保护气氛对Fe80Si9B11非晶带材表面特征及磁性能的影响

非晶合金带材的表面特征对磁性能有着重要的影响。为研究CO保护气氛对Fe₈₀Si₉B₁₁非晶带材表面鱼鳞纹的形成及非晶合金带材磁性能的影响规律,本文采用平面流铸法制备了Fe₈₀Si₉B₁₁非晶合金带材,利用金相显微镜、X射线衍射仪和磁性能测试仪研究了熔潭保护气体CO流量对非晶合金带材表面特征、微观结构及磁性能的影响。研究表明,不同CO流量条件下制备的合金带材均为非晶态,且CO流量对带材厚度几乎无影响;随CO流量增大,熔潭周围气体密度和气压降低,熔潭稳定性增强,裹入熔潭的气体变少,带材贴辊面气泡尺寸变小且数量减少,带材表面的鱼鳞纹间距增大。当CO流量为0时,带材表面比较粗糙,观察不到鱼鳞纹;当CO流量为0.25和0.5 m³/h时,带材表面鱼鳞纹间距分别为1.5、2.3 mm。随CO流量增大,由于气泡对畴壁的钉扎和鱼鳞纹细化磁畴的协同作用,使带材矫顽力和铁损降低,振幅磁导率增大;磁损耗分离结果表明,随CO流量增大,磁滞损耗降低,涡流损耗增大,且铁损降低主要由磁滞损耗降低引起的。     

Soft magnetic amorphous Fe–Zr–Si(Cu) boron-free alloys

Amorphous Fe₈₀Zr_xSi_20−x−yCu_y boron-free alloys, in which boron was completely replaced by silicon as a glass forming element, have been prepared in the form of ribbons by using the melt quenching technique. X-ray diffraction and Mössbauer spectroscopy measurements revealed that the as-quenched ribbons with the compositions with x = 6–10 at.% and y = 0, 1 at.% are fully or predominantly amorphous. Differential scanning calorimetry (DSC) measurements allowed the estimation of crystallization temperatures of the amorphous alloys. Soft magnetic properties have been studied by the specialized rf-Mössbauer technique. Since the rf-collapse effect observed is very sensitive to the local anisotropy fields it was possible to evaluate the soft magnetic properties of the amorphous alloys studied. The rf-Mössbauer studies were accompanied by conventional measurements of hysteresis loops from which the magnetization and coercive fields were estimated. It was found that amorphous Fe–Zr–Si(Cu) alloys are magnetically very soft, comparable with those of the conventional amorphous B-containing Fe-based alloys.     

Nanocrystallization of amorphous CoSiBFeNb alloys

The effect of Fe and Nb contents on the crystallization behavior of CoSiBFeNb alloys was studied using Mössbauer spectroscopy, transmission electron microscopy and X-ray diffraction. It was found that the structure formed by primary crystallization in the (Co₇₇Si_13.5B_9.5)₈₈Fe₇Nb₅ alloy is similar to that of the famous Fe_73.5Si_1.35B₉Cu₁Nb₃ nanocrystalline alloy. The data obtained are discussed regarding a random network of associates as a base structural element of amorphous metallic alloys.     

Effects of elemental additions and superheat on melt surface tension and metallic glass embrittlement

Additions of antimony, selenium, tellurium and some other alloying elements to iron-nickel base alloys have been investigated with regard to effects on melt surface tension and resultant metallic glass formation and characteristics. Surface tension of the molten alloys has been measured as a function of composition and melt temperature using a variation of the maximum bubble pressure method. The density of molten Fe₄₀Ni₄₀B₂₀ alloy has been measured as a function of temperature. Attempts to chill block melt-spin and alloys of the present investigation into metallic glass ribbons were largely successful. A few compositions were partially crystalline in the as-cast state and even fewer were not castable at all. The amorphous structure of ribbons made was assessed by X-ray diffraction, differential scanning calorimetry, and embrittlement temperatures for one hour anneals. A correlation has been established between changes in melt surface tension and metallic glass embrittlement temperature with the addition of surface active elements.     

