Amorphous Fe40Ni40P14B6 Research Articles

Study on the Cutting Characteristics and Chip Formation Mechanism of Typical Amorphous Alloy Fe40Ni40P14B6 under Micro Cutting Conditions

Study on the Cutting Characteristics and Chip Formation Mechanism of Typical Amorphous Alloy Fe₄₀Ni₄₀P₁₄B₆ under Micro Cutting Conditions

Study of the dynamic of crystallization of an amorphous Fe40Ni40P14B6 ribbon through Johnson-Mehl-Avrami model

The study of the crystallization process of an amorphous Fe40Ni40P14B6 ribbon which is grown by the melt-spinning is reported. Differential scanning calorimetry (DSC), thermogravimetry (TGA), X-ray diffraction and magnetization measurements are used to investigate its dynamic of crystallization. DSC measurements show that a well-pronounced exothermic peak corresponding to first crystallization changes as function of the heating rate. For using the temperature calibration procedure of the thermogravimetric equipment, we are able to observe both the transition magnetic temperature of amorphous phase and the crystallization step observed in the differential scanning calorimetry measurements. The analysis of the dynamic of crystallization through Johnson-Mehl-Avrami (JMA) model allows us to state that the nucleation and grain growth processes occur by diffusion controlled growth. The analysis of the X-ray diffraction ex situ carried out after heating confirm the appearing of nanocrystalline Fe3B0.63P0.37 and Ni3P grains (of ≈40 nm) which are likely embedded inside a residual amorphous matrix. Finally, the increasing the crystallized fraction takes an important role on saturation magnetization and magnetic anisotropy.

Thermally induced crystallization of amorphous Fe40Ni40P14B6 alloy

The crystallization mechanism and kinetics of Fe40Ni40P14B6 amorphous alloy were studied under non-isothermal conditions. Thermal stabilization of this alloy manifests in DSC through two complex peaks, corresponding to crystallization and recrystallization, respectively. The complex crystallization DSC peak was deconvoluted into individual steps corresponding to crystallization of individual phases, where the results using both Gaussian–Lorentzian cross-product and Fraser–Suzuki function were compared. It was determined that the values of kinetic triplets of the individual steps did not exhibit any significant difference, depending on the deconvolution function. Anisotropic growth was indicated to be the prevailing type of impingement for all crystallization steps. Using the calculated values of the respective kinetic triplets and the mechanisms determined from the value of Avrami exponent, distinct values of activation energies for nucleation and crystal growth for crystallization of each individual phase were calculated, showing significantly higher values for nucleation than those for crystal growth. Alloy samples treated non-isothermally in the DSC cell exhibit inhomogeneous surface morphology with highly granulated structure dependent on heating rate.

Crystallization acceleration of amorphous Fe40Ni40P14B6 alloy by fluxing technique

The effect of fluxing on the structure and the crystallization of amorphous Fe40Ni40P14B6 alloy has been studied. Subjected to fluxing, the incubation time upon isothermal crystallization decreases, whereas, the onset crystallization temperature upon non-isothermal crystallization (with constant heating rate) decreases, and crystallization peaks become less sharp. via structural characterization, it is considered that fluxing promotes relaxation of the system; the atomic structure becomes more similar to the corresponding crystallized phase, thus alleviating the transient effect on nucleation and accelerates the crystallization.

Structural modification and phase transformation kinetics: crystallization of amorphous Fe40Ni40P14B6 eutectic alloy

The effect of processing histories (fluxing and pre-annealing) on the amorphous structure and the crystallization kinetics of amorphous Fe40Ni40P14B6 alloy prepared by melt spinning has been studied by differential scanning calorimetry, X-ray diffraction, transmission and scanning electron microscopy. For isothermal crystallization, an incubation time exists, and for isochronal crystallization, an abnormally sharp crystallization peak (with the transformed fraction corresponding to the transformation-rate maximum f p as less than 0.632) occurs. Subjected to fluxing and pre-annealing, the incubation time (in isothermal crystallization) decreases, whereas the initial crystallization temperature (in isochronal crystallization) declines as well as the less sharp crystallization peak and f p approaches 0.632. A kinetic model considering transient nucleation is proposed and analyzed, which could describe well the singular crystallization behavior of amorphous Fe40Ni40P14B6 alloy. A recipe based on the kinetic model is also proposed to obtain the kinetic parameters from experiment data. Via kinetic analysis and amorphous structural characterization, it is considered that pre-annealing and fluxing promote relaxation of the system close to the meta-stable equilibrium state; the atomic structure becomes more similar to the correspondingly crystallized phase, thus declining the amorphous stability and alleviating the transient effect on nucleation.

