Composition Of Amorphous Alloys Research Articles

Effect of amorphous layer parameters on tensile behavior of amorphous/crystalline CuZr/Cu composites

This study investigates the mechanical behavior and deformation property of CuZr/Cu amorphous/crystalline (AC) composites subjected to uniaxial tensile loading. The results reveal significant insights by varying amorphous shell thickness and amorphous alloy composition. Reducing the amorphous shell thickness from 20Å to 5Å increases the tensile strength of the composite from 2.715GPa to 4.668GPa due to the enhanced AC interface effect. The insertion of crystalline phases in the amorphous matrix induces nucleation zones for the shear bands and dislocations, affecting the plastic flow distribution. The shear strain and residual stress predominantly manifest in the amorphous shell. A thinner amorphous shell induces substantial shear strain in crystalline phases, promoting homogeneous deformation. The dislocations prompt plastic deformation in crystalline phases, altering atomic configurations. The AC interfaces initiate deformation nucleation, generating partial dislocations, stacking faults, and twinning in the tension. Besides, the total dislocation length rises with strain increase and thinner amorphous shell. Moreover, the increase of Cu content in the amorphous CuZr shell leads to increased tensile strength and elastic modulus. The higher Cu content increases the concentration of shear strain regions in the composites. The deformation mechanism is also switched from the dominant shear band to the homogenous deformation with increasing Cu content in the amorphous shell. Finally, the phase change shows that the FCC phase decreases and the amorphous phase gain is less as the percentage of Cu in the amorphous increases.

One-step synthesis of self-supporting porous Cu81(Ni,Co)19 intermetallic catalysts for hydrogen evolution reaction

The development of hydrogen evolution reaction (HER) catalysts with excellent performance is the key to the wide-scale application of hydrogen energy. Herein, this work facilely synthesizes the self-supporting porous Cu81(Ni,Co)19 electrocatalysts by dealloying ZrNiCoCuAl amorphous alloy in HF solution. By regulating the composition of ZrNiCoCuAl amorphous alloy dealloying precursor, the porous Cu81(Ni,Co)19 composite synthesized by dealloying Zr60Ni8Co8Cu16Al8 amorphous alloy demonstrates the great HER performance with an overpotential of 35 mV at 10 mA cm−2 and a Tafel slope of 73.3 mV dec−1. The outstanding catalytic performance of porous Cu81(Ni,Co)19 is attributed to the hierarchical porous structure, low charge transfer resistance as well as the synergistic interactions among the Cu, Ni and Co elements. Moreover, the theoretical calculations indicate that the constituent Cu, Co and Ni elements in the Cu81(Ni,Co)19 intermetallic alloy can act synergistically to optimize the free energy of hydrogen adsorption, therefore improve HER activity.

The Influence of the Composition of Amorphous Alloys on Their Corrosion Resistance in Aggressive Environments of Different Nature

The Influence of the Composition of Amorphous Alloys on Their Corrosion Resistance in Aggressive Environments of Different Nature

Application of CALPHAD Method for Predicting of Concentration Range of Amorphization of Transition Metals Melts

Early, the efficiency of the CALPHAD (Calculation of Phase Diagrams) method to a targeted search for compositions of amorphous alloys has been shown. The method for predicting the ranges of amorphization is based on the calculation of diagrams of metastable phase transformations between supercooled melts and boundary solid solutions on the base of pure elements. In this work, the model parameters for thermodynamic properties of liquid alloys and boundary solid solutions were summarized in a self-consistent database for the multicomponent Cu–Fe–Ni–Ti–Zr–Hf system. Such database for the multicomponent system is based on a common set of model parameters for boundary binary and ternary systems. This database was used to predict the concentration ranges of amorphization for the quinary Cu–Fe–Ni–Ti–Zr, Cu–Fe–Ni–Ti–Hf and boundary ternary and quaternary systems. The results of calculations are presented along sections in quaternary and quinary systems. The ternary and quaternary equiatomic alloys along with high entropy CuFeNiTiZr and CuFeNiTiHf alloys are trapped into prognosed composition ranges of amorphization. Predicted composition space of amorphization for melts of the Fe–Ni–Ti–Zr system is shown on the concentration tetrahedron. Based on the obtained results, a new criterion for predicting the concentration regions of amorphization of multicomponent melts is proposed, according to which the presence of a sufficient content of metals that are electron acceptors and donors is a chemical factor that affects the thermodynamic stability of melts and determines their glass-forming ability. For multicomponent melts of the Cu–Fe–Ni–Ti–Zr–Hf system the concentration ranges of amorphization correspond to the simultaneous fulfillment of the conditions xFe + xNi + xCu > 0.25 and xTi + xZr + xHf > 0.15, where Fe, Ni, and Cu are electron acceptors and Ti, Zr, and Hf are electron donors.

