# Patent

## Title
BMG parts having greater than critical casting thickness and method for making the same

## Abstract

The embodiments described herein relate to BMG articles with high bulk having all dimensions greater than the critical dimension. Exemplary BMG article can include at least one bulk component and/or one or more fixation elements configured on surface of the bulk component or inserted into the bulk component. Other embodiments relate to methods of making the BMG articles by thermo-plastic-formation of BMG alloy materials.

## Background
BACKGROUND
A large portion of the metallic alloys in use today are processed by solidification casting, at least initially. The metallic alloy is melted and cast into a metal or ceramic mold, where it solidifies. The mold is stripped away, and the cast metallic piece is ready for use or further processing. The as-cast structure of most materials produced during solidification and cooling depends upon the cooling rate. There is no general rule for the nature of the variation, but for the most part the structure changes only gradually with changes in cooling rate. On the other hand, for the bulk-solidifying amorphous alloys the change between the amorphous state produced by relatively rapid cooling and the crystalline state produced by relatively slower cooling is one of kind rather than degree—the two states have distinct properties.
Bulk-solidifying amorphous alloys, or bulk metallic glasses (“BMG”), are a recently developed class of metallic materials. These alloys may be solidified and cooled at relatively slow rates, and they retain the amorphous, non-crystalline (i.e., glassy) state at room temperature. This amorphous state can be highly advantageous for certain applications. If the cooling rate is not sufficiently high, crystals may form inside the alloy during cooling, so that the benefits of the amorphous state are partially or completely lost. For example, one risk with the creation of bulk amorphous alloy parts is partial crystallization due to either slow cooling or impurities in the raw material.
Bulk-solidifying amorphous alloys have been made in a variety of metallic systems. They are generally prepared by quenching from above the melting temperature to the ambient temperature. Generally, high cooling rates, such as one on the order of 105° C./sec, are needed to achieve an amorphous structure. The lowest rate by which a bulk solidifying alloy can be cooled to avoid crystallization, thereby achieving and maintaining the amorphous structure during cooling, is referred to as the “critical cooling rate” for the alloy. In order to achieve a cooling rate higher than the critical cooling rate, heat has to be extracted from the sample. Thus, the thickness of articles made from amorphous alloys often becomes a limiting dimension, which is generally referred to as the “critical (casting) thickness.” A critical thickness of an amorphous alloy can be obtained by heat-flow calculations, taking into account the critical cooling rate.
Until the early nineties, the processability of amorphous alloys was quite limited, and amorphous alloys were readily available only in powder form or in very thin foils or strips with a critical thickness of less than 100 micrometers. A class of amorphous alloys based mostly on Zr and Ti alloy systems was developed in the nineties, and since then more amorphous alloy systems based on different elements have been developed. These families of alloys have much lower critical cooling rates of less than 103° C./sec, and thus they have much larger critical casting thicknesses than their previous counterparts. However, little has been shown regarding how to utilize and/or shape these alloy systems into structural components, such as those in consumer electronic devices. In particular, pre-existing forming or processing methods often result in high product cost when it comes to high aspect ratio products (e.g., thin sheets) or three-dimensional hollow products. Moreover, the pre-existing methods can often suffer the drawbacks of producing products that lose many of the desirable mechanical properties as observed in an amorphous alloy. Furthermore, the pre-existing methods such as conventional casting techniques are limited by the critical casting thickness of the amorphous alloy.
Thus, there is a need to provide BMG parts having greater than critical dimension and methods for making the same.
SUMMARY
The embodiments described herein relate to BMG parts with high bulk and methods of making them. The embodiments described herein further relate to articles such as electronic devices that include the disclosed BMG parts. The electronic devices can include, without limitation, a telephone, a smart phone such as an iPhoneTM; a display such as a digital display, a TV monitor, an electronic-book reader, a portable web-browser (e.g., iPadTM), and a computer monitor; an entertainment device such as a portable DVD player, conventional DVD player, Blue-Ray disk player, video game console, music player; and any other possible electronic devices as disclosed herein.
In accordance with various embodiments, there is provided a BMG article processed to have greater than critical dimensions. An exemplary BMG article can be formed of a material including one or more BMG alloys with all dimensions greater than a critical dimension of each BMG alloy used. Such BMG article can include at least one bulk component and/or one or more fixation elements configured on surface of the bulk component or inserted in the bulk component.
In accordance with various embodiments, there is provided a method of making a bulk metallic glass (BMG) part. In this method, a part in a first form formed of one or more BMG alloys can be provided having at least one dimension less than or equal to a critical dimension of each BMG alloy used. The part in the first form can then be heated to at least above the glass transition temperature of each BMG alloy and further be plastically formed into a second form. The part in the second form can have all dimensions greater than the critical dimension. The heating and plastically forming processes can be conducted simultaneously or sequentially. In one embodiment, the part in the first form can have a near net shape and the part in the second form can have the net shape by the thermo-plastic-formation.
In accordance with various embodiments, there is provided a method of making a bulk metallic glass (BMG) part. In this method, a part in a first form can be formed of one or more BMG alloys and can have one or more dimensions less than or equal to a critical dimension of each BMG alloy used. The part in the first form can then be heated to at least above the glass transition temperature of each BMG alloy and further be shaped into a second form such that all dimensions thereof are greater than the critical dimension. The heating and shaping processes can be conducted simultaneously or sequentially. In embodiments, a mold with a pre-determined shape/dimension can be used for shaping or re-shaping the BMG article.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 provides a temperature-viscosity diagram of an exemplary bulk solidifying amorphous alloy.
FIG. 2 provides a schematic of a time-temperature-transformation (TTT) diagram for an exemplary bulk solidifying amorphous alloy.
FIGS. 3A-3D illustrate an exemplary BMG article at various fabrication stages in accordance with various embodiments of the present invention.