Ball milling of Co70 Fe8Si9B13 amorphous ribbon,crystallized ribbon and a mixture of pure crystalline powders

Co₇₀ Fe₈ Si₉B₁₃ amorphous ribbon, crystallized ribbon and a mixture of pure crystalline powders were mechanically alloyed by milling and nanocrystalline structures were obtained. The structural changes were monitored By X-ray diffraction and differential scanning calorimetry measurements. The thermal behaviour on heating the alloys prepared by ball milling was studied and the influence of the high-energy ball milling on the resulting phases was found.     

Comparative Study of the Crystallization Behavior of Fe-Cr-B-Si in Bulk and Thin Film Forms

A pulsed laser deposition technique was used to obtain Fe-Cr-B-Si metallic glass in a thin film form using the amorphous Fe₇₇Cr₂B₁₆Si₅ ribbon as a target. Subsequently the as-deposited films were annealed at the same conditions as the ribbon samples in order to compare their crystallization behaviors. The structure and magnetic properties of the bulk and the surface layer of the samples were characterized by transmission and conversion electron Mössbauer spectroscopy, respectively. Significantly different crystallization behavior was observed for the ribbon and thin film samples.     

Crystallization behaviour and mechanical properties of rapidly solidified Al<Subscript>87.5</Subscript>Ni<Subscript>7</Subscript>Mm<Subscript>5</Subscript>Fe<Subscript>0.5</Subscript> amorphous alloy

The crystallization behaviour and the mechanical properties of rapidly solidified Al_87.5Ni₇Mm₅Fe_0.5 alloy ribbons have been examined in both as-melt-spun and heat-treated condition using differential scanning calorimetry, X-ray diffractometry (XRD), transmission electron microscopy (TEM), tensile testing and Vicker’s microhardness machine. XRD and TEM studies revealed that the as-melt-spun ribbons are fully amorphous. The amorphous ribbon undergoes three-stage crystallization process upon heating. Primary crystallization resulted in the formation of fine nanocrystalline fcc-Al particles embedded in the amorphous matrix. The second and third crystallization stages correspond to the precipitation of Al₁₁(La,Ce)₃ and Al₃Ni phases, respectively. Microhardness and tensile strength of the ribbons were examined with the variation of temperature and subsequently correlated with the evolved structure. Initially, the microhardness of the ribbon increases with temperature followed by a sharp drop in hardness owing to the decomposition of amorphous matrix that leads to formation of intermetallic compounds     

Enhancement of the giant magnetoimpedance effect and its magnetic response in ion-irradiated magnetic amorphous ribbons

The influences of N and Xe ion irradiation on the giant magnetoimpedance (GMI) effect and its magnetic response in Co₆₉Fe_4.5Al_1.5Si₁₀B₁₅ amorphous ribbons were systematically investigated. A large enhancement of the GMI effect and its magnetic response were achieved in N and Xe ion-irradiated amorphous ribbons. At a frequency of 3 MHz, the GMI ratio and magnetic response for an N-ion-irradiated amorphous ribbon respectively reached the highest values of 130% and 13%/Oe, while for a non-irradiated amorphous ribbon they were only about 53% and 8%/Oe. The enhancement of the GMI effect and magnetic response in the ion-irradiated amorphous ribbons resulted from the enhancement of the permeability due to rotational magnetization. Our studies indicate that low energy ion irradiation is useful for improving the magnetic softness, GMI and magnetic response of amorphous alloys, which is of practical importance for the development of high-performance magnetic sensors.     

Effect of low-temperature annealing and deformation on the structure of metallic glasses by X-ray diffraction

The changes in the atomic structure of amorphous Pd-Si and Ni-P alloys due to low-temperature annealing, cold-rolling and isothermal creep have been studied by the conventional X-ray diffraction. The present results on the effect of low-temperature annealing were consistent with those of amorphous Fe₄₀Ni₄₀P₁₄B₆ alloy studied by the energy dispersive X-ray diffraction method. In addition, the present results have indicated that the effect of cold-rolling causes small changes in the structure of amorphous Pd₈₀Si₂₀ alloy which are qualitatively different from the structural relaxation, and the effect of annealing plays a significant contribution in the structural change during an isothermal creep test.     