Design of Amorphous Alloy Composition and Optimization of Vacuum Die Casting Process Parameters Based on Co-evolutionary Algorithm

Design of Amorphous Alloy Composition and Optimization of Vacuum Die Casting Process Parameters Based on Co-evolutionary Algorithm

Mechanical, wetting and corrosion properties of a Zr-based amorphous alloy composite consolidated by spark plasma sintering

The bulk Zr48Cu47.5Al4Co0.5 amorphous alloy composites were successfully consolidated by spark plasma sintering under different sintering temperatures. Their mechanical, wetting and corrosion properties were investigated. The results show that the density and hardness increase firstly with increase in the sintering temperature, and then decrease when the sintering temperature exceeds 713K. The Cu10Zr7 and CuZr2 phases continuously grow up with increasing sintering temperature. The growth rate of the volume fraction is ∼3.5 times larger for the Cu10Zr7 than for the CuZr2 under present sintering conditions. The water contact angle decreases with increasing sintering temperature. In addition, the corrosion potential of the 713K-sintered sample is the highest. The corrosion current density of the 673K-sintered sample is 2∼3 times larger than that of the other samples under higher sintering temperatures. The growth mechanism for Cu10Zr7 and CuZr2 phases and the corrosion mechanism are also discussed.

High-Throughput Synthesis and Characterization Screening of Mg-Cu-Y Metallic Glass

Bulk metallic glasses can exhibit novel material properties for engineering scale components, but the experimental discovery of new alloy compositions is time intensive and thwarts the rate of discovery. This study presents an experimental, high-throughput methodology to increase the speed of discovery for potential bulk metallic glass alloys. A well-documented system, Mg-Cu-Y, was used as a model system. A laser additive manufacturing technique, directed energy deposition, was used for the in situ alloying of elemental powders to synthesize discrete compositions in the ternary system. The laser processing technique can supply the necessary cooling rates of 103–104 Ks−1 for bulk metallic glass formation. The in situ alloying enables the rapid synthesis of compositional libraries with larger sample sizes and discrete compositions than are provided by combinatorial thin films. Approximately 1000 discrete compositions can be synthesized in a day. Surface smoothness, as discerned by optical reflectivity, can suggest glass-forming alloys. X-ray diffraction coupled with energy dispersive X-ray spectroscopy can further refine amorphous alloy signatures and compositions. Transmission electron microscopy confirms amorphous samples. The tiered rate of amorphous alloy synthesis and characterization can survey a large compositional space and permits a glass-forming range to be identified within one week, making the process at least three orders of magnitude faster than other discrete composition techniques such as arc-melting or melt-spinning.

Rationality of two-phase coexistence with no element segregation in a CuZr-based amorphous alloy composite

Here, the structure features of Cu62Zr34.4Al3Nb0.6 amorphous alloy composites (AACs) are studied by combining experimental characterization with first-principles calculation. Element segregation, which is common in conventional alloy materials, does not occur in two phases (crystalline and amorphous phase) of the AACs due to complex solid solution. The lattice parameters, electron distribution, charge transfer and electrical potential, which are directly related to atomic bonding and lattice parameters of different structures, are obtained by calculating the various types of structural models, including interstitial solid solution, substitutional solid solution, B2 and amorphous phase. Finally, the formation and stability of solid solution in crystalline phase and amorphous phase are elucidated by first-principles calculation. The work has important guiding significance for understanding the two-phase structure and solidification mechanism in AACs materials.

