KR20160086946A - A method and system for fabricating bulk metallic glass sheets - Google Patents

Abstract

The present invention relates to a method and hardware for transforming a metallic glass under low force and stabilized conditions for producing a large area metallic glass sheet of thin film. This is typically based on the combination of thermoplastic rolling and stretching combined with the preheating method. The main mode of modification depends on BMG conditions such as thickness, viscosity and crystallization time.

Description

Technical Field [0001] The present invention relates to a bulk metal glass sheet,

Cross-reference to related application

This application claims benefit of U.S. Provisional Application No. 61 / 919,158, filed December 20, 2013, and U.S. Provisional Application No. 62 / 025,558, filed July 17, 2014, each of which is incorporated by reference herein in its entirety Are included by reference.

Field of invention

The present invention relates generally to a method and apparatus for transforming metallic glasses for making metallic glass sheets, strips and ribbons.

A statement of federal sponsorship research or development

The present invention was conducted with Government support under W911NF-11-I-0380 awarded by the United States Army Research Office. The United States government has certain rights in this invention.

Bulk metallic glass (BMG), also known as bulk solidifying amorphous alloy composition, has excellent properties, such as high yield strength, large elastic strain, strain limit and high corrosion resistance, it is a class of amorphous metal alloy materials which are considered as promising materials for various applications.

An inherent property of BMG is that it has a ΔTsc, which is a super-cooled liquid region (SCLR), and ΔTsc is the relative dimension of the stability of the viscous liquid form. SCLR is defined as the temperature difference between crystallization initiation, Tx and glass transition temperature, and Tg of a particular BMG alloy. These values can usually be measured using standard calorimetry techniques, for example, DSC (Differential Scanning Calorimetry) measurements at 20 ° C / min.

Generally, a large ΔTsc is associated with a low critical cooling rate, but a significant amount of scatter is present at a ΔTsc value of greater than 40 ° C. Bulk-solidified amorphous alloys with ΔTsc above 40 ° C., preferably above 60 ° C., even more preferably above 70 ° C., are highly desirable because of their relative ease of deformation. In the subcooled liquid region, bulk solids behave like high viscosity liquids. The viscosity of bulk solidified alloys with widely supercooled liquid regions decreases from 10 ¹² Pa · s to 10 ⁷ Pa · s at the glass transition temperature and in some cases to 10 ⁵ Pa · s. Heating the bulk solidified alloy above the crystallization temperature causes crystallization of the alloy and a direct loss of good properties, which can no longer be molded.

Superplastic forming (SPF) of amorphous metal alloys involves heating an amorphous metal alloy with SCLR and molding under an applied pressure. The process is analogous to the processing of thermoplastics, where the formability in inverse proportion to the viscosity increases with increasing temperature. However, in contrast to thermoplastics, high viscosity amorphous metal alloys are metastable and eventually crystallized.

Crystallization of amorphous metal alloys should be avoided for several reasons. First, it impairs the mechanical properties of the amorphous metal alloy. From a processing viewpoint, crystallization limits the processing time for hot-forming operations because the flow in the crystalline material is up to 10 times higher than in liquid amorphous metal alloys. The crystallization kinetic of various amorphous metal alloys allows processing times of several minutes to several hours in the stated viscosity range. This makes the superplastic forming process a finely tunable process that can be performed on a convenient time scale and enables a complex geometric structure in a net shape.

The ability of an amorphous metal alloy to be thermoplasticly formed is described as its formability, a parameter directly related to the interaction between temperature dependent viscosity and crystallization time. Crystallization should be avoided during the TPF of the amorphous metal alloy because this impairs the properties of the amorphous metal alloy and delays its formation. Thus, the total time elapsed during the TPF of the amorphous metal alloy should be less than the time for crystallization.

The sheet is one of the most important forms of metal as a final product or as a feedstock for further processing. In particular, in the case of metallic glass, the sheet is highly desirable because the sheet is a thin film in one dimension, and in this geometry, bulk metallic glasses (BMGs) often exhibit bending ductility. For example, medium-range BMGs with a thickness of ~ 1 mm were found to exhibit bending ductility.

However, the production of BMG sheets, particularly large BMG sheets, is not simple and has not been demonstrated in the prior art for sheets larger than about 10 cm x 10 cm.

Conventional casting is not suitable for the production of BMG sheets produced through the rolling process, because the process is contradictory - on the one hand, rapid cooling to avoid crystallization and on the other hand the entire mold cavity, Lt; RTI ID = 0.0 > cooling < / RTI > Twin-roll casting has to be performed under a high vacuum or protective atmosphere, and has a non-simple adjustment problem. Cold rolling of BMG is very limited because at room temperature BMG is slightly deformed to a very localized state through the formation of shear bands, where most deformation is localized, which is counter to the homogeneous strain required for rolling. As a result, the deformation achieved during cold rolling is very non-homogeneous and, in the case of feedstock materials of thicknesses greater than about 1 mm, causes direct cracking.

Deformation at the temperature (T _g < T < T _x ) within the subcooled liquid region of a particular BMG was also studied for molding and processing. The BMG is homogeneously deformed at low stress, which is ~ 1/100 of the room temperature yield strength, at a temperature within the subcooled liquid region for the actual strain rate, .

Attempts have been made to roll BMG in a supercooled liquid region. The most successful approach was to be performed by a heating plate through which the heat is passed through the roller with the feedstock. Here, however, the BMG is permanently in contact with the sandwiched heating plate, thereby heating the BMG. Thus, the main advantage of rolling, which is the reduction of the contact area between the mold (roll) and the material, is eliminated, and the deformation is considerably limited. The largest and thinnest piece achieved by this method is approximately 7 cm x 5 cm and the thickness is approximately 0.4 mm. Since the feedstock is in permanent contact with the mold (heating plate), it is not possible to achieve a giant thin sheet by this technique.

For thermoplastic forming processes where BMG is permanently in contact with the mold, the increase in radius is proportional to the time ^ ^1/8 for static pressure. Thus, an unrealistically long time (until the crystallization time far exceeds the maximum machining time) is necessary or impractically high to achieve this large radius. Therefore, the technique in which the entire BMG contacts the mold is not suitable for manufacturing a large thin BMG sheet.

U.S. Patent No. 8,485,245 to Prest et al., Which is hereby incorporated by reference in its entirety, teaches that a molten BMG alloy can be cast into a molten metal bath having a higher density and lower temperature than a BMG melt in a float chamber Pouring and solidifying the BMG melt and forming a BMG sheet. This process mainly depends on the solidification of the BMG melt.

However, since the thickness of the obtained equilibrium sheet is limited by the surface tension and gravity of the BMG melt and the molten bath, it is difficult to control the thickness. In addition, an inert gas atmosphere and / or vacuum is required in the molten alloy chamber and float chamber.

U.S. Patent Publication No. 2013/0025746 to Hofmann et al., The disclosure of which is incorporated herein by reference, describes a method of making a BMG sheet through twin roll casting of BMG melt under an inert atmosphere. The method comprises injecting a molten BMG melt into a cold roll to solidify the metal glass melt into a sheet. As a further option, the discharged BMG sheet may be further thermoplastically formed into a sheet of thinner film by a subsequent set of rolls.

In this process, the BMG melt is first processed through a cold roll for solidification casting followed by a subsequent set of hot rolls for hot rolling. This twin roll casting method solidifies the BMG melt into a sheet and must be carried out under vacuum or an inert atmosphere. In addition, the thickness of the BMG sheet through twin roll casting is undesirable because it is often not uniform, and typical thickness is less than about 200 [mu] m. Thermoplastic rolling by twin roll casting followed by rolls of sets also requires a very high rolling stress to further deform the thin film and achieve a thinner sheet.

