Amorphous Metallic Materials Research Articles

Machine learning-guided exploration and experimental assessment of unreported compositions in the quaternary Ti-Zr-Cu-Pd biocompatible metallic glass system

Due to their outstanding elastic limit, biocompatible Ti-based bulk metallic glasses (BMGs) are candidate materials to decrease the size of medical implants and therefore reduce their invasiveness. However, the practical use of classical Ti-BMGs in medical applications is in part hindered by their high copper content: more effort is thus required to design low-copper Ti-BMGs. In this work, in line with current rise in AI-driven tools, machine learning (ML) approaches, a neural-network ML model is used to explore the glass-forming ability (GFA) of unreported low-copper compositions within the biocompatible Ti-Zr-Cu-Pd system. Two types of models are trained and compared: one based on the alloy composition only, and a second based on various features derived from the alloying elements. Contrary to expectation, the predictive power of both models in evaluating GFA is similar. The compositional space identified by ML as promising is experimentally assessed, finding unfortunately low GFA. These results indicate that the ML approach may be premature for specific composition tuning of amorphous metallic materials. We emphasise that the development of ML tools in GFA prediction requires an improvement of the dataset, in terms of homogeneity, size and GFA descriptors, which must be supported by increased reporting of high-quality experimental GFA measurements, both positive and negative. Statement of significanceBiocompatible Ti-based bulk metallic glasses (BMGs) are candidate materials for use in the next generation of minimally invasive dental implants where improved mechanical properties, such as high strength are required. Despite promising in vitro/vivo evaluations, implementation of alloys for practical applications is partly hindered by the presence of copper as the main alloying element. Recent studies have presented AI-guided and machine learning strategies as appealing approaches to understand and describe the glass forming ability (GFA) of BMG-forming compositions. In this work, we employ and evaluate the capacity of a machine-learning model to explore low-copper compositional spaces in the biocompatible Ti-Zr-Cu-Pd system. Our results highlight the limits of such a computational approach and suggest improvements for future designing routes.

Latest Advances in Manufacturing and Machine Learning of Bulk Metallic Glasses

In this review, two interrelated areas are focused on for the development of novel amorphous metallic alloys, namely, materials processing and machine learning techniques for the design of new alloy compositions. Findings, barriers, and opportunities are described, targeting powder production and sintering, additive manufacturing, and postprocessing techniques, followed by the latest developments in artificial intelligence algorithms for both the design of new alloys and for alloy classification tasks.

Enhancement of Interfacial Hydrogen Interactions with Nanoporous Gold-Containing Metallic Glass.

Contrary to the electrochemical energy storage in Pd nanofilms challenged by diffusion limitations, extensive metal-hydrogen interactions in Pd-based metallic glasses result from their grain-free structure and presence of free volume. This contribution investigates the kinetics of hydrogen-metal interactions in gold-containing Pd-based metallic glass (MG) and crystalline Pd nanofilms for two different pore architectures and nonporous substrates. Fully amorphous MGs obtained by physical vapor deposition (PVD) co-sputtering are electrochemically hydrogenated by chronoamperometry. High-resolution (scanning) transmission electron microscopy and corresponding energy-dispersive X-ray analysis after hydrogenation corroborate the existence of several nanometer-sized crystals homogeneously dispersed throughout the matrix. These nanocrystals are induced by PdHx formation, which was confirmed by depth-resolved X-ray photoelectron spectroscopy, indicating an oxide-free inner layer of the nanofilm. With a larger pore diameter and spacing in the substrate (Pore40), the MG attains a frequency-independent impedance at low frequencies (∼500 Hz) with very high Bode magnitude stability accounting for enhanced ionic diffusion. On the contrary, on a substrate with a smaller pore diameter and spacing (Pore25), the MG shows a larger low-frequency (0.1 Hz) capacitance, linked to enhanced ionic transfer in the near-DC region. Hence, the nanoporosity of amorphous and crystalline metallic materials can be systematically adjusted depending on AC- and DC-type applications.

