Patent Application
20180119259
The present invention generally relates to shaping metallic glass-based sheet material.
Metallic glasses, also known as amorphous alloys, embody a relatively new class of materials that is receiving much interest from the engineering and design communities. Metallic glasses are characterized by their disordered atomic-scale structure in spite of their metallic constituent elements—i.e. whereas conventional metallic materials typically possess a highly ordered atomic structure, metallic glass materials are characterized by their disordered atomic structure. Notably, metallic glasses typically possess a number of useful material properties that can allow them to be implemented as highly effective engineering materials. For example, metallic glasses are generally much harder than conventional metals, and are generally tougher than ceramic materials. They are also relatively corrosion resistant, and, unlike conventional glass, they can have good electrical conductivity. Importantly, the manufacture of metallic glass materials lends itself to relatively easy processing in certain respects. For example, the manufacture of a metallic glass can be compatible with an injection molding process.
Nonetheless, the manufacture of metallic glasses presents challenges that limit their viability as engineering materials. In particular, metallic glasses are typically formed by raising a metallic alloy above its melting temperature, and rapidly cooling the melt to solidify it in a way such that its crystallization is avoided, thereby forming the metallic glass. The first metallic glasses required extraordinary cooling rates, e.g. on the order of 106 K/s, and were thereby limited in the thickness with which they could be formed. Indeed, because of this limitation in thickness, metallic glasses were initially limited to applications that involved coatings. Since then, however, particular alloy compositions that are more resistant to crystallization have been developed, which can thereby form metallic glasses at much lower cooling rates, and can therefore be made to be much thicker (e.g. greater than 1 mm). These metallic glass compositions that can be made to be thicker are known as ‘bulk metallic glasses’ (“BMGs”).
In addition to the development of BMGs, ‘bulk metallic glass matrix composites’ (BMGMCs) have also been developed. BMGMCs are characterized in that they possess the amorphous structure of BMGs, but they also include crystalline phases of material within the matrix of amorphous structure. For example, the crystalline phases can exist in the form of dendrites. The crystalline phase inclusions can impart a host of favorable materials properties on the bulk material. For example, the crystalline phases can allow the material to have enhanced ductility, compared to where the material is entirely constituted of the amorphous structure. BMGs and BMGMCs can be referred to collectively as BMG-based materials. Similarly, metallic glasses, metallic glasses that include crystalline phases of material, BMGs, and BMGMCs can be referred to collectively as metallic glass-based materials or MG-based materials.
Although considerable advances have been made in the development of MG-based materials, they have yet to be developed to an extent where they can truly be implemented as viable, widespread engineering materials. Recently, efforts have been made to develop MG-based feedstock that is in the form of conventional sheet metal, e.g. a sheet of material having a thickness of between approximately 0.1 mm and approximately 10 mm, and being substantially planar otherwise. It is believed that such ‘MG-based sheet materials’ can lend themselves to conventional manufacturing processes, and thereby facilitate the widespread implementation of MG-based materials.
Systems and methods in accordance with embodiments of the invention advantageously shape sheet materials that include metallic glass-based materials. In one embodiment, a method of shaping a sheet of material including a metallic glass-based material includes: heating a metallic glass-based material within a first region within a sheet of material to a temperature greater than the glass transition temperature of the metallic glass-based material; where the sheet of material has a thickness of between approximately 0.1 mm and approximately 10 mm; where at least some portion of the sheet of material does not include metallic glass-based material that is heated above its respective glass transition temperature when the metallic glass-based material within the first region is heated above its respective glass transition temperature; and deforming the metallic glass-based material within the first region while the temperature of the metallic glass-based material within the first region is greater than its respective glass transition temperature.
In another embodiment, the sheet of material has a thickness of between approximately 0.1 mm and approximately 3 mm.
In still another embodiment, the temperature of the metallic glass-based material within the first region is maintained below its crystallization temperature when it is heated above the glass transition temperature.
