Study on crystallization phenomenon and thermal stability of binary Ni-Nb amorphous alloy

In this paper, a ribbon of binary Ni–Nb amorphous alloy was prepared by the melt spinning technique. Glass transition and crystallization phenomenon of the alloy were investigated by differential scanning calorimetry. Thermal properties of the ribbon of binary Ni–Nb upon heating and cooling were analysed by DTA at a heating/ cooling rate of 0.5 K s-1 under the purified argon atmosphere. The thermal stability of Ni–Nb amorphous alloy was studied by using an X-ray diffractometer equipped with an in situ heating system. The structure and fracture morphology of the ribbons were examined by X-ray diffraction and scanning electron microscopy methods

Formation and physical properties of Fe-based bulk metallic glasses with Ni addition

Purpose: The main aim of the paper was investigations of formation and changes of physical properties (magnetic properties and microhardness) of Fe based bulk metallic glasses (BMGs) with Ni addition. Design/methodology/approach: The following experimental techniques were used: transmission electron microscopy (TEM), scanning electron microscopy (SEM) and X-ray diffraction (XRD) phase analysis method to test the structure, electrical resistivity in situ measurements (four-point probe), measurements of magnetic properties, microhardness of investigated ribbons was determined by Vickers method. Findings: The structural studies revealed an amorphous structure for the ribbons with thicknesses up to 0.27 mm, regardless of their thickness. Research limitations/implications: More investigations for example Mössbauer spectrometry have to be conducted on different thickness of ribbons in order to confirm conclusions contained in the work. Practical implications: According to the results presented in the present paper the examined Fe-based bulk glassy alloys with Ni addition as a soft ferromagnetic material may be utilized in construction of magnetic cores such as choke coils, common mode and noise filter and is of great technological interest. Originality/value: The originality of the paper are examinations of changes of structure and physical properties on cross section and on surface of ribbons

Structure and magnetic properties of amorphous and nanocrystalline Fe85.4Hf1.4B13.2 alloy

Purpose: The forming of magnetic properties of the nanocrystalline Fe-based are different than those in conventional ferromagnetic materials that is: the soft magnetic properties increase with decreasing of grain size of crystalline phase Design/methodology/approach: The nanocrystalline Fe-based alloys could be obtain by many different methods, in this work first amorphous ribbons were obtained by planar-flow casting method and after that amorphous precursor were heat treated. The changes of structure associated to crystallization was investigated by X-ray diffractometry, the analysis of Mössbauer spectra made it possible to determine the average hyperfine field and volume fractions of α Fe crystalline phase. The changes of coercive force (Hc) of tapes were investigated using coerciometer with the terrestrial magnetic field compensation. Findings: The obtained results of investigations shows that crystallization process of amorphous Fe85.4Hf1.4B13.2 allowed to form nanocrystalline structure. This crystallization process has two-stages character and exhibit redistribution of the phases stages. The changes of magnetic properties has been observed with increasing the temperature annealing of investigated alloy. The coercive force is decreasing and minimum Hc is obtained at temperature 523 K. The obtained results showed clearly that for examined alloy is possible to determine the specific thermal treatment conditions (Top) causing an improvement of the magnetic properties. Practical implications: The possibility of optimization of soft magnetic properties is obtaining by the use of controlled crystallization of amorphous alloys. Originality/value: It has been found that the Fe85.4Hf1.4B13.2 alloys consisting of a mostly single bcc structure with nanoscale grains exhibit much better soft magnetic properties than in example well-known nanocrystalline Fe73.5Cu1Nb3Si13.5B9 . The group of Fe – M – B alloys is called NANOPERMTM. From a viewpoint of industrial application they are very attractive materials especially because of the highest BS among the nanocrystalline alloy

