Amorphous Fe40Ni40P14B6 Research Articles

Study of the structure of annealed amorphous Fe40Ni40P14B6

Amorphous Fe40Ni40P14B6 alloys are investigated by means of X-ray diffraction, small angle X-ray scattering, and transmission electron microscopy in dependence on heat treatment. Below the crystallization temperature structural changes are observed, which point to the formation and to the growth of small crystalline regions in the amorphous matrix. Die Struktur der amorphen Legierung Fe40Ni40P14B6 wird in Abhängigkeit von Wärmebehandlungen mittels Röntgenbeugung, Kleinwinkelstreuung und Transmissionselektronenmikroskopie untersucht. Es werden unterhalb der Kristallisationstemperatur strukturelle änderungen gefunden, die mit der Bildung und dem Wachstum mikrokristalliner Bereiche in der amorphen Matrix interpretiert werden.

The Curie temperature relaxation behavior of metglases 2826 and (Fe0.1Co0.55Ni0.35)78Si8B14 under high pressure

Relaxation behavior of the Curie temperature (Tc) of two amorphous alloys Fe40Ni40P14B6 and (Fe0.1Co0.55Ni0.35)78Si8B14 was investigated under high pressure up to 20kbar. Experimental results show that Tc relaxation process was restrained by high pressure. On the other hand, alternative treating sample at different pressures may enhance this process. Based on the expansion of local pressed region in an amorphous structure, a mechanism of relaxation under high pressure was suggested for explaining the above phenomena.

The coercive field of the partially crystallized amorphous alloy Fe40Ni40P14B6

The influence of isothermal crystallization on the coercive field of the amorphous alloy Fe40Ni40P14B6 is investigated by combining magnetic measurements and transmission electron microscopy (TEM) observations. It is found, that the statistically distributed crystalline regions with barrel like shape and diameters up to some micrometers act as pinning centres for domain walls. In the early stage of crystallization the coercive field is mainly determined by the pinning of the domain walls in the amorphous phase at statistically distributed crystallites. With increasing degree of crystallization the coercive field of the alloy is determined by the coercive fields of the different crystalline phases.

Effect of Irradiation on Amorphous Alloy Fe40Ni40P14B6

The effect of 40 keV helium ion irradiation on the amorphous alloy Fe40Ni40P14B6 has been studied. Conversion electron Mössbauer spectra taken from the near surface region of the irradiated alloy show the presence of crystalline phases after a total does of 1.6×1018 ions/cm2. The crystallization process is found to be different from that in the thermally-treated amorphous alloy without irradiation. It is also observed that the crystalline phases appear together with surface damage such as blistering and exfoliation.

Changes in the remanent magnetisation, magnetoelastic coupling and Young's modulus during structural relaxation of an amorphous ribbon

The kinetics of structural relaxation have been studied in the amorphous alloy Fe40Ni40P14B6 over the temperature range 230-380 degrees C, by the analysis of the magnetoelastic coupling coefficient, Young's modulus and remanent magnetisation. Measurements provide evidence that different mechanisms should be considered in order to explain the observed behaviour. The results are discussed in terms of different theoretical relaxation models previously reported. Comparison of relaxation data with those predicted from models based on an activation energy spectrum shows an overall consistency.

Investigation of Structural Defects in the Amorphous Ferromagnetic Alloy Fe40Ni40P14B6

AbstractStructural defects in the amorphous ferromagnetic alloy Fe40Ni40P14B6 are investigated by measuring the magnetic polarization in the region of approach to ferromagnetic saturation. From the field dependence of the high‐field susceptibility it is concluded that the main source of internal stresses may be characterized as quasi‐dislocation dipoles. These structural defects are shown to be rather stable under annealing treatments and may be produced by small plastic deformations.

Domain structure and behavior in Fe40Ni40P14B6

An experimental investigation was conducted to determine the static and dynamic domain characteristic of the amorphous alloy Fe40Ni40P14B6 both before and after proton irradiation to compare with samples before and after annealing. The as-received samples show the combination of wide wavy slab-like domains, regions of a star-like domain pattern, and a fine domain structure with magnetization normal to the ribbon surface, as has been noted by others. Observation of this domain structure under dynamic magnetization conditions, by means of the Kerr magneto-optic effect, indicated nonreproducibility in the domain pattern from cycle to cycle. Following annealing at 189 °C for 3 1/2 h, with a proton fluence of 5×1015/cm2 at sufficient energy to penetrate through the sample, only straight slab-like domains could be observed. Kerr effect observations of the dynamic domain behavior revealed a high degree of reproducibility from cycle to cycle. This suggests that the nonreproducibility in the as-received samples is most likely due to the residual stresses and defects incorporated into the sample during the melt-spinning operation. The surface roughness of the melt-spun sample probably plays a less important role in the domain reproducibility.

The activation energy of crystallization of amorphous Fe40Ni40P14B6

The isothermal crystallization of Fe40Ni40P14B6 (Metglas 2826) has been studied by transmission electron microscopy, using static observations of partially crystallized ribbons at room temperature and in situ dynamic registration of the crystallization process at elevated temperatures. At all temperatures crystallization takes place by the nucleation and growth of individual crystals. Analysis of the transformation kinetics allowed to determine the nucleation rates and the activation energy for crystal growth. The growth velocity of the crystal phase was found to be controlled by the diffusion coefficient of phosphorus in this alloy withD 0=2.5×1010±1cm{swu2}/s andQ=(3.4±0.15)eV.