DETAILED DESCRIPTION
All publications, patents, and patent applications cited in this Specification are hereby incorporated by reference in their entirety.
The articles “a” and “an” are used herein to refer to one or to more than one (i.e., to at least one) of the grammatical object of the article. By way of example, “a polymer resin” means one polymer resin or more than one polymer resin. Any ranges cited herein are inclusive. The terms “substantially” and “about” used throughout this Specification are used to describe and account for small fluctuations. For example, they can refer to less than or equal to ±5%, such as less than or equal to ±2%, such as less than or equal to ±1%, such as less than or equal to ±0.5%, such as less than or equal to ±0.2%, such as less than or equal to ±0.1%, such as less than or equal to ±0.05%.
Bulk-solidifying amorphous alloys, or bulk metallic glasses (“BMG”), are a recently developed class of metallic materials. These alloys may be solidified and cooled at relatively slow rates, and they retain the amorphous, non-crystalline (i.e., glassy) state at room temperature. Amorphous alloys have many superior properties than their crystalline counterparts. However, if the cooling rate is not sufficiently high, crystals may form inside the alloy during cooling, so that the benefits of the amorphous state can be lost. For example, one challenge with the fabrication of bulk amorphous alloy parts is partial crystallization of the parts due to either slow cooling or impurities in the raw alloy material. As a high degree of amorphicity (and, conversely, a low degree of crystallinity) is desirable in BMG parts, there is a need to develop methods for casting BMG parts having controlled amount of amorphicity.
FIG. 1 shows a viscosity-temperature graph of an exemplary bulk solidifying amorphous alloy, from the VIT-001 series of Zr—Ti—Ni—Cu—Be family manufactured by Liquidmetal Technology. It should be noted that there is no clear liquid/solid transformation for a bulk solidifying amorphous metal during the formation of an amorphous solid. The molten alloy becomes more and more viscous with increasing undercooling until it approaches solid form around the glass transition temperature. Accordingly, the temperature of solidification front for bulk solidifying amorphous alloys can be around glass transition temperature, where the alloy will practically act as a solid for the purposes of pulling out the quenched amorphous sheet product.
FIG. 2 (obtained from U.S. Pat. No. 7,575,040) shows the time-temperature-transformation (TTT) cooling curve of an exemplary bulk solidifying amorphous alloy, or TTT diagram. Bulk-solidifying amorphous metals do not experience a liquid/solid crystallization transformation upon cooling, as with conventional metals. Instead, the highly fluid, non crystalline form of the metal found at high temperatures (near a “melting temperature” Tm) becomes more viscous as the temperature is reduced (near to the glass transition temperature Tg), eventually taking on the outward physical properties of a conventional solid.
Even though there is no liquid/crystallization transformation for a bulk solidifying amorphous metal, a “melting temperature” Tm may be defined as the thermodynamic liquidus temperature of the corresponding crystalline phase. Under this regime, the viscosity of bulk-solidifying amorphous alloys at the melting temperature could lie in the range of about 0.1 poise to about 10,000 poise, and even sometimes under 0.01 poise. A lower viscosity at the “melting temperature” would provide faster and complete filling of intricate portions of the shell/mold with a bulk solidifying amorphous metal for forming the BMG parts. Furthermore, the cooling rate of the molten metal to form a BMG part has to such that the time-temperature profile during cooling does not traverse through the nose-shaped region bounding the crystallized region in the TTT diagram of FIG. 2. In FIG. 2, Tnose is the critical crystallization temperature Tx where crystallization is most rapid and occurs in the shortest time scale.
The supercooled liquid region, the temperature region between Tg and Tx is a manifestation of the extraordinary stability against crystallization of bulk solidification alloys. In this temperature region the bulk solidifying alloy can exist as a high viscous liquid. The viscosity of the bulk solidifying alloy in the supercooled liquid region can vary between 1012 Pa s at the glass transition temperature down to 105 Pa s at the crystallization temperature, the high temperature limit of the supercooled liquid region. Liquids with such viscosities can undergo substantial plastic strain under an applied pressure. The embodiments herein make use of the large plastic formability in the supercooled liquid region as a forming and separating method.
One needs to clarify something about Tx. Technically, the nose-shaped curve shown in the TTT diagram describes Tx as a function of temperature and time. Thus, regardless of the trajectory that one takes while heating or cooling a metal alloy, when one hits the TTT curve, one has reached Tx. In FIG. 2, Tx is shown as a dashed line as Tx can vary from close to Tm to close to Tg.
The schematic TTT diagram of FIG. 2 shows processing methods of die casting from at or above Tm to below Tg without the time-temperature trajectory (shown as (1) as an example trajectory) hitting the TTT curve. During die casting, the forming takes place substeantially simultaneously with fast cooling to avoid the trajectory hitting the TTT curve. The procssing methods for superplastic forming (SPF) from at or below Tg to below Tm without the time-temperature trajectory (shown as (2), (3) and (4) as example trajectories) hitting the TTT curve. In SPF, the amorphous BMG is reheated into the supercooled liquid region where the available processing window could be much larger than die casting, resulting in better controllability of the process. The SPF process does not require fast cooling to avoid crystallization during cooling. Also, as shown by example trajectories (2), (3) and (4), the SPF can be carried out with the highest temperature during SPF being above Tnose or below Tnose, up to about Tm. If one heats up a piece of amorphous alloy but manages to avoid hitting the TTT curve, you have heated “between Tg and Tm”, but one would have not reached Tx.
Typical differential scanning calorimeter (DSC) heating curves of bulk-solidifying amorphous alloys taken at a heating rate of 20 C/min describe, for the most part, a particular trajectory across the TTT data where one would likely see a Tg at a certain temperature, a Tx when the DSC heating ramp crosses the TTT crystallization onset, and eventually melting peaks when the same trajectory crosses the temperature range for melting. If one heats a bulk-solidifying amorphous alloy at a rapid heating rate as shown by the ramp up portion of trajectories (2), (3) and (4) in FIG. 2, then one could avoid the TTT curve entirely, and the DSC data would show a glass transition but no Tx upon heating. Another way to think about it is trajectories (2), (3) and (4) can fall anywhere in temperature between the nose of the TTT curve (and even above it) and the Tg line, as long as it does not hit the crystallization curve. That just means that the horizontal plateau in trajectories might get much shorter as one increases the processing temperature.
Phase
The term “phase” herein can refer to one that can be found in a thermodynamic phase diagram. A phase is a region of space (e.g., a thermodynamic system) throughout which all physical properties of a material are essentially uniform. Examples of physical properties include density, index of refraction, chemical composition and lattice periodicity. A simple description of a phase is a region of material that is chemically uniform, physically distinct, and/or mechanically separable. For example, in a system consisting of ice and water in a glass jar, the ice cubes are one phase, the water is a second phase, and the humid air over the water is a third phase. The glass of the jar is another separate phase. A phase can refer to a solid solution, which can be a binary, tertiary, quaternary, or more, solution, or a compound, such as an intermetallic compound. As another example, an amorphous phase is distinct from a crystalline phase.
Metal, Transition Metal, and Non-metal
