Magnetic properties of nanocrystalline Finemet alloys with Co addition

This report focuses on ac magnetic properties of (Fe_0.5Co_0.5)_73.5Cu₁Nb₃Si_13.5B₉ alloy in the high temperature. The effects of replacing 50% Fe by Co in Fe_73.5Cu₁Nb₃Si_13.5B₉ alloy on the static magnetic properties have also been studied. Addition of Co leads to an increase around 110 K of the Curie temperature of the amorphous phase, much higher than Ge-containing Finemet alloy. The material has much better ac magnetic properties than Hitperm alloy. An excellent stability of initial permeability in high temperature (up to 650 K) and high frequency (up to 5 × 10⁵ Hz) can be observed with respect to the Co-free alloy.     

新型Fe80.5Si7.2B12.3非晶合金带材的退火工艺与磁性能

研究了新型Fe_80.5Si_7.2B_12.3非晶合金带材在不同退火工艺下的磁性能及磁损耗特性,并与传统的铁基非晶合金Fe₈₀Si₉B₁₁进行了对比。结果表明:新型Fe_80.5Si_7.2B_12.3非晶合金带材比Fe₈₀Si₉B₁₁具有更高的饱和磁感应强度,在励磁磁场强度为3500 A/m下其磁通密度值为1.607 T;在f=50 Hz、B_m=1.4 T下,经无磁场退火处理后其磁损耗高于Fe₈₀Si₉B₁₁,达到0.411 W/kg;经纵磁退火后磁损耗与Fe₈₀Si₉B₁₁基本相当,其值为0.197 W/kg;经横磁退火后损耗仅为0.175 W/kg低于Fe₈₀Si₉B₁₁,而且初始磁导率和恒磁导率均优于Fe₈₀Si₉B₁₁;新型Fe_80.5Si_7.2B_12.3非晶合金带材的最佳退火温度区间(360~400 ℃)与Fe₈₀Si₉B₁₁相当。     

Effect of Si addition on the glass-forming ability of a NiTiZrAlCu alloy

The effect of Si addition on the glass-forming ability (GFA) of a NiTiZrAlCu alloy was investigated by using differential scanning calorimetry (DSC), differential thermal analysis (DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The maximum diameter of glassy rods increased from 0.5 mm for the Ni₄₂Ti₂₀Zr₂₅Al₈Cu₅ alloy (the base alloy) to 2.5 mm for the Ni₄₂Ti₂₀Zr_21.5Al₈Cu₅Si_3.5 alloy and to 3 mm for the Ni₄₂Ti₁₉Zr_22.5Al₈Cu₅Si_3.5 alloy, when prepared by using the copper mould casting. The GFA of the alloys can be assessed by the reduced glass transition temperature T_rg(=T_g/T_l) and a newly proposed parameter, δ(=T_x/T_l − T_g). An addition of a proper amount of Si and a minor substitution of Ti with Zr can enhance the GFA of the base alloy by suppressing the formation of primary Ni(TiZr) and (TiZr)(CuAl)₂ phases and inducing the composition close to eutectic.     

The effect of Hf substitution for Zr on glass forming ability and magnetic property of FeCoZrMoBAlY bulk metallic glasses

Bulk metallic glasses (BMGs) Fe₆₁Co₆Zr_8−xHf_xMo₇B₁₅Al₁Y₂ (x = 0–8) have been produced by copper mold casting technique using industrial raw materials. The effect of substitution of Hf for Zr on the glass forming ability (GFA) and the magnetic property has been studied by X-ray diffraction (XRD), differential scanning calorimetry (DSC) and superconducting quantum interference device (SQUID). It was found that the substitution of an appropriate amount of Hf for Zr can improve the GFA of the base alloy Fe₆₁Co₆Zr₈Mo₇B₁₅Al₁Y₂, as demonstrated by the increase in reduced glass transition temperature T_rg (=T_g/T_l) and GFA parameters of γ (=T_x/T_g + T_l) and δ (=T_x/T_l − T_g). The Fe₆₁Co₆Zr₅Hf₃Mo₇B₁₅Al₁Y₂ alloy exhibits the highest GFA with the largest T_rg (0.612) and δ (1.633), and can cast a fully amorphous rod in 3 mm diameter. The substitution of Hf for Zr also enhances the magnetic properties, as verified by the increase in saturation magnetization (M_s) in the alloy of Fe₆₁Co₆Zr₃Hf₅Mo₇B₁₅Al₁Y₂, whose M_s is approximately 1.5 times higher than that of the base alloy (x = 0) at room temperature. Finally, the effect of the substitution of Hf for Zr on glass forming ability and magnetic properties is discussed.     

