Bulk Glassy Research Articles

Sol-gel Chemistry Approaches for the Manufacturing of Innovative Functional Composites for the Aerospace Sector

Sol-Gel is a “bottom-up” synthesis method that enables the production of films, nano/microparticles, fibers, gels, and bulk materials, both glassy and crystalline. Sol-Gel chemistry can be a vital tool for solving problems in several industrial applications where nanotechnology is necessary to overcome constraints. Here, various examples involving silicate-based materials are discussed. Silicatic materials with a variety of morphologies and applications, e.g., monodisperse SiO2 particles ranging in size from a few nanometers to a micron, can be synthesized through hydrolysis and polycondensation reactions of silicon alkoxide precursors. Using an environmentally friendly electrospinning process, silica nanoparticles can be incorporated into polyvinylpyrrolidone (PVP) fibers to create novel, fire-resistant sound absorbers. Additionally, by employing hybrid techniques based on Sol-Gel, the flame retardance of nanocomposites made of silica and epoxy resin as well as epoxy-based composites including hemp, even cured with cycloaliphatic hardeners, can be enhanced. The development of novel materials beneficial for aviation applications, such as hydrophobic (potentially self-anti-icing) coatings, is a further proof of the effectiveness of Sol-Gel chemistry.

Low-temperature relaxation behavior of a bulk metallic glass leading to improvement of both strength and plasticity

Low temperature relaxation and structural changes in a Cu36Zr48Al8Ag8 bulk glassy alloy well below the glass-transition temperature are examined by using differential scanning calorimetry, X-ray diffractometry, scanning and transmission electron microscopy. Although densification of the sample takes place owing to beginning of structural relaxation both room-temperature mechanical strength and plasticity values are increased. The studied samples exhibited an inverse relationship between compressive strength and hardness. However, no clear structural changes in terms of crystallization or phase separation are observed. The results are interpreted in terms of both structural relaxation and release of internal stresses.

Improvement of intrinsic plasticity and strength of Zr55Cu30Ni5Al10 metallic glass by tuning the glass transition temperature

We report the tuning of the glass transition temperature (Tg) in Zr55Cu30Ni5Al10 metallic glass by rolling at room temperature. The precise thermo-analytical measurements using step-scan modulated temperature differential scanning calorimeter (MTDSC) revealed a decrease of Tg by 16.9 K in ribbons and 7.1 K in bulk glassy plates upon 40% and 70% thickness reduction, respectively. The cold rolled plates exhibit higher yield strength up to σy = 1.66 GPa and larger plastic strain (εp = 8.0%) before failure than that of as-cast plates (σy = 1.45 GPa). Transmission electron microscopy and DSC studies suggest that a relaxed structure has evolved due to the deformation induced structural change upon rolling, which reduces the activation energy of the shear transformation zone and improves the inherent plasticity of the glassy phase.

Effect of strain rate and crystalline inclusions on mechanical properties of bulk glassy and partially crystallized Zr52.5Cu17.9Ni14.6Al10Ti5 alloy

The mechanical properties of the Zr52.5Cu17.9Ni14.6Al10Ti5 alloy were presented, with an emphasis on the strain rate effect and presence of crystalline inclusions on the deformation and fracture mechanisms. X-ray diffraction studies indicated fully amorphous alloy structures with lower oxygen contents and partial crystalline structures at higher oxygen levels; however, completely different compressive deformation behaviour was observed. Uniaxial compression tests of the fully amorphous alloy showed elastic deformation, followed by yielding, distinct plastic deformation and serration flow behaviour. An increase in strain rate from 1×10–4 to 1×10–2 s–1 did not affect the yield strength; however, it decreased the compressive fracture strength and reduced the plastic strain. Scanning electron microscopy (SEM) observations with energy dispersive spectroscopy (EDS) analysis showed that the intermetallic CuZr2 phase was present even in the low oxygen content alloy, leading to lower fracture strength and ductility loss. For the high oxygen level samples, the presence of the dendritic Zr51Cu28Al21 phase was confirmed, leading to fracture strength impairment. The difference between ductile and brittle samples has been reflected on the fracture surfaces. The higher the plastic strain was, the higher the density of shear bands forming during deformation manifested by a serration flow behaviour on stress–strain curves.

