[(Fe<Subscript>0.5</Subscript>Co<Subscript>0.5</Subscript>)<Subscript>0.75</Subscript>B<Subscript>0.20</Subscript>Si<Subscript>0.05</Subscript>]<Subscript>96</Subscript>Nb<Subscript>4</Subscript> Metallic Glasses with Small Cu Additions

Recently, (Fe-Co)-B-Si-Nb bulk metallic glasses (BMGs) were produced. Such BMGs exhibit high glass-forming ability (GFA) as well as good mechanical and magnetic properties. These alloys combine the advantages of functional and structural materials. The soft magnetic properties can be enhanced by nanocrystallization. To force the nanocrystallization, small content of Cu was added to the starting composition. In this article, {[(Fe_0.5Co_0.5)_0.75Si_0.05B_0.20]_0.96Nb_0.04}_100–x Cu _x glassy alloys (x = 1, 2, and 3) were chosen for investigation. The GFA and the thermal stability of these alloys were evaluated. The effects of crystallization during heat-treatment processes on the phase evolution and the magnetic properties, including M _s , H _c , and T _c , in these alloys were investigated. The phase analyses were done with the help of the X-ray diffraction patterns recorded in situ by using the synchrotron radiation in transmission configuration.     

Ti-Cu-Zr-Fe-Sn-Si-Ag-Pd Bulk Metallic Glasses with Potential for Biomedical Applications

Ti₄₇Cu_38−xZr_7.5Fe_2.5Sn₂Si₁Ag₂Pd_x (x = 1, 2, 3, and 4 atomic percent, at. pct) bulk metallic glasses (BMGs) with potential for biomedical applications were fabricated by copper-mold casting. The Ti-based BMGs exhibited high glass-forming ability (GFA) with critical diameters of 4 to 5 mm and a supercooled liquid region over 50 K, though the high contents of Pd slightly decreased the GFA. The additions of 2 and 3 at. pct Pd benefited the improvement of plasticity, and the resultant BMGs showed the relatively low Young’s modulus of about 100 GPa, high compressive strengths of 2174 to 2340 MPa, and compressive plastic strain of around 4 pct. The addition of Pd also decreased the passive current density and increased the pitting potential of the Ti-based BMGs in the Hank’s solution, leading to the enhanced bio-corrosion resistance of the BMGs. Furthermore, the cell adhesion, viability, and proliferation behaviors revealed that the present Ti-based BMGs possess as good biocompatibility as that of the Ti-6Al-4V alloy. These results demonstrated the potential of the Ti-Cu-Zr-Fe-Sn-Si-Ag-Pd BMGs as biomedical materials.

     

Electrochemical Behavior of an Amorphous and Nanocrystalline Fe<Subscript>79</Subscript>P<Subscript>13</Subscript>Si<Subscript>5</Subscript>V<Subscript>3</Subscript> Alloy in a Damp SO<Subscript>2</Subscript>-Contaminated Atmosphere

The electrochemical behavior of amorphous and nanocrystalline soft magnetic Fe₇₉P₁₃Si₅V₃ alloy in a 0.1 M Na₂SO₄ solution has been studied. Mössbauer studies show that the electrochemical characteristics of the alloy are comparable with those of an Finemet Fe₇₇Si₁₃B₇Nb_2.1Cu_0.9 alloy, whereas the studied alloy is inexpensive and can be prepared using natural alloy ferrophosphorus containing vanadium and silicon.     

Effect of quenching conditions on the structure and properties of a “thick” microwire fabricated by the Ulitovskii-Taylor method

The effect of quenching conditions on the mechanical and magnetic properties of a meltquenched wire with a core diameter of 50 μm, which is made of a model soft magnetic Co₆₉Fe₄Cr₄Si₁₂B₁₁ alloy and is fabricated by the Ulitovskii-Taylor method, is studied. The highest set of mechanical and soft magnetic properties of a wire is achieved when it is quenched from the upper position of a quenching stream. The lowering of the position of the quenching stream degrades the mechanical and magnetic properties of the wire at a retained amorphous structure in it.     

