Fe 10Ni Research Articles

Crystallization of bulk amorphous alloy (Fe 40Ni 40P 14B 6) 96Ga 4 in supercooled liquid region

Transmission electron microscopy is used to resolve the crystallization of the bulk amorphous alloy (Fe 40Ni 40P 14B 6) 96Ga 4. Nanocrystallization is observed in supercooled liquid region for bulk amorphous alloy (Fe 40Ni 40P 14B 6) 96Ga 4. The annealing temperature varies from 680 K to 730 K where supercooled liquid region exists. The annealing time is 60 min for all samples. Crystallization does not occur until the annealing temperature exceeds 680 K. Crystal unions consisting of nanocrystals start to precipitate in amorphous base when the annealing temperature arrives at 690 K. The average diameter of crystal unions is about 150–250 nm. Crystal unions already knock together when the annealing temperature comes to 700 K. When the annealing temperature reaches 710 K, another microstructure is formed, consisting of the uniform nanocrystals with a grain size of about 8 nm. When the annealing temperature is increased to 730 K, the nanocrystals grow up into the bacilliform crystals with the average diameter of about 30 nm.

Studies of crystallization and soft magnetic properties of FeNiMoB(Si) alloys

Crystallization behaviors of Fe 40Ni 38Mo 4B 18, Fe 38Ni 35Mo 4Si 5B 18, and Fe 39Ni 36Mo 2Si 5B 18 (at%) amorphous alloys as well as magnetic properties of the Fe 40Ni 38Mo 4B 18 alloy, annealed in the temperature range from 400 to 520 °C for 1 h, have been investigated. The results show that for the samples of Fe 40Ni 38Mo 4B 18, annealed in the temperature range of 430–450 °C, a single-crystalline FCC phase with composition near Ni 3Fe solid solution and grain size of about 10 nm precipitates in the amorphous matrix, and the samples exhibit good soft magnetic properties. As the samples are annealed at T a⩾470 °C, the magnetic properties drop rapidly, this is mainly due to the formation of Fe–B and Ni–B compounds. For the samples of Fe 38Ni 35Mo 4Si 5B 18 and Fe 39Ni 36Mo 2Si 5B 18, a single FCC crystalline phase structure cannot be formed in the amorphous matrix, where more than single-crystalline phase such as Fe–B compounds as well as γ-(Fe, Ni) phase are precipitated almost simultaneously by the annealing treatment.

The ring-shaped magnetoelastic torque sensors utilizing soft amorphous magnetic materials

This paper presents results of the investigation on a novel solution in construction of the magnetoelastic torque sensors. In this solution, ribbon ring-shaped magnetic materials based on both iron and nickel were used. Due to a special backing glued to the ring-shaped core the uniform stresses under the influence of the torque can be achieved. As a result magnetoelastic properties under the influence of the torque can be tested. For investigation both Fe 78B 13Si 9 and Fe 40Ni 38Mo 4B 18 alloy compositions in as-quenched and annealed state were used. In annealed Fe 40Ni 38Mo 4B 18 core, under the torque equal 4 Nm, was observed a decreasing of flux density from 301 to 108 mT.

Compaction of bulk amorphous Fe 40Ni 40P 14B 6 alloys

The consolidations of two bulk amorphous Fe 40Ni 40P 14B 6 alloy discs are performed via hot pressing for a short time in its supercooled liquid region under a pressure of ∼1.2 GPa. When the consolidated temperature T s is lower, the conjunction of two bulk amorphous Fe 40Ni 40P 14B 6 alloy discs cannot be achieved. Only when T s get to the vicinity of 675 K, two amorphous Fe 40Ni 40P 14B 6 alloy discs have low viscosity enough to be fully fused together in a short time and the resulting compacts retain ∼90% amorphous phase. To further improve the consolidated temperature T s, a vast amount of crystallization will occur and result in the embrittlement of amorphous alloy.

Fe xNi 100− x nanometric films deposited by laser ablation on SiO 2/Si substrates

Fe x Ni 100− x nanometric films were deposited on SiO 2/Si substrates at room temperature using the pulsed laser deposition technique. The targets were Fe–Ni amorphous magnetic foils with composition Fe 50Ni 50, Fe 35Ni 65 and Fe 22Ni 78. Morphological and structural properties of the deposited films were investigated using scanning electron microscopy, Rutherford backscattering spectrometry, grazing incidence X-ray diffraction, and X-ray reflectivity. Electrical and magnetic characteristics of the films were investigated by using the four-point probe and the magneto-optic Kerr effect techniques, respectively. The film properties are strictly dependent on the Fe–Ni compositional ratio.