Crystallization of glassy Fe40Ni40P14B6 alloy on heating and the melt amorphization during melt-spinning processing

Crystallization of amorphous Fe40Ni40P14B6 melt-spun ribbons has been studied and analyzed using the classical theory equations. It was established that crystallization of this glass occurs by non-steady state homogeneous nucleation and interface controlled crystal growth. All parameters controlling the rates of crystal nucleation and growth including the temperature dependence of the transient time were estimated from comparison of the calculated kinetic curves with those experimentally measured. By substitution of these parameters and experimentally determined values of the heat transfer coefficient into the numerical approach describing crystallization in a melt-spinning technique amorphization of the Fe40Ni40P14B6 melt has been analyzed. The dominant role of the heterogeneous nucleating in this melt crystallization under rapid cooling in the majority of experiments has been confirmed and the most probable values of the heterogeneous sites density and wetting angle have been estimated by comparing of the experimental and calculated ‘temperature-time’ cooling curves.

Thermal evolution of ferromagnetic metallic glasses

A traditional TG apparatus was modified by placing two permanent magnets producing a controlled magnetic field (TG(M): Magneto Thermogravimetry). This technique proved to be useful to study both structural relaxation and crystallisation of ferromagnetic metallic glasses. Results obtained for the amorphous alloys Fe40Ni40P14B6 and Fe62.5Co6Ni7.5Zr6Nb2Cu1B15, are reported in this paper. Structural relaxation can be evaluated by measuring changes in Curie temperature induced by thermal treatments. Crystallisation in TG(M) is detected through a change in the measured apparent mass (difference between the sample mass and magnetic force driving it upward). These results were confirmed by DSC analysis. Whether the obtained crystalline phase is ferromagnetic, it can be identified through its Curie temperature, measured by TG(M). In fact the value of 770°C measured as Curie temperature of crystallised Fe62.5Co6Ni7.5Zr6Nb2Cu1B15led to conclude that the only ferromagnetic crystalline phase is a-Fe. These hypothesis was confirmed by XRD analysis, showing that the first crystallisation yields to a-Fe nanocrystals.

Deformation-induced microstructural changes in Fe40Ni40P14B6 metallic glass

The effect of mechanical deformation via high-energy ball milling on the structure of the Fe40Ni40P14B6 metallic glass was studied by means of x-ray diffactometry, transmission electron microscopy (TEM), and differential scanning calorimetry (DSC). After 5 h of milling, TEM observations indicated that some nanocrystallites with a diameter of about 6 nm precipitated from surface layers of the amorphous ribbons, whereas the bulk remained amorphous. When milling time was increased to 11 h, bulk crystallization occurred. The amorphous Fe40Ni40P14B6 alloy crystallized into a mixture of γ–(Fe, Ni) and (Fe, Ni)3(P, B). To understand the microstructural changes occurring in the amorphous ribbons before the onset of bulk crystallization, the isothermal crystallization behavior of as-deformed amorphous ribbons was studied. Compared with as-quenched amorphous ribbons, the local value of the Avrami exponent, derived from isothermal DSC data, increased from 3.5 to 4.1 for bulk crystallization. The thermal crystallization mechanism of deformed amorphous Fe40Ni40P14B6 ribbons changed from an eutectic-type reaction with simultaneous precipitation of γ–(Fe, Ni) and (Fe, Ni)3(P,B) from the amorphous matrix to a primary-type reaction with precipitation of α–Fe(P,B) preceding the formation of γ–(Fe,Ni) and (Fe,Ni)3(P,B). Our results suggest that several hours of mechanical milling cause surface crystallization and some atomic rearrangements in the amorphous alloy. The latter effect may be responsible for the observed primary-type reaction for crystallization of the deformed amorphous alloy

