Amorphous Alloy System Research Articles

The new sight to Fe–C system

ABSTRACT The crystalline Fe–C alloy had been the focal point of research in the traditional metallurgical steel industry. However, its corresponding amorphous alloy system had received little attention, with a lack of consensus on the microstructural evolution. Three types of Fe–C unbalanced composite films with different carbon content were fabricated using the magnetron sputtering method. The results indicated that as the carbon content increased, carbon existed in the form of supersaturated solid solution atoms in crystalline Fe, an amorphous Fe–C structure and Fe3C, respectively. The resistivity of the films in these three carbon types gradually increased from 1.37 × 10−4 ohm/cm to 4.53 × 10−2 ohm/cm and then to 5.43 × 10−2 ohm/cm. Simultaneously, the transmittance gradually increased from 0% to 28% and then to 51%. Upon annealing at 400°C, with the crystallisation of Fe in the low-carbon film, unbalanced carbon atoms were pushed out of the lattice and precipitated as Fe3C. After annealing at 650°C, the Fe3C in the high-carbon film decomposed into Fe and C. The as-prepared medium-carbon film displayed commendable corrosion resistance. These findings provided valuable insights for the design and performance development of new materials.

Magnetic Semiconductors from Ferromagnetic Amorphous Alloys

Utilizing both charge and spin degrees of freedom of electrons simultaneously in magnetic semiconductors promises new device concepts by creating an opportunity to realize data processing, transportation and storage in one single spintronic device. Unlike most of the traditional diluted magnetic semiconductors, which obtain intrinsic ferromagnetism by adding magnetic elements to non-magnetic semiconductors, we attempt to develop room temperature magnetic semiconductors via a metal-semiconductor transition by introducing oxygen into three different ferromagnetic amorphous alloy systems. These magnetic semiconductors show different conduction types determined primarily by the compositions of the selected amorphous ferromagnetic alloy systems. These findings may pave a new way to realize magnetic semiconductor-based spintronic devices that work at room temperature.

Prediction of magnetocaloric properties of Fe-based amorphous alloys based on interpretable machine learning

This study developed a machine learning model to accurately predict the isothermal magnetic entropy change (-SM) in amorphous alloys, a key parameter for evaluating magnetocaloric performance. Four machine learning algorithms were compared, and the (Extremely Randomized Trees) ETR algorithm demonstrated exceptional performance with an (R-squared) R2 value of 0.90 and a (Mean Absolute Percentage Error) MAPE of 13.31 % on the test set. Feature selection techniques, including Pearson correlation coefficient (PCC) and Recursive feature elimination (RFE), identified a subset of 7 important features: (Applied Field) Mf, δr, ΔH, ΔTm, ΔS, Tm‾, and Ec‾. The Shapley Additive Explanations (SHAP) method provided insights into feature importance and critical values. Design strategies for new alloys, using the FeZrB system as an example, were proposed based on the predictive model. The model's generalization ability was validated on other amorphous alloy systems, showcasing its wide applicability. This research contributes to the field of amorphous alloys and suggests future directions for machine learning applications.

(Fe-Ni)-based glassy alloy containing Nb and Cu with excellent soft magnetic properties

Magnetic properties of amorphous Fe38Ni38B12P5Si3Nb3Cu1 alloy ribbons have been investigated in as-spun and annealed states with the aim of developing an ultrasoft magnetic material which is expected to be used in advanced information data devices. A small amount of simultaneous addition of Cu and Nb to a FeNi-metalloid amorphous alloy system caused the change in crystallization process from eutectic type to the primary one. After annealing at the temperature just below the glass transition temperature (Tg), the glassy alloy ribbon exhibit excellent soft magnetic properties, very low coercive force of 1 A/m and extremely high effective permeability of 7.5·104 at 1 kHz which have not been obtained for any kinds of Fe- and Ni-based amorphous alloys, in spite of relatively low saturation magnetic flux density of 0.86 T. The further increase in annealing temperature causes the precipitation of nanoscale fcc particles with a size of about 7 nm including a high density of planar faults and the resulting nanostructure alloy also exhibits good soft magnetic properties with low Hc below 2 A/m. The formation of nanostructure fcc-(Fe,Ni) + glass soft magnetic alloys is also novel. The syntheses of the new Fe-Ni-based glassy and nanocrystalline [fcc(Fe,Ni) + glass] alloy ribbons with ultrasoft magnetic properties are encouraging as a new type of energy saving-type soft magnetic material.