Electrochemical behavior of partially crystallized amorphous Al86Ni9La5 alloys

The Al₈₆Ni₉La₅ amorphous ribbons were annealed at 503 K for different time to obtain partially crystallized alloys with the different volume fractions of α-Al phase, and the effect of the crystallization extent on the electrochemical behavior of the ribbon was investigated in 0.01 M NaCl solution. The results show that the corrosion resistance of the partially crystallized ribbons is higher than that of the as-spun ribbon with the fully amorphous structure, and the corrosion resistance of the partially crystallized alloy is strongly dependent on the volume fraction of α-Al phase. The partially crystallized ribbon containing about 20 vol% α-Al phase exhibits the highest corrosion resistance.     

Investigation of Magnetic and Structural Properties of Amorphous Alloys Irradiated by Nd:YAG Laser

Amorphous metallic alloys (AMAS) have found wide application in various fields. Laser is used to modify materials. In this work, we have prepared an amorphous metallic alloy with composition Fe₇₇Co₂₁Si₂ using the melt spinning method. The prepared specimens have irradiated by a Nd:YAG laser at 1064?nm, with various fluences to investigate the corresponding induced change. The structures of specimens are verified by X-ray diffraction (XRD) before and after laser irradiated. Then magnetic parameters are measured using a vibrating sample magnetometer. Morphology reference and laser treated samples are investigated by the scanning electron microscope (SEM). The use of laser beam of relatively low energy, but with a subsequent overlapping of heated areas, resulted in a much more homogeneous structure in the heated areas of the ribbon. These measurements show that initially the magnetic properties are altered due to laser processing. The surface alteration was being simultaneously monitored by laser induced breakdown spectroscopy (LIBS).     

Comparison of Fe-Ni based alloys prepared by ball milling and rapid solidification

Mechanical alloying (MA) and rapid solidification (RS) are two important routes to obtain amorphous alloys. An Fe-Ni based metal-metalloid alloy (Fe₅₀Ni₃₀P₁₄Si₆) prepared by these two different processing routes was studied by differential scanning calorimetry, scanning electron microscopy with microanalysis, inductive coupled plasma, X-ray diffraction (XRD) and transmission Mössbauer spectroscopy (TMS). The results were compared with that obtained from other Fe-Ni based alloys of similar compositions. The structural analyses show that the materials obtained by mechanical alloying are not completely disordered after 40 h of milling whereas fully amorphous alloys were obtained by rapid solidification. TMS analyses show that, independent of the composition, after milling for 40 h, about 7% of the Fe remains unreacted. Furthermore, the thermal stability of mechanically alloyed samples is lower than that of the analogous material prepared by rapid solidification. In the MA alloys, a broad exothermic process associated to structural relaxation begins at low temperature. XRD patterns of crystallized alloys indicate that the crystallization products are bcc(Fe,Ni), fcc(Ni,Fe), and (Fe,Ni)-phosphides and -silicides.     

Studies on crystallization behaviour and mechanical properties of Al-Ni-La metallic glasses

Alloy ingots with nominal composition, Al_92−x Ni₈La _x (x = 4 to 6) and Al_94−x Ni₆La _x (x = 6, 7), were prepared by induction melting in a purified Ar atmosphere. Each ingot was inductively re-melted and rapidly solidified ribbons were obtained by ejecting the melt onto a rotating copper wheel in an argon atmosphere. The crystallization behaviour of melt-spun amorphous ribbon was investigated by means of differential scanning calorimetry (DSC), X-ray diffractometry and transmission electron microscopy. DSC showed that Al₈₆Ni₈La₆ alloy undergoes a three-stage and rest of the alloys undergo a two-stage crystallization process upon heating. The phases responsible for each stage of crystallization were identified. During the first crystallization stage fcc-Al precipitates for low La-containing alloys and for higher La-containing alloys a bcc metastable phase precipitates. The second crystallization stage is due to formation of intermetallic compounds along with fcc-Al. Microhardness of all the ribbons was examined at different temperatures and correlated with structural evolutions. Precipitation strengthening of nano-size fcc-Al is responsible for maximum hardness in these annealed alloys.     

