Patent Application
20140284019
1. Field
The present disclosure is generally related to a system and method for melting and molding meltable materials, including amorphous alloys.
2. Description of Related Art
Various methods have been used to mold molten metal materials. For example, die casting generally consists of injecting molten metal under high pressure into a mold. There are two methods typically used to inject molten metal into a mold: cold chamber and hot chamber. In hot chamber methods, low melting point alloys are used in a gooseneck feeding system, where the injection mechanism is immersed in the molten metal bath. On the other hand, in cold chamber methods, higher melting point alloys (e.g., aluminum alloy) can be used and melted in a crucible before pouring into a cold chamber. Some variations of a cold chamber include squeeze casting and semi-solid molding.
Another method of forming and molding material is called “Metal Injection Molding” or MIM, where granular particles of certain metal are mixed with a binder, formed into shape, and then the binder is stripped and sintered.
One aspect of the disclosure provides an injection molding system having: a melt zone configured to melt meltable material received therein, and a plunger rod configured to eject molten material from the melt zone and into a mold, wherein the plunger rod and melt zone are provided in-line and on a horizontal axis, such that the plunger rod is moved in a horizontal direction through the melt zone to move the molten material into the mold.
Another aspect of the disclosure provides an injection molding system having: a vessel that has a body for receiving meltable material and configured to melt the material therein, a plunger rod configured to move molten material from the vessel, through a transfer sleeve, and into a mold, wherein the plunger rod, vessel, and transfer sleeve are provided in-line and on a horizontal axis, such that the plunger rod is moved in a horizontal direction through the vessel to move the molten material into the transfer sleeve.
Yet another aspect of the disclosure provides an injection molding system having: a temperature regulated vessel, an induction source, a vacuum mold, and a plunger rod. The temperature regulated vessel has a body for receiving amorphous alloy material and configured to melt the amorphous alloy material therein, as well as one or more temperature regulating lines configured to flow a liquid therein for regulating a temperature of the vessel. The induction source is positioned adjacent the temperature regulated vessel and is configured to melt the amorphous alloy material. The vacuum mold is configured to receive molten amorphous alloy through an inlet and configured to mold the molten amorphous alloy material and under vacuum. The plunger rod is configured to eject the molten amorphous alloy material from the body of the temperature regulated vessel into the vacuum mold. The temperature regulated vessel, the inlet of the vacuum mold, and the plunger rod are provided in-line and on a horizontal axis, such that the plunger rod is moved in a horizontal direction through the body of the temperature regulated vessel to eject molten material from the temperature regulated vessel and into the vacuum mold via the inlet.
Other features and advantages of the present disclosure will become apparent from the following detailed description, the accompanying drawings, and the appended claims.
The methods, techniques, and devices illustrated herein are not intended to be limited to the illustrated embodiments. 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%.
As disclosed herein, a system (or a device or a machine) is configured to perform injection molding of material(s) (such as amorphous alloys). The system is configured to process such materials or alloys by melting at higher melting temperatures before injecting the molten material into a mold for molding. As further described below, parts of the system are positioned in-line with each other. In accordance with some embodiments, parts of the system (or access thereto) are aligned on a horizontal axis.
The meltable material can be received in the melt zone in any number of forms. For example, the meltable material may be provided into melt zone 12 in the form of an ingot (solid state), a semi-solid state, a slurry that is preheated, powder, pellets, etc. In some embodiments, a loading port (such as the illustrated example of an ingot loading port 18) may be provided as part of injection molding system 10. Loading port 18 can be a separate opening or area that is provided within the machine at any number of places. In an embodiment, loading port 18 may be a pathway through one or more parts of the machine. For example, the material (e.g., ingot) may be inserted in a horizontal direction into vessel 20 by plunger 14, or may be inserted in a horizontal direction from the mold side of the injection system 10 (e.g., through mold 16 and/or through a transfer sleeve 30 into vessel 20). In other embodiments, the meltable material can be provided into melt zone 12 in other manners and/or using other devices (e.g., through an opposite end of the injection system).
Melt zone 12 includes a melting mechanism configured to receive meltable material and to hold the material as it is heated to a molten state. The melting mechanism may be in the form of a vessel 20, for example, that has a body 22 for receiving meltable material and configured to melt the material therein.
Vessel 20 may also have an inlet for inputting material (e.g., feedstock) into a receiving or melting portion 24 of its body. In the embodiment shown in
In an embodiment, body 22 and/or its melting portion 24 may comprise substantially rounded and/or smooth surfaces. For example, a surface of melting portion 24 may be formed in an arc shape. However, the shape and/or surfaces of body 22 are not meant to be limiting. Body 22 may be an integral structure, or formed from separate parts that are joined or machined together. Body 22 may be formed from any number of materials (e.g., copper, silver), include one or more coatings, and/or configurations or designs. In an embodiment, body 22 of vessel 20 is formed from a material that does not give off or transfer contaminants to the meltable/molten material. For example, one or more surfaces may have recesses or grooves therein.
