Thermal Stability and Magnetic Properties of (Fe,Co)-Zr-Nd-B Amorphous Alloys

A new type of Fe-based amorphous alloy containing rare earth element was prepared by melt spinning technique. The glass-forming ability (GFA),thermal stability and magnetic properties were investigated in the composition range of Fe_(70)Co_8Zr_(7- x )Nd_ x B_(15) ( x =0% to 6%,atom fraction). They exhibit the glass transition and supercooled liquid region before crystallization. The width of supercooled liquid region obtained for the series of Fe_(70)Co_8Zr_(7- x )Nd_ x B_(15) exceeds (40 K,) among which the maximum width for Fe_(70)Co_8Zr_5Nd_2B_(15) amorphous alloy reaches 61 K. Another main attraction is that the selected Fe-based amorphous alloys have good soft magnetic properties. The saturation magnetization ( J _s) is in the range of 1.10 to 1.37 T,and coercive force ( H _c) in the range of 2.28 to 8.15 A·m (-1) for Fe_(70)Co_8Zr_(7- x )Nd_ x B_(15) amorphous alloys. It is found that the saturation magnetization ( J _s) increases with the increment of the relative content of the Nd for the Fe_(70)Co_8Zr_(7- x )Nd_ x B_(15) alloys. The H _c values for the glasses with Nd content of 1%,2% and 3% are below 3 A·m (-1). The research indicates that Fe_(70)Co_8Zr_5Nd_2B_(15) amorphous alloy has good high GFA and good soft magnetic properties,of which the width of supercooled liquid region,J _s,and H _c are 61 K,1.25 T and 2.28 A·m (-1),respectively.

Effect of Al Addition on the Glass-Forming Ability and Magnetic Properties of a Gd-Co Binary Amorphous Alloy

The glass-forming ability （CFA） and magnetic properties of the Cd50 Co50-based amorphous alloy with AI addition substitution for Co are investigated. It is found that the CFA and magneto-caloric effect of the Gd50Co45Al5 amorphous alloy are better than Cd50Co50 amorphous alloy. The maximum magnetic entropy change （-△ Sm^peak） and the magnetic refrigerant capacity- of the amorphous alloy under a field of 5 T are about 6.64 J·kg^-1 K^-1 and 764 J·kg^-1, respectively. The field dependence of magnetic entropy change meets the one predicted by the mean field theory, which is investigated for a better understanding of the magneto-caloric behaviors of the Gdso Co45Al5 amorphous alloy.

Crystalline Behavior and Magnetic Properties of Nd_(60) Fe_(30-x)Al_(10)Co_x (x=0,5,10) Bulk Amorphous Alloys

Crystalline behavior and magnetic properties of Nd 60 Fe 30- x Al 10 Co x (x =0,5,10) bulk amorphous alloys were investigated by differential scanning calorimeter (DSC), X ray diffraction (XRD) and the vibrating sample magnetometer (VSM). Neither glass transition nor supercooled liquid region before crystallization was observed for the as cast Nd 60 Fe 30- x Al 10 Co x (x =0,5,10) bulk amorphous alloys. The glass forming ability can be improved significantly by the addition of Co. The as cast Nd 60 Fe 30- x Al 10 Co x (x =0,5,10) alloys show hard magnetic behavior. With the addition of Co content, intrinsic coercivity ( i H c) increases while the saturation magnetization( σ s) and remanence ( σ r) decrease. The Curie temperature for the as cast Nd 60 Fe 30- x Al 10 Co x alloys increases from 451 K for x =0 to 468 K for x =10. Some precipitation of crystalline phases does not affect the hard magnetic properties of Nd 60 Fe 30- x Al 10 Co x (x =0,5,10) alloys, while the hard magnetic behavior disappears quickly after the alloys being completely crystallized.

Study of structural and magnetic properties of Fe(80)P-9B(11) amorphous alloy by ab initio molecular dynamic simulation

The structural and magnetic properties of Fe80P9B11 amorphous alloy are investigated through ab initio molecular dynamic simulation. The structure evolution of Fe（80）P9B（11） amorphous alloy can be described in the framework of topological fluctuation theory, and the fluctuation of atomic hydrostatic stress gradually decreases upon cooling. The left sub peak of the second peak of Fe–B partial pair distribution functions（PDFs） becomes pronounced below the glass transition temperature, which may be the major reason why B promotes the glass formation ability significantly. The magnetization mainly originates from Fe 3d states, while small contribution results from metalloid elements P and B. This work may be helpful for developing Fe-based metallic glasses with both high saturation flux density and glass formation ability.

