Ni-based Metallic Glass Research Articles

Development of High Strength Ni–Cu–Zr–Ti–Si–Sn In-Situ Bulk Metallic Glass Composites Reinforced by Hard B2 Phase

In the present study, the influence of atomic ratio of Zr to Ti on the microstructure and mechanical properties of Ni–Cu–Zr–Ti–Si–Sn alloys is investigated. The alloys were designed by fine replacement of Ti for Zr from Ni39Cu20Zr36−xTixSi2Sn3. The increase of Ti content enhances glass forming ability of the alloy by suppression of formation of (Ni, Cu)10(Zr, Ti)7 phase during solidification. With further increasing Ti content up to 24 at.%, the B2 phase is introduced in the amorphous matrix with a small amount of B19′ phase from alloy melt. The bulk metallic glass composite containing B2 phase with a volume fraction of ~ 10 vol% exhibits higher fracture strength (~ 2.5 GPa) than that of monolithic bulk metallic glass (~ 2.3 GPa). This improvement is associated to the individual mechanical characteristics of the B2 phase and amorphous matrix. The B2 phase exhibits higher hardness and modulus than those of amorphous matrix as well as effective stress accommodation up to the higher stress level than the yield strength of amorphous matrix. The large stress accommodation capacity of the hard B2 phase plays an important factor to improve the mechanical properties of in situ Ni-based bulk metallic glass composites.

Helical Carbon Nanotube Fiber Tool Cathode for Wire Electrochemical Micromachining

Helical carbon nanotube fibers (CNFs), proposed as lightweight, high-strength, electrically conducting cables, have potential as tool cathodes in wire electrochemical micromachining (WECMM). WECMM has increasingly become recognized as a versatile technique for producing planar contour micro-features, and holds great advantages for micro-shaping of difficult-to-machine materials. However, the processing performance is affected by the mass transport rate in the narrow inter-electrode gap. Therefore, a helical CNF with superior hydrophilicity and high tensile strength is proposed as a new tool cathode for WECMM. Moreover, the electroplating technique is proposed as a means to improve the electrical conductivity of the CNF electrode. The synthesis of a Cu-CNF electrode had a two orders of magnitude enhanced electrical conductivity of about 2.0 × 107 S/m and a tensile strength of about 1350 MPa. An overall improvement of processing performance for WECMM was achieved. The machining accuracy in terms of slit width and its standard deviation were 38.8 μm and 0.2 μm, respectively. The surface average roughness of side wall was 0.022 μm. Finally, the five-layered micro tenon structures on Ni-based metallic glass were fabricated successfully by using three helical CNF electrodes simultaneously. The total machining efficiency in terms of feed rate attained 9.0 μm/s.

Micro-shaping of metallic glass by wire electrochemical micro-machining with a reciprocating traveling workpiece

Metallic glasses exhibit many outstanding properties, such as high hardness and strength, but their micro-shaping is still challenging. The technique of wire electrochemical micro-machining (WECMM) with a reciprocating traveling workpiece is proposed firstly for complex micro-shaping of metallic glasses. WECMM has increasingly become recognized as a versatile technique for producing planar contour micro-features, and holds promise for the micro-shaping of metallic glass structures. In WECMM, the processing performance is significantly affected by the mass transport rate in the narrow inter-electrode gap. Therefore, a new method with a reciprocating traveling workpiece is developed to enhance mass transport. Analysis of the electric field and flow field indicates that the reciprocating motion of the workpiece can facilitate active removal of electrolysis products and rapid refreshment of electrolyte, both of which are beneficial for maintaining a stable current density distribution on the machining surface. Taking a Ni-based metallic glass, Ni72Cr19Si7B2, as an example, the polarization and processing characteristics in dilute acid electrolyte are investigated. An overall improvement in processing performances is achieved. Finally, several complex five-layered microstructures are fabricated successfully using the optimized parameters. The resulting surface roughnesses Ra and Rmax are just 0.018 μm and 0.225 μm, respectively. The total machining efficiency in terms of feed rate reaches 4.0 μm/s.

