Bulk Glassy Alloys Research Articles

Fe-based amorphous coatings: Structures and properties

Bulk metallic glasses (BMGs), also called amorphous alloys, have totally different structure from the conventional crystalline metals and are well-known for their high strength and high hardness, large elastic limits, and, in particular, for their outstanding corrosion and wear resistance. During the past several decades, despite the understanding gained on the formation and microstructure, as well as the mechanisms related to their unique mechanical properties that have achieved great progress, industrial applications of BMGs are still very scant due to mostly the poor ductility at room temperature. In contrast, amorphous coatings based on BMG systems have received increasing attention and interest in recent years because of the combination of the excellent properties inherited from the bulk glassy alloys and the potential engineering applications for amorphous coatings. In this article, we briefly summarize the past development and the recent progress of amorphous coatings made in our group in terms of fabrication, microstructure, thermal stability, and properties such as corrosion and wear resistance, bonding strength and wettability. In addition, we also describe simply the foreseen potential applications and future developments of this kind of materials.

Positron annihilation study of free volume in electron irradiated Zr50Cu40Al10 bulk glassy alloy: Effects of thermal relaxation before irradiation

Change in free volume reflects various properties such as hardness and ductility of glassy alloys. The electron- and ion- irradiations affect the free volume of ZrCuAl bulk glassy alloys that is associated with the mechanical properties. In this study, as-quenched Zr50Cu40Al10 bulk glassy alloys and structural relaxed one by annealing for 5 hours at 673K below glass transition temperature (Tg) were irradiated by 8 MeV electrons with a maximum fluence of about 2×1018 e−/cm2 at room temperature. The behaviour of free volume in these samples was investigated by positron annihilation techniques. X-ray diffraction measurements showed that no crystallization occurred after the irradiation. We observed the positron lifetime increased by the irradiation for both as-quenched and structural relaxed samples. The increases in positron lifetime at 2×1018 e−/cm2 were 9 psec for as-quenched and 12 psec for relaxed sample, respectively. In addition, the increase in positron lifetime with irradiation fluence was clearly different for the two types of sample. These facts imply that the thermal relaxation before irradiation of Zr50Cu40Al10 bulk glassy alloy influences the radiation effects, especially the free volume change.

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.

Irradiation effect of swift heavy ion for Zr50Cu40Al10 bulk glassy alloy

It has been reported that heavy ion irradiation causes softening in some cases of Zr-based bulk metallic glass alloys. However, the fundamental mechanisms of such softening have not been clarified yet. In this study, Zr50Cu40Al10 bulk glassy alloys were irradiated with heavy ions of 10MeV I at room temperature. The maximum fluence was 3×1014ions/cm2. The positron annihilation measurements have performed before and after irradiation to investigate changes in free volume. We discuss the relationship between the energy loss and local open volume change after 10MeV I irradiation compared with those obtained for 200MeV Xe and 5MeV Al. The energy loss analysis in ion irradiation for the positron lifetime has revealed that the decreasing trend of positron lifetime is well expressed as a function of total electronic energy deposition rather than total elastic energy deposition. It means that the positron lifetime change by the irradiation has a relationship with the inelastic collisions with electrons during heavy ion irradiation.

Iron-based bulk metallic glasses

The current status of research and development in Fe-based bulk metallic glasses (BMGs) is reviewed. Bulk metallic glasses are relatively new materials possessing a glassy structure and large section thickness. These materials have an exciting combination of properties such as high mechanical strength, good thermal stability, large supercooled liquid region and potential for easy forming. Ever since the first synthesis of an Fe-based BMG in an Fe–Al–Ga–P–C–B system in 1995, there has been intense activity on the synthesis and characterisation of Fe-based BMGs. These BMGs exhibit some unique characteristics which have not been obtained in conventional Fe-based crystalline alloys. This uniqueness has led to practical uses of these bulk glassy alloys as soft magnetic and structural materials. This review presents the recent results on the glass-forming ability, structure, thermal stability, mechanical properties, corrosion behaviour, soft magnetic properties and applications of Fe-based bulk glassy alloys developed during the last 15 years. This review also highlights the advanced analysis of their properties which has contributed significantly to the progress in understanding and developing of the Fe-based BMGs. The future prospects of Fe-based BMGs have also been presented.

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.

