Zirconium-based Metallic Glass Research Articles

Effects of RF Magnetron Sputtering Power on the Mechanical Behavior of Zr-Cu-Based Metallic Glass Thin Films.

Zirconium-based metallic glass films are promising materials for nanoelectronic and biomedical applications, but their mechanical behavior under different conditions is not well understood. This study investigates the effects of radio frequency (RF) power and test temperature on the nanostructure, morphology, and creep behavior of Zr55Cu30Al10Ni5 metallic glass films prepared by RF magnetron sputtering. The films were characterized by X-ray diffraction and microscopy, and their mechanical properties were measured by a bulge test system. The results show that the films were amorphous and exhibited a transition from noncolumnar to columnar morphology as the RF power increased from 75 W to 125 W. The columnar morphology reduced the creep resistance, Young's modulus, residual stress, and hardness of the films. The creep behavior of the films was also influenced by the test temperature, with higher temperature leading to higher creep strain and lower creep stress. The findings of this study provide insights into the optimization of the sputtering parameters and the design of zirconium-based metallic glass films for various applications.

Development of p-type zinc oxide nanorods on zirconium-based metallic glass nanotube arrays by facile hydrothermal method for gas sensing applications

In this study, p-type zinc oxide (ZnO) nanorods grown on zirconium-based metallic glass nanotube arrays were developed for hydrogen gas sensing applications. Heterogeneous zirconium-based metallic glass nanotube arrays were synthesized by sputter deposition of metallic glass (Zr60Cu25Al10Ni5) over contact-hole arrays created using a photoresist template (diameter, 2 µm). To provide nucleation sites for the growth of nanorods inside the zirconium-based metallic glass nanotube arrays, a ZnO seed layer was deposited. ZnO nanorods were grown using the hydrothermal method. The developed p-type ZnO nanorods were systematically characterized, and the reason behind the change from n-type ZnO to p-type ZnO was explained based on experimental findings. The sample was then sputtered with Pt electrodes to obtain a hydrogen sensing device. The fabricated zirconium-based metallic glass nanotube arrays with ZnO nanorods (Zr-ZnO nanorods) exhibited outstanding hydrogen gas sensing property of 28% sensor response at room temperature. Besides, the H2 gas sensing performance of the developed sensor is better than that of the ZnO-based H2 gas sensors in the open literatures. It also presented excellent cyclic and long-term stability, which is crucial for practical applications. The preparation method is also easy, fast, and at low temperatures. Therefore, this study paves the way for the development of p-type ZnO with potential applications in various areas; the developed sensor can be used for environmental remediation and monitoring.

Structure-Element Surface Modification Strategy Enhances the Antibacterial Performance of Zr-BMGs.

Zirconium-based metallic glasses (Zr-BMGs) have attracted tremendous attention in healthcare fields, especially in the design of surgical tools and orthopedic implants, due to their unique amorphous structure; however, the application of Zr-BMG-based medical devices is hindered by bacterial contamination. Here, a structure-element strategy is proposed to improve the antibacterial performance of Zr-BMGs by surface laser nanostructuring and silver nanoparticle (AgNP) deposition. The laser nanostructuring process generates a disordered nanoparticle structure (NP) and laser-induced periodic surface structure (LIPSS) to decrease the surface bacterial adhesion and increase the internal antimicrobial ion release. Moreover, after Ag deposition and hydrogen peroxide (H2O2) treatment, the antibacterial adhesion ability of the Zr-BMG surface can be further improved without any influence on the crystallization of Zr-BMGs and the release of antibacterial copper/nickel (Cu/Ni). The antibacterial effect of the LIPSS and the NP surfaces presents over 90% bacterial killing ratio, which is superior to that of the naked Zr-BMGs with less than 60% bacterial killing ratio. In vitro and in vivo tests show that the Ag-deposited and H2O2-treated LIPSS surfaces exhibit an optimal balance between the antibacterial property and the biocompatibility compared with the polished, NP structured or LIPSS structured surfaces. It is assumed that such structure-element surface modification strategy can improve the antibacterial activity of metal-containing surgical tools and orthopedic implants, improving the success rate of medical treatment.

