Review-Recent Progress in the Industrialization of Metallic Glasses-Eugen2012[1]

Recent Patents on Materials Science 2012, 5, 213-221213 Recent Progress in the Industrialization of Metallic Glasses
Eugen M. Axinte* and Marius P.I. Chirileanu
“Gheorghe Asachi” Technical University of Iasi, Faculty of Machine Manufacturing and Industrial Management, Iasi, Romania
Received: January 27, 2012; Accepted: February 15, 2012; Revised: February 26, 2012
Abstract: 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 mecha-
nisms 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 al-
loys 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 Cal-
tech are more focused on practical aspects relating to MGs (production, industrialization, biomedical materials and aero-
space 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.
1. INTRODUCTION
Metallic glasses are defined as amorphous alloys that exhibit a glass transition, from which their properties of ex-treme strength at low temperatures and high flexibility at high temperatures are derived, along with thermodynamic and physical properties that change abruptly at the glass transition temperature (Tg).
The first scientifically obtained metallic glass reported was the Au75Si25 alloy produced at Caltech by Klement, Wil-lens and Duwez in 1959, through extremely rapid cooling of the melted alloy (nearly 106 K per second).
An important consequence of high cooling rates in the formation of metallic glasses was that metallic glasses could only be produced in a limited number of forms (typically ribbons, foils, or wires) in which one dimension was small so that heat could be extracted quickly enough to achieve the necessary cooling rate [1, 2]. As a result, metallic glass specimens (with a few exceptions) were limited to thick-nesses of less than one hundred micrometers. A few excep-tions were found in noble metal-based alloys, such as Pd- Cu-Si alloys. These alloys have very low critical cooling rates of ~10Ks–1 and can make glassy samples with a bulk *Address correspondence to this author at the Gh.Asachi Technical Univer-sity of Iasi Faculty of Machine Manufacturing & Industrial Management .59 A -Prof. Dimitrie Mangeron Blvd, Iasi, Romania;
Tel:/Fax: (04)023*******; E-mail: axintee@tuiasi.ro impact on the materials science community. This is in part due to the fact that “although the noble metals of palladium and platinum are good for improving glass-forming ability, they are too expensive to be used for a wide range of appli-cations” [2].
In the 1990s, new alloys were developed that formed glasses at cooling rates as low as 1Ks-1. Such cooling rates can be achieved by simple casting into metallic moulds. These "bulk" amorphous alloys can be cast into parts of up to several centimetres in thickness (the maximum thickness depending on the alloy) while retaining an amorphous struc-ture. The best glass-forming alloys are based on zirconium and palladium, but alloys based on iron, titanium, copper, magnesium, and other metals are also known. In recent years, extensive investigations were transferred to novel multi-component bulk glass-forming alloy systems, mostly to Zr-based alloys, but also more and more to Pd-, Fe-, Cu, Ni-, Pr-, Nb- and Nd-based systems.
Metallic glasses are at the cutting edge of research and they are of considerable significance in condensed matter physics, material science and engineering [3].
2. RECENT PROGRESS IN RESEARCH ON METAL-LIC GLASSES
2.1. Brief on the Local Structure of MGs
According to [4-7], there are two major challenges in the study of MG structures: how to construct a realistic three-
1874-46 /12 $100.00+.00 © 2012 Bentham Science Publishers
214 Recent Patents on Materials Science 2012, Vol. 5, No. 3 Axinte and Chirileanu dimensional (3-D) amorphous structure, using experimental
and/or computational tools and how to effectively character-
ize a given amorphous structure and extract the key struc-
tural features relevant to the fundamentals of glass formation
and properties, using appropriate structural parameters.
Structural models, such as Bernal’s “dense random packing”
and Gaskel’s “short-range order” have been proposed in the
past fifty years.
In [6], the authors reported their direct observation of the
distinct patterns that result from the diffraction of an electron
beam from individual atomic coordination polyhedra inside a metallic glass. This study provides compelling evidence of the local atomic order in the disordered material and has im-portant implications in understanding the atomic mecha-nisms of metallic-glass formation and its properties.