The term “metal” refers to an electropositive chemical element. The term “element” in this Specification refers generally to an element that can be found in a Periodic Table. Physically, a metal atom in the ground state contains a partially filled band with an empty state close to an occupied state. The term “transition metal” is any of the metallic elements within Groups 3 to 12 in the Periodic Table that have an incomplete inner electron shell and that serve as transitional links between the most and the least electropositive in a series of elements. Transition metals are characterized by multiple valences, colored compounds, and the ability to form stable complex ions. The term “nonmetal” refers to a chemical element that does not have the capacity to lose electrons and form a positive ion.
Depending on the application, any suitable nonmetal elements, or their combinations, can be used. The alloy (or “alloy composition”) can comprise multiple nonmetal elements, such as at least two, at least three, at least four, or more, nonmetal elements. A nonmetal element can be any element that is found in Groups 13-17 in the Periodic Table. For example, a nonmetal element can be any one of F, CI, Br, I, At, 0, S, Se, Te, Po, N, P, As, Sb, Bi, C, Si, Ge, Sn, Pb, and B. Occasionally, a nonmetal element can also refer to certain metalloids (e.g., B, Si, Ge, As, Sb, Te, and Po) in Groups 13-17. In one embodiment, the nonmetal elements can include B, Si, C, P, or combinations thereof. Accordingly, for example, the alloy can comprise a boride, a carbide, or both.
A transition metal element can be any of scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, yttrium, zirconium, niobium, molybdenum, technetium, ruthenium, rhodium, palladium, silver, cadmium, hafnium, tantalum, tungsten, rhenium, osmium, iridium, platinum, gold, mercury, rutherfordium, dubnium, seaborgium, bohrium, hassium, meitnerium, ununnilium, unununium, and ununbium. In one embodiment, a BMG containing a transition metal element can have at least one of Sc, Y, La, Ac, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Tc, Re, Fe, Ru, Os, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zn, Cd, and Hg. Depending on the application, any suitable transitional metal elements, or their combinations, can be used. The alloy composition can comprise multiple transitional metal elements, such as at least two, at least three, at least four, or more, transitional metal elements.
The presently described alloy or alloy “sample” or “specimen” alloy can have any shape or size. For example, the alloy can have a shape of a particulate, which can have a shape such as spherical, ellipsoid, wire-like, rod-like, sheet-like, flake-like, or an irregular shape. The particulate can have any size. For example, it can have an average diameter of between about 1 micron and about 100 microns, such as between about 5 microns and about 80 microns, such as between about 10 microns and about 60 microns, such as between about 15 microns and about 50 microns, such as between about 15 microns and about 45 microns, such as between about 20 microns and about 40 microns, such as between about 25 microns and about 35 microns. For example, in one embodiment, the average diameter of the particulate is between about 25 microns and about 44 microns. In some embodiments, smaller particulates, such as those in the nanometer range, or larger particulates, such as those bigger than 100 microns, can be used.
The alloy sample or specimen can also be of a much larger dimension. For example, it can be a bulk structural component, such as an ingot, housing/casing of an electronic device or even a portion of a structural component that has dimensions in the millimeter, centimeter, or meter range.
Solid Solution
The term “solid solution” refers to a solid form of a solution. The term “solution” refers to a mixture of two or more substances, which may be solids, liquids, gases, or a combination of these. The mixture can be homogeneous or heterogeneous. The term “mixture” is a composition of two or more substances that are combined with each other and are generally capable of being separated. Generally, the two or more substances are not chemically combined with each other.
Alloy
In some embodiments, the alloy composition described herein can be fully alloyed. In one embodiment, an “alloy” refers to a homogeneous mixture or solid solution of two or more metals, the atoms of one replacing or occupying interstitial positions between the atoms of the other; for example, brass is an alloy of zinc and copper. An alloy, in contrast to a composite, can refer to a partial or complete solid solution of one or more elements in a metal matrix, such as one or more compounds in a metallic matrix. The term alloy herein can refer to both a complete solid solution alloy that can give single solid phase microstructure and a partial solution that can give two or more phases. An alloy composition described herein can refer to one comprising an alloy or one comprising an alloy-containing composite.
Thus, a fully alloyed alloy can have a homogenous distribution of the constituents, be it a solid solution phase, a compound phase, or both. The term “fully alloyed” used herein can account for minor variations within the error tolerance. For example, it can refer to at least 90% alloyed, such as at least 95% alloyed, such as at least 99% alloyed, such as at least 99.5% alloyed, such as at least 99.9% alloyed. The percentage herein can refer to either volume percent or weight percentage, depending on the context. These percentages can be balanced by impurities, which can be in terms of composition or phases that are not a part of the alloy.
Amorphous or Non-crystalline Solid
An “amorphous” or “non-crystalline solid” is a solid that lacks lattice periodicity, which is characteristic of a crystal. As used herein, an “amorphous solid” includes “glass” which is an amorphous solid that softens and transforms into a liquid-like state upon heating through the glass transition. Generally, amorphous materials lack the long-range order characteristic of a crystal, though they can possess some short-range order at the atomic length scale due to the nature of chemical bonding. The distinction between amorphous solids and crystalline solids can be made based on lattice periodicity as determined by structural characterization techniques such as x-ray diffraction and transmission electron microscopy.
The terms “order” and “disorder” designate the presence or absence of some symmetry or correlation in a many-particle system. The terms “long-range order” and “short-range order” distinguish order in materials based on length scales.
The strictest form of order in a solid is lattice periodicity: a certain pattern (the arrangement of atoms in a unit cell) is repeated again and again to form a translationally invariant tiling of space. This is the defining property of a crystal. Possible symmetries have been classified in 14 Bravais lattices and 230 space groups.
Lattice periodicity implies long-range order. If only one unit cell is known, then by virtue of the translational symmetry it is possible to accurately predict all atomic positions at arbitrary distances. The converse is generally true, except, for example, in quasi-crystals that have perfectly deterministic tilings but do not possess lattice periodicity.
Long-range order characterizes physical systems in which remote portions of the same sample exhibit correlated behavior. This can be expressed as a correlation function, namely the spin-spin correlation function: G(x,x′)=s(x),s(x′).
In the above function, s is the spin quantum number and x is the distance function within the particular system. This function is equal to unity when x=x′ and decreases as the distance |x−x′| increases. Typically, it decays exponentially to zero at large distances, and the system is considered to be disordered. If, however, the correlation function decays to a constant value at large |x−x′|, then the system can be said to possess long-range order. If it decays to zero as a power of the distance, then it can be called quasi-long-range order. Note that what constitutes a large value of |x−x′| is relative.
A system can be said to present quenched disorder when some parameters defining its behavior are random variables that do not evolve with time (i.e., they are quenched or frozen)—e.g., spin glasses. It is opposite to annealed disorder, where the random variables are allowed to evolve themselves. Embodiments herein include systems comprising quenched disorder.