U.S. Patent Publication No. 2014/0064043 to Tsuchiya et al., Which is incorporated herein by reference, discloses a single-roll casting of BMG melt into a sheet followed by casting induced pinholes ) Of the BMG sheet is subjected to super-plastic rolling to produce a clock spring.

Similar to Hoffman, the process proceeds from a cold roll to a hot roll and depends on the solidification of the BMG melt under an inert atmosphere. This causes pinholes on the surface of the BMG sheet when the BMG is solidified with air remaining on or inside the BMG surface. The thickness is also not adjustable (i. E. It is not uniform and typically less than about 200 [mu] m). The superplastic hot rolling step is only designed for smoothing the BMG sheet surface; The sheet can not be deformed due to high hydrostatic stress during hot rolling. As a result, uniaxial thermoplastic stretching is not applied.

U.S. Patent No. 8,613,814 to Kaltenboeck et al., And U.S. Patent Application Publication No. US 2014/0047888 to Johnson et al., Which are hereby incorporated by reference in their entirety, disclose a technique for rapid capacitor discharge ) Technology to rapidly heat and forge bulk metal glass. Although this method can soften BMG very quickly, the thermoplastic or forge stresses for this process are very high due to high isotropic stresses under forging and high strains within a short time scale, and thus the manufacture of large BMG sheets The use of which is limited.

Accordingly, there is a need in the art to provide a method and apparatus for producing bulk metallic glass sheets of any thickness and size, in a controllable manner under realistic conditions (e.g., in air and at realistic feasible pressure) There remains a need for a method of transforming glass.

It is an object of the present invention to produce bulk metallic glass sheets.

It is yet another object of the present invention to produce a bulk metallic glass sheet having a uniform thickness.

It is yet another object of the present invention to produce a large bulk metallic glass sheet under advantageous processing conditions.

It is yet another object of the present invention to produce a bulk metallic glass sheet having a composite pattern.

It is another object of the present invention to produce bulk metallic glass strips.

It is another object of the present invention to connect bulk metal glass sheets by hot rolling.

A further object of the present invention is a system for producing bulk metallic glass sheets and strips.

To this end, in one aspect,

a) preheating the bulk metallic glass feedstock to a temperature sufficient to soften the bulk metallic glass feedstock, but which does not contribute significantly to the spent crystallization time of the bulk metallic glass; And

b) thermo-graphically rolling said preheated bulk metal glass feedstock between a set of heated rollers maintained at the processing temperature of said bulk metal glass

A method for producing a bulk metallic glass sheet,

And reducing the thickness of the bulk metallic glass feedstock to produce a bulk metallic glass sheet.

The present invention also relates generally to a system for producing bulk metallic glass sheets,

a) a set of preheating plates, said set of preheating plates being capable of sandwiching a bulk metallic glass feedstock therebetween, so that the crystallization time of the bulk metallic glass is sufficient to soften the bulk metallic glass feedstock, A preheating plate for preheating the bulk metal glass feedstock to a temperature which does not contribute significantly to the temperature of the preheating plate;

b) a set of rotatable heated rollers held at the working temperature of said bulk metal glass, said heated rollers being capable of moving said bulk metal glass feedstock received from the step of the preheating plate A set of rotatable heated rollers thermoplasticly rolling between heated rollers to thin the bulk metal glass feedstock into bulk metal glass sheets; And

c) a stretching mechanism capable of stretching the rolled bulk metal glass emitted from the set of heated rollers at a controlled rate;

To a system for producing bulk metallic glass sheets.

For a more thorough understanding of the present invention, reference is now made to the following descriptions taken in conjunction with the accompanying drawings,
Figures 1a, 1b, 1c and 1d depict various methods of thinning a metal glass in its supercooled liquid state.
Figure 2 depicts two methods of BMG processing techniques.
Figures 3a and 3b demonstrate the relationship between moldability and processing temperature.
Figures 4a and 4b illustrate the effect of preheating at the maximum strain that can be achieved in a hot rolling process, with negligible stretching force.
Figure 5 depicts the temperature protocol of a single step (conventional) machining protocol with the machining protocol of the present invention.
Figure 6 depicts a time-temperature-transformation diagram for Zr ₄₄ Ti ₁₁ Cu ₁₀ Ni ₁₀ Be ₂₅ BMG.
Figure 7 depicts the maximum dimensions of a rolled Zr ₄₄ Ti ₁₁ Cu ₁₀ Ni ₁₀ Be ₂₅ BMG sheet.
Figure 8 depicts a schematic of a rolling system combined with a stretching method.
Figure 9 depicts a comparison of a rolling force and a stretching force for the same speed (3 mm / s).
Figure 10 depicts a comparison of maximum shear stress and maximum hydrostatic pressure as a function of sheet thickness in thermoplastic rolling.
11A depicts a Zr ₄₄ Ti ₁₁ Cu ₁₀ Ni ₁₀ Be ₂₅ BMG sheet in a rolled state and FIG. 11 depicts a Zr ₄₄ Ti ₁₁ Cu ₁₀ Ni ₁₀ Be ₂₅ BMG sheet after removal of surface oxidation.
Figure 12 depicts a rolling apparatus for a BMG material according to the present invention.
Figure 13 depicts an exploded view of important parts of a rolling device according to the invention.
14 is an example of a preheating plate according to the present invention.
Figure 15 depicts a Pd ₄₃ Ni ₁₀ Cu ₂₇ P ₂₀ sample in the rolled state.
16 shows an example in which a pattern is formed on a BMG sheet in-plane or out-of-plane using a patterned roller.
17 shows an example in which a pattern is formed on a BMG sheet using a thermoplastic compression or blow molding method.
Figure 18 depicts an example of a spectacle frame patterned on a BMG sheet processed according to the present invention.
Figure 19 depicts rolling a sandwich of bulk metallic glass feedstock material to connect (a) or partially (b) sandwich and deform the sandwich of the material.
Also, not all elements are shown in the respective figures, but elements having the same reference numbers all refer to similar or identical parts.

FIELD OF THE INVENTION [0002] The present invention relates generally to methods and apparatus for fabricating large area bulk metal glass sheets and bulk metal glass strips and ribbons by modifying the metal glass under low force and steady conditions. "Sheet" means a wide stretch or surface of bulk metallic glass. "Strip" or "ribbon" means a long, narrow strip of bulk metallic glass. In both cases, the bulk metallic glass sheet or strip is made to have a thickness of less than about 1 mm.

As noted above, in the prior art based on thermoplastic rolling, the rolls are typically cold (~ room temperature), which is much lower than the desired rolling temperature. Thus, when rolling, the BMG is cold and its flow stress rapidly increases. An important aspect of the present invention is to set the opposite case wherein the BMG feedstock temperature is increased when approaching the roll and the amount of increase in temperature is optimized taking into account the consumption of formability prior to contact with the roll. This minimizes the time required to reach the rolling temperature and optimizes the viscosity to allow for large deformation during rolling, which enables separation and laminar flow.

