Method for preparing a large mold blank for isothermal forging

Abstract

Method for preparing a large mold blank (6) for isothermal forging, characterized in that the method comprises the following steps: Preparing several plate-shaped base elements (1) from a titanium-zirconium-molybdenum alloy with a thickness of 20 to 100 mm based on a predetermined shape; Preparing several foil-shaped intermediate layers (2) of a metallic niobium-tungsten alloy or tantalum-tungsten alloy with a thickness of 40 to 150 micrometers based on a predetermined shape; Assembling the plate-shaped base elements (1) made of titanium-zirconium-molybdenum alloy and the foil-shaped intermediate layers (2) successively to form an assembly body based on a predetermined design, such that the foil-shaped intermediate layers (2) are clamped in the assembly body (3) between plate-shaped base elements (1) made of titanium-zirconium-molybdenum alloy; Exposing the assembly body (3) to an axial pressure of 6 to 9 MPa for a bonding duration of at least 3 hours using a vacuum diffusion furnace (11) under the conditions of a bonding temperature that is 20 to 100°C lower than the recrystallization temperature of the titanium-zirconium-molybdenum alloy and a vacuum level of 10-3 to 10-2 Pa, so that diffusion bonding of the plate-shaped base elements (1) made of titanium-zirconium-molybdenum alloy and the foil-shaped intermediate layer (2) takes place to obtain a primary blank (4); Subsequently, the primary blank (4) is subjected to a homogenization treatment with a homogenization duration of 2 to 24 hours under conditions of a homogenization temperature that is 50 to 150 °C lower than the recrystallization temperature of the titanium-zirconium-molybdenum alloy, a vacuum or protection by inert gas in order to homogenize the tissue and composition of the interface in the primary blank (4); Cooling the primary blank (4) after the homogenization treatment to obtain the mold blank (6); where the recrystallization temperature of the titanium-zirconium-molybdenum alloy is 1350°C to 1400°C.

Description

Technical field

[0001] The present invention relates to a method for producing metal materials, specifically to a method for preparing a large mold blank for isothermal forging, and more particularly to a method for preparing a titanium-zirconium-molybdenum alloy mold blank for isothermal forging. State of the art

[0002] Isothermal forging is particularly suitable for the precision forming of difficult-to-form materials with a narrow forging temperature range, low plasticity, and high deformation resistance, such as titanium alloys, nickel-based high-temperature alloys, and other alloys. However, since molds for isothermal forging must operate at high temperatures and exhibit higher flow stress than formed parts, higher requirements are placed on the high-temperature performance of the mold materials. Currently, the working temperature of the mold cavity in isothermal forging of nickel-based high-temperature alloys and titanium alloys is usually between 700°C and 1200°C. Within this temperature range, the mold must exhibit high strength and hardness, good wear resistance, and sufficient toughness.

[0003] A titanium-zirconium-molybdenum alloy (abbreviated to TZM alloy) is an alloy based on molybdenum (Mo) with a small amount of titanium (Ti), zirconium (Zr), and carbon (C). It has a higher recrystallization temperature (1350°C–1400°C) than metallic molybdenum and possesses better high-temperature mechanical and corrosion properties. Therefore, as an important high-temperature structural material, titanium-zirconium-molybdenum alloy is well-suited for the production of high-temperature molds for isothermal forging. However, due to the high melting point of titanium-zirconium-molybdenum alloys (approximately 2640°C), melting or powder metallurgical preparation of larger titanium-zirconium-molybdenum alloys is more difficult, and coarse crystals and component segregation may occur.Furthermore, due to the high resistance of titanium-zirconium-molybdenum alloys to high-temperature deformation, it becomes more difficult to refine the crystal grains in large blanks and to modify large blanks through hot working processes such as forging and rolling. Large blanks tend to exhibit uneven texture and chemical composition. The mechanical properties of the blank also show a significant downward trend with increasing blank size.

[0004] In the preparation of large metal materials, existing methods propose to stack several small primitives in a predetermined shape, and then each small primitive is encapsulated by electron beam welding to achieve a vacuum state between the primitives.

[0005] Through large-scale deformation (upsetting) and high-temperature insulation, each small basic element can achieve interlayer diffusion and forging and welding between the layers. Multiple basic elements are finally forged and welded together to form a large metal blank. For example, Chinese patent applications CN 1 05 598 327 A "Forming Method for Layered Multi-Row Stacked Metal Structures," CN 1 07 717 341 A "Forming Method for Modular Metal Structures," CN 1 07 876 674 A "Forming Method for Hierarchical Metal Structures," and CN 1 05 522 349 A "Forming Method for Homogeneous Metal Structures" are all methods that utilize the construction and forming process to forge and weld multiple small basic elements into large metal parts.However, titanium-zirconium-molybdenum alloy, as a difficult-to-work alloy with a high melting point, exhibits high deformation resistance at high temperatures and is difficult to achieve large-scale forging deformation, that is, it is difficult to achieve upsetting. Therefore, for titanium-zirconium-molybdenum alloy, it is more difficult to achieve interfacial diffusion between the layers in each small unit by applying pressure at high temperatures, and it is more difficult to achieve a good forging and welding bond between the units for each layer. Meanwhile, the welding performance of titanium-zirconium-molybdenum alloy is poor, and it is difficult to obtain welds with better performance by electron beam welding.The high temperatures generated during electron beam welding and packaging processes can also significantly alter the texture and properties of titanium-zirconium-molybdenum alloys. Electron beam welding also increases process complexity and manufacturing costs. Furthermore, titanium-zirconium-molybdenum alloys exhibit high-temperature properties that make them prone to oxidation and volatilization under high-temperature conditions. The conventional forge-welded construction process in the atmosphere is not suitable for titanium-zirconium-molybdenum alloys. Therefore, the aforementioned construction and forming process based on forging and welding is not suitable for titanium-zirconium-molybdenum alloys, and it is necessary to develop methods suitable for the preparation of large-format titanium-zirconium-molybdenum alloy materials.