The alloy described herein can be crystalline, partially crystalline, amorphous, or substantially amorphous. For example, the alloy sample/specimen can include at least some crystallinity, with grains/crystals having sizes in the nanometer and/or micrometer ranges. Alternatively, the alloy can be substantially amorphous, such as fully amorphous. In one embodiment, the alloy composition is at least substantially not amorphous, such as being substantially crystalline, such as being entirely crystalline.
In one embodiment, the presence of a crystal or a plurality of crystals in an otherwise amorphous alloy can be construed as a “crystalline phase” therein. The degree of crystallinity (or “crystallinity” for short in some embodiments) of an alloy can refer to the amount of the crystalline phase present in the alloy. The degree can refer to, for example, a fraction of crystals present in the alloy. The fraction can refer to volume fraction or weight fraction, depending on the context. A measure of how “amorphous” an amorphous alloy is can be amorphicity. Amorphicity can be measured in terms of a degree of crystallinity. For example, in one embodiment, an alloy having a low degree of crystallinity can be said to have a high degree of amorphicity. In one embodiment, for example, an alloy having 60 vol % crystalline phase can have a 40 vol % amorphous phase.
Amorphous Alloy or Amorphous Metal
An “amorphous alloy” is an alloy having an amorphous content of more than 50% by volume, preferably more than 90% by volume of amorphous content, more preferably more than 95% by volume of amorphous content, and most preferably more than 99% to almost 100% by volume of amorphous content. Note that, as described above, an alloy high in amorphicity is equivalently low in degree of crystallinity. An “amorphous metal” is an amorphous metal material with a disordered atomic-scale structure. In contrast to most metals, which are crystalline and therefore have a highly ordered arrangement of atoms, amorphous alloys are non-crystalline. Materials in which such a disordered structure is produced directly from the liquid state during cooling are sometimes referred to as “glasses.” Accordingly, amorphous metals are commonly referred to as “metallic glasses” or “glassy metals.” In one embodiment, a bulk metallic glass (“BMG”) can refer to an alloy, of which the microstructure is at least partially amorphous. However, there are several ways besides extremely rapid cooling to produce amorphous metals, including physical vapor deposition, solid-state reaction, ion irradiation, melt spinning, and mechanical alloying. Amorphous alloys can be a single class of materials, regardless of how they are prepared.
Amorphous metals can be produced through a variety of quick-cooling methods. For instance, amorphous metals can be produced by sputtering molten metal onto a spinning metal disk. The rapid cooling, on the order of millions of degrees a second, can be too fast for crystals to form, and the material is thus “locked in” a glassy state. Also, amorphous metals/alloys can be produced with critical cooling rates low enough to allow formation of amorphous structures in thick layers—e.g., bulk metallic glasses.
The terms “bulk metallic glass” (“BMG”), bulk amorphous alloy (“BAA”), and bulk solidifying amorphous alloy are used interchangeably herein. They refer to amorphous alloys having the smallest dimension at least in the millimeter range. For example, the dimension can be at least about 0.5 mm, such as at least about 1 mm, such as at least about 2 mm, such as at least about 4 mm, such as at least about 5 mm, such as at least about 6 mm, such as at least about 8 mm, such as at least about 10 mm, such as at least about 12 mm. Depending on the geometry, the dimension can refer to the diameter, radius, thickness, width, length, etc. A BMG can also be a metallic glass having at least one dimension in the centimeter range, such as at least about 1.0 cm, such as at least about 2.0 cm, such as at least about 5.0 cm, such as at least about 10.0 cm. In some embodiments, a BMG can have at least one dimension at least in the meter range. A BMG can take any of the shapes or forms described above, as related to a metallic glass. Accordingly, a BMG described herein in some embodiments can be different from a thin film made by a conventional deposition technique in one important aspect—the former can be of a much larger dimension than the latter.
Amorphous metals can be an alloy rather than a pure metal. The alloys may contain atoms of significantly different sizes, leading to low free volume (and therefore having viscosity up to orders of magnitude higher than other metals and alloys) in a molten state. The viscosity prevents the atoms from moving enough to form an ordered lattice. The material structure may result in low shrinkage during cooling and resistance to plastic deformation. The absence of grain boundaries, the weak spots of crystalline materials in some cases, may, for example, lead to better resistance to wear and corrosion. In one embodiment, amorphous metals, while technically glasses, may also be much tougher and less brittle than oxide glasses and ceramics.
Thermal conductivity of amorphous materials may be lower than that of their crystalline counterparts. To achieve formation of an amorphous structure even during slower cooling, the alloy may be made of three or more components, leading to complex crystal units with higher potential energy and lower probability of formation. The formation of amorphous alloy can depend on several factors: the composition of the components of the alloy; the atomic radius of the components (preferably with a significant difference of over 12% to achieve high packing density and low free volume); and the negative heat of mixing the combination of components, inhibiting crystal nucleation and prolonging the time the molten metal stays in a supercooled state. However, as the formation of an amorphous alloy is based on many different variables, it can be difficult to make a prior determination of whether an alloy composition would form an amorphous alloy.
Amorphous alloys, for example, of boron, silicon, phosphorus, and other glass formers with magnetic metals (iron, cobalt, nickel) may be magnetic, with low coercivity and high electrical resistance. The high resistance leads to low losses by eddy currents when subjected to alternating magnetic fields, a property useful, for example, as transformer magnetic cores.
Amorphous alloys may have a variety of potentially useful properties. In particular, they tend to be stronger than crystalline alloys of similar chemical composition, and they can sustain larger reversible (“elastic”) deformations than crystalline alloys. Amorphous metals derive their strength directly from their non-crystalline structure, which can have none of the defects (such as dislocations) that limit the strength of crystalline alloys. For example, one modern amorphous metal, known as VitreloyTM, has a tensile strength that is almost twice that of high-grade titanium. In some embodiments, metallic glasses at room temperature are not ductile and tend to fail suddenly when loaded in tension, which limits the material applicability in reliability-critical applications, as the impending failure is not evident. Therefore, to overcome this challenge, metal matrix composite materials having a metallic glass matrix containing dendritic particles or fibers of a ductile crystalline metal can be used. Alternatively, a BMG low in element(s) that tend to cause embitterment (e.g., Ni) can be used. For example, a Ni-free BMG can be used to improve the ductility of the BMG.
Another useful property of bulk amorphous alloys is that they can be true glasses; in other words, they can soften and flow upon heating. This can allow for easy processing, such as by injection molding, in much the same way as polymers. As a result, amorphous alloys can be used for making sports equipment, medical devices, electronic components and equipment, and thin films. Thin films of amorphous metals can be deposited as protective coatings via a high velocity oxygen fuel technique.
A material can have an amorphous phase, a crystalline phase, or both. The amorphous and crystalline phases can have the same chemical composition and differ only in the microstructure—i.e., one amorphous and the other crystalline. Microstructure in one embodiment refers to the structure of a material as revealed by a microscope at 25× magnification or higher. Alternatively, the two phases can have different chemical compositions and microstructures. For example, a composition can be partially amorphous, substantially amorphous, or completely amorphous.
