Annealing effects in electrodeposited amorphous Co-P alloys

We observed how perpendicular magnetic anisotropy, present in electrodeposited amorphous Co-P alloys, changes during heat treatment in the presence or absence of a magnetic field. The results show that, apart from “columnar” shape anisotropy, there are other mechanisms of anisotropy present in the samples, first a stress anisotropy which can reach a value close to that reached by shape anisotropy and second directional-order anisotropy of smaller magnitude than that due to stress. The latter only occurs when the sample is heated to over 140°C.     

Magnetic annealing in electrodeposited Co-P amorphous alloys

The different diffusion processes that occur in electrodeposited Co-P amorphous alloys when they are subjected to magnetic annealing at different temperatures are studied by Coercive field measurements. Different processes are identified with different activation energies: 0.19 eV (stress relaxation): 0.75 eV (directional order); 2.9 eV (crystallization process). The low value of the activation energy for the first mechanism is identified with the diffusion of H, and that of the second with the diffusion of P.     

Local structure of amorphous and microcrystalline Fe-B alloys

Amorphous and microcrystalline Fe-B alloys in the composition range (4–25) at % B, fabricated by melt spinning, were investigated by pulse nuclear magnetic resonance (NMR) on ¹¹B nuclei at 4.2 K. Alloy samples were prepared both from a natural mixture of isotopes and an isotope mixture ⁵⁶Fe-¹¹B. The NMR spectra were measured at different boron contents. The local atomic structure of amorphous Fe-B alloys has been determined. The amorphous alloys consist of microregions (clusters) with short-range order of the tetragonal and orthorhombic Fe₃B-phase types, as well as of the α-Fe type.     

Preparation and characterisation of electrodeposited amorphous Sn-Co-Fe ternary alloys

Electrochemical deposition was investigated as a process to obtain alloys of Sn-Co-Fe, which to date have not been reported in the literature. A constant current technique was used to electrochemically deposit tin-cobalt-iron alloys from a gluconate electrolyte. The gluconate system was chosen as an electrolyte, which could potentially provide an environmentally safe process. The effect of plating parameters such as current density, deposition time, temperature and pH are discussed. Results are reported for current density and plating time using an electrolyte temperature of 20-60 °C and pH of 7.0 in relation to phase composition, crystal structure and magnetic anisotropy of the deposited alloys.Investigations were conducted using ⁵⁷Fe conversion electron Mössbauer spectroscopy (CEMS), ¹¹⁹Sn CEMS, transmission Mössbauer Spectroscopy and XRD. The ⁵⁷Fe and ¹¹⁹Sn CEMS spectra and XRD showed that the dominant phase in the deposits was amorphous Sn-Co-Fe. The relative area of the 2nd and 5th lines of the sextets representing the magnetic iron containing phases was found to decrease continuously with increasing current density while at the same time no significant changes in the magnetic anisotropy was found with plating time. Magnetically split ¹¹⁹Sn spectra reflecting a transferred hyperfine field were also observed.A range of good quality amorphous Sn-Co-Fe ternary alloys was obtained over a range of operating conditions from an environmentally acceptable gluconate electrolyte.     

Electrochemical behaviour of electrodeposited Fe—8P amorphous alloys

Mössbauer spectroscopy was used in order to study the influence of electrochemical behaviour of electrochemically deposited Fe—8P amorphous alloy. Electrochemically deposited amorphous samples were exposed to corrosion in the solution of H₂SO₄ and Na₂SO₄ containing NaHSO₃ at pH=3.5. CEM spectra of as-deposited samples exhibit a typical sextet of ferromagnetic amorphous state. Even with samples being kept under corrosion condition for 10 minutes, the Mössbauer spectra reveal an extra Fe(III) component.     

Reorientation kinetics of induced anisotropy in electrodeposited Co-P amorphous alloys

The kinetics of the reversible reorientation of induced magnetic anisotropy in electrodeposited Co-P amorphous alloys, have been studied from 75 to 151°C. Three different kinetic processes have been detected in each sample, each one of which is in accordance with an Arrehenius-type law. Two of the mechanisms are thought to be controlled by self-diffusion of P and the third is thought to be controlled by a kind of residual defect which remains although the samples were subjected to prolonged preannealing at temperatures higher than those used in this study.     

