Metallic Glass Surface Research Articles

Structural color of metallic glass through picosecond laser

Abstract The alteration in surface color of metallic glasses (MGs) holds great significance in the context of microstructure design and commercial utility. It is essential to accurately describe the structures that are formed during the laser and color separation processes in order to develop practical laser coloring applications. Due to the high oxidation sensitivity of La-based metallic glass, it can broaden the color range but make it more complex. Structure coloring by laser processing on the surface of La-based metallic glass can be conducted after thermoplastic forming. It is particularly important to clarify the role of structure and composition in the surface coloring process. The aim is to study the relationship between amorphous surface structural color, surface geometry, and oxide formation by laser processing in metallic glasses. The findings revealed that the periodic structure primarily determines the surface color at laser energy densities below 1.0 J/mm2. In contrast, the surface color predominantly depends on the proportion of oxides that are formed when energy densities exceed 1.0 J/mm2. Consequently, this study provides a novel concept for the fundamental investigation of laser coloring and establishes a new avenue for practical application.

Ultrafast laser-induced topochemistry on metallic glass surfaces

Manufacturing multifunctional nanocomposite materials and engineered surface nanopatterns involves a strategic blend of topography, crystal structures, and chemistry. Here, we report the controllable formation of crystalline nanoparticles and intermetallic compounds on thin films of metallic glasses (Zr50Cu50, Ti50Cu50, and Zr67Ag33) irradiated by ultrafast laser beams. Mapping the structural modification of the photoexcited and subsequently heated alloys reveals previously neglected chemical reactions with air, offering a direct solution for incorporating nanoparticles into an amorphous oxide matrix and broadening the range of laser-induced surface self-organization features. Our findings are attributed to the occurrence and enrichment of oxygen surface contamination that reacts with selected elements of the metallic glasses. Additionally, the growth of the crystalline phase from undercooled liquid may originate from the dissolution of oxides. Finally, our results establish that the combination of crystalline nanoparticles on amorphous periodic patterns can be universally obtained in a wide range of binary systems of irradiated metallic glasses.

Sputtered zirconium based metallic glassy thin films onto electrospun PCL nanofibrous scaffolds for enriching bioactivity

Surface modification of electrospun Polycaprolactone (PCL) nanoscaffold is to enhance surface properties, particularly bioactivity. In this paper, electrospinning was employed to produce PCL nanoscaffolds and enhancing the bioactivity of the electrospun PCL scaffolds by sputtering of Zirconium based thin film metallic glasses (Zr -TFMGs). The Energy Dispersive Spectroscopy (EDS) analysis exhibited the presence of Zr, Ti and Si and surface topography by Atomic Force Microscopy (AFM) revealed the smooth surface of metallic glasses with nanofibrous structures. The sputtered samples were subjected to immersion test in Simulated Body Fluid (SBF) to analyze the apatite forming ability of Zr–Ti–Si metallic glasses. After 21days of incubation, SEM clearly showed the spherical structures of apatite formed on the surface of modified electrospun PCL. Cell viability studies using L929 fibroblast cells indicates the higher proliferation rate for the Zr based TFMG sputtered PCL scaffold specimen than the uncoated neat PCL scaffold and indicating the bioactive nature of Zr based TFMG. Contact angle of TFMG sputtered sample exhibited the hydrophobic surface which is helpful in preventing the biomedical devices from blood coagulation.

Surface modification with Cu on Zr-based metallic glass using laser cladding and improvement of solder wettability

Zr55Al10Ni5Cu30 metallic glass (bulk amorphous alloy) has unique properties, such as highly resistant to corrosion, high strength and elastic deformation over whole deformation range, so that it is expected to be the next-generation engineering materials. To develop further industrial applications, joining technology for the metallic glass is necessary. In this study, surface modification with Cu on Zr55Al10Ni5Cu30 metallic glass using laser cladding and the consequent solderability improvement were studied. As a result, the interface between Cu foil and Zr55Al10Ni5Cu30 metallic glass were continuously welded by the laser cladding. XRD showed that there are no crystalline and reaction layer in the weld interface. Furthermore, it was found, by XPS, that the Cu-modified layer on the Zr55Al10Ni5Cu30 metallic glass surface inhibited the formation of a strong oxide film. Consequently, the Cu-modified layer played an important role in improving the solderability to the Zr55Al10Ni5Cu30 metallic glass.

