Glass formation and magnetic properties of Fe-based metallic glasses fabricated by low-purity industrial materials

Fe-based metallic glasses of (Fe₇₄Nb₆B₂₀)_100-xCr_x (x=1, 3, 5) with high glass forming ability (GFA) and good magnetic properties were prepared using low-purity raw materials. Increasing Cr content does not significantly change glass transition temperature and onset crystallization temperature, while it enhances liquidus temperature. The addition of Cr improves the GFA of the (Fe₇₄Nb₆B₂₀)_100-xCr_x glassy alloys compared to that in Cr-free Fe-Nb-B alloys, in which the supercooled liquid region (ΔT_x), T_rg and γ are found to be 50–54 K, 0.526–0.538, and 0.367–0.371, respectively. The (Fe₇₄Nb₆B₂₀)_100–xCr_x glassy alloys exhibit excellent soft magnetic properties with high saturation magnetization of 139–161 A·m²/kg and low coercivity of 30.24–58.9 A/m. Present Fe-Nb-B-Cr glassy alloys exhibiting high GFA as well as excellent magnetic properties and low manufacturing cost make them suitable for magnetic components for engineering application.     

Magnetic properties and magnetocaloric effect of FeCrNbYB metallic glasses with high glass-forming ability

The influences of Cr addition on the Curie temperature (T_C), glass-forming ability (GFA), and magnetocaloric effect were investigated in FeCrNbYB metallic glasses. It was found that the addition of Cr element slightly decreases the GFA and saturation magnetization, whereas effectively modulates T_C. By the method of copper mold casting, bulk metallic glasses (BMGs) with critical diameters up to 5 mm can be obtained in Fe_68−xCr_xNb₄Y₆B₂₂ (x = 2–6) alloys. The resulting metallic glasses exhibit T_C of 271–367 K and excellent magnetocaloric properties, including magnetic entropy change of 0.76–1.05 J/kg K, and refrigerant capacity of 83–93 J/kg under a low field change of 1.5 T. In addition, they exhibit a wide supercooled liquid region of 116–135 K. The successful synthesis of the FeCrNbYB BMGs with near room-temperature magnetocaloric properties is encouraging for the future development of Fe-based BMGs as a new magnetic refrigerant in magnetic cooling system.     

Thermal stability,magnetic and mechanical properties of Fe–Dy–B–Nb bulk metallic glasses with high glass-forming ability

The effects of Dy addition on the thermal stability, glass-forming ability (GFA), magnetic and mechanical properties of quaternary (Fe_0.76−xDy_xB_0.24)₉₆Nb₄ (x = 0–0.07) bulk metallic glasses (BMGs) were investigated. Increasing Dy content from x = 0 to 0.05 extended the supercooled liquid region up to 112 K, allowing the fabrication by copper mold casting of BMGs rods with 5.5 mm in diameter. The high GFA was found to be related to the structure of primary crystalline phase. For the x = 0.05 alloy, the competitive formation process of the complex Fe₂₃B₆ and Dy₂Fe₁₄B phases enabled to obtain the largest GFA value. Moreover, the Fe–Dy–B–Nb BMGs exhibited good soft-magnetic properties, i.e., high saturation magnetization of 1.18–0.56 T and low coercive force of 1.9–21.6 A/m. In addition, the glassy alloy rods also showed high compressive fracture strengths of 4400–4150 MPa and high Vickers hardness of 1110–1090 kg/mm².     

Formation of centimeter Fe-based bulk metallic glasses in low vacuum environment

The formation of a Fe_43.7Co_7.3Cr_14.7Mo_12.6C_15.5B_4.3Y_1.9 bulk metallic glass (BMG) was attempted in low vacuum environment and in air using commercial raw materials. The glass forming ability of the Fe-based alloys was studied by X-ray diffraction (XRD), differential scanning calorimetry (DSC) and differential thermal analyzer (DTA). It was found that cylindric rods with diameters ranging from 10 mm to 5 mm could be successfully fabricated by copper-mold casting in the pressures from 1.5 Pa to 10⁵ Pa (10⁵ Pa = 1 atm). All BMGs exhibit a distinct glass transition and wide supercooled liquid region. The preparation condition seems not significantly affected by the thermodynamic parameters of BMG, such as supercooled liquid region, glass transition temperature and melting process. The oxygen content of the alloys prepared in different vacuum conditions was measured by a LECO oxygen analyzer, which revealed that the oxygen content was less than 100 ppm for all BMGs prepared, even in air. The good glass forming ability and excellent oxidation resistance for the present Fe-based alloy are discussed.     

