Homogenized heterogeneous foil for light alloy metal parts

Abstract

A method for manufacturing an object. The method includes receiving an alloy composition required to manufacture an object, depositing a plurality of foils in a stack to form the object, applying heat to the stack at a first temperature to bond the plurality of foils to one another, and applying heat to the stack at a second temperature to homogenize the composition of the stack. The homogenized stack has a desired alloy composition.

Description

[0001] Cross - Reference to Related Applications This application is a continuation of U.S. patent application Ser. No. 18 / 482,866, filed Oct. 7, 2023, which is a divisional application of U.S. patent application Ser. No. 18 / 131,340, filed Apr. 5, 2023, which is a partial continuation of International (PCT) patent application No. PCT / US2021 / 065196, filed Dec. 27, 2021, and claims the benefit and priority of U.S. Provisional Application No. 63 / 131,285, filed Dec. 28, 2020, and U.S. Provisional Application No. 63 / 257,091, filed Oct. 18, 2021, and International (PCT) patent application No. PCT / US2021 / 030879, filed May 5, 2021, and International (PCT) patent application No. PCT / US2021 / 036770, filed Jun. 10, 2021, the entire disclosure of each of which is incorporated herein by reference as if set forth in full herein. Technical Field

[0002] The embodiments described herein relate to methods and systems for manufacturing objects, and more particularly but not limited to, methods and systems for manufacturing an object having a desired alloy composition from a stack of foils having a composition different from the desired alloy composition. Background Art

[0003] Laminated object manufacturing (LOM) techniques generally involve stacking multiple foils composed of at least two alloy layers and bonding the foils together to produce a solid object. Parts assembled by conventional LOM techniques have different compositions in the bonding regions between the foils and in the structural portions of the foils, which alternate throughout the part body. These composition gradients throughout the part can cause the mechanical properties of the composite LOM - assembled parts to not be equal to the properties predicted by the average composition of the alloy.

[0004] Accordingly, there is a need for improved LOM techniques. Summary of the Invention

[0005] This invention is intended to introduce some concepts in a simplified form that will be further described in the detailed description section below. This invention is not intended to identify or exclude key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

[0006] According to one aspect, an embodiment relates to a method of manufacturing an object. The method includes: receiving a desired alloy composition of the object; depositing a plurality of foils into a stack to form the object; applying heat to the stack at a first temperature to bond the plurality of foils to each other; and applying heat to the stack at a second temperature to homogenize the composition of the stack, wherein the homogenized stack has the desired alloy composition.

[0007] In some embodiments, a plurality of foils are patterned.

[0008] In some embodiments, the plurality of foils includes foils having at least two different compositions.

[0009] In some embodiments, each foil includes a plurality of layers. In some embodiments, each layer includes an aluminum alloy, a magnesium alloy, or a titanium alloy. In some embodiments, the alloy material is aluminum, chromium, copper, lithium, magnesium, titanium, nickel, silicon, or zinc. In some embodiments, the first layer forms the core of the foil and the second layer forms the cladding layer of the foil.

[0010] In some embodiments, the thickness of each foil is between 25 and 1000 microns.

[0011] In some embodiments, the second temperature is below the melting point of the plurality of foils.

[0012] In some embodiments, the second temperature is approximately equal to or below the solidus temperature of the plurality of foils of the desired alloy composition.

[0013] In some embodiments, the first temperature and the second temperature are the same.

[0014] In some embodiments, application of heat at the first temperature occurs in a first processing unit and application of heat at the second temperature occurs in a second processing unit. In some embodiments, the stack is maintained at the first temperature during transfer from the first processing unit to the second processing unit.

[0015] In some embodiments, the method further includes quenching the stack after homogenization. In some embodiments, quenching occurs in the same processing unit used to homogenize the stack.

[0016] In some embodiments, the desired alloy composition is a homogenized composition different from the composition of the plurality of foils. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Non-limiting and non-exhaustive embodiments of the present invention are described with reference to the following drawings, in which like reference numerals refer to like parts throughout the various views unless otherwise specified.

[0018] Figure 1 A side cross-sectional view of a metal laminate manufactured according to one embodiment is shown; Figure 2 A trimetric view and an object view of the metal laminate according to one embodiment are shown; Figure 1 of Figure 3Shows a cross-sectional view of respective foils according to one embodiment; Figure 4A -D shows foils in various configurations according to multiple embodiments; Figure 5 Shows a concentration curve of an interface between an intermediate layer and two core layers according to one embodiment; Figure 6 Shows an operating curve of a homogenization process according to one embodiment; Figure 7 Shows a flowchart of a method for manufacturing an object according to one embodiment; Figure 8 Shows an additive manufacturing system according to one embodiment, including two plates configured to apply at least one of heat and pressure to a layer stack to join the layers in the layer stack together; Figure 9 Schematically shows a method for additive manufacturing an object by diffusion bonding according to one embodiment; Figure 10 Schematically shows a method for additive manufacturing an object by transient liquid phase (TLP) diffusion bonding according to one embodiment; Figure 11 Schematically shows a method for additive manufacturing an object by soldering according to one embodiment. Detailed Description

[0019] The various embodiments are described more fully hereinafter with reference to the accompanying drawings, which form a part of this specification and show specific exemplary embodiments. However, the concepts of the present invention may be implemented in many different forms and should not be construed as limited to the embodiments described herein; rather, these embodiments are provided as part of a complete and comprehensive disclosure to fully convey the scope of the concepts, techniques, and implementations of the present invention to those skilled in the art. The embodiments may be practiced as a method, system, or device. Thus, the embodiments may take the form of hardware implementation, fully software implementation, or an implementation combining software and hardware. Therefore, the following detailed description should not be considered restrictive.