In yet another embodiment, at least a majority of the sheet of material, as measured by volume, does not include metallic glass-based material that is heated above its respective glass transition temperature when the metallic glass-based material within the first region is heated above its respective glass transition temperature.
In still yet another embodiment, heating the metallic glass-based material within the first region is accomplished using one of: induction heating, frictional heating, and a heated fluid.
In a further embodiment, deforming the metallic glass-based material within the first region is accomplished by pressing a shaping tool into the sheet of material.
In a still further embodiment, a method of shaping a sheet of material including a metallic glass-based material includes: subjecting a sheet of material including a metallic glass-based material to direct contact with a heated fluid so as to raise the temperature of at least some portion of the metallic glass-based material to a temperature that is above its glass transition temperature; where the sheet of material has a thickness between approximately 0.1 mm and 10 mm; and deforming the metallic glass-based material that has been heated by the heated fluid to a temperature above its glass transition temperature.
In a yet further embodiment, the sheet of material is between approximately 0.1 mm and 3 mm.
In a still yet further embodiment, the metallic glass-based material that is heated above its glass transition temperature because of the heated fluid is maintained at a temperature lower than its crystallization temperature.
In another embodiment, deforming the metallic glass-based material that has been heated by the heated fluid is accomplished by using the heated fluid to deform the sheet of material.
In yet another embodiment, deforming the metallic glass-based material that has been heated by the heated fluid is accomplished by pressing a shaping tool into the sheet of material as it is supported, at least in part, by the heated fluid.
In still another embodiment, a method of shaping a sheet of material including a metallic glass-based material includes: moving a surface relative to a sheet of material including a metallic glass-based material while the surface and the sheet of material are in direct contact so as to frictionally heat the metallic glass-based material within the sheet of material above its glass transition temperature; where the sheet of material has a thickness of between approximately 0.1 mm and approximately 10 mm; deforming the metallic glass-based material that has been heated by the frictional heating to a temperature above its glass transition temperature.
In still yet another embodiment, the sheet of material has a thickness of between approximately 0.1 mm and approximately 3 mm.
In a further embodiment, the metallic glass-based material that has been heated by the frictional heating is maintained at a temperature lower than its crystallization temperature during the frictional heating.
In a still further embodiment, moving the surface relative to the sheet of material includes rotating the surface relative to the sheet of material so as to frictionally heat it.
In a yet further embodiment, deforming the metallic glass-based material is accomplished by pressing the surface into the sheet of material.
In a still yet further embodiment, deforming the metallic glass-based material is accomplished by pressing the surface into the sheet of material so that it conforms to the shape of a mold cavity.
In another embodiment, deforming the metallic glass-based material is accomplished by using pressurized gas.
In still another embodiment, a method of shaping a sheet of material including a metallic glass-based material includes: deforming a metallic glass-based material within a sheet of material at a temperature lower than the glass transition temperature of the metallic glass-based material, the metallic glass-based material having a volume fraction of crystalline phase greater than approximately 30% and a fracture toughness greater than approximately 80 MPa·m1/2; where the sheet of material has a thickness of between approximately 0.1 mm and approximately 10 mm.
In yet another embodiment, the metallic glass-based material has a volume fraction of crystalline phase of greater than approximately 40% and a fracture toughness greater than approximately 100 MPa·m1/2.
In still yet another embodiment, the sheet of material has a thickness that is less than approximately three times the size of the plastic zone radius of the metallic glass-based material.
In a further embodiment, the sheet of material has a thickness that is less than approximately one-third the size of the plastic zone radius of the metallic glass-based material.
In a still further embodiment, the sheet of material has a thickness of between approximately 0.1 mm and approximately 3 mm.
In a yet further embodiment, deforming the metallic glass-based material is accomplished using a pressing tool.
In a still yet further embodiment, the method further includes removing portions of the sheet of material in a periodic fashion; and deforming the sheet of material that no longer includes the removed portions so as to form a cellular structure.
In another embodiment, deforming the sheet of material is accomplished using a punch and die.
