Metallic Glass Alloys Research Articles

Shear band multiplication aided by free volume underthree-point bending

Zr52.5Cu17.9Ni14.6Al10Ti5 bulk metallic glass (BMG) alloy samples in both rod and plate geometry were prepared. Different free volume states were obtained through thermal treatment. The plastic deformation ability of the BMGs was investigated through both a three-point bending test and compression test. The three-point bending results reveal the important role of free volume content on the formation of multiple shear bands, as the shear band propagation can be efficiently stopped due to the existence of the stress gradient from the surface to the neutral plane. In compression, the sample size rather than free volume controls the shear banding behavior.

Synthesis of Fe Based Metallic Glass–Pd Based Metallic Glass Composite by Slightly Pressured Liquid Phase Sintering

To consolidate [(Fe0.5Co0.5)0.75Si0.05B0.2]96Nb4 metallic glass powder to full density, a pressurized liquid phase sintering was employed, which was intended to promote densification by an enhanced wetting of a liquid phase with solid particles. Pd42.5Ni7.5P20Cu30 metallic glass powder, which has been reported to have a high glass forming ability and the lowest critical cooling rate of glass formation of 0.067 K/s, was chosen as a liquid phase component. The melting point of the Pd42.5Ni7.5P20Cu30 metallic glass alloy of 763 K is lower than the glass transition temperature of the [(Fe0.5Co0.5)0.75Si0.05B0.2]96Nb4 metallic glass alloy of 808 K. However, the wettability of this alloy with the Pd42.5Ni7.5P20Cu30 alloy was revealed to be poor. Therefore, sintering pressure was applied to the compacts to promote a viscous flow deformation of solid particles and also to enhance the intergranular permeation of the liquid phase. A specially designed micro-hot press was devised for the pressure-sintering experiment. A pseudo-wettability was observed during pressure-sintering, and the liquid phase was found to fill completely the intergranular space of the powder compact. The relative density of 64–95%, as well as the sintering structure, could be controlled by the punch displacement to squeeze out a part of the liquid phase from the compact. The compressive fracture strength of the obtained metallic glass composite was found to be as high as 2051 MPa, and the fracture was observed to be intragranular type, suggesting a good bonding in the particle-binding phase interface.

Zr계 벌크 비정질 복합재의 변형률 속도에 따른 인장 변형 거동 연구

Tensile deformation behavior with different strain rate was investigated. (bulk metallic glass alloy possessed crystal phase which was called -phase of dendrite shape, mean size of and occupied 25% of the total volume) was used in this study. Maximum tensile strength was obtained as 1.74GPa at strain rate and minimum strength was found to be 1.6GPa at . And then, maximum plastic deformation occurred at the strain rate of and represented 1.75%, though minimum plastic deformation showed 0%. In the specific range of strain rate, relatively higher plastic deformation and lower ultimate tensile strength were found with lots of shear bands. The fractographical observation after tensile test indicated that vein like pattern on the fracture surface was well developed especially in the above range of strain rate.

Wettability and reactivity between B 4C and molten Zr 55Cu 30Al 10Ni 5 metallic glass alloy

The isothermal wetting and spreading behaviors of molten Zr 55Cu 30Al 10Ni 5 metallic glass alloy on B 4C substrates were studied using a modified sessile drop method at 1133–1253 K in a high vacuum. A distinct reaction layer consisting of ZrB 2 and ZrC x was produced at the interface and displayed good wettability with the molten alloy. The entire spreading kinetics could be characterized by four representative stages: (i) an initial rapid spreading presumably driven by adsorption of the active Zr atoms at the solid–liquid interface, (ii) a quasi-linear and (iii) a linear spreading stage controlled by the chemical reaction between Zr and B 4C in both cases, and (iv) an approach-to-equilibrium stage with precipitation of crystals in the liquid. An increase in temperature promotes the wetting and reaction. In view of the reasonable wettability and reactivity, there is a potential for preparing Zr-base bulk metallic glass matrix composites reinforced by in situ ZrC–ZrB 2 hybrid ceramic particulates using B 4C as a reaction agent by way of an infiltration synthesis technique.

Low-temperature brazing of titanium by the application of a Zr–Ti–Ni–Cu–Bebulk metallic glass (BMG) alloy as a filler

Titanium (Ti) was successfully brazed at low temperatures below 800 °C by employing a Zr 41.2Ti 13.8Ni 10.0Cu 12.5Be 22.5 (at.%) bulk metallic glass (BMG) alloy as a filler. Through the use of this alloy filler, the detrimental segregation of Zr–Cu–Ni filler elements was completely eliminated by heating to well below 800 °C, so the resultant joint was quite homogeneous with a coarse acicular structure. The disappearance of the Zr–Cu–Ni segregated region was rate-controlled by the diffusion of the filler elements in the Ti base metal. Remarkably, the mechanical property and corrosion resistance of the homogeneous joint brazed at 800 °C for 10 min were mostly comparable to those of bulk Ti.