Processing and Properties of Ni-Based Bulk Metallic Glass via Spark Plasma Sintering of Pulverized Amorphous Ribbons

ABSTRACTNi-based bulk metallic glasses and composites with high absolute densities exceeding 11 g/cm3 were synthesized via spark plasma sintering of Ni45Co10Ta25Nb20 powders produced from pulverized, melt-spun amorphous ribbons. Optimizing the synthesis via selection of sintering temperature, uniaxial load pressure, and powder mechanical screening yielded samples with relative densities of nearly 100% and hardness values in excess of 12.5 GPa without cracking. Mechanical testing included Weibull modulus determination for hardness and compression testing at 10-3 s-1 and 103 s-1 strain rates. The capability of using spark plasma sintering to fabricate high hardness, high density, large scale metallic glasses is demonstrated. The mechanical properties of these compacted comminuted melt-spun glass ribbons are presented.

Enhancement on GFA and mechanical properties of Ni-based bulk metallic glasses through Fe addition

Bulk Ni76-xFexP14B6Ta4 (x = 10, 20, 30, all in at.%) glassy alloy rods with diameters of 1.5–3.0 mm are synthesized by combining fluxing treatment and J-quenching technique, and the effects of Fe substitution for Ni on the glass forming ability (GFA), thermal stability, mechanical properties, and corrosion resistance of the present Ni-based bulk metallic glasses (BMGs) have been studied systematically in this work. It is found that the appropriate substitution of Fe for Ni can greatly enhance the GFA of the present Ni-based alloys, and the critical diameter for fully glass formation gets to the maximum value of 3.0 mm when the substitution content of Fe for Ni is 20 at.%. The corrosion tests show that the substitution of Fe for Ni causes a certain reduction of the corrosion resistance of the present Ni-based BMGs, but the corrosion current densities in both 1 M NaCl and 1 M HCl solutions are below the order of magnitude of 10−5 A/cm2 and the corrosion rate in1 M HCl solution is in the order of magnitude of 0.1 mm/year, still exhibiting a good corrosion resistance. The present Ni-based BMGs exhibit a compressive strength of more than 2.6 GPa and, more significantly, the substitution of Fe for Ni greatly enhances the compressive plasticity of the present Ni-based BMGs and the compressive plastic strain gets up to 6.6% when 20 at.% of Ni is substituted by Fe. This work indicates that the GFA and mechanical properties of Ni-based BMGs can be enhanced significantly through the Fe addition.

Wire electrochemical micromachining of metallic glass using a carbon nanotube fiber electrode

Metallic glasses are promising materials for realizing high-performance micro devices in micro-electromechanical systems (MEMS) owing to their excellent functional and structural characteristics. A significant limitation to their application is the challenge of shaping them on a microscale. A technique of wire electrochemical micromachining (WECMM) with a carbon nanotube fiber (CNF) as tool electrode is proposed for microstructure fabrication of metallic glass. WECMM is a type of electrochemical micromachining (ECMM) that is increasingly recognized as a flexible and effective technology to fabricate complex-shaped micro components. Taking the example of a Ni-based metallic glass, Ni72Cr19Si7B2, the polarization and fabrication characteristics in dilute acid electrolytes are investigated. As the machining gap is very small in WECMM, efficient mass transport is extremely important to improve the machining efficiency, stability, and quality. The efficiency of enhancing mass transport using a CNF electrode in this work is shown by flow-field simulation and hydrophilicity analysis, as well as experimental investigation. The maximum feed rate can be doubled and the homogeneity of machined slits improved more than five times compared with the results obtained using a smooth tungsten wire. Finally, complex microstructures based on metallic glass are fabricated by WECMM using a CNF electrode successfully.

Investigation on Wire Electrochemical Micro Machining of Ni-based Metallic Glass

Metallic glasses (MGs) have been recognized as promising materials for realizing high-performance micro devices in micro electromechanical systems (MEMS) due to their excellent functional and structural characteristics. However, the applications of MGs are currently limited because of the difficulty of shaping them on the microscale. Wire electrochemical micro machining (WECMM) is increasingly recognized as a flexible and effective method to fabricate complex-shaped micro metal components with many advantages relative to the thermomechanical processing, which appears to be well suitable for micro shaping of MGs. We consider the example of a Ni-based MG, Ni72Cr19Si7B2, which has a typical passivation characteristic in 0.1M H2SO4 solution. The transpassive process can be used for localized material removal when combined with nanosecond pulsed WECMM technique. In present work, the applicable electrolyte for WECMM of the Ni-based MG was discussed firstly. Then the voltage pulse waveform and electrolyte composition were modified to improve machining efficiency and stability. Several complex microstructures such as micro curved cantilever beam, micro gear, and micro square helix were machined with different optimized parameters.