Structural properties and evaluation of crystal fraction by cryogenic heat capacity measurements of Fe-based nanocrystalline alloy

An amorphous Fe_73.5Cu₁Nb₃Si_13.5B₉ alloy was prepared by the rapid solidification technique. The rapidly quenched alloys have been annealed in the temperature range from 490 to 550 °C for 90 min and their structure was investigated by using X-ray diffraction (XRD). After annealing, at crystallization temperature, the microstructure of the samples composed of nanocrystalline Fe₃Si grains surrounded by the residual amorphous phase. The crystal fractions of the annealed samples were evaluated by heat capacity measurements. Heat capacities of the as-quenched and annealed samples were measured at different temperatures between 15 and 40 K. This method is useful for evaluating small changes in the amount of crystalline phase and provides a new tool for finding the nanocrystalline fraction. The volume fraction of the crystalline phase increased from 15.92 to 94.21% as annealing temperature increased from 490 to 550 °C.     

Small-angle neutron scattering and differential scanning calorimetry studies on the copper clustering stage of Fe–Si–B–Nb–Cu nanocrystalline alloys

The kinetics of copper clustering and primary crystallization of FINEMET type alloys with the compositions Fe_74.5−xSi_13.5B₉Nb₃Cu_x and Fe₇₇Si₁₁B₉Nb_3−xCu_x have been studied by small-angle neutron scattering (SANS) and high-sensitivity differential scanning calorimetry (DSC) in order to explain the different optimized Cu contents, x, for obtaining the highest permeability in these two alloys. SANS results have shown that the alloys with the optimized Cu contents have the finest nanocrystalline microstructures. Kinetic analyses of Cu clustering prior to primary crystallization have shown that the number density of Cu clusters becomes highest at the crystallization stage of -Fe primary crystals in the alloy containing an optimized amount of Cu.     

The microstructure of liquid immiscible Fe–Cu-based in situ formed amorphous/crystalline composite

In the microstructures of slowly and rapidly cooled liquid of the immiscible alloy Fe₃₀Cu₃₂Ni₁₀Si₁₃Sn₄B₉Y₂ two distinct regions were observed following arc melting and slow cooling, confirming that liquid/liquid phase separation had occurred. Rapid cooling from a temperature within the liquid immiscibility gap, melt spinning, resulted in an amorphous/crystalline composite, formed from the previously melted Fe- and Cu-rich regions, respectively. Transmission electron microscopic studies of this melt-spun ribbon revealed the glassy nature of the Fe-rich matrix, as well as of the Fe-rich spheres formed within the previously existing Cu-rich liquid.     

Effect of copper addition on the glass forming ability of a Fe–Co based alloy

The effect of copper addition on the glass forming ability of Fe₃₆Co₃₆Nb₄Si_4.8B_19.2 bulk metallic glass is studied. With 0.6 at% of copper addition, the critical size of the glassy rod formed is enlarged from 2 to 4 mm. Differential scanning calorimetry (DSC) study shows that the copper addition depressed the phase separation before the eutectic transformation upon cooling. And the crystallization of the alloy with copper addition is carried through three stages upon heating. Energy dispersive spectroscopy study shows that the copper addition reduces the oxygen content of the alloy.     

高饱和磁感Fe82Si3.8B13.9C0.3非晶铁芯的退火及浸漆工艺

研究了不同磁场退火和浸漆固化工艺对Fe₈₂Si_3.8B_13.9C_0.3非晶合金环形铁芯损耗和磁性能的影响,并与1K101合金铁芯进行了对比。结果表明:与1K101合金相比,Fe₈₂Si_3.8B_13.9C_0.3合金铁芯的最佳退火温度低于1K101合金,其中纵磁退火时达到最低,为330 ℃。纵磁退火Fe₈₂Si_3.8B_13.9C_0.3合金铁芯有着更高的饱和磁感应强度,B_{3500 A/m}=1.611 T。经350 ℃无磁场退火处理后,Fe₈₂Si_3.8B_13.9C_0.3合金铁芯的损耗P_{50 Hz, 1.4 T}=0.360 W/kg,稍高于1K101合金;经330 ℃纵磁退火处理后,Fe₈₂Si_3.8B_13.9C_0.3合金铁芯的损耗P_{50 Hz, 1.4 T}=0.257 W/kg,也高于1K101合金;经350 ℃横磁退火处理后损耗P_{50 Hz, 1.4 T}=0.163 W/kg,低于1K101合金。纵磁退火Fe₈₂Si_3.8B_13.9C_0.3合金铁芯经浸漆固化处理后,磁通密度B_{800 A/m}=1.341 T,比纵磁退火1K101合金浸漆固化铁芯高15%;纵磁退火且浸漆的Fe₈₂Si_3.8B_13.9C_0.3合金铁芯损耗低于1K101合金浸漆铁芯,且随着频率升高优势更加明显;当频率大于1000 Hz时,纵磁退火且浸漆的Fe₈₂Si_3.8B_13.9C_0.3合金铁芯的损耗值低于未浸漆铁芯。     