Zirconium-based metallic glass and zirconia coatings to inhibit bone formation on titanium

Surface-modified commercially pure titanium (Cp-Ti) with zirconium (Zr)-based thin film metallic glasses (Zr-TFMGs) and ZrO2 thin films were surgically implanted into the tibiae of rats; the bone formation was analyzed to examine the performance of the coatings as a biomaterial. Zr-TFMGs and ZrO2 thin films were coated on Cp-Ti substrates to monitor the control of assimilation in vitro and in vivo. The microstructural and elemental analyses were carried out for the as deposited thin films by x-ray diffraction (XRD), transmission electron microscopy and x-ray photoelectron spectroscopy. TFMG- and ZrO2-coated Ti specimens were immersed in simulated body fluid (SBF) for a period of 21 days to evaluate the calcium phosphate precipitation in vitro. XRD, x-ray photoelectron spectroscopy and scanning electron microscopy/energy dispersive x-ray spectroscopy were used to quantify the mineralization on the coated Zr-TFMG and ZrO2. In vitro corrosion studies showed that the Zr-based TFMG and ZrO2 coatings sustained in the SBF, exhibited superior corrosion resistance to the bare crystalline Ti substrate. Wettability studies showed TFMG and ZrO2 coatings with a hydrophobic nature, and the TFMG-coated SBF-submerged specimens showed a hydrophilic nature. The in vitro cell viability of MC3T3-E1 cells showed good cell proliferation and low cytotoxicity. The calcification deposits were evaluated by staining with alizarin red S, which showed a lower calcium formation on Zr-TFMG compared to ZrO2. The present work also aims to assess the assimilation behavior of Cp-Ti, Zr-TFMG and ZrO2 in vivo by inserting the coated specimen in the femur of rats. After post-implantation of 8 weeks, specimens were examined by micro-CT evaluation. The bone contact ratios as calculated were 72.75%, 15.32% and 38.79%. Consequently, the bone affinity was Cp-Ti wire >ZrO2-coated Ti wire >Zr48Cu36Ag8Al8-coated Ti wire.

Surface modification of high-rejection ultrafiltration membrane with antifouling capability using activated oxygen treatment and metallic glass deposition

Polysulfone (PSf) composite ultrafiltration membranes were subjected to Ar/O2 plasma assisted oxygen activation and then coated with various forms of metallic glass (W50Ni25B25, Zr60Cu25Al10Ni5, and Pd74Si14Cu12). The activated oxygen treated PSf ultrafiltration membrane was strongly hydrophilic, with pure water flux (PWF) of 350.7 L m−2 h−1 and bovine serum albumin (BSA) rejection of 83%. The application of metallic glass (MG) to the surface of the polysulfone composite membrane using low-power radio-frequency magnetron sputtering improved the BSA rejection rate (ranging from 98.6 to 99.9%) with only a slight reduction in PWF: tungsten-based MG (321.5 L m−2 h−1), zirconium-based MG (215.6 L m−2 h−1), and palladium-based MG (181.3 L m−2 h−1). The membrane with the tungsten-based coating achieved remarkable PWF, BSA rejection, and antifouling performance, due primarily to high surface hydrophilicity (water contact angle of 24.2°) and a strongly negative surface charge. Overall, the proposed metallic glass/polysulfone composite membranes achieved moderately high PWF and protein rejection with incredible antifouling competence, even under extended (multi-cycle) fouling conditions.

Experimental study on wire-electrical discharge machining of zirconium-based metallic glass

In this paper, the new alloy material, zirconium-based bulk metallic glass (Zr41.2Ti13.8Cu12.5Ni10Be22.5), which is hard and brittle, was the research object. Since the process of wire-electrical discharge machining offers the advantage of processing hard and brittle conductive materials, the effects of discharge parameters on material removal rate, surface roughness, surface morphology, carbonization and crystallization have been studied by changing discharge voltage, peak current and pulse width. The results showed that material removal rate and surface roughness increased with the increase of peak current and pulse width. Compared to peak current and pulse width, voltage exerted a less influence on material removal rate and surface roughness. The surface of the workpiece after processing presented fish-scale structure with some bumps, microspheres and droplets. As the discharge energy increased, more carbon deposits from cutting fluid were deposited on the surface of the workpiece, resulting in an increase of the carbon content which accelerated surface carbonization. The workpiece processed by low discharge energy kept a good amorphous state, but its surface layer had a tendency to crystallize. Furthermore, with the increase of discharge energy, sharp diffraction peaks began to appear, and crystallization occurred. Based on the current inadequacy of research on wire-electrical discharge machining of zirconium-based metallic glass, the purpose of this study is to provide a reference for further research on wire-electrical discharge machining of zirconium-based metallic glass.