Mechanical, Electromagnetic, and Tribological Properties of Microspirals Made from Amorphous and Crystalline Metallic Materials

Mechanical, Electromagnetic, and Tribological Properties of Microspirals Made from Amorphous and Crystalline Metallic Materials

Aluminum Alloy Matrix Composite Reinforced with Metallic Glasses Particles Using Hot-Roll Bonding

Composite materials (CMs) exhibit high hardness, mechanical strength, and wear resistance, but their processing properties are limited. The most popular reinforcements for composites are carbides, nitrides, and oxides. Amorphous metallic materials are an alternative reinforced component. Metallic glass can provide increased properties due to higher interphase strength between their particles and the metallic matrix when compared with nonmetallic particles. A sheet of metal matrix composite has been processed by roll bonding. The composite consists of an aluminum-based matrix reinforced by particles of Co48Cr15Mo14C15B6Tm2 metallic glasses and a cladding layer of AA5083 alloy. The thickness of the central layer of Al–5% Zn–5% Ca alloy reinforced by metallic glasses particles is 60% of the total thickness of the sheet, and the thickness of the cladding layer is 20% on the both sides. Granules of the CM were processed by mechanical alloying with the subsequent consolidation to the balk sheet by roll bonding in clad sheets at the temperature below class transition temperature of the amorphous component. The reinforcement compound retains the amorphous state after mechanical alloying and hot rolling, which is shown by X-ray and differential thermal analysis. The microstructure after different processing steps is studied by scanning electron microscopy and the mechanical properties of the metal matrix composite sheet at room temperature are studied. Amorphous particles have a size range of 2 to 187 μm and volume fraction of about 10%. The hardness of the composites is 25% higher than the hardness of basic alloy Al–5% Zn–5% Ca. The yield strength of the cladded CM is two times higher than that of metallic alloys of the matrix and cladding.

Ti-Zr-Si-Nb Nanocrystalline Alloys and Metallic Glasses: Assessment on the Structural Development, Thermal Stability, Corrosion and Mechanical Properties.

The development of novel Ti-based amorphous or β-phase nanostructured metallic materials could have significant benefits for implant applications, due to improved corrosion and mechanical characteristics (lower Young’s modulus, better wear performance, improved fracture toughness) in comparison to the standardized α+β titanium alloys. Moreover, the devitrification phenomenon, occurring during heating, could contribute to lower input power during additive manufacturing technologies. Ti-based alloy ribbons were obtained by melt-spinning, considering the ultra-fast cooling rates this method can provide. The titanium alloys contain in various proportions Zr, Nb, and Si (Ti60Zr10Si15Nb15, Ti64Zr10Si15Nb11, Ti56Zr10Si15Nb19) in various proportions. These elements were chosen due to their reported biological safety, as in the case of Zr and Nb, and the metallic glass-forming ability and biocompatibility of Si. The morphology and chemical composition were analyzed by scanning electron microscopy and energy-dispersive X-ray spectroscopy, while the structural features (crystallinity, phase attribution after devitrification (after heat treatment)) were assessed by X-ray diffraction. Some of the mechanical properties (hardness, Young’s modulus) were assessed by instrumented indentation. The thermal stability and crystallization temperatures were measured by differential thermal analysis. High-intensity exothermal peaks were observed during heating of melt-spun ribbons. The corrosion behavior was assessed by electrocorrosion tests. The results show the potential of these alloys to be used as materials for biomedical applications.

Quasi-Amorphous Metallic Nickel Nanopowder as an Efficient and Durable Electrocatalyst for Alkaline Hydrogen Evolution.

Nickel is regarded as the best alternative metal electrocatalyst to platinum for hydrogen evolution reaction (HER). Success in developing a quasi‐amorphous metallic nickel (QAMN) nanopowder catalyst using a two‐step chemical route for efficient and durable HER in alkaline solution is reported. It is found that the QAMN electrocatalyst exhibits essentially zero overpotential at the cathodic onset while delivering 10 mA cm−2 at an overpotential of only 240 mV; both performances are far better than what was reported previously using prior metallic nickel catalysts. Taking into account increased surface area, further enhanced activity is attributed to the superior intrinsic activity. Meanwhile, the QAMN catalyst shows excellent stability in accelerated and interrupted polarization in alkaline solution for tens of hours. This study provides a new chemical means to prepare amorphous metallic materials for more efficient catalysis.