Simultaneous flattening and hardening of laser shock peened Zr-based metallic glass surface by nanosecond laser irradiation in a flowing nitrogen atmosphere

Laser shock peening (LSP) is an ideal surface modification technique which has been extensively applied to improve the room-temperature plasticity of metallic glasses (MGs) by generating extra-deep compressive residual stress region and increasing the free volume content. Nevertheless, after LSP treatment, the surface quality and hardness of MGs are usually impaired simultaneously, which hinders their applications as structural and functional materials. In the current study, an attempt was made to achieve simultaneous flattening and hardening of LSP treated (LSPed) Zr-based MG by nanosecond laser irradiation in a flowing nitrogen atmosphere. The effects of laser power level on the macro- and micro-morphology, chemical composition, surface hardness, and surface roughness (Sa) of the laser-irradiated LSPed MG were comprehensively investigated. It was found that the minor surface defects of the LSPed MGs could be effectively reduced by nanosecond laser irradiation under appropriate laser irradiation parameters, and accordingly, the surface quality was improved (with a maximum reduction in surface roughness (Sa) by 86.3%). Furthermore, the nanoindentation test results indicated that nanosecond laser irradiation at a relatively high laser power of 15.6 W resulted in an impressive improvement (173.9%) in surface hardness of the LSPed MG, which could be attributed to the introduction of hard nitrided phases mainly consisting of Zr3N4. This study provides an insightful understanding of the microstructure changes and surface characteristics of the LSPed MGs after nanosecond laser irradiation in a flowing nitrogen atmosphere, which paves the way for improving the applicability of MGs as structural and functional materials.

ZrO2 Superhydrophobic Coating with an Excellent Corrosion Resistance and Stable Degradation Performance on Zr-Based Bulk Metallic Glass.

Photocatalysis is an energy-saving and high-efficiency green environmental technology. Because of its wide band gap and low light utilization, few studies have been conducted on ZrO2 used as a photocatalytic material. In this paper, a corrosion-resistant superhydrophobic ZrO2 coating was prepared on the surface of Zr-based bulk metallic glass by electrochemical etching. This coating not only showed a better corrosion resistance and easier collection, but also presented a stable degradation performance when combined with H2O2; these characteristics are necessary for photocatalysts to survive under harsh environments. This study provides a new direction for designing superhydrophobic surfaces on bulk metallic glass that possess a functional performance.

Laser polishing and simultaneous hardening of the electrical discharge machined Zr-based metallic glass surface

Wire electrical discharge machining (WEDM) is highly suitable for processing the hard-brittle materials like metallic glasses (MGs). However, the electro-thermal energy conversion involved in the WEDM process inevitably introduces some surface defects including bulges, discharge craters, and recast materials on the WEDMed MG surface, which significantly impedes its practical application. Here, an emerging automated polishing technology, laser polishing (LP), was performed in the nitrogen-rich environment to simultaneously improve the surface quality and hardness of the WEDMed Zr-based MG surface. The detailed effects of LP parameters on the surface roughness and morphology were systematically investigated. The morphology evolution and temperature distribution of the molten pool during LP were analyzed by simulation analysis. The experimental results indicated that after single LP of four representative WEDMed Zr-based MG surfaces using the optimized laser parameters, the surface roughness (Sa) was remarkably reduced from 1.27, 2.10, 3.49, and 4.58 μm to 0.09, 0.14, 0.17, and 0.21 μm, respectively, accompanied by an increase in surface hardness from 6.30 GPa to 7.39, 7.67, 8.51 and 8.99 GPa. This study demonstrated that LP could effectively achieve simultaneous enhancement of the quality and hardness of WEDMed MG surfaces, which would contribute to expanding the application prospects of MGs.