Ni-WC composite coatings by carburizing electrodeposited amorphous and nanocrystalline Ni-W alloys

In situ formation of tungsten carbide in the matrix of FCC nickel has been achieved by carburizing of the electrodeposited Ni-W alloy coatings. The size of the carbide particles ranges between 100 and 500 nm. The carbide phase is also present in the form of very small precipitates inside the nickel grains. The size of such precipitates is between 10 and 40 nm. The carburizing environment was created by introducing a flowing mixture of vaporized 95.5% alcohol (0.25 ml/min, liquid) and argon (0.5 L/min, gas) into the carburizing furnace. Supersaturated nature of electrodeposited amorphous and nanocrystalline alloys, in addition to high diffusivity, have been attributed for the formation of carbide phase in the deposits at a temperature range of 700-850 °C. The carbide-metal interface is clean and the composite coatings are compact. Hardness values up to about 1100 KHN are achieved. Hardness increases with tungsten content and carburizing temperature.     

铝基非晶合金微观结构的特点与演变

选择Al90Fe5Ce5和Al83Zn7Ce10非晶合金来研究铝基非晶合金的微观结构的特点和微观结构的演变.在Al90Fe5Ce5非晶合金中,发现亚稳Al6Fe相与被铝相包裹的二十面体准晶相共存.在Al83Zn7Ce10非晶合金中,金属间化合物Al2ZnCe2为凝固过程中的初生相.金属间化合物Al2ZnCe2可以伴随纳米晶粒铝的晶化而析出.抑制在冷却过程中所形成的各种晶核的成长是铝基合金具有很强的非晶形成能力的主要原因.多种相的竞争形核和有限生长导致了铝基合金具有复杂的结构特点 关键词： 铝基非晶合金 二十面体准晶 预峰 化学短程序     

On the microstructure of electrodeposited Fe−P alloys investigated with SAXS

Small angle X-ray scattering of Fe_1–x P _x , 0.05<x<0.25 suggests the existence of some volume percent of small domains with an electron density different from that of the matrix. The experimental diagrams can be described assuming three kinds of scatterers with different diameters not only in amorphous but also in microcrystalline material or in material including both phases. The diameters of the scatterers of one class are independent of composition and the microstructural state. The effect of annealing on a suitably defined inhomogeneity parameter indicates a different nature of the three classes of scattering centers. More information in this respect results from additional measurements of other physical properties.     

The phase composition of tin-nickel electrodeposited alloys

It was studied the tin phase composition of the electrodeposited alloys produced at different temperatures and current densities from an acid chloride/fluoride electrolyte and an acid chloride bath. Mössbauer spectra were consistent with a Ni₃Sn₄ intermetallic compound, dissolved tin, and a Cu?Sn intermetallic compound formed at the interface of the copper substrate.     

等温退火对辐照诱发的非晶TiNiCu合金微观组织结构的影响

 TiNiCu记忆合金在美国Argonne国家实验室IVEM Tandem National Facility加速器产生的400keV Xe+离子辐照到0.4dpa时发生非晶化转变。通过电子显微镜研究了非晶化的TiNiCu合金的回复和再结晶过程。退火加热的速度是10℃/min。在280℃时非晶环附近出现电子衍射斑点以及明场像中出现少量析出相，表明回复和再结晶开始。退火到550℃出现多晶环，650℃时有片状马氏体变体生成，750℃时有很锐利的多晶环出现，表明再结晶过程基本完成。经标定再结晶晶粒仍然是TiNiCu记忆合金。再结晶组织与辐照前TiNiCu 合金的显微组织相比有较大差异。     

等温退火对辐照诱发的非晶TiNiCu合金微观组织结构的影响

TiNiCu记忆合金在美国Argonne国家实验室IVEM Tandem National Facility加速器产生的400keV Xe+离子辐照到0.4dpa时发生非晶化转变。通过电子显微镜研究了非晶化的TiNiCu合金的回复和再结晶过程。退火加热的速度是10℃/min。在280℃时非晶环附近出现电子衍射斑点以及明场像中出现少量析出相,表明回复和再结晶开始。退火到550℃出现多晶环,650℃时有片状马氏体变体生成,750℃时有很锐利的多晶环出现,表明再结晶过程基本完成。经标定再结晶晶粒仍然是TiNiCu记忆合金。再结晶组织与辐照前TiNiCu 合金的显微组织相比有较大差异。     

Comparative Mössbauer study of short-range ordering in electrodeposited and rapidly quenched amorphous alloys

We have found significant differences between the low-temperature Mössbauer spectra of rapidly quenched and electrochemically prepared samples in the investigated cases even if the room temperature spectra were similar. In the spectra of electrodeposited alloys, a new component appears at low temperature. The results can be interpreted in terms of differences between the structures of rapidly quenched and electrodeposited anorphous alloys.     