[0020] References in the specification to "one embodiment" or "an embodiment" mean that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one example implementation or technique according to the present invention. The phrase "in one embodiment" appearing throughout the specification does not necessarily refer to the same embodiment.

[0021] Furthermore, the language used in the specification is selected primarily for readability and guidance purposes and is not selected to describe or limit the disclosed subject matter. Accordingly, the present invention is intended to illustrate rather than limit the scope of the concepts discussed herein.

[0022] Embodiments of the present invention include a method for homogenizing the composition of lightweight alloy laminated parts. These laminated parts can be the product of the LOM process. In some embodiments, the parts may include a plurality of foils bonded together by a certain method, each foil including at least one core layer and at least one intermediate layer. In other embodiments, the parts may include a plurality of foils bonded together by a certain method, with foils of the same core layer and the same intermediate layer arranged alternately. In some embodiments, the process includes applying heat for a predetermined processing time to promote the solid-state diffusion of alloy elements throughout the body of the part. In some embodiments, the solid-state diffusion homogenizes the compositions of the alloy elements throughout the body of the part, thereby improving the mechanical properties of the parts produced by LOM. In an embodiment of this method, no significant amount of material is added to the part.

[0023] In some embodiments, the composition and relative fractions of the component layers that make up the foils are selected such that the fully homogenized part has an average composition corresponding to the target alloy. By using this method to combine and homogenize two or more layers of different alloys, a third alloy can be manufactured, which is determined by the composition and thickness of the component layers. In some embodiments, the target alloy has a composition and material properties similar to those of commercially available aluminum alloys manufactured conventionally.

[0024] The term "foil" refers to a metal sheet used to form each layer in a layer stack. The foil may include one or more sub-layers, at least one of which and optionally some intermediate layers, the intermediate layer including a metal alloy different from the first layer. In some embodiments, the thickness of the foil in one dimension is between 10 μm and 10 mm. In some embodiments, the thickness of the foil in one dimension is between 25 μm and 1000 μm. In further embodiments, the thickness of the foil in one dimension can be between 50 μm and 500 μm. In some embodiments, the foil can be patterned corresponding to the design of the object and its support structure. In some embodiments, the foil may include at least one of Al, Sb, Ba, Be, Bi, B, Cd, Ca, C, Cr, Co, Cu, Gd, Ga, H, Fe, Pb, Li, Mg, Mn, Mo, Nd, Ni, Nb, N, O, Pd, P, K, S, Si, Ag, Na, Sr, S, Ta, Th, Sn, Ti, V, Y, Zn, Zr or rare earth metals. In some embodiments, the foil may include at least one of aluminum, magnesium, titanium, aluminum alloy, magnesium alloy or titanium alloy.

[0025] The term "core" or "core layer" refers to the foil or a part of the foil that constitutes the main body of the layer stack. The alloy composition of the core layer material is described in the form of the main alloy element.

[0026] The term "intermediate layer" refers to a foil or a part of a foil that allows adjacent foils to be bonded. In some embodiments, the intermediate layer may be on the outer side of the foil and applied to at least one face of the core layer. In some embodiments, the thickness of the intermediate layer is less than the thickness of the core layer. The alloy composition of the intermediate layer is described in terms of the main alloying elements.

[0027] The term "cladding" or "coating layer" refers to the intermediate layer material bonded to the core layer before the bonding and homogenization processes. In some embodiments, a thin intermediate layer bonded to a component of the core layer by rolling is described as a "cladding foil".

[0028] "Layer stack" refers to at least two foils. In some embodiments, a single foil may include at least one support region and at least one object region. "Support" refers to the non-object part of the foil, which forms a bracket or fixture conforming to the outer appearance of the object when bonded together and can be used for subsequent post-processing. The bracket or fixture is composed of a combination of multiple support regions and can be called a "support part". The combination of each object region can be called an "object part". The process of the combination can be called "joining".

[0029] The term "aluminum" refers to any material containing aluminum. For example, a material containing aluminum can refer to a material of pure molecular aluminum, aluminum of standard industrial grade purity, an alloy of aluminum and at least one other element, or any combination thereof. In the case where the alloy contains a specific metal (such as aluminum), at least the main part of the alloy composition is the same specific metal. The minor alloying elements present can be described subsequently.

[0030] Some embodiments herein relate to methods of manufacturing metal objects from constituent metal layers having comparable mechanical properties. In some embodiments, these methods avoid using adhesives between the layers and instead use high-strength metal bonds between the constituent layers to form the object. For aluminum parts, some embodiments can use bonding methods such as diffusion bonding, transient liquid phase diffusion bonding, and / or brazing. Strong metal bonds can be generated through specific configurations of materials, such as alloy compositions, alloy structures of composite materials including two or more sub-layers with different compositions, and process conditions, such as the applied temperature and pressure, and a process with shorter time and greater robustness, which is useful for manufacturing aluminum parts.

[0031] In some embodiments, the manufacturing methods described herein first receive the desired alloy composition for manufacturing an object. These embodiments then apply heat to a stack of foils that includes at least one core layer and at least one intermediate layer to homogenize the composition of the stack. The resulting product is a homogenized object having the desired alloy composition. The foils in the stack can be selected such that, for example, one layer has a surplus of one element while an adjacent layer has a deficiency of the same element, such that the resulting object has a desired ratio of elements. This principle can be applied to multiple elements for forming the desired composition of the object.