[0006] Further publications concerning the joining of components made of titanium-zirconium-molybdenum alloy are DE 15 27 326 A and US 4 331 902 A. Content of the invention

[0007] In view of the above-mentioned problems of the prior art, the present application provides an additive preparation method for isothermal forging of large-sized mold blanks, which effectively reduces the effects of the uneven tissue, composition and performance of titanium-zirconium-molybdenum alloy blanks on the service performance of large-sized alloys, which is particularly suitable for the production of large-sized mold blanks made of titanium, zirconium and molybdenum.

[0008] To achieve the above-mentioned objectives, the present application provides a method for preparing large blanks for isothermal forging, comprising the following steps: - Preparing several plate-shaped base elements made of a titanium-zirconium-molybdenum alloy with a thickness of 20 to 100 mm based on a given shape; - Preparing several foil-shaped intermediate layers of a metallic niobium-tungsten alloy or tantalum-tungsten alloy with a thickness of 40 to 150 micrometers based on a given shape; - assembling the plate-shaped base elements made of titanium-zirconium-molybdenum alloy and the foil-shaped intermediate layers one after the other to form an assembly body based on a predetermined configuration, so that the foil-shaped intermediate layer is clamped in the assembly body between plate-shaped base elements made of titanium-zirconium-molybdenum alloy; - subjecting the assembly body to an axial pressure of 6 to 9 MPa for a joining time of at least 3 hours using a vacuum diffusion (welding) furnace under the conditions of a joining temperature 20 to 100°C lower than the recrystallization temperature of the titanium-zirconium-molybdenum alloy and a vacuum degree of 10-3 to 10-2 Pa, so that a diffusion bonding of the plate-shaped base elements made of titanium-zirconium-molybdenum alloy and the foil-shaped intermediate layer takes place to obtain a primary blank; - subjecting the primary blank to a homogenisation treatment with a homogenisation duration of 2 to 24 hours under conditions of a homogenisation temperature 50 to 150 °C lower than the recrystallisation temperature of the titanium-zirconium-molybdenum alloy, a vacuum or an inert gas protection in order to homogenise the tissue and the composition of the joining interface in the primary blank; - Cooling of the primary blank after the homogenization treatment to obtain the mold blank.

[0009] By using diffusion bonding technology, a foil-shaped material made of a niobium-tungsten alloy or a tantalum-tungsten alloy is used as an interlayer to increase the homogenization process, improve the design and forming process, and realize the preparation of large mold blanks made of a titanium-zirconium-molybdenum alloy.Without being bound by any theory, it is believed that the additive preparation method according to the present application promotes the interdiffusion between the molybdenum element of the plate-shaped base member made of titanium-zirconium-molybdenum alloy and the metal element of the foil-shaped intermediate layer, whereby a diffusion layer is formed at the connection interface between the base member and the intermediate layer, and the connection of a plurality of base members is effectively realized by the foil-shaped intermediate layer, thereby enabling the preparation of large-sized titanium-zirconium-molybdenum alloy mold blanks with the design and forming process.Furthermore, since the temperatures of the diffusion bonding and the homogenization treatment of the present application are both lower than the recrystallization temperature of the titanium-zirconium-molybdenum alloy, the additive preparation method of the present application does not cause any significant changes to the texture and properties of the titanium-zirconium-molybdenum alloy plate-shaped base member.

[0010] In a possible implementation of the present application, it is provided that when preparing a plurality of plate-shaped base members made of titanium-zirconium-molybdenum alloy with a thickness of 30 to 100 mm, the plate-shaped base members made of titanium-zirconium-molybdenum alloy are mechanically machined, pre-ground and polished so that the roughness Ra of the connecting surface between the plate-shaped base member made of titanium-zirconium-molybdenum alloy and the foil-shaped intermediate layer is 0.4 to 0.8, and that the parallelism between each connecting surface and the pressure surface subjected to axial pressure of the plate-shaped base member made of titanium-zirconium-molybdenum alloy is less than 0.02 mm.

[0011] In a possible implementation of the present application, it is envisaged that the niobium-tungsten alloy or tantalum-tungsten alloy is Nb-(2-10) W or Ta-(2-10) W (wt%).

[0012] From the above, by further defining the foil-shaped intermediate layer, it is advantageous to form a good interdiffusion between the foil-shaped intermediate layer and the plate-shaped base member made of titanium-zirconium-molybdenum alloy, thereby further improving the performance of the mold at high temperatures.

[0013] In a possible implementation of the present application, it is provided that when preparing several foil-shaped intermediate layers made of a niobium-tungsten alloy or a tantalum-tungsten alloy with a thickness of 60 to 80 micrometers, the foil-shaped intermediate layers are soaked with 10 wt.% hydrochloric acid for 10 minutes, and then the foil-shaped intermediate layers are cleaned with alcohol or acetone by means of ultrasound.