Surprisingly, it has been found difficult to obtain a large and thin BMG sheet using only hot rolling, due to the hydrostatic pressure necessary to achieve realistic shear deformation (where? Is the viscosity, U is the rolling speed and R and h are the Radius and sheet thickness). Since the shear strain depends only on the pressure gradient, the hydrostatic pressure can be considered as loss; The absolute majority of the clamping force hydrostatically squeezes the BMG only hydrostatically without any permanent deformation. For normal size and thickness reduction, the hydrostatic pressure consumes most of the applied force and exceeds the pressure that can be generated by the clamping force that is practically achievable for the hot rolling mill. In short, the thermoplastic rolling can produce a BMG sheet that itself exceeds a size of 20 cm x 20 cm with a thickness of less than about 0.05 cm, even for very few metallic glasses having a practically achievable viscosity of less than 10 ⁷ Pa 揃 s Do not allow it.

The inventors of the present invention have found that the stretching deformation of the BMG is an effective use of the strain applied to all the forces which are necessarily applied to the deformation. However, when only stretching is used, instability (necking) is observed, especially at a large stretching force. As a result, as illustrated in Fig. 1A, the thickness variation is unacceptably high and deteriorates in multi-pass machining.

However, if one or more of hot rolling and drawing under a controlled speed (not force) below a negative temperature gradient is combined, the force to deform the bulk metallic glass is sharply reduced, and a large, thin sheet Can be achieved. In addition, the combination results in high stability, with very little thickness variation of the sheet produced.

Rapid cooling is known to affect the mechanical properties of BMG. However, deformation during solidification is also not reported to affect mechanical properties. The inventors of the present invention have found that by the method described herein, the sample is deformed until solidified. In addition, for the sample stretched during solidification, greater bending ductility is measured relative to the sample that has not been stretched.

The present invention relates generally to methods and systems for producing metallic glass sheets having controllable dimensions. The metal glass is deformed under low force and stable conditions to produce a large-area thin metal glass sheet. The present invention is based on the discovery that thin (i.e., less than about 1 mm, preferably less than about 0.5 mm, and most preferably less than about 0.1 mm thick, depending on the particular BMG) of a large (e.g., at least 20 cm x 40 cm, , And even thinner thickness) metal glass sheets.

The present invention is based on a thermoplastic rolling technique, optionally but preferably combined with stretching deformation. This is based on a combination of one or more of thermoplastic rolling and stretching in combination with the preheating method. The dominant mode of deformation is dependent on BMG conditions such as thickness, viscosity and crystallization time. The process described herein prevents crystallization during the manufacture of sheets having particularly large, thin sheets made from BMG having low moldability, as further described below. Through preheating, the available process time consumed is reduced, which allows the use of thicker feedstock materials. Deformation during hot rolling is used to reduce the thickness to less than that requiring only very limited deformation; The minimum requirement is the smoothing of the perturbation of the thickness.

Thus, in one aspect,

a) preheating the bulk metallic glass feedstock to a temperature sufficient to soften the bulk metallic glass feedstock, but which does not contribute significantly to the spent crystallization time of the bulk metallic glass; And

b) thermo-graphically rolling said preheated bulk metal glass feedstock between a set of heated rollers maintained at the processing temperature of said bulk metal glass

A method for producing a bulk metallic glass sheet,

And reducing the thickness of the bulk metallic glass feedstock to produce a bulk metallic glass sheet.

In a first process step, the metallic glass is 0.8T _g <T _preheating <1.4T _g: is heated to a temperature of (T _g heated glass transition temperature (℃) for the to 20K / min), for a subsequent rolling step Preheat the feedstock BMG. Art preheating phase and reduces the heating time required for rolling, softening the BMG, which roller and the supply BMG effective heat transfer between the raw material and therefore 0.7T _x <T _Processing <1.3T _x (T _x according to: a 20K / min (&Lt; RTI ID = 0.0 &gt; C)) &lt; / RTI &gt; If the sheet is already thin, for example by several passes if the thickness is less than 1 mm, the preheating step becomes less effective (or even omitted). Subsequently, the BMG feedstock was hot rolled at 0.7T _x &lt; T _processing &lt; 1.3T _x .

(여기서, R은 롤러의 반경이고 △h 및 h는 각각 두께 감소 및 필름 두께이다)인 경우에 매우 효과적이지 않게 되는데, 그 이유는, 정수압이 윤활 근사 영역(lubrication approximation region)에서 매우 급속하게 증가하기 때문이다. 통상적으로, 당해 영역에서의 가소성 변형에 대한 압연력의 기여도는 10% 미만이다. 그러나, 열간 압연으로부터의 또 다른 이점은, "네킹"을 일으키는 임의의 동요(최초 두께 변화)이며, 불안정성이 감소할 수 있고, 이는 후속 연신 가공의 안정화를 돕는다.Hot rolling is used to thin the feedstock, but (essentially for a thin sheet)

(Where R is the radius of the roller and h and h are the thickness reduction and the film thickness, respectively), because the hydrostatic pressure increases very rapidly in the lubrication approximation region . Typically, the contribution of the rolling force to plastic deformation in the area is less than 10%. However, another benefit from hot rolling is any fluctuation (initial thickness variation) that causes "necking &quot;, which can reduce instability, which aids stabilization of subsequent stretching.

Upon ejection of the bulk metal glass sheet from a set of heated rollers, the bulk metal glass sheet is optionally, but preferably expediently, stretched. Surprisingly, the stretching force is typically much less than the clamping force required for hot rolling of the metallic glass to achieve the same strain rate. The stretching force is applied to a temperature gradient and the bulk metallic glass sheet moves relative to the temperature gradient. This stabilizes the process and prevents instability that occurs during the associated thinning.

One requirement for stabilizing the stretch is that stretching occurs under velocity controlled conditions rather than force controlled conditions. Thus, all stretching forces are used for tension deformation, while very large hydrostatic pressure must act to achieve a similar deformation rate during hot-rolling. The force applied to make hydrostatic pressure does not thin the feedstock and can be considered a loss. Thus, the stretching force is dramatically smaller during hot rolling, especially for the BMG feedstock than during the post-thinning steps.

As a result, the combined rolling and drawing processes described herein can achieve thin and large BMG sheets. Thus, the use of more effective deformation forces, which would not have been possible with thermoplastic based rolling alone, and the use of a wider range of BMG alloys (i.e. those with a minimum viscosity of even 10 ¹⁰ Pa s As shown in FIG.

Surprisingly, it has been found that the deformation also affects the mechanical properties of BMG by increasing the ratio of bulk modulus through generation of free volume or equivalently above shear modulus. Solidification during stretching results in more ductile BMG than when BMG is simply hot rolled. Thus, even though they become brittle during typical processing conditions, the methods described herein can produce BMG with increased ductility. For example, stretch rolling has been found to increase the bending ductility of a 0.8 mm ribbon of Zr ₄₄ Ti ₁₁ Cu ₁₀ Ni ₁₀ Be ₂₅ bulk metal glass alloy from less than 2% to more than 3%.

The implementation of this method minimizes the consumption of formability prior to the feedstock being contacted with the roll, and the deformation stresses required for thicker feedstocks using the hot rolling process step and through speed controlled stretching in a stabilized temperature gradient ).

Figures 1a, 1b, 1c and 1d illustrate various methods of thinning metal glasses in their supercooled liquid state and in which stretching is achieved through speed control (rather than load control). Figure 1A (Case 1) shows continuous stretching at a uniform temperature, causing overall necking and uneven thickness of the feedstock. FIG. 1B (Case 2) shows the temperature gradient field using only stretching. As shown in Figure IB, the presence of typical surface defects on the BMG feedstock acts as "agitation" during drawing without hot rolling under a temperature gradient. These fluctuations continue to increase during stretching, resulting in localized necking behavior. Figure 1c (Case 3) shows that a very limited strain can be produced by stretching without hot rolling under a temperature gradient to deform BMG feedstock due to very high hydrostatic pressure in hot rolling. Finally, Fig. 1d (case 4) shows that, by the combination of hot rolling and stretching, higher deformation can be achieved with steady-state thermoplastic deformation, which can significantly eliminate fluctuations.