Calculation of transient nucleation rate for Pd and Zr based metallic glass alloys

In order to investigate the glass forming ability, a new method to evaluate the transient nucleation rate of glass alloys is provided in the present paper using the parameters of bulk metallic glasses, such as onset melting temperature, glass transition temperature, viscosity and the cooling rate. The transient nucleation rates of Au81Si19, Pd75Si25 and Zr–Al–Ni–Cu alloys are obtained with this method. The computing result for Au81Si19 agrees well with that of the literature. The results show that with increasing viscosity or cooling rate, the nucleation rate drops sharply. When the cooling rate reaches to 103 K s–1, the peak value of nucleation rate of Pd75Si25 falls to 104 mol–1 s–1. Under the cooling rate of 102·5 K s–1, the peak value of nucleation rate of Zr66Al9Ni9Cu16 decreases to 105 mol–1 s–1. To Zr66Al8Cu7Ni19, Zr66Al8Cu12Ni14, Zr66Al9Cu16Ni9 and Zr65Al7·5Cu17·5Ni10 alloys, with increasing content of Cu, the supercooled liquid region ΔTx rises and the nucleation rate falls gradually.

Modeling and Simulation of Fe-Based Metallic Glass Alloys Preparation Process

The simulation for the preparation process of Fe-based glass alloys was performed, and the temperature, cooling rate crystalline fractions are obtained in this article. The simulation results illustrate that crystalline phase can precipitate in the central part and near the top surface of the sample. For Fe83B17, Fe79Si10B11, and Fe30Co30Ni15Si8B17, the crystalline phase can reach the highest value of 0.1075, 0.09650, and 0.06720, respectively. Comparatively lower nucleation rate, as well as the higher viscosity and the cooling rate account for the formation of the bulk metallic glass.

Electron-irradiation-induced nano-crystallization in quasicrystal-forming Zr-based metallic glass

Phase selection in electron-irradiation-induced crystallization and crystal-to-amorphous-to-crystal (C–A–C) transition at 298 K in quasicrystal-forming Zr–Pt metallic glass alloys were investigated. Two types of f.c.c. nano-crystalline precipitates were formed in amorphous Zr 80Pt 20 and Zr 66.7Pt 33.3 alloys under electron irradiation; such unique nano-crystalline structures were not observed during thermal annealing. It was inferred that unique phase selection in electron-irradiation-induced crystallization and thermal crystallization can be explained by the large negative chemical mixing enthalpy (Δ H chem) in Zr–Pd and Zr–Pt alloys.

The Coupling Effect of Small Nanocrystals and Free Volume on the Ductility of Cu46Zr47Al7Bulk Metallic Glass Alloy

The Coupling Effect of Small Nanocrystals and Free Volume on the Ductility of Cu₄₆Zr₄₇Al₇Bulk Metallic Glass Alloy

Dependence of Ductility on Free Volume in a Cu‐Zr‐Based Metallic Glass

Cu46Zr47Al7 bulk metallic glass alloy samples with different free volume states were obtained through thermal treatments such as annealing and quenching. Three-point bending tests were performed to these samples to evaluate their ductility. The results demonstrate that the ductility of BMGs is closely related to the free volume. The reduction in the free volume is the dominant reason for the embrittlement of samples annealed below Tg. In addition, the ductility of embrittled samples can be enhanced by restoring free volume by a short anneals above Tg followed by quenching.

Indentation creep of a Ti-based metallic glass

In this work, the time-dependent plastic deformation behavior of Ti40Zr25Ni3Cu12Be20bulk and ribbon metallic glass alloys was investigated using a nanoindentation technique at room temperature with the applied load ranging from 5 to 100 mN. The stress exponentn, defined as, has been derived as a measure of the creep resistance. It was found that the measured stress exponent increases rapidly with increasing indentation size, exhibiting a positive size effect. The size effect on the stress exponentnobtained from the bulk sample is more pronounced than that obtained from the ribbon sample. The deformation mechanism involved will be discussed.