Improved Plasticity of Fe25Co25Ni25(Si0.3B0.7)25 High Entropy Bulk Metallic Glass through the Addition of Cu

This work was focused on enhancement in the plasticity of Fe₂₅Co₂₅Ni₂₅(Si_0.3B_0.7)₂₅ high entropy bulk metallic glass (HE-BMG) by adding minor Cu (0-1.2, in at.%). It is found that the appropriate addition of Cu can efficiently improve the plasticity of the present HE-BMG while the excessive addition of Cu will deteriorate again the plasticity, and especially, the plastic strain of the present HE-BMG is improved from 0.8% for the Cu-free alloy to 4.7% for the 0.3 at.% Cu-added alloy. The transmission electron microscopy observation shows that there are many α-Fe (Co, Ni) clusters with sizes of less than 5 nm dispersed in the glassy matrix in the 0.3 and 0.6 at.% Cu-added alloys, which may account for the significant improvement in the plasticity of the two alloys, and further increase in Cu content more than 0.9 at.% leads to the precipitation of α-Fe (Co, Ni) and Fe (Co, Ni) B compound grains with diameters of tens of nanometers, in which the plasticity of the present HE-BMGs has deteriorated rapidly.     

Microstructural evolution of Fe3B/Nd2Fe14B nanocomposite magnets microalloyed with Cu and Nb

The microalloying effect of Cu and Nb on the microstructure and magnetic properties of an Fe₃B/Nd₂Fe₁₄B nanocomposite permanent magnet has been studied by transmission electron microscopy (TEM) and atom probe field ion microscopy (APFIM). Additions of Cu are effective in refining the nanocomposite microstructure and the temperature range of the heat treatment to optimize the hard magnetic properties is significantly extended compared with that of the ternary alloy. Combined addition of Cu and Nb is further effective in reducing the grain size. Optimum magnetic properties obtained by annealing a melt-spun Nd_4.5Fe_75.8B_18.5Cu_0.2Nb₁ amorphous ribbon at 660°C for 6 min are B_r=1.25 T, H_cJ=273 kA/m and (BH)_max=125 kJ/m³. The soft magnetic Fe₂₃B₆ phase coexists with the Fe₃B and Nd₂Fe₁₄B phases in the optimum microstructure of the Cu and Nb containing quinternary alloy. Three-dimensional atom probe (3DAP) results show that the finer microstructure is due to the formation of a high number density of Cu clusters prior to the crystallization reaction, which promote the nucleation of the Fe₃B phase. The Nb atoms appear to induce the formation of the Fe₂₃B₆ phase when the remaining amorphous phase is crystallized.     

Effects of Ribbon Thickness on Structure and Soft Magnetic Properties of a High-Cu-Content FeBCuNb Nanocrystalline Alloy

The effects of ribbon thickness (t) on the structure and magnetic properties of a Fe_82.3B₁₃Cu_1.7Nb₃ alloy in melt-spun and annealed states have been investigated. Increasing the t from 15 to 23 μm changes the structure of the melt-spun ribbons from a single amorphous phase to a composite with dense α-Fe nanograins embedded in the amorphous matrix. The grain size (D_α-Fe) of the α-Fe near the free surface of the ribbon is about 6.7 nm, and it gradually decreases along the cross section toward the wheel-contacted surface. Further increasing the t to 32 μm coarsens the D_α-Fe near the free surface to 15.2 nm and aggravates the D_α-Fe ramp along the cross section. After annealing, the ribbon with t = 15 μm has relatively large α-Fe grains with D_α-Fe > 30 nm, while the thicker ribbons possessing the pre-existing nanograins form a finer nanostructure with D_α-Fe < 16 nm. The structural uniformity of the ribbon with t = 23 μm is better than that of the ribbon with t = 32 μm. The annealed ribbons with t = 23 and 32 μm possess superior soft magnetic properties to the ribbon with t = 15 μm. The ribbon with t = 23 μm exhibits a high saturation magnetic flux density of 1.68 T, low coercivity of 9.6 A/m, and high effective permeability at 1 kHz of 15,000. The ribbon with t = 32 μm has a slightly larger coercivity due to the lower structural uniformity. The formation mechanism of the fine nanostructure for the ribbons with suitable t has been discussed in terms of the competitive growth effect among the pre-existing α-Fe nanograins.     