As described above, the degree of amorphicity (and conversely the degree of crystallinity) can be measured by fraction of crystals present in the alloy. The degree can refer to volume fraction of weight fraction of the crystalline phase present in the alloy. A partially amorphous composition can refer to a composition of at least about 5 vol % of which is of an amorphous phase, such as at least about 10 vol %, such as at least about 20 vol %, such as at least about 40 vol %, such as at least about 60 vol %, such as at least about 80 vol %, such as at least about 90 vol %. The terms “substantially” and “about” have been defined elsewhere in this application. Accordingly, a composition that is at least substantially amorphous can refer to one of which at least about 90 vol % is amorphous, such as at least about 95 vol %, such as at least about 98 vol %, such as at least about 99 vol %, such as at least about 99.5 vol %, such as at least about 99.8 vol %, such as at least about 99.9 vol %. In one embodiment, a substantially amorphous composition can have some incidental, insignificant amount of crystalline phase present therein.
In one embodiment, an amorphous alloy composition can be homogeneous with respect to the amorphous phase. A substance that is uniform in composition is homogeneous. This is in contrast to a substance that is heterogeneous. The term “composition” refers to the chemical composition and/or microstructure in the substance. A substance is homogeneous when a volume of the substance is divided in half and both halves have substantially the same composition. For example, a particulate suspension is homogeneous when a volume of the particulate suspension is divided in half and both halves have substantially the same volume of particles. However, it might be possible to see the individual particles under a microscope. Another example of a homogeneous substance is air where different ingredients therein are equally suspended, though the particles, gases and liquids in air can be analyzed separately or separated from air.
A composition that is homogeneous with respect to an amorphous alloy can refer to one having an amorphous phase substantially uniformly distributed throughout its microstructure. In other words, the composition macroscopically comprises a substantially uniformly distributed amorphous alloy throughout the composition. In an alternative embodiment, the composition can be of a composite, having an amorphous phase having therein a non-amorphous phase. The non-amorphous phase can be a crystal or a plurality of crystals. The crystals can be in the form of particulates of any shape, such as spherical, ellipsoid, wire-like, rod-like, sheet-like, flake-like, or an irregular shape. In one embodiment, it can have a dendritic form. For example, an at least partially amorphous composite composition can have a crystalline phase in the shape of dendrites dispersed in an amorphous phase matrix; the dispersion can be uniform or non-uniform, and the amorphous phase and the crystalline phase can have the same or a different chemical composition. In one embodiment, they have substantially the same chemical composition. In another embodiment, the crystalline phase can be more ductile than the BMG phase.
The methods described herein can be applicable to any type of amorphous alloy. Similarly, the amorphous alloy described herein as a constituent of a composition or article can be of any type. The amorphous alloy can comprise the element Zr, Hf, Ti, Cu, Ni, Pt, Pd, Fe, Mg, Au, La, Ag, Al, Mo, Nb, Be, or combinations thereof. Namely, the alloy can include any combination of these elements in its chemical formula or chemical composition. The elements can be present at different weight or volume percentages. For example, an iron “based” alloy can refer to an alloy having a non-insignificant weight percentage of iron present therein, the weight percent can be, for example, at least about 20 wt %, such as at least about 40 wt %, such as at least about 50 wt %, such as at least about 60 wt %, such as at least about 80 wt %. Alternatively, in one embodiment, the above-described percentages can be volume percentages, instead of weight percentages. Accordingly, an amorphous alloy can be zirconium-based, titanium-based, platinum-based, palladium-based, gold-based, silver-based, copper-based, iron-based, nickel-based, aluminum-based, molybdenum-based, and the like. The alloy can also be free of any of the aforementioned elements to suit a particular purpose. For example, in some embodiments, the alloy, or the composition including the alloy, can be substantially free of nickel, aluminum, titanium, beryllium, or combinations thereof. In one embodiment, the alloy or the composite is completely free of nickel, aluminum, titanium, beryllium, or combinations thereof.
For example, the amorphous alloy can have the formula (Zr, Ti)a(Ni, Cu, Fe)b(Be, Al, Si, B)c, wherein a, b, and c each represents a weight or atomic percentage. In one embodiment, a is in the range of from 30 to 75, b is in the range of from 5 to 60, and c is in the range of from 0 to 50 in atomic percentages. Alternatively, the amorphous alloy can have the formula (Zr, Ti)a(Ni, Cu)b(Be)c, wherein a, b, and c each represents a weight or atomic percentage. In one embodiment, a is in the range of from 40 to 75, b is in the range of from 5 to 50, and c is in the range of from 5 to 50 in atomic percentages. The alloy can also have the formula (Zr, Ti)a(Ni, Cu)b(Be)c, wherein a, b, and c each represents a weight or atomic percentage. In one embodiment, a is in the range of from 45 to 65, b is in the range of from 7.5 to 35, and c is in the range of from 10 to 37.5 in atomic percentages. Alternatively, the alloy can have the formula (Zr)a(Nb, Ti)b(Ni, Cu)c(Al)d, wherein a, b, c, and d each represents a weight or atomic percentage. In one embodiment, a is in the range of from 45 to 65, b is in the range of from 0 to 10, c is in the range of from 20 to 40 and d is in the range of from 7.5 to 15 in atomic percentages. One exemplary embodiment of the afore described alloy system is a Zr—Ti—Ni—Cu—Be based amorphous alloy under the trade name VitreloyTM, such as Vitreloy-1 and Vitreloy-101, as fabricated by Liquidmetal Technologies, CA, USA. Some examples of amorphous alloys of the different systems are provided in Table 1.
The amorphous alloys can also be ferrous alloys, such as (Fe, Ni, Co) based alloys. Examples of such compositions are disclosed in U.S. Pat. Nos. 6,325,868; 5,288,344; 5,368,659; 5,618,359; and 5,735,975, Inoue et al., Appl. Phys. Lett., Volume 71, p 464 (1997), Shen et al., Mater. Trans., JIM, Volume 42, p 2136 (2001), and Japanese Patent Application No. 200126277 (Pub. No. 2001303218 A). One exemplary composition is Fe72Al5Ga2PIIC6B4. Another example is Fe72Al7ZrI0Mo5W2B15. Another iron-based alloy system that can be used in the coating herein is disclosed in U.S. Patent Application Publication No. 2010/0084052, wherein the amorphous metal contains, for example, manganese (1 to 3 atomic %), yttrium (0.1 to 10 atomic %), and silicon (0.3 to 3.1 atomic %) in the range of composition given in parentheses; and that contains the following elements in the specified range of composition given in parentheses: chromium (15 to 20 atomic %), molybdenum (2 to 15 atomic %), tungsten (1 to 3 atomic %), boron (5 to 16 atomic %), carbon (3 to 16 atomic %), and the balance iron.
The aforedescribed amorphous alloy systems can further include additional elements, such as additional transition metal elements, including Nb, Cr, V, and Co. The additional elements can be present at less than or equal to about 30 wt %, such as less than or equal to about 20 wt %, such as less than or equal to about 10 wt %, such as less than or equal to about 5 wt %. In one embodiment, the additional, optional element is at least one of cobalt, manganese, zirconium, tantalum, niobium, tungsten, yttrium, titanium, vanadium and hafnium to form carbides and further improve wear and corrosion resistance. Further optional elements may include phosphorous, germanium and arsenic, totaling up to about 2%, and preferably less than 1%, to reduce melting point. Otherwise incidental impurities should be less than about 2% and preferably 0.5%.