Figure 2 shows two methods of BMG treatment techniques. Route 1 is a liquid casting process that relies on rapid quenching of the liquid melt to form BMG, and Route 2 relies on the thermoplastic formation of BMG in the subcooled liquid state.

For processing BMG sheets based on liquid state treatments, for example twin roll casting, single roll casting, injection molding or pouring of melt melt into baths, All of the techniques of the prior art are carried out by the processing method of route 1. As mentioned above, Route 1 has several major difficulties, including very high temperatures (e.g., above the liquid temperature), fast cooling (narrow processing window) to avoid crystallization, high vacuum or inert atmospheres Demand, very limited control.

On the other hand, there are many advantages in machining a BMG sheet based on the processing method of route 2, which includes a lower temperature and a wider processing window. Further, the route 2 processing technique may be performed in air.

The ability to thermally process BMG is quantified as temperature dependent formability F = t _crist / η. As shown in Figs. 3A and 3B, moldability increases with increasing process temperature. This behavior is surprising and appears to be everywhere among BMGs. A wide range of BMGs have been studied, some of which are described in Pitt, EB, G. Kumar, and J. Schroers, Temperature dependence of the 온도oplastic form 성 in bulk metallic glasses . Journal of Applied Physics, (2011) 110 (4).

This behavior has affected the processing protocols described herein for the practical processing of large, high quality, thin sheets. As a result, in order to maximize the deformation during thermoplastic deformation of the metal glass, a high temperature was selected, as shown in Figure 3a, which shows that the moldability of the metallic glass is a function of both the crystallization time and the viscosity, which are all powerful functions of temperature . Surprisingly, for all BMG considered, moldability increased with increasing process temperature. However, with increasing temperature, the crystallization time decreased. Therefore, in order to roll a large sheet, efforts must be made to approach high temperatures while avoiding crystallization. Experimentally implementing such a high forming state can be very challenging.

To solve this problem, the present invention uses a processing protocol that optimizes the pre-rolling condition. The moldability is low, but the BMG feedstock is soft enough to allow rapid heating to the rolling temperature (i. E., The processing temperature within a certain temperature range) and optionally, but preferably, the stretch strain is used as the main deformation process. Stretching deformation requires much lower force than deformation during hot rolling, and therefore, it can deform at lower temperatures and preserve moldability.

The preheating of the BMG feedstock is an effective first treatment step of the process described herein which results in a larger possible variation generally obtainable by prior art processes. The effect of preheating on the maximum deformation attainable during hot rolling with a slight draw roll force (lateral sheet size) is schematically illustrated in Figures 4a and 4b.

Figure 4a shows the maximum deformation that can be achieved during hot rolling without using any preheating. As shown in Figure 4a, without preheating of the BMG feedstock, it is only slowly heated to the desired rolling temperature, which results in slow deformation of the BMG feedstock during the time the moldability is consumed.

On the other hand, as shown in FIG. 4B, when the BMG feedstock is _preheated from T _preheating to T _rolling , there is a faster deformation of the BMG that preserves moldability, which allows processing of larger, thin BMG sheets . The preheating step softens the BMG sufficiently to allow the roller to adhere tightly to the BMG, thus allowing the BMG to heat up more rapidly.

In sex highest forming BMG, rolling behavior (rolling operation) ~ f = 10 -4 Pa - 1 may be actually implemented. This corresponds to a treatment time of approximately 1 minute at a viscosity of 10 ⁶ Pa · s. In a typical thermoplastic processing protocol, the feedstock is heated to the treatment temperature. This process consumes approximately one minute. However, as shown in Fig. 5, only a part contributes to the moldability consumption. This corresponds to a set temperature T _set ± 10% close to the set temperature. Only a small fraction should be considered because the crystallization time decreases rapidly with increasing temperature and the heating rate decreases as it approaches the set temperature. The heating rate is proportional to the difference between the feedstock temperature and the set temperature. In contrast, in the present invention, instead of direct heating to an ideal rolling temperature, the BMG feedstock is first preheated to a generally lower temperature. The crystallization time becomes longer, and therefore, a remarkably small portion of the moldability is consumed as shown in Figs. 3A and 3B.

As shown in Fig. 5, the consumption of moldability during heating can be drastically reduced due to the two-step process used in the present invention. In the current process, the heating rate decreases when approaching T _preheating (with minimal formability consumption) and increases in the temperature range where significant formability is consumed by the different heating mechanisms from T _preheating to T _rolling .

The present invention has advantages over the exponential dependence of crystallization time and temperature. The feedstock is heated to a BMG (a, T _g that is, the crystallization times a day or more in order) the crystallization time is very long temperature. However, in terms of temperature, this temperature is close to the processing temperature. Thus, the temperature of the preheated feedstock to achieve the treatment temperature has to increase only a few tens of degrees through the set of heated rollers, which can be achieved by putting the preheated feedstock BMG into a set of heated rollers. Thereafter, cooling may be achieved by natural convection of the treatment environment, or by the addition of gas or liquid to the discharged sheet. Thus, the use of the pre-heating step results in only a small total deformation and can also cause damage to the roller. Thus, the bulk metal glass is preheated to a temperature that can be maintained for an extended period of time, in one embodiment at least 5 times, preferably at least 10 times, compared to the time available at the processing temperature. In other words, the bulk metal glass feedstock is preheated to a temperature that is sufficient to soften the bulk metal glass feedstock, but does not significantly contribute to the spent crystallization time of the bulk metal glass. At the same time, this preheat temperature is close to the rolling temperature in terms of temperature, and the BMG feedstock is soft enough to allow smooth thermoplastic deformation.

FIG. 6 shows a time-temperature-transition diagram of Zr ₄₄ Ti ₁₁ Cu ₁₀ Ni ₁₀ Be ₂₅ BMG. As shown in Fig. 6, the crystallization time decreases rapidly with increasing temperature.

Figure 7 shows a Zr ₄₄ Ti ₁₁ Cu ₁₀ Ni ₁₀ Be ₂₅ BMG sheet that has been rolled at different temperatures. The initial feedstock is all 1.7 mm thick, 14 mm diameter discs. The number of passes before crystallization is shown. As shown in FIG. 7, using Zr ₄₄ Ti ₁₁ Cu ₁₀ Ni ₁₀ Be ₂₅ BMG, it was determined that the highest treatment temperature was 440 ° C in order to obtain the highest thickness reduction possible from the viewpoint of rolling and the thinnest possible sample.

Generally, the rolling is carried out with several passes, which may range from 3 to 15 passes. At 440 [deg.] C, Zr ₄₄ Ti ₁₁ Cu ₁₀ Ni ₁₀ Be ₂₅ BMG before crystallization represents a 5-6 minute treatment window. During the single stage heating process, ~ 25 seconds were consumed in each pass during a total of 5-6 minutes at 440 ° C. Actual rolling (feedstock and roller contact) depends, for example, on sheet length, roller radius, rolling speed, and for typical BMG rolling, the actual rolling takes about 10 seconds. Thus, rolling through 10 passes consumes approximately 6 minutes of processing time, which means that the BMG sample has already begun to crystallize. Therefore, only about 9 passes are the maximum prior to BMG sample crystallization. If a non-ideal low processing temperature, for example 420 DEG C, is selected, a processing time of 8 minutes is available, and thus more than 10 passes can be performed prior to crystallization. However, because of the significantly increased viscosity at these low temperatures, the strain achieved is low. Other temperatures are also shown in FIG.