Fabrication of optical gratings through surface patterning of zirconium-based metallic glass by laser irradiation

Periodic lines with intervals ranging from ∼220 μm down to ∼27 μm were fabricated on the surface of Zr55Cu30Al10Ni5 metallic glass ribbon and disk samples by laser irradiation. The X-ray diffraction results indicated that both oxides (monoclinic ZrO2, tetragonal ZrO2) and crystallites (Cu10Zr7, NiZr2) existed together with the amorphous phase on the surface of the laser-patterned metallic glass samples. The energy-dispersive X-ray spectroscopy of a cross section of a disk sample clearly showed that high amounts of aluminum (292% of the nominal composition) and oxygen were present in the laser-irradiated area, suggesting that Al2O3 formed on the surface of the laser-irradiated region. Reflective diffraction spots were observed from the fine grids with a grating period of ∼27 μm, indicating the excellent periodicity and accuracy of the pattern in two dimensions on the surface of the metallic glass substrates. Calculation of the grating period using Bragg's law confirmed that the spots originated from the periodic patterns of the laser-irradiated lines. Along the lines, pairs of ridges and hollows with a height/depth of ∼0.5 μm were observed; such specific morphology generated the diffraction spots as a reflective grating. We observed structural color gradation from the periodic fine grids under a fluorescent light. The present study showed that it is possible to prepare optical gratings on the surface of metallic glasses by laser irradiation more cheaply and easily than by conventional imprinting.

Biocompatibility evaluation of sputtered zirconium-based thin film metallic glass-coated steels.

Thin film metallic glasses comprised of Zr48Cu36Al8Ag8 (at.%) of approximately 1.5 μm and 3 μm in thickness were prepared using magnetron sputtering onto medical grade 316L stainless steel. Their structural and mechanical properties, in vitro corrosion, and antimicrobial activity were analyzed. The amorphous thin film metallic glasses consisted of a single glassy phase, with an absence of any detectable peaks corresponding to crystalline phases. Elemental composition close to the target alloy was noted from EDAX analysis of the thin film. The surface morphology of the film showed a smooth surface on scanning electron microscopy and atomic force microscopy. In vitro electrochemical corrosion studies indicated that the zirconium-based metallic glass could withstand body fluid, showing superior resistance to corrosion and electrochemical stability. Interactions between the coated surface and bacteria were investigated by agar diffusion, solution suspension, and wet interfacial contact methods. The results indicated a clear zone of inhibition against the growth of microorganisms such as Escherichia coli and Staphylococcus aureus, confirming the antimicrobial activity of the thin film metallic glasses. Cytotoxicity studies using L929 fibroblast cells showed these coatings to be noncytotoxic in nature.

Effects of residual stress on elastic plastic behavior of metallic glass bolts formed by cold thread rolling

Metallic glass (MG) has unique mechanical properties, combining high strength and low Young's modulus. By using MG to fabricate fasteningbolts, high resistance against bolt loosening is expected. However, MG components are considered brittle because MG exhibits poor ductility when subjected to uniaxial loading at room temperature. We have developed hexagonal cap bolts made of zirconium-based MG by cold thread rolling. The MG bolts showed a 1.6% plastic strain with a tensile strength of more than 1550MPa. In addition, the load–strain curve was similar to that of a strain hardening material, although MG itself is free of strain hardening. In this study, we attempted to clarify the reasons for these characteristics, which are advantageous for bolts in terms of toughness and reliability. Various experiments and numerical analysis indicated that residual stress plays an important role in the behavior.