TABLE 1







Exemplary amorphous alloy compositions













Alloy
Atm %
Atm %
Atm %
Atm %
Atm %
Atm %
















1
Zr
Ti
Cu
Ni
Be




41.20%
13.80%
12.50% 
10.00%
22.50%


2
Zr
Ti
Cu
Ni
Be



44.00%
11.00%
10.00% 
10.00%
25.00%


3
Zr
Ti
Cu
Ni
Nb
Be



56.25%
11.25%
6.88%
 5.63%
 7.50%
12.50%


4
Zr
Ti
Cu
Ni
Al
Be



64.75%
 5.60%
14.90% 
11.15%
 2.60%
 1.00%


5
Zr
Ti
Cu
Ni
Al



52.50%
 5.00%
17.90% 
14.60%
10.00%


6
Zr
Nb
Cu
Ni
Al



57.00%
 5.00%
15.40% 
12.60%
10.00%


7
Zr
Cu
Ni
Al
Sn



50.75%
36.23%
4.03%
 9.00%
 0.50%


8
Zr
Ti
Cu
Ni
Be



46.75%
 8.25%
7.50%
10.00%
27.50%


9
Zr
Ti
Ni
Be



21.67%
43.33%
7.50%
27.50%


10
Zr
Ti
Cu
Be



35.00%
30.00%
7.50%
27.50%


11
Zr
Ti
Co
Be



35.00%
30.00%
6.00%
29.00%


12
Au
Ag
Pd
Cu
Si



49.00%
 5.50%
2.30%
26.90%
16.30%


13
Au
Ag
Pd
Cu
Si



50.90%
 3.00%
2.30%
27.80%
16.00%


14
Pt
Cu
Ni
P



57.50%
14.70%
5.30%
22.50%


15
Zr
Ti
Nb
Cu
Be



36.60%
31.40%
7.00%
 5.90%
19.10%


16
Zr
Ti
Nb
Cu
Be



38.30%
32.90%
7.30%
 6.20%
15.30%


17
Zr
Ti
Nb
Cu
Be



39.60%
33.90%
7.60%
 6.40%
12.50%


18
Cu
Ti
Zr
Ni



47.00%
34.00%
11.00% 
 8.00%


19
Zr
Co
Al



55.00%
25.00%
20.00% 









Other exemplary ferrous metal-based alloys include compositions such as those disclosed in U.S. Patent Application Publication Nos. 2007/0079907 and 2008/0118387. These compositions include the Fe(Mn, Co, Ni, Cu) (C, Si, B, P, Al) system, wherein the Fe content is from 60 to 75 atomic percentage, the total of (Mn, Co, Ni, Cu) is in the range of from 5 to 25 atomic percentage, and the total of (C, Si, B, P, Al) is in the range of from 8 to 20 atomic percentage, as well as the exemplary composition Fe48Cr15Mo14Y2C15B6. They also include the alloy systems described by Fe—Cr—Mo—(Y,Ln)-C—B, Co—Cr—Mo-Ln-C—B, Fe—Mn—Cr—Mo—(Y,Ln)-C—B,(Fe, Cr, Co)—(Mo,Mn)—(C,B)—Y, Fe—(Co,Ni)—(Zr,Nb,Ta)—(Mo,W)—B, Fe—(Al,Ga)—(P,C,B,Si,Ge), Fe—(Co,Cr,Mo,Ga,Sb)—P—B—C, (Fe, Co)—B—Si—Nb alloys, and Fe—(Cr—Mo)—(C,B)—Tm, where Ln denotes a lanthanide element and Tm denotes a transition metal element. Furthermore, the amorphous alloy can also be one of the exemplary compositions Fe80P12.5C5B2.5, Fe80P11C5B2.5Si1.5, Fe74.5Mo5.5P12.5C5B2.5, Fe74.5Mo5.5P11C5B2.5Si1.5, Fe70Mo5Ni5P12.5C5B2.5, Fe70Mo5Ni5P11C5B2.5Si1.5, Fe68Mo5Ni5Cr2P12.5C5B2.5, and Fe68Mo5Ni5Cr2P11C5B2.5Si1.5, described in U.S. Patent Application Publication No. 2010/0300148. Some additional examples of amorphous alloys of different systems are provided in Table 2.