Calculation assisted composition design of Fe-based amorphous alloys

Combining calculation to accelerate the composition design of Fe-based amorphous alloys is of paramount importance for diversifying the alloy systems and applications. In this study, the constituent elements in Fe-based amorphous alloys and the parameters affecting glass-forming ability (GFA) were statistically analyzed. Taking a simple FePC bulk amorphous alloy system as the model material, the ternary phase diagram and the parameters affecting GFA were carefully calculated. Accordingly, optimal FePC alloys with a critical diameter (dc) of 1.5 mm were obtained in the composition range of 78 ≤ Fe ≤ 80 and 11 ≤ P ≤ 13 at.%. This composition design strategy was further evaluated in FeCoNiPC alloy. The optimal Fe72–76Co3–6Ni1–4P13C7 (at.%) alloys exhibit an improved dc of 2 mm. These criteria are quite effective in accelerating the composition design of Fe-based amorphous alloys, and can also be extended to other multi-component alloy systems to discover high GFA amorphous alloys.

Novel Ni-V-Y Electrocatalysts for Hydrogen Evolution Reaction

Generation of renewable energy is improving globally, the ability to store generated energy remains an issue. A new class of water electrolysers that utilize anion exchange membranes (AEMs) are effective at converting water to hydrogen gas which can be used as fuel. Novel electrocatalysts are required for AEMs to be active, stable, and cost effective when used in AEM water electrolysers. Previously, S. Ghobrial investigated the Ni-Nb-Y alloy system as an electrocatalyst for the hydrogen evolution reaction, with Ni and Y components contributed to electrocatalytic activity [1]. Nb phase did not contribute to electrochemical activity and behaved only as a glass former. For the second-generation alloy, V replaced Nb to create a Ni-V-Y alloy. Thermodynamic modelling via FactSage was used to develop the amorphous alloy system. To create the amorphous alloys, a two-step ball milling process was used. Elemental powders were mechanically alloyed and amorphized under cryogenic conditions. The micron sized alloyed powder was size reduced to nanoparticles suitable for use as electrocatalysts via surfactant assisted high energy ball milling (SA-HEBM). Both micron powders and nanoparticles were structurally characterized using X-ray diffraction and SEM. The catalytic activity of the electrocatalysts were electrochemically characterized using steady state polarization to determine Tafel slopes and exchange current densities. A Ni-V-Y alloy was successfully produced via cryomilling and SA-HEBM. The combination of the NiVY amorphous phase + Ni3V + Ni5Y phases in the micron and nanopowders improved activity relative to the intermetallics alone via the spillover effect. The surfactant used in SA-HEBM is not completely removed by the current centrifugation process leading to lower-than-expected activity and marginal spillover enhancement in nanoparticles. With an improved cleaning process, it is predicted the nanoparticles will have higher activities than their micron powder counterparts.[1] - S. Ghobrial, Amorphous Ni-Nb-Y Alloys as Hydrogen Evolution Electrocatalysts, Toronto: University of Toronto, 2019.

Machine learning driven rationally design of amorphous alloy with improved elastic models

Rational design of amorphous alloys from the viewpoint of elasticity can be helpful as it offers close correlations with glass forming ability (GFA), thermal stability, mechanical properties and so on. Here, by separately employing composition and structure descriptors as input, we successfully optimized, generated and interpreted the elastic predictive models via various machine learning (ML) approaches, which exhibit distinct advantages of high accuracy, simple operation, wide applicability and good interpretability relative to that of previously reported elastic models. Meanwhile, the performances of our developed elastic models were well verified via GFA and plasticity prediction in two ternary amorphous alloy systems. Finally, based on the above improved elastic models, we proposed a general framework for rational design of amorphous alloys using four steps strategy. Our results demonstrate the great potential to accelerate the composition screening and property optimization of amorphous alloys.