Deformation of amorphous Fe40Ni40P14B6 under compression to 250 kbar

Amorphous Fe40Ni40P12B6 was compressed in the diamond anvil cell up to a 250 kbar pressure, and the pressure was measured as a function of position with the ruby fluorescence method. Analysis of the spatial distribution of the pressure indicates that the flow stress σy of the material varies as σy = 17 exp(0.004 P), with σy and P expressed in units of kbar. The increase in the flow stress with pressure corresponds to an activation volume of 0.16 Å.3 The pre-exponential factor represents the flow stress of the material at zero pressure. Because the material in a diamond cell is subjected to a very extensive plastic flow before the pressure distribution is established, this value is not necessarily identical to the flow stress measured with more conventional methods, involving no or very little prior plastic deformation. The latter methods tend to measure higher values for σy, indicating that metallic glasses undergo work softening when deformed extensively.

Point defects in amorphous Fe80B20and Fe40Ni40P14B6studied by positron lifetime and magnetic after-effect

Abstract Amorphous Fe80B20 and Fe40Ni40P14B6 alloys are studied before and after low temperature electron irradiations by positron lifetime and magnetic after-effect methods. The results show that in amorphous state all positrons are trapped by quenched-in voids of less than one atomic volume. Electron irradiation produces vacancy-like defects which recover continuously up to room temperature making only a few reorientation jumps before annealing.

Low field magnetic properties of amorphous Fe40Ni40P14B6 ribbons

Low field magnetic properties of amorphous Fe40Ni40P14B6 ribbons

Acoustic barkhausen emission in amorphous metallic alloys Fe40Ni40P14B6 and Fe78Mo2B20

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Transversal magnetic field effect on Fe40Ni40P14B6 amorphous alloys

A study about the influence of an electric current flowing through an amorphous ribbon Fe40Ni40P14B6 has been done. It has been found that the magnetization curves are strongly influenced by such a current (from 0 up to 5000 Hz). Bitter patterns under the action of the current have been observed in order to gain a better knowledge of these effects. The wall energy has been evaluated from a simple model.

Micro inversion domains formed during the crystallization of the amorphous alloy Fe40Ni40P14B6

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Structural relaxation in amorphous Fe40Ni40P14B6alloy studied by positron annihilation

The Doppler-broadened line shape of 511 keV gamma rays emitted from annihilating positron-electron pairs, the positron lifetime and electrical resistivity of the amorphous Fe40Ni40P14B6 alloy have been measured in the 0-500 degrees C temperature range using isochronal annealing. The W parameter of the Doppler-broadened line shape, related to core-electron annihilation, increased in two stages by annealing below the crystallisation temperature. These increases appear to be due to the loss of excess free volume in the as-quenched amorphous alloy.

FREE VOLUME CHANGE OF METALLIC GLASSES STUDIED BY THERMAL EXPANSION MEASUREMENTS

A dilatation set up was designed and used to investigate the low temperature relaxation of amorphous Fe40Ni40B20 and Fe40Ni40P14B6 through observed changes during isothermal annealing. In addition to the anticipated contraction on annealing, these amorphous alloys exhibited peaks in their dilatation curves brought about by a simultaneous but temporary expansion during structural relaxation. Although there was a considerable difference in the length change of Fe40Ni40B20 and Fe40Ni40P14B6 samples, the low temperature relaxation behaviour of both alloys was qualitatively similar and the relaxation parameter could be described by an equation of the form : [MATH]

Energy-Dispersive Diffraction Analysis of the Structure of Metallic Glasses

AbstractThe intensities of x-rays scattered by amorphous Fe80P13C7 and Fe40Ni40P14B6 samples have been measured as a function of photon energies E at fixed scattering angles 2θi using a Li-drifted Si detector and polychromatic x-rays generated by a 50KV full-wave rectified generator. The coherently scattered intensity per atom was calculated for free-standing samples as well as samples contained in a Be or pyrolytic graphite cell, after the evaluation of the energy dependence of the primary beam spectrum by an iterative process. The interference functions were then calculated from the data obtained in transmission and reflection, and compared with those measured with the conventional variable 2θ technique. Good agreement between energy-dispersive diffraction (also called variable wavelength technique) and variable 2θ diffraction was observed in all cases.

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.

Temperature dependence of the flow stress and ductility of annealed and unannealed amorphous Fe40Ni40P14B6

The flow stress and ductility of amorphous Fe40Ni40P14B6 was investigated on asprepared and annealed ribbons over the temperature range 78 to 573 K. The embrittlement is characterized by a rise in the ductile-to-brittle transition temperatureTdtb, such thatTdtb≈Tanneal and sets in at temperatures as low as 423 K. The flow stress of Fe40Ni40P14B6 at room temperature is 2.21 GPa (320 ksi), in good agreement with the extrapolation from hardness measurements. The flow stress increases with decreasing temperature. The increase can be accounted for in dislocation-based models of the deformation of a metallic glass but is more difficult to understand in terms of a free volume model.

Hall resistivity of a two-phase magnetic material-crystallised Metglas 2826

Hall resistivity measurements in the temperature range 100-800K have been used to study the influence of thermal cycling and annealing on amorphous Fe40Ni40P14B6. While the as-received sample has Tc=510K, thermal cycling to 700K yields a two-phase system, one of the phases have a broad transition around 425K. Annealing for three hours at 800K causes this transition to sharpen up, and a second transition at 730K is also observed. The extraordinary Hall coefficient (R1) has been analysed and is described in terms of linear contributions from each phase. From simultaneous measurements of the ohmic resistivity rho on the same sample it is found that, for the two-phase material, R1 is related to rho as R1=a rho +b rho 2 for 100<T<300K. In the amorphous state there is an anomaly in rho at Tc. From the relationship between R1(T) and rho (T) it is concluded that in both amorphous and crystallised materials the side jump is of the same order of magnitude as in dilute Fe alloys.