Quaternary Fe-based bulk metallic glasses with a diameter of 5 mm

Bulk metallic glasses with a diameter of 5 mm were obtained by drop casting in the quaternary Fe–B–Y–Nb and Fe–B–Y–Mo systems. Starting from the best glass former Fe_71.2B₂₄Y_4.8 in the ternary Fe–B–Y system, the search quickly led to the discovery of the quaternary good glass formers (Fe_71.2B₂₄Y_4.8)₉₆Nb₄, (Fe_73.2B₂₂Y_4.8)₉₅Mo₅ and (Fe_70.7B₂₄Y_5.3)₉₅Mo₅ after trying only around a dozen of alloys. No obvious glass transition event was observed for these quaternary alloys. No Nb and Mo containing crystalline phases were detected in the alloys studied. The potential beneficial effects of Nb and Mo in enhancing the glass forming ability (GFA) of the Fe–B–Y alloy system are discussed.     

Novel FePBNbCr glassy alloys “SENNTIX” with good soft-magnetic properties for high efficiency commercial inductor cores

According to a recent study, Fe-based glassy alloys are expected good soft-magnetic properties such as high saturation magnetization and lower coercive force. We focused on Fe-based glassy alloys and have succeeded in developing novel glassy Fe_97?x?yP_xB_yNb₂Cr₁ (x = 5–13, y = 7–15) alloys for an inductor material. The glassy alloy series of Fe_97?x?yP_xB_yNb₂Cr₁ (x = 5–13, y = 7–15) have high glass-forming ability with the large critical thickness of 110–150 μm and high B_s of 1.25–1.35 T. The glassy alloy powder with chemical composition Fe₇₇P_10.5B_9.5Nb₂Cr₁ exhibits an excellent spherical particle shape related to the lower melting point and liquid phase point. In addition, Fe–P–B–Nb–Cr powder/resin composite core has much lower core loss of 653–881 kW/m³, which is approximately 1/3 lower than the conventional amorphous Fe–Si–B–Cr powder/resin composite core and 1/4 lower than the conventional crystalline Fe–Si–Cr powder/resin composite core due to the lower coercive force of 2.5–3.1 A/m. Based on above results, the glassy Fe₇₇P_10.5B_9.5Nb₂Cr₁ alloy powder enable to achieve ultra-high efficient and high quality products in a commercial inductor. In fact, the surface mounted inductor using Fe–P–B–Nb–Cr powder/resin exhibits the high efficiency of approximately 2.0% compared with the conventional inductors made of the crystalline Fe–Si–Cr powder/resin composite core.     

Bulk glassy Fe-Cr-Mo-C-B alloys with high corrosion resistance

The preparation of bulk glassy alloys with high glass-forming ability and high corrosion resistance in Fe-based system was succeeded by means of copper-mold casting. The temperature interval of supercooled liquid region (ΔT_x) is as large as 53-62 K and the reduced glass transition temperature (T_g/T_m) is as high as 0.62-0.63 for the cast Fe_50−xCr₁₆Mo₁₆C₁₈B_x (x=4, 6, 8 at.%) glassy alloys. The corrosion rates of the Fe_50−xCr₁₆Mo₁₆C₁₈B_x glassy alloys with a diameter of 1.2 mm were in the range of 10⁻³-10⁻² mm year⁻¹ in 1, 6 and 12 N HCl solutions at 298 K. The bulk glassy alloys are spontaneously passivated in 1 and 6 N HCl solutions with wide passive region and low passive current density. They do not suffer pitting corrosion even when polarized anodicly in 12 N HCl solution up to 1.0 V (Ag/AgCl). The high corrosion resistance is due to the formation of chromium-rich passive films during immersion in HCl solutions. In addition, the increase of boron content in alloys improves the corrosion resistance of the bulk glassy alloys within the composition range examined.     