Correlation of parameters and microstructure of 3D printing bulk medical titanium-based metallic glass

Metallic glass has developed over the past few decades. To fabricate the metallic glass, high cooling rates (105 K/s) is needed to form the disorder atomic structure [1]. Because metallic glass has no grain boundary, its characteristics are superior to traditional crystalline materials, such as good wear resistance, and excellent corrosion resistance [2]. In the past few decades, most amorphous alloy systems can only be manufactured to a millimeter size, causing the application difficulties [3]. Due to development of 3D printing technology nowadays, it’s expected to manufacture metallic glass in a larger size due to the localized melting process with a high cooling rate. Due to the breakthrough in size, it can be applied to medical equipment such as scalpels, dental implants, and various implants in the future. However, the relationship between the materials, 3D printing process parameter, and microstructure evolution is still needed to be explored. Thus, in study, such relationship of Ti-based metallic glass is studied through changing parameters of scan speed and laser power to vary cooling rates and microstructure by Selective Laser Melting (SLM). The samples were examined through the X-ray diffractometer (XRD) and the scanning electron microscope (SEM) with energy disthispersive spectrometry (EDS). The composition variation and microstructure evolution during the 3D printing process was discussed in detail from the point of view of 3D printing parameter, molten pool behavior, and heat of mixing. Furthermore, the mechanical properties of metallic glass were investigated by using micro-indentation, which results showed further that the microstructure indirect effects hardness and young’s modulus of the alloys.

Transition from high-entropy to conventional (TiZrNbCu)1−xCox metallic glasses

In this article, we describe the characterization of a newly fabricated amorphous alloy system (TiZrNbCu)1−xCox covering a broad composition range from high-entropy (HEA) to Co-rich alloys (x ≤ 0.43). We investigated thermal stability, atomic and electronic structure, and magnetic and mechanical properties as a function of chemical composition x. One of the important findings is that all studied properties change their dependence on concentration x within the HEA range. In particular, it has been found that the average atomic volume deviates from Vegard’s law for x > 0.2, the concentration for which the average atomic packing fraction suddenly changes. The valence band structure, studied with ultraviolet photoemission spectroscopy, shows a split-band shape with 3d-states of Co approaching the Fermi level on increasing x. Due to the onset of magnetic correlations, magnetic susceptibility rapidly increases for x > 0.25. Very high microhardness increases rapidly with x. The results are compared with those for similar binary and quinary metallic glasses and with those for Cantor type of crystalline alloys.

Identifying the optimal amorphous precursor alloy system for dual-phase nanostructure formation according to the impurity tolerance and crystallization mechanism

The amorphous precursor alloys for nanostructure with high Bs always exhibit a low impurity tolerance, inhibiting mass production. Here, we comparatively studied the FeBSiCu, FeBPSiCu and FePSiCu alloy systems in Fe83B12-xPxSi4Cu1 (x = 0–12) alloys made with industrial raw materials. Fully amorphous ribbons were readily prepared in the Fe83B12Si4Cu1 and Fe83P12Si4Cu1 alloys. It is difficult to avoid the surface crystallization induced by the impurities in Fe83B12-xPxSi4Cu1 (x = 2–8) amorphous alloys with a relatively high amorphous formability. The Fe83B12Si4Cu1 alloy exhibits a large crystallization temperature interval (ΔT) which can be further widened by P micro-alloying. The macro-substitution of B by P will lead to a significant decrease of ΔT. The ΔT of the novel Fe83P12Si4Cu1 alloy can be effectively widened by increasing the Fe content and microalloying of B, exhibiting a good potential for the combination of superior ΔT, AFA and impurity tolerance. The low impurity tolerance in the Fe83B12-xPxSi4Cu1 alloys is ascribed to the significant difference in the metallurgical properties of the Fe–B and Fe–P alloys, needing new impurity purification processes. These results will bring a new perspective to develop high Bs precursor alloys and experimental references for critical industrialization.