High entropy Ti20Zr20Cu20Ni20Be20 bulk metallic glass

In this letter, we report that a new bulk metallic glass (BMG) of Ti20Zr20Cu20Ni20Be20, with a critical diameter of 3mm, has been successfully fabricated using copper mold casting method. Different from most reported BMGs which possess one or two main constituents, this newly developed BMG possesses five elements with equal atomic concentration, which has been defined as high entropy alloy. This high entropy bulk metallic glass (HE-BMG) exhibits high fracture strength of 2315MPa but a brittle behavior. The glass forming ability, mechanical property and phase transformation after annealing of the HE-BMG are discussed in detail. And a way for designing high entropy bulk glassy alloy has been proposed.

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.

Effect of Ti substitution on glass-forming ability and mechanical properties of a brittle Cu–Zr–Al bulk metallic glass

Starting from the brittle Cu46Zr46Al8 bulk metallic glass (BMG), the effect of substituting Al by Ti on the glass-forming ability (GFA) and the mechanical properties is systematically investigated. The supercooled liquid region (ΔTx), the reduced glass transition temperature (Trg=Tg/Tliq) and the γ parameter (γ=Tx/(Tg+Tliq)) tend to decrease with increasing Ti content in the present Cu46Zr46Al8−xTix (0≤x≤8) alloys. An increasing distance from the eutectic point might be the origin of the reduced GFA after the Ti addition. At the same time, the Ti additions significantly increase the plasticity of the respective alloys. The Cu46Zr46Ti3.2Al4.8 bulk glassy alloy is found to have the largest plastic strain in compression of around 12% and a fracture strength up to 1950MPa while the Ti-free Cu46Zr46Al8 BMG exhibits values of 0% and 1754MPa, respectively. The statistics of the serrated flow behavior, which is closely related with the dynamics of shear bands, are also investigated. The macroscopic and microscopic mechanisms, which contribute to the enhancement of malleability, are analyzed.

Direct visualization of Ni-Nb bulk metallic glasses surface: From initial nucleation to full crystallization

This article is devoted to in situ investigation of the Ni-based bulk metallic glass structural evolution and crystallization behavior by scanning tunneling microscopy/spectroscopy. The possibility of different surface nanostructures formation is shown by annealing of an original bulk glassy alloy in ultra high vacuum. Atomic locations in these surface nanostructures are completely different from those formed according to Ni-Nb binary phase diagram in the bulk area of the sample. The validity of the results is also verified by transmission electron microscopy and nano-beam diffraction measurements.

Formation and microstructure of Ni62- x Nb38Ti x (x = 3, 6, 10 at.%) bulk metallic glasses

Abstract In this work we report the formation and microstructure of Ni62- x Nb38Ti x (x = 0, 3, 6, 10 at.%) bulk metallic glasses (BMGs). The addition of Ti to Ni–Nb binary alloys is effective for the increase in stabilization of supercooled liquid and glass-forming ability (GFA). The maximum supercooled liquid region (ΔT x) of 46 K and the reduced glass transition temperature (T rg) of 0.61 were obtained for Ni56Nb38Ti6, leading to the formation of the bulk glassy alloys. The best GFA was obtained for Ni56Nb38Ti6 alloy which was located near the eutectic composition of the ternary component alloy, and glassy alloy samples up to 0.5 mm were fabricated through wedge copper mold casting. The new Ni–Nb-based bulk glassy alloys exhibit large ΔT x of 35 to 46 K. The Ni62- x Nb38Ti x (x = 0, 3, 6, 10 at.%) BMGs showed high Vickers microhardness in the range of 988 to 1140 HV representing good mechanical properties.