Micropatterning of Ni-based metallic glass by pulsed wire electrochemical micro machining

The technique of wire electrochemical micro machining (WECMM) is proposed firstly for the micropatterning of Ni-based metallic glass in this paper. Metallic glass (MG) exhibits many outstanding properties such as high hardness and strength, which enable it to be used as functional and structural materials in micro electromechanical systems (MEMS). A significant limitation to the application of MGs is the challenge of shaping them on micro scale. WECMM is a non-traditional machining technique to fabricate microstructures that has some unique advantages over other methods, which will be a promising technique for micro shaping of metallic glass structures. Taking the example of a Ni-based glassy alloy, Ni72Cr19Si7B2, the polarization and fabrication characteristic in dilute hydrochloric acid electrolyte were investigated. Changes in the machined slit width in terms of several experimental parameters were investigated to find the optimal ones. Finally, the optimal machining parameters: HCl electrolyte concentration of 0.1 M, applied voltage of 4.5 V, pulse duration of 80 ns, pulse period of 3 μs and feed rate of 0.3 μm s−1 were employed for the fabrication of microstructures. Such as a micro square helix with a slit width of 14.0 μm, standard deviation of 0.2 μm and total length up to 2000 μm, along with a micro pentagram structure with side length of 90 μm and sharp corner of 36°, were machined with a high level of stability and accuracy.

Surface Characteristics of Ni-Based Metallic Glass in Wire Electrochemical Micro Machining

Surface characteristics of Ni-based metallic glass in wire electrochemical micro machining (WECMM) process are investigated firstly. Metallic glasses have a unique combination of enhanced mechanical and chemical properties due to the absence of crystalline features. However, their range of application is significantly limited because of the challenges faced when shaping them on a microscale. The technique of nanosecond pulsed electrochemical micro machining with a micro-wire tool electrode is introduced and a specially designed system is developed for micro-shaping metallic glass. Taking a Ni-based metallic glass, Ni72Cr19Si7B2, as an example, polarization and processing characteristics in dilute acid electrolytes are investigated. A significantly more uniform surface is obtained in H2SO4 than in HCl, because of the growth of a passive film during a stable passivation regime. A high current density is beneficial for good surface morphology and roughness. It is demonstrated experimentally that the use of a traveling cathode wire and a traveling anodic workpiece, as well as a carbon nanofiber tool electrode with good surface hydrophilicity, can enhance mass transport significantly in the machining gap. Enhanced surface quality of both front face and side wall is also achieved. Several complex microstructures with good surface quality are fabricated under different conditions.

Pitting resistivity of Ni-based bulk metallic glasses in chloride solution

Resistance of new Ni70Cr21Si0.5B0.5P8C≤0.1Co≤1Fe≤1 and Ni72.65Cr7.3Si6.7B2.15C≤0.06Fe8.2Mo3 glassy alloys to pitting corrosion was studied in 0.25 M sodium nitrate solution, with or without addition of chloride ions, using EIS, CP and EFM techniques.

Structural and mechanical properties of microwave sintered AlNi50Ti50 composites

Abstract Metal matrix composites (MMCs) have become attractive for structural engineering applications due to their excellent specific strength and are becoming an alternative to the conventional materials particularly in the automotive, aerospace and defence industries. The present work aims to synthesize and characterize the Al Ni 50 Ti 50 composites using microwave sintering technique with various weight fractions of reinforced particles. Ni-based metallic glass (Ni 50 Ti 50 ) powders were prepared by mechanical alloying. The microstructure and mechanical properties of Al Ni 50 Ti 50 composites were examined by X-ray diffraction (XRD), scanning electron microscopy (SEM), Vickers hardness and compression testing. The results show that the maximum average hardness value of 116 ± 5 Hv was measured for Al–20 wt% Ni 50 Ti 50 composite. The average compression strength of the composites was increased by 211% compared to pure Al.