[0032] Figure 1 A side cross-sectional view of a metal laminated object 100 manufactured according to one embodiment is depicted. In some embodiments, the object 100 can be manufactured on a print bed 105. In some embodiments, the foil 110 can be deposited onto the print bed 105. In some embodiments, multiple foils can be directly deposited onto the first foil 110 or can be subsequently added on top of the first foil 110.

[0033] Figure 2 Shows a Figure 1 trimetric view 205 and an object view 210 of a metal laminated object according to one embodiment. The object can be loaded into support portions 215, 220 and, as further explained in detail below, these support portions 215, 220 can be removed after forming the object portion 225 to produce the metal laminated object.

[0034] Figure 3 A cross-sectional view of respective foils 305, 315, 325 according to one embodiment is shown. In some embodiments, at least one foil in a stack of foils (not shown) can consist entirely of a core layer 310. In some embodiments, the foil 315 can include a core layer 330 and a separate intermediate layer 335 on one surface. In some embodiments, the intermediate layer 335 can be on top of the core layer 330. In some embodiments, the intermediate layer 335 can be on the bottom of the core layer 330. In some embodiments, the foil 325 can include a core layer 350 and two intermediate layers 335 on both sides of the foil.

[0035] In some embodiments, the core layer can include aluminum. In some embodiments, the core layer can be an aluminum alloy.

[0036] In some embodiments, the intermediate layer may comprise a metal or alloy having a melting point lower than that of the core layer. In some embodiments, the intermediate layer material may include at least one of aluminum, copper, chromium, iron, magnesium, manganese, silicon, titanium, and zinc. In some embodiments, the metal elements may be present in a variety of different combinations, and the selection of each composition is made to have a specific set of properties that match its bonding method (e.g., surface oxidation resistance, surface oxide disruption, optimal melting temperature) and liquid properties (e.g., wettability on the core layer). In some embodiments, the two intermediate layers may include different materials. In some embodiments, the two intermediate layers may be the same.

[0037] In some embodiments, the thickness of the intermediate layer may be 1-50% of the thickness of the core layer. In some embodiments, the thickness of the intermediate layer may be 0-5% of the thickness of the core layer 330. In some embodiments, the thickness of the intermediate layer of a single-clad foil may be 1-25% of the thickness of the core layer 330. In some embodiments, the thickness of the intermediate layer of a double-clad foil may be 2-50% of the thickness of the core layer.

[0038] In some embodiments, the thickness of the intermediate layer is less than the thickness of the core layer. In some embodiments, the total thickness of the foil is greater than 25 μm. In other embodiments, the total thickness of the foil is less than 1000 μm. In some embodiments, the thickness of the core layer and the intermediate layer and the ratio of the core layer thickness to the intermediate layer thickness are variable and optimized for a specific bonding method.

[0039] In some embodiments, the specific composition of the intermediate layer is selected such that the intermediate layer material melts at a lower temperature than the core layer. In some embodiments, the intermediate layer material is selected to minimize the melting temperature. In some embodiments, the melting temperature of the intermediate layer material may be greater than 500°C and less than 590°C. In some embodiments, the melting temperature of the intermediate layer material may be lower than 500°C. In different subsets of these embodiments, the melting temperature of the intermediate layer material may be lower than 490°C. In some embodiments, the ratio and composition of the intermediate layer material and the core layer material are selected such that the final mechanical properties of the object are those of the desired composition. In some embodiments where the intermediate layer composition is a small fraction of the total foil, the desired composition may be within the tolerance of the composition of the core material.

[0040] In some embodiments, the composition of the foils in the stack is selected such that once heated, the finished object has the desired composition. For example, if the finished object is to have a desired composition that matches a specific alloy, the individual sheets may each have an excess or deficiency of various elements, but when heated, the finished object has a substantially homogenized composition that matches the desired composition.

[0041] For example,Figure 4A Shows a foil 400a according to one embodiment. The foil 400a includes a single core layer 402a, with an intermediate layer 404a coated on one side thereof. Figure 4B Shows a foil 400b according to another embodiment. The foil 400b includes a single core layer 402b, with intermediate layers 404b coated on both sides thereof.

[0042] The core layers 402a and 402b may mainly include aluminum or magnesium. Other alloying elements may be present, such as but not limited to copper, silicon, zinc or other materials as described above.

[0043] The intermediate layers 404a and 404b may include a certain combination of aluminum, copper, magnesium, silicon and zinc or other materials as described above. The intermediate layers 404a and 404b may alternatively include a uniform layer of any single element in the aforementioned list.

[0044] In some embodiments, the intermediate layer accounts for 1 - 50% of the total thickness of the foil. In some embodiments, such as those where the intermediate layer includes a single element, the intermediate layer may include a thin layer less than 5% of the total thickness of the foil.

[0045] The specific composition of the core layer or the intermediate layer may match that of commercially available aluminum alloys. For example, the core layer may include 2024, 5182, 6061 or another alloy. Custom alloys that generally match the composition of commercial alloys but have an increased or decreased concentration of one or more elements in the intermediate layer may also be used. The intermediate layer may include 2024, 4004, 5182, 6061, 7075 or another commercial aluminum alloy. The intermediate layer may also include custom alloys that match the composition of commercial alloys but may also have an increased or decreased concentration of one or more elements.