Influence of Metalloid Elements on the Magnetic Properties and Anisotropy of FeNi-based Amorphous Alloys

The magnetic properties and anisotropy of amor- phous(Fe_(80)Ni_(20))_(78)Si_xB_(22-x).alloys have been investigated systematically.The maximum permeability,coercive force and remanence have been determined for as-prepared and annealed samples,The results on the technical magnetic properties of this alloy system have been discussed and compared with Masumoto's.

High-pressure sintering and magnetic properties of Fe_(86)Zr_(11-x)Nb_xB_3(x=5.5, 6) amorphous alloys

The thermal stability of milling Fe86Zr11-xNbxB3（x=5.5, 6） melt-spun strip powders and the influence of high-pressure sintering conditions on phase component and grain size of bulk alloys were investigated by X-ray diffractometry（XRD）, differential scanning calorimetry（DSC） and scanning electron microscopy（SEM）. The results show that milling melt-spun powder remains in the amorphous state, and the crystallization temperature of which is 480530℃, the apparent activation energy Ep of crystallization process is 294.1219.5kJ/mol. The increasing Nb content can increase crystallization temperature and decrease Ep. Under the sintering conditions of 5.5GPa/3min, when Pw is 1150W, single phase α-Fe nanocrystalline （20.626.7nm） bulk alloy with relative density higher than 99.0% can be obtained. Under the sintering conditions of 5.5GPa/1150W/3min, the magnetic properties of these nanocrystalline bulk alloys are Fe86Zr5.5Nb5.5B3 alloy, Bs=1.15T, Hc=5.08kA·m-1; Fe86Zr5Nb6B3 alloy, Bs=1.26T, Hc=4.27kA·m-1.

Influence of heat treatment on high frequency soft magnetic properties of Finemet amorphous alloy

In order to study high-frequency soft magnetic properties of Finemet amorphous alloy,the microstructural change and nanocrystallization under different heat treatment conditions were investigated by XRD and TEM. The crystallite size of α-Fe was calculated from the XRD pattern using the Scherrer formula,while the high frequency magnetic properties were measured at room temperature by TPS-200SA exchange tester. The results of XRD and TEM indicate that the nanocrystallization occurs at 500 ℃. When the annealing temperature increases to 560 ℃,the amorphous alloy becomes totally nanocrystallized and the crystallites distribute homogeneously,thus an excellent combination of soft magnetic properties is obtained.

Effect of Y element on atomic structure, glass forming ability,and magnetic properties of FeBC alloy

The atomic structure of amorphous alloys plays a crucial role in determining both their glass-forming ability and magnetic properties. In this study, we investigate the influence of adding the Y element on the glass-forming ability and magnetic properties of Fe_(86-x)Y_xB_7C_7(x = 0, 5, 10 at.%) amorphous alloys via both experiments and ab initio molecular dynamics simulations. Furthermore, we explore the correlation between local atomic structures and properties. Our results demonstrate that an increased Y content in the alloys leads to a higher proportion of icosahedral clusters, which can potentially enhance both glass-forming ability and thermal stability. These findings have been experimentally validated. The analysis of the electron energy density and magnetic moment of the alloy reveals that the addition of Y leads to hybridization between Y-4d and Fe-3d orbitals, resulting in a reduction in ferromagnetic coupling between Fe atoms. This subsequently reduces the magnetic moment of Fe atoms as well as the total magnetic moment of the system, which is consistent with experimental results. The results could help understand the relationship between atomic structure and magnetic property,and providing valuable insights for enhancing the performance of metallic glasses in industrial applications.

Effect of Zr on Microstructure and Magnetic Properties of Nanocrystalline (Nd, Pr)FeB/α-Fe Composite Alloys

For nanophase (Nd, Pr)FeB/α-Fe composite alloys were prepared by melt spinning, the appreciable addition of Zr reduces their average grain size. Observed by atom force microscopy (AFM), the average grain diameter of crystallized ribbons on their free surface, reduces from 175 nm of Zr-free alloy to 79 nm of Zr-1at%, by about 55%. If the concentration exceeds 1%, the effects of Zr on fining grain size are evidently weakened. The average grain size on free surface of Zr-1.5at% is 72 nm. With the addition of 1at% Zn, the bonded magnets has the best combination of properties: B_r=0.675 T, H_(ci)=616 kA·m^(-1), (BH)_(max)=77 kJ·m^(-3). Below 1at%, the coarser grains lead to a lower magnetic property. Beyond 1at%, the layer of Zr-rich intergranular phase will thicken, which results in weakening of the exchange coupling among adjacent grains, and then causes degrading of magnetic properties of magnets.