Fe-based glassy alloys with high iron content and high saturation magnetization

Iron-based bulk metallic glasses (BMGs) are attractive due to their excellent magnetic properties. It is known that increasing the iron content in alloys would enhance the magnetic property of glassy alloys, but would reduce their glass forming ability. Despite researchers are keen to develop Fe-based BMGs with high Fe content, BMG with Fe content higher than 79 at.% has not been reported. Here we report that Fe-based BMGs with Fe content as high as 78 ～ 81 at.% have been successfully prepared. The as-prepared Fe₈₁Mo₁P_7.5C_5.5B₂Si₃ BMG possesses a saturation magnetization of 1.64 T, which is significantly higher than the reported value in BMGs.     

Preparation and properties of quaternary CoMoPB bulk metallic glasses

A new series of Co_80−xMo_xP₁₄B₆ (x = 7, 9, and 11 at%) bulk glassy alloys were successfully prepared by a combination method of fluxing treatment and J-quenching technique. The glass-forming ability (GFA) of the obtained Co-based alloys is sensitive to the Mo content substituted for Co, and the maximum attainable diameter for a fully amorphous state can reach 4.5 mm at x = 9. The compressive tests show that the obtained Co-based BMGs exhibit a compressive strength of 3.3–3.9 GPa, but nearly zero compressive plasticity. The new Co-based BMGs possess good soft magnetic properties, and their saturated magnetization values decrease from 47 emu/g (0.45 T) to 14 emu/g (0.14 T) with increasing the content of the Co substitute from 7 at% to 11 at%, which may be attributed to the anti-ferromagnetic coupling between the Mo and Co atoms. Because of their good GFA, high Co content, few constituting elements, and relatively high strength, the obtained Co-based BMGs (especially Co₇₁Mo₉P₁₄B₆ BMG) can be considered promising as starting alloys to develop the new Co-based BMGs for the advanced structural and functional applications.     

Towards improved integrated properties in FeCrPCB bulk metallic glasses by Cr addition

Fe-based soft-magnetic metallic glasses (MGs) of Fe_80−xCr_xP₉C₉B₂ (x = 0, 2, 5, 8 and 16 at.%) with high glass-forming ability (GFA), good soft-magnetic properties and high corrosion resistance are fabricated. With the addition of Cr to FePC-based alloys, the GFA and saturation magnetization (M_s) slightly decrease while the corrosion resistance effectively increases. The Fe–Cr–P–C–B BMGs exhibit good GFA and fully glassy rods can be produced up to 1.8 and 1.5 mm in diameter for the 2 and 5 at.% Cr added alloys, respectively. The alloys with 2 and 5 at.% Cr addition also show good soft-magnetic properties featured by high M_s of 1.16 and 1.04 T, low coercivity of 2.7 and 2.2 A/m, respectively. Besides, the corrosion behavior of the alloys was studied by immersion tests and potentiodynamic polarization measurements. It was found that the addition of Cr efficiently enhances the corrosion resistance of Fe–Cr–P–C–B alloys and the glassy alloy with 5 at.% Cr addition exhibits better corrosion resistance in comparison with the stainless steel SUS304 in 3 mass% NaCl solution. The combination of large GFA, good soft-magnetic properties, high corrosion resistance as well as low cost makes the Fe–Cr–P–C–B alloys as promising soft-magnetic and anti-corrosive materials for industrial applications.     

Viscosity and fragility of the supercooled liquids and melts from the Fe–Co–B–Si–Nb and Fe–Mo–P–C–B–Si glass-forming alloy systems