[0046] The composition of the core layer and the intermediate layer may vary relative to each other. For example, in some embodiments, elements that are in excess in the intermediate layer may be present in the core layer at a lower concentration to achieve the desired composition after homogenization.

[0047] Alternatively, elements that are in excess in the core layer may be present in the intermediate layer at a lower concentration to achieve the desired composition after homogenization. The relative thicknesses of the layers may also be selected such that the average composition of the alloy matches that of 2024, 6061, 7075 or another desired composition.

[0048] As another example, the core layer may include a magnesium alloy with a high melting point. The intermediate layer may include a low melting point magnesium alloy and a custom alloy with an increased or decreased concentration of alloying elements. In some embodiments, the intermediate layer may include elements that lower the melting point of magnesium.

[0049] In operation, a user or a system can place the parts in a heating environment, such as a furnace. The furnace can apply heat to the parts to increase the temperature of the parts and maintain the temperature of the parts at a certain temperature or within a certain temperature range for a period of time. Specifically, the technology according to the embodiments herein can include a bonding stage, in which the layers are heated and bonded together, and then a homogenization stage, in which the bonded layers are heated to produce a homogenized product. Then, the homogenized product can be quenched.

[0050] In some embodiments, the bonded parts can be transferred to a separate furnace processing unit that performs the homogenization stage. For example, the parts can be moved together with a support structure. In other embodiments, a chamber can protect the parts during movement to prevent surface oxidation. In some embodiments, the chamber can be in a vacuum state, or be a protective gas chamber with an inert gas or a non-oxidizing gas present around the parts. In some embodiments, these steps can further include a polishing step, in which the parts can be polished or otherwise modified before or after the homogenization treatment.

[0051] During the heating stage, the furnace can apply heat to the parts to increase their temperature to the processing temperature. That is, heat can be applied to the parts until the temperature of the parts reaches the processing temperature.

[0052] In some embodiments, the processing temperature is lower than the solidus temperature of the intermediate layer and the core layer. For example, the furnace can be configured to set the processing temperature to be 5°C to 100°C lower than the solidus temperature of the intermediate layer.

[0053] In some embodiments, during homogenization, the parts can be in a heated press to increase or improve the heat transfer to the parts. Well-controlled heat transfer can enable the parts to be heated more evenly and consistently during the processing stage, so that the rate of diffusion of elements in the parts can be finely controlled without melting the parts. This increases the diffusion rate and reduces the possibility of forming defects in the parts.

[0054] Figure 4C It shows that a foil or a part 406 is manufactured by stacking foils, such as foils 400a or 400b. For example, it can be seen that the part 406 includes a plurality of core layers 402c and a plurality of intermediate layers 404c.

[0055] During the homogenization process, the foil materials (such as foil materials 400a-c) are held at the processing temperature for a period of time to allow the elements in the intermediate layer and the core layer to diffuse into each other, thereby forming a substantially uniform composition in both regions. This interdiffusion process involves two simultaneous phenomena. That is, the elements present in the intermediate layer diffuse into the core layer region, and the elements present in the core layer diffuse into the intermediate layer region. Since the thickness of the core layer can be at least several times the thickness of the intermediate layer, the element that diffuses the slowest is the component that is present in at least one of the core layer and the intermediate layer and diffuses into the complementary layer.

[0056] In addition, under the same concentration gradient, temperature, and other environmental conditions, elements with lower diffusion coefficients diffuse more slowly than elements with higher diffusion coefficients. Therefore, the element that diffuses the slowest is the element with the lowest diffusion coefficient. Once the element that diffuses the slowest is present in the region previously occupied by the core layer and the intermediate layer, and the peak composition of the element that diffuses the slowest is within the standard tolerance of the alloy composition in the published standard (such as the specified TEAL table), the foil can be considered to be homogenized.

[0057] Figure 4D Figure 408 shows a part produced by the homogenization process according to one embodiment. As Figure 4D shown, at least a portion of part 408 is fully homogenized and has a uniform composition.

[0058] Figure 5 Figure 500 shows a concentration profile of an interface including an intermediate layer 502 and adjacent to two core layers 504 over time during the homogenization process. In this example, initially (i.e., before the start of the homogenization process), there is an alloy element that is present in the intermediate layer 502 but not in either core layer 504.

[0059] Curve 506 represents the initial concentration of this alloy element before the start of the homogenization process. As Figure 5 shown, the concentration of this alloy element is higher in the intermediate layer 502 but zero in the core layer 504. That is, before the start of the homogenization process, the composition of the core layer 504 does not contain this alloy element.

[0060] Three progressive curves 508, 510, and 512 represent the concentrations of alloying elements at different times during the entire homogenization process. Curve 508 represents the concentration of alloying elements at time t1, curve 510 represents the concentration of alloying elements at time t2, and curve 512 represents the concentration of alloying elements at time t3, where t1 < t2 < t3. From t1 to t3, the composition of the alloying elements in the intermediate layer 502 decreases as they diffuse out of the region previously occupied by the intermediate layer 502. At the same time, the composition of the alloying elements in the core layer 504 increases. Curve 514 represents the concentration of alloying elements at the end of the homogenization process. As shown in the distribution map 500, the concentration of alloying elements in the intermediate layer 502 decreases, while the concentration of alloying elements in the core layer 504 increases.

[0061] Figure 6 The operating curve 600 of the homogenization process over time according to an embodiment is shown. The homogenization process associated with the curve 600 of Figure 6 may be similar to the process described, for example, in combination with Figure 5 .