EFFECT OF HYDROGEN ABSORPTION ON MAGNETIC PROPERTIES OF AMORPHOUS Fe_(90-x) V_x Zr_(10) ALLOYS

The amorphous Fe_(90-x)V_xZr_(10) alloy after electolytic hydrogenation procedure was studied by means of Mossbauer effect,magnetic measurement.X-ray diffaction and secondary ion mass spectroscopy(SIMS)techniques.The experimental results show that the magnetic properties of amorphous Fe_(90-x)V_xZr_(10) alloy are highly sensitive to the presence of hydrogen. The isomer shift(IS)has a small positive change and the magnetic properties transfer from paramagnetic to ferromagnetic State by hydrogenation,and the effect of hydrogen absorption is to raise Fe magnetic moment(from the increase of saturation maguetization)and Curie temperature T_c from 257 to 384 K.Finally.the considerable increase of magnetic properttes of amorphous Fe_(90-x)V_xZr_(10) alloy by hydrogenation is attributable to the change of hybridization effect between outer electrons of Zr atoms and 3d electrons of Fe atoms.From the results of SIMS experiment,it is concluded that the hydrogen atoms is localized around Zr atoms wheh hydrogen atoms enter into the allor.

CRYSTALLIZATION AND MAGNETIC PROPERTIES OF AMORPHOUS Nd_6Fe_(81)B_(13)ALLOY

The magnetic properties and the crystallization and its influence on the magnetic and struc- tural properties for rapidly quenched amorphous Nd_6Fe_(81)B-(13) alloy have been studied.The low temperature magnetic properties,the Curie temperature and the crystallization behavior are discussed.A small addition(6at.-%)of Nd in amorphous Fe-B alloys increases largely the crystallization temperature T_x but causes a decrease of the Curie temperature Tc·A new phase was observed in the sample annealed at 873 K.

Surface Structure and High-frequency Magnetic Properties of the Amorphous [Co_(0.94-x)Fe_(0.06)(MoMn)_x]_(77)(SiB)_(23) Alloys

The relationship between the high-frequency magnetic properties and surface structure of the amorphous [Co_(0.94-x)Fe_(0.06)(MnMo)_x]_(77)(SiB)_(23) alloys annealed at 400-500℃ then control-cooled was investigated using XRD,TEM and XPS techniques.The results have shown that the high-frequency losses of the present alloys ob- viously reduced after suitable treatment.A crystalline layer with ultrafine grains of γ-Co formed on the surface of the amorphous ribbons.The size of the grains is 10-20 nm.The thickness of the layer is less than 0.1 μm.The sur- face of the crystalline layer is covered with an extremely thin oxide film which is very uniform and dense with thickness of less than 30 nm,the size of grains of the oxide is less than 10 nm.These ultrafine grains and the dense oxide film effectively refine the magnetic domains and increase the resistance of the layers of the magnetic core,consequently the losses at high frequency are fairly reduced.

Formation of L1_(0)-FeNi hard magnetic material from FeNi-based amorphous alloys

L1_(0)-FeNi hard magnetic alloy with coercivity reaching 861 Oe was synthesized through annealing Fe_(42)Ni_(41.3)Si_8 B_(4)P_(4)Cu_(0.7)amorphous alloy,and the L1_(0)-FeNi formation mechanism has been studied.It is found the L1_(0)-FeNi in annealed samples at 400℃mainly originated from the residual amorphous phase during the second stage of crystallization which could take place over 600 C lower than the measured onset temperature of the second stage with a50 C/min heating rate.Annealing at 4000 C after fully crystallization still caused a slight increase of coercivity,which was probably contributed by the limited transformation from other high temperature crystalline phases towards L1_(0)phase,or the removal of B from L1_(0)lattice and improvement of the ordering quality of L1_(0)phase due to the reduced temperature from520℃to 400℃.The first stage of crystallization has hardly direct contribution to L1_(0)-FeNi formation.Ab initio simulations show that the addition of Si or Co in L1_(0)-FeNi has the effect of enhancing the thermal stability of L1_(0)phase without seriously deteriorating its magnetic hardness.The non-monotonic feature of direction dependent coercivity in ribbon segments resulted from the combination of domain wall pinning and demagnetization effects.The approaches of synthesizing L1_(0)-FeNi magnets by adding Si or Co and decreasing the onset crystallization temperature have been discussed in detail.