Investigation and simulation of crystallization of bulk zirconium-based metallic glasses

This article is devoted to the investigation and simulation of the crystallization kinetics of zirconium-based bulk metallic glasses under heating with a constant rate, as well as under isothermal holding at an elevated temperature. The investigation into crystallization kinetics with time can provide a deeper under-standing of the crystallization mechanism of bulk metallic glasses and promote the scientifically substantiated selection of thermal treatment modes to form the desired structure and properties of composite materials on their basis.

Effects of Residual Stress on Elastic Plastic Behavior of Metallic Glass Bolts Formed by Cold Thread Rolling

Metallic glass (MG) has unique mechanical properties, combining high strength and low Young’s modulus. By applying MG to the fabrication of fastening bolts, high resistance against bolt loosening is expected. However, MG components are thought to be brittle because MG exhibits poor ductility when subjected to uniaxial loading at room temperature. We have developed hexagonal cap bolts made of zirconium-based MG by cold thread rolling. The MG bolt showed a 1.6% plastic strain with a tensile strength of more than 1550 MPa. In addition, the load-strain curve was similar to that of a strain hardening material although MG itself is free of strain hardening. In this study, we attempt to clarify the reasons for the behavior, which are advantageous for bolts in terms of toughness and reliability. Various experiments and numerical analysis indicate that residual stress plays an important role in the behavior.

Plastic Working of Metallic Glass Bolts by Cold Thread Rolling

Bolts are commonly employed machine elements used for joining and fastening, and their performance and reliability influence the overall performance of machines. In this study, we have plastically worked and formed bolts using metallic glass (MG) that exhibits unique mechanical properties such as high tensile strength, low Young’s modulus, and large elastic limit. The large elastic limit increases the permissible elongation range of the bolt and helps avoid bolt loosening, while the low Young’s modulus effectively resists screwed-in bolt loosening by increasing the frictional forces on both bolt-nut contact area and bearing surface. We employed a zirconium-based MG Zr55Al10Cu30Ni5 for our experimental investigations. A pre-form of a hexagon socket head cap screw (bolt) was fabricated by squeeze casting. Cold and warm thread rolling were performed to form a metric screw thread M3×0.5 (class 6g (ISO)) below the glass transition temperature (Tg) using a flat rolling machine. Despite the extremely poor ductility of MG at room temperature, thread rolling was successfully performed. Straining behavior analysis by a three-dimensional finite element method demonstrated that these remarkable results are due to the compressive stress distribution induced during the thread rolling process. In addition, thread rolling is fundamentally an incremental process, and it enhances the deformability of MG by gradually improving ductility in the deformed region. The tensile strength of the thread-rolled bolt was approximately 1600 MPa, which is considerably higher than that of conventional heat-treated high strength steel bolts. MG was thus successfully employed to manufacture improved bolts.

Reverse Monte Carlo structural model for a zirconium-based metallic glass incorporating fluctuation microscopy medium-range order data

We used reverse Monte Carlo (RMC) modeling to simulate the atomic structure of a Zr-based bulk metallic glass (BMG), incorporating short-range structural data from the electron diffraction total reduced density functionG(r) and medium-range structural data from fluctuation electron microscopy (FEM). Including the FEM data created within the model loosely ordered planar atomic arrangements covering regions ∼1 nm in diameter without degrading the agreement withG(r). RMC refinement against onlyG(r) produced no agreement with FEM. Improved simulations are needed to create fully realistic BMG structures, but these results show that including FEM in RMC further constrains the structure compared withG(r) data alone and that the FEM signal in real materials is likely to arise from pseudo-planar arrangements of atoms.

The effect of temperature and extrusion speed on the consolidation of zirconium-based metallic glass powder using equal-channel angular extrusion