Effect of Cr Addition on Glass-Forming Ability and Corrosion Properties of FeCoSiBPC Bulk Glassy Alloys

Effect of Cr Addition on Glass-Forming Ability and Corrosion Properties of FeCoSiBPC Bulk Glassy Alloys

Mechanical and Magnetic Properties of New (Fe,Co,Ni)–B–Si–Ta Bulk Glassy Alloys

The alloying effects of the like-atom substitution of Ni and Co for Fe on the various properties of Fe70B16.7Si8.3Ta5 metallic glass are investigated in this present work. New Fe-based bulk glassy alloys, namely Fe60–x Co x Ni10B16.7Si8.3Ta5 (at.%; x = 10, 20 and 30) with critical diameters up to 1.5 mm, were made by means of copper mold casting. A new glass-forming ability indicator, viz., the enthalpy of supercooled liquid, has been introduced for assessment of the glass-forming abilities (GFAs) of these Fe-based multi-component alloys. Nano-indentation results indicate that the calculated elastic modulus and hardness of the bulk glassy alloys are lower than those of the Fe70B16.7Si8.3Ta5 alloy. Among these bulk glassy alloys, Fe70B16.7Si8.3Ta5 exhibits the large elastic modulus and hardness with values of 178 ± 1 GPa and 12.9 ± 0.1 GPa, respectively. All the bulk glassy alloys exhibit good soft magnetic properties with high saturation magnetization B s ~ 0.75–1.04 T but low coercive force H c ~ 0.2–5.2 A/m.

Corrosion Fatigue Studies on a Bulk Glassy Zr-Based Alloy under Three-Point Bending

Corrosion fatigue (CF) tests were carried out on bulk glassy Zr52.5Cu17.9Al10Ni14.6Ti5 (Vitreloy 105) samples under load-controlled three-point bending conditions with a load ratio of R = 0.1 in 0.01 M Na2SO4 + 0.01 M NaCl electrolyte. During cyclic testing, the bar-shaped specimens were polarized in situ at constant potentials and the current was monitored. Three different anodic potentials within the interval between the pitting potential EP and the repassivation potential ER, and three different load amplitudes were applied. In some cases, in situ microscopic observations revealed the formation of black corrosion products in the vicinity of the crack tip during anodic polarization. Fractographic analysis revealed a clear distinction between two modes of crack growth characterized by smooth dissolution induced regions on the one hand and slim fast fracture areas on the other hand. Both alternating features contributed to a broad striated corrosion fatigue fracture surface. Moreover, further fatigue tests were carried out under free corrosion conditions yielding additional information on crack initiation and crack propagation period by means of the open circuit potential (OCP) changes. Thereby, a slight increase in OCP was detected after rupture of the passive layer due to bare metal exposed to the electrolyte. The electrochemical response increased continuously according to stable crack propagation until fracture occurred. Finally, the fracture surfaces of the corrosion fatigue samples were investigated by energy dispersive X-ray with the objective of analyzing the elemental distribution after anodic dissolution. Interestingly, anodic polarization at a near repassivation potential of -50 mV vs. SCE (Saturated Calomel Electrode, E = 0.241 V vs. SHE, Standard Hydrogen Electrode) led to favorable effects on the fatigue lifetime. In conclusion, all results are conflated to a corrosion fatigue model for bulk glassy Vitreloy 105 under anodic polarization in chloride-containing electrolyte and compared to the previously proposed stress corrosion mechanisms under similar conditions.