On short-range ordering in Fe–Ni alloys

In the work, the X-ray electron spectroscopy and molecular dynamics methods were used for investigating the electron and atomic structure of Fe–Ni alloys in order to explain the variations in their short-range order. The comparative study was carried out for the Fe–Ni system with the invar (Fe 65Ni 35) and non-invar (Fe 25Ni 75) compositions at two different temperatures (with heating). The presence of the invar effect in the Fe–Ni alloys can be related to strong local distortions in the fcc lattice leading to the redistributions of atoms in the nearest environment.

Surface properties and activity of Fe–Ni–B ternary glasses

The surface structure, composition and corrosion behavior of metallic glass (MG) ribbons of the Fe–Ni–B system, with nominal composition Fe 40Ni 40B 20 are investigated by X-ray diffraction, Auger electron spectroscopy (AES) and energy dispersive X-ray spectroscopy (EDS). We found that the surface is Fe enriched at the expense of both Ni and B, while exposure to 200 eV N + and Ar + plasma modifies slightly the top surface layer further enriching the surface with Fe; in the case of N +, strong incorporation of N is detected indicating the formation of nitride phases. The corrosion behavior of the Fe–Ni–B surfaces was studied by electrochemical techniques in aquatic solutions of NaCl, NaOH, HNO 3 and HCl. Corrosion properties are very satisfactory compared to other MGs and engineering crystalline alloys with similar base compositions.

Nanoparticle morphology in FeNi–Cu granular films with giant magnetoresistance

A series of (Fe 50Ni 50) x Cu 1− x granular films were prepared using the magnetron-controlled sputtering method. The nanoparticle morphology and giant magnetoresistance (GMR) of FeNi–Cu films deposited at room temperature were investigated through the transmission electron microscope (TEM) and the conventional four probes method under room temperature, respectively. Upon varying the magnetic volume fraction x, the GMR of as-deposited FeNi–Cu films reached a maximum of about 1.8% at a volume fraction of 32% FeNi. In addition, TEM observation disclosed that FeNi–Cu films consist of FeNi nanoparticles dispersed in Cu matrix and form FCC structure. For films with lower volume fraction of FeNi particles, the size distribution of FeNi particles satisfied a log-normal function. With increasing volume fraction of FeNi particles, the size distribution of FeNi particles deviated gradually from a log-normal function. Meanwhile, the average size of FeNi particles increased monotonically with increasing volume fraction of FeNi particles, leading to the fact that GMR can reach a peak value at a certain middle particle size. In addition, the relationship between GMR and nanoparticle morphology of granular films was discussed.

Critical cooling rate for the glass formation of ferromagnetic Fe 40Ni 40P 14B 6 alloy

Bulk ferromagnetic amorphous Fe–Ni–P–B alloys in rod shape were formed by a rapid solidification technique. The largest amorphous specimen prepared had a diameter of ∼ 2.5 mm and the corresponding cooling rate for the glass formation of this alloy system in our experiment can be estimated to be around 492.4 K/s by the method of finite-difference numerical calculation. This value is on the same order of magnitude as the critical cooling rate R c of Fe 40Ni 40P 14B 6 alloy estimated by the method of constructing the continuous-cooling-transformation (CCT) curve. It is indicated that the heterophase impurities have been eliminated well in our experiment.

Thermal expansion of anti-invar alloys up to high temperatures

The thermal expansion of the anti-invar alloys Fe–20Ni–6Mn, Fe–22Ni–3Cr–0.15C and Fe–14Ni–7Mn–0.6C which are used commercially as active side materials in bimetals was determined from RT up to 1500 K. All alloys show an enhanced thermal expansion coefficient, CTE, in the temperature range up to 1200 K with peaks around 500 and 1000 K. For T>1200 K d(CTE)/d T becomes negative, i.e., the CTE is smaller than the normal lattice expansion in this temperature range. This means that an invar like behavior is observed in this temperature range.