TABLE 2







Exemplary amorphous alloy compositions















Alloy
Atm %
Atm %
Atm %
Atm %
Atm %
Atm %
Atm %
Atm %





1
Fe
Mo
Ni
Cr
P
C
B




68.00%
5.00%
5.00%
2.00%
12.50%
5.00%
2.50%



2
Fe
Mo
Ni
Cr
P
C
B
Si



68.00%
5.00%
5.00%
2.00%
11.00%
5.00%
2.50%
1.50%


3
Pd
Cu
Co
P



44.48%
32.35% 
4.05%
19.11% 


4
Pd
Ag
Si
P



77.50%
6.00%
9.00%
7.50%


5
Pd
Ag
Si
P
Ge



79.00%
3.50%
9.50%
6.00%
 2.00%


6
Pt
Cu
Ag
P
B
Si



74.70%
1.50%
0.30%
18.0%
 4.00%
1.50%









In some embodiments, a composition having an amorphous alloy can include a small amount of impurities. The impurity elements can be intentionally added to modify the properties of the composition, such as improving the mechanical properties (e.g., hardness, strength, fracture mechanism, etc.) and/or improving the corrosion resistance. Alternatively, the impurities can be present as inevitable, incidental impurities, such as those obtained as a byproduct of processing and manufacturing. The impurities can be less than or equal to about 10 wt %, such as about 5 wt %, such as about 2 wt %, such as about 1 wt %, such as about 0.5 wt %, such as about 0.1 wt %. In some embodiments, these percentages can be volume percentages instead of weight percentages. In one embodiment, the alloy sample/composition consists essentially of the amorphous alloy (with only a small incidental amount of impurities). In another embodiment, the composition includes the amorphous alloy (with no observable trace of impurities).
In one embodiment, the final parts exceeded the critical casting thickness of the bulk solidifying amorphous alloys.
In embodiments herein, the existence of a supercooled liquid region in which the bulk-solidifying amorphous alloy can exist as a high viscous liquid allows for superplastic forming. Large plastic deformations can be obtained. The ability to undergo large plastic deformation in the supercooled liquid region is used for the forming and/or cutting process. As oppose to solids, the liquid bulk solidifying alloy deforms locally which drastically lowers the required energy for cutting and forming. The ease of cutting and forming depends on the temperature of the alloy, the mold, and the cutting tool. As higher is the temperature, the lower is the viscosity, and consequently easier is the cutting and forming.
Embodiments herein can utilize a thermoplastic-forming process with amorphous alloys carried out between Tg and Tx, for example. Herein, Tx and Tg are determined from standard DSC measurements at typical heating rates (e.g. 20° C./min) as the onset of crystallization temperature and the onset of glass transition temperature.
The amorphous alloy components can have the critical casting thickness and the final part can have thickness that is thicker than the critical casting thickness. Moreover, the time and temperature of the heating and shaping operation is selected such that the elastic strain limit of the amorphous alloy could be substantially preserved to be not less than 1.0%, and preferably not being less than 1.5%. In the context of the embodiments herein, temperatures around glass transition means the forming temperatures can be below glass transition, at or around glass transition, and above glass transition temperature, but preferably at temperatures below the crystallization temperature TX. The cooling step is carried out at rates similar to the heating rates at the heating step, and preferably at rates greater than the heating rates at the heating step. The cooling step is also achieved preferably while the forming and shaping loads are still maintained.
Electronic Devices
The embodiments herein can be valuable in the fabrication of electronic devices using a BMG. An electronic device herein can refer to any electronic device known in the art. For example, it can be a telephone, such as a cell phone, and a land-line phone, or any communication device, such as a smart phone, including, for example an iPhoneTM, and an electronic email sending/receiving device. It can be a part of a display, such as a digital display, a TV monitor, an electronic-book reader, a portable web-browser (e.g., iPadTM), and a computer monitor. It can also be an entertainment device, including a portable DVD player, conventional DVD player, Blue-Ray disk player, video game console, music player, such as a portable music player (e.g., iPodTM), etc. It can also be a part of a device that provides control, such as controlling the streaming of images, videos, sounds (e.g., Apple TVTM), or it can be a remote control for an electronic device. It can be a part of a computer or its accessories, such as the hard drive tower housing or casing, laptop housing, laptop keyboard, laptop track pad, desktop keyboard, mouse, and speaker. The article can also be applied to a device such as a watch or a clock.
Embodiments
The embodiments described herein relate to BMG articles with high bulk and methods of making them. The embodiments described herein also relate to articles and/or electronic devices that include the disclosed BMG articles and their methods.
In accordance with various embodiments, there is provided a BMG article processed to have greater than critical dimensions. An exemplary BMG article can be formed of a material including one or more BMG alloys with all dimensions greater than a critical dimension of each BMG alloy used. Such BMG article can include at least one bulk component and/or one or more fixation elements configured on surface of the bulk component or inserted in the bulk component.
In accordance with various embodiments, there is provided a method of making a bulk metallic glass (BMG) part. In this method, a part in a first form formed of one or more BMG alloys can be provided having at least one dimension less than or equal to a critical dimension of each BMG alloy used. The part in the first form can then be heated to at least above the glass transition temperature of each BMG alloy and further be plastically formed into a second form. The part in the second form can have all dimensions greater than the critical dimension. The heating and plastically forming (or thermo-plastic-forming) processes can be conducted simultaneously or sequentially. In one embodiment, the part in the first form can have a near net shape and the part in the second form can have the net shape by thermo-plastic-forming.
In accordance with various embodiments, there is provided a method of making a bulk metallic glass (BMG) part. In this method, a part in a first form can be formed of one or more BMG alloys and can have one or more dimensions less than or equal to a critical dimension of each BMG alloy used. The part in the first form can then be heated to at least above the glass transition temperature of each BMG alloy and further be shaped into a second form such that all dimensions thereof are greater than the critical dimension. The heating and shaping processes can be conducted simultaneously or sequentially. In embodiments, a mold with a pre-determined shape/dimension can be used for shaping the BMG article.
The embodiments take advantage of the thermo-plastic formation of BMG alloys to produce parts with high bulk. The embodiments also enable the production of bulk components and/or fixation elements that retain many, if not all, of the characteristics of the BMG alloy materials. The embodiments also make it possible to form devices/articles/parts/components having critical dimension (e.g., thicknesses) far greater than the critical dimension of each BMG alloy selected.
FIGS. 3A-3D illustrate an exemplary BMG article at various fabrication stages in accordance with various embodiments of the present invention.
In FIG. 3A, an exemplary BMG article in a first form 300A (which is also referred to herein as a “BMG feedstock”) can be provided or pre-fabricated.
The part 300A can have any possible three dimensional (3D) structures. For example, the part 300A can include, e.g., at least one bulk component 310 and/or one or more fixation elements 320 connected to each bulk component. Other possible components formed of BMG alloys and/or non-BMG materials can be included in the part 300A in accordance with various embodiments of the present teachings.
The bulk component 310 can be formed of one or more BMG alloys or a material containing one or more BMG alloys. The bulk component 310 can further include non-BMG materials. Alternatively, the bulk component 310 can include one or more layers each having the same or different materials. For example, the bulk component 310 can include stacked layers (not illustrated in FIG. 3A) formed of same or different BMG alloys and/or stacked layers with some layers formed of BMG alloys and some layers formed of non-BMG materials.
The fixation element 320 can be configured on the bulk component 310 or inserted into the bulk component 310. For example, when multi-layers of bulk component are used, the fixation element 320 can be connected onto/into each layer of the bulk component or connected onto/into interfaces between adjacent layers of the bulk component.
In one embodiment, the fixation element 320 can include migration resistant features. The migration resistant features may facilitate engagement of the bulk component 310 with the ends of adjacent device components (e.g., for an electronic device) by providing a mechanical interlock as a result of penetration and/or deformation of the ends of the adjacent device components. Such mechanical stability can minimize the risk of post-operative instability, movement, dislodging or expulsion of the bulk component 310. Exemplary fixation element 320 can include, without limitation, flaps, teeth, deployable teeth, deployable spikes, flexible spikes, shaped teeth, flexible teeth, anchors, fins, insertable or expandable fins, anchors, screws, ridges, serrations, plates, rods, ingots, discs, balls or other similar structures on/in the bulk component 310.
In embodiments, the bulk component 310 and the fixation element 320 can take the same or different materials, shapes, structures, dimensions, etc. The bulk component 310 and/or the fixation element 320 can be simultaneously or sequentially processed, for example, be heated, pressed, molded, shaped, etc.
During formation of the part in the first form 300A, rapid cooling are often used in order to avoid crystallization of the BMG alloy(s). Thus, the dimension of each component in the part made from BMG alloy(s) often becomes a limiting dimension, which is generally referred to as the “critical dimension.” A critical dimension of a BMG alloy can be obtained by heat-flow calculations, taking into account the critical cooling rate. As a result, the bulk component 310 and/or the fixation element 320 can have at least one dimension less than or equal to a critical dimension of the BMT alloy(s) used.
In FIG. 3B, the BMG article in the first form 300A shown in FIG. 3A can be heated by any possible heating means 330 to at least above the glass transition temperature of the BMG alloy(s) used. In some cases, the heating temperature can be lower than a melting temperature and/or a crystallization temperature of the BMG alloy(s) used. As discussed in FIG. 2, the BMG article 300A can be heated into the supercooled liquid region, e.g., with the highest temperature being above Tnose or below Tnose, up to about Tm, i.e., between Tg and Tm but not reaching Tx. In one example, the heating can be carried out at a temperature of from about 100° C. to about 900° C., or from about 100° C. to about 750° C. The heating can be performed for a period of time ranging anywhere from about 5 minutes to about 10 hours, or from about 15 minutes to about 5 hours, or from about 25 minutes to about 3 hours. In embodiments, the bulk component 310 and/or the fixation element 320 of the BMG article 300A can be heated simultaneously or sequentially. In embodiments, one of them such as bulk component 310 can be heated, while no heating or other processes applied to the other such as the fixation element 320, and vice versa.
Because of the large plastic formability in the supercooled liquid region of the BMG alloy(s) when heated above its glass transition temperature and/or below its crystallization temperature (i.e., between Tg and Tx in FIG. 2), BMG article containing BMG alloy(s) can be further processed, e.g., pressed, shaped, or re-shaped, to form desired BMG-containing parts. It is believed that the unique rheological properties of the BMG alloy materials in the supercooled liquid state, large plastic deformations can be obtained, and wetting may take place in the supercooled liquid state. The ability to undergo large plastic deformation in the supercooled liquid region is used for the forming and/or shaping (or re-shaping) process. As opposed to solids, the BMG alloy(S) deform locally, which drastically lowers the required energy for forming, shaping, and/or re-shaping. The ease of forming and/or (re-)shaping depends on the temperature of the alloy, the pressure used, the mold selected, etc. As temperature is increased, viscosity decreases, and consequently, it is easier to form or (re-)shape into the final part. In the context of the embodiments herein, temperatures around glass transition means the forming temperatures can be below glass transition, at or around glass transition, and above glass transition temperature, but preferably at temperatures below the crystallization temperature Tx.
Still in FIG. 3B, a pressure means 340 can be used to press the part 300A while heating. Alternatively, following the heating process, the pressure can be applied to the heated part in the first form. The part in the first form 300A can be plastically formed into a second form as shown in FIGS. 3C-3D. In one embodiment, the heating means 330 and/or the pressure means 340 can be configured to accommodate the BMG article in the first form 300A according to its dimension and/or shape. The BMG article in the second form can have all dimensions greater than the BMG alloy's critical dimension.
In some cases, in addition to providing greater dimension, the BMG article in the first form (see FIG. 3A) can be at least partially or at least locally re-shaped (e.g., in cross-section shape, dimension, etc.) into the second form (see FIG. 3D), e.g., by replication from a predetermined mold. For example, the predetermined mold can be provided having pre-determined dimensions and/or shapes. The pre-determined dimensions and/or shapes can be determined by the dimensions/shapes of the BMG article 300A in FIG. 3A and the final part 300D in FIG. 3D. In embodiments, the predetermined mold can be permanent.
In an exemplary embodiment, the predetermined mold can be formed by the heating means and the pressure means. In this case, the BMG article 300A can first be fed into the predetermined mold. While heating by the heating means 330, a pressure can be applied, e.g., by using the pressure means 340, to the heating BMG article 300A against the mold such that the part can be plastically shaped into the desired second form. In embodiments, the BMG article 300A can first be heated and then moved into the predetermined mold, or other components that have pre-determined dimensions/shapes. The heated BMG article can further be pressed and/or (re-)shaped as desired.
In embodiments, the time and temperature of the thermo-plastic-formation can be selected such that the elastic strain limit of the BMG article including the bulk component 310 and the fixation element 320 can be substantially preserved to be not less than about 1.0%, and preferably not less than about 1.5%.
In FIG. 3D, the heating/pressure means or the exemplary mold can be removed, whereby leaving the BMG article in the second form 300D. In embodiments, the BMG article 300D is directly formed from the BMG article 300A into the final part by the disclosed thermo-plastic-formation, no other processes or steps such as cooling are necessary.
In this manner, the BMG article 300D can include, e.g., at least a bulk component 310D and/or one or more fixation elements 320D, formed of a material including one or more BMG alloys and having all dimensions greater than their critical dimension. In embodiments, the bulk component 310A and/or the fixation element 320A in FIG. 3A can have a near net shape, while the bulk component 310D and/or the fixation element 320D in FIG. 3D can have a net shape. In embodiments, depending on the temperature, pressure, mold, etc. the bulk component 310A and/or the fixation element 320A in FIG. 3A can be at least partially re-shaped having different cross-sections and dimensions to form the bulk component 310D and/or the fixation element 320D in FIG. 3D. Corresponding to the part 300A, the bulk component 310D and/or the fixation element 320D can be formed as stacked layers with at least one layer including BMG alloys.