Failure behavior of Cu–Ti–Zr-based bulk metallic glass alloys

Microstructure fracture and mechanical properties of Cu-based bulk metallic glass alloys were investigated. Centrifugal casting into copper molds were used to manufacture basic Cu47Ti33Zr11Ni9, and modified Cu47Ti33Zr11Ni7Si1Sn1 alloys. Although the alloys show an amorphous structure, TEM images revealed the formation of nanoparticles. At room temperature compression tests reveal fracture strength of 2000 MPa, elastic modulus of 127 GPa, and 1.8% fracture strain for the unmodified basic alloy. Whereas the modified alloy exhibits a fracture strength of 2179 MPa, elastic modulus reaches 123 GPa, and 2.4% fracture strain. So, with the addition of 1 at.% Si and Sn, the fracture strength improves by 9% and the fracture strain improves by 25%, but the fracture behavior under compression conditions exhibits a conical shape similar to that produced by tensile testing of ductile alloys. A proposed fracture mechanism explaining the formation of the conical fracture surface was adopted. The formation of homogeneously distributed nano-size (2–5 nm) precipitates changes the mode of fracture of the metallic glass from single to multiple shear plane modes leading to the conical shape fracture surface morphology.

鋭い切欠の高強度部材の疲労特性のE依存性とその機械,構造の疲労設計への影響の重要性

The author suggested that fatigue lives of the sharp notched specimens of high strength steels the tensile strength of which was higher than 1000MPa, could be estimated only by the stress intensity factor and did not depend on the tensile strength. This result indicates that the fatigue life of the sharp notched specimen is controlled by macro fatigue crack growth rate under small scale yielding. It is well known that macro fatigue crack growth rate under small scale yielding depend on Young's modulus. Therefore, the relationship between the fatigue life and the stress intensity factor of the sharp notched specimen is thought to depend on Young's modulus. In this study, K-N curve of metallic glass and non-ferrous alloys were compared with that of high strength steels and E dependent fatigue of sharp notched specimen was experimentally verified. Its importance on fatigue design of machine and structure using high strength light alloys was discussed and future development was suggested.

Fe-based bulk metallic glasses used for magnetic shielding

The casting in complex shapes (tubullar) and the main magnetic properties of bulk metallic glasses (BMG) alloys from the ferromagnetic Fe-Cr-Ni-Ga-P-Si-C system, with a small adittion of Ni (3%) were studied. Samples as rods and sockets having the thickness up to 1 mm were obtained from master alloys by melt injection by low cooling rates into a Cu mold and annealed in order to ensure adequate magnetic requirements. The structure was examined by X-ray diffraction (XRD) and the basic magnetic properties (coercivity, magnetic remanence, initial susceptibility, etc.) were determined by conventional low frequency induction method. The experimental investigations on producing of BMG ferromagnetic alloys with 3% Ni show the possibility to obtain magnetic shields of complex shape with satisfactory magnetic properties. The presence of Ni does not affect the glass forming ability, but reduce the shielding capacity.

Bulk metallic glass coating of polymer substrates

Bulk Metallic Glass (BMG) alloy with the composition of Zr55Cu30Al10Ni5 was deposited by sputtering as thin films on several different engineering polymers and polymer composites. Polycarbonate, polymethyl methacrylate, polyamide 12, polyarylamide (50GF=50 % glass fibers), polyphenylene sulfide (30GF) and polybutylene terephthalate (30GF) were used as substrates. The microstructure of the deposited BMG coatings was studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results of XRD and SEM studies were consistent with amorphous microstructure. Elemental compositions of the coatings were verified by energy dispersive spectroscopy (EDS). Mechanical properties of the coatings were compared to copper mould cast BMG using nano- indentation tests with similar results. According to the cross-cut tape tests good adhesion was achieved between the studied BMG alloy and all other polymer substrates except polycarbonate. Nano-indentation results showed similar mechanical properties for coating and cast BMG. The results of this study look promising as they open new opportunities for BMG- polymer composite applications.

圧力付加液相焼結法による Fe 系金属ガラス-Pd 系金属ガラス複合材の作製

To consolidate [(Fe0.5Co0.5)0.75Si0.05B0.2]96Nb4 metallic glass powder to full density, a pressurized liquid phase sintering was employed, which was intended to promote densification by an enhanced wetting of a liquid phase with solid particles. Pd42.5Ni7.5P20Cu30 metallic glass powder, which has been reported to have a high glass forming ability and the lowest critical cooling rate of glass formation of 0.067 K/s, was chosen a liquid phase component. The melting point of the Pd42.5Ni7.5P20Cu30 metallic glass alloy of 763 K is lower than the glass transition temperature of the [(Fe0.5Co0.5)0.75Si0.05B0.2]96Nb4 metallic glass alloy of 808 K. However, the wettability of this alloy with the Pd42.5Ni7.5P20Cu30 alloy was revealed to be poor. Therefore, sintering pressure was applied to the compacts to promote a viscous flow deformation of solid particles and also to enhance the intergranular permeation of the liquid phase. A specially designed micro-hot press was devised for the pressure-sintering experiment. A pseudo wettability was observed during pressure-sintering, and the liquid phase was found to fill completely the intergranular space of the powder compact. The relative density of 64-95%, as well as the sintering structure, could be controlled by the punch displacement to squeeze out a part of the liquid phase from the compact. The compressive fracture strength of the obtained metallic glass composite was found to be as high as 2051 MPa, and the fracture was observed to be intragranular type, suggesting a good bonding in the particle-binding phase interface.