Heterogeneity of microstructures in a Cu–Zr based amorphous alloy composite reinforced by crystalline phases

Amorphous alloy composites (AACs) comprising reinforcing crystalline phases exhibit far better mechanical properties than their base amorphous alloy counterparts, and Cu–Zr based alloys consisting of B2 phase particles embedded in an amorphous matrix are well-researched AACs in this respect. Traditionally, the B2 particles in Cu–Zr based AACs may appear to be homogeneously crystalline (without any amorphous phase inside), the glassy matrix homogeneously amorphous, and their interfaces atomically sharp. Yet, such a picture would pose difficulties in understanding how crystallization can happen in the glassy matrix, since the crystallized product is denser than but iso-stoichiometric with the matrix. The present work provides insights into this puzzle, by using electron microscopy, nanoindentation and molecular dynamics (MD) simulations to investigate the structures and mechanical properties of the crystalline and amorphous phases, and their interfaces in a Cu62Zr34.5Al3Nb0.5 AAC. Surprisingly, in this AAC, the superficially crystalline particles with tens to hundreds of microns large are found to be heterogeneous at the sub-micron scale, comprising nano-crystallites embedded in a glassy matrix, and the amorphous phase outside also exhibits a gradient in free volume content towards the interface. Smaller particles containing only B2 nano-crystallites are found to be softer than the amorphous matrix, while larger particles are harder than the amorphous phase due to martensitic transformation into the B19’ phase. MD simulations indicate that the B2 phase is marginally more stable than the glassy state, and on crystallization the densification leads to free-volume generation in the surrounding glassy matrix as observed experimentally. Mechanics analysis indicates that the strain energy in the glassy matrix associated with free-volume generation scales with the volume of the crystallization, as would be the crystallization energy itself. Hence, crystallization in the AAC leading to a two-phase structure is a spontaneous but kinetically limiting process arising from the net energy difference between the crystallization energy and free-volume energy produced in the glassy matrix. This work provides a detailed understanding of the heterogeneity in the microstructures in Cu–Zr based AACs, to shed light on the crystallization of the iso-stoichiometric B2 phase from the amorphous phase.

A new approach to predicting compositional regions of facilitated glass formation in the Gd-Ni-Al system

Efficient search for new compositions of amorphous alloys and significant savings in labor and material costs for the ones production require the development of reliable theoretical methods for predicting the glass-forming ability of multicomponent metal alloys. We introduce a new model for predicting the compositions of bulk amorphous metallic glasses (BMGs) and ribbons with its test application to the Gd-Ni-Al system. The proposed model parameters Θx−y(x),Θx−y(y) make it possible to forecast the location of glass-forming compositions by finding the minimum result of multiplying the PHSS parameter by the geometric coefficient Γ1,2,3(x), Γ1,2,3(y). The compositions of Gd-Ni-Al system with the best glass-forming ability (GFA), namely Gd49Ni29Al22 (BMG) and Gd40Ni51Al9 (ribbon), have been successfully determined using these parameters. The correlation between the geometric factors Γ1,2,3(x), Γ1,2,3(y) and effective packing density is shown. Amorphous alloys can be formed only at certain content of the Gd-Ni-Al system components, under which the geometric factors Γ1,2,3(x), Γ1,2,3(y) are close to the radius ratios central atom 1/central atom 2 and central atom 2/central atom 1, respectively. The results of this work open up prospects for developing reliable theoretical methods of new metal glasses prediction.

Synthesis and characterization of amorphous alloy Co69Nb25b6

. In this paper, amorphous alloy composition Co69Nb25B6 was prepared by high-energy ball milling which allows the formation of phases through solid state reaction. In addition, the effects of a 21:1 powder to ball mass ratio were used and the milling time during high energy milling was crucial for the formation of the amorphous and ferromagnetic phases. The characterization of the Co69Nb25B6 alloy was investigated by X-ray diffraction, scanning electron microscopy and hysteresis loops of alloy were measured with a VSM, and exhibited the typical soft magnetic character.