Crystallisation kinetics and magnetic properties of a Co-based amorphous alloy

Purpose: In the present paper, the kinetics of crystallization process and its correlation with magnetic properties of the Co80Si9B11 alloy was carefully examined. Design/methodology/approach: The following experimental techniques were used: X-ray diffraction (XRD), electrical resistivity in situ measurements (four-point probe), saturation magnetization in situ measurements (magnetic balance) and initial relative magnetic permeability measurements (Maxwell-Wien bridge). Findings: The investigations proved that thermal annealing of amorphous Co80Si9B11 alloy leads to a crystallization process and radical changes of magnetic properties. The activation energy of this process was determined as Ec=3.0±0.2 eV. Research limitations/implications: According to the results presented in the present paper the examined alloys can be used as a very good soft magnetic material. Originality/value: The best soft magnetic properties are observed in as quenched state

Thermal stability, crystallization and magnetic properties of Fe-Co-based metallic glasses

The aim of the paper was to investigate thermal stability, crystallization and magnetic properties of Fe-Cobased metallic glasses (MGs). Investigations were carried out on amorphous ribbons with the compositions of [(Fe0.5Co0.5)0.75B0.2Si0.05]96Nb4 and [(Fe0.6Co0.3Ni0.1)0.75 B0.2Si 0.05]96Nb4. Thermal properties (liquidus Tl and melting Tm temperatures) of the pre-alloyed ingots upon heating and cooling were analyzed by DTA at a heating/ cooling rate of 0.33 K s-1 under the purified argon atmosphere. The structure of the ribbons was examined by X-ray diffraction (XRD) and transmission electron microscopy (TEM) method. Kinetics of the crystallization process was examined by applying differential scanning calorimetry (DSC) method, and experiments performed in thermal analysis involve heating at a constant rates b = 0.17, 0.33 and 0.5 K s-1. Additionally, the conventional crystallization temperature Tx was determined from the normalized isochronal resistivity curves a(T) with heating rate 0.0083 K s-1. a is the temperature coefficient of resistance and a = q-1 dq/dT. The Tx, can be obtained from the condition a = 0 (Stokłosa et al. in J Alloy Compd 509(37):9050–9054, 2011). The saturation magnetization M(T) was measured in situ with heating rates 0.083 K s-1 using magnetic balance (Szewieczek and Lesz in J Mater Process Tech 162–163:254–259, 2005)

Influence of heat treatment on changes on structure and magnetic properties of CoSiB alloy

Purpose: This paper describes influence of heat treatment on changes on structure and magnetic properties of the amorphous Co77Si11.5B11.5 alloy. Design/methodology/approach: The following experimental techniques were used: X-ray diffraction (XRD), static and dynamic measurements of magnetic properties (magnetic balance, fluxmeter, Maxwell-Wien bridge). Findings: The crystallization process involved by heat treatment leads to significant changes of structure and magnetic properties of amorphous Co77Si11.5B11.5 alloy. Research limitations/implications: Practical implications: The attractive properties of Co-Si-B alloy are of special interest for basic research on the materials as well as for their potential applications, like magnetic sensors. According to the results presented in this paper the examined Co77Si11.5B11.5 alloy as a soft magnetic material may be used in noise filters, saturable reactors, miniature inductance elements for abating spike noise, zero-phase current transformers, and magnetic heads etc., i.e. devices which are expected to exhibit high levels of permeability at high frequencies. Originality/value: It has been shown that thermal annealing at temperature close to the crystallization temperature leads to a significant increase of the initial magnetic permeability

Crystallization kinetics of an amorphous Co77Si11.5B11.5 alloy

Purpose: This paper describes crystallization kinetics and changes magnetic properties involved by process of crystallization Co-Si-B amorphous alloy. Design/methodology/approach: The following experimental techniques were used: X-ray diffraction (XRD), electrical resistivity in situ measurements (four-point probe) static and dynamic measurements of magnetic properties (magnetic balance, fluxmeter, Maxwell-Wien bridge). Findings: In this work has been performed influence of thermal annealing on crystallization kinetics and magnetic properties amorphous Co77Si11.5B11.5 alloy. Practical implications: The attractive properties of Co-Si-B alloy are of special interest for basic research on the materials as well as for their potential applications, like magnetic sensors. The Co soft magnetic material is used in noise filters, saturable reactors, miniature inductance elements for abating spike noise, mains transformers, choke coils, zero-phase current transformers, and magnetic heads etc., i.e., devices which are expected to exhibit high levels of permeability at high frequencies. Originality/value: It has been shown that thermal annealing at temperature close to the crystallization temperature leads to a significant increase of the initial magnetic permeability