Fabrication of bulk amorphous Fe67Co9.5Nd3Dy0.5B20 alloy by hot extrusion of ribbon and study of the magnetic properties

We report on the preparation of bulk amorphous Fe₆₇Co_9.5Nd₃Dy_0.5B₂₀ by hot extrusion of melt-spun ribbons. X-ray diffraction studies were performed to check the structure of the as-spun ribbons and the consolidated bulk specimens. Differential scanning calorimetry (DSC) analysis of the amorphous ribbons revealed that crystallization proceeds in two stages. The first crystallization step leads to the formation of soft magnetic α-(FeCo) and (FeCo)₃B and the second crystallization step corresponds to the formation of the hard magnetic (NdDy)₂(FeCo)₁₄B phase. The hysteresis loop of the as-spun ribbon reveals soft magnetic properties which change to hard magnetic behavior with enhanced remanence after annealing at 973 K for 7 min. X-ray diffraction analysis proves the presence of both soft and hard magnetic phases in the annealed sample. The viscosity of the powder obtained from crushed ribbons was investigated by parallel plate rheometry, showing a distinct viscosity drop in the supercooled liquid region that allows for easy consolidation of the crushed ribbons. The hot extruded sample that was subsequently annealed at 973 K for 7 min exhibits good hard magnetic properties with coercivity H_c = 218 kA/m, saturation magnetization J_s = 1.36 T, maximum energy product (BH)_max = 91.3 kJ/m³ and remanence B_r = 1.18 T (after demagnetization field correction), respectively.     

Effect of transition metal (TM) on the crystallization and the magnetic properties of Fe<Subscript>62</Subscript>Co<Subscript>10</Subscript>Si<Subscript>10</Subscript>B<Subscript>13</Subscript>Nb<Subscript>4</Subscript>TM<Subscript>1 </Subscript>melt-spun ribbons

Crystallization and magnetic behavior of melt-spun Fe₆₂Co₁₀Si₁₀B₁₃Nb₄TM₁ amorphous ribbon where TM = Ni, Cr, V, Pd, Pt, Ti, Ta and Zr were examined. The alloy with Pt as transition metal showed the lowest crystallization temperature of 823 K among the studied alloys. Significant increase in crystallization temperature was observed when the atomic radius of the substituted transition metal was varied from that of Pt. High Curie temperature and high saturation magnetization were recognized for the alloys containing Pd, Pt or Ti. The amorphous alloys except the alloys containing Ti or V showed good soft magnetic properties.     

On the glass-forming ability of Ni–P binary alloys

The composition dependence of glass-forming ability (GFA) of Ni–P binary alloys was systematically examined by fabricating ribbons of different thicknesses, and the microhardness of the glassy ribbon was measured. The eutectic alloy Ni_80.4P_19.6 has the best GFA and the highest microhardness in glassy state. As the alloy composition is deviated from the eutectic composition, both GFA and microhardness decrease, accompanied with an increasing full width at half maximum of the main broad peak in the X-ray diffraction spectrum of the glassy ribbon. All these results indicate a close correlation among microstructure, GFA and microhardness for the metallic glass.     