Polarization analysis of the magnetic excitations in Fe65Ni35 Invar

Triple-axis inelastic polarized neutron measurements have been performed as a function of temperature on a single crystal of the Invar alloy Fe65Ni35 to distinguish longitudinal from transverse magnetic excitations in the magnetically ordered phase. Well below the Curie temperature of 501 K the magnetic excitation spectrum is dominated by conventional transverse spin-wave excitations, which in fact follow the predictions of spin-wave theory very well. In particular, we find no evidence for propagating longitudinal excitations in this system, in sharp contrast to the behavior observed in the amorphous Invar Fe86B14 material as well as the non-Invar amorphous system Fe40Ni40P14B6.

Mechanisms of isothermal relaxation and recovery in the amorphous alloy Fe40Ni40P14B6

The relaxation and recovery behaviour of the spin-quenched amorphous alloy Fe40Ni40P14B6 is investigated by means of the magnetic after-effect. Three processes are clearly distinguished: (i) reorientation of anisotropic defect configurations; (ii) defect migration induced by magnetic anisotropies; (iii) diffusion due to quenched-in gradients of defect concentrations. This latter process, causing the transition of the as-quenched system into the completely relaxed glassy state, is thoroughly investigated in dependence on systematically varied thermomagnetic pretreatments of the alloy. Das Relaxations- und Erholungsverhalten der abgeschreckten, amorphen Legierung Fe40Ni40P14B6 wird mit Hilfe magnetischer Nachwirkungsmessungen untersucht. Drei Prozesse können deutlich unterschieden werden: (i) Reorientierung anisotroper Fehlstellen, (ii) Fehlstellenwanderung unter dem Einfluß induzierter magnetischer Anisotropien, (iii) Diffusion infolge eingeschreckter, inhomogener Fehlstellenverteilungen. Insbesondere der letzte, für den Übergang des Systems aus dem abgeschreckten in den vollständig relaxierten Glaszustand verantwortliche Prozeß wurde eingehend, nach jeweils systematisch geänderten thermo-magnetischen Vorbehandlungen der Legierung, untersucht.

Polarization analysis of the magnetic excitations in Invar and non-Invar amorphous alloys

Conventional spin wave theory works remarkably well in describing the spin dynamics of both Invar and non-Invar isotropic ferromagnets, with the important exception that for Invar systems the magnetization decreases much more rapidly with temperature than can be explained based on the measured spin wave dispersion relations. We have been carrying out triple-axis polarized inelastic neutron scattering experiments on the amorphous ferromagnets Fe86B14 (Invar system) and Fe40Ni40P14B6 (METGLAS■ 2826) in order to separate the longitudinal magnetic fluctuations from the transverse (spin wave) excitations, and thereby determine if the presence of longitudinal excitations might resolve this discrepancy. The present measurements exhibit longitudinal excitations below Tc, but in both materials. Possible interpretations of the results are discussed.

X-ray-absorption study of chemical short-range order in the amorphous Fe40Ni40P14B6 and Co70(Si,B)23Mn5(Fe,Mo)2 alloys.

X-ray-absorption fine-structure data of the metal-absorption edges in the amorphous Fe 40 Ni 40 P 14 B 6 and Co 70 (Si,B) 23 Mn 5 (Fe,Mo) 2 alloys suggest segregation into microphases with different stoichiometric compositions; in the first case the material contains microphases consisting mainly of Ni and P and others of mainly Fe and B. The second material contains microphases with mainly Co-Si stoichiometry and a Mn-Fe-Mo-B mixture in the remaining part of the sample

Short range order at the surfaces of annealed amorphous Fe40Ni40P14B6 ribbons

Conversion electron Mossbauer spectroscopy (CEMS) and gamma transmission Mossbauer spectroscopy were used to measure the effects of annealing at 583 K in vacuum into about 200 nm thick layer below the two surfaces and on the bulk of theFe40Ni40P14B6 amorphous ribbons prepared by means of melt-spinning technique. The results show a large distribution of hyperfine magnetic fields on the bulk and in the surfaces of the samples. By means of selective analysis of hyperfine magnetic field distribution, we have evalueded the correlation between the different degree of short range orders at the surfaces and in the bulk of the samples, and the phosphorus segregation associated with mechanical cubrittlement induced at low annealing temperature.