[0062] Before the start of the homogenization process, the temperature 602 is initially at room temperature or ambient temperature 604. The temperature 602 can be heated to a temperature below the interlayer solidus temperature 606. The interlayer solidus temperature 606 is lower than the core layer solidus temperature 608.

[0063] The time required for the homogenization process depends in part on the thickness of the core layer and the intermediate layer. For example, the time required for the homogenization process is proportional to the thickness of the layer. Specifically, foils with a thinner intermediate layer require less time to homogenize.

[0064] Similarly, the migration rate of the diffusing elements increases with increasing temperature. Therefore, the time required for the homogenization process is also a function of temperature and decreases as the processing temperature increases.

[0065] After a period of time sufficient to promote the homogenization process, the temperature 602 can be reduced back to room temperature or ambient temperature 604. The cooling phase can involve quenching the part in water, oil, or other fluids; cooling the part using a fan or by blowing air, natural cooling, etc.

[0066] Figure 7 The flowchart of a method 700 for manufacturing an object according to an embodiment is depicted. A homogenized part produced from two or more different component layer alloys can exhibit mechanical properties superior to any of the constituent alloys. In some cases, the composition of the alloys selected for the component layers can have weaker mechanical properties than the final homogenized part.

[0067] For example, the core layer and the intermediate layer can alternatively include a greater proportion of magnesium and silicon than the stoichiometric ratio of 2:1. This stoichiometric ratio typically results in a brittle and bendable material. However, the total proportion of magnesium and silicon is present in such a ratio that the homogenized part is a high-strength, hardened 6000 series alloy, and the magnesium-silicon ratio meets the required alloy composition. This allows for fine-tuning of the processing conditions (such as the melting temperature) of the alloy by the selective presence of magnesium and silicon without the negative consequences of an excess of one of these elements in the final homogenized part.

[0068] Step 702 involves receiving the required alloy composition of the object. The required alloy composition can be an aluminum-copper-rich alloy in the 2000 series, a silicon-rich aluminum alloy in the 4000 series, a magnesium-rich aluminum alloy in the 5000 series, a magnesium- and silicon-rich aluminum alloy in the 6000 series, a zinc-rich aluminum alloy in the 7000 series, etc.

[0069] Step 704 involves depositing a plurality of foils into a stack to form the object. As part of step 704, the type of foils deposited in the stack can depend on the required alloy composition specified in step 702.

[0070] For example, if the required alloy composition is an aluminum alloy in the 6000 series, a core layer of a 6000 series alloy and an intermediate layer of a 2000 series alloy can be employed. In this case, copper from the copper-rich 2000 series intermediate layer will diffuse into the core layer of the 6000 series alloy, resulting in a low-copper 6000 series alloy, such as 6061, which is a high-strength processing alloy.

[0071] If the required alloy composition is a magnesium-rich aluminum alloy in the 5000 series, a core layer of a 1000 series, 3000 series, or 1000 series alloy and an intermediate layer of a 5000 series alloy can be used. If the required alloy composition is a silicon-rich aluminum alloy in the 4000 series, a core layer of a 6000 series alloy and an intermediate layer of a 4000 series alloy can be used. If the required alloy composition is a zinc-rich aluminum alloy in the 7000 series, a core layer of at least one of the 2000 series, 5000 series, 6000 series, or 7000 series alloys and an intermediate layer of a 7000 series alloy can be used.

[0072] In some embodiments, when the homogenized part is an aluminum alloy of the X000 series, both the intermediate layer and the core layer can be alloys of the same X000 series. In other embodiments, when the homogenized part is an aluminum alloy of the X000 series, both the intermediate layer and the core layer can be custom alloys that match the composition of the X000 series, except that one of the core layer or the intermediate layer has an excess of at least one element, while the complementary alloy has a deficiency of at least one of the same elements.

[0073] In some embodiments, the composition of each foil layer in the stack can be selected so that when diffused using the aforementioned method, the result is an object with a homogenized composition that matches a desired composition that is different from the composition of the constituent foil. The following table lists several alloys and the constituent foils that can be used to achieve these alloys.

[0074]

[0075] Table 1 - Required alloy is 6000 series aluminum alloy (all compositions are expressed in wt.%)

[0076] Table 2 - Required alloy is 6000 series aluminum alloy (all compositions are expressed in wt.%)

[0077] Table 3 - Required alloy is 6000 series aluminum alloy (all compositions are expressed in wt.%)

[0078] Table 4 - Required alloy is 6000 series aluminum alloy (all compositions are expressed in wt.%)

[0079] Table 5—Required alloy is 2000 series aluminum alloy (all compositions are expressed in wt.%)

[0080] Table 6—Required alloy is 2000 series aluminum alloy (all compositions are expressed in wt.%)

[0081] Table 7—Required alloy is 7000 series aluminum alloy (all compositions are expressed in wt.%)

[0082] Table 8 - Required alloy is 7000 series aluminum alloy (all compositions are expressed in wt.%)

[0083] Table 9—Required alloy is 7000 series aluminum alloy (all compositions are expressed in wt.%)

[0084] Table 10—Required alloy is 300 series aluminum alloy (all compositions are expressed in wt.%) Each table specifies a different composition for the core layer and the cladding layer (i.e., the intermediate layer), while the table label specifies the desired alloy series. The numerical entries correspond to the weight fractions of each major alloying element, with the balance being aluminum (Al). These compositions above are merely exemplary, and other compositions can be achieved according to the embodiments herein.