Optical properties of surface layers of amorphous and polycrystalline metallic materials modified by laser and ion implantation treatment

Optical properties of surface layers of amorphous and polycrystalline metallic materials modified by laser and ion implantation treatment

Preparation of Magnesium-zinc Alloy by Mechanical Alloying

Mechanical alloying is one of the ways how to prepare nanostructured and amorphous metallic materials. In this paper we used this method to prepare Mg-Zn alloy containing 50 wt.% of zinc. Powders produced by milling in a planetary ball mill were consequently compacted by the SPS method, a very fast method which prevents grain coarsening. The prepared samples were subjected to a closer examination - microstructure, phase composition, hardness and short-term thermal stability were studied. We found out that the prepared powder consisted of Mg and Mg7Zn3 phases, which were very fine and homogeneously distributed. After the SPS compacting, the metastable Mg7Zn3 phase decomposed and new phases (Mg, MgZn, MgZn2, Mg2Zn11) formed. The compacted sample possessed relatively inhomogeneous microstructure and hardness about 260 HV5. Investigation of the short-term thermal stability was accomplished by annealing at temperatures up to 300 °C. We observed changes in hardness - it regularly decreased up to 200 °C and then it slightly increased.

ChemInform Abstract: High‐Strength and High‐Ductility Nanostructured and Amorphous Metallic Materials

AbstractReview: 50 refs.

Nanostructures: High‐Strength and High‐Ductility Nanostructured and Amorphous Metallic Materials (Adv. Mater. 31/2014)

Nanostructures: High‐Strength and High‐Ductility Nanostructured and Amorphous Metallic Materials (Adv. Mater. 31/2014)

High-strength and high-ductility nanostructured and amorphous metallic materials.

The development of materials with dual properties of high strength and high ductility has been a constant challenge since the foundation of the materials science discipline. The rapid progress of nanotechnology in recent decades has further brought this challenge to a new era. This Research News highlights a few newly developed strategies to optimize advanced nanomaterials and metallic glasses with exceptional dual mechanical properties of high strength and high ductility. A general concept of strain non-localization is presented to describe the role of multiscale (i.e., macroscale, microscale, nanoscale, and atomic scale) heterogeneities in the ductility enhancement of materials reputed to be intrinsically brittle, such as nanostructured metallic materials and bulk metallic glasses. These nanomaterials clearly form a new group of materials that display an extraordinary relationship between yield strength and the uniform elongation with the same chemical composition. Several other examples of nanomaterials such as those reinforced by nanoprecipitates will also be described.

Determination of trace metal release during corrosion characterization of FeCo-based amorphous metallic materials by stripping voltammetry. New materials for GMI biosensors

The objective of this investigation has been the study of metal release during corrosion characterization of Fe2.5Co64.5Cr3Si15B15, Fe3Co67Cr3Si15B12 and Fe5Co70Si15B10 amorphous metallic alloys, used as based materials to create new type for giant magnetoimpedance (GMI) biosensors. Alloy samples were tested in phosphate buffered saline solutions (PBS, artificial biological solutions) at pH 7.4 and 22 °C. Individual alloy constituents (Fe, Co, Cr, B) released during the electrochemical corrosion tests, were analyzed by differential pulse stripping voltammetry (DP) using a hanging mercury drop electrode technique (HMDE). In this work, the experimental results obtained are discussed in order to study their corrosion behavior in artificial biological solutions and thus determine their possible use as GMI biosensor prototype materials.

Thermodynamic approach to quantitative assessment of propensity of metallic melts to amorphization

On thermodynamic grounds, it was found that key properties that control the capacity of molten metallic alloys for transition into an amorphous state are the excess (configurational) entropy and heat capacity of the liquid. Chemical short-range order in liquids exhibiting various ten-dencies to glass formation was analyzed on the basis of the associated solution theory and the results of detailed thermodynamic research on a wide set of alloys. An interrelation was established between the association, characteristics of molten alloys (viscosity η, activation energies of viscous flow, and crystallization) that determine the possibility of amorphization and characteristics of glassy state stability (glass transition point, Gibbs energy, and enthalpy of crystallization). It was demonstrated that the magnitude of the key functions is completely determined by the covalent constituent of chemical interaction between components and depends mainly on the entropy terms of association reactions. The prospects for developing the quantitative criteria of amorphization on the basis of the entropy of association was discussed. It was also shown that the suggested approach based on taking into accoun the specificity of chemical interaction between components can be useful for prediction of physical, chemical, and mechanical properties of solid amorphous metallic materials.