Oxidation state and short range order at the surfaces of amorphous Fe40Ni40P14B6 ribbons

Conversion electron Mossbauer spectroscopy (CEMS) was used to study the oxidation state at the surfaces of amorphous Fe40Ni40P14B6 ribbons obtained by melt-spinning in air and vacuum heated at 583 K. Different concentrations of ferric and ferrous ions depend on the different behaviour of phosphorous diffusion towards the two surfaces during low annealing temperature.

Structural segregation in amorphous Fe40Ni40P14B6 under heat treatment and natural ageing

Transmission and depth selective conversion electron Mossbauer spectroscopy (DCEMS) were applied usefully to study structural transformation in the bulk and in the surface layer in a≈50 and 100 nm thick amorphous alloy that was subjected to annealing and natural ageing. Analysis of the hyperfine field distributionsP(H) shows the segregation of the amorphous matrix.

Pressure effect on thermal relaxation behavior of the Curie temperature in amorphous alloys

The Curie temperature relaxation behavior in two amorphous ferromagnetic alloys (Fe10Co55Ni35)78Si8B14 and Fe40Ni40P14B6 (Metglas 2826) subjected to annealing at pressures up to 2 GPa is investigated. A comparison of the relaxed amounts of TC due to isothermal and isochronal annealings at 0, 1, and 2 GPa shows a delaying effect on the relaxation process during high-pressure annealing, while the concomitant kinetics of the processes remains unchanged. The pressure-induced percentage reductions in TC relaxation are estimated to be 8% and 12% per GPa, respectively. The reversible relaxation behavior was found still present during high-pressure annealing, but with a reduced amplitude. By annealing between high and low pressures at fixed temperature, some regenerative relaxation behavior was observed after every completion of the cyclic pressures. The obtained results may be explained by pressure-induced narrowing of regions in the amorphous structure. It is suggested that these extended regions are the main locations where the compositional short-range ordering contributed to TC relaxation.

Structural separation of amorphous Fe40Ni40P14B6 alloy during natural ageing

Both the transmission and depth selective conversion electron Mossbauer spectroscopy (DCEMS) were applied usefully to study structural transformations in the bulk and in the surface layer ∼50 and 100 nm thick during three years natural ageing of an amorphous alloy. The primary crystallization was revealed in the surface layer ∼100 nm thick on the rough side of amorphous ribbon.

Fractal analysis of magnetic aftereffects in the amorphous alloy Fe40Ni40P14B6 at 500 K (abstract)

Magnetic aftereffects (MAEs) of the initial reluctivity have been measured over times of 1–106 s in the as-quenched state of amorphous alloy Fe40Ni40P14B6 at 500 K. A considerable decrease in the relaxation amplitude observed for times t>103–10 s has been interpreted in terms of a superposition of two different mechanisms resulting from (i) quasi-reversible, local rearrangements of two-level systems, and (ii) irreversible, wide-range order relaxation due to the migration of free volumes.2 Here we report on the results obtained from fractal analysis of the short-time MAE region (t≲200 s). Fitting of the stretched exponential,3 exp[−(t/τ)ρ], (0<β<1), to the experimental data yielded values of ρ in the range 0.15–0.30. This implies a spectral (fracton) dimension d̃ of 0.3–0.6 for this alloy. In terms of a postulated ultrametric distribution of random energy barriers, this means a hierarchy with a low degree of ramification (Z∼1.2).

Influence of the melt temperature on the formation of soft magnetic properties of an amorphous Fe40Ni40P14B6 alloy

Influence of the melt temperature on the formation of soft magnetic properties of an amorphous Fe40Ni40P14B6 alloy

Thermal conductivity of the amorphous alloy Fe40Ni40P14B6 between 80 and 300 K

The thermal conductivity of the amorphous alloy Fe40Ni40P14B6 is investigated with the aim to separate out the lattice contribution and to compare it with that of amorphous dielectrics. The problems of the influence of the radiative transfer of heat between the sample and its environment, which causes errors in the determination of thermal conductivity, are discussed. The authors found that the temperature dependence of the lattice thermal conductivity of the alloys is qualitatively the same as that of amorphous dielectrics.