Electrodeposited metallic glasses with superlative wear resistance

The electrodeposition route to obtain amorphous alloys offers a facile, low-cost, and versatile alternative to conventional melt quenching. However, there are significant knowledge gaps in tribological properties and wear mechanisms for electrodeposited metallic glasses (EMGs). Here, the wear behavior and the scratch response of a model binary amorphous alloy system were investigated. Electrodeposited Ni–P metallic glasses were systematically studied as a function of composition, with amorphous alloy formation over the narrow range of 10 at% to 20 at% phosphorus. The electrodeposited metallic glasses showed hardness values in the range of 6.6–7.4 GPa, modulus in the range of 155–163 GPa, and friction coefficient around 0.50. Among the studied alloys, electrodeposited Ni80P20 showed the lowest wear rate, which was two orders of magnitude lower than electrodeposited pure Ni. The wear mechanism was determined to be extensive plastic deformation along with mild ploughing, micro tears, and formation of discontinuous lubricious oxide patches. Scratch tests showed an increase in critical load for damage initiation with the increase in phosphorus content among the amorphous alloys following the trend: Ni80P20 > Ni85P15 > Ni90P10. The overall wear rate for the electrodeposited metallic glasses was found to be lower than most reported bulk metallic glasses (BMGs). This represents a fundamental study on structure-property correlations in electrodeposited metallic glasses and demonstrates the versatility of electrodeposition in tuning the surface properties of amorphous alloys.

Widely tunable optical properties via oxygen manipulation in an amorphous alloy

The ability to widely tune the optical properties of amorphous alloys is highly desirable especially for their potential applications in optoelectronic devices. In this work, we demonstrate that introducing oxygen into an amorphous alloy system of Co-Fe-Ta-B enables the formation of various amorphous derivatives ranging from metals to semiconductors, and eventually to insulators. These oxygen-containing amorphous derivatives gradually become transparent with the opened bandgaps, leading to a continuous increase in their optical transmittance. Furthermore, the reflective metal-type amorphous alloy and transparent insulator-type amorphous oxide of the system can be integrated together to realize the full-color tuning over the entire visible spectral range. This provides a new way to develop large-area color coatings with high design flexibility and full-color tun-ability. We envisage that the design concept proposed in this work is also applicable to many other amorphous alloy systems, from which all types of amorphous materials including alloys, semiconductors and insulators may be developed to show unprecedented optical functionalities.

A general and transferable deep learning framework for predicting phase formation in materials

Machine learning has been widely exploited in developing new materials. However, challenges still exist: small dataset is common for most tasks; new datasets, special descriptors and specific models need to be built from scratch when facing a new task; knowledge cannot be readily transferred between independent models. In this paper we propose a general and transferable deep learning (GTDL) framework for predicting phase formation in materials. The proposed GTDL framework maps raw data to pseudo-images with some special 2-D structure, e.g., periodic table, automatically extracts features and gains knowledge through convolutional neural network, and then transfers knowledge by sharing features extractors between models. Application of the GTDL framework in case studies on glass-forming ability and high-entropy alloys show that the GTDL framework for glass-forming ability outperformed previous models and can correctly predicted the newly reported amorphous alloy systems; for high-entropy alloys the GTDL framework can discriminate five types phases (BCC, FCC, HCP, amorphous, mixture) with accuracy and recall above 94% in fivefold cross-validation. In addition, periodic table knowledge embedded in data representations and knowledge shared between models is beneficial for tasks with small dataset. This method can be easily applied to new materials development with small dataset by reusing well-trained models for related materials.