Structure and magnetic properties of the amorphous Co80Si9B11 alloy

Purpose: The main aim of the paper was to study the influence of heat treatment on changes of structure and magnetic properties of the amorphous Co80Si9B11 alloy.Design/methodology/approach: The following experimental techniques were used: X-ray diffraction (XRD), electrical resistivity in situ measurements (four-point probe), static and dynamic measurements of magnetic properties (magnetic balance, fluxmeter, Maxwell-Wien bridge).Findings: The crystallization process involved by heat treatment leads to significant changes of phase composition and magnetic properties of amorphous Co80Si9B11 alloy. The activation energy of this process was determined by Kissinger method, which yields Ec=3.0±0.2 eV.Practical implications: According to the results presented in the present paper the examined Co80Si9B11 alloy as a soft ferromagnetic material with high permeability may be utilized in construction of more inductive components and is of great technological interest

Influence of copper addition on properties of (Fe36Co36B19Si5Nb4)100-xCux metallic glasses

Purpose: The main aim of the paper was investigation of influence of copper addition on thermal, magnetic and mechanical (microhardness) properties of (Fe36Co36B19Si5Nb4)100-xCux (x=0 and 0.6) metallic glasses. Design/methodology/approach: The following experimental techniques were used: differential thermal analysis (DTA), transmission electron microscopy (TEM) and X-ray diffraction (XRD) method, measurements of magnetic properties, Vickers microhardness. Findings: It was shown that addition of small amount of copper to the base alloy induced a change of thermal, magnetic and mechanical properties. Research limitations/implications: The relationship between structure and magnetic and mechanical properties can be useful for practical application of these alloys. Practical implications: The (Fe36Co36B19Si5Nb4)100-xCux (x=0 and 0.6) metallic glasses due to a unique properties have been commercialized in the following application fields: precision mould material, precision imprint material, precision sensor material, precision machinery material and surface coating material. Originality/value: The originality of the paper are examinations of changes of thermal and mechanical properties combined with magnetic properties of the (Fe36Co36B19Si5Nb4)100-xCux (x=0 and 0.6) metallic glasses

Crack initiation and fracture features of Fe–Co–B–Si–Nb bulk metallic glass during compression

The aim of the paper was investigation crack initiation and fracture features developed during compression of Fe-based bulk metallic glass (BMG). These Fe-based BMG has received great attention as a new class of structural material due to an excellent properties (e.g. high strength and high elasticity) and low costs. However, the poor ductility and brittle fracture exhibited in BMGs limit their structural application. At room temperature, BMGs fails catastrophically without appreciable plastic deformation under tension and only very limited plastic deformation is observed under compression or bending. Hence a well understanding of the crack initiation and fracture morphology of Fe-based BMGs after compression is of much importance for designing high performance BMGs. The raw materials used in this experiment for the production of BMGs were pure Fe, Co, Nb metals and nonmetallic elements: Si, B. The Fe–Co–B–Si–Nb alloy was cast as rods with three different diameters. The structure of the investigated BMGs rod is amorphous. The measurement of mechanical properties (Young modulus - E, compressive stress - ?c, elastic strain - ?, unitary elastic strain energy – Uu) were made in compression test. Compression test indicates the rods of Fe-based alloy to exhibit high mechanical strength. The development of crack initiation and fracture morphology after compression of Fe-based BMG were examined with scanning electron microscope (SEM). Fracture morphology of rods has been different on the cross section. Two characteristic features of the compressive fracture morphologies of BMGs were observed. One is the smooth region. Another typical feature of the compressive fracture morphology of BMGs is the vein pattern. The veins on the compressive fracture surface have an obvious direction as result of initial displace of sample along shear bands. This direction follows the direction of the displacement of a material. The formation of veins on the compressive fracture surface is closely related to the shear fracture mechanism. The results of these studies may improve the understanding on the fracture features and mechanisms of BMGs and may provide instructions on future design for ductile BMGs with high resistance for fracture