In still another embodiment, the metallic glass-based material is Zr55.3Ti24.9Nb10.8Cu6.2Be2.8.
In yet another embodiment, a cellular structure includes a metallic glass-based material having a volume fraction of crystalline phase greater than approximately 30% and a fracture toughness greater than approximately 80 MPa·m1/2.
In still yet another embodiment, the metallic glass-based material has a volume fraction of crystalline phase greater than approximately 40% and a fracture toughness greater than approximately 100 MPa·m1/2.
In a further embodiment, the metallic glass-based material is Zr55.3Ti24.9Nb10.8Cu6.2Be2.8.
Turning now to the drawings, systems and methods for advantageously shaping sheet materials that include metallic glass-based materials are illustrated. In many embodiments, a method of shaping a sheet of material that includes a metallic glass-based material includes locally heating a region of the sheet of material, the region including a metallic glass based-material, such that the temperature of the metallic glass based-material that is within the region is elevated to above its glass transition temperature, and deforming the heated metallic glass-based material into a desired configuration. In numerous embodiments, the sheet of material has a thickness of between approximately 0.1 mm and 10 mm. In many embodiments, a method of shaping a sheet of material that includes a metallic glass-based material includes subjecting the sheet of material to direct contact with a heated fluid so as to raise the temperature of at least some portion of the metallic glass-based material to a temperature above its glass transition temperature, and deforming the metallic glass-based material while it is heated above its glass transition temperature. In numerous embodiments, a method of shaping a sheet of material that includes a metallic glass-based material includes moving a surface relative to the sheet of material while the surface and the sheet of material are in direct contact so as to frictionally heat the metallic glass-based material to a temperature above its glass transition temperature, and deforming the metallic glass-based material that has been heated by the frictional heating to a temperature above its glass transition temperature.
The efforts to develop metallic glass-based materials so that they can more viably be incorporated as engineering and/or design materials has led to the development of metallic glass-based materials in the form of conventional sheet metal. It is believed that metallic glass-based materials in this form factor can more easily lend themselves to conventional shaping processes, and can thereby promote their practicality. For example, metallic glass-based materials in the shape of conventional sheet metal can act as feedstock for subsequent shaping processes, e.g. those commonly used to form conventional metallic components. As one example, Prest et al. disclose a method for forming amorphous alloy sheets including pouring molten metal so that it forms a sheet, floating the sheet of molten metal on a second molten metal, cooling the sheet of molten metal to form a metallic glass, and annealing the sheet without deteriorating its metallic glass qualities in U.S. Pat. No. 8,485,245. The disclosure of U.S. Pat. No. 8,485,245 is hereby incorporated by reference in its entirety.
Although sheets of metallic glass-based material have been formed, they are typically still not entirely compatible with conventional shaping processes. For example, while metallic glasses may be relatively tough compared to conventional glasses, they may not be tough enough to withstand a conventional folding operation, e.g. one that a conventional metal may be able to withstand. In essence, sheets of metallic glass-based are not universally compatible with conventional forming/shaping operations. Instead, methods for forming a metallic glass-based sheet material typically involve heating the sheet so that it may be thermoplastically formed/shaped. For example, in U.S. Pat. No. 8,613,815, Johnson et al. disclose using a rapid capacitor discharge to heat an amorphous alloy sample above its glass transition temperature and simultaneously thermoplastically forming/shaping the sample. The disclosure of U.S. Pat. No. 8,613,815 is hereby incorporated by reference in its entirety. However, it is not clear that using a rapid capacitor discharge can be effective for example to heat a sheet of material based on a bulk metallic glass matrix composite that includes crystalline phases beyond some threshold extent. Instead, the crystalline inclusions may inhibit the heating effect of the rapid capacitive discharge.
Additionally, Jan Schroers et al. have disclosed the thermoplastic blow molding of metallic glass sheet materials to form/shape them; these techniques essentially regard the heating of the metallic glass sheet above the glass transition temperature, and thereafter shaping them using conventional blow molding techniques. Nonetheless, the techniques presently known for shaping metallic glass-based sheet materials may not be inefficient and non-optimal in a variety of circumstances. Accordingly, the instant application discloses further methods that can more efficiently shape metallic glass sheet material, and can thereby make metallic glass-based material an even more viable option as an engineering material.