Effects of Alloying Elements on the Thermal Stability and Corrosion Resistance of an Fe-based Metallic Glass with Low Glass Transition Temperature

The effects of alloying elements on the thermal stability, glass-forming ability (GFA), corrosion resistance, and magnetic and mechanical properties of a soft magnetic Fe₇₅P₁₀C₁₀B₅ metallic glass with a low glass transition temperature (T _g) of 723 K (450°C) were investigated. The addition of Mo, Ni, and Co significantly increased the stabilization of supercooled liquid, GFA, and corrosion resistance in the H₂SO₄ solution. The maximum critical diameter (d _c) of 4 mm for glass formation was obtained for the Fe₅₅Co₁₀Ni₅Mo₅P₁₀C₁₀B₅ alloy, which shows the largest supercooled liquid region (ΔT _x ) of 89 K (89 °C). The substitution of Cr for Mo further enhanced the corrosion resistance of the Fe₅₅Co₁₀Ni₅Mo₅P₁₀C₁₀B₅, while the ΔT _x and d _c decreased. The (Fe, Ni, Co)₇₀(Mo, Cr)₅P₁₀C₁₀B₅ bulk metallic glasses showed low T _g of 711 K to 735 K (438 °C to 462 °C), wide ΔT _x of 67 K to 89 K, high saturation magnetization of 0.79 to 0.93 T, low coercive force of 2.36 to 6.61 A m^?1, high compressive yield strength of 3271 to 3370 MPa, and plastic strain of 0.8 to 2.3 pct. In addition, the mechanism for enhancing stability of supercooled liquid was discussed in terms of the precipitated phases during crystallization.     

Effect of annealing on the structure and mechanical properties of the maraging steel N9K17M14-nanoamorphous alloy Co69Fe4Cr4Si12B11 composite material

The effect of annealing on the structure, mechanical properties, and fracture of a one-dimensional composite material consisting of a microwire made of maraging N9K17M14 steel with a surface layer of a eutectic soft magnetic Co₆₉Fe₄Cr₄Si₁₂B₁₁ alloy is studied. The optimum temperature of annealing of the composite material is found; as a result, high strength characteristics are achieved at good plasticity. The composite material with a nanoamorphous layer is shown to have the high strength characteristics of the matrix maraging steel at significantly higher plasticity. When the Co₆₉Fe₄Cr₄Si₁₂B₁₁ alloy is deformed in the composition of the composite material, it exhibits a plasticity effect, and this alloy fails in a brittle manner when deformed in the form of a wire or a ribbon. This effect becomes more pronounced upon annealing.     

Effects of Cooling Rates on Glass Formation and Magnetic Behavior for the Fe73.0C7.0Si3.3B5.0P8.7Mo3.0 Bulk Metallic Glass

In this paper, effects of cooling rates on glass formation and magnetic behavior of the Fe_73.0C_7.0Si_3.3B_5.0P_8.7Mo_3.0 (at. pct) alloy were investigated via different purging gases (i.e., helium and argon) during suction casting. X-ray diffraction patterns and transmission electron microscopy characterization confirmed that the maximum attainable diameter for glass formation is increased from 5 to 7 mm with the helium as the purging gas, relative to the argon. Meanwhile, the coercivity value (H _c) of the sample cast in helium is almost 5 times larger than that fabricated in argon, although the magnetization saturation in these two alloys is similar. Our pair distribution function analysis, density, and positron annihilation lifetime spectroscopy measurements indicated that the sample cast in helium possesses more free volume; however, the difference between them is insubstantial. Further, experimental results revealed that the residual stress in the samples cast under helium is much larger than that in those prepared in Argon, which could be responsible for the abrupt change in the coercivity.     

Comparison of the Crystallization Behavior of Fe-Si-B-Cu and Fe-Si-B-Cu-Nb-Based Amorphous Soft Magnetic Alloys

The role of the solute elements, copper, and niobium, on the different stages of de-vitrification or crystallization of two amorphous soft magnetic alloys, Fe_73.5Si_13.5B₉Nb₃Cu₁, also referred to as FINEMET, and a Fe_76.5Si_13.5B₉Cu₁ alloy, a model composition without Nb, has been investigated in detail by coupling atom probe tomography and transmission electron microscopy. The effects of copper clustering and niobium pile-up at the propagating interface between the α-Fe₃Si nanocrystals and the amorphous matrix, on the nucleation and growth kinetics have been addressed. The results demonstrate that while Cu clustering takes place in both alloys in the early stages, the added presence of Nb in FINEMET severely restricts the diffusivity of solute elements such as Cu, Si, and B. Therefore, the kinetics of solute partitioning and mobility of the nanocrystal/amorphous matrix interface is substantially slower in FINEMET as compared to the Fe_76.5Si_13.5B₉Cu₁ alloy. Consequently, the presence of Nb limits the growth rate of the α-Fe₃Si nanocrystals in FINEMET and results in the activation of a larger no. of nucleation sites, leading to a substantially more refined microstructure as compared to the Fe_76.5Si_13.5B₉Cu₁ alloy.     