Microstructure and Corrosion Resistance of a Novel AlNiLa Lightweight Medium Entropy Amorphous Alloy Composites

Microstructure and Corrosion Resistance of a Novel AlNiLa Lightweight Medium Entropy Amorphous Alloy Composites

Microstructure and Corrosion Behavior of Laser Cladding FeCoNiCrBSi Based High-Entropy Alloy Coatings

High-entropy amorphous alloys designed based on the concept of multi-principal components have the comprehensive advantages of high passivation element content and amorphous structure, and are considered as one of the promising alternative protective materials in extreme marine environments. However, based on the composition of traditional amorphous alloys, the multi-principal design significantly reduces its glass forming ability. In order to improve the glass formation ability of high-entropy amorphous alloys, this study attempts to design Fe19.6Co19.6Ni19.6Cr19.6(B13.72Si5.88)19.6Y2 alloy by microalloying on the basis of traditional FeCoNiCrBSi high-entropy amorphous alloy. The traditional Fe43.6Co6Ni17.4Cr9B17.5Si1.5Nb5 iron-based amorphous alloy was selected as the comparison material. Then, spherical alloy powders were prepared by gas atomization. The amorphous nanocrystalline composite coatings were deposited on the 304 stainless steel by laser cladding technology. The microstructure of the coatings was characterized by scanning electron microscopy and X-ray diffractometer. The corrosion behavior of laser cladding coatings in 3.5 wt.% NaCl solution were investigated in detail. The results show that the Fe43.6Co6Ni17.4Cr9B17.5Si1.5Nb5 powder is composed of FCC, Laves and boride phases. Whereas the Fe19.6Co19.6Ni19.6Cr19.6(B13.72Si5.88)19.6Y2 high-entropy amorphous alloy powder is composed of FCC and boride phases. Due to the remelting and multiple heat treatments during the preparation of the laser cladding coatings, borides were precipitated in both coatings. The microstructure of the two coatings from the bonding area with the substrate to the top layer are plane grains, dendrite, equiaxed grains and amorphous phase, respectively. Fe19.6Co19.6Ni19.6Cr19.6(B13.72Si5.88)19.6Y2 high-entropy amorphous alloy coating exhibits high corrosion potential, passivation film resistance and low corrosion current density in 3.5 wt.% NaCl solution. In addition, the passivation film formed on the coating has higher Cr content and lower defect concentration, showing more excellent corrosion resistance.

Wetting behavior and interfacial characteristics of Ti33Zr17Cu50 amorphous alloy on AlN

Our study investigated the wetting of AlN ceramic by molten Ti33Zr17Cu50 amorphous alloy at 1123–1223 K using a modified sessile drop method. Ti33Zr17Cu50 amorphous alloy presents an outstanding wettability and moderate reactivity. The spreading of the melts on AlN is controlled by the adsorption of Ti mainly and then forming TiN. The emergency of precursor film can be attributed to the high adhesive energy between Zr and TiN layer. Spreading dynamics put up two stages, the first stage is relative to the adsorption of Ti at the interface and further CuTi3 IMCs, and the second stage may correspond to the formation of a thin TiN layer. From the reasonable wettability point of view, it is difficult to fabricate excellent Ti-based amorphous alloy composites using AlN as a reaction agent to form TiN reinforcement in situ. Similarly, a favorable ceramic-ceramic or metal-ceramic joint can be obtained using Ti33Zr17Cu50 amorphous alloy as filler.

Combined data-driven model for the prediction of thermal properties of Ni-based amorphous alloys

Ni-based amorphous alloys are a unique class of materials that are attracting attention in biomass plants because of their outstanding physical properties at high temperatures. Several studies have investigated and designed the relationships between the input and target properties of alloys using machine learning algorithms. The extensive use of these models has a limitation in that the required composition is yet to be determined. To address this issue, we trained four machine learning algorithms to design Ni-based amorphous alloys and predict their thermal properties. The machine learning algorithms were trained using only the compositions of Ni-based amorphous alloys obtained from the relevant literature as the input feature data. Random forest regression was selected to predict and design the Ni-based amorphous alloys. We applied this algorithm to design amorphous alloys with the desired thermal properties and an optimal composition determined via particle swarm optimization. A melt spinner was used to fabricate the alloy. X-ray diffraction and differential thermal analyses were used to evaluate the specimens. Empirical equations were proposed for use in industrial fields.