A simulated model of glassy Zr66.7Ni33.3, which shows the atomic configuration with 198 atoms (132 Zr and 66 Ni), is presented in Fig. (1).
Fig. (1). A structural model with 132 Zr atoms (white spheres) and 66 Ni atoms (blue spheres). (Extracted and reproduced with permis-sion from [6] Copyright © 2010, Nature Publishing Group).
Recently, it was proposed and demonstrated that the structure of metallic glasses can be best viewed as compris-ing interpenetrating quasi-equivalent clusters (coordination polyhedra). Each atom in the alloy is surrounded by a pre-ferred number of neighbours in preferred proportions and with a preferred geometry Fig. (2).
The intimate structure of metallic glasses is far from be-ing completely understood and elucidated and it is very dif-ficult to describe and quantify. Predictions about how atomic structure influences the macroscopic properties of MGs are still difficult to make.
2.2. Recent Research on MG Behaviour
All studies conclude that MGs have much higher tensile strengths and much lower Young’s moduli. The difference in the values corresponding to MGs versus those of crystalline Fig. (2). High-resolution TEM image of a low-carbon steel crystal showing well-defined lattice fringes. Inset, the corresponding se-lected-area electron diffraction pattern showing sharp spots. (a) High-resolution TEM image (b) of the Zr67Ni33 metallic glass2, showing a maze-like pattern. Inset, the corresponding selected-area electron diffraction pattern shows diffuse haloes, in stark contrast with the crystalline pattern in a. (Courtesy of A. Hirata and M. W. Chen, Tohoku University.) (Adapted with permission from [7] © 2011 NPG).
alloys is as large as 60%. The significant difference in me chanical properties is thought to be a reflection of the differ-ence in the deformation and fracture mechanisms between MGs and crystalline alloys. Plastic deformation in metallic glasses is generally associated with inhomogeneous flow in highly localized shear bands.
In [8], the authors prepared bulk MG samples using a copper mould suction casting method. The amorphous rib-bons were obtained through the melt spinning technique. A study of the similarity and correlations between relaxations and plastic deformation in metallic glasses (MGs) and MG-forming liquids was provided. Figure 3 schematically illus-trates the flow based on the concept of potential energy landscape (PEL).
Fig. (3). Schematic illustration of the flow based on the concept of potential energy landscape (PEL) (adapted with permission from [8] © 2011 Elsevier).
The arrows indicate the possible motion of atoms. The potential shear transformation zone (STZ) events are lo-calized with cooperative nature and are reversible due to
Industrialization of Metallic Glasses Recent Patents on Materials Science 2012, Vol. 5, No. 3 215
confinements of surrounding materials, while -relaxa-tion (percolation of STZs, or plastic flow and yielding) incorporates large scale atomic migration and irreversi-bility).
In [9], the authors reported a strain-rate-dependent plas-ticity in a Zr-based bulk metallic glass (BMG) under axial compression. The dynamic shear-band operations in a Zr based BMG were investigated during compression at various strain rates, reflecting that the shear band events are highly dependent on strain rates. This research may open new hori-zons in understanding strain-rate-dependent plastic deforma-tion (shear-band operations) of MGs.
Metallic glass composites (MGCs) were developed to improve plasticity of metallic glasses. In [10], the authors used a monochromatic X-ray beam to map the distributions of lattice strain under compressive loading mode.
In [11], the authors reported the formation of a series of high mixing entropy MGs based on multiple major elements, which have excellent glass- forming ability and mechanical properties compared to conventional MGs. The high mixing entropy MGs based on multiple major elements may be of significance in scientific studies. This research provides a novel approach in the search for new metallic glass-forming systems.
A team led by Mao from Carnegie Geophysical Labora-tory created a metallic glass ordered at large scale (LRO). A single crystal was obtained by applying 25GPa of pressure (equivalent to 1800 tons per square inch) to the cerium-aluminium glass and the new order formed is preserved even when the glass is restored to ambient pressure [12-14].
The experiment is illustrated schematically in Fig. (4). Fig. (4). Experimental schema for obtaining a metallic glass or-
dered at large scale (adapted from [14] © 2011 Carnegie Institute).