Microscopic deformation mechanism and residual plastic accumulation in cross-connection area in nano-grooving process of Zr-based metallic glass

Metallic glass plays a significant role in precision micro-molding and has increasingly gained attention in surface micro-nano structure processing technology. However, the current cutting processes of metallic glass surface micro/nanostructures are still facing several issues, such as burrs and defects. The research on surface structure defects at the nanoscale, specifically residual plastic accumulation in the cross-connection area (PACA), has not been explored. This paper analyzes the material removal process of a nano-groove from the Cu-Zr metallic glass surface, along with the deformation and chip separation mechanism under nanoscale conditions. The results indicate that there are no burrs or defects in cross-areas of surface micro/nanostructures for nano-scale cutting depths. PACA is identified as the primary factor that affects shape accuracy of nanometer microstructures. The study also clarifies the influences of machining parameters (such as tool geometry, workpiece temperature, and cutting process repeats) on material removal process and provides an optimization scheme for solving PACA in cross-areas. These findings offer direct theoretical guidance in understanding the material shear deformation mechanism and chip separation process of Cu-Zr metallic glass during the nano-grooving process, which will aid in solving PACA in cross-areas.

Achieving superhydrophobicity of Zr-based metallic glass surface with anti-corrosion and anti-icing properties by nanosecond laser ablation and subsequent heat treatment

Water repellency of superhydrophobic surfaces offers an opportunity to enhance the corrosion and icing resistance of metallic glasses (MGs). Inspired by the “lotus effect” in nature, hierarchical micro/nanostructures were constructed on a Zr-based MG surface using nanosecond laser ablation. By subsequent heat treatment in air, the structured surface showed a water contact angle (CA) of 168.2 ± 1.5° and a sliding angle (SA) of 4 ± 0.7° (adhesion force of 9.8 ± 1.7 μN), exhibiting repellency and low adhesion to water. Specifically, the superhydrophobic surface stored in air and immersed in water possessed stability and durability, and the superhydrophobic surface still maintained superhydrophobicity after mechanical scratching. The heat treatment temperature worked as a switch for controlling the wettability transition, and by tuning the temperature, the structured surface can switch from superhydrophobicity (CA: 168.2 ± 1.5°) to superhydrophilicity (CA: ~0°). Furthermore, compared to the polished MG surface, the superhydrophobic surface increased the corrosion resistance and freezing time, and delayed the freezing temperature. This study provides a facile non-fluorinated method for fabricating superhydrophobic MG surfaces with anti-corrosion and anti-icing properties, which would enhance the application of MGs as structural and functional materials under extreme conditions.

Surface hardness and scratch characteristics of nanosecond laser colored Ti-based metallic glass

Pulsed laser irradiation is widely used for coloring metallic glass (MG) surfaces due to its efficient and clean processing characteristics. However, the hardness and tribological properties of laser colored MG surfaces have rarely been studied. In this study, various colors were prepared on Ti-based MGs by nanosecond pulsed laser irradiation, and the mechanical properties of the colored surfaces were subsequently investigated. Before hardness testing, the colored surfaces were slightly polished and characterized for surface morphology and phase composition. The hardness of the colored surfaces was measured by a nanoindentation instrument, and the corresponding load depth curves and residual indentations were obtained. The results showed a 39% increase in hardness compared to the as-cast surface. Scratch tests were performed to investigate the tribological properties of the colored surfaces. The residual scratches and three dimensional (3D) topographies exhibited diverse features, and the scratch damage mechanism was analyzed accordingly. This study broadened the knowledge of surface hardness and tribological properties, and illustrated the application potentials of laser colored MGs.

Nanobubbles and physical-mechanical properties of the Ti-Ni-Ta-Si-based metallic glass surface alloy fabricated on a TiNi SMA substrate by additive thin-film electron-beam method