Recent Progress in the Industrialization of Metallic Glasses

Metallic Glasses (MGs), also called glassy metals (amorphous metals, liquid metals) are considered to be the materials of the future. Metallic glasses, formed at very low critical cooling rates, are different from traditional amorphous alloys (which are usually formed at high cooling rates) in order to avoid crystallization. The most important feature of MGs, which distinguishes them from ordinary amorphous materials, is the glass transition that transforms super cooled liquids into a glassy state when cooled from high to low temperature. Some scientists have been investigating the mechanisms and dynamics of metallic glass formation, their atomic structure, micromechanisms of mechanical properties, etc. They have also been exploring the atomic-scale mechanisms of MG formation and the development of new bulk glassy alloys and composites with improved glass-forming ability. Other scientists focus on manufacturing and industrialization of MGs. At the Chinese Academy of Sciences (CAS), there are currently more than 30 groups working on the science, preparation and applications of MGs. The Amorphous Materials and Physics Group at CAS has developed a series of rare earth-based RE-MGs with functional physical properties. In the US, there are science groups that have made successful progress in the area of metallic glasses. More specifically, the US-based team from Yale and the science group from Caltech are more focused on practical aspects relating to MGs (production, industrialization, biomedical materials and aerospace materials). This patent review article briefly investigates the industrialization and some environmental aspects of MGs, as follows: biocompatibility of most MGs, obtaining valuable MGs from low-purity industrial raw materials, use of MGs in green energy applications (solar cells, hydrogen production), use of MGs in catalyst systems and possibilities for using metallic glasses in systems for retention and purification of dangerous pollutants. Keywords: Aerospace, atomic structure, biomedical, defence, environmental, glass forming ability, green energy, metallic glasses, new alloys, processing, solar cells, hydrogen production

Effect of Co Addition on the Glass-Forming Ability and Mechanical Properties of Ti-Zr-Be-Cu-Co Bulk Amorphous Alloys

The effect of Co substitution for Be on the glass-forming ability and mechanical properties was investigated in Ti35Zr30Be27.5-xCu7.5Cox (x=0, 3.5, 7.5, 11.5 at.%) alloys by using X-ray diffractometry (XRD), differential scanning calorimetry (DSC), high-resolution transmission electron microscopy (HRTEM) and compression test. With the substitution of Co for Be, glass-forming ability (GFA) is significantly enhanced and fully amorphous rods with a diameter of up to 12 mm were produced in the alloy with 3.5 and 7.5 at.% Co. The Ti35Zr30Be24Cu7.5Co3.5 bulk glassy alloy exhibits good plasticity of 4% during compressive applied load at ambient temperature in conjunction with distinct yield strain of 2% and high fracture strength of 2196 MPa. The effect of the addition of Co on the structure and deformation behavior of the Ti35Zr30Be27.5-xCu7.5Cox (x=0, 3.5, 7.5, 11.5 at.%) alloys is discussed.

Preparation of thin ribbon and bulk glassy alloys in CoFeBSiNb(Ga) using planar flow casting and suction casting methods

Co-based ferromagnetic bulk glassy alloy (BGA) system is promising for future applications as new structural and functional materials. In the present paper as-cast Co47Fe20.9B21.2Si4.6Nb6.3 bilayer, ribbon, rods with diameter up to 5mm and [Co47Fe20.9B21.2Si4.6Nb6.3]98Ga2 as-cast ribbon as well as rod with 4mm diameter were investigated. Co based master ingots with the composition Co47Fe20.9B21.2Si4.6Nb6.3 have been prepared in a vacuum furnace. The as-prepared master ingots were then purified by fluxing. Small amount of gallium (2at.%) was added into one part of the purified master alloy. Ribbons, bilayer and bulk samples in form of rods were prepared by subsequent planar flow casting and suction casting method, respectively. Glassy structure of as-cast samples was examined by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Thermal stability associated with glass transition temperature (Tg), crystallization temperature (Tx) and supercooled liquid region (∆Tx=Tx–Tg) were examined by differential scanning calorimetry (DSC). The Curie temperature of the investigated ribbons and rods was determined by magnetic thermogravimetry analysis (TGA). Using special disc-shaped samples field dependencies of magnetostriction in parallel and perpendicular directions of the applied magnetic field were obtained by direct measurement.

The Effect of Microstructural Changes Induced by Annealing on Mechanical Properties of FeCoCrMoCBY Bulk Glassy Alloy

Bulk metallic glasses have interesting mechanical properties, such as high strength up to 5 GPa, high elastic strain and many other additional desirable properties. However, BMGs beyond the elastic region fail catastrophically on one dominant shear band and show little macroscopic plasticity in an apparently brittle manner. Nano-crystallized BMGs have been found to possess better ductility comparing with brittle parent BMGs. Annealing treatment of glassy alloys is a useful method to prepare bulk nano-crystalline alloys. In the present study, the crystallization trend of the FeCoCrMoCBY alloy which is claimed to have the best glass forming ability was studied in various times in temperature ranges of a) between Tg (glassy temp.) and Tx1 (first crystallization temp.), and b) between Tx1 and Tx2 (second crystallization temp.). The influences of different annealing time and temperatures on the microstructure and microhardness of Fe41Co7Cr15Mo14Y2C15B6 BMG are reported in this paper.