Nanocrystallization of Cu-Based Bulk Glassy Alloys upon Annealing

Cu-based bulk glassy alloy is a new amorphous system developed recently, which has large glass forming ability and relatively low cost (Dai et al., 2006; Fu et al., 2008; Kim et al., 2006; Malekana et al., 2010; Zhang & Zhang, 2008). The tensile fracture strength is much higher than crystals, reaching up to 2,000 to 2,400 MPa, with certain ductility. And compared to Zr-based and Pd-based bulk glassy alloys, the strength of Cu-based bulk glassy alloy is also on the top, which can be used as ultra-high strength structural materials in the future. Until now, many researchers in the world have done a lot of deep studies on Cu-based bulk glassy alloy. But as structural materials, the plastic property of prepared Cubased bulk glassy alloy which has lowers plastic property than steel materials also need to be improved. Therefore, it’s an urgent problem to improve the plasticity and toughness of amorphous alloys. Based on the research of bulk glassy alloy, in recent years, the research on the composite material of bulk glassy and nanocrystalline alloy has been carried out (Barekara et al., 2010; Liu et al., 2009; Xie et al., 2008; Yang et al., 2009; Zhang et al., 2013). Because when the nanocrystalline evenly distributed in the bulk glassy alloy matrix, the properties of bulk glassy alloy can be further optimized, while maintaining high strength and improving the lower plastic. So the application field of high strength structural material can be expanded. In this paper, Cu-based bulk glassy alloy was prepared through copper mold casting method. The nanocrystallization of bulk glassy alloy was obtained by annealing. The annealing process, microstructure and properties of the nanocrystallization were investigated. The preparation of Cu-based bulk glassy-nanocrystalline alloy composite materials on the basis of the theory and technology pISSN 2287-5123·eISSN 2287-4445 http://dx.doi.org/10.9729/AM.2016.46.1.32

Formation and mechanical properties of Zr-Nb-Cu-Ni-Al-Lu bulk glassy alloys with superior glass-forming ability

Glass-forming ability (GFA) and mechanical properties of (Zr0.58Nb0.03Cu0.16Ni0.13Al0.10)100-x Lu x (x = 0-3 at%) alloys have been investigated. The GFA of Zr58Nb3Cu16Ni13Al10 alloy is dramatically enhanced by adding Lu. The (Zr0.58Nb0.03Cu0.16Ni0.13Al0.10)98Lu2 alloy possesses the highest GFA in the studied Zr-Nb-Cu-Ni-Al-Lu alloys, with its critical diameter for glass formation reaching 20 mm by copper-mould casting method, while that of the Lu-free Zr58Nb3Cu16Ni13Al10 alloy is 7 mm. The critical diameters of (Zr0.58Nb0.03Cu0.16Ni0.13Al0.10)100-xLux (x = 1 at% and 3 at%) alloys are 15 mm and 12 mm, respectively. The Lu addition to Zr58Nb3Cu16Ni13Al10 alloy induces the change of initial crystallization phases from face-centred-cubic Zr2Ni and tetragonal Zr2Ni phases for the Lu-free Zr58Nb3Cu16Ni13Al10 alloy to an icosahedral quasi-crystalline phase for the Lu-doped alloys, which may be the origin for the enhanced GFA of the Lu-doped alloys. The compressive fracture strength and plastic strain of the bulk glassy (Zr0.58Nb0.03Cu0.16Ni0.13Al0.10)98Lu2 alloy are 1 610 MPa and 1.5%, respectively.

Study of local structure in hyper-eutectic Zr-Cu-Al bulk glassy alloys by positron annihilation techniques

The Zr-Cu-Al bulk glassy (BG) alloy, which has amorphous structure, possesses various properties such as high strength and toughness with compositional dependence. In the present study, density, positron annihilation lifetime and coincidence Doppler Broadening measurement have been performed for various compositional hyper-eutectic Zr-Cu-Al BG alloys. The density of hyper-eutectic Zr-Cu-Al BG alloys increases with decreasing of Zr fraction. In contrast, positron lifetime for all compositional alloys is almost constant about 165 psec. In addition, the CDB ratio profile is almost the same for hyper-eutectic alloys. This unchanging trend of CDB ratio profile is quite different from that of hypo-eutectic BG alloys. These results reveal that different internal structure exists in hyper and hypo-eutectic BG alloys.

