A molybdenum matrix composite heating band material for vacuum isothermal forging and a method for manufacturing the same
By preparing a molybdenum-based composite heating strip material and combining it with a multi-component composite carbide and ceramic fiber to form a three-dimensional reinforcing network, the problems of grain growth and reduced plasticity of molybdenum strips during vacuum isothermal forging were solved, thereby improving high-temperature toughness and service life.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- BEIJING RESEARCH INSTITUTE OF MECHANICAL & ELECTRICAL TECHNOLOGY CO LTD CAM
- Filing Date
- 2026-06-18
- Publication Date
- 2026-07-31
AI Technical Summary
Existing molybdenum strips, due to grain growth and mechanical contact during vacuum isothermal forging, exhibit reduced plasticity, making them prone to cracking and limiting their service life. Furthermore, existing grain refiners reduce recrystallization control at high temperatures, failing to guarantee stable mechanical properties.
A molybdenum-based composite heating band material was prepared by mixing molybdenum powder, titanium source, tungsten source, zirconium source, carbon source, lanthanum oxide, and short-cut ceramic fibers through powder metallurgy. The material was then combined with long-cut ceramic fibers to form a multi-scale three-dimensional reinforcement network, which inhibited recrystallization and grain growth and enhanced high-temperature toughness.
It effectively inhibits recrystallization and grain growth of the molybdenum matrix, improves high-temperature toughness and thermal shock resistance, extends service life, and ensures stable mechanical properties.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of manufacturing high-end molybdenum alloy heating belt materials for vacuum isothermal forging equipment, specifically to a molybdenum matrix composite heating belt material for vacuum isothermal forging and its preparation method. Background Technology
[0002] Vacuum isothermal forging operates in environments characterized by vacuum, high temperature, and heavy load. In actual production, the operating temperature can reach 1300℃ or even higher, placing high demands on high-temperature heaters. Currently, common heating element materials include nickel-iron alloys (≤600℃), nickel-chromium alloys (600-1000℃), iron-chromium-aluminum alloys (1100-1400℃), silicon carbide / molybdenum disilicide (1400-1800℃), tungsten, molybdenum, and graphite (≥1800℃).
[0003] Currently, in response to the equipment's usage requirements and actual production needs, the equipment uses molybdenum alloy strip as a high-temperature heating element. However, during repeated heating, the grains of the molybdenum strip will continuously grow, even to the point of being visible to the naked eye. The coarsening of the grains will have an adverse effect on its mechanical properties, especially its plasticity. Vibration occurs during the forging process and during the assembly and disassembly of the mold, and impacts may also occur due to mechanical contact. Once the plasticity of the molybdenum strip decreases to a certain extent, it is prone to cracking, thus limiting its service life.
[0004] To address the aforementioned issues, existing technologies employ powder metallurgy combined with forging and rolling to prepare thin strips. During the powder mixing process, lanthanum oxide is added as a grain refiner (second phase) to refine the grain structure and improve performance, thereby increasing the recrystallization temperature. The typical addition content is 2-2.5%. However, after repeated heating at 1600℃ or at low temperatures, lanthanum oxide reduces its control over recrystallization, leading to a decrease in the recrystallization temperature of the molybdenum-lanthanum alloy and compromising the stability of its mechanical properties. Summary of the Invention
[0005] The purpose of this invention is to provide a molybdenum-based composite heating belt material for vacuum isothermal forging and its preparation method, so as to solve the technical problems in the prior art.
[0006] To solve the above-mentioned technical problems, the present invention specifically provides the following technical solution: A method for preparing a molybdenum-based composite heating belt material for vacuum isothermal forging includes the following steps: S100. Molybdenum powder, titanium source, tungsten source, zirconium source, carbon source, lanthanum oxide, and short-cut ceramic fibers are mixed to obtain composite powder. S200. A molybdenum alloy rod containing second-phase particles and the chopped ceramic fibers is obtained through powder metallurgy. During the sintering process, tungsten, titanium, zirconium react with carbon to generate multi-component complex carbide particles, while titanium and zirconium react with residual oxygen to generate oxide particles. S300. The bar is forged and extruded to form a billet with a grain size ≤50μm, and then rolled into a plate with a width of 300-600mm. A circular arc groove is cut on the surface of the plate. S400. Long-cut ceramic fibers are laid in the arc groove, and then the long-cut ceramic fibers are embedded into the plate through mechanical interlocking by small deformation pressing or rolling. The long-cut ceramic fibers are oriented along the rolling direction. The short-cut fibers randomly distributed in three dimensions inside the material and the oriented interlocking long fibers on the surface together form a multi-scale three-dimensional reinforcement network to obtain a molybdenum alloy composite material. S500: Anneal the molybdenum alloy composite material to stabilize its microstructure.