Deformation Mechanisms and Fracture of Ni-Based Metallic Glasses

Abstract The cracking of materials and fracture surface is of great practical and academic importance. Over the last few years the development of the fractography of crystalline alloys resulted in a useful tool for the prediction or failure analysis. Many attempts have been made to observe cracks using optical microscopy, X-ray topography and transmission electron microscopy (TEM). Of these techniques, the resolution of optical microscopy and X-ray topography is too poor. By contrast, the resolution of TEM is high enough for detailed information to be obtained. However, in order to apply TEM observations, a thin foil specimen must be prepared, and it is usually extremely difficult to prepare such a specimen from a pre-selected region containing a crack. In the present work, deformation mechanisms fracture surfaces of Ni-based metallic glass samples have been studied by specially designed experiments. In order to study the deformation mechanisms and fracture the Ni-based metallic glasses have been investigated in the tensile test. The structure and fracture surfaces after the decohesion process in tensile tests were observed using transmission electron microscope (TEM) and scanning electron microscope (SEM), respectively. The studies of structure were performed on thin foils. Moreover the investigated tape was subjected to a banding test. Then, the tape was straightened and the thin foil from the area of maximum strain was prepared. This thin foil sample was deformed before the TEM investigation to obtain local tears.

Preparation of Ni-based bulk metallic glasses with high corrosion resistance

Bulk Ni77−x−yMoxCryNb3P14B6 (x=7 y=0; x=8 y=0; x=9 y=0; x=5 y=3; x=5 y=5; x=5 y=8; x=8 y=3; x=8 y=5, all in at.%) glassy alloy rods with the diameters of 1.0–1.5mm were synthesized by combining fluxing technique and J-quenching technique. The effects of Mo and Cr substitution for Ni on the glass forming ability (GFA), thermal stability, mechanical properties and corrosion properties of the present Ni-based bulk metallic glasses (BMGs) had been studied systematically. It is found that the substitution of an appropriate amount of Cr and Mo for Ni can enhance the GFA of the present Ni-based alloys, while excessive substitution will lead to the degradation of the GFA. The corrosion tests show that the corrosion current density and corrosion rate of most of the present Ni-based BMGs in 1M NaCl and 1M HCl solutions are in the order of 10−6A/cm2 and 10−2mm/year, respectively, exhibiting very high corrosion resistance. The addition of the appropriate Mo content and the Cr content as much as possible are benefit for the enhancement of the corrosion resistance of the present Ni-based BMGs. The compressive tests show that that the present Ni-based BMGs exhibit a compressive strength of 2.5–3.4GPa, but nearly zero compressive plasticity.

H+-induced irradiation damage resistance in Fe- and Ni-based metallic glass

In this study, use of 40-keV H+ ion for irradiating metallic glass Fe80Si7.43B12.57 and Ni62Ta38 as well as metallic tungsten (W) at fluences of 1×1018 and 3×1018ions/cm2, respectively, was investigated. At the fluence of 1×1018ions/cm2, a crystalline layer appeared in metallic glass Fe80Si7.43B12.57, with α-Fe as the major crystalline phase, coupled with a little Fe2B, Fe3B, and metastable β-Mn-type phase. Fe80Si7.43B12.57 exhibited good soft magnetic properties after irradiation. At the fluence of 3×1018ions/cm2, Ni62Ta38 was found to be amorphous-based, with a little μ-NiTa and Ni3Ta phases. No significant irradiation damage phenomenon appeared in metallic glasses Fe80Si7.43B12.57 and Ni62Ta38. Blistering, flaking, and other damage occurred on the surface of metallic W, and the root-mean-square (RMS) roughness increased with the increase of fluence. Metallic glass Ni62Ta38 exhibited better resistance to H+ irradiation than Fe80Si7.43B12.57, both of which were superior to the metallic W.

Erratum: “Effect of hydrothermal condition on the formation of multi-component oxides of Ni-based metallic glass under high temperature water near the critical point” [AIP Advances 5, 077132 (2015)

In the original manuscript, M. H. Lee’s affiliation number was incorrectly listed as 1. M. H. Lee’s correct affiliation number is 2 (Rare Metals R&D Group, Korea Institute of Industrial Technology, Incheon 406-840, South Korea). Furthermore, this change affects no other part of the paper.