[0085] The foil can be clad on one or both sides, and the total thickness of the foil can be between 25 µm and 1000 µm. The core layer thickness is typically greater than the intermediate layer thickness. In some embodiments, for each example, the foil is "all-core" or "all-clad". In these embodiments, the foils can be arranged alternately to produce the same striped layer structure of alternating core and cladding layers as can be produced by stacking clad foils.

[0086] Step 706 involves applying heat to the stack at a first temperature to bond the plurality of foils to each other. The stack can include multiple layers of foils. Each layer can include, for example, an aluminum alloy, a magnesium alloy, or a titanium alloy. The alloying materials can be aluminum, chromium, copper, lithium, magnesium, manganese, titanium, nickel, silicon, or zinc. The first temperature required to bond the foils together can depend on the materials used.

[0087] Step 708 involves applying heat to the stack at a second temperature to homogenize the composition of the stack. As previously mentioned, the stack (e.g., the foils) can be heated to achieve the desired level of interdiffusion. In some embodiments, the second temperature is below the melting point of the plurality of foils. In some embodiments, the second temperature can be close to the solidus temperature of the plurality of foils or the desired alloy composition. In some embodiments, the second temperature can be the same as the first temperature.

[0088] Step 710 is optional and involves quenching the stack after homogenization. This quenching step can be performed in the same processing unit where the homogenization step occurs, or at a location outside the processing unit where the homogenization step occurs. The optional quenching step can be employed according to the desired alloy properties.

[0089] Figure 8 An additive manufacturing system 800 according to one embodiment is shown, which includes two plates 805’, 805” (collectively referred to as "805"), configured to apply at least one of heat and pressure to a layer stack 815 to bond foils 810. Some embodiments can use at least one bonding method to join at least two foils 810 within the layer stack 815.

[0090] In some embodiments, the platen 805 can be at least one of a pressing or heating platen. In some embodiments, the platen 805 can be configured to apply at least one of heat or pressure to opposite sides of the layer stack 815. In some embodiments, applying at least one of heat or pressure raises the temperature of the layer stack 815 to a temperature below the melting temperature of the core layer of the foil 810 such that at least one of heat or pressure causes the first foil in the layer stack 815 to bond to the second foil.

[0091] In some embodiments, to bond the object area 820, the platen 805 can apply uniform pressure to the layer stack 815. In some embodiments, the layer stack 815 can include a fully enclosed structure of the object area 820. The fully enclosed structure can include at least two support areas 825, 830 such that the object area 820 is completely enclosed within the support areas 825, 830.

[0092] In some embodiments, the support areas 825, 830 are configured to conduct at least one of heat or pressure from the platen 805 through the layer stack 815. This conduction of heat or pressure facilitates the bonding of the foils 810 to form the bonded object area 820. In some embodiments, the platen 805 applies at least one of heat or pressure to the support areas 825, 830, and the support areas 825, 830 in turn conduct at least one of heat or pressure to the object area 820. In some embodiments, the support areas 825, 830 can have flat surfaces such that the platen 805 can apply at least one of pressure or heat uniformly across the surface. In some embodiments, the support area is a single support area surrounding the object area 820 and can be used to create a negative image of the object. In some embodiments, the bonding process of the object area 820 can occur in an oxidizing atmosphere (such as air). In some embodiments, the bonding process of the foils 810 can be enclosed in a vacuum or inert gas chamber.

[0093] In some embodiments, the system can employ at least one of diffusion bonding, transient liquid phase diffusion bonding, and / or brazing. In some embodiments, the alloy composition and processing conditions are optimized to achieve effective diffusion bonding.

[0094] Figure 9 Method 900 for additive manufacturing an object by diffusion bonding according to one embodiment is schematically illustrated. Method 900 includes applying heat to a stack of foils to bring the foils to a bonding temperature (step 905). In some embodiments, the bonding temperature can be below the melting temperature of the core layer of the foil and high enough to promote diffusion and bonding between adjacent foils. In some embodiments, the bonding temperature can be below the temperature of the intermediate layer of the foil. In some embodiments, at least one platen can apply heat to the foils.

[0095] In some embodiments, a stack of foils can be raised to a bonding temperature and an optional pressure (step 915) and held at the bonding temperature and optional pressure (step 925) until elements from adjacent core layers diffuse into each other, thereby bonding the stack of foils into an object region (step 930).

[0096] In some embodiments, the method can include a sequential diffusion bonding process. In the sequential diffusion bonding process, the method can include adding a foil to an object or a portion of an object at a bonding temperature (step 920). In some embodiments, the bonding temperature can be lower than the melting temperature of the core layer material. Alternatively, a foil can be added to a cold stack of foils, and the stack with the additional foil can be raised to the bonding temperature. In some embodiments, a foil is added to a heated stack and pressure is applied to the stack. In some embodiments, after pressure is applied, the pressure is released to add another foil (step 920).

[0097] In some embodiments, temperature can facilitate diffusion and bonding between the core layer of the added foil and elements of the object, thereby causing the bonding process to occur.

[0098] In some embodiments, at least one of the object or its components can be used as a heat sink. In some embodiments, the heat sink can create a temperature gradient across the object, with the aim of selectively facilitating diffusion bonding in a sub-region of the object. In some embodiments, the diffusion process can be repeated until the object is complete.