In this study, gas-atomized amorphous Zr58.5Nb2.8Cu15.6Ni12.8Al10.3 (Vitreloy 106a) containing 1280 ppmw oxygen was consolidated by equal-channel angular extrusion (ECAE). The powder was vacuum encapsulated in copper cans and subjected to one extrusion pass in the temperature region above the glass transition temperature (Tg) and below the crystallization temperature (Tx). The effects of extrusion temperature and the extrusion rate on microstructure, thermal stability, hardness, and compressive strength are investigated. Compression fracture surfaces were examined to determine the deformation mechanisms. The consolidates in which the time-temperature-transformation (TTT) boundary was not crossed during processing exhibit differential scanning calorimetry (DSC) patterns similar to the initial powder, with a slight decrease in Tx. Compressive strengths of about 1.6 GPa are recorded in the consolidates processed at 30 °C and 40 °C below Tx, which is close to what is observed in cast counterparts. The fracture surfaces exhibit vein patterns covering up to 90 pct of the surface area in some samples, which are characteristic of glassy material fracture. The slight decrease in Tx after consolidation is attributed to thermal-history-dependent short-range order and formation of nanocrystalline islands. The present results show that ECAE is successful in consolidation of metallic glass powder. This processing avenue opens a new opportunity to fabricate bulk metallic glasses (BMGs) with dimensions that may be impossible to achieve by casting methods.

Structure of Shear Bands in Zirconium-Based Metallic Glasses Observed by Transmission Electron Microscopy

ABSTRACTWe have used transmission electron microscopy (TEM) to investigate the structure of shear bands produced by bending electron-transparent Zr52.5Cu17.9Ni14.6Al10Ti5metallic glass specimens. Shear bands were located by comparing the structure of the specimens before and after deformation. The shear band spacing is influenced by the structure of the specimen; portions of the specimen with a significant population of nanocrystals show a smaller separation between shear bands. Quantitative high resolution TEM analysis based on ratio technique has been used to explore the defect structure in shear bands. High density and void-like defects with size of about 1 nm were found in shear bands formed in both amorphous and nanocrystalline areas. A simple model was proposed to explain the formation of these defects.

Oxidation of amorphous NiZr sputtered films

In this study the surface oxidation of a number of nickel-rich NiZr alloys is reported as a means to determine its role on the stability of amorphous zirconium-based metallic glasses. The evolution of the oxide layer was monitored by following the nickel and zirconium XPS peaks after exposure to an oxygen pressure of 10 −5 mbar for various periods. The surface of the air-exposed films is characterized as ZrO 2 even for bulk nickel concentrations over 80 at.%. After sputter cleaning, oxidation at room temperature under controlled oxygen exposure results in a several-stage oxidation towards ZrO 2 accompanied by a systematic depletion of the nickel at the surface. This reaction saturates after exposures of the order of several thousand Langmuirs. Throughout this process, nickel remains primarily in a metallic state. There is, moreover, indirect transport evidence that a non-surface nickel-rich layer is produced.

Crystallization of zirconium-based metallic glasses

Any amorphization by solid state reactions is limited by crystallization reactions of the stable intermetallic compounds. Nucleation and crystal growth have been studied systematically in (Fe, Co, Ni)-Zr glasses using transmission electron microscopy. The temperature and time dependences of nucleation and growth rates have been determined and can be used to calculate limiting crystallization diagrams. These results will be compared with the ease of glass formation by solid state reactions.

Transient nucleation in zirconium-based metallic glasses

The nucleation kinetics of zirconium-based metallic glasses has been studied by quantitative electron microscopy. The nucleation behaviour can be derived from crystal size distributions by computer simulations, i.e. by varying the steady state nucleation rate, time lag and number of nucleation sites as fitting parameters. A sufficient condition for such an analysis is a constant, isotropic growth rate as observed during polymorphic crystallization of CoZr 2 or FeZr 2; NiZr 2 exhibits a rather irregular shape. These glasses possess the same activation energy for growth, but growth rates increase significantly in the order Co → Fe → Ni. From crystal size distributions in partially crystallized Co 33Zr 67 or Fe 33Zr 67 glasses it is not possible to distinguish unambiguously between homogeneous or heterogeneous nucleation, but in any case rates are transient and the steady state nucleation rates increase in the sequence Ni → Co → Fe. In contrast to metal-metalloid glasses, the steady state nucleation rate can be described in a wide temperature range around the glass transition temperature by an Arrhenius equation with an activation energy of the same order of magnitude as for zirconium diffusion in CoZr glasses.

New disordered superconductors

We have measured the low temperature resistance of zirconium-based metallic glasses. Superconductivity is found in: Zr 65Cu 35, T c = 2.0 K; Zr 70Ni 30, T c = 2.9 K; and Zr 70Co 30, T c = 3.3 K.