[0014] From the above, by further restricting the preparation of the plate-shaped base member made of titanium-zirconium-molybdenum alloy and the foil-shaped intermediate layer, a certain parallelism is ensured between the surfaces to be joined and between the joining surface and the pressing surface, and the surfaces to be joined have a certain roughness and cleanliness, which is conducive to improving the joining quality between the base member and the intermediate layer, so that the performance of the mold at high temperatures is improved.

[0015] In a possible implementation of the present application, it is provided that the joining temperature is at a temperature that is 20 to 60 °C lower than the recrystallization temperature of the titanium-zirconium-molybdenum alloy, the axial pressure is 7 to 9 MPa, and the joining time is 3 to 6 hours.

[0016] In a possible implementation of the present application, it is provided that the homogenization temperature is 80 to 150 °C lower than the recrystallization temperature of the titanium-zirconium-molybdenum alloy, the homogenization time being 5 to 12 hours.

[0017] In a possible implementation of the present application, it is provided that during the cooling of the primary blank after the homogenization treatment, the primary blank is cooled at a cooling rate of 2 to 6 °C / min from the homogenization temperature to 1000 °C and at a cooling rate of 10 to 15 °C / min from 1000 °C to 500 °C.

[0018] In a possible implementation of the present application, it is provided that during the cooling of the primary blank after the homogenization treatment, the primary blank is kept at a temperature of 500 °C for one hour after cooling to 500 °C in order to eliminate the stresses caused by the cooling.

[0019] From the above, by further limiting the process parameters such as joining temperature, axial joining pressure, joining time, homogenization temperature, homogenization time, cooling rate and the like, it is advantageous to further promote the interdiffusion of molybdenum elements between the titanium-zirconium-molybdenum alloy base member and the foil-shaped intermediate layer and the metal elements of the intermediate layer, thereby further increasing the molybdenum content of the intermediate layer, thereby further improving the high-temperature performance of the mold.

[0020] In one possible implementation of the present application, the homogenization and cooling processes are performed in a vacuum diffusion furnace. In other words, the homogenization and subsequent controlled cooling can be performed directly after pressure bonding by adjusting the temperature of the vacuum diffusion furnace.

[0021] In one possible implementation of the present application, the homogenization and cooling processes are performed in a vacuum furnace or an atmosphere-protection furnace. In other words, it is necessary to wait until the vacuum diffusion furnace has cooled down to remove the lead, and then the subsequent homogenization and controlled cooling process must be completed in the vacuum furnace or atmosphere-protection furnace. This method can shorten the service life of the vacuum diffusion furnace and improve production efficiency.

[0022] The above content of the present application will become more concise and understandable in the following description of several embodiments with reference to the accompanying drawings. Description of the characters

[0023] The drawings of the present application are provided below. These drawings are provided solely for the purpose of illustrating the present application in a more intuitive form. They are exemplary and are not intended to limit the scope of the present application. Fig. 1 is a schematic structural diagram of a mounting body according to an embodiment of the present application; Fig. 2 is a schematic diagram of a diffusion connection according to an embodiment of the present application; Fig. 3 is a schematic diagram of a homogenization treatment according to an embodiment of the present application; Fig. 4 is a schematic structural diagram of a mold blank according to an embodiment of the present application. Concrete embodiments

[0024] To facilitate understanding of the present application, the present application will be described in more detail below in connection with specific embodiments. The experimental methods described in this application are normal methods unless otherwise noted. Unless otherwise noted, the materials described are commercially available. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which one has ordinary skill in the art belongs. In case of any discrepancy, the meaning explained in this specification or the meaning derived from the content recorded in this specification shall prevail. Furthermore, the terms used herein are only for describing embodiments of the present application and are not intended to limit the present application.

[0025] In order to accurately describe the technical content of the present application and to accurately understand the present invention, the following explanations or definitions are given to the words and terms used in this specification before describing the specific embodiments.

[0026] The word "an embodiment" or "an embodiment" as used in this specification means that a particular feature, step, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. Therefore, the phrases "in an embodiment" or "in the embodiment" that appear at various points in this specification do not necessarily all refer to the same embodiment, but may. Moreover, each particular feature, step, or feature may be combined in any suitable manner in one or more embodiments, as one of ordinary skill in the art will recognize from the present application.

[0027] The term “vacuum diffusion furnace” as used in the description and claims refers to equipment capable of providing a vacuum environment for the workpiece while simultaneously applying pressure to the workpiece.

[0028] The term “vacuum heating furnace” as used in the description and claims refers to equipment capable of providing a vacuum environment for the workpiece.

[0029] The term “atmosphere protection furnace” as used in the description and claims refers to equipment capable of providing an inert gas environment to the workpiece.

[0030] The term "titanium-zirconium-molybdenum alloy," also known as TZM alloy, used in the description and claims, has a composition of 0.4 wt% to 0.55 wt% titanium, 0.06 wt% to 0.12 wt% zirconium, and 0.01 wt% to 0.04 wt% carbon. On the one hand, titanium and zirconium elements dissolve in the molybdenum matrix to distort the crystal lattice and thus achieve solid-solution strengthening of the titanium-zirconium-molybdenum alloy; on the other hand, titanium reacts with zirconium and carbon elements to form fine and dispersed TiC and ZrC particles to achieve second-phase strengthening.Due to the alloying effect, in addition to the properties of high melting point, small expansion coefficient, low vapor pressure and good electrical and thermal conductivity of metallic molybdenum, the TZM alloy has a higher recrystallization temperature (1350°C-1400°C), as well as better high-temperature resistant mechanical properties and corrosion properties.