A Numerical Simulation of a Ni-based Bulk Metallic Glass During Compressive Deformation and Fracture

On the basis of compression tests, uni-axial compression deformation and fracture behaviors of NiTiZrAlCuSi bulk metallic glass samples with different dimensions have been studied by numerical simulation approaches. Finite element models for compression simulation have been developed using ABAQUS software. Shear damage models were employed to reproduce the compression deformation and fracture process of the Ni-based amorphous alloys. Mises stress distribution and equivalent plastic strain obtained numerically during compression were analyzed. The simulation results were consistent with those of the compression experiment tests. The smaller of the samples exhibited larger plasticity and higher fracture strength when compared with the bigger one.

Effect of hydrothermal condition on the formation of multi-component oxides of Ni-based metallic glass under high temperature water near the critical point

The specific feature of multi-component oxides synthesized by hydrothermal process under high temperature (633 K) and highly pressurized water (18.9 MPa) near critical point. Effects of hydrothermal processing duration times 24 hours and 72 hours, respectively, on the oxide formation of the Ni59Zr20Ti16Si2Sn3 metallic glass synthesized by powder metallurgy process were characterized by X-ray diffractometer, differential scanning calorimeter along with the particle size, morphology and crystalline phase of the oxides. The crystallization of the needle-shape NiTiO3, ZrTiO4 and ZrSnO4 ternary oxide phases observed on the surface of metallic glass at below glass transition temperature and the morphology of oxide phases changed to plate-shape around 2 μm in diameter by the increase processing time. This hydrothermal processing in subcritical water provides accelerated dense metal oxide crystals due to the reaction medium being at higher pressure than conventional oxidation processing.

Co Oxidation Properties Of Selective Dissoluted Metallic Glass Composites

Abstract Porous metallic materials have been widely used in many fields including aerospace, atomic energy, electro chemistry and environmental protection. Their unique structures make them very useful as lightweight structural materials, fluid filters, porous electrodes and catalyst supports. In this study, we fabricated Ni-based porous metallic glasses having uniformly dispersed micro meter pores by the sequential processes of ball-milling and chemical dissolution method. We investigated the application of our porous metal supported for Pt catalyst. The oxidation test was performed in an atmosphere of 1% CO and 3% O2. Microstructure observation was performed by using a scanning electron microscope. Oxidation properties and BET (Brunauer, Emmett, and Teller) were analyzed to understand porous structure developments. The results indicated that CO Oxidation reaction was dependent on the specific surface area.

Preparation and properties of Ni68.6W17.9B13.5 metallic glass

A novel Ni-based metallic glass, i.e., Ni68.6W17.9B13.5 (mole fraction, %), was prepared using melt spinning method. The results showed that the element B has much effect on the glass forming ability of the Ni–W–B metallic glass. Ni–W–B metallic glass could not be fabricated with lower content of B, whereas a higher content of 13.5% B could easily lead to the fully amorphous structure. The glass transition temperature and the onset temperature of crystallization are as high as 768 K and 781.5 K, respectively, and the crystallization activation energy calculated by Ozawa model is (637±60) kJ/mol, which showed strong thermal stability of Ni68.6W17.9B13.5 metallic glass. This novel Ni-based metallic glass also exhibited good mechanical properties with the tensile strength of about 2331 MPa. The results indicate that this metallic glass should have a promising application in high strength material.

A New Ni-Based Metallic Glass with High Thermal Stability and Hardness

Glass forming ability (GFA), thermal stability and microhardness of Ni51−xCuxW31.6B17.4 (x = 0, 5) metallic glasses have been investigated. For each alloy, thin sheets of samples having thickness of 20 µm and 100 µm were synthesized by piston and anvil method in a vacuum arc furnace. Also, 400 µm thick samples of the alloys were synthesized by suction casting method. The samples were investigated by X-ray diffractometry (XRD) and differential scanning calorimetry (DSC). Crystallization temperature of the base alloy, Ni51W31.6B17.4, is found to be 996 K and 5 at.% copper substitution for nickel increases the crystallization temperature to 1063 K, which is the highest value reported for Ni-based metallic glasses up to the present. In addition, critical casting thickness of alloy Ni51W31.6B17.4 is 100 µm and copper substitution does not have any effect on critical casting thickness of the alloys. Also, microhardness of the alloys are found to be around 1200 Hv, which is one of the highest microhardness values reported for a Ni-based metallic glass until now.