In the present invention, the preheating temperature is high but is optimized to a temperature low enough not to contribute significantly to the spent crystallization time. Since the temperature is close to the processing / rolling temperature, the temperature can be quickly raised to the processing temperature.

The reason for this rapid heating in this processing step is as follows:

(1) the temperature is already close to the processing temperature, typically > T _rolling - from about 20% to about 35%, more preferably about 30%.

(2) Since the preheated softness of the BMG feedstock results in close contact of the entire contact line, rapid thermal transfer can be achieved.

For example, when BMG is preheated at 390 ° C rolled and then rolled at 440 ° C, the crystallization takes place after 35 minutes, which is much longer than the crystallization time scale at 440 ° C for 5 to 6 minutes, without the preheating step. Thus, the consumption of formability can be drastically reduced during heating to the pre-heating temperature and consumed during the rolling step. For example, by using the method described herein, the BMG feedstock can be rolled down to about 16 passes or less before crystallization compared to about 10 passes for a single step process.

As described herein, it has been found that the force required to reach the desired thickness reduction by thermoplastic rolling is dramatically higher, especially for sheet-like dimensions (i.e., when the out-of-plane dimension is much smaller than in-plane dimensions). However, when the stretching step is added as shown in Fig. 8, the sheet thickness after being discharged from the first set of rollers can be further reduced because of the stretching force, F. Fig.

The stretching force may be, for example, (1) a " cold "roller of a second pair that rotates at a higher speed than the first set of heated rollers to produce an elongating force Or (2) a rate-controlled pulling mechanism, which is maintained at a temperature lower than the processing temperature of the die. Other methods of applying the stretching force to bulk metal glasses, such as those discharged from a first set of heated rollers, are also known to those of ordinary skill in the art. What is important for the stretching is the controlled velocity and the negative temperature gradient.

The stretching force is calculated according to? = F / (h * W) (where W is the width of the sheet). The stress in the stretched portion is proportional to 1 / h. This means that the driving stress is increased until the sheet is broken, because the thickness of the rolled sheet is reduced. Surprisingly, however, it has been found that changes in the feedstock thickness can be reduced before stretching to withstand BMGs that grow in some unstable manner in some thickness variations.

The requirements for stabilizing the combination of compression and stretch rolling are as follows:

(1) Negative temperature gradient as the BMG sheet is discharged from the first set of heated rollers. As a result, the distance from the first set of heated rollers increases, the speed increases, and therefore the deformation resistance increases.

(2) Stretching is realized by precisely adjusting the displacement. That is, stretching is not force control but speed control. Typically, the velocity is at least substantially constant.

(3) Thickness changes occurring during stretching can be flattened by subsequent rolling passes.

Figure 8 shows a schematic of a rolling system in combination with a stretching method wherein a second set of "cooling" rollers are used to control the stretching of the rolled sheet to make the rolled sheet thinner.

The deformation mechanisms for thermoplastic rolling and stretching are different. In the case of thermoplastic rolling, the thickness reduction is derived from shear deformation (similar to squeezing flow), whereas in the case of stretching, the thickness reduction is derived from the tensile strain.

To quantify the desired mode of deformation for different BMG processing conditions, such as thickness, speed and crystallization time, the thermoplastic rolling and stretching forces can be calculated.

)는 1 보다 훨씬 작기 때문에, 비중 및 관성 항목과 같은 본체 힘은 무시될 수 있다.In the following calculations, the problem is simplified to a 2D problem. That is, it is assumed that BMG is considered as an incompressible Newtonian fluid in the case of a BMG deformed in a supercooled liquid zone, where the thickness of the sheet is much smaller than its other dimensions. In fact,

) Is much smaller than 1, body forces such as specific gravity and inertia items can be ignored.

(1)Based on this, the pressure at rolling can be measured using a no-slip boundary condition as shown in equation (1).

(One)

Where h is the viscosity, U is the rolling speed, x is the rolling direction, h _m , R, h ₁ are the spacing between the rollers, the radius of the rollers, and the sheet thickness at the time of discharge.

The rolling force can then be calculated according to equation (2).

(2)

(2)

The stretching force can be estimated according to equation (3).

(3)

(3)

Here, w is the width of the sheet, △ U is the speed difference between the two ends of the sheet, L ₀ is the length of the thickness reduction takes place.

To compare the rolling forces and stretching force, △ h / h ₀ = 40% is used as an example and the roller gap is half of the initial sheet thickness and w = 10 cm,? = 10 ⁶ Pa.s, U = 3 mm / s,? U = U, L ₀ = 1 cm, These are suitable for actual control, for example, high temperatures are presumed to need to be cooled to stabilize the strain. In one embodiment, the strain of thermoplastic rolling and stretching to the same strain achieved during the deformation time is at least 10 times different.

The results showed in Fig. 9, which compares the rolling force and a stretching force to the same speed (3mm / s), where the reduced thickness △ h / h ₀ = 40%, the roller gap is half the initial sheet thickness, the sheet width = 10 cm and the viscosity = 10 ⁶ Pa.s. Surprisingly, the force required to achieve the same rate and thickness reduction rate during stretching is much lower than during rolling. Thus, in order to achieve a sheet of 0.5 mm thickness, the rolling force is approximately 1000 times greater than the elongation force.

Based on equation (3), it is clear that for all thermoplastic rolls all shear forces are used for plastic deformation whereas shear stresses are used rather than hydrostatic pressure which contributes to plastic deformation. The maximum shear stress and maximum hydrostatic pressure are compared to the same rolling parameters as in FIG. 9 as a function of thickness as shown in FIG. As shown in Fig. 10, the maximum hydrostatic force increases very rapidly as the sheet thickness decreases. In addition, the maximum hydrostatic force is always much greater than the maximum shear stress, which means that by thermoplastic rolling, thinner sheets become less and less efficient as sheets become thinner (15).

One of the main advantages of the present invention is that the sheet can be produced at ambient temperature. In contrast, most alternative methods previously proposed for producing sheet-type BMG parts including methods such as casting, biaxial-rolling casting and alloy melt forming require an unconventional vacuum or inert gas or reducing environment in the manufacturing environment do. Obviously, most BMGs are oxidized during the proposed temperature and processing conditions. Surprisingly, however, oxidation has been found to be superficial and limited to the surface of the sheet. The oxide layer only stays at the top (thin) depth (1-2 탆) of the surface. 11A shows a rolled Zr ₄₄ Ti ₁₁ Cu ₁₀ Ni ₁₀ Be ₂₅ BMG sheet having a thickness of ~ 450 μm (T _rolling for 13 passes = 440 ° C., T _preheat = 420 ° C.). 11B shows this same BMG sheet after removing 1-2 micron surfaces.

로서 계산될 수 있고, 여기서 ρ, η 및 h는 각각 공급원료의 밀도, 점도 및 두께이고, U는 압연 속도이다. 본 발명에서 층류의 요건은 다음 조건을 포함한다: 10㎛ 내지 20mm의 압연 두께, 점도: 10³~10¹⁰ Pa.s, 밀도: 3~20 g/cm³, 압연 속도: 1-200cm/min, 이들 모두는 Re=10^-13-10^-3<<1을 수득한다.However, the present inventors have found that laminar flow is necessary for limiting the oxide on the surface of BMG sheet. Therefore, the present invention is limited to processing conditions that cause laminar flow and avoid turbulence. The conditions for this flow can be defined by the Reynolds number, where Reynolds number considerably smaller than 1 is needed to effect laminar flow. For the rolling process, the Reynolds number is

Where ρ, η and h are the density, viscosity and thickness of the feedstock, respectively, and U is the rolling speed. The requirements of laminar flow in the present invention include the following conditions: a rolling thickness of 10 to 20 mm, a viscosity of 10 ³ to 10 ¹⁰ Pa.s, a density of 3 to 20 g / cm ³ , a rolling speed of 1 to 200 cm / min , All of them yield Re = 10 ^-13 -10 ^-3 << 1.