Effects of Minor Additions on Ni- and Be-Free Ti-Based Bulk Glassy Alloys

We investigated the effects of addition elements (Sn, Al, Si, Ag, Fe, Cr) with a small amount on the glass-forming ability, thermal stability and mechanical properties of the Ti-Zr-Cu-Pd glassy alloy system. The results revealed that minor Sn addition improved the glass-forming ability, thermal stability and plasticity, Si addition enlarged the supercooled liquid region, and Fe addition improved the plasticity, while minor additions of Si, Ag, Fe, and Cr lowered the glass-forming ability, and Al and Cr additions were harmful to the plasticity of the Ti-Zr-Cu-Pd glassy alloy system.

Solidification Atmosphere and Glass-Forming Ability of Engineering Important Fe- and Zr-Based Bulk Glassy Alloys

It is important to clarify the best solidification condition for the formation of bulk glassy alloys in Fe- and Zr-based alloy systems with engineering values. The effectiveness of atmosphere during injection casting changes in the order of O2 > Air > N2 > Ar > He for Fe76Si9B10P5 bulk glassy alloy and 105 Pa He > 105 Pa Ar > 103 Pa Ar > vacuum for Zr65Al7.5Ni10Cu17.5−xPdx (x = 0–17.5 %) bulk glassy alloys. The effectiveness of oxygen atmosphere is due to the suppression of crystal nucleation rate caused by the increase in surface tension of liquid by the dissolution of oxygen in case of Fe-based alloy. In case of Zr-based bulk glassy alloys, the He atmosphere is effective due to the maintenance of cleanness of alloy liquid as well as the increase in the cooling rate. The opposite tendency of the effectiveness for helium atmosphere in the same injection casting is important for further development of the production techniques for large-scale Fe- and Zr-based bulk glassy alloys.

Bulk Glassy Alloys: Historical Development and Current Research

ABSTRACT This paper reviews the development of current research in bulk glassy alloys by focusing on the trigger point for the synthesis of the first bulk glassy alloys by the conventional mold casting method. This review covers the background, discovery, characteristics, and applications of bulk glassy alloys, as well as recent topics regarding them. Applications of bulk glassy alloys have been expanding, particularly for Fe-based bulk glassy alloys, due to their unique properties, high glass-forming ability, and low cost. In the near future, the engineering importance of bulk glassy alloys is expected to increase steadily, and continuous interest in these novel metallic materials for basic science research is anticipated.

Alloy Designs of High-Entropy Crystalline and Bulk Glassy Alloys by Evaluating Mixing Enthalpy and Delta Parameter for Quinary to Decimal Equi-Atomic Alloys

The values of mixing enthalpy (¦Hmix) and Delta parameter (¤) were calculated with 73 elements from Miedema’s model for multicomponent equi-atomic alloys to investigate the possibilities of the alloys to be formed into high-entropy (H-E) alloys or high-entropy bulk metallic glasses (HE-BMGs). The equi-atomic alloys from about 15 million (73C5) quinary to 621 billion (73C10) decimal systems were evaluated by referring to a ¦Hmix­¤ diagram for zones S and B’s for H-E alloys with disordered solid solutions and BMGs, respectively, reported by Zhang et al. The results revealed that the number of quinary equi-atomic alloys plotted in zone S is 28405 (30.19% in 73C5), whereas those in zones B1 and B2 for conventional and Cuand Mg-based BMGs, respectively, were 1036385 and 21518 (36.90 and 30.14%), respectively. This kind of statistical approach using ¦Hmix­¤ diagram will lead to finding out unprecedented H-E alloys and HE-BMGs. [doi:10.2320/matertrans.M2013352]