The dynamic viscosity of four Fe-based bulk metallic glass-forming alloys, [(Fe_0.5Co_0.5)_0.75B_0.2Si_0.05]₉₆Nb₄ (alloy A), {[(Fe_0.5Co_0.5)_0.75B_0.2Si_0.05]_0.96Nb_0.04}_99.5Cu_0.5 (alloy B), Fe₇₄Mo₄P₁₀C_7.5B_2.5Si₂ (alloy C) and (Fe_0.9Ni_0.1)₇₇Mo₅P₉C_7.5B_1.5 (alloy D), was investigated as a function of temperature in the supercooled liquid region, as well as above the melting point. The alloy B is Cu-added alloy A, while the alloy D was obtained upon fine-tuning the alloy C composition. All these alloys may form bulk metallic glasses upon copper mold casting. The viscosities in the supercooled liquid region were calculated using the data obtained upon parallel plate rheometry measurements, as well as upon differential scanning calorimetry (DSC). The values of the supercooled fragility parameter m, 61, 66, 52 and 60 for the alloys A, B, C and D respectively, indicate that these alloys are intermediate glass formers. The behavior of the same alloys, in the molten state, was studied using a high temperature torsional oscillation cup viscometer. The values of the corresponding fragility parameter M was calculated as 5.03, 5.91, 4.25, 4.93 for the alloys A, B, C and D, respectively. They confirm the supercooled liquid behavior and predict that the alloys A and C may form glasses easier than the fine-tuned compositions B and D. Angell plot is constructed for the entire range of viscosities and the values from both regions, i.e. above melting point and supercooled liquid region, fit well with the model.     

Role of Mo in the local configuration and structure stabilization of amorphous steels,a Synchrotron X-ray diffraction and Mössbauer study

Amorphous steels are promising materials with potential structural applications. The glass-forming ability (GFA) and mechanical properties of metallic glasses are intimately related to the local structure. In Fe-based alloys, Cr and Mo content seem to play a key role in stabilizing the amorphous atomic-level structure. Here we present a study on the effects of changing Mo content in Fe_72?xC₇Si_3.3B_5.5P_8.7Cr_2.3Al₂Mo_x amorphous steels. We study the local structure of these alloys by Synchrotron X-ray diffraction and Mössbauer spectroscopy. The results show how the amorphous phase evolves from a ferromagnetic Fe-rich structure to a structure with predominance of paramagnetic environments with the increase of Mo content. The changes in the distribution of magnetic environments cannot be attributed only to the Fe–Mo substitution but to a change of local configuration in the amorphous phase.     

APT characterization of some iron-based bulk metallic glasses

A microstructural characterization was performed on 3 iron-based bulk metallic glasses. These alloys were an arc cast Fe₆₁Y₂Zr₈Co₆Al₁Mo₇B₁₅ A2 alloy, a twin roll cast Fe₆₈Y₂Zr₂Nb₂Cr_1.5V_4.5B₂₀ DarpaQ21 alloy and a vacuum induction melted Fe_50.7Y_1.5Cr_14.5Mo₁₃C_14.8B_5.5 Darva101-Y alloy. The alloys were characterized by scanning electron microscopy and atom probe tomography in the as-cast condition. Some micrometer and nanometer scale precipitates were observed in all 3 alloys indicating that the alloy compositions are not fully optimized in the as-cast state. The Darva101-Y alloy was also characterized after annealing above the onset of crystallization temperature for 1 h at 610 °C. This annealing treatment produced a mixture of crystalline phases: M₆(BC) and Fe₁₄Y₂B in addition to a high temperature M₂₃C₆ phase that is indicated from XRD and previous research.     

Structure and thermal behavior of multicomponent Fe68−xNixZr15Nb5B12 (x = 5, 10, 15, 20) alloys

Multicomponent Fe_68−xNi_xZr₁₅Nb₅B₁₂ (x = 5, 10, 15, 20) alloy powders milled for 60 h were prepared by mechanical alloying (MA). The structure and crystallization behavior were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and differential thermal analysis (DTA). Ni enhances the amorphisation of alloy powders. Particle size increases with increasing Ni content. Both onset crystallization temperature T_x and the first crystallization peak temperature T_p of the four alloys shift to a higher temperature with increasing heating rate while melting temperature (T_m) is just the opposite. Fe_68−xNi_xZr₁₅Nb₅B₁₂ (x = 5, 10, 15, 20) alloys all have a large supercooled liquid region ΔT_x. The supercooled liquid region ΔT_x increases and the crystallization activation energy E decreases with increasing Ni content.     