Experiments and simulations on the magnetization of transparent Co-Fe-Ta-B-O heteroamorphous films

Inducing oxygen into Co-Fe-Ta-B amorphous alloy system makes the transparent amorphous magnetic thin film (Co20Fe47Ta20B13)1-xOx. Oxygen content plays a major role in the magnetization properties of the films. Samples with x=0.41 have a large coercivity ∼1000 Oe, which is 20 times larger than the low oxygen content samples. The forming of a set of single domain magnetic granules rather than continuous magnetic film makes the different magnetization mechanisms. The deviation from Bloch law of saturation magnetization with temperature indicates the Bose-Einstein condensation occurring in magnetic nanostructures. According to the superparamagnetic theory, magnetic phase diagram of the system has been obtained. Monte-Carlo method is used for the simulation of the magnetization of a single domain magnetic granular system at a finite temperature. The simulation results match the experiment to some extent in magnetization-filed curve and field-cooling and zero-field-cooling magnetization curve. This work provides a systematical study of transparent amorphous magnetic thin film system and helps us to know better of this material.

Magnetocaloric effect in Co-based amorphous alloy Co90Nb10Ta3

Abstract We have found that the Curie temperature (Tc) of Co-based amorphous alloy Co90Nb10Ta3 (Tc = 360 K) is much lower than many amorphous alloy systems. Through further research, we have found Co90Nb10Ta3 exists second-order ferromagnetic (FM) to paramagnetic (PM) phase transition near the Tc. Co90Nb10Ta3 amorphous alloy near the Tc has a larger magnetocaloric effect (MCE), under the ΔH = 60 kOe, - Δ S M max =2.43 J kg−1K−1, relative cooling power (RCP) can reach 203.55 J/kg. Compared with Fe-B-Cr, Fe-Cr-Cu-Nb-Si-B, FeCoSiAlGaPCB and FeCrMoCuGaPCB amorphous alloy, the Co-Nb-Ta amorphous alloy has better properties. Co-Nb-Ta amorphous alloy has better mechanical and chemical properties than other amorphous alloys, it is a potential MCE material.

Shifting from Ising model to Heisenberg model critical behavior and the departure from these models in Fe73.5−Cr Cu1Nb3Si13.5B9

Abstract The universality classes of amorphous alloy system Fe73.5−xCrxCu1Nb3Si13.5B9 with x = 0, 2, 4, 6, 8, and 10 are studied by determination of the static critical exponents (β, γ, δ), and critical temperatures from magnetization measurements using two independent methods, namely the Kouvel-Fisher method and the Berger-Campillo et al method. The found values for these critical exponents depend on the content of Cr and interestingly vary from values that correspond to universality classes of standard models (Ising (sample with x = 0), XY (sample with x = 2), and Heisenberg (sample with x = 4)) with short-range interactions to universality class of mean field model (samples with x = 6, 8, and 10) with long-range interactions. The critical temperature decreases quasi linearly with the increase of Cr content. The possible mechanisms leading to such universality classes and shift including the spin-orbit interaction, shape anisotropies, direct exchange and itinerant exchange are analyzed. In addition, X-ray diffraction and Mossbauer spectroscopy studies performed on this alloy system reveal that it has a heterogeneous structure.

Properties of a rare earth free L10-FeNi hard magnet developed through annealing of FeNiPC amorphous ribbons

The rare-earth-free hard magnetic L10-FeNi phase found in cosmic meteorites demonstrates potential as a next-generation permanent magnet. However, it is very difficult to artificially produce the L10-FeNi phase due to the low atomic diffusion coefficients of Fe and Ni near the order-disorder transition temperature (∼320 °C). Therefore, FeNiPC amorphous alloy systems exhibiting crystallization temperature (Tx) near the transition temperature were investigated. The amorphous alloys were annealed at Tx, resulting in high atomic diffusion. The structural and microstructural characterizations of annealed ribbons revealed the formation of L10-FeNi phase through observation of the superlattice peak. The magnetic property, such as coercivity (Hc), also indicated the formation of L10-FeNi phase, because the maximum Hc value is 641 Oe after the annealing process.