Diagnostics of the structure and phase composition of amorphous-nanocrystalline soft magnetic materials by magnetic methods

Various structural states, such as microcrystalline, submicrocrystalline, nanocrystalline (with various sets of grain sizes), and amorphous, are considered in soft magnetic materials intended for preparing sensitive elements for instruments used in high-tech processes. The effect of the structural state of amorphous Fe₅Co₇₀Si₁₅B₁₀, Fe₆₀Co₂₀Si₅B₁₅, and Co_81.5Mo_9.5Zr₉ alloys on their magnetic characteristics is studied under various nanocrystallization conditions. A correlation between the specific features of the fine structure and grain sizes in the alloys and the Barkhausen effect parameters is found.     

Retardation of annealing embrittlement in iron-based glasses by microaddition of cerium

The effects of microadditions of cerium on the rate of annealing embrittlement, stress relief, and as-quenched magnetic domain structure in three iron-based metallic glasses have been investigated. Ribbons melt-spun from optimally doped castings of composition Fe₈₀B₁₆Si₂C₂ and Fe₈₀B₂₀ did not embrittle during annealing until the onset of crystallization, whereas Fe₇₈B₁₃Si₉ ribbons were unaffected by cerium additions. In the first two glasses optimal doping resulted in the disappearance of quenched-in stresses in the ribbons, as evidenced by an absence of maze domains, and, for the Fe₈₀B₂₀ alloy, a slight enhancement of stress relief rate for small times and temperatures. The effects of doping were qualitatively different in the Fe₇₈B₁₃Si₉ glass. We conclude that annealing embrittlement in the first two glasses is an impurity effect, and that the embrittling impurities are oxygen and/or sulfur, the dissolved concentrations of which are strongly reduced by cerium additions. That low concentrations (50–100 at. ppm) of these impurities are sufficient to cause annealing embrittlement suggests that impurity segregation may be involved in the embrittlement process.     

Effects of B addition on glass forming ability and thermal behavior of FePC-based bulk metallic glasses

The FePC-based bulk metallic glasses (BMGs) have been demonstrated to possess high plasticity and good soft magnetic properties.However, the relatively poor glass forming ability (GFA) and thermal stabilities limited their application in industries.The effects of microalloying with B in FePC-based BMGs on the GFA and thermal behaviors were systematically investigated.It was found that a small amount of B addition can dramatically enhance the GFA of FePC-based BMGs, which in turn leads to the critical maximum diameter up to 2 mm for full glass formation even using low cost raw materi-als.The underlying mechanism of the enhancement of GFA from the competing crystalline phase with amorphous phase, the average thermal expansion coefficient and dynamic viscosity were dis-cussed in detail.     

Effect of Alloying Additions on Microstructure,Mechanical and Magnetic Properties of Rapidly Cooled Bulk Fe-B-M-Cu (M = Ti,Mo and Mn) Alloys

The influence of alloying additions on the microstructure, mechanical, and magnetic properties of bulk Fe₇₉B₂₀Cu₁, Fe₇₉B₁₆Ti₄Cu₁, Fe₇₉B₁₆Mo₄Cu₁ and Fe₇₉B₁₆Mn₄Cu₁ (at. pct) alloys was investigated. Nanocrystalline samples in the form of 3 mm rods were prepared directly by suction casting without additional heat treatment. Mössbauer spectroscopy, transmission electron microscopy and scanning electron microscopy studies confirmed that the investigated alloys consist α-Fe and Fe₂B nanograins embedded in an amorphous matrix. The addition of alloying elements, such as Ti, Mo and Mn to Fe₇₉B₂₀Cu₁ alloy increases the amount of amorphous phase and decreases the presence of Fe₂B phase in all examined alloys. The mechanical properties of the samples, such as hardness, elastic modulus, and elastic energy ratio, were analysed by an instrumented indentation technique performed on a 12 × 12 nanoindentation grid. These tests allowed to characterise the mechanical properties of the regions observed in the same material. For the Fe₇₉B₂₀Cu₁ alloy, the hardness of 1508 and 1999 HV, as well as Young’s modulus of 287 and 308 GPa, were estimated for the amorphous- and nanocrystalline-rich phase, respectively. The addition of Ti, Mo, and Mn atoms leads to a decrease in both hardness and elastic modulus for all regions in the investigated samples. Investigations of thermomagnetic characteristics show the soft magnetic properties of the studied materials. More detailed studies of magnetisation versus magnetic field curves for the Fe₇₉B_20−xM_xCu₁ (where x = 0 or 4; M = Ti, Mo, Mn) alloy, recorded in a wide range of temperatures, followed by the law of approach to magnetic saturation revealed the relationship between microstructure and magneto-mechanical properties.