Influence of Zr Additions on Microstructure and Magnetic Properties of Nanocomposite Nd_(10.5)Fe_(78-x)Co_5Zr_xB_(6.5) (x=0～5) Alloys

The influence of Zr addition on the microstructure and magnetic properties of nanocomposite Nd_(10.5)Fe_(78-x)Co_5Zr_xB_(6.5) (x=0～5) alloys was investigated. It was found that the intrinsic coercivity could be significantly improved by the addition of 2% (atom fraction) Zr. The presence of small amount of amorphous phase is responsible for the low intrinsic coercivity for Zr-free alloy. The small amount addition of Zr may suppress the growth of grains of α-Fe and Nd_2Fe_(14)B phases. The more homogeneous microstructure with an average grain size of 20 nm can be obtained for Nd_(10.5)Fe_(76)Co_5Zr_2B_(6.5) alloy.

Structure and magnetic properties of mechanically alloyed Tb_(0.2)Pr_(0.8)(Fe_(0.4)Co_(0.6))_(1.93) and magnetostriction of its epoxy composite

The C15 Laves phase with composition Tb0.2Pr0.8（Fe0.4Co0.6）1.93 was synthesized by mechanical alloying （MA） and subsequent annealing process. The structure and magnetic properties of Tb0.2Pr0.8（Fe0.4Co0.6）1.93 were investigated by means of X-ray diffraction （XRD）, a vibrating sample magnetometer, and a standard strain technique. The effect of annealing on the structure and magnetic properties was studied. The analysis of XRD shows that the high Pr-content Tb0.2Pr0.8（Fe0.4Co0.6）1.93 alloy with the single phase of MgCu2-type structure can be successfully synthesized by MA method. The sample annealed at 450℃ is found to have a coercivity of 196 kA/m at room temperature. An epoxy/Tb0.2Pr0.8（Fe0.4Co0.6）1.93 composite was produced by a cold isostatic pressing technique. A large magnetostriction of 400 ppm, at an applied magnetic field of 800 kA/m, was found for the composite. The epoxy-bonded Tb0.2Pr0.8（Fe0.4Co0.6）1.93 composite combines a high magnetostriction with a significant coercivitv, which is a oromising magnetostrictive material.

Effects of the Composition of Electrodeposited Fe-Ni-P Alloy on the Thermostability and Magnetic Properties

The magnetic properties, structure defects of electrodeposited Fe-Ni-P alloys with various compositions and the thermostability at amorphous state have been studied by DSC, positron annihilation and electronic integrating instrument methods. The results show that the thermostability of amorphous Fe-Ni-P alloys increases with Fe content. Emergence and recrystallization of stable phases defer as the P content of the coating increases. The minimum H-c, B-r and P-h occur at 9.4 P (wt pet) content. Maximum H-c, B-r and P-h occur at the weight ratio of Fe to Ni equaling to 1/9.

Formation and properties of high Fe-content Fe-(B-Si)-Zr bulk amorphous alloys

The present work is devoted to the development of Fe-（B-Si）-Zr amorphous alloys with high glass-forming ability and good magnetic properties. Using the cluster-plus-glue-atom model proposed for ideal amorphous structures, [FeFe11B3Si]（Fe1-xZrx） was determined as the cluster formula of Fe-（B-Si）-Zr alloys. The glass formation and thermal stability of the serial alloys, namely, [FeFel^B3Si]（Fel_xZrx） （x = 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.75, and 1.0）, were studied by the combination of copper mold casting, X-ray diffraction, and differential thermal analysis techniques. The maxima of glass-forming ability and thermal stability were found to occur at the compositions of [FeFe11B3Si] （Fe0.6Zr0.4） and [FeFe11B3Si]（Fe0.5Zr0.5）. The alloys can be cast into amorphous rods with 1.5 ram diameter, and upon reheating, the amorphous alloys exhibit a large undercooled liquid span of 37 K. The saturation magnetization of the [FeFe11B3Si]（Fe0.5Zr0.5） amorphous alloy was measured to be 1.4 T.