Fabrication of gapless dual-curvature microlens as a diffuser for a LED package

The light-emitting diode (LED) has been the subject of much interest in the role of a backlight module for liquid crystal displays (LCDs). However, a traditional LED lamp is a point-light source, and so is not suitable for use in large LCD panels. This study presents a new packaging method for LEDs, which uses a gapless dual-curvature microlens array (GDMLA) to improve its ability to illuminate a panel. GDMLAs of different dimensions were simulated and fabricated in order to examine their light luminance and uniformity. Commercial optical simulation software, “Tracepro”, was used to obtain a GDMLA of optimized geometry and dimensions. Based on the simulated data, a GDMLA mold was first fabricated using a LIGA-like process (Lithographie Galvanoformung Abformung, LIGA); this was known as the first mold. In this study, the first mold was obtained using a nickel cobalt (Ni–Co) electroplating process. In order to obtain a highly accurate and strong mold, a bulk metallic glass (BMG) alloy, Mg 58Cu 31Y 11, was chosen as the material for the second mold, which exhibits excellent forming ability and high hardness. The pattern of the first mold was replicated onto BMG by hot-embossing, and the shrinkage between the first and the second mold was less than 0.2%. Next, the pattern of the GDMLA on the second mold was replicated onto ultraviolet (UV)-curable resin, producing the final optical film for a LED package. The shrinkage between the second mold and the UV-cured optical film was less than 0.4%; this means that the process exhibits a high replication ability. The fabricated GDMLA had the characteristics of dual curvatures and a high fill-factor of 100%. The light uniformity of the LED package with the GDMLA optical film was measured, and the results demonstrated that the GDMLA is a good optical device for use in LED packages. In addition, the relationship between the simulation and experimental results is assessed and discussed.

Wetting of Polycrystalline α-Al2O3 by Molten Zr55Cu30Al10Ni5 Metallic Glass Alloy

The wetting behaviors of molten Zr55Cu30Al10Ni5 metallic glass alloy on polycrystalline α-Al2O3 substrates were investigated using a modified sessile drop method at 1133 to 1193 K in vacuum. Excellent wettability with final contact angles approaching zero degree and mild interfacial reaction were observed. The spreading followed a well-defined exponential decay law. It is the Zr adsorption at the interface and then formation of a Zr-Cu precursor film rather than the interfacial reaction that accounts for the excellent wettability in this system.

Effect of hydrostatic pressure on the decomposition behavior of Cu 54Zr 22Ti 18Ni 6 bulk metallic glass alloy in supercooled liquid region

The effect that hydrostatic pressure has on the decomposition behavior in Cu 54Ni 6Zr 22Ti 18 bulk metallic glass (BMG) alloy was assessed using samples, which were isothermally annealed in the supercooled liquid region (SLR) with and without application of hydrostatic pressure. During subsequent annealing for the thermal analysis, the samples annealed under hydrostatic pressure displayed a slower crystallization process in the SLR, which is attributed to a retarded compositional decomposition of the BMG alloy under pressure.

Comparison of Crevice Corrosion of Fe-Based Amorphous Metal and Crystalline Ni-Cr-Mo Alloy

The crevice corrosion behaviors of an Fe-based bulk metallic glass alloy (SAM1651) and a Ni-Cr-Mo crystalline alloy (C-22) were studied in 4M NaCl solution at 100 °C with cyclic potentiodynamic polarization and constant-potential tests. The corrosion damage morphologies, corrosion products, and the compositions of corroded surfaces of these two alloys were studied with optical three-dimensional reconstruction, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and Auger electron spectroscopy (AES). It was found that the Fe-based bulk metallic glass (amorphous alloy) SAM1651 had a more positive breakdown potential and repassivation potential than crystalline alloy C-22 in cyclic potentiodynamic polarization tests and required a more positive oxidizing potential to initiate crevice corrosion in constant-potential tests. Once crevice corrosion initiated, the corrosion propagation of C-22 was more localized near the crevice border compared to SAM1651, and SAM1651 repassivated more readily than C-22. The EDS results indicated that the corrosion products of both alloys contained a high amount of O and were enriched in Mo and Cr. The AES results indicated that a Cr-rich oxide passive film was formed on the surfaces of both alloys, and both alloys corroded congruently in the crevice corrosion damage areas.