     

Structure, Properties, and Glass Forming Ability of Melt-Spun Fe-Zr-B-Cu Alloys with Different Zr/B Ratios

Melt-spun ribbons of Fe_99–x–y Zr _x B _y Cu₁ alloys with x + y = 11 and x + y = 13 were prepared under similar experimental conditions and characterized for structure and soft magnetic properties. Substitution of Zr by B changes the structure of as-spun ribbons from completely amorphous to cellular bcc solid solution coexisting with the amorphous phase at intercellular regions and then to completely dendritic solid solution. The glass forming ability (GFA) of the Fe-Zr-B-Cu system, evaluated from thermodynamic properties such as enthalpy of mixing and mismatch entropy, is found to be in good agreement with the experimental observations. Annealing of all ribbons leads to the precipitation of nanocrystalline bcc α-Fe phase from both amorphous phase and already existing bcc solid solution. A window of alloy compositions that exhibit the best combination of soft magnetic properties (high saturation magnetization and low coercivity) was identified.     

Magnetic properties and microstructure of Fe_(69.5-x)Nd_7B_(21)Nb_(2.5)Ga_x(x=0-1)alloys

The Fe_(69.5-x)Nd_7 B_(21)Nb_(2.5)Ga_x(x = 0-1)permanent magnets in the form of rods were prepared by annealing the bulk amorphous alloys.The magnetic properties,phase evolution and microstructure of the alloys were investigated systematically.It is found that the glass forming ability(GFA), microstructure and magnetic properties are sensitive to Ga content for Fe_(69.5-x)Nd_7 B_(21)Nb_(2.5)Ga_x(x = 0-1)bulk alloys.The annealed alloys are mainly composed of soft α-Fe,hard Nd_2 Fe_(14)B and nonmagnetic Nd_(1.1)Fe_4 B_4 phases.When x = 0.3,the optimally annealed magnets exhibit magnetic properties of the remanence Br = 0.63 T,intrinsic coercivity H_(cj) = 368.68 kA/m and maximum energy product(BH)_(max) = 33.73 kJ/m~3.Furthermore,magnetic field heat treatment at the temperature close to Curie temperature of Nd_2 Fe_(14)B phase was applied to the annealed Fe_(69.2)Nd_7 B_(21)Nb_(2.5)Ga_(0.3) magnet.The results of X-ray diffraction(XRD)and transmission electron microscopy(TEM)indicate that the magnetic field heat treatment can be beneficial for the precipitation of α-Fe.Thus,the B_r,H_(cj) and(BH)_(max) are enhanced by 8.7%,6.3% and 16.3%,respectively.     

Influence of heat treatment on the efficiency of impact fragmentation of amorphous alloy Fe<Subscript>73.5</Subscript>Cu<Subscript>1</Subscript>Nb<Subscript>3</Subscript>Si<Subscript>13.5</Subscript>B<Subscript>9</Subscript> ribbons

The mechanism of impact fracture of soft magnetic amorphous alloy Fe_73.5Cu₁Nb₃Si_13.5B₉ ribbons in a disintegrator after heat treatment at a temperature from the range 300–700°C and the fractional composition of the formed powder are studied. The temperature ranges of a change in the mechanism of ribbon fracture are determined. The particle size distribution is shown to change weakly within the revealed temperature ranges.     

Prediction of Bulk Metallic Glass Formation in Cu–Zr–Ag–Hf System by Thermodynamic and Topological Modeling

Cu based bulk metallic glasses (BMGs) are widely studied because of their high glass forming ability (GFA) and interesting combination of properties such as high strength coupled with good ductility and low cost. With these attributes, Cu based BMGs are being projected as promising materials for practical applications. The process of glass formation in metallic systems is a challenging task and alloys should be cooled from the liquid state at rates faster than a critical cooling rate (R_c) to resist crystallization. Interestingly, composition plays an important role in achieving easy glass formation, which is usually measured in terms of R_c. In the present work, attempt has been made to identify the composition for easy glass formation in Cu based quaternary system by theoretical approach. A GFA parameter P_HS, which is a product of enthalpy of chemical mixing (?H_chem) and mismatch entropy normalized with Boltzmann??s constant (?S_??/k_B) is used to identify the best glass forming composition in Cu?CZr?CAg?CHf system. Further, a new parameter P_HSS, which is a product of P_HS and configurational entropy (??S_config/R) is found to illustrate strong correlation with GFA. An attempt has also been made to correlate P_HSS parameter with critical diameters and R_c using reported data in Cu?CZr?CAg?CHf system.     