Synthesis of Bulk Nanocrystalline Materials by Repeated Cold Rolling

AbstractThe article gives an overview on the preparation and characterization of bulk nanocrystalline or bulk amorphous metallic materials by repeated cold rolling with intermediate folding. The results that are highlighted for pure fcc and hcp metals and one binary glass‐forming alloy indicate that truly nanocrystalline materials with grain sizes below 10 nm can be obtained by this process that does not apply an additional hydrostatic pressure and that is compatible with continuous processing routes.

Structure and Mechanical Properties of ZrCr2Intermetallic Compound within the Temperature Range 20–1300°C

We studied the properties of ZrCr2 intermetallic compound without crystallization cracks, obtained due to the introduction of excess zirconium (up to 2 at. %) with respect to the stoichiometric composition into the alloy. The melt was poured in a copper chill mold, and specimens for mechanical compression tests within the temperature range 900–1300°C were cut out of the castings. The short-term strength of intermetallic compound was σu = 665 and 140 MPa, and fracture took place mainly along the grain boundaries: below 1100°C, it was brittle, but, at higher temperatures (1200–1300°C), the plastic strain reached 5–7% prior to crack initiation and almost 30% before fracture. Plastic deformation is not accompanied by hardening. In the case of transcrystalline fracture, its type can be attributed to “venous,” which is characteristic of amorphous metallic materials.

Atomic-Scale Characterization of Nanostructured Metallic Materials by HAADF/Z-contrast STEM

We demonstrate that high-angle annular-dark-field scanning transmission electron microscopy (HAADF-STEM) with a finely-focusedelectron probe( 0:15nm) is very powerful techniqueto provide direct information on a local chemistry of nano-materials at atomicscale. Thisis due to an atomic-number (Z) sensitive nature of the HAADF contrast (Z-contrast). We describe the microstructures of some crystalline,quasicrystalline and amorphous metallic materials with focusing on their local chemical environments. Not only the chemical Z-contrast,HAADF-STEMpossessesmoresubstantialadvantagescomparedtotheconventionalphase-contrasthigh-resolutionimaging,sothatitwouldbeone of the most powerful methods for total characterization of nano-structured materials.(Received April 23, 2003; Accepted June 19, 2003)Keywords: scanning transmission electron microscope, high-angle annular-dark-field imaging, atomic-resolution Z-contrast, local chemistry,aluminium- and magnesium-alloys

Production of shape memory thin strips by twin roll casting technique

Rapid solidification techniques were first used to obtain amorphous or microcrystalline metallic materials, which required high quenching rates (10 4 -10 6 K.s -1 ). Applied to shape memory alloys, the twin roll casting technique allows semi-finished materials (strips) with reduced grain size to be obtained. This is particularly useful for certains shape memory alloys for which shaping is difficult because of their inherent lack of ductility. The melt is cast through a nozzle and solidified between the gap of two rollers rotating in opposite directions. Optimum conditions must be established to obtain thin foils with a smooth surface, not brittle and free of cracks and holes. It is only possible for a limited combination of the following experimental parameters: roll speed, melt temperature, melt flow, ejection pressure and roll gap. In this work, we have characterized (transformation temperatures, microstructures) copper based and Ni-Ti-Hf strips, with a thickness between 150 and 500 μm. For copper based alloys, it has been found that transformation temperatures were in a similar range to those of conventionnally cast alloys, which is not the case of melt spun ribbons whose transformation temperatures dramatically decrease. For Ni-Ti-Hf strips cast with different conditions, transformation temperatures vary: some are close to the conventionnally solidified material but some others are lower.

Thermodynamics of the NI-ZR melt: Specific features of interatomic interaction and transition into an amorphous state

Nickel–zirconium alloys have a high glass-forming ability in a wide range of concentrations and constitute the basis for a variety of bulky amorphous metallic materials [1]. However, until now, there is no information on the Gibbs energy of the Ni–Zr-melt formation. This fact hampers both the analysis of thermodynamic and kinetic parameters of the transition of the Ni–Zr liquid into an amorphous state and the understanding of the reasons why such a transition easily proceeds in a number of transition metal systems.

アモルファス金属研究の流れ

アモルファス金属研究の流れ