The body 22 of vessel 20 may be configured to receive the plunger rod therethrough in a horizontal direction to move the molten material. That is, in an embodiment, the melting mechanism is on the same axis as the plunger rod, and the body can be configured and/or sized to receive at least part of the plunger rod. Thus, plunger rod 14 can be configured to move molten material (after heating/melting) from the vessel by moving substantially through vessel 20, and into mold 16. Referencing the illustrated embodiment of system 10 in
To heat melt zone 12 and melt the meltable material received in vessel 20, injection system 10 also includes a heat source that is used to heat and melt the meltable material At least melting portion 24 of the vessel, if not substantially the entire body 22 itself, is configured to be heated such that the material received therein is melted. Heating is accomplished using, for example, an induction source 26 positioned within melt zone 12 that is configured to melt the meltable material. In an embodiment, induction source 26 is positioned adjacent body 22 of vessel 20. For example, as shown in
In one embodiment, the vessel 20 is a temperature regulated vessel. Such a vessel may include one or more temperature regulating lines, such as cooling line(s) 25 shown in
After the material is melted in the vessel 20, plunger 14 may be used to force the molten material from the vessel 20 and into a mold 16 for molding into an object, a part or a piece. In instances wherein the meltable material is an alloy, such as an amorphous alloy, the mold 16 is configured to form a molded bulk amorphous alloy object, part, or piece. Mold 16 has an inlet for receiving molten material therethrough. An output of the vessel 20 and an inlet of the mold 16 can be provided in-line and on a horizontal axis such that plunger rod 14 is moved in a horizontal direction through body 22 of the vessel to eject molten material and into the mold 16 via its inlet.
As previously noted, systems such as injection molding system 10 that are used to mold materials such as metals or alloys may implement a vacuum when forcing molten material into a mold or die cavity. Injection molding system 10 can further includes at least one vacuum source 38 or pump that is configured to apply vacuum pressure to at least melt zone 12 and mold 16. The vacuum pressure may be applied to at least the parts of the injection molding system 10 used to melt, move or transfer, and mold the material therein. For example, the vessel 20, transfer sleeve 30, and plunger rod 14 may all be under vacuum pressure and/or enclosed in a vacuum chamber.
In an embodiment, mold 16 is a vacuum mold that is an enclosed structure configured to regulate vacuum pressure (e.g., via a valve 33) therein when molding materials.
Generally, first plate 32 may be connected to transfer sleeve 30. In accordance with an embodiment, plunger rod 14 is configured to move molten material from vessel 20, through a transfer sleeve 20, and into mold 16. Transfer sleeve 30 (sometimes referred to as a cold sleeve or injection sleeve in the art) may be provided between melt zone 12 and mold 16. Transfer sleeve 30 has an opening that is configured to receive and allow transfer of the molten material therethrough and into mold 16 (using plunger 14). Its opening may be provided in a horizontal direction along the horizontal axis (e.g., X axis). The transfer sleeve need not be a cold chamber. In an embodiment, at least plunger rod 14, vessel 20 (e.g., its receiving or melting portion), and opening of the transfer sleeve 30 are provided in-line and on a horizontal axis, such that plunger rod 14 can be moved in a horizontal direction through vessel 20 in order to move the molten material into (and subsequently through) the opening of transfer sleeve 30.
Referring back to
The vacuum ejector box 36 is positioned adjacent at least first and second plates 32 and 34. In an embodiment, the ejector box is enclosed and is configured to be vacuum sealed by vacuum pressure from vacuum source 38 (pump). In an embodiment, included in the enclosed vacuum ejector box 36 has an ejector mechanism 46 configured to eject molded (amorphous alloy) material from the mold cavity between the at least first and second plates 32 and 34. Ejector mechanism 46 can be vacuum sealed within the enclosed vacuum ejector box 36 and any adjacent plate or interface sealed with the open face of the box 36. Ejector mechanism 46 may include an ejector plate 66, in accordance with an embodiment. The ejector plate is configured to move within the enclosed ejector box to eject the molded material from the mold 16. More specifically, ejector plate 66 may have one or more (multiple) ejector pins (not shown) extending in a linear direction therefrom. Upon movement of ejector plate 66, the ejector pins are moved relatively to eject the molded material from the mold cavity of mold 16. The ejection mechanism is associated with or connected to an actuation mechanism (not shown) that is configured to be actuated in order to eject the molded material or part (e.g., after first and second parts 32 and 34 are moved horizontally and relatively away from each other, after vacuum pressure between the plates 32 and 34 is released). The ejector pins may be configured to push molded material away from cavity 44, for example.