Accurate prediction method for the microstructure of amorphous alloys without non-metallic elements

A new structural parameter of amorphous alloys called atomic bond proportion was proposed, and a topological algorithm for the structural parameter was proven feasible in the previous work. In the present study, a correction factor, λ, is introduced to optimize the algorithm and dramatically improve the calculation accuracy of the atomic bond proportion. The correction factor represents the ability of heterogeneous atoms to combine with one another to form the metallic bonds and it is associated with the uniformity of the master alloy, mixing enthalpy, cooling rate during preparation, and annealing time. The correction factor provides a novel pathway for researching the structures of the amorphous alloys.     

The temperature dependence of the magnetization of Fe-P, Co-P and Ni-P alloys

Foils of Fe_{100 ? x}, Co_{100 ? x}P_x and Ni_{100 ? ×P×} and were prepares by Eletro-deposition with 0 < x < 28. Materials with x is purely microcrystalline, material with x > 15 is purely amorphous. So the effects of composition and structural order on the magnetic properties of these alloys could be separated. The decrease of the magnetization with increasing temperature was measured by means of a vibrating sample magnetometer. The results are discussed on the basis of the spin wave concept. To describe the deviations of the experimental results from exact T^{$\text{3}\text{2}$}-laws temperature dependent spin wave stiffnesses are favored. The ratios spin wave stiffness to Curie temperature proved to be characteristic constants for each of the three alloy systems. The magnetic properties of a series are mainly determined by the transition metal component. The series differ from each other in the same sense as the pure metals. The change of the properties with the phosphorus content is first of all an effect of composition and far less an effect of structural order or disorder.     

Magnetic properties of electrodeposited iron-nickel alloys

The basic magnetic properties, viz., magnetic saturation and coercive force, have been established by measurement of about 150 specimens for electrodeposited iron-nickel alloys over the entire range of chemical compositions. The magnetization data were related ot the physicochemical aspects of the electrodeposition process.     

Mössbauer study of ionic and metallic states of electrodeposited Fe−Ni−P amorphous alloys

In this contribution we report cases in which we found ionic character of the amorphous state in electrodeposited Fe?Ni?P samples electroplated in a similar way but with different parameters to those exhibiting metallic amorphous character in their Mössbauer spectra. In particular, the room temperature transmission spectrum of an X-ray amorphous electrodeposited Fe₆₈Ni₂₃P₈ sample consists of two doublets with IS1=0.27 mm/s, QS1=0.51 mm/s, IS2=1.22 mm/s and QS2=2.54 mm/s parameters, where the latter is characteristic for Fe²⁺ state.     

Magnetic properties of electrodeposited copper-nickel composition-modulated alloys

Pulsed potentiostatic deposition offers a new technology for the production and stabilization of composition-modulated alloy (CMA) structures. Using this new technology, a series of Cu-Ni-modulated structures with layer thickness in the to 6 nm range were prepared. The first transmission electron micrographs of electrodeposited CMA are presented, showing the existence of sharp interfaces. Magnetic properties of the CMA structures were measured by vibrating sample and SQUID magnetometers, and by ferromagnetic resonance.     

Stability of amorphous alloys

The thermal stability of a number of Ti-base and Zr-base amorphous alloys was studied by means of differential scanning calorimetry. The crystallization temperatures of these amorphous alloys and those reported in the literature for a variety of other amorphous alloys (actinide-base alloys an refractory metal-base alloys) were analysed in terms of the corresponding formation enthalpies. It is shown that there is no correlation between the crystallization temperatures and the formation enthalpies. On the other hand the crystallization temperatures were found to scale more or less linearly to the corresponding formation enthalpies of a hole the size of the smaller type of atom in the binary amorphous alloys.