Mechanical alloying of the FeNi–Ag system

The Fe–Ni–Ag system is of particular interest for its potential applications as soft magnetic granular material with small magnetic grains embedded in a non-magnetic metal matrix. Under equilibrium conditions: Fe–Ag and Ni–Ag are immiscible and Fe–Ni shows complete solubility. These materials are particularly important for magnetoresistivity properties. The properties of these alloys are closely related to their microstructure; therefore, a detailed study of the transformations occurring during milling was undertaken using pre-alloyed Fe x Ni 100− x ( x = 30, 50 and 70) further milled with different Ag content to give the following alloys compositions (Fe x –Ni 100− x ) 100− y Ag y ( y = 5, 20, 60). Consolidation of the mechanically alloyed powders by sintering at 950 °C was performed. Morphological and structural characterization of the sintered powders was carried out by scanning and transmission electron microscopy and X-ray diffraction. Fe 30Ni 70 and Fe 50Ni 50 formed ordered FeNi 3 compound. Fe 70Ni 30 showed the formation of a mixture of γ-(Fe,Ni) and α-Fe(Ni) solid solutions. The mixture of these systems with Ag showed the metal solid solutions surrounded by Ag islands of Fe x Ni y –Ag, There was also evidence of Ag diffusing into the γ-(Fe,Ni). High Ag content (60%) shows formation of islands of FeNi surrounded by Ag. Sintering is always improved with the Ag content.

Axial ratio of an Fe–30Ni–0.23C bct martensite determined by neutron diffraction

When an Fe–30Ni–0.23C alloy is cooled below Ms temperature lower than RT, in situ neutron diffraction has revealed that newly transformed bct martensite shows a high axial ratio, c/ a-value. When the sample is heated from 100 K to RT, the c/ a apparently decreases. Such a change in c/ a indicates that, even below RT, there is carbon diffusion to induce tempering effect. When a quenched martensite is tempered at 473 K, the c/ a is drastically decreased.

Crystallography of upper bainite in Fe–Ni–C alloys

The upper bainite structures were investigated in Fe–9Ni–(0.15–0.5)C (mass%) alloys transformed at temperatures between 723 and 623 K. A bainite packet similar to lath martensite is formed and is partitioned into blocks containing lath-shaped bainitic ferrite with the same parallel close-packed plane relationship of the K–S relationship. Its feature is categorized into three types: (A) a packet contains laths of two K–S variants with a small misorientation (sub-blocks), (B) a packet is divided by blocks largely misoriented and each block contains sub-blocks and (C) a packet is divided by blocks containing a single variant of laths. A packet of type (A) is formed at 723 K in each alloy whereas the packet type becomes (B) or (C) at lower temperatures. As a result, bainite blocks are refined with decreases in transformation temperature and carbon content. In contrast, blocks and packets of lath martensite are refined with increasing carbon content.

Crystallography of ausformed upper bainite structure in Fe–9Ni–C alloys

The effect of ausforming on formation of upper bainite structure was investigated in Fe–9Ni–(0.15–0.5)C (mass%) alloys, focusing on the crystallographic feature of bainitic ferrite. The specimens were ausformed at 1073 or 873 K by 50% compressive reduction after austenitizing, and transformed at 623 K. Lath-shaped upper bainite structures similar to lath martensite are formed at 623 K. A bainite packet is partitioned into blocks of all the six variants of the K–S orientation relationship satisfying the same parallel close-packed plane relationship. In both of the non-ausformed and ausformed specimens, bainite blocks are coarsened with increasing carbon content. In the Fe–9Ni–0.15C alloy, the effect of ausforming on the bainite block width is small. For higher carbon alloys (Fe–9Ni–0.3C and 0.5C), bainite blocks are remarkably coarsened by the ausforming. In contrast, the ausforming refines lath martensite blocks in the Fe–9Ni–0.15C alloy but has a small effect in higher carbon alloys.

High resolution transmission electron microscopy study on the nano‐scale twinning of θ‐NiMn precipitates in an Fe–Ni–Mn maraging alloy

AbstractPrecipitation of nanometer‐sized fct θ‐NiMn intermetallic compound was found to cause age hardening in Fe–10Ni–7Mn (wt%) maraging alloy during isothermal aging at 753 K. High resolution transmission electron microscopy was used to study the substructure of the fct θ‐NiMn precipitates in the alloy after aging for 0.36 and 86.4 ks. Nano‐scale twins on (111) planes were found in the precipitates of intial and later stages of aging. Precipitation of bcc β‐NiMn at 753 K and subsequent martensitic transformation to fct θ‐NiMn during cooling to room temperature was suggested. It was also indicated that precipitation of fct θ‐NiMn at bcc iron matrix gives rise to high coherency strain energy. The (111) twinning is proposed to accommodate the strain energy of either martensitic transformation or coherency strain of precipitation reaction. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Analytical transmission electron microscopy study of grain boundary precipitates in an Fe–Ni–Mn maraging alloy