3. ASPECTS OF MG INDUSTRIALIZATION
Below is a brief evaluation of some current aspects relat-ing to MG uses and industrialization, including: biocompati-bility of most MGs, obtaining valuable MGs from low-purity raw materials and use of MGs in green energy applications (solar cells, hydrogen production). 3.1. MGs for biomedical applications
Some metallic glasses (as Pd-based MGs) exhibit good properties as biomedical materials: non-toxicity, good corro-sion resistance, good toughness characteristics.
The invention described in [15] is aimed at Pd-based me-tallic glass alloys useful in biomedical applications having no Ni or Cu. Pd-based metallic glasses generally have the required modulus and toughness characteristics and are able to form three-dimensional metallic glass objects of sufficient thickness for biomedical applications. These metallic glasses include at least one of Ni and Cu (and often both), likely making them non-biocompatible and therefore not suitable for use in biomedical applications. However, because Pd-based metallic glasses have desirable modulus and toughness characteristics, the present invention is directed towards Pd-based metallic glasses free.The cytotoxicity of the newly developed Pd-based glassy alloy was evaluated by an in vitro biocompatibility study. Also, the cytotoxicity of Pd-based glassy test article was evaluated through an in vivo biocom-patibility study. The test article was implanted into the mus-cle tissue of a rabbit. The muscle tissue was evaluated for evidence of irritation or toxicity. In vitro and in vivo cytotox-icity tests revealed that the newly developed Pd-based glassy alloy is fully biocompatible.
US7998286 [16] describes MGs and, more particularly, a subset of Zr-Ti-based MGs with improved corrosion resis-tance properties. BMGs are designed by carefully controlling concentration of, or completely removing highly electro-negative elements, such as Ni and Cu from Zr-Ti-based bulk solidifying amorphous alloys thereby producing BMG mate-rials with corrosion resistance properties that far exceed those of current commercially available MGs and most con-ventional alloys. The elimination of these electronegative materials also opens the possibility of new uses for MGs, including in biological applications.
The invention described in US7887584 [17] provides an artificial heart component, such as an artificial heart valve or a pacemaker, wherein the artificial heart component includes an amorphous metal alloy component. The artificial heart valve may be a ball valve comprising an amorphous metal alloy cage. Alternatively, the artificial heart valve can in-clude leaves made of amorphous metal alloy. The pacemaker containing the amorphous metal alloy may house an energy source which is shielded from the body by the amorphous metal alloy. This invention may be applied in: sutures, im-plantable surgical fabrics, stents, heart valves, implants for reconstructive surgery, orthodontic and dental implants, all of these comprising amorphous metal alloys.
In patent [18], the authors describe an implant having a substantially solid basic structure and a porous jacket struc-ture at least partially enclosing the basic structure for at-tachment of cellular tissue wherein the basic structure and the jacket structure are connected integrally to each other and the porous jacket structure is formed substantially by a struc-ture with open pores. The disclosure also relates to a method for manufacturing such an implant.
Researchers at ETH Zurich have developed a new amor-phous alloy that opens the way for a new generation of
216 Recent Patents on Materials Science 2012, Vol. 5, No. 3 Axinte and Chirileanu biodegradable bone implants. The new metallic glass
(MgZnCa) synthesized by Zberg and his team, under the
leadership of Löffler, shows a fundamentally different be-
haviour from previous materials synthesized in the past, and
appears to eliminate the problem of hydrogen-forming gas
[19].
In Fig. (5), plasma of up to 3000°C is produced between
a tungsten tip (centre) and a water-cooled copper plate.
Fig. (5).Arc melter for producing MGs for bone surgery (adapted with permission from [19] © 2009 NPG Credit: ETH Zu-rich/LMPT).
Porous prostheses have been gaining importance, in light
of their ability to guide cells and aid with tissue repair. Inter-connected pore architectures with pore sizes in the range of
75-250μm are thought to be optimal for tissue ingrowth. In
addition to eliciting cell attachment and tissue ingrowth, po-
rosity functions to reduce the structural properties of mono-
lithic bulk materials to values closer to those of natural bone.