Entropies in Alloy Design for High-Entropy and Bulk Glassy Alloys

High-entropy (H-E) alloys, bulk metallic glasses (BMGs) and high-entropy BMGs (HE-BMGs) were statistically analyzed with the help of a database of ternary amorphous alloys. Thermodynamic quantities corresponding to heat of mixing and atomic size differences were calculated as a function of composition of the multicomponent alloys. Actual calculations were performed for configurational entropy (Sconfig.) in defining the H-E alloys and mismatch entropy (Ss) normalized with Boltzmann constant (kB), together with mixing enthalpy (DHmix) based on Miedema’s empirical model and Delta parameter (d) as a corresponding parameter to Ss/kB. The comparison between DHmix–d and DHmix– diagrams for the ternary amorphous alloys revealed Ss/kB ~ (d /22)2. The zones S, S′ and B’s where H-E alloys with disordered solid solutions, ordered alloys and BMGs are plotted in the DHmix–d diagram are correlated with the areas in the DHmix – Ss /kB diagram. The results provide mutual understandings among H-E alloys, BMGs and HE-BMGs.

Microstructure and magnetic properties of soft magnetic composites based on silicon resin coated Co40Fe22Ta8B30 glassy powders

In this paper, new Co40Fe22Ta8B30 bulk glassy and composite cores were prepared by powder metallurgy method. The Co40Fe22Ta8B30 glassy powder precursor was obtained by controlled ball milling of the melt-spun amorphous ribbons. As-milled metallic powders, as well as metallic powder particles coated by a silicon resin with very high thermal stability, were hot pressed at temperatures above the glass transition temperature of the metallic alloy powders. Therefore, monolithic glassy samples, as well as composite cores with high relative density, were obtained. The X-ray diffraction (XRD) and differential scanning calorimetry (DSC) analyses confirmed that no devitrification was happened upon consolidation. The elemental mapping analysis using the energy dispersive X-ray method (EDX) indicated that the glassy powders were electrically insulated by silicone resin after hot pressing. The monolithic glassy cores showed a high relative density of 99% and wide supercooled liquid region of 74 K before crystallization, which is the same as that of the as-cast and ball milled Co40Fe22Ta8B30 amorphous ribbons. In addition to high thermal stability, the monolithic glassy cores exhibited good soft magnetic properties, e.g. high initial permeability of 1500, low coercivity of 13 A/m and magnetization of 43 Am2/kg at f = 100 Hz. Addition of the silicon resin was effective to enhance the electrical resistivity and frequency stability of the initial permeability. The relaxation frequency of compacted cores increased from 1.1 kHz for monolithic glassy samples to 36 kHz upon addition of 2.5 wt.% silicon resin. In addition, Co40Fe22Ta8B30 glassy composites showed high initial permeability of 575 up to 14 kHz and low DC coercivity of 30 A/m.

Research on Cu-Based Bulk Glassy Alloys and its Mechanical Properties

High-strength Cu-based bulk glassy alloys with a large supercooled liquid region in Cu-Zr-Ti-Ni systems were prepared by means of copper mold casting. The Cu-based bulk glassy alloys samples were tested by X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and Instron testing machine. The result indicates, the maximum diameter was 5.0 mm for the Cu55Zr25Ti15Ni5 bulk glassy alloy. The temperature interval of supercooled liquid region (ΔTx) is as large as 45.48-70.98 K for the Cu-Zr-Ti-Ni alloy. The Cu-based glassy alloys rods exhibited the very high mechanical properties and the distinct plastic strains. The compressive fracture strength is 2155 MPa, 2026 MPa and 1904 MPa respectively for Cu50Zr25Ti15Ni10, Cu55Zr25Ti15Ni5 and Cu54Zr22Ti18Ni6 bulk glassy alloys. The Vickers hardness is respectively 674, 678 and 685 for the Cu50Zr25Ti15Ni10, Cu55Zr25Ti15Ni5 and Cu54Zr22Ti18Ni6 bulk glassy alloys. The addition Co element to Cu-Zr-Ti-Ni alloy expand the ΔTx, the ΔTx is 74.5 K for Cu50Zr22Ti18Ni6Co4 bulk glassy alloys.