[0099] Figure 10 A method 1000 for additive manufacturing of an object by transient liquid phase (TLP) diffusion bonding according to one embodiment is schematically illustrated. Some embodiments can optimize alloy compositions and processing conditions for effective bonding by transient liquid phase (TLP) diffusion bonding in an oxidizing or non-oxidizing atmosphere or in a vacuum.

[0100] In some embodiments, the core material is aluminum or an aluminum alloy. In some embodiments, the core material can include at least one of aluminum, magnesium, titanium, copper, silicon, or zinc. The alloying elements can include at least one of magnesium or zinc. In some embodiments, the cladding intermediate layer can include at least one of an aluminum-magnesium alloy, a magnesium-zinc alloy, an alloy of at least two of aluminum, copper, magnesium, silicon, or zinc, or any combination thereof. In some embodiments, at least one of these intermediate layer alloying elements can be used as an oxide getter to preferentially bind to oxygen at a higher rate than aluminum.

[0101] In some embodiments, the aluminum alloy foil may comprise between 20% and 100% aluminum. In some embodiments, the aluminum alloy foil may comprise at least one of Sb, Ba, Be, Bi, B, Cd, Ca, C, Cr, Co, Cu, Ga, Fe, Pb, Li, Mg, Mn, Ni, O, P, K, Sc, Si, Ag, Na, Sr, Sn, Ti, V, Zn, or Zr. In some embodiments, the aluminum alloy foil may comprise more than 50% Cu. In some embodiments, the aluminum alloy foil may comprise more than 40% Fe. In some embodiments, the aluminum alloy foil may comprise more than 40% Mg. In some embodiments, the aluminum alloy foil may comprise more than 40% Ni. In some embodiments, the aluminum alloy foil may comprise more than 40% Zn. In some embodiments, the aluminum alloy foil may comprise more than 60% Si.

[0102] In some embodiments, the magnesium alloy foil may comprise between 45% and 100% magnesium. In some embodiments, the magnesium alloy foil may comprise at least one of Al, Be, Ca, Ch, Cu, Gd, Fe, Li, Mn, Nd, Ni, Si, Ag, Th, Y, Zn, Zr, or rare earth metals. In some embodiments, the magnesium alloy foil may comprise more than 40% Al.

[0103] In some embodiments, the titanium alloy foil may comprise between 70% and 100% titanium. In some embodiments, the titanium alloy foil may comprise at least one of Al, B, C, Cr, Cu, H, Fe, Mn, Mo, Ni, Nb, N, O, Pd, Si, S, Ta, Sn, V, Y, or Zr.

[0104] In some embodiments, the melting temperature of the intermediate layer may be at least 10 °C lower than the melting temperature of the core layer. The melting temperature of the intermediate layer can be minimized to reduce energy costs and the complexity of the processing machine. In some embodiments, the melting temperature of the intermediate layer may be below 500 °C.

[0105] In some embodiments, the total foil thickness is generally between 25 μm and 1000 μm. Each intermediate layer can reach 50% of the thickness of the core material and can be between 1 μm and 50 μm thick. The intermediate layer material can be deposited on one or both sides of the core material to form a single foil.

[0106] In some embodiments, the method may utilize a diffusion element including at least one of Cu, Mg, Zn, or Si. In some embodiments, the intermediate layer may include at least 0.2% of Cu. In some embodiments, the diffusion element may include at least 1% of Cu. In some embodiments, the diffusion element may include at least 2% of Cu. In some embodiments, the diffusion element may include up to 4% of Cu. In some embodiments, the diffusion element may include up to 5% of Cu. In some embodiments, the diffusion element may include up to 6% of Cu. In some embodiments, the diffusion element may include up to 6.3% of Cu.

[0107] In some embodiments, the method includes heating a stack of foils to a bonding temperature (step 1005), the bonding temperature being greater than the melting temperature of the intermediate layer but less than the melting temperature of the core layer that composes the foils.

[0108] In some embodiments, the method may include compressing the stack of foils by applying pressure (step 1010). In some embodiments, the pressure may be on the order of 0.1 - 100 MPa.

[0109] In some embodiments, applying at least one of temperature or pressure may cause the intermediate layer to melt, thereby increasing the rate at which elements of the core layer diffuse into the intermediate layer and the rate at which elements of the intermediate layer diffuse into the core layer (step 1015). In some embodiments, the applied pressure may promote element mixing between the core layer and the intermediate layer of adjacent foils.

[0110] In some embodiments, as elements of the intermediate layer and the core layer diffuse into each other, the average composition of the stack of foils changes to resemble the final average composition of the object, and the melting temperature increases with the change in composition. In some embodiments, new bonds are formed between the metal components.

[0111] In some embodiments, the process may be completed sequentially. In a sequential process, foils may be added to the part at the bonding temperature, the bonding temperature being greater than the melting temperature of the intermediate layer material, or new foils may be added to a cold stack and then raised to the bonding temperature. In some embodiments, the intermediate layer of the added foils may melt (step 1015) to continue the bonding process.

[0112] In some embodiments, previously deposited layers are not affected by the process because their compositional intermediate layers have already diffused and bonded with the core layer such that the part does not melt at the applied bonding temperature.

[0113] Figure 11 Method 1100 for additive manufacturing of an object by soldering according to one embodiment is schematically shown. In some embodiments, soldering is used to optimize the alloy composition and processing conditions for bonding.