Microstructure and properties of nanocrystalline Fe–Zr–Nb–B soft magnetic alloys with low magnetostriction

We have investigated the microstructure–property relationship of nanocrystalline Fe₈₅Zr_1.2Nb_5.8B₈ and Fe_85.5Zr₂Nb₄B_8.5 soft magnetic alloys in order to understand the origin of drastic change in the permeability regardless of the zero magnetostriction in these two alloy compositions. Plan-view and cross-section transmission electron microscopy (TEM) observations showed strongly textured α-Fe particles on the free surface of the Fe₈₅Zr_1.2Nb_5.8B₈ alloy ribbon, while uniform nanocrystalline microstructure was observed in the Fe_85.5Zr₂Nb₄B_8.5 alloy ribbon. The high Zr content of the latter improves the glass forming ability, thereby suppressing the surface crystallization, resulting in higher permeability. By adding Cu in the Fe–Zr–Nb–B alloy, uniform nanocrystalline microstructure was obtained, from which superior soft magnetic properties with zero magnetostriction was achieved.     

Study of serrated flow and plastic deformation in metallic glasses through instrumented indentation

The plastic deformation behavior and serrated flow in seven bulk metallic glass (BMG) systems were investigated through instrumented indentation. These materials include Ce₆₅Al₁₀Ni₁₀Cu₁₀Nb₅, Mg₆₅Cu₂₅Gd₁₀, Pd₄₃Ni₁₀Cu₂₇P₂₀, Cu₆₀Zr₂₀Hf₁₀Ti₁₀, Pt_57.5Cu_14.7Ni_5.3P_22.5, Ni₆₀Nb₃₇Sn₃ and Fe₄₃Cr₁₆Mo₁₆C₁₅B₁₀ BMGs, which show a glass transition temperature (T_g) ranging from 360 to 908 K at a heating rate of 0.33 K/s. Remarkable difference in deformation behavior was found among these BMGs in the load–depth curves during nanoindentation. Prominent serrations are observed in Mg-, Pt- and Pd-based BMGs with medium T_g during the loading process, whereas no distinct serrated flow was found in Ce-, Ni- and Fe-based BMGs with quite low or high T_g. The subsurface plastic deformation regions after indentation were investigated using depth-sensing microindentation to characterize the shear band feature developed in various BMG systems. The size of the shear band upset is found to be larger in the alloys with lower T_g. The effect of T_g on the operation of shear bands and the serrated flow behavior in various BMG systems were discussed.     

The Effects of Strain-Annealing on Tuning Permeability and Lowering Losses in Fe-Ni-Based Metal Amorphous Nanocomposites

Fe-Ni-based metal amorphous nanocomposites with a range of compositions (Fe_100?x Ni _x )₈₀Nb₄Si₂B₁₄ (30 ≤ x ≤ 70) are investigated for motor and transformer applications, where it is beneficial to have tunable permeability. It is shown that strain annealing offers an effective method for tuning permeability in these alloys. For an Fe-rich alloy, permeability increased from 4000 to 16,000 with a positive magnetostriction. In a Ni-rich alloy, permeability decreased from 290 to 40 with a negative magnetostriction. Significant elongations (above 60%) are observed during strain annealing at high stress. Crystallization products have been determined in all alloys heated to 480°C. γ-FeNi is formed in all alloys, while (Fe₃₀Ni₇₀)₈₀Nb₄Si₂B₁₄ also undergoes secondary crystallization at temperatures of approximately 480°C to form a phase with the Cr₂₃C₆-type structure and a likely composition of Fe₂₁Nb₂B₆. Toroidal losses have been measured for (Fe₇₀Ni₃₀)₈₀Nb₄Si _y B_16?y (0 ≤ y ≤ 3) at various annealing temperatures. At an induction of 1 T and frequency of 400 Hz and 1 kHz, the toroidal losses obtained are W_{1.0T, 400 Hz} = 0.9 W/kg and W_{1.0T, 1 kHz} = 2.3 W/kg, respectively. These losses are lower than losses recently reported for state of the art 3.0% and 6.5% silicon steels, a Metglas Fe-based amorphous alloy, and some Fe-based nanocomposites.     