For example, in some embodiments, metallic glass-based sheet material is heated only where deformation is to occur (as opposed to the entire metallic glass-based sheet material being heated). In this way, the risk of adversely impacting the material properties of the sheet material with unnecessary heating can be mitigated. In a number of embodiments, a heated hydraulic fluid is used to heat a metallic glass-based sheet material above its glass transition temperature; the hydraulic fluid can then be used in the shaping/forming of the metallic glass sheet material. Using heated hydraulic fluid in the shaping of metallic glass sheet material can be an effective shaping method insofar as the fluid can provide substantial pressure to the metallic glass sheet material and cause it to conform to unique mold cavity geometries that may be difficult to accomplish otherwise. In several embodiments, a metallic glass sheet material is frictionally heated to above its glass transition temperature; the tool causing the frictional heating may then be used to shape the metallic glass sheet material. In this way, cooling can be quickly initiated by removing the tool. Quickly initiating the cooling stage is important in maintaining the amorphous structure of the metallic glass-based material. In many embodiments, a method of shaping a metallic glass sheet material involves shaping the metallic glass-based sheet material at room temperature—this can be achieved when the metallic glass-based sheet material has the requisite materials properties. These processes are now discussed in greater detail below.
In many embodiments, metallic glass-based sheet materials are shaped by heating only those regions of the sheet where thermoplastic deformation is to take place. In this way the unnecessary heating of the remainder of the sheet material can be avoided. Avoiding the unnecessary heating of the remainder of the sheet material can confer a number of benefits. For example, in general, heating metallic glass-based materials to a temperature where they can be thermoplastically formed (e.g. above their glass transition temperatures) carries with it the risk of inadvertently heating the metallic glass-based materials to a temperature above the crystallization temperature, thereby causing the metallic-glass based material to crystallize and lose its glass-like qualities. Moreover, heating metallic glass-based materials additionally carries the risk of causing unwanted oxidation. Accordingly, by avoiding unnecessarily heating the sheet material where heating is not required, the risk of adversely affecting the material properties is correspondingly reduced. Moreover, avoiding the unnecessary heating can allow the shaping process to be more energy efficient, e.g. energy is not needed to heat the entire sheet material—only those portions that embody the deformation.
Additionally, the metallic glass-based material within a region can be heated 102 using any suitable technique in accordance with embodiments of the invention. For example, in many embodiments, the metallic glass-based material within the region is heated using induction heating. In a number of embodiments, the metallic glass-based material within the region is heated using a heated fluid. In many embodiments, the metallic glass-based material is heated frictionally. In general, any suitable method of heating the metallic glass-based material within the region can be implemented.
In numerous embodiments, at least some portion of the sheet material is maintained at a temperature lower than the glass transition temperature of the heated metallic-glass based material. In several embodiments, at least some of the metallic glass-based material within the sheet of material is at a temperature lower than its respective glass transition temperature when the metallic glass-based material within the region is heated above its respective glass transition temperature. In many embodiments, at least some portion of the sheet material is maintained at a lower temperature than the lowest glass transition temperature amongst any of the metallic glass-based materials that are present in the sheet of material. In a number of embodiments, the majority of the sheet material (e.g. as measured by volume, or alternatively, by surface area) does not include metallic glass-based material that is above its respective glass transition temperature when the metallic glass-based material within the region is heated to above its glass transition temperature. In several embodiments, the majority of the sheet of material is maintained at a temperature lower than the lowest glass transition temperature of any of the metallic glass-based materials that are present in the sheet of material. In many embodiments, the temperature of the metallic glass-based material is kept below the crystallization temperature.
Returning back to
Although
In some embodiments, the tool that is used to heat metallic glass-based material within a sheet is also used to shape the sheet material.