The Effect of Co Addition on Glassy Forming Ability and Soft Magnetic Properties of Fe-Si-B-P Bulk Metallic Glass

We Successfully Prepared the Rod Glassy Samples of (Fe1-xCox)76Si9B10P5(x= 0~0.4) Bulk Metallic Glass (BMG) with the Diameters up to 3.0 mm by Substituting Fe for a Small Amount of Co Element. A Certain Amount of Co Substitution for Fe Contributes to the Increase of the Glass-Forming Ability (GFA) while Maintaining Good Mechanical Properties (the Fracture Strength up to 3700 MPa). This Co-Added Ferromagnetic Bulk Glassy Alloy System Also Exhibits a Higher Saturation Magnetization of 1.49 T and Lower Coercive Force (Hc, 1.2 A/m). The Fe-Based BMGs with Alloying a Small Amount of Co Element Demonstrate Excellent Combination of High GFA, Good Soft-Magnetic Properties as Well as High Strength.

Enhancement of glass-forming ability of FeSiBP bulk glassy alloys with good soft-magnetic properties and high corrosion resistance

The effect of Nb micro-addition on the glass-forming ability, magnetic and corrosion properties of (Fe0.76Si0.09B0.1P0.05)100−xNbx (x=0–4) alloy system was investigated. It was found that micro-addition of 1% Nb is effective in increasing the critical diameter for glass formation from 2.5 for the base alloy to 3.5mm for (Fe0.76Si0.09B0.1P0.05)99Nb1 glassy alloy. Moreover, the 1% Nb-containing glassy alloy exhibits excellent soft-magnetic properties, i.e., high saturation magnetization (Is) of 1.45T and low coercive force (Hc) of 1A/m. A significant improvement in corrosion resistance of the glassy alloys with Nb micro-alloying in 1N H2SO4 solution is also observed. The good combination of high glass-forming ability (GFA), excellent soft-magnetic properties and enhanced corrosion resistance indicates the possibility of future development as new engineering and functional materials.

Soft magnetic properties of bulk FeCoMoPCBSi glassy core prepared by copper mold casting

Bulk Fe66Co10Mo3.5P10C4B4Si2.5 glassy core of 10 mm in outer diameter, 6 mm in inner diameter, and 1 mm in thickness was successfully prepared by copper mold casting. The effects of annealing treatments on magnetic properties and microstructure of these cores were investigated. After an optimum annealing treatment, the resulting bulk glassy core exhibits good magnetic properties, i.e., high saturation magnetic flux density of 1.23 T, low coercive force of 1.0 A/m, high maximum permeability of 450 000, respectively. In addition, the glassy core also shows low core loss of 0.4 W/kg at 50 Hz and at maximum magnetic flux density of 1 T. The synthesis of bulk glassy core with excellent magnetic properties is encouraging for enlarging the application field of ferromagnetic bulk glassy alloys.

Bulk glassy (Fe0.474Co0.474Nb0.052)100 − x(B0.8Si0.2)x alloys prepared using commercial raw materials

The alloy compositions have been optimized by modifying the B and Si contents in (Fe0.474Co0.474Nb0.052)100−x(B0.8Si0.2)x alloy system with commercial materials. The thermal stability of the supercooled liquid improves with the increased B and Si contents from x=22 to 28. The composition of the alloy with x=26 is close to a eutectic point. By copper mold casting, (Fe0.474Co0.474Nb0.052)100−x(B0.8Si0.2)x bulk glassy alloys with diameters up to 5mm were synthesized for the composition range of x from 22 to 28. In addition to high glass-forming ability (GFA), the (Fe0.474Co0.474Nb0.052)100−x(B0.8Si0.2)x glassy alloys exhibit good soft magnetic properties as well, i.e., rather high saturation magnetization of 0.84–1.07T, low coercive field of 1.8–3.2A/m, high initial permeability of 10100–24100 at 1kHz under a field of 1A/m and Curie temperature of 620–730K.