[0007] Furthermore, the long-cut ceramic fiber or the short-cut ceramic fiber is any one or more of alumina and titanium carbonitride; To address the aforementioned technical problems, the present invention further provides the following technical solution: A molybdenum-based composite heating belt material for vacuum isothermal forging, the material comprising: The materials include: Molybdenum matrix; The second phase particles are dispersed in the molybdenum matrix, and the second phase particles include at least one of TiC, WC, ZrC, and lanthanum oxide, and at least one of (Ti,Mo,W)C and (Zr,Mo,W)C multi-component complex carbides generated by in-situ reaction; The particle size of the second phase particles is 10 nm to 500 nm; Short-cut ceramic fibers uniformly distributed within the molybdenum matrix; Long-cut ceramic fibers are oriented along the length direction in the molybdenum matrix, and a mechanical interlocking interface is formed between the long-cut ceramic fibers and the molybdenum matrix; In this structure, the second phase particles and the long-cut ceramic fibers form a heterogeneous structure in the molybdenum matrix, which synergistically inhibits the recrystallization and grain growth of the molybdenum matrix through the pinning effect of the second phase. At the same time, Ti and Zr elements preferentially combine with oxygen impurities to purify the matrix and reduce the ductile-brittle transition temperature of the matrix. The short-cut ceramic fibers and the long-cut ceramic fibers together form a three-dimensional reinforcing network to improve the high-temperature toughness and thermal shock resistance of the molybdenum matrix.
[0008] Furthermore, the total content of the short-cut ceramic fibers and the long-cut ceramic fibers is 0.5 to 5 wt.% of the total mass of the material, and the ratio of their addition is 1:2 to 4.
[0009] Furthermore, the chopped ceramic fibers have a diameter of 0.5~5μm and a length of 1~100μm.
[0010] Furthermore, the diameter of the long-cut ceramic fiber is 5~9μm and the length is ≥300mm, specifically the length of the heating band of the workpiece.
[0011] Furthermore, based on the total mass of the material, the content of Mo is 93%~98%, the content of W is 0.05%~0.3%, the content of Ti is 0.05%~0.3%, the content of Zr is 0.03%~0.05%, the content of C is 0.01%~0.05%, and the content of lanthanum oxide is ≤2.1%.
[0012] Compared with the prior art, the present invention has the following advantages: This invention utilizes the Zener pinning effect of dispersed multi-component complex carbides ((Ti,Mo,W)C, (Zr,Mo,W)C and oxide particles (TiO2,ZrO2,La2O3) in a molybdenum matrix, combined with the heterogeneous nucleation and physical barrier effect of chopped ceramic fibers, to inhibit recrystallization and grain growth of the molybdenum matrix, thereby reducing the ductile-brittle transition temperature of the matrix. After holding at 1400℃ for 100h, the grain size of the workpiece is maintained at 14.2-15.3μm. This invention further enhances service safety and failure predictability by forming a multi-scale three-dimensional reinforcement network through internally three-dimensionally randomly distributed short chopped fibers and surface-oriented intercalated long fibers. The short fibers absorb the energy of microcrack propagation, while the long fibers consume the energy of the main crack through mechanisms such as crack bridging, fiber pull-out, and delamination. Attached Figure Description
[0013] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.