Thermal stability of amorphous phases in vapour-deposited binary alloy thin films of palladium with vanadium,niobium and tantalum

Binary alloys of the systems V-Pd, Nb-Pd and Ta-Pd were vapour deposited and investigated by transmission electron microscopy. The atomic fraction,x, was varied in steps of 0.1 from one pure element to the other. The range over which an amorphous phase is observed is found to increase in width going from 3d to 5d alloying element in palladium: the compositions where amorphous phases are found are V_1–x Pd _x (x = 0.5), Nb_1–x Pd _x (x = 0.4 to 0.6) and Ta_1–x Pd _x (x = 0.2 to 0.6). The composition range over which a crystalline phase is found correlates well with the single-phase solid solution region close to the melting temperature in the phase diagram. Crystallization of the V_0.5Pd_0.5 alloy takes place at 550 K. The amorphous Nb_1–x Pd _x (x = 0.4, 0.5) films crystallize at 850 K, whereas the amorphous Ta-Pd films crystallize between 850 and 1050K, depending on the composition. For Nb_1–x Pd _x (x = 0.4 to 0.5) and Ta_1–tx Pd _x (x = 0.2 to 0.6) primary crystallization takes place into an f c c phase. The second crystallization step leads to a phase with a complex structure. The result is a two-phase system. V_0.5Pd_0.5 and Nb_0.4Pd_0.6 crystallize polymorphically to an f c c solid solution. The crystallization temperatures for the compositions which display primary crystallization are higher than for the compositions which crystallize by a polymorphic reaction.     

Comparative study on sintering behavior of Al86Ni6Y4.5Co2La1.5 mechanically alloyed amorphous powder and melt-spun ribbon

In this research work, the sintering characteristics of Al₈₆Ni₆Y_4.5Co₂La_1.5 mechanically alloyed amorphous powders and milled melt spun ribbon have been compared. Mechanically alloyed amorphous powders were synthesized via 200?h high energy ball milling. Melt spun ribbons were synthesized by single roller melt spinning technique and grounded to powder form by ball milling. Mechanically induced partial crystallization occurred in the ribbons during milling. Significantly higher amount of contaminations such as carbon, oxygen and iron were observed in the mechanically alloyed amorphous powders compared to the milled ribbons. Both powders were consolidated via spark plasma sintering. Superior particle bonding was found in the sample consolidated from milled ribbons, ascribed to the lower amount of contamination that could not effectively restrict the viscous flow and diffusion of atoms. Various complex crystalline phases evolved in the sample consolidated from milled ribbon particles due to the presence of crystalline phases in the powders which acted as nucleation sites, whereas the amorphous phase was mostly retained in its counterpart. Vickers microhardness of the consolidated alloys from milled ribbon and mechanically alloyed amorphous powders were 3.60?±?0.13?GPa and 2.53?±?0.09?GPa, respectively. The higher hardness in the former case was attributed to the superior particle bonding and distribution of hard intermetallic phases in the amorphous matrix.     

Preparation and properties of iron-boron metallic glass ribbons melt spun in air

The preparation of metallic glass ribbons by melt spinning is a simple technique; however, a researcher often faces many problems when undertaking the preparation of such ribbons. The difficulties encountered are oxidation of the melt, choking of the nozzle by the solidified metal, formation of metal globules or ribbon fragments, oxidation of the ribbons, etc. These problems are particularly severe when working with high melting point alloys. This report describes certain experimental techniques used to overcome problems in preparation of metallic glass ribbons of iron-boron and other high melting point alloys. The ribbons thus produced have been characterized by transmission electron microscopy, mechanical tests and differential thermal analysis. The mechanical strength of the ribbon is comparable to the best recorded strength for ribbons of similar composition. Thedta data support the view that the formation of the phase Fe₂₃B₆ takes place upon crystallization of the eutectic alloy.     

Effect of metalloids on crystallization and magnetic behaviour of FeCoSiB based metallic glass

A series of amorphous iron-cobalt alloys with varying metalloid, boron and silicon contents were studied for their thermal stability and magnetic behaviour. The crystallization temperature and thermal stability increased with the silicon content. Good soft magnetic properties were observed for the materials with nominal composition, (Fe_0.79Co_0.21)77Si_12.2B_10.8. The magnetic properties were further improved by annealing.