[0031] The term "diffusion bonding" used in the description and claims refers to a process in which, under the influence of high temperature and high pressure, the surfaces to be joined are plastically deformed and brought into close contact, and interatomic interdiffusion occurs over a certain period of time to form a reliable bond. This process is particularly suitable for the preparation of connections with large joining surfaces and high requirements for dimensional accuracy and mechanical properties.

[0032] The term “isothermal forging” as used in the description and claims refers to a forging technique in which the forming tool and the formed part are at substantially the same temperature.

[0033] The term “design and forming” used in the description refers to an additive manufacturing process in which several smaller metal blanks are used as basic design elements to produce large metal blanks.

[0034] The word “axial direction” mentioned in the description and claims is the direction perpendicular to the contact surface between the plate-shaped base element made of titanium-zirconium-molybdenum alloy and the intermediate layer made of foil.

[0035] The technical solution of the present application is based on the Fig. 1 to 4 are described in detail.

[0036] Fig. 1 shows a mounting body 3 with a square cross-section according to an embodiment of the present application. As in Fig. 1, the mounting body 3 consists of four plate-shaped base elements 1 made of titanium-zirconium-molybdenum alloy and three foil-shaped intermediate layers 2, wherein the foil-shaped intermediate layers 2 are clamped between plate-shaped base elements 1 made of titanium-zirconium-molybdenum alloy. In this embodiment, each plate-shaped base element 1 made of titanium-zirconium-molybdenum alloy is prepared to have a uniform shape, and each foil-shaped intermediate layer 2 is prepared to have a uniform shape to form the mounting body 3 with such a cross-section.It should be understood that in other embodiments of the present application, each plate-shaped base member 1 made of titanium-zirconium-molybdenum alloy may be prepared to have inconsistent shapes, and / or each foil-shaped intermediate layer 2 may be prepared to have inconsistent shapes to form a cross-section of the desired shape, thereby producing a mounting body 3 with the desired configuration. For example, each plate-shaped base member 1 made of titanium-zirconium-molybdenum alloy and each foil-shaped intermediate layer 2 may be prepared in different shapes, so that the mounting body 3 may have a uniformly curved outline in the thickness direction from top to bottom.For example, some of the plate-shaped base elements 1 made of titanium-zirconium-molybdenum alloy and foil-shaped intermediate layers 2 can be prepared in hollow molds so that the assembly body 3 has a cavity, whereby the mold blank serving as a molding tool can use the cavity to prepare molded parts.

[0037] Fig. Figure 2 shows a schematic diagram of a diffusion bonding process according to an embodiment of the present application. After the assembly body 3 is placed in the vacuum diffusion furnace 11, the vacuum diffusion furnace 11 is started so that the temperature in the vacuum diffusion furnace 11 reaches a bonding temperature that is 20 to 100°C lower than the recrystallization temperature of the titanium-zirconium-molybdenum alloy, and the vacuum degree reaches 10-3 to 10-2 Pa. Then, the vacuum diffusion furnace 11 applies a pressure of 6 to 9 MPa to the assembly body 3 along the axial direction indicated by the arrow, maintaining the assembly body under this pressure for at least 3 hours. The produced primary blank 4 is then removed from the vacuum diffusion furnace 11.

[0038] It is understood that during the formation of the primary blank 4, a diffusion bond has already taken place between the plate-shaped base element 1 made of titanium-zirconium-molybdenum alloy and the foil-shaped intermediate layer 2, wherein the molybdenum element in the plate-shaped base element 1 made of titanium-zirconium-molybdenum alloy has diffused into the foil-shaped intermediate layer 2, while the metal element in the foil-shaped intermediate layer 2 has diffused into the plate-shaped base element 1 made of titanium-zirconium-molybdenum alloy, whereby a new intermediate structure 5 is formed between the plate-shaped base elements 1' made of titanium, zirconium and molybdenum (see Fig. 3). The intermediate structure 5 has a diffusion layer 7 at the connection interface and possibly a metal foil layer between the diffusion layers 7 (since in some other embodiments the molybdenum element completely penetrates the foil-shaped intermediate layer and forms a solid solution, in this case it is assumed that the foil-shaped intermediate layer 2 partially or completely disappears). Due to the formation of the new intermediate structure 5, it can be assumed from a microscopic point of view that the plate-shaped base element 1' made of titanium, zirconium, and molybdenum is thinner than the plate-shaped base element 1 made of titanium-zirconium-molybdenum alloy, while the metal foil layer is thinner than the foil-shaped intermediate layer 2.

[0039] Fig. Figure 3 shows a schematic diagram of a homogenization treatment according to an embodiment of the present application. After the primary blank 4 is placed in the vacuum furnace 12 or the atmosphere-protection furnace 13, the vacuum furnace 12 or the atmosphere-protection furnace 13 is started so that the vacuum degree of 10-3 to 10-2 Pa is reached, or the furnace is filled with inert gas, and the furnace temperature is adjusted to reach a homogenization temperature that is 50 to 150°C lower than the recrystallization temperature of the titanium-zirconium-molybdenum alloy. After reaching the homogenization temperature, this temperature is maintained for 2 to 24 hours to homogenize the tissue and composition at the bonding interface in the primary blank 4 and thus form the mold blank 6 (see Fig. 4).

[0040] Fig.4 shows a mold blank 6 according to an embodiment of the present application. The mold blank 6 consists of a plate-shaped base element 1' made of titanium, zirconium, and molybdenum and a diffusion layer 7. In the present embodiment, the primary blank 4 undergoes further interdiffusion during the homogenization process, whereby the metal foil layer originally remaining in the intermediate structure 5 completely disappears upon further interdiffusion. As a result, the intermediate structure 5 is converted into a diffusion layer 7 consisting of a solid molybdenum-titanium / niobium solution, thereby forming the mold blank 6.