## Claims

1. A method of making a bulk metallic glass (BMG) article with all dimensions of the article greater than the critical casting thickness comprising:
forming an article of one or more BMG alloys in a first form having at least one dimension less than or equal to a critical casting thickness of each BMG alloy of the one or more BMG alloys;
the step of forming including stacking a plurality of layers of the BMG alloys to form the article, the layers including an interface between each of the plurality of layers;

associating a fixation element with the article to provide a mechanical interlock with an adjacent device component;
the step of associating including configuring or connecting the fixation element onto one or more of the layers and/or onto at least one interface;

heating the article in the first form to at least above the glass transition temperature of the each BMG alloy; and
plastically forming the BMG article into a second form such that all dimensions of the BMG article are greater than the critical casting thickness.

2. The method of claim 1, wherein the step of plastically forming the article into a second form comprises subjecting the article in the first form to a pressure while heating.

3. The method of claim 1, wherein the step of plastically forming the article into a second form comprises subjecting the heated article in the first form to a pressure.

4. The method of claim 1, wherein the article is heated to lower than a melting temperature or a crystallization temperature of the each BMG alloy.

5. The method of claim 1, wherein heating is carried out at a temperature of from about 100° C. to about 900° C.

6. The method of claim 1, wherein heating is carried out at a temperature of from about 100° C. to about 750° C.

7. The method of claim 1, wherein the article in first form has a near net shape and the article in the second form has a net shape.

8. The method of claim 1, wherein one or more of the bulk component and the fixation element are formed of the one or more BMG alloys.

9. The method of claim 1, wherein the fixation element is formed of a material comprising a non-BMG alloy.

10. The method of claim 1, wherein one or more of the bulk component and the fixation element comprise one or more layers formed of materials comprising the one or more alloys.

11. The method of claim 1, wherein one or more of the bulk component and the fixation element sustain strain up to 1.5% or more without any permanent deformation or breakage.

12. The method of claim 1, wherein the each BMG alloy comprises an alloy of aluminum, bismuth, cobalt, copper, gallium, gold, indium, iron, lead, magnesium, mercury, nickel, potassium, plutonium, rare earth alloys, rhodium, silver, titanium, tin, uranium, zinc, zirconium, and mixtures thereof.

13. The method of claim 1 wherein at least one of the layers comprises a non-BMG material.

14. A method of making a bulk metallic glass (BMG) article comprising:
forming the article in a first form comprising one or more BMG alloys and having one or more dimensions less than or equal to a critical casting thickness of each BMG alloy of the one or more BMG alloys;
the step of forming including stacking a plurality of layers of the BMG alloys to form the article, the layers including an interface between each of the plurality of lavers;

associating a fixation element with the article to provide a mechanical interlock with an adjacent device component;
the step of associating including inserting the fixation element into at least one layer and/or into at least one interface;
heating the article in the first form to at least above the glass transition temperature of each BMG alloy; and
shaping the article in the first form into the BMG article having a second form such that all dimensions thereof are greater than the critical casting thickness.

15. The method of claim 14, further comprising locally re-shaping the article into the second form.

16. The method of claim 14, further comprising shaping the article while heating or after heating.

17. The method of claim 14, further comprising using a mold having a pre-determined shape to accommodate the article during one or more steps of heating and shaping.

18. The method of claim 14, further comprising pressing the article during one or more steps of heating and shaping.

19. The method of claim 14, wherein one or more of the bulk component and the fixation element are formed of the one or more BMG alloys.

20. The method of claim 14, wherein the fixation element is formed of a material comprising a non-BMG alloy.

21. The method of claim 18, wherein one or more of the bulk component and the fixation element sustain strain up to 1.5% or more without any permanent deformation or breakage.

22. The method of claim 14, wherein the each BMG alloy comprises an alloy of aluminum, bismuth, cobalt, copper, gallium, gold, indium, iron, lead, magnesium, mercury, nickel, potassium, plutonium, rare earth alloys, rhodium, silver, titanium, tin, uranium, zinc, zirconium, and mixtures thereof.

23. The method of claim 14 wherein at least one of the layers comprises a non-BMG material.