The Minor Precipitation at the Final Stage of U720Li Solidification

The minor precipitations caused by B and Zr which are the normal constituents of U720 Li alloy have been studied by analyzing the solidification process and the composition evolution. The present study aims to supply the elementary information about the existing form of B and Zr in the as-cast microstructure, which is helpful for the subsequent processing, such as homogenization treatment. The M_3B_2 and Ni_5Zr phases were observed in the U720 Li alloy in as-cast state, which were usually accompanying with each other together with g-Ni_3 Ti phase at the edge of eutectic(γ+γ'). Combining the DTA analysis and heating and quenching tests, the solidification sequence was determined to be the following: c matrix, eutectic(γ+γ'), g-Ni_3Ti, M_3B_2 and Ni_5Zr. The in situ composition analysis by EDS and EPMA revealed that the precipitation and microstructure were governed by the composition evolution in the liquids. The solidification of c matrix increased the Ti concentration in the residual liquids and resulted in the eutectic(γ+γ') formation; the(γ+γ') formation increased the Ti/Al radio in the liquids and the g-Ni_3Ti was formed in front of the eutectic(γ+γ'); the g-Ni_3Ti precipitation consumed up Al and Ti and increased the concentration of B, Mo and Cr, and M_3B_2 boride is formed;the previous precipitation of the phases consumed up most of the elements other than Ni and Zr, and Ni_5Zr is formed finally. The melting points are in the ranges of 1130–1140 °C for Ni_5Zr phase, 1180–1190 °C for M_3B_2 boride and1190–1200 °C for g-Ni_3Ti phase.     

The role of tensides in the covering, formation and power loss properties of amorphous metallic ribbons by glassy coatings

Tensides are surface active substances which play an essential role in the formation of glassy coatings from aqueous solutions of H₃BO₃, H₃PO₄ and their salts. Firstly, they ensure the wettability of the hydrophobic metallic ribbon at the phase boundary in very low concentrations and, in addition, they adjust both specifically and effectively the reaction conditions between the depositing solution and the surface of the amorphous metallic ribbon. They penetrate into the interlayer of the ribbon changing its physico-chemical properties and in this way influence its magnetic characteristics. This paper deals with the effect of commercially produced non-ionic tensides (Slovanik NT, Slovasol EL, Slovasol O) and an anionic tenside (Slovafos 3) in the process of the formation of glassy coatings vs. power loss for amorphous Fe₈₂Si₆B₁₂, Fe₄₀Ni₄₀B₂₀ and Co₇₀Fe₅Si₇B₁₈ ribbons. The influence of different amounts of tensides in borate and phosphate deposition solutions and of heat treatment of these solutions on power loss is discussed.     

Synthesis and characterization of bulk composite Fe-Si-B alloys with small concentration of Nb and Mo

The preparation and some mechanical,thermal and magnetic properties of the as cast bulk composite Fe72B19.2Si4.8M4 (M=Nb,Mo) alloys obtained by suction casting are presented and discussed.The microstructrural results showed the existence of a crystalline α-Fe(Si) phase embedded in a glassy matrix.The values of microhardness (Hv) and yield strength (σy) for the Nb-containing alloy are exceptionally high,i.e.(12.65±0.3) GPa and (4.22±0.10) GPa,respectively.The saturation polarization values are found to be as...     

Ni合金化对Finemet合金热稳定性及软磁性能的影响

通过铜辊甩带法制备了成分为Fe_73.5-xSi_13.5B₉Cu₁Nb₃Ni_x(x=0、1、2、3)的非晶带材,并对其进行退火处理。利用XRD、DSC、VSM和软磁直流测试仪等对带材的相结构、热稳定性以及软磁性能进行测试分析。结果表明,所制备合金带材淬火态下均为完全非晶结构,经560 ℃保温60 min退火处理后,合金中形成了非晶和α-Fe(Si)纳米晶双相共存结构。随着Ni含量的增加,整体上非晶带材的一级起始晶化温度T_s1和二级起始晶化温度T_s2先减小后增大,两级起始晶化温度之差ΔT_s整体呈下降的趋势,由166.0 ℃下降至132.8 ℃,热稳定性降低。淬火态下,Ni元素的添加使得非晶带材的软磁性能有所恶化。经退火处理后,带材的软磁性能明显提升,当Ni含量x=1时,具有较好的软磁性能,其饱和磁化强度为157.7 emu/g,矫顽力为6.8 Oe。     