FeSiBPNbCu alloys with high glass-forming ability and good soft magnetic properties

Effects of Cu addition on the glass-forming ability (GFA), thermal stability, magnetic properties and crystallization process of (Fe_0.76Si_0.09B_0.1P_0.05)_99−xNb₁Cu_x (x = 0, 0.25, 0.5, 0.75, 1) alloys were investigated. The introduction of Cu effectively stimulates the precipitation of the α-Fe(Si) without obvious deterioration of the GFA, and successfully modifies the simultaneous precipitation of α-Fe(Si), Fe₂B and Fe₃(B,P) phases in (Fe_0.76Si_0.09B_0.1P_0.05)₉₉Nb₁ alloy into separable precipitation of each phase at different temperatures during annealing, leading to the enhancement of soft magnetic properties. The saturation magnetic flux density of the representative (Fe_0.76Si_0.09B_0.1P_0.05)_98.25Nb₁Cu_0.75 alloy could be enhanced from 1.43 to 1.51 T after annealing at 530 °C for 10 min due to the precipitation of α-Fe(Si) nanoparticles with a diameter of about 22 nm dispersing randomly in the amorphous matrix. The integration of high GFA and excellent soft magnetic properties makes the FeSiBPNbCu alloys promising soft magnetic materials for industrial applications.     

Cr effects on magnetic and corrosion properties of Fe–Co–Si–B–Nb–Cr bulk glassy alloys with high glass-forming ability

Effects of the Cr addition on glass formation, magnetic and corrosion properties of {[(Fe_0.6Co_0.4)_0.75B_0.2Si_0.05]_0.96Nb_0.04}_100−xCr_x (x = 1, 2, 3, 4 at.%) alloys have been investigated. It was found that the addition of Cr element slightly decreases the glass-forming ability (GFA), but is very effective in increasing corrosion resistance and improving soft magnetic properties for this Fe–Co–B–Si–Nb bulk glassy alloy within the composition range examined. The Fe–Co–B–Si–Nb–Cr alloys exhibit high GFA. Full glassy rods with diameters up to 4 mm can be synthesized by copper mold casting. The Fe-based bulk glassy alloys (BGAs) exhibit a high saturation magnetization of 0.81–0.98 T as well as excellent soft magnetic properties, i.e., extremely low coercive force of 0.6–1.6 A/m and super-high initial permeability of 26,400–34,100. Furthermore, corrosion measurements show that corrosion rate and corrosion current density of these Fe-based BGAs in 0.5 M NaCl solution decrease from 7.0 × 10⁻¹ to 1.6 × 10⁻³ mm/year and 3.9 × 10⁻⁶ to 8.7 × 10⁻⁷ A/cm², respectively, with increasing Cr content from 0 to 4 at.%. The success of synthesizing the new Fe-based BGAs exhibiting simultaneously high GFA as well as excellent good soft magnetic properties combined with high saturation magnetization and enhanced corrosion resistance allows us to expect future progress as a new type of soft magnetic materials.     

Properties of the Ti<Subscript>40</Subscript>Zr<Subscript>10</Subscript>Cu<Subscript>36</Subscript>Pd<Subscript>14</Subscript> BMG Modified by Sn and Nb Additions

The results of investigation of the influence of additions of 2 and 3 at.% of Sn and simultaneously of Sn and 3 at.% Nb on microstructure and properties of the bulk metallic glasses of composition (Ti₄₀Cu_36?x Zr₁₀Pd₁₄Sn _x )_100?y Nb _y are reported. It was found that the additions of Sn increased the temperatures of glass transition (T _g), primary crystallization (T _x ), melting, and liquidus as well as supercooled liquid range (ΔT) and glass forming ability (GFA). The nanohardness and elastic modulus decreased in alloys with 2 and 3 at.% Sn additions, revealing similar values. The 3 at.% Nb addition to the Sn-containing amorphous phase decreased as well all the T _g, T _x , T _L, and T _m temperatures as ΔT and GFA; however, relatively larger values of this parameters in alloys containing larger Sn content were preserved. In difference to the previously published results, in the case of the amorphous alloys containing small Nb and Sn additions, a noticeable amount of the quenched-in crystalline phases was not confirmed, at least of the micrometric sizes. In the case of the alloys containing Sn or both Sn and Nb, two slightly different amorphous phase compositions were detected, suggesting separation in the liquid phase. Phase composition of the alloys determined after amorphous phase crystallization was similar for all compositions. The phases Cu₈Zr_3, CuTiZr, and Pd₃Zr were mainly identified in the proportions dependent on the alloy compositions.