[0041] In some embodiments of the present application, particularly those embodiments where a thicker niobium-tungsten alloy foil or tantalum-tungsten foil is used as the intermediate layer, a metal foil layer of a certain thickness remains in the mold blank 6. However, since niobium-tungsten and tantalum-tungsten are high-melting-point alloys with high high-temperature strength, the remaining metal foil layer will not significantly impair the high-temperature performance of the mold blank 6. Meanwhile, the formed diffusion layer is sufficient to impart the required mechanical properties to the mold blank 6 as a molding tool. Furthermore, particularly in embodiments where a thicker niobium-tungsten foil or tantalum-tungsten foil is used as the intermediate layer, the element distribution of the diffusion layer 7 is not uniform, and the molybdenum element is distributed in a concentration gradient.However, since the molybdenum element can improve the high-temperature performance of the intermediate layer, the gradient concentration distribution of the titanium element in the diffusion layer 7 will not significantly affect the high-temperature performance of the mold blank 6. Meanwhile, the formed diffusion layer is sufficient to impart the required mechanical properties to the mold blank 6 as a molding tool.

[0042] In summary, the present application offers the following advantages.

[0043] By adding niobium-tungsten foil or tantalum-tungsten foil as an intermediate layer, the present application solves the problems of high yield strength at high temperatures, high melting point, difficulty in plastic deformation of the bonding interface, and difficulty in diffusion of the titanium-zirconium-molybdenum alloy.

[0044] The present application solves the problem that large titanium-zirconium-molybdenum alloy blanks are difficult to prepare and exhibit uneven and poor performance by adding a specific intermediate layer, a homogenization process, and a cooling process based on the metal design process. Furthermore, in the present invention, the blank is homogenized after diffusion bonding, so that the elements in the intermediate layer and the molybdenum element of the titanium-zirconium-molybdenum alloy are fully interdiffused, and a distinct diffusion layer is formed at the bonding interface of the base elements, resulting in high bond strength.In addition, since the interlayer itself has high normal temperature and high temperature strength and is fully interdiffused with titanium-zirconium-molybdenum alloy elements, the bonding interface of each basic element of titanium, zirconium and molybdenum has high normal temperature and high temperature performance.

[0045] The bonding temperature of the present application is relatively low, 20 to 100 °C lower than the recrystallization temperature of the titanium-zirconium-molybdenum alloy. The structure and properties of plate-shaped base elements made of titanium-zirconium-molybdenum alloy do not change significantly after diffusion bonding.

[0046] The present application does not require welding of packages of each basic element by vacuum electron beam, the process is relatively simple and the manufacturing cost is low.

[0047] The present application reduces the requirements for diffusion bonding in terms of roughness, bonding temperature, bonding pressure, and heat retention time of the titanium-zirconium-molybdenum alloy bonding surface. The present application also avoids the problem of limited powder metallurgy equipment capabilities and high investment costs.

[0048] The shape of the basic elements of the present application can be designed according to the actual situation, and the additive diffusion manufacturing of solid, hollow and irregularly shaped blanks can be realized, and the process is flexible and adaptable.

[0049] Compared to current metal construction methods, the method of the present application is more suitable for the design and manufacture of refractory alloys and hard-to-work alloys with high melting points, such as molybdenum alloys, tungsten alloys and nickel-based alloys.

[0050] To simplify implementation, exemplary embodiments of the present application are described below. <Ausführungsbeispiel 1>

[0051] This example is an isothermally forged blank made of titanium, zirconium, and molybdenum for a blade made of a nickel-based high-temperature alloy with dimensions of 200 × 200 × 60 mm (length × width × thickness). The isothermally forged blank made of titanium, zirconium, and molybdenum consists of three pieces of plate-shaped base elements made of titanium-zirconium-molybdenum alloy with dimensions of 200 × 200 × 20 mm (length × width × thickness) and two pieces of Nb-10W foil with dimensions of 200 × 200 mm in length and width and 80 micrometers in thickness as the interlayers. Additive manufacturing by diffusion bonding is carried out in a vacuum diffusion furnace, and the diffusion homogenization treatment is carried out in a vacuum furnace. The specific steps are as follows: Step 1: Through mechanical machining, pre-grinding and polishing of plate-shaped base elements made of titanium-zirconium-molybdenum alloy, the bonding surface made of titanium-zirconium-molybdenum alloy is given a roughness of Ra 0.4 to 0.8, ensuring that the parallelism between the bonding surface of the titanium-zirconium-molybdenum alloy and the printing surface in contact with the print head of the vacuum diffusion furnace is less than 0.02 mm. Step 2: The film-shaped intermediate layer is soaked with 10 wt% hydrochloric acid for 10 minutes, rinsed with water, and then placed in alcohol or acetone for ultrasonic cleaning, then air-dried and set aside. Step 3: The titanium-zirconium-molybdenum alloy plate base elements and the Nb-10W foil interlayers processed in steps 1 and 2 are alternately assembled and stacked in five layers (three layers of titanium-zirconium-molybdenum alloy plates and two layers of foil interlayers) to form an assembly body. The niobium foil interlayer can be fixed to the titanium-zirconium-molybdenum alloy plate base elements by energy storage welding to prevent misalignment during assembly. Step 4: The assembly is placed in a vacuum diffusion furnace, and an axial pressure of 0.2 MPa is applied to the assembly to fix it. Evacuation then begins, and heating begins when the vacuum level reaches 2×10-3 Pa. In the first stage, the temperature is increased to 500°C at a rate of 15°C / min and held for 30 minutes to evaporate oil stains in the furnace and on the workpiece surface. In the second stage, the temperature is increased to 1000°C at a rate of 10°C / min and held for 15 minutes to uniform the temperature in the furnace. In the third stage, the temperature is increased to the diffusion bonding temperature of 1330°C at a rate of 5°C / minute.After the joining temperature of 1330°C is reached, the assembly body is subjected to an axial pressure of 9 MPa and kept warm for 6 hours to perform the diffusion bonding, thereby obtaining a primary blank. Step 5: After the heat preservation of the diffusion joint is completed, the temperature in the furnace is reduced to 1220°C, the axial pressure is removed and the heat preservation is carried out for 8 hours, and the homogenization treatment is carried out to eliminate the joint stress and the components and tissue at the joint interface are homogenized. Step 6: After homogenization and heat preservation are completed, cooling begins. During the cooling phase from 1200°C to 1000°C, the cooling rate is 2 to 6°C / minute; during the phase from 1000°C to 500°C, the cooling rate is 10 to 15°C / minute. When the temperature reaches 500°C, heat preservation is carried out for 1 hour at this temperature to perform annealing and stress relief. After the stress is relieved and cooled to room temperature in the furnace, the titanium-zirconium-molybdenum alloy blank is obtained. <Ausführungsbeispiel 2>