Structural stability of mechanically alloyed amorphous (FeCoNi)70Ti10B20 under high-temperature and high-pressure

Nanostructured (FeCoNi)70Ti10B20 (at%) alloy was synthesized by mechanical alloying from elemental powder mixture of Fe, Co, Ni, Ti and B using ball milling. The effect of ball milling time on the evolution of structure and morphology was investigated by X-ray diffraction, scanning and transmission electron microscopy and differential thermal analysis. It was observed that the formation of solid solution of (FeCoNi)70Ti10B20 started from the very onset of the milling process. Crystallite size and lattice strains seemed to be leveled off after 20 h of milling with no further major changes. The milling process for longer periods introduced severe plastic deformations causing formation of amorphous phase of (FeCoNi)70Ti10B20. The amorphous alloy composition was confirmed by energy dispersive X-ray spectroscopy analysis that showed an excellent homogeneity of the alloying elements. The phase stability of the mechanically alloyed amorphous sample was further verified by employing high-temperature and high-pressure studies. The alloy samples heat-treated at 700 °C revealed crystallization of the amorphous phase. However, synchrotron-based high-pressure ambient temperature X-ray diffraction studies confirmed that the amorphous phase of the alloy remained stable up to the pressure of 30 GPa. The 50 h milled sample after being annealed at 350 °C showed improvement in the soft magnetic properties of the alloy, which was due to the probable elimination of the residual stress in the amorphous phase of the alloy powders.

Oxygen addition for improving the strength and plasticity of TiZr-based amorphous alloy composites

The addition of a small amount of oxygen improves the mechanical properties, especially plasticity, of Ti45.7Zr33Ni3Cu5.8Be12.5 amorphous alloy composites (AACs) at room temperature (298 K). Compared to the plasticity of AACs without added O (5%), the plasticity of the composites with 0.73 at.% O (nominal composition) was much higher (11 %). Even at O content higher than 0.73 at.%, the AACs exhibited good plasticity. The highest plasticity of ∼12.3 % was observed with 2.87 at.% O. Two distinct mechanisms are proposed to explain the enhanced plasticity of the AACs. At low O content, although deformation-induced phase transformation was suppressed, a substantial amount of α’’ martensite was formed. The microstructural features of α’’ martensite, such as thinner laths and homogeneous distribution, induced the formation of multiple shear bands in the amorphous matrix. At high O content, deformation-induced phase transformation was seriously suppressed. A dispersed nano ω phase was formed during rapid solidification in AACs with O content higher than 1.45 at.%. This resulted in a weakening in the anisotropy of β dendrites and led to their homogenous deformation. Furthermore, multiple shear bands were formed in the amorphous matrix. Apart from plasticity, the strength of the AACs also increased with an increase in the O content. This phenomenon was explained in terms of three mechanisms, viz. the solid-solution-strengthening effect of O, fine-grain strengthening of β dendrites, and secondary phase strengthening by the nano ω phase.

Micro-Compression Characterization of Electrodeposited Nickel Phosphorus Amorphous Alloys for MEMS Application