The BMGs that can be processed in accordance with the present invention can be formally separated into four groups, even if they are included in a continuum as shown in Table 1.

[Table 1]

Class of BMG

The need for stretching depends to some extent on the final BMG sheet of the desired size as well as on a particular class of BMG.

BMG having excellent moldability exhibits a viscosity of 10 ⁶ Pa · s at T _x . Their formability is greater than or equal to 10 ^-4 Pa ^-1 . Preheating is still required during the initial stage of rolling for thicker feedstocks (> 3 mm). Often, for such BMG classes, longer processing times are available and more easily avoid crystallization since the processing temperature can be chosen to be lower. Stretching is only required for larger sheets (i.e., having dimensions of about 40 cm by about 20 cm or more).

The BMG of the solid formation shows a viscosity of 10 ⁶ to 10 ⁷ Pa · s or less at T _x . Their formability is about 10 ^-4 to 10 ^-5 . Preheating is still required during the initial stage of rolling for thicker feedstocks (> 3 mm). Stretching is required for large and medium sheets (i.e., having dimensions of about 20 cm by about 10 cm).

The intermediate formability of BMG alloys requires stretching for most geometries. At a clamping force of 30 kN, the final size that can be achieved with these alloys is significantly different from that for the high-build BMG. The large sheet can only be achieved through stretching. BMG sheets having dimensions of about 20 cm by about 10 cm are possible using the techniques described herein.

The low-build-up BMG alloy has a viscosity of 10 ⁹ Pa · s at T _x (F <10 ^-6 Pa ^-1 ), has poor formation and is slightly deformed during rolling. Thus, most of the strain must occur during stretching. The pre-formed thin plate may still be thin if it includes stretching. BMG sheets having dimensions of about 20 cm x about 3 cm are possible using the techniques described herein.

However, in all cases where the BMG feedstock has a thickness of > 3 mm, it is necessary to preheat the feedstock feed prior to rolling. In the feedstock dimensions, for example, after several passes through which the feedstock is sheet-type <1 mm thick, heating through the rollers may be sufficient and no preheating is required.

Another key aspect of the present invention is precise temperature and process time control. Accurate temperature control can be achieved by controlling the temperature of the heating element. For example, thermocouple feedback can be placed inside a set of heated rollers and used to adjust the temperature of the heating cartridge within a set of heated rollers. Alternatively, temperature control can also be achieved using radiant heat from outside the set of heated rollers. The rollers can also be heated by immersion in heated liquids. Other temperature control means that allow precise temperature control are also known to those skilled in the art and are usable in the present invention.

As described in Figures 12 and 13, in one embodiment, the rollers are heated to a resistance heater controlled via PID-regulation, wherein a thermocouple placed close to the surface of the roller is used to measure the temperature. It is highly desirable for temperature uniformity on the roller surface to deviate to less than 5 ° C through the entire roller.

As described above, the preheater is a major element of the present invention because it reduces moldability consumption of BMG. The requirement for the preheater is that the BMG raw material is sufficiently softened that the BMG is suitable for the roller shape without damaging the rollers and also minimizes the moldability consumption.

In one embodiment, as shown in FIG. 11, the preheater may include two heating plates (upper and lower) that heat the stock as it passes through the preheat stage. Temperature control during preheating is important, but not important during rolling. The preheater optionally, but preferably, has a heating and conditioning mechanism independent of that of the rollers. The technique of heating and conditioning the preheater may be similar to that proposed for the rollers.

The preheater shown in Fig. 11 enables temperature control within ± 5 ° C. In this example, the two heating plates simply press the raw material by gravity. However, depending on the specific characteristics of the BMG in the class and the geometry of the BMG material, as well as a particular class of BMG, additional forces may be added. This force can be adjusted high or low as needed.

As the transverse sheet dimension increases, the tendency of the BMG to adhere to the rollers can become problematic. The adhesion of the BMG to the rollers should be addressed to maintain the continuity formability during planarity, thermal conductivity and overall rolling process. The tendency of the raw materials adhering to the rollers can be quantified by comparing the driving force that is adhered to each other due to the system energy reduction caused by the adhering force and the resistance due to the increase in strain energy caused by the bending. In the case of Newtonian fluids, the increase in flexural energy due to adhesion is given in equation (4): &lt; EMI ID =

(4)

(4)

Here, λ = 3η has a tensile viscosity of the sheet, Ω is the angular velocity of the roller, I = h ₂ ^3/12 is a cross-sectional moment of inertia.

On the other hand, the bond energy of the system is shown in equation (5): &lt; EMI ID =

(5)

(5)

Here,? Is the contact angle between the metal glass and the roller.

(6) 또는

(7)을 필요로 한다.Therefore, in order to prevent adhesion during rolling,

(6) or

(7).

This adhesion tendency is not observed for other metals and is believed to occur in the BMG due to the low viscosity or corresponding flow stress accessible to the BMG and consequently the intimate contact between the roller and the BMG raw material. Therefore, in order to reduce the adhesion during hot rolling, the adhesion energy must be lowered.

The present invention proposes the following strategy for reducing the sticking tendency of the BMG raw material to the rollers:

(1) Decrease in fine surface area - It has been observed that the adhesion tendency is reduced by a very high surface finish. Thus, in an attempt to reduce the sticking tendency, the roughness was lowered. First, although adhesion tends to deteriorate, a decrease in adhesion is observed below the roughness compared with the mirror finish.

(2) Surface chemistry - When selecting a roller material that is poorly wetted by BMG. What this means is that the wetting angle,? In equation (7) is greater than 90 degrees (equation (7) always holds). For example, nitride and other ceramic roller surfaces reduce adhesion (increase wetting angle) and metal roller surfaces promote adhesion.

(3) Surface chemistry is the oxidation of BMG feedstock. The oxidized surface of the BMG feedstock also reduces adhesion. For example, Pt _57.5 Cu _14.7 Ni _5.3 P _22.5 BMG having the lowest oxidation tendency mostly adheres to the roller, whereas Pd ₄₃ Ni ₁₀ Cu ₂₇ P ₂₀ BMG is significantly less sticky, and the optimum sticking tendency is described in FIG. 15 As shown, this occurs with the tested Zr ₄₄ Ti ₁₁ Cu ₁₀ Ni ₁₀ Be ₂₅ BMG alloy.

(4) Another way to prevent adhesion of BMG is to reduce the surface energy of BMG (gamma _lv in equation (7)) by adding a lubricant.

Figure 15 is a rolled _{Pt 57 .5 Cu 14 .7 Ni 5} .3 P 22 .5 shows a photo of the sample. As shown in FIG. 15, the Pd ₄₃ Ni ₁₀ Cu ₂₇ P ₂₀ sample may simultaneously adhere to the upper and lower rollers to cause tearing along the centerline.

The process described herein enables the production of a super smooth sheet of bulk metal glass with a low oxidation rate.

In addition, where the BMG is made of a giant thin sheet, other processing steps may be performed to form the BMG sheet into a more complex design shape.