[0052] This example is an isothermally forged blank made of titanium, zirconium, and molybdenum for a nickel-based high-temperature alloy impeller with dimensions of 500×500×200 mm (length×width×thickness). The isothermally forged blank made of titanium, zirconium, and molybdenum consists of four pieces of plate-shaped base elements made of titanium-zirconium-molybdenum alloy with dimensions of 500×500×50 mm (length×width×thickness) and three pieces of Ta-2.5W foil with dimensions of 500×500 mm and a thickness of 60 micrometers as the interlayers. Additive manufacturing by diffusion bonding is carried out in a vacuum diffusion furnace, and the diffusion homogenization treatment is carried out in a vacuum furnace. The specific steps are as follows: Step 1: Through mechanical machining, pre-grinding and polishing of plate-shaped base elements made of titanium-zirconium-molybdenum alloy, the bonding surface made of titanium-zirconium-molybdenum alloy is given a roughness of Ra 0.4 to 0.8, ensuring that the parallelism between the bonding surface of the titanium-zirconium-molybdenum alloy and the printing surface in contact with the print head of the vacuum diffusion furnace is less than 0.02 mm. Step 2: The film-shaped intermediate layer is soaked with 10 wt% hydrochloric acid for 10 minutes, rinsed with water, and then placed in alcohol or acetone for ultrasonic cleaning, then air-dried and set aside. Step 3: The titanium-zirconium-molybdenum alloy plate base elements and the Ta-2.5W foil interlayers processed in steps 1 and 2 are alternately assembled and stacked in seven layers (four layers of titanium-zirconium-molybdenum alloy plates and three layers of foil interlayers) to form an assembly body. The niobium foil interlayer can be fixed to the titanium-zirconium-molybdenum alloy plate base elements by energy storage welding to prevent misalignment during assembly. Step 4: The assembly is placed in a vacuum diffusion furnace, and an axial pressure of 0.2 MPa is applied to the assembly to fix it. Evacuation then begins, and heating begins when the vacuum level reaches 2×10-3 Pa. In the first stage, the temperature is increased to 500°C at a rate of 15°C / min and held for 30 minutes to evaporate oil stains in the furnace and on the workpiece surface. In the second stage, the temperature is increased to 1000°C at a rate of 10°C / min and held for 15 minutes to uniform the temperature in the furnace. In the third stage, the temperature is increased to the diffusion bonding temperature of 1300°C at a rate of 5°C / minute. After the joining temperature of 1330°C is reached, the assembly body is subjected to an axial pressure of 7 MPa, kept warm for 5 hours and then bonded by diffusion.After the heat preservation for diffusion bonding is completed, the primary blank is removed from the furnace under air cooling to room temperature. Step 5: The primary blank is placed in the atmospheric furnace, purged with nitrogen for protection, and then heated to raise the temperature. The furnace temperature is increased to 1250°C and held for 12 hours for homogenization. Step 6: After homogenization and heat preservation are completed, cooling begins. During the cooling phase from 1250°C to 1000°C, the cooling rate is 2 to 6°C / minute; during the phase from 1000°C to 500°C, the cooling rate is 10 to 15°C / minute. When the temperature reaches 500°C, heat preservation is carried out for 1 hour at this temperature to perform annealing and stress relief. After the stress is relieved and cooled to room temperature in the furnace, the mold blank made of titanium, zirconium, and molybdenum is obtained. <Ausführungsbeispiel 3>