Effects of Cu Content on Microstructures and Mechanical Properties of Ti-Ni-Based Amorphous Composites

Abstract Ti-Ni-based amorphous composite samples (Ti0.5Ni0.5)100-xCux with different Cu contents but the same diameter which has been prepared by the copper mold suction casting. The effect of the Cu contents (x=0, 10, 15, 20, 25, 30, 35, 40, at%) on the microstructures and mechanical properties of the amorphous composites was studied. Results show that both fracture strength and plastic strain of the alloy are very high when the copper content is x=20. Meanwhile the alloy exhibits the best comprehensive properties. As the x value increases, the glass forming ability of (Ti0.5Ni0.5)100-xCux alloy shows a waveform change from increasing to decreasing and then to increasing, but following an overall trend towards decreasing. The plasticity of Ti-Ni-based amorphous materials can be improved by adding Cu element in modest quantities (x≈25) to the Ti-Ni-based composites; however, adding more Cu (i.e., x>30) neither can improve the amorphous forming ability nor can enhance its strength. When x=15, the alloy has the highest breaking strength of 2440 MPa while gets the higher yield strength of 1471 MPa causing 17.15% plastic strain. The data are pretty high with respect to other amorphous systems or other alloy systems with memory of their shapes. When x=25, there is a certain increase in the alloy plastic strain with 21.35% plastic deformation.

Microwave absorbing properties of FeCrMoNiPBCSi amorphous powders composite

Abstract The FeCrMoNiPBCSi amorphous alloy system with good soft-magnetic property and high glass forming ability was utilized to prepare amorphous powders which are integrated for electromagnetic wave absorbing composite with silicone-matrix. The absorption parameters were measured by tuning the sample thickness and volume fraction strictly. The results show that FeCrMoNiPBCSi amorphous alloy system is more prone to attain impedance matching and has strong ability on electromagnetic wave attenuation. The value of reflection loss reaches −60.3 dB at 7.08 GHz for the composite (30 vol % powders) and the bandwidth reaches 2.30 GHz for RL

Research progress in U-based amorphous alloys

Uranium-based amorphous alloys are a unique family of amorphous materials, which have so far been less studied due to the high chemical activity and radioactivity of uranium metal. In this paper, we review the compositions, preparations and thermal stability characteristics of U-based amorphous alloys obtained in the early experimental studies, and summarizes our recent results of the preparations and material properties of stable U-based amorphous alloys. The latest progress in our study of U-based amorphous alloys is presented in the three aspects. Firstly, the preparation methods, alloy systems and compositions, formation and crystallization behaviors of the new U-based amorphous alloys, along with the preliminary mechanisms for their formation and structure stabilization are reviewed. A number of new uranium-based amorphous alloy systems have been established based on eutectic law and structural packing model. These alloys show high ability to form glass, and the reduction of glass transition temperatures of some alloys to those of conventional amorphous alloys. The formation rules of binary (U-Fe/U-Co/U-Cr), ternary (U-Co-Al/U-Fe-Sn) and multicomponent alloy system have been investigated. It was found that the ability to form glass is strongly related to some physical parameters such as the local cluster structure, the electron concentration, the enthalpy of mixing, the electronegativity of the alloy component as well as the atomic size. The fragilities of U-based amorphous alloys indicate that they belong to a class of strong glass forming system, which means that the critical dimensions of such amorphous alloys can be further enhanced, and bulk amorphous samples are expected to be prepared. The crystallization activation of this kind of amorphous alloy is higher, and the crystallization process is dominated by nucleation. Then, the microstructures especially the first high-resolution electron microscopic results of the unique amorphous materials are reviewed. Finally, the micro-mechanical and anti-corrosion properties are reported in great detail. It is found that U-based amorphous materials show excellent mechanical properties and corrosion resistance, and the strength and hardness are much higher than those of conventional crystalline uranium alloys, and the corrosion resistance is also superior to the latter, which may be caused by its disorderly amorphous structural characteristics. Amorphous alloys have been the subject of intense fundamental and application research in recent years. Stable U-based amorphous alloys appear to cover all physical phenomena displayed by amorphous alloys. The discovery of outstanding properties in these new alloys therefore would stimulate both the fundamental studies including structure, electronic, glass transition, crystallization, etc., and the application-orientated studies of the thermal stability, mechanical and corrosion properties.