脉冲磁场处理Fe52Co34Hf7B6Cu1非晶的低温真空退火效应

对Fe₅₂Co₃₄Hf₇B₆Cu₁非晶合金进行了低频磁脉冲处理,研究低温真空退火对磁脉冲处理Fe_52Co₃₄Hf₇B₆Cu₁非晶软磁性能的影响.结果表明,磁脉冲处理导致非晶合金发生纳米晶化,析出晶态相α-Fe（Co）,晶粒尺寸为5-10 nm,形成的纳米晶粒弥散分布于非晶基体的双相纳米合金中.对磁脉冲处理的试样进行低温真空退火,可以进一步优化纳米合金的软磁性能,在100℃退火可以得到最佳的软磁性能.     

High permeability nano-crystalline FeSiBTaAg ribbons obtained by direct casting

Nano-crystalline soft magnetic ribbons, being extensively used as magnetic cores for switching power supplies, have been invariantly obtained by melt-spinning followed by post-annealing. Reported herewith are the attainment, by direct-casting without annealing, of nano-crystalline Fe_77.4−xSi_15.5B₇Ta_xAg_0.1 (x = 1, 2) ribbons with superior soft magnetic properties (named TAGMET after the addition of Ta and Ag). The grain size of nano-crystalline -FeSi, from 20 to 30 nm, varies with composition and quenching speeds. As-spun Fe_75.4Si_15.5B₇Ta₂Ag_0.1 ribbons consisting of 25 nm nano-crystals exhibit a saturation magnetization of 157 emu/g (1.45 T), an effective permeability of 56,000 at 1 kHz, and coercivity, 8 A/m. With the combination of easier manufacturing process and excellent soft magnetic properties, this alloy is competitive in industrial applications versus the well-known FINEMET.     

Effect of Pd additions on phase stability and hydrogen-induced internal friction of Ti34Zr11Cu47Ni8 glassy alloys

The effects of additions of Pd below 10 at.% on the stability and hydrogen-induced internal friction behavior of Ti₃₄Zr₁₁Cu₄₇Ni₈ glassy alloys have been investigated. Thermal analyses indicate that the supercooled liquid region decreases distinctly with increasing Pd content. It was found that internal friction peak temperatures of Ti₃₄Zr₁₁Cu₄₇Ni₈–Pd hydrogenated glassy alloys (HGAs) in the hydrogen content range below approximately 30 at.% H were higher than those of the original Ti₃₄Zr₁₁Cu₄₇Ni₈ HGAs, especially at hydrogen contents below 10 at.% H. It was also found that the internal friction peaks of Ti₃₄Zr₁₁Cu₄₇Ni₈–Pd HGAs increased with increasing hydrogen content below 15 at.% H, after which they tended to saturate. These results are in contrast to the effects of Si addition as previously reported. The effects of Pd are discussed from the viewpoint of the interstitial site distribution for hydrogen and local atomic structure of the glassy alloy.     

Reduced Annealing Time and Enhanced Magnetocaloric Effect of La(Fe,Al)13 Alloy by La-nonstoichiometry and Si-doping

LaFe_13-xM_x (M = Si, Al) alloys are promising for use in magnetic refrigeration. However, they require long annealing time (30 days) in order to optimize the magnetocaloric properties. Research has shown that the addition of extra La in off-stoichiometric alloys can greatly shorten the annealing time. Therefore, the purpose of this study is to investigate the influence of the extra addition of La on the annealing properties of a new off-stoichiometric La_1.7Fe_11.6Al_1.4-xSi_x (x = 0, 0.1, 0.4) alloys. It was demonstrated that after a 36h annealing time, a large volume fraction of 1:13 magnetocaloric phase was obtained for all alloys. Further microstructural analysis of the off-stoichiometric La_1.7Fe_11.6Al_1.4-xSi_x alloys revealed a facet-like grain morphology. The La_1.7Fe_11.6Al_1.4 and La_1.7Fe_11.6Al₁Si_0.4 alloys were shown to contain large 1:13 phase precipitates separated in a La-rich matrix, while the La_1.7Fe_11.6Al_1.3Si_0.1 alloy had a continuous 1:13 phase matrix with a fine dispersion of La-rich precipitates throughout. When the magnetic field varied between 0 and 2 T, the corresponding magnetic entropy change and relative cooling capacity for the La_1.7Fe_11.6Al_1.3Si_0.1 specimen were determined as 4.58 J/kg K and 173.6 J/kg, respectively. More importantly, the La_1.7Fe_11.6Al_1.3Si_0.1 alloy displayed only a slight volume change when the meta-magnetic phase transition occurred, which is promising for cyclic use.