[0053] This example is an isothermally forged blank made of titanium, zirconium, and molybdenum for a titanium alloy compressor disk with dimensions of 400 × 400 × 160 mm (length × width × thickness). The isothermally forged blank made of titanium, zirconium, and molybdenum consists of four pieces of plate-shaped base elements made of titanium-zirconium-molybdenum alloy with dimensions of 400 × 400 × 40 mm (length × width × thickness) and three pieces of Ta-10W foil with dimensions of 400 × 400 mm in length and width and 60 micrometers in thickness as the interlayers. Additive manufacturing by diffusion bonding is carried out in a vacuum diffusion furnace, and the diffusion homogenization treatment is carried out in a vacuum furnace. The specific steps are as follows: Step 1: Through mechanical machining, pre-grinding and polishing of plate-shaped base elements made of titanium-zirconium-molybdenum alloy, the bonding surface made of titanium-zirconium-molybdenum alloy is given a roughness of Ra0.4 to 0.8, ensuring that the parallelism between the bonding surface of the titanium-zirconium-molybdenum alloy and the printing surface in contact with the print head of the vacuum diffusion furnace is less than 0.02 mm. Step 2: The film-shaped intermediate layer is soaked with 10 wt% hydrochloric acid for 10 minutes, rinsed with water, and then placed in alcohol or acetone for ultrasonic cleaning, then air-dried and set aside. Step 3: The titanium-zirconium-molybdenum alloy plate base elements and the Ta-10W foil interlayers processed in steps 1 and 2 are alternately assembled and stacked in seven layers (four layers of titanium-zirconium-molybdenum alloy plates and three layers of foil interlayers) to form an assembly body. The titanium foil interlayer can be fixed to the titanium-zirconium-molybdenum alloy plate base elements by energy storage welding to prevent misalignment during assembly. Step 4: The assembly is placed in a vacuum diffusion furnace, and an axial pressure of 0.2 MPa is applied to the assembly to fix it. Evacuation then begins, and heating begins when the vacuum level reaches 2×10-3 Pa. In the first stage, the temperature is increased to 500°C at a rate of 15°C / min and held for 30 minutes to evaporate oil stains in the furnace and on the workpiece surface. In the second stage, the temperature is increased to 1000°C at a rate of 10°C / min and held for 15 minutes to uniform the temperature in the furnace. In the third stage, the temperature is increased to the diffusion bonding temperature of 1300°C at a rate of 5°C / minute.After the joining temperature of 1300°C is reached, the assembly body is subjected to an axial pressure of 6 MPa, kept hot for 3 hours and then bonded by diffusion to obtain a primary blank. Step 5: After the heat preservation of the diffusion joint is completed, the temperature in the furnace is reduced to 1220°C, the axial pressure is removed and the heat preservation is carried out for 10 hours, and the homogenization treatment is carried out to eliminate the joint stress and the homogenization treatment for the components and the tissue at the joint interface is carried out. Step 6: After homogenization and heat preservation are completed, cooling begins. During the cooling phase from 1220°C to 1000°C, the cooling rate is 2 to 6°C / minute; during the phase from 1000°C to 500°C, the cooling rate is 10 to 15°C / minute. When the temperature reaches 500°C, heat preservation is carried out for 1 hour at this temperature to perform annealing and stress relief. After the stress is relieved and cooled to room temperature in the furnace, the mold blank made of titanium, zirconium, and molybdenum is obtained. <Nicht erfindungsgemäßes Beispiel 4>

[0054] This example is an isothermally forged blank made of titanium, zirconium, and molybdenum for a titanium alloy impeller disk with dimensions of φ300×150 mm (length×width×thickness). The isothermally forged blank made of titanium, zirconium, and molybdenum uses three plate-shaped base elements made of titanium-zirconium-molybdenum alloy with a size of φ300×50 mm and two tantalum foils with a diameter of φ300 mm and a thickness of 40 micrometers as an interlayer. Additive manufacturing by diffusion bonding is carried out in a vacuum diffusion furnace, and the diffusion homogenization treatment is carried out in a vacuum furnace. The specific steps are as follows: Step 1: Through mechanical machining, pre-grinding and polishing of plate-shaped base elements made of titanium-zirconium-molybdenum alloy, the bonding surface made of titanium-zirconium-molybdenum alloy is given a roughness of Ra0.4 to 0.8, ensuring that the parallelism between the bonding surface of the titanium-zirconium-molybdenum alloy and the printing surface in contact with the print head of the vacuum diffusion furnace is less than 0.02 mm. Step 2: The film-shaped intermediate layer is soaked with 10 wt% hydrochloric acid for 10 minutes, rinsed with water, and then placed in alcohol or acetone for ultrasonic cleaning, then air-dried and set aside. Step 3: The titanium-zirconium-molybdenum alloy plate base elements and the tantalum foil interlayers processed in steps 1 and 2 are alternately assembled and stacked in five layers (three layers of titanium-zirconium-molybdenum alloy plates and two layers of foil interlayers) to form an assembly body. The titanium foil interlayer can be fixed to the titanium-zirconium-molybdenum alloy plate base elements by energy storage welding to prevent misalignment during assembly. Step 4: The assembly is placed in a vacuum diffusion furnace, and an axial pressure of 0.2 MPa is applied to the assembly to fix it. Evacuation then begins, and heating begins when the vacuum level reaches 2×10-3 Pa. In the first stage, the temperature is increased to 500°C at a rate of 15°C / min and held for 30 minutes to evaporate oil stains in the furnace and on the workpiece surface. In the second stage, the temperature is increased to 1000°C at a rate of 10°C / min and held for 15 minutes to uniform the temperature in the furnace. In the third stage, the temperature is increased to the diffusion bonding temperature of 1320°C at a rate of 5°C / minute.After the joining temperature of 1320°C is reached, the assembly body is subjected to an axial pressure of 6 MPa, kept warm for 3 hours and then bonded by diffusion to obtain a primary blank. Step 5: After the heat preservation of the diffusion bond is completed, the temperature in the furnace is reduced to 1200°C, the axial pressure is removed and the heat preservation is carried out for 12 hours, and the homogenization treatment is carried out to eliminate the bonding stress and the homogenization treatment for the components and the tissue at the bonding interface is carried out. Step 6: After homogenization and heat preservation are completed, cooling begins. During the cooling phase from 1200°C to 1000°C, the cooling rate is 2 to 6°C / minute; during the phase from 1000°C to 500°C, the cooling rate is 10 to 15°C / minute. When the temperature reaches 500°C, heat preservation is carried out for 1 hour at this temperature to perform annealing and stress relief. After the stress is relieved and cooled to room temperature in the furnace, the mold blank made of titanium, zirconium, and molybdenum is obtained.