Field-emission gun analytical transmission electron microscopy was used to study grain boundary precipitates in Fe–10Ni–7Mn (wt.%) maraging alloy after isothermal aging at 753 K. High spatial resolution energy dispersive X-ray spectroscopy was used for quantitative chemical analysis of the grain boundary precipitates. Precipitation of f.c.t. θ-NiMn intermetallic compound and reversion to f.c.c. austenite were identified at prior austenite grain boundaries after prolonged aging. Selected area electron diffraction patterns (SADPs) showed the L1 0 type ordering of f.c.t. θ-NiMn precipitates. The f.c.t. θ-NiMn precipitates showed higher Ni and Mn concentrations than reverted f.c.c. austenite.

A study on microstructure, magnetic properties and kinetics of the nanocrystallization of Fe 40Ni 38B 18Mo 4 metglass

This study has investigated the microstructure and magnetic properties of Fe 40Ni 38B 18Mo 4 at various degrees of crystallization from the amorphous state. TEM and XRD studies confirmed that phases forming after crystallization at temperatures around 414 and 522 °C were cubic (Fe, Ni, Mo) 23B 6 phase and FCC (Fe, Ni) solid solution. The growth behavior and morphology of the nanocrystalline phases have been studied as a function of time and temperature. Nanoparticles were lying in the size range of 10–20 nm and they were stable below 522 °C. Kissinger approach, Ozawa method and Yi Qun Gao method were employed to determine and compare the kinetic parameters of the crystallization processes. A growth mechanism of crystallizing phases was proposed on the basis of these results. Magnetic properties mainly coercivity and saturation magnetization of as-received and heat-treated samples were evaluated.

Effects of oblique-incidence evaporation on magnetic properties of Fe 20Ni 80/Fe 70Co 30 bilayer film

Evaporative deposition at oblique incidence is shown to enhance the magnetic anisotropy of an Fe 20Ni 80 magnetic film and induce magnetic anisotropy in an overlying, strongly isotropic Fe 70Co 30 film. This deposition method for the formation of an underlayer of several lattice parameters in thickness and semi-hard overlayer of a few thousands Angstroms in thickness achieves a significant change in the magnetization process and strong suppression of the coercive forces of Fe 70Co 30 in the hard magnetization direction. Soft magnetization of the Fe 70Co 30 overlayer is not achieved when one of the layers is deposited at oblique incidence. It is anticipated that shape magnetic anisotropy is responsible in part for the magnetic anisotropy induced in both in Fe 20Ni 80 under- and Fe 70Co 30 overlayer by oblique incidence evaporation.

Formation of ferromagnetic bulk amorphous Fe 40Ni 40P 14B 6 alloys

Ferromagnetic bulk amorphous Fe 40Ni 40P 14B 6 alloy rods with a diameter of ∼ 1.2 mm can be prepared by means of a rapid quenching technique. If a fluxing technique is also used, amorphous rods with a diameter as large as ∼ 2.5 mm can be synthesized. The critical cooling rate R c for the glass formation Fe 40Ni 40P 14B 6 is estimated to be on the order of 10 2 K s − 1 .

Nanocrystalline structures obtained by the crystallization of an amorphous Fe 40Ni 38B 18Mo 4 soft magnetic alloy

The kinetics of crystallization of a soft magnetic amorphous Fe 40Ni 38B 18Mo 4 alloy was studied by TEM, EDX and resistivity methods. The kinetic parameters were measured from TEM studies and resistivity measurements. Nanocrystals of the fcc FeNi phase were found to crystallize by a primary crystallization mechanism followed by slow growth kinetics. The volume fraction measured by TEM matches well with that calculated from resistivity results and a TTT diagram was constructed. Quantitative measurements of the nucleation and growth rates as a function of temperature and time were performed. The nucleation rate was found to decrease with an increase in heat treatment time due to an increase in boron content in the amorphous matrix as the crystallization took place. The crystal growth was found to slow down considerably due to the presence of Mo. The crystal size was calculated according to the Michels model and compared to our experimental results. Molybdenum was found to dramatically alter the energetics of crystallization, the morphology of the crystals and particularly the kinetics of crystallization. These results offer a method of creating new families of nanostructured magnetic materials by suitable molybdenum addition.