Owing to their high strength combined with relatively low moduli, amorphous metals can be thought as attractive base materials for developing strong highly-elastic porous solids capable of matching the mechanical properties of cancellous bone [20]. A porous amorphous structure (88% porosity) is shown in Fig. (6).
Fig. (6). Amorphous porous Pd-Ni-Cu-P foam and micrographs of the cellular structure at high magnifications (adapted with permis-sion [20] © 2010 Elsevier).
Zirconium-based BMGs are used in surgical instruments, such as surgical razors or micro-surgery scissors. Razors made using Zr BMG present much smoother edges than stainless steel razors [21] (see Fig. (7)). Fig. (7). Surgical instruments made from Zr-based BMG(adapted and reproduced with permission from [21] ©2009 Elsevier).
3.2. MGs in Catalyst Systems
Schroers and colleagues developed Pt57.5Cu14.7Ni5.3P22.5
bulk metallic glass (Pt-BMG) nanowires. The Pt-BMG
nanowires have high surface areas, thereby exposing more of
the catalyst, and also maintaining their activity longer than
traditional fuel cell catalyst systems. After 1,000 cycles, these nanowires maintained 96% of their performance-2.4
times more than conventional Pt/C catalysts [22] (See Fig.
(8)).
Fig. (8). Pt-BMG nanowires for catalyst systems (adapted with permission from [22]).
3.3. MGs in Defence and Aerospace Applications
Depleted-uranium-based (DU) alloys have traditionally been used in the production of solid metal, armour-piercing projectiles known as kinetic energy penetrators (KEPs). The combination of high density and high strength make depleted uranium ideal for ballistics applications. Depleted-uranium-based (DU) is particularly suitable for KEPs because its complex crystal structure promotes shear banding when plas-tically deformed. When DU penetrators hit a target at very high speeds, they deform in a "self-sharpening" behaviour.
Scientists at the US Department of Energy's Ames Labo-ratory are close to developing a new composite with an in-ternal structure resembling fudge-ripple ice cream
that is
Industrialization of Metallic Glasses
Recent Patents on Materials Science 2012, Vol. 5, No. 3 217 actually comprised of environmentally safe materials to do the job even better [23].
The US Department of Defence (DoD) has extensively researched Liquid metal Technologies for KEPs. Ballistic tests conducted by the US Army have proven that some spe-cial tungsten-based metallic glass composites exhibit self-sharpening similar to the DU KEP, but are environmentally benign. The main attributes (high strength and lightweight) of liquid metal alloys enable the DoD to support its trans-formation toward lighter, smaller and more cost effective systems (Fig. (9)) [24].
Fig. (9). BMG Kinetic Energy Penetrators produced by Liquid-Metal Technologies (adapted from [24]).
NASA’s Genesis Spacecraft used solar wind collectors made of a new formula of bulk metallic glass (Fig. (10)) [1, 25, 26].
Fig. (10). BMG solar wind collector of NASA’s Genesis Spacecraft (adapted from [1] © 2011 Elsevier, [25, 26] credit NASA).
A complex mixture of zirconium, niobium, copper, nickel, and aluminium (a new BMG forming alloy) was de-signed by Hays in the Caltech Materials Science Laborato-ries.
