of the excellent GFA from the viewpoint of electronic structure. It was found that the Tm doped alloy displayed unique electronic structure including the deepest core-level binding energy, the most numerous RE–B bonds and the minimum density of states near the Fermi level, making this alloy the best glass former. The various trends noticed in the magnetic properties were ascribed mainly to the differences in the magnetic anisotropy and magnetic moment of RE elements.

The effects of Co addition on the microstructure, crystallization processes and soft magnetic properties of (Fe1−xCox)83Si4B8P4Cu1 (x=0.35, 0.5, 0.65) alloys were investigated. The experimental results demonstrated that the addition of Co decreased the thermal stability against crystallization of the amorphous phase, and thus improved the heat treatment temperature of this alloy. FeCoSiBPCu nanocrystalline alloys with a dispersed α′-FeCo phase were obtained by appropriately annealing the as-quenched ribbons at 763 K for 10 min. The α′-FeCo with grains size ranging from 9 to 28 nm was identified in primary crystallization. The coercivity (Hc) markedly increased with increasing x and exhibited a minimum value at x=0.35, while the saturation magnetic flux density (Bs) shows a slight decrease. The (Fe0.65Co0.35)83Si4B8P4Cu1 nanocrystalline alloy exhibited a high saturation magnetic flux density Bs of 1.68 T, a low coercivity, Hc of 5.4 A/m and a high effective permeability µe of 29,000 at 1 kHz.

•P added FeBSiP alloys exhibit excellent soft magnetic properties and high GFA.•Fe78Si4B13P5 alloy can be made into bulk sample with diameter of 1.5 mm.•P addition will decrease the anti-oxidation behavior and Bs.•Slight oxidation can improve the soft magnetic properties of low P content alloys.The effect of P on the glass forming ability, soft magnetic properties and oxidation behavior of Fe78B13Si9-xPx (x = 0–7) amorphous alloys were investigated. It is found that the proper introduction of P, can effectively improve the glass forming ability and stability of supercooled liquid region. Fe78Si4B13P5 BMG, which exhibits high saturation flux density of 1.56 T, was readily made into rod sample with a diameter of 1.5 mm under air casting atmosphere. P bearing alloys also exhibit excellent soft magnetic properties containing low coercivity of 1.7–2.7 A/m, and high effective permeability of 8200–12,200. Slight oxidation can further improve the coercivity to a lower value of 1.1 A/m and the higher effective permeability to 11,900 for the alloys with P content no more than 3 at. %. Excessive addition of P may deteriorate the glass forming ability, soft magnetic properties and oxidation behavior. Magnetic domain revealing the magnetization process of the amorphous ribbons were characterized to explain the effect of P on magnetic properties and oxidation behavior.

•The effect of longitude magnetic field on magnetism of powder cores was researched.•With the increase of intensities of magnetic field, permeability was improved.•With the increase of intensities of magnetic field, core loss was decreased.•Although permeability was improved, DC bias property keeps an excellent level.The longitude magnetic field annealing on the soft magnetic properties of Fe-based Fe78Si9B13 amorphous powder cores were investigated. The magnetic properties of powder core greatly change when annealed under longitude magnetic field. With the increase of magnetic field intensity, the permeability of annealed powder core further increase. The core shows an enhanced effective magnetic permeability of 66 after longitude magnetic field annealing at an applied field of 30 Oe and temperature of 400 °C, which is attributed to the relief of internal stress and the variation of atomic structure. The permeability was improved by 8% and the frequency stability of FeSiB amorphous powder core is up to 2 MHz. The core loss decreases obviously and DC bias property stays at a same level compared with zero field treatment with the increase of magnetic field intensity. For the powder cores, the core loss ranges from 90 to 180 W/kg at 50 mT and 100 kHz, and DC bias property reaches over 70% at 100 Oe. This work provides a novel approach to improve permeability for Fe78Si9B13 powder cores and also validates the application prospect of powder core in the work condition of different ripple currents, different loads and a wide frequency range (10 kHz–2 MHz).

•The absorber has excellent corrosion, wear resistance and soft-magnetic properties.•The reflection loss reaches −60.3 dB at 7.08 GHz for the composite(30 vol % filler).•Dual absorption peaks appear beyond 4.01 mm for the composite(30 vol % filler).•This absorbing material has potential X-band application.The FeCrMoNiPBCSi amorphous alloy system with good soft-magnetic property and high glass forming ability was utilized to prepare amorphous powders which are integrated for electromagnetic wave absorbing composite with silicone-matrix. The absorption parameters were measured by tuning the sample thickness and volume fraction strictly. The results show that FeCrMoNiPBCSi amorphous alloy system is more prone to attain impedance matching and has strong ability on electromagnetic wave attenuation. The value of reflection loss reaches −60.3 dB at 7.08 GHz for the composite (30 vol % powders) and the bandwidth reaches 2.30 GHz for RL  < −10 dB.