Effect of Nb Addition on the Glass-Forming Ability, Soft-Magnetic Properties and Mechanical Properties of CoFeNiBSiNb Bulk Glassy Alloys

The effect of Nb addition on the glass-forming ability (GFA), soft-magnetic properties and mechanical properties of [(Co0.65Fe0.35)0.9Ni0.1]73-xB21.9Si5.1Nbx(x=36) alloy system were investigated. The results showed that by adjusting the content of Nb, the thermal stability of the supercooled liquid and the GFA increased effectively. With increasing the amount of Nb, the supercooled liquid region (ΔTx) increased from 45 to 65 K and the reduced glass transition temperature (Trg=Tg/Tl) was located in the range of 0.5840.644. As a result, the [(Co0.65Fe0.35)0.9Ni0.1]73-xB21.9Si5.1Nbx bulk glassy alloys (BGAs) with diameters up to 5.0 mm were produced by copper mold casting. In addition to the high GFA, the Co-based glassy alloys exhibited excellent soft-magnetic properties, i.e., saturation magnetization of 0.530.81 T, low coercive force of 0.511.75 A/m, and high effective permeability of (1.522.53)×104 at 1 kHz under a field of 1 A/m. Besides, the Co-based BGAs also exhibited super high fracture strength of 42704490 MPa and vickers hardness of 11271182.

Preparation and Corrosion Resistance of Cu-Based Bulk Glassy Alloys

The Cu-based bulk glassy alloys in Cu-Zr-Ti-Ni systems were prepared by means of copper mold casting. The structure and corrosion resistance of Cu-based bulk glassy alloys were analyzed by X-ray diffraction (XRD), differential scanning calorimetry (DSC), electrochemistry method, lost weight method. The result indicates the supercooled liquid temperature interval (ΔTx) is up to 70.98 K for Cu50Zr25Ti15Ni10 bulk glassy alloy. The maximum diameter was up to 5.0 mm for the Cu55Zr25Ti15Ni5 bulk glassy alloy. For electrochemistry corrosion in 3.5% NaCl solution, self-corrosion electric current density of the Cu50Zr25Ti15Ni10 bulk glassy alloys is obviously lower than that of stainless steel and brass, so corrosion resistance of Cu-based bulk glassy alloys is better than stainless steel and brass at the same corrosion condition. The lost weight method showed that the corrosion rate of brass, stainless steel and glassy alloy is respectively 10.08 g/(m2•h), 6.08 g/(m2•h) and 2.19 g/(m2•h) in the 3% NaCl solution, which also indicates that the corrosion resistance of Cu-based bulk glassy alloys is better than stainless steel and brass. The Cu-based bulk glassy alloys can be used in the special field demanding to have the super high strength, hardness and corrosion resistance.

Glass Forming Ability and Magnetic Properties of Fe36Ni36B19.2Si4.8Nb4−x M x (M=Cu, Zr, Ti, Y, Pt) Bulk Glassy Alloys Fabricated by Suction Casting

In this study, the effects of Cu, Zr, Ti, Y, Pt substitution for Nb additions on the stability and magnetic properties of Fe-Ni-based bulk metallic glass (BMG) alloys fabricated by the suction casting method are investigated. The saturation magnetization (J s) and coercivity (H c) for as-cast Fe36Ni36B19.2Si4.8Nb4−x M x (M=Cu, Ti) BMG alloys were in the range of 0.51 T–0.55 T and 76–779 A/m, respectively. Differential scanning calorimetry curves show that the Fe36Ni36B19.2Si4.8Nb4−x M x (M=Cu, Ti) bulk metallic glasses have a supercooled liquid region for Cu at 44 K and for Ti at 39 K.