This study reports mechanical property evaluation of electrodeposited nickel phosphorus amorphous alloys. Electrodeposited nickel materials have excellent properties such as high elastic modulus, high strength, low internal stress, and excellent conductivity, and are expected to be applied to micro-sized machines and micro electro mechanical systems [1]. An example is nickel phosphorous amorphous alloys, which are commonly used as structure materials in microelectromechanical system devices [2].Electrodeposition is a powerful technique to manipulate properties of metallic materials used in electronic devices. For example, nickel-phosphorus alloys can be prepared by electrodeposition with an electrolyte containing nickel chloride and nickel sulfate as source of the nickel, and sodium hypophosphite as source of the phosphorus [3, 4]. Properties of the electrodeposited nickel phosphorous alloy can be controlled by the bath temperature, current density, pH, sodium hypophosphite concentration, etc.In order to use the nickel phosphorus amorphous alloy as structure components in a MEMS device, it is necessary to investigate the mechanical properties using specimens having similar size as those used in a MEMS device. Hence, mechanical property characterization of electrodeposited nickel phosphorus amorphous alloys has to be conducted using specimens having dimensions in micrometer scale.Nickel phosphorus amorphous alloys were electrodeposited on pure copper plates using a commercially available electrolyte provided by MATEX Co. Japan. Thickness of the nickel phosphorous alloy was controlled to be at around 50 μm. Composition of the nickel phosphorus amorphous alloy was determined by energy dispersive X-ray spectroscopy (EDS). Specimens used in the micro-mechanical testing were micro-pillars having a square cross-section. The micro-pillars were fabricated by focus ion beam (FIB) system. Before the FIB process, the nickel phosphorus electrodeposited copper plate was thinned down to roughly 100 μm. Dimensions of the micro-pillar were 5 × 5 × 10 μm3, 8 × 8 × 16 μm3, 15 × 15 × 30 μm3, and 20 × 20 × 40 μm3. Shape of the micro-pillar was observed in a scanning electron microscope (SEM) before and after the micro-compression test to confirm the exact dimension and deformation behavior. Then micro-compression test was conducted using a micro-mechanical testing system developed in our group [1]. The yield strength was determined from the engineering stress-strain curve generated from the micro-compression test. Vickers hardness of the nickel-phosphorus amorphous alloys was also measured to compare with the yield strength obtained from the micro-compression test.Fig. 1 and 2 show SEM images of the 20 × 20 × 40 μm3 micro-pillar before and after the micro-compression test, respectively. After the compressive deformation, slip deformation, which is often seen in amorphous metals, was observed. Evolution of this slip deformation could be identified from the stress oscillation observed in the stress-strain curve shown in Fig. 3. Similar slip deformation and stress oscillation were also observed in nickel phosphorous amorphous alloy micro-pillars with other sizes. Table 1 shows the 0.2% yield strength and 1% flow strength determined from the stress-strain curves. The 0.2% yield strength fluctuated between 2.01 - 2.08 GPa and the 1% flow strength changed between 2.37 - 2.47 while the one side of the micropillar varied between 10 - 40 μm. Micro-compression test of the nickel phosphorous amorphous alloys revealed that there was no obvious relationship between size of the micro-pillar and the yield strength in the range evaluated in this study. This result was different from the sample size effect commonly observed in metallic materials with high crystallinity [5]. [1] K. Takashima, Y. Higo, S. Sugiura, M Shimojo, Mater. Trans. 42 (2001) 68-73. [2] X Li, B Bhushan, K Takashima, C Bank, Y Kim. Ultramicroscopy 97 (2003) 481-494. [3] C.C. Hu, A. Bai, Surf. Coat. Techno. 137 (2001) 181-187. [4] C.C. Hu, A. Bai, Mater. Chem. Phys. 77 (2003) 215-225. [5] J.R. Greer, J.Th.M. De Hosson, Prog. Mater. Sci. 56 (2011) 654-724. Figure 1

High-entropy alloy and amorphous alloy composites fabricated by ultrasonic vibrations

We successfully fabricate high-entropy alloys and amorphous alloy composites by adopting the proposed ultrasonic vibration method. The low-stress, low-temperature method enables us to create composites that combine both amorphous and crystalline properties. Microscopic observations and computed tomography measurements indicate good bonding quality without pores or cracks in the composites. Due to the unique structure which mixes soft and rigid phases, the composite exhibits improved mechanical performance compared to that obtained from a pure single phase. Our results are promising for the manual design and fabrication of smart materials containing multiple phases and compositions.

Study of the composition of innovative materials for the restoration and strengthening of machine parts

The article describes promising, innovative materials for the restoration of machine parts. The elemental composition was studied by atomic emission spectrometry with inductively coupled plasma. The elemental composition of amorphous alloys of grades 84KHSR, 2HSR, 82H7HSR and nanocrystalline alloy of grade 5BDSR was studied. Based on the results of elemental analysis, it can be argued that the chemical composition of the materials studied by us will help to increase the productivity of technological processes of recovery and the formation of amorphous or nanocrystalline structures of high microhardness in the reducing coatings