[0055] The above examples 1 to 3 are merely preferred embodiments of the present application and the technical principles employed. Those skilled in the art will understand that the present application is not limited to the specific embodiments described herein, and that those skilled in the art may make various obvious changes, adjustments, and substitutions without departing from the scope of the present application. Therefore, although the present application has been described in detail with reference to the above embodiments, the present application is not limited to the above embodiments. Without departing from the concept of the present application, it may also include other equivalent embodiments, all of which are intended to be within the scope of the present application.

Claims

[1] Method for preparing a large blank (6) for isothermal forging, characterized by that the procedure comprises the following steps: Preparing a plurality of plate-shaped base elements (1) made of a titanium-zirconium-molybdenum alloy with a thickness of 20 to 100 mm based on a predetermined shape; Preparing a plurality of foil-shaped intermediate layers (2) made of a metallic niobium-tungsten alloy or tantalum-tungsten alloy with a thickness of 40 to 150 micrometers based on a predetermined shape; Assembling the plate-shaped base elements (1) made of titanium-zirconium-molybdenum alloy and the foil-shaped intermediate layers (2) one after the other to form an assembly body based on a predetermined design, so that the foil-shaped intermediate layers (2) are clamped in the assembly body (3) between plate-shaped base elements (1) made of titanium-zirconium-molybdenum alloy; Subjecting the assembly body (3) to an axial pressure of 6 to 9 MPa for a joining time of at least 3 hours using a vacuum diffusion furnace (11) under the conditions of a joining temperature which is 20 to 100°C lower than the recrystallization temperature of the titanium-zirconium-molybdenum alloy and a vacuum degree of 10-3 to 10-2 Pa, so that a diffusion bonding of the plate-shaped base elements (1) made of titanium-zirconium-molybdenum alloy and the foil-shaped intermediate layer (2) takes place in order to obtain a primary blank (4); subsequently subjecting the primary blank (4) to a homogenization treatment with a homogenization time of 2 to 24 hours under the conditions of a homogenization temperature which is 50 to 150 °C lower than the recrystallization temperature of the titanium-zirconium-molybdenum alloy, a vacuum or protection by inert gas in order to homogenize the tissue and the composition of the connection interface in the primary blank (4); Cooling the primary blank (4) after the homogenization treatment to obtain the mold blank (6); The recrystallization temperature of the titanium-zirconium-molybdenum alloy is 1350°C to 1400°C. [2] A method of preparation according to claim 1, characterized bythat in the preparation of a plurality of plate-shaped base elements (1) made of titanium-zirconium-molybdenum alloy with a thickness of 20 to 100 mm, the plate-shaped base elements (1) made of titanium-zirconium-molybdenum alloy are mechanically machined, pre-ground and polished so that the roughness Ra of the connecting surface between the plate-shaped base element (1) made of titanium-zirconium-molybdenum alloy and the foil-shaped intermediate layer (2) is 0.4 to 0.8, and that the parallelism between each connecting surface and the pressure surface subjected to axial pressure of the plate-shaped base element (1) made of titanium-zirconium-molybdenum alloy is less than 0.02 mm. [3] A method of preparation according to claim 1, characterized by that the tantalum is pure tantalum with a purity of ≥99.5% and the niobium-tungsten alloy or tantalum-tungsten alloy is Nb-(2-10) W or Ta-(2-10) W (wt%). [4] A method of preparation according to claim 1, characterized by that in the preparation of several foil-shaped intermediate layers (2) made of pure tantalum, niobium-tungsten alloy or tantalum-tungsten alloy with a thickness of 60 to 80 micrometers, the foil-shaped intermediate layers (2) are impregnated with 10 wt.% hydrochloric acid for 10 minutes, and then the foil-shaped intermediate layers (2) are cleaned with alcohol or acetone by means of ultrasound. [5] A method of preparation according to claim 1, characterized by that the joining temperature is 20 to 60 °C lower than the recrystallization temperature of the titanium-zirconium-molybdenum alloy, the axial pressure is 7 to 9 MPa and the joining time is 3 to 6 hours. [6] A method of preparation according to claim 1, characterized bythat the homogenization temperature is 80 to 150 °C lower than the recrystallization temperature of the titanium-zirconium-molybdenum alloy, with the homogenization time being 5 to 12 hours. [7] A method of preparation according to claim 1, characterized by that the primary blank (4) is cooled during the cooling of the primary blank (4) after the homogenization treatment at a cooling rate of 2 to 6 °C / min from the homogenization temperature to 1000 °C and at a cooling rate of 10 to 15 °C / min from 1000 °C to 500 °C. [8] A method of preparation according to claim 7, characterized by that the primary blank (4) is kept at a temperature of 500 °C for one hour after cooling to 500 °C during the cooling of the primary blank (4) after the homogenization treatment in order to eliminate the stress caused by the cooling.

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