While the above illustrations depict that a cylindrical tool having a relatively large diameter is used to shape the metallic glass-based sheet material, it should be clear that a tool of any shape can be used to shape the sheet material object. For example, in some embodiments a line contact heater is used to heat and thermoplastically shape the sheet material.
The localized thermoplastic shaping techniques described above can be implemented and modified in any of a variety of ways in accordance with embodiments of the invention. For example, any of a variety of shaping tools can be used to shape heated metallic glass-based sheet materials. In some embodiments, a plurality of regions within a sheet of material including metallic glass-based materials are simultaneously thermoplastically shaped. It should also be appreciated that the sheet of material can include any suitable metallic glass-based material in accordance with embodiments of the invention, and is not limited to a particular subset of metallic glass-based materials. Generally, any of a variety of modifications to the above described techniques can be implemented in accordance with embodiments of the invention. Additionally, while the above discussion has focused on advantageously shaping sheet material including metallic glass-based materials using localized thermoplastic forming techniques, in many embodiments, fluids are used to thermoplastically form a sheet of material including metallic glass-based materials. These processes are now described in greater detail below.
In many embodiments, fluids are used to thermoplastically shape a sheet of material that includes a metallic glass-based material. In a number of embodiments, heated fluids are used to elevate the temperature of the constituent metallic glass-based material to above its respective glass transition temperature. Any fluid capable of heating a sheet of material including metallic glass-based material above the glass transition temperature of the metallic glass-based material can be utilized in accordance with embodiments of the invention. For example, in some embodiments, molten metal is used as the heating fluid. In a numerous embodiments, a conventional hydraulic fluid is used. In several embodiments, a heating oil is used. In a number of embodiments, a heating gas is used. In general, any suitable fluid that can heat a sheet of material including metallic glass-based materials can be utilized in accordance with embodiments of the invention. In many instances, it is simply required that the fluid be able to heat the sheet material to a temperature that is greater than approximately 350° C. The heated fluid can thereafter be used to apply pressure to the sheet of material and thereby cause it to conform to the shape of a tool. Using fluids in this manner can be advantageous insofar as fluids can more uniformly apply heat and pressure to a sheet of material against a tool irrespective of the tool geometry. For example, where a sheet of material is to be shaped by a curved tool, the liquid can more easily cause it to uniformly conform to the shape of the curvature. In general, the fluid can be used in conjunction with any shaping tool to shape the sheet of material in accordance with embodiments of the invention.
For example, in some embodiments, a shaping tool having a semi-circular cross section is used to shape a sheet of material including a metallic glass-based material in accordance with embodiments of the invention.
While
Of course, it should be appreciated that the above-described processes can be varied in any of a variety of ways in accordance with embodiments of the invention. For example, as previously mentioned, any of a variety of fluids can be implemented, and the fluids do not necessarily have to be liquid—they can be gaseous. Similarly, any of a variety of shaping tools can be used in conjunction with the above-described processes. Additionally, in some embodiments, the fluid does not heat the sheet of material above the glass transition temperature of the constituent metallic glass-based material; instead the sheet of material is separately heated (e.g. using an induction heater), and the fluid is used to thermoplastically shape the separately heated material sheet. In a number of embodiments, the fluid is used in conjunction with another mechanism (e.g. an induction heater) to heat the sheet of material above the glass transition temperature of the constituent metallic glass-based material. The sheet of material can thereby be thermoplastically formed. Of course it should be appreciated that the above techniques can be applied in conjunction with any of a variety of suitable metallic glass-based materials—the process is not limited to a particular subset of metallic glass-based materials. While the above discussion has regarded using fluids in conjunction with the thermoplastic shaping of a sheet of material including a metallic glass-based material, in many embodiments, a sheet of material including metallic glass-based materials is heated frictionally above the relevant glass transition temperature so that it can be thermoplastically formed. These processes are now discussed in greater detail below.