[0114] In some embodiments, the method includes depositing a first foil (step 1105). In some embodiments, the first foil can be deposited on a print bed. In some embodiments, the first foil can be deposited on the foil. In some embodiments, the method also includes depositing a second foil (step 1115). In some embodiments, the foil can include at least one intermediate layer and at least one core layer.

[0115] In some embodiments, the foil may be heated to a bonding temperature (step 1120). In some embodiments, the bonding temperature is greater than the melting temperature of the intermediate layer but less than the melting temperature of the core layer of the foil.

[0116] In some embodiments, the foil may be maintained at the bonding temperature for a fixed period of time (step 1125). In some embodiments, maintaining the foil at the bonding temperature may cause the intermediate layer to melt, which increases the rate at which elements of the core layer diffuse into the intermediate layer, and correspondingly increases the rate at which elements of the intermediate layer diffuse into the core layer.

[0117] This process causes a metallic bond to form between adjacent stacked foils, thereby forming an object (step 1130 ).

[0118] In some embodiments, the brazing process can be done sequentially. In a sequential brazing process, foil can be added to a subassembly or object comprising multiple bonded foils. In some embodiments, additional liquid flux can be applied to the void space between the added foil and the object.

[0119] In some embodiments, the added foil and the part may be heated to a bonding temperature greater than the melting temperature of the intermediate layer of the added foil but less than the melting temperature of the core layer of the added foil and less than the melting temperature of the alloy comprising the part (step 1120).

[0120] In some embodiments, the added foil and part may be held at the bonding temperature for a fixed period of time (step 1125), which causes the intermediate layer of the added foil to melt and the bonding process described above to occur.

[0121] In some embodiments, previously deposited layers may not be affected by this process because their constituent interlayers have already melted, interdiffused, and bonded with the core layer, so the object does not melt at the applied bonding temperature.

[0122] In some embodiments, the alloy compositions of the core and intermediate layers may be used in other form factors, such as core structure powders or core structure wires, or a combination of both powder compositions. These may then be bonded, and when diffused using the aforementioned process, the result is an object with a homogenized composition that matches the desired composition that is different from the composition of the constituent raw materials.

[0123] The methods, systems, and devices discussed above are examples. Various configurations may omit, substitute, or add various procedures or components as needed. For example, in alternative configurations, the methods may be performed in an order different from the described order, and various steps may be added, omitted, or combined. Additionally, features described with respect to certain configurations may be combined in various other configurations. Different aspects and elements of the configurations may be combined in a similar manner. Moreover, technology is constantly evolving, so many elements are examples and do not limit the scope of the invention or the claims.

[0124] For example, embodiments of the present invention have been described above with reference to block diagrams and / or operational descriptions of methods, systems, and computer program products according to embodiments of the present invention. The functions / actions indicated in the blocks may not occur in the order shown in any flowchart. For example, two consecutive blocks shown may actually be performed substantially simultaneously, or sometimes the blocks may be performed in the reverse order, depending on the functions / actions involved. Additionally or alternatively, not all blocks shown in any flowchart need to be executed and / or implemented. For example, if a given flowchart has five blocks containing functions / actions, perhaps only three of the five blocks are executed and / or implemented. In this example, any three of the five blocks may be executed and / or implemented.

[0125] Stating that a value exceeds (or is greater than) a first threshold is equivalent to stating that the value meets or exceeds a second threshold that is slightly greater than the first threshold. For example, the second threshold is a value in the relevant system resolution that is higher than the first threshold. Stating that a value is less than the first threshold (or within it) is equivalent to stating that the value is less than or equal to a second threshold that is slightly lower than the first threshold. For example, the second threshold is a value in the relevant system resolution that is lower than the first threshold.

[0126] Specific details are given in the description to provide a thorough understanding of example configurations (including implementations). However, the configurations may be practiced without these specific details. For example, well-known circuits, processes, algorithms, structures, and techniques have been shown without unnecessary detail to avoid obscuring the configurations. This description merely provides example configurations and does not limit the scope, applicability, or configurations of the claims. Instead, the previous description of the configurations will provide those skilled in the art with a useful description for implementing the techniques. Various changes may be made to the functions and arrangements of the elements without departing from the spirit or scope of the invention.

Claims

1. A coated foil, comprising: a core comprising the balance Al and 0.2 - 0.4 wt.% Si, 0.15 - 0.4 wt.% Cu, 0.8 - 1.2 wt.% Mg, and 0.04 - 0.35 wt.% Cr; and a coating layer comprising the balance Al and 1.5 - 4.5 wt.% Si, 0.15 - 0.4 wt.% Cu, 0.4 - 1.2 wt.% Mg, and 0.04 - 0.35 wt.% Cr.

2. The coated foil according to claim 1, wherein the trace elements in the composition of the core and the coating layer include 0 - 0.3 wt.% Fe, 0 - 0.1 wt.% Mn, 0 - 0.25 wt.% Zn, 0 - 0.15 wt.% Ti, and any other elements in an amount less than 0.05 wt.%, and the total amount of all other elements is less than 0.15 wt.%.

3. The coated foil according to claim 1, wherein the thickness of each foil is between 25 µm and 1000 µm.

4. The coated foil according to claim 1, wherein the core is the first layer of the foil and the coating layer is the second layer of the foil.

5. The coated foil according to claim 1, wherein the first layer forms the first coating layer of the foil, the second layer forms the core of the foil, and the third layer forms the second coating layer of the foil.

6. The coated foil according to claim 1, wherein the coating layer accounts for 8% to 45% of the total thickness of the coated foil.

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