The new BMG was prepared in a collaborative effort by Hays and Wolter (Howmet Co., Greenwich, Conn). The sur-faces of metallic glasses dissolve evenly, allowing the cap-tured ions to be released in equal layers. Solar wind higher energy ions penetrate into the metal surface of the collector. The samples returned to Earth in a Stardust-like sample-return capsule (SRC), entering Earth’s atmosphere in Sep-tember 2004. The Genesis Preliminary Examination Team was able to show that, because the solar-wind ions were bur-ied beneath the surface of the collectors, it is possible to de-tect and quantify elements in the solar wind. When samples are back on Earth, sophisticated acid etching techniques de-veloped by the University of Zurich, Switzerland, were used to etch the metal layer by layer, releasing the particles of gas for laboratory study. 3.4. MGs for Solar Energy Conversion Systems MGs can be relatively simple patterned in different forms and various aspects [27, 28]. Figure 11 schematically shows how the patterned MG surfaces can be used as anti-reflective coatings in solar en-ergy converters (especially solar to thermal energy). A sig-nificant increase in efficiency is expected, given that less solar light is reflected. Fig. (11). Anti-reflective patterned MGs for solar light absorption (adapted from [27, 28] © Elsevier). Some special MGs were recently used as the layer that sits between each individual cell in solid oxide fuel cells (SOFC). 3.5. MGs Obtained from Low Purity Industrial Materials Recently, in [29], the authors obtained tungsten-based metallic glasses from low-purity industrial raw materials through a melt-spinning method. The low-purity industrial raw materials were used: ferrotungsten, ferroboron and cast iron. A full metallic glass (W 30Fe 38B 22C 10) was produced. Tungsten-based metallic glasses reported in previous papers are made up of high purity tungsten ruthenium, rhenium, iridium and boron. The high prices of pure ruthenium, rhe-nium and iridium elements limit the ability to use these in a wide range of applications. Figure 13 is presented a typical high-resolution transmis-sion electron microscopy (HRTEM) image and selected area electron diffraction (SAED) pattern for the W 30Fe 38 B 22C 10 ribbon sample. Nanocrystals are not detected and a fully amorphous structure was confirmed Fig. (12).
218 Recent Patents on Materials Science 2012, Vol. 5, No. 3 Axinte and Chirileanu
Fig. (12). High resolution TEM image and selected area electronic diffraction pattern (inset) of theW30Fe38B22C10 sample (adapted with permission from [29] © 2011 Elsevier).
The application of low-purity industrial raw materials not only reduces the cost, but also improves the manufacturabil-ity of W-b ased metallic glasses with high crystallization temperature, high modulus and high hardness.
3.6. MGs as “Green Engineering” Tools
Metallic glasses can be processed through powder metal-lurgy. This process is more flexib le in controlling the size, shape and microstructures of the components. MG powders are usually obtained by using atomization methods and me-chanical alloying. In atomization, high-purity raw materials and Ar are used, in order to decrease impurity level and in-crease glass forming ability.
In [30], the authors prepared mono-dispersed spherical particles of a desired diameter by using an atomization proc-ess that they developed. The particles have perfect sphericity and narrow size distribution along with a homogeneous com-position. The authors have successfully developed a unique atomization process which is capab le of producing mono-dispersed particles of various materials, using a method called the pulsated orifice ejection method (POEM).
The POEM is able to mass-produce mono-dispersed par-ticles of the desired diameter in the range of several tens to hundreds of micrometers. The results of structural and ther-mal analyses showed that the prepared particles exhib ited a homogeneous glassy phase. In addition, the microstructure of the particles changed from a fully crystalline phase to a fully glassy phase with a reduction in the size of the particle. The largest particles with the diameter of 390μm clearly showed the crystalline peaks. However, the peaks gradually became ambiguous as the particle size was reduced, and the particle of 291μm showed only the broad peaks. The result implied that the volume of the glassy phase increased with the reduction in particle size. Scanning electron micros-copy (SEM) images of particles with a diameter of 300μm are presented in Fig. (13). Fig. (13). SEM image of spherical particles (adapted with permis-sion from [30] © 2011 Elsevier).
Recently developed metallic glasses based on Fe-Si-B-C-
P reportedly have good glass forming ability. Fe-Si-B metal-
lic glasses are usually used as powder cores. The manufac-
turing process includes the disintegration of the ribbons and mixing with polymers and finally, consolidation. In [31], the
authors produced Fe-Si-B-C-P amorphous powders through
water atomization.
The morphology, chemical composition, phase structure
and soft magnetic properties have b een studied and the re-sults indicate that the powders are completely amorphous in nature.
The morphology of the powders can be modified by ad-
justing the water atomization parameters and spherical parti-
cles can be made Fig. (14).
The water-atomized powders can be easily processed into
compacts due to their irregular shape. The soft magnetic
properties depend on the heat treatment temperature Fig.
(15).