For example, FIG. 16 shows an example of creating a pattern in a BMG sheet in-plane or out-of-plane using a patterned roller. As shown in Figure 16, after processing the BMG through a pre-heating step and rolling through a set of heated rollers and then performing the drawing step as described in detail above, the BMG is placed on top of the BMG sheet Can be processed through a subsequent set of heated rollers with in-plane or out-of-plane patterns. The set of patterned rollers maintains the same or different processing temperature as the first set of heated rollers to provide the pattern to the BMG sheet either in-plane or out-of-plane.

These same patterns can also be produced using a thermoplastic compression or blow molding process as described in Fig. In a similar manner, after the BMG is processed through a pre-heating step and rolled through a set of heated rollers, and after performing the stretching step, the BMG is subjected to a compression molding or blow molding process as is generally known in the art can do. Examples of these techniques are described, for example, in U.S. Patent No. 8,641,839 to Schroers et al. And U.S. Patent Application Publication No. 2013/0306262 to Schroer et al., Each of which is incorporated herein by reference in its entirety It is used as a reference.

Further, the forming step can be performed to mold the bulk metallic glass sheet into a mold cavity. If desired, the shearing step may be performed to cut the bulk metallic glass sheet into the contour set by the mold cavity. In another preferred embodiment, the deforming step can be performed to corrugate the bulk metal glass sheet out of the plane deformation set by the mold cavity.

By using these methods as well as other similar patterning methods for BMG, highly complex shapes such as the spectacle frames described in Figure 18 can be made using the methods described herein.

In another preferred embodiment of the present invention, the bulk metallic glass raw material may comprise a plurality of bulk metallic glass pieces connected in step b). As shown in FIG. 19, a plurality of bulk metallic glass pieces forming a "sandwich" can be connected by rolling. This connection step can be complete, wherein a plurality of pieces of bulk metal glass are completely connected together without any gap. Alternatively, the connection position can be adjusted to prevent a piece of bulk metallic glass from connecting at a particular location, whereby only a portion of the bulk of the bulk metallic glass is connected. In this manner, in one embodiment, various materials, such as salts and polymers, can be interspersed within the bulk of the bulk metal glass to prevent the connection of bulk metal glass pieces at specific locations. Other methods that can prevent the connection of the material in a particular region such that only a portion of the bulk of the bull metallic glass is connected can be used in the practice of the present invention.

The present invention also relates generally to a system for producing bulk metallic glass sheets,

a) a set of preheating plates, said set of preheating plates being capable of sandwiching a bulk metallic glass feedstock therebetween so as to be sufficient to soften said bulk metallic glass feedstock, but at the consumed crystallization time of said bulk metallic glass A set of preheating plates for preheating the bulk metallic glass feedstock to a temperature that does not contribute significantly;

b) a set of rotatable heated rollers held at the processing temperature of the bulk metal glass, wherein as the set of heated rollers rotates, the heated rollers heat the bulk metal glass feedstock received from the stage of the preheating plate A set of rotatable heated rollers that thermally roll between the rollers to thin the bulk metal glass feedstock into a bulk metallic glass sheet; And

c) a stretching mechanism capable of stretching the rolled bulk metal glass emitted from the set of heated rollers at a controlled rate;

To a system for producing bulk metallic glass sheets.

As discussed above, the elongating mechanism moves relative to a negative temperature gradient, when the bulk metal glass is stretched or stretched from a set of heated rollers, it is cooled to a temperature below the processing temperature of the BMG.

In one embodiment, the elongating mechanism comprises a velocity controlled pulling mechanism, wherein the velocity controlled tensioning mechanism is configured to tension the bulk metallic glass sheet when released from the set of heated rollers, . This stretching mechanism preferably stretches the bulk metallic glass sheet at a faster rate than the bulk metallic glass travels through the set of heated rollers.

In another aspect, the elongating mechanism comprises a set of rotatable chill rollers. In this aspect, the set of rotatable chill rollers is maintained at a lower temperature than the set of heated rollers and receives a bulk metallic glass sheet therebetween as it is discharged from the set of heated rollers. The set of chilled rollers also preferably rotate at a faster rate than the set of heated rollers.

As also discussed above, after the rolling and drawing step, the system of the present invention also includes a set of rotatable patterned rollers that imparts a pattern onto the bulk metallic glass sheet after ejecting the stretching mechanism . Alternatively, after the rolling and drawing steps, various molding processes can be performed to impart a pattern onto the bulk metallic glass sheet.

In one aspect, the system of the present invention may comprise a number of systems connected in series to continuously produce a thin bulk metallic glass sheet. For example, the system may include a plurality of stations of a set of at least one additional heated roller and a set of at least one additional cooling roller, wherein the bulk metallic glass is further thinned. If desired, a set of preheater plates may be placed prior to the set of at least one additional heated roller. However, the preheater plate may not be required between every station if the bulk metal glass sheet remains at a sufficient temperature during rolling between the set of heated rollers. As discussed above, the "cooling" roller is only cooling to the processing temperature maintained by the set of heated rollers. If the bulk metal glass sheet is not significantly cooled between subsequent subsequent stations, an additional preheater step may not be required. Thus, the optimal arrangement of a set of preheater plates, a set of heated rollers and a set of cooling rollers in the system can be determined by those skilled in the art.

The set of heated rollers may optionally include a surface coating that provides a smooth non-tacky surface thereon. Other methods of protecting the bulk metal glass from adhesion to the heated roller have been discussed above. In addition, the set of heated rollers preferably comprises a hard metal strong enough at the processing temperature of the bulk metal glass.

The set of chilled rollers may have a rough surface such that when the set of chilled rollers emits the set of heated rollers, it holds the bulk metallic glass sheet.

Figures 12 and 13 show views of a set of preheater plates and heated rollers according to the present invention. As shown in Figures 12 and 13, preheater plates 2 and 4 are arranged to receive bulk metallic glass feedstock material. As discussed above, the preheater plate can be sandwiched using gravity alone to bulk metal glass feedstock material, or, optionally, additional pressure providing means can be used between the preheater plate and the bulk metal glass feedstock material More intimate contact can be provided.

The servo motor 6 regulates the rotation of the set of heated rollers 8 and 10. The loading and draining sensor 12 can be used to provide feedback on the position of the rollers. A set of jackscrews can be used to adjust the gap between the set of heated rollers 8 and 10 based on the information received from the load and drain sensor 12.

Figure 13 shows a view of an exploded view of the major parts of the rollers 8 and 10. 13, the cartridge heater 16 is placed along the length of the rollers 8 and 10 along a thermocouple 18. The preheater plates 2 and 4 each also have a cartridge heater 20 and a thermocouple passing therethrough.

Fig. 14 shows an example of the preheating plates 2 and 4 according to the invention. The measurement tape is in inches.

As described herein, the present invention permits the production of long, thin bulk metallic glass sheets having a uniform thickness. In addition, the present invention allows the production of bulk metal glass strips having a uniform thickness. The present invention also allows the further production of complex patterns in bulk metal glass sheets. In addition, the present invention allows continuous production of any complex shape. Finally, the present invention also allows the connection of bulk metal glasses of the same or different types by hot rolling. Other uses of the present invention for making bulk metallic glass sheets with desired features, structures, thicknesses and arrangements will also be known to those skilled in the art and are within the scope of the present invention.

It is also to be understood that the following claims are intended to cover all of the general features and specific features of the invention as described herein and all technical content of the scope of the invention as may arise as a matter of language.