An additive thin-film electron-beam method for the synthesis of micron-thick surface alloys is a promising method for modifying the surface layers of metallic materials. This method allows to functionalize the surface properties (corrosion resistance, radiopacity, biocompatibility), as well as to improve the physical-mechanical properties. The amorphous Ti-Ni-Ta-Si-based surface alloy (~1.6 μm thick) was synthesized by 10-fold alternation of operations of the deposition of an alloying film (Ti60Ta30Si10 (at. %), ~100 nm thick) and the liquid-phase mixing of the [film/substrate] system using a pulsed low-energy high-current electron beam. Spherical nanobubbles (diameter varies from ~2.5 up to ~50 nm) were observed within the surface alloy. The additional electron-beam treatments were used to reduce the concentration of the nanobubbles. The paper presents the results of the influence of the electron-beam treatments on the concentration and size of the nanobubbles, and their in-depth distribution. It was found that the single-step electron-beam treatment effectively reduced the concentration of the nanobubbles and affected on their size and distribution. The two-step electron-beam treatment almost restored the characteristics of the nanobubbles. The influence of the characteristics of the nanobubbles on the strength and elastic-plastic parameters of the amorphous Ti-Ni-Ta-Si-based surface alloy was revealed. The characteristics of the nanobubbles had a major effect on the elastic-plastic parameters of the surface alloy while the strength parameters remained practically the same. It was found that a purposeful change of the characteristics of the nanobubbles is an effective tool for controlling physical-mechanical properties of the amorphous Ti-Ni-Ta-Si-based surface alloy fabricated on a TiNi SMA substrate.

3D morphological analysis of Fe-based metallic glass surfaces via laser powder bed fusion using a digital microscope

3D morphological analysis of Fe-based metallic glass surfaces via laser powder bed fusion using a digital microscope

Defect Engineering of a High-Entropy Metallic Glass Surface for High-Performance Overall Water Splitting at Ampere-Level Current Densities.

Platinum-based electrocatalysts possess high water electrolysis activity and are essential components for hydrogen evolution reaction (HER). A major challenge, however, is how to break the cost-efficiency trade-off. Here, a novel defect engineering strategy is presented to construct a nanoporous (FeCoNiB0.75 )97 Pt3 (atomic %) high-entropy metallic glass (HEMG) with a nanocrystalline surface structure that contains large amounts of lattice distortion and stacking faults to achieve excellent electrocatalytic performance using only 3at% of Pt. The defect-rich HEMG achieves ultralow overpotentials at ampere-level current density of 1000mAcm-2 for HER (104mV) and oxygen evolution reaction (301mV) under alkaline conditions, while retains a long-term durability exceeding 200h at 100mAcm-2 . Moreover, it only requires 81 and 122mV to drive the current densities of 1000 and 100mAcm-2 for HER under acidic and neutral conditions, respectively. Modelling results reveal that lattice distortion and stacking fault defects help to optimize atomic configuration and modulate electronic interaction, while the surface nanoporous architecture provides abundant active sites, thus synergistically contributing to the reduced energy barrier for water electrolysis. This defect engineering approach combined with a HEMG design strategy is expected to be widely applicable for development of high-performance alloy catalysts.

Efficient preparation of multifunctional superhydrophobic surfaces on Zr-based bulk metallic glass by electrochemical machining

It is well known that metallic glasses (MGs) are ideal superhydrophobic substrate materials. However, the preparation methods and application fields of superhydrophobic MGs are presently limited. For the first time, the superhydrophobic layers on both the cathode and anode surfaces of Zr-based bulk metallic glasses (BMGs) were efficiently fabricated through combining the electrochemical etching with electrochemical deposition. The superhydrophobic Cu/Cu2O coating with cauliflower structure on the cathode surface shows excellent photocatalytic and antibacterial performance. In the meantime, the corrosion inhibition rate of the superhydrophobic anode surface reached ∼99.62% and the surface shows good long-term corrosion resistance. This study provides a new horizon for designing superhydrophobic surface on MGs showing mutifunctional performance.

An invivo preclinical study assessing biocompatibility of Pd-based bulk metallicglass.

The bulk metallic glass (BMG), Pd79Ag3.5P6Si9.5Ge2, has a high fracture toughness and has been found to accommodate post-yield stress, unlike most other BMG. Moreover, due to its greater noble gas composition it has a intrinsic corrosion resistance, ideal for dental and orthopedic implants. This present study aimed to evaluate the invivo application of Pd79Ag3.5P6Si9.5Ge2 in a large translational sheep model to assess its efficacy to be utilized as an endosteal device. Twelve implants in the form of cylindrical rods (3 mm in diameter) were produced through rapid quenching. Each sheep (n = 12) received one osteotomy in the mandibular region using rotary instrumentation, which was filled with Pd79Ag3.5P6Si9.5Ge2. After 6- and 24-weeks the animals were euthanized, and samples collected en bloc to conduct histomorphometric analysis. The degree of osseointegration were assessed through bone-to-implant contact (BIC). All samples revealed favorable BIC along with with fibrous connective tissue layers at both 6- and 24-weeks. Bone along with interfacial remodeling was observed in proximity with the metallic glass surface at 6 weeks with higher degrees of bone organization being observed at the later healing time, 24 weeks. The synthesized BMG, given its unique combination of toughness and strength, revealed potential to serve as an alternative to commonly used Ti alloys.