The oxidation behaviour of amorphous and crystalline Fe78Si9B13

A combination of thermogravimetry, scanning and transmission electron microscopy, electron probe microanalysis and differential scanning calorimetry has been used to investigate the oxidation kinetics, and oxide morphology, structure and composition in amorphous and crystalline Fe₇₈Si₉B₁₃ alloys. Kinetic data indicate that the oxidation reactions of both amorphous and crystalline Fe₇₈Si₉B₁₃ obey a parabolic rate law over the temperature range 300 to 450°C with activation energies of 120 and 86 kJ/mol respectively, indicating that grain boundary diffusion is probably the rate controlling process. The parabolic rate constant for oxidation of crystalline Fe₇₈Si₉B₁₃ is consistently higher than for amorphous Fe₇₈Si₉B₁₃ over the temperature range 300–450°C, so that the amorphous alloy always shows a better oxidation resistance. Electron microscopy and electron probe microanalysis show that the oxide scales formed on both amorphous and crystalline Fe₇₈Si₉B₁₃ consist of SiO₂, Fe₃O₄ and Fe₂O₃, but the detailed microstructure and compositions are different. The oxide scale formed on amorphous Fe₇₈Si₉B₁₃ contains more SiO₂ and has a small particle size, while the oxide scale formed on crystalline Fe₇₈Si₉B₁₃ contains more Fe₃O₄ and consists of larger particles. The difference in oxide growth between amorphous and crystalline Fe₇₈Si₉B₁₃ is caused by the difference in alloy microstructure.     

Effects of Phosphorus and Carbon Contents on Amorphous Forming Ability in Fe-based Amorphous Alloys Used for Thermal Spray Coatings

Cost-effective Fe-based amorphous alloys used for thermal spray coatings were developed by varying contents of P and C, and their microstructure, hardness, and corrosion resistance were analyzed. In order to achieve chemical compositions having high amorphous forming ability, thermodynamically calculated phase diagrams of Fe-Al-P-C-B five-component system were used, from which compositions of super-cooled liquid having the lowest driving force of formation of crystalline phases were obtained. The thermodynamic calculation results showed that only phases of Fe₃P and Fe₃C were formed in the Fe₇₈Al₂P_(18.3?x)C _x B_1.7 alloy system. Considering driving force curves of Fe₃P and Fe₃C, the carbon contents were selected to be 6.90 and 7.47 at. pct, when the thermodynamic calculation temperatures were 697 K (414 °C) and 715 K (442 °C), respectively. According to the microstructural analysis of suction-cast alloys, the Fe₇₈Al₂P_10.83C_7.47B_1.7 alloy showed a fully amorphous microstructure, whereas the Fe₇₈Al₂P_11.40C_6.9B_1.7 and Fe₇₈Al₂P_10.3C_8.0B_1.7 alloys contained Fe₃P and Fe₃C phases. This Fe₇₈Al₂P_10.83C_7.47B_1.7 alloy showed the better hardness and corrosion resistance than those of conventional thermal spray coating alloys, and its production cost could be lowered using cheaper alloying elements, thereby leading to the practical application to amorphous thermal spray coatings.     

Microstructure and magnetic properties of Fe-Co-Nd-Y-B alloys obtained by suction casting method

The phase composition, magnetic properties i.e. coercivity and the magnetic polarization at room temperature for the bulk Fe₆₇Co₅Nd₃Y₆B₁₉ and Fe₆₄Co₅Nd₆Y₆B₁₉ alloys were studied. The bulk amorphous Fe₆₇Co₅Nd₃Y₆B₁₉ alloy, inhomogeneous in the as-quenched state, crystallized after annealing at 948 K for 0.5 h and consisted of Nd₂Fe₁₄B-type, Fe₂B and paramagnetic phases. The rapidly solidified Fe₆₄Co₅Nd₆Y₆B₁₉ alloy contained the Nd₂Fe₁₄B-type and paramagnetic phases. The annealing of the bulk Fe₆₇Co₅Nd₃Y₆B₁₉ alloy at 948 K for 0.5 h led to hard magnetic properties. However, the bulk Fe₆₄Co₅Nd₆Y₆B₁₉ alloy exhibited good hard magnetic properties directly after preparation.