In many embodiments of the invention, a sheet of material including metallic glass-based materials is heated frictionally so that they may be thermoplastically shaped. Incorporating frictional heating in thermoplastic shaping processes can be advantageous insofar as the subsequent cooling of the material can be initiated efficiently and virtually immediately with the removal of the friction-causing mechanism. Recall that cooling rates play a vital role in allowing a metallic glass-based material to retain its amorphous structure. Frictional heating can be instituted using any of a variety of processes in accordance with embodiments of the invention. For example, in many embodiments, a surface is rapidly rotated while in direct contact with a sheet of material including a metallic glass-based material so as to raise the temperature of the metallic glass based material above the relevant glass transition temperature. In a number of embodiments, frictional heating is effectuated by translational sliding of a surface with the material sheet. In many embodiments, the surface is the shaping tool that is used to thermoplastically shape the material sheet. In general, any mechanism for frictionally heating the sheet of material can be incorporated in accordance with embodiments of the invention.
Although the above description and accompanying illustration depicts the using a shaping tool to shape the metallic glass sheet without the support of a mold cavity, in many embodiments a mold cavity is also used to help shape the sheet of material.
While the above descriptions have regarded scenarios where the shaping tool is also used to provide frictional heating, in many embodiments the friction causing mechanism and the shaping mechanism are distinct. For example,
In general, similar to before, the above-described processing techniques can be modified in any of a variety of ways in accordance with embodiments of the invention. While the above processes have largely regarded the thermoplastic shaping of metallic glass-based sheet materials, in many embodiments, shaping processes for cold-forming sheet materials including metallic-glass based materials that include crystalline inclusions are implemented, and these are now discussed in greater detail below.
Cold-Forming of Sheet Materials Comprising Metallic-Glass Based Materials that Include Crystalline Inclusions
Metallic glass-based materials are typically characterized as somewhat brittle (at least relative to conventional engineering metals such as steel), and their shaping largely revolves around thermoplastic deformation. However, in many embodiments of the invention, metallic glass-based materials that include crystalline inclusions undergo shaping procedures at temperatures below the respective glass transition temperature. In effect, the crystalline inclusions impart sufficient ductility to allow for such ‘cold-forming.’ In many embodiments, the constituent metallic glass-based material includes greater than approximately 30% crystalline inclusions (by volume) and has a fracture toughness of greater than approximately 80 MPa·m1/2. In a number of embodiments, the constituent metallic glass-based material includes greater than approximately 40% crystalline inclusions (by volume) and has a fracture toughness greater than approximately 100 MPa·m1/2. These characteristics can impart sufficient toughness to the sheet material to allow it to be cold formed. As an example,
It should of course be clear that any of a variety of forming operations can be implemented in accordance with embodiments of the invention. For example, in many embodiments, the sheet materials are formed using stamping tools. In a number of embodiments, they are formed with water jets. In several embodiments, lasers are used to shape the structures. In general, any of a variety of shaping procedures can be implemented.
Notably, the above-described processes can be used to create any of a variety of geometries. For example, in many embodiments, cellular structures are created.
As can be inferred from the above discussion, the above-mentioned concepts can be implemented in a variety of arrangements in accordance with embodiments of the invention. Accordingly, although the present invention has been described in certain specific aspects, many additional modifications and variations would be apparent to those skilled in the art. It is therefore to be understood that the present invention may be practiced otherwise than specifically described. Thus, embodiments of the present invention should be considered in all respects as illustrative and not restrictive.
The current application is a divisional of U.S. application Ser. No. 14/252,585, filed Apr. 14, 2014, which application claims priority to U.S. Provisional Application No. 61/811,405, filed Apr. 12, 2013, the disclosures of which are incorporated herein by reference in their entirety.
The invention described herein was made in the performance of work under a NASA contract, and is subject to the provisions of Public Law 96-517 (35 U.S.C. 202) in which the Contractor has elected to retain title.
| Number | Date | Country | |
|---|---|---|---|
| 61811405 | Apr 2013 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 14252585 | Apr 2014 | US |
| Child | 15856543 | US |