Experimental Study for Yield Surface of Metallic Glass and Methods

The yield surface, the mechanical properties and our experimental methods for Zr55Al10Cu30Ni5 metallic glass are explained. The deformation behavior and the yield stress of this material changes for environmental temperature because of its obvious temperature dependency. The effect of normal stress on its yield can be revealed with increasing temperature and the yield surface closes a typical shape based on the Mohr-Coulomb yield criterion. This material also has an obvious strain rate dependency. The experimental study of the influence of deformation speed on the yield surface and function of this material will be important for a practical application of this material under dynamic load in hot environment.

The scratch characteristics of laser nitrided Zr-based metallic glass surface

Improving the surface hardness and tribological characteristics of metallic glasses (MGs) is meaningful for their applications as surface contact materials. In this study, nanosecond laser nitriding was performed on Zr-based MG to improve its surface properties. Three types of laser nitrided surfaces with different hardness were prepared, and their tribological characteristics were systematically investigated by means of the scratch test. The experimental results indicated that compared with the as-cast MG, the hardness of these three laser nitrided surfaces was increased by 47.94%, 114.56%, and 171.99%, and their coefficients of friction were reduced by 29.12%, 65.05%, and 71.84%, respectively. Furthermore, the residual scratches and surrounding chips exhibited various features under different conditions, and the scratch damage mechanisms were analyzed accordingly.

Cup-cone statistical investigation assess the relationship between the micro-structure and spall strength of metallic glasses under planar impact loadings

Modern industries including the aircraft, rail transportation, and military equipment necessitate a thorough grasp of the dynamic fracture process of materials. Metallic glass, as a typical high-performance modern material, has a broad application prospect in these areas. However, its trans-scale damage evolution process is still shrouded in veil. In this work, we conducted systematic dynamic loading experiments to investigate a distinctive “cup-cone structure” phenomenon that emerges on fracture surface of metallic glass as the impact energy increases. We proposed a new approach of statistical analysis centred on the idea of neighbouring nucleation sites. On the basis of this defect statistical technique, the correlation between the initial nucleation density and spall strength was clarified. The result implies that the macro response does not provide a complete picture of the information regarding the evolution of microstructure. In addition, the meso statistical analysis can play a greater role in establishing the structural-performance correlation.

Deposition of biomimetic biocompatible oxides on metallic glass surface by electro‐discharge coating process

AbstractBulk metallic glass demonstrates superior mechanical properties and excellent bio‐mechanical stability compared to routinely used biomaterials like titanium, cobalt‐chromium, stainless steel, et cetera. However, the metallic glass surface do not easily adhere to the leaving tissues due to native bio‐inert oxide layer, which have poor wear resistance and low hardness. In this current study an innovative method for surface coating of bulk metallic glass by mixing hydroxyapatite powder during electro‐discharge machining has been employed. A biomimetic nano‐porous bio‐ceramic layer of oxides and carbides was deposited on metallic glass surface. The modified surface integrity and composition were investigated by scanning electron microscopy, energy‐dispersive x‐ray spectroscopy, and x‐ray diffraction characterization techniques. The characterization results confirmed the formation of a natural bone‐like nano‐porous surface topography on the metallic glass surface using a novel hydroxyapatite‐mixed electro‐discharge coating process. In addition, a favourable surface chemistry in the form of bioceramic carbides (zirconium carbide, titanium carbide) and zirconium oxide layers, was achieved.

A comparative study on mechanical polishing and laser polishing of laser-nitrided Zr-based metallic glass surface

A comparative study on mechanical polishing and laser polishing of laser-nitrided Zr-based metallic glass surface