Fig. (14). Microstructures of the atomized Fe-b ased metallic pow-ders. (a) General view; (b) spherical particles ( adapted with permis-
sion from [31] © 2011 Elsevier ).
Industrialization of Metallic Glasses Recent Patents on Materials Science 2012, Vol. 5, No. 3 219
Fig. (15). Fe-based metallic powder rings (adapted with permission from [31] © 2011 Elsevier).
In [32], it is described how a Fe-based BMG powder (with a little Ni, Cr, Mo, B and Si) is produced using water atomization. The powder diameter extends in a wide range from ~ 0.05 to 0.6mm because of the high glass-forming ability for the developed Fe-based alloy.
BMG powder has the advantage of much longer endur-ance times compared with those for cast steel shot and high-speed steel shot. By use of good mechanical characteristics in conjunction with high corrosion resistance and a smooth outer surface, the peening shot treatment using BMG powder can generate a higher level of residual compressive stress on the surface of high class alloy steel vehicle gears with a high Vickers’ hardness comparable with hardness achieved by a carburization treatment. As a result, the alloy steel gears can increase fatigue strength by 50-80% compared with the steel gear subjected to peening shot using high-speed steel ball. This causes a significant reduction in the weight of alloy steel vehicle gear by ~45% [1, 31]. Another great advantage of BMG powders is that they are 100% recyclable (see Fig.
(16))
Fig. (16). BMG powder peening process (adapted with permission from [1] and [32] © 2011 Elsevier). 4. CURRENT & FUTURE DEVELOPMENTS
4.1. Current Developments
A novel metal-to-metal or material-to-material joining technique using bulk metallic glasses is provided in [33]. The method of the current invention relies on the superior mechanical properties of bulk metallic glasses and softening behaviour of metallic glasses in the undercooled liquid re-gion of temperature-time process space, enabling joining of a variety of materials at a lower temperature than typical ranges used for soldering, brazing or welding. Two types of joining are presented. In the first example, a thermoplastic joining process is described. This "thermoplastic joining" process is based on the unique rheological behaviour and pattern-replication ability of Bulk Metallic Glass. In a sec-ond example joining method a deep undercoating process may be used. This processing technique utilizes the deep undercoating characteristic of metallic glasses to form a liq-uid joining material that can be used to create joints that can be amorphous, crystalline or partially crystalline.
In patent [34], the authors present a family of iron-based, bulk metallic glasses containing phosphorus, with excellent processibility and toughness, methods for forming such al-loys, and processes for manufacturing articles. The inventive iron-based alloy is based on the observation that by very tightly controlling the composition of the metalloid moiety of the Fe-based phosphorous bulk metallic glass alloys, it is possible to obtain highly processable alloys with low shear toughness. The invented alloy demonstrates an optimum toughness-glass forming ability relationship. It also demon-strates higher toughness for a given critical rod diameter than any other prior art alloys. This optimum relationship, which is unique to Fe-based systems, is a consequence of a low shear modulus achieved by very tightly controlling the frac-tions of C and B in the compositions of the inventive alloys.
In [35], a new method is provided for obtaining a her-metic seal using an amorphous alloy or composite containing an amorphous alloy where the manufacturing process takes place at a temperature around the glass transition tempera-ture or within the supercooled liquid region.
Reference [36] provides a new method for producing wire by combining a metal strip and a powder. This inven-tion includes a method of obtaining a hardened surface on a substrate by processing a solid mass to form a powder. This powder is applied to a surface to form a layer containing metallic glass and converting the glass into a material with a nanocrystalline microstructure.
Recently, light-weight and low-cost Magnesium (Mg)-based metallic glasses have been researched. New alloys with surprising properties have been developed.
In [37], it is revealed how, through the addition of the Zn element, Mg-Li-Cu-Zn-(Y, Gd) bulk metallic glasses with a diameter of 2mm have been successfully manufactured using the conventional copper mould injection casting method.
In [38], the authors demonstrate that by increasing Li content (3 at.%-8 at.%), the supercooled liquid region tem-perature of Mg-based metallic glasses gradually decreases. It
was also shown that the addition of metal Li effectively in-。