Structural and magnetic properties of Sm_2Fe_(17-x)Nb_x (x = 0-4) alloys prepared by HDDR processes and their nitrides

Sm2Fe17-xNbx （x = 0-4） powder was synthesized by HDDR treatment and nitrogenation. The effects of partial Nb substitution for Fe on the structural and magnetic properties of Sm2Fe17-xNbx alloys and their nitlides were investigated. It was seen that Sm2（Fe,Nb）17 phase exists in both annealed and HDDR-treated Sm2Fe17-xNbx alloys. However, its content is decreased with the increase in Nb substitution. In annealed alloys, Sm2（Fe,Nb）17 phase becomes unstable and will dissociate into SmFe2 and Fe-rich phases when x 〉 1.5. With HDDR-treatment, the Nb concentration in recombined Sm2（Fe,Nb）17 phase is decreased, and the content of Fe-rich phases is increased. Sm2Fe17-xNbx powder exhibits dendritic cracks and fine particles with a size of less than 300 nm. In nitrogenated alloys, N atoms mainly enter 2：17-type phase to form Sm2（Fe,Nb）17Ny. Partial Nb atoms in Sm2（Fe,Nb）17Ny phase will be released or excluded by nitrogen atoms. Fe-rich phases increase, and are followed by the amorphous Sm2（Fe,Nb）17Ny phase. Nb substitution for Fe with x = 0.5 and 1.0 in Sm2Fe17-xNbxNy powders increases the coercivity and remanence. But when x is greater than 2.0, Nb substitution will deteriorate the magnetic properties.

Effects of Sm content on crystallized structure and magnetic properties of Co80-xSmxb20 amorphous alloys

The formation,thermal stability,crystallized structure,and magnetic properties of melt-spun Co80-xSmxB20(x=0–20)amorphous alloys have been investigated.A single amorphous phase is formed for the alloys with x=0–15.The first crystallization temperature gradually increases from 670 to 955 K as x increases from 0 to 10,and decreases to 836K when x=15.After optimum annealing,the nanocomposite structure consisting of SmCo12B6+fcc-Co+Sm2Co17 phases is formed for the alloys with x=5 and 7.5,and SmCo12B6+Sm2Co17+SmCo3,SmCo12B6+Sm2Co17+SmCo4B,and SmCo12B6+SmCo4B phases are formed for the alloys with x=10,12.5,and 15,respectively.The coercivity of the annealed alloys increases remarkably from 103.5 to 1249.4 kA m^-1 as x increases from 5 to 15,while the magnetization at the applied field of 2.0T decreases from 0.51 to 0.16T.The improved magnetic hardness with rising Sm content is attributed to the formation of the hard magnetic phases with higher magnetocrystalline anisotropy and the increase in their volume fraction.

Amorphization and magnetic properties of Fe_(62)Nb_(38) mechanically alloyed powders

The amorphization and magnetic properties of Fe_(62)Nb_(38) mechanicallyalloyed powders were investigated. In the initial mechanical alloying processes, the latticestructure of pure Fe is destroyed due to the cold-welding and fracturing, accompanying the reductionof ferromagnetic properties. The M_S value of Fe_(62)Nb_(38) powders with ball-milling time t = 6 his only 48.1 A·m^2/kg. With prolongating of mechanical alloying processes, a solid stateamorphization reaction (SSAR) takes place and the Fe-Nb ferromagnetic amorphous phase is formed.With the milling time increasing from 6 to 18 h, the saturation magnetization of Fe_(62)Nb_(38)powders increases with enhancement of the proportion of ferromagnetic amorphous phase in milledpowders. The M_S value of the Fe_(62)Nb_(38) amorphous powders is 98 A·m^2/kg, which is very closeto the value estimated from dilute model. However, the Curie temperature of the Fe_(62)Nb_(38)amorphous phase is only 206℃, which is much smaller than that of the pure Fe. This implies that theexchange interaction between Fe atoms in amorphous alloyed Fe_(62)Nb_(38) becomes weak due to theNb dilution. Investigation shows that the variation of magnetic properties of milled powders is oneof important tools for describing the amorphization by mechanical alloying.