The illustrated mold 16 in
Generally, the injection molding system 10 may be operated in the following manner: The vacuum is applied to the injection molding system 10. Meltable material (e.g., amorphous alloy or BMG) is loaded into a feed mechanism (e.g., loading port 18) while held under vacuum, and a single ingot (feedstock) is loaded, inserted and received into the melt zone 12 into the vessel 20 (surrounded by the induction coil 26). The injection molding machine “nozzle” stroke or plunger 14 can be used to move the material, as needed, into the melting portion 24 of the vessel 20. The material is heated through the induction process. In an embodiment, the injection molding machine controls the temperature through a closed loop system, which will stabilize the material at a specific temperature (e.g., using a temperature sensor and a controller). In another embodiment, the injection molding machine controls the temperature through an open loop system. During heating/melting, a cooling system can be activated to flow a (cooling) liquid in any cooling line(s) of the vessel 20. Once the temperature is achieved and maintained to melt the meltable material, the machine will then begin the injection of the molten material from vessel 20, through transfer sleeve 20, and into vacuum mold 16 by moving in a horizontal direction (from right to left) along the horizontal axis. This may be controlled using plunger 14, which can be activated using a servo-driven drive or a hydraulic drive. The mold 16 is configured to receive molten material through an inlet and configured to mold the molten material under vacuum. That is, the molten material is injected into a cavity between the at least first and second plates to mold the part in the mold 16. Once the mold cavity has begun to fill, vacuum pressure (via the vacuum lines and vacuum source 38) can be held at a given pressure to “pack” the molten material into the remaining void regions within the mold cavity and mold the material. After the molding process (e.g., approximately 10 to 15 seconds), the vacuum pressure applied to the mold 16 is released. For example, the pressure can be released using vacuum break valve 33 and/or the vacuum port. Mold 16 is then opened to relieve pressure and to expose the part to the atmosphere. Ejector mechanism 46 is actuated to eject the solidified, molded object from between the at least first and second plates of mold 16 (ejector plate 66 is moved in a horizontal and linear direction (e.g., towards the right) via an actuation device and the ejector pins assist in ejecting the part from the cavity). Thereafter, the process can begin again. Mold 16 can then be closed by moving at least the at least first and second plates relative to and towards each other such that the first and second plates are adjacent each other. The melt zone 12 and mold 16 is evacuated via the vacuum source once the plunger 14 has moved back into a load position, in order to insert and melt more material and mold another part.
Accordingly, the herein disclosed embodiments illustrate an exemplary injection system that has its melting system in-line with at least one plunger rod along a horizontal axis. The system does not require use of a separate chamber to melt and then pour molten metal into the plunger cavity/cold sleeve, as in known systems. The system does not need to include immersion of the plunging system into a molten metal bath, as well as reduced or no sintering. Also, it more precisely controls the volume of feed stock/inserted material and final molded part, and reduces heat loss. System 10 enables molding of material is that is substantially free of contamination because it is formed from a clean melt with low oxygen and nitrogen (due to applied vacuum pressure). Additionally, the material is also substantially free of contamination because, in accordance with an embodiment, the meltable material is configured to be melted in a vessel comprising a surface which does not give off contaminants (such as known graphite crucibles which can induce carbine particles into the melt). System 10 further provides a more efficient delivery method to its mold.
The disclosed system enables injection molding of objects to be performed at a faster volumetric flow rate than plastic injection molding techniques (but may be slower than conventional die cast machines). For example, the flow rate of casting using the herein described system(s) may be performed at approximately zero to 1,000 cm3.
Although not described in great detail, the disclosed injection system may include additional parts including, but not limited to, one or more sensors, flow meters, etc. (e.g., to monitor temperature, cooling water flow, etc.), and/or one or more controllers. Also, seals can be provided with or adjacent any of number of the parts to assist during melting and formation of a part of the molten material when under vacuum pressure, by substantially limiting or eliminating substantial exposure or leakage of air. For example, the seals may be in the form of an O-ring. A seal is defined as a device that can be made of any material and that stops movement of material (such as air) between parts which it seals. The injection system may implement an automatic or semi-automatic process for inserting meltable material therein, applying a vacuum, heating, injecting, and molding the material to form a part.
The material to be molded (and/or melted) using any of the embodiments of the injection system as disclosed herein may include any number of materials and should not be limited. In one embodiment, the material to be molded using the disclosed injection molding system 10 is an amorphous alloy, which are metals that may behave like plastic, or alloys with liquid atomic structures.
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.
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
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
The schematic TTT diagram of
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
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.
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, Cl, Br, I, At, O, 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.
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.
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.
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.
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 25X 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)b(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)b(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 aforedescribed alloy system is a Zr—Ti—Ni—Cu—Be based amorphous alloy under the trade name Vitreloy™, 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 Fe72Al5Da2P11C6B4. Another example is Fe72Al7Zr10Mo5W2B15. 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%.
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 could be 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.
The aforedescribed embodiments of the injection molding system 10 can be used in a fabrication device and/or process including using BMG (or amorphous alloys). Because of the superior properties of BMG, BMG can be made into structural components of bulk amorphous alloy in a variety of objects, devices and parts. One such type of device is an electronic device.
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, Blu-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.
While the principles of the disclosure have been made clear in the illustrative embodiments set forth above, it will be apparent to those skilled in the art that various modifications may be made to the structure, arrangement, proportion, elements, materials, and components used in the practice of the disclosure.
It will be appreciated that various of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems/devices or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/US11/54153 | 9/30/2011 | WO | 00 | 5/23/2014 |