Claims (46)

a) preheating the bulk metallic glass feedstock to a temperature sufficient to soften the bulk metallic glass feedstock, but which does not contribute significantly to the spent crystallization time of the bulk metallic glass; And
b) thermo-graphically rolling said preheated bulk metal glass feedstock between a set of heated rollers maintained at the processing temperature of said bulk metal glass
A method for producing a bulk metallic glass sheet,
Wherein the bulk metal glass feedstock is reduced in thickness to produce a bulk metal glass sheet. The method of claim 1, further comprising: c) after the bulk metallic glass sheet is discharged from the set of heated rollers, stretching the bulk metallic glass sheet. The method of claim 1 wherein from about 0.8 times to 1.4 times of the method (℃) glass transition temperature (T _g) is the measurement of the pre-heating temperature of the bulk metallic glass feedstock. The process according to claim 1, wherein the processing temperature of the bulk metallic glass in step b) is within a supercooled liquid region of the bulk metallic glass. 3. The method of claim 2, wherein the stretching occurs at a negative temperature gradient. 3. The method of claim 2 wherein stretching occurs at a controlled rate. 3. The method of claim 2, wherein steps a) to c) are repeated to obtain the desired thickness of the metallic glass sheet. The method of claim 1, wherein steps a) and b) are performed in air. 3. The process according to claim 2, wherein steps a) to c) are carried out in air. The method of claim 1, wherein the bulk metallic glass feedstock has a viscosity eta _min of greater than about 10 ⁹ Pa · s. 11. The method of claim 10, wherein the bulk metal glass feedstock has a viscosity eta _min of greater than about 10 &lt; ⁷ &gt; 3. The method of claim 2 wherein the thermoplastic rolling step reduces the thickness perturbation that can increase in size during subsequent stretching steps. 3. The process according to claim 2, wherein the processing conditions during steps a) to c) are such that the Reynolds number of the bulk metal glass is maintained at R < ^10-3 . 3. The method of claim 2, wherein the mechanical properties are improved through deformation to produce a free volume during the stretching, wherein the bulk metal glass is changed from a brittle behavior to a ductile behavior. The method of claim 1, wherein the bulk metallic glass feedstock comprises a plurality of bulk metallic glass pieces, wherein the plurality of bulk metallic glass pieces are connected in step b). 16. The method of claim 15, wherein the connecting position is adjusted, wherein only a portion of the bulk of the bull metallic glass is connected. 3. The method of claim 2 wherein stretch rolling increases bending ductility of the bulk metal glass sheet. 3. The method of claim 2, further comprising the step of imparting a pattern to the bulk metallic glass sheet after step c). 19. The method of claim 18, wherein the pattern is imparted to the bulk metallic glass sheet by rolling the bulk metallic glass sheet through a set of patterned rollers, wherein the set of patterned rollers is processed Wherein the rollers impart a pattern on the bulk metallic glass sheet. 19. The method of claim 18, wherein after step c) a shaping step is performed to impart a pattern on the bulk metallic glass sheet. 19. The method of claim 18, wherein after step c) a forming step is performed to form the bulk metallic glass sheet into a mold cavity. 22. The method of claim 21, wherein a shear step is performed to cut the bulk metallic glass sheet into a contour defined by the mold cavity. 22. The method of claim 21, wherein the deforming step is performed to crease the bulk metallic glass sheet into an out-of-plane deformation defined by the mold cavity. 19. The method of claim 18, wherein the pattern has a length scale of less than 1 mm. 25. The method of claim 24, wherein the pattern has a length scale of less than 0.5 mm. 19. The method of claim 18, wherein the pattern comprises a mold cavity. A method of deforming a bulk metallic glass, the method comprising: providing a bulk metallic glass feedstock having a thickness of less than 0.5 mm,
a) thermo-graphically rolling the preheated bulk metallic glass feedstock between a set of heated rollers maintained at the processing temperature of said bulk metallic glass
Wherein the bulk metallic glass feedstock is reduced in thickness to produce a bulk metallic glass sheet. 28. The method of claim 27, further comprising: b) stretching the bulk metallic glass sheet after it has been discharged from the set of heated rollers. A method of deformation of bulk metallic glass, said bulk metallic glass having a minimum viscosity eta _min less than 10 &lt; ⁷ &gt; Pa &
a) preheating to a temperature of about 60 to 100% of the processing temperature; And
b) thermoplasticly rolling said preheated bulk metal glass feedstock between a set of heated rollers maintained at the working temperature of said bulk metal glass
Wherein the bulk metallic glass feedstock is reduced in thickness to produce a bulk metallic glass sheet. A patterned sheet having a length scale of less than 1 mm in a pattern prepared according to the method of claim 1. A casing for an electronic device formed by the method of claim 18. A system for making a bulk metallic glass sheet,
a) a set of preheating plates, said set of preheating plates being capable of sandwiching a bulk metallic glass feedstock therebetween, so that the crystallization time of the bulk metallic glass is sufficient to soften the bulk metallic glass feedstock, A preheating plate for preheating the bulk metal glass feedstock to a temperature which does not contribute significantly to the temperature of the preheating plate;
b) a set of rotatable heated rollers held at the processing temperature of the bulk metal glass, wherein as the set of heated rollers rotates, the heated rollers heat the bulk metal glass feedstock received from the stage of the preheating plate A set of rotatable heated rollers that thermally roll between the rollers to thin the bulk metal glass feedstock into a bulk metallic glass sheet; And
c) a stretching mechanism capable of stretching the rolled bulk metal glass sheet discharged from the set of heated rollers at a controlled rate;
&Lt; / RTI &gt; 33. The system of claim 32, wherein the elongating mechanism moves along a negative temperature gradient. 33. The system of claim 32, wherein the elongating mechanism is controlled by velocity as it is ejected from the set of heated rollers. 35. The system of claim 34, wherein the elongating mechanism stretches the bulk metallic glass sheet at a rate that is greater than the rate at which the bulk metallic glass travels through the set of heated rollers. 35. The method of claim 34, wherein the stretching mechanism comprises a set of rotatable chill rollers, wherein the set of rotatable chill rollers is maintained at a temperature lower than the set of heated rollers, And the bulk metallic glass sheet is received between the rotatable cooling rollers as it is discharged from the set of rollers. 35. The apparatus of claim 34, wherein the elongating mechanism comprises a clamping device, the clamping device receiving the bulk metallic glass sheet between the clamping devices as the bulk metallic glass sheet is released from the set of heated rollers, system. 37. The system of claim 36, wherein the set of chilled rollers rotate at a faster rate than the set of heated rollers. 33. The method of claim 32, wherein the system further comprises a set of rotatable patterned rollers, wherein the patterned roller is pressed against the bulk metallic glass sheet after the bulk metallic glass sheet is discharged from the stretching mechanism To the pattern. 40. The system of claim 39, wherein the set of patterned rollers is maintained at a processing temperature of the bulk metal glass. 33. The system of claim 32, wherein a plurality of systems are connected in series so that a thin film bulk metal glass sheet can be obtained. 33. The system of claim 32, wherein the set of heated rollers comprises a top coating on top providing a smooth, non-viscous surface. 33. The system of claim 32, wherein the set of heated rollers comprises a hard metal and the hard metal is sufficiently strong at the processing temperature of the bulk metal glass. 33. The system of claim 32, wherein the steps are performed in air. 33. The system of claim 32, wherein the system comprises a set of one or more additional heated rollers and a set of one or more additional cooling rollers, wherein the bulk metallic glass is further thinned. 46. The system of claim 45, comprising a set of preheating plates positioned prior to the set of one or more additional heated rollers.

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