[0014] Figure 1 This is a schematic diagram of the material structure composition provided for an embodiment of this application; Figure 2 A flowchart provided for an embodiment of this application. Detailed Implementation
[0015] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0016] like Figure 1 As shown, the present invention provides a molybdenum matrix composite heating belt material for vacuum isothermal forging, the material comprising: Molybdenum matrix; The second phase particles are dispersed in the molybdenum matrix. The second phase particles include at least one of TiC, WC, ZrC, and lanthanum oxide, and at least one of (Ti,Mo,W)C and (Zr,Mo,W)C multi-component complex carbides generated by in-situ reaction. The particle size of the second phase particles is 10 nm to 500 nm. Short-cut ceramic fibers uniformly distributed within the molybdenum matrix; Long-cut ceramic fibers are oriented along the length of the molybdenum matrix, and a mechanical interlocking interface is formed between the long-cut ceramic fibers and the molybdenum matrix (a metal coating can be applied to the surface to improve the bonding strength).
[0017] In this structure, the second phase particles and the long-cut ceramic fibers form a heterogeneous structure in the molybdenum matrix, which synergistically inhibits the recrystallization and grain growth of the molybdenum matrix through the pinning effect of the second phase. At the same time, Ti and Zr elements preferentially combine with oxygen impurities to purify the matrix and reduce the ductile-brittle transition temperature of the matrix. The short-cut ceramic fibers and the long-cut ceramic fibers together form a three-dimensional reinforcing network to improve the high-temperature toughness and thermal shock resistance of the molybdenum matrix.
[0018] Tungsten (W) and molybdenum (Mo) have a strong affinity for carbon (C), titanium (Ti), zirconium (Zr), and other elements. At the high temperatures required for preparation and service, TiC, WC, ZrC, lanthanum oxide, and even further, multi-component solid solution carbides such as (Ti,Mo,W)C and (Zr,Mo,W)C are formed.
[0019] Ti, Zr, and La are reactive elements that react with trace amounts of oxygen in the alloy to form oxide particles such as TiO2, ZrO2, ZrTiO4, and La2O3. Thus, Ti and Zr can act as a second phase, pinning grain boundaries, by forming fine oxides; and they also purify the alloy matrix by "removing" oxygen, thereby reducing the room-temperature brittleness of the molybdenum alloy.
[0020] Furthermore, some Zr forms Laves phase intermetallic compounds with Mo, which can be distributed at grain boundaries and play a strengthening role in the material by hindering dislocation movement.
[0021] The second phase particles also include Mo2C, which is generated in situ through the reaction of a molybdenum matrix with carbon, and has a particle size of less than 100 nm.
[0022] Furthermore, in this invention, the second-phase particles (TiC, WC, ZrC, etc.) in the molybdenum-based material and the ceramic phase fibers (such as alumina and titanium carbonitride) can synergistically inhibit grain growth. First, during subsequent high-temperature service, the fibers themselves will also undergo a certain degree of recovery and recrystallization. At this time, the uniformly distributed nanoparticles in the matrix will continuously pin their grain boundaries, further inhibiting the structural coarsening of the fibers themselves and maintaining their reinforcing effect.
[0023] Meanwhile, the presence of nanoparticles keeps the alloy in a fine-grained state. The finer the grains, the better the plasticity and toughness of the material. Once cracks inevitably form in the matrix, when they extend to the fibers, the ceramic fibers act like the "steel bars" in reinforced concrete, bridging the cracks. Even if the cracks do not terminate, they will consume a lot of energy. If the cracks bypass them, the crack path deflects or bifurcates, increasing the length of the propagation path, which will also consume more energy, thus producing a toughening effect.
[0024] Therefore, when vibration and impact occur, ceramic fibers will share most of the load and reduce the stress on the matrix. At the same time, the fine and dispersed MoC / TiC / WC / ZrC / lanthanum oxide, (Ti,Mo,W)C and (Zr,Mo,W)C nanoparticles act as strong obstacles to dislocation movement, greatly increasing the resistance to dislocation movement.
[0025] It is evident that the synergistic effect of nanoparticles and ceramic fibers can not only inhibit the growth of molybdenum-based grains, but also help the material resist external forces and improve its service life.
[0026] Notably, ceramic fibers are divided into chopped ceramic fibers and long-cut ceramic fibers. Long-cut ceramic fibers provide a skeleton for metal materials, ensuring the integrity of the metal materials and enabling them to resist vibration and minor impacts, thus giving the entire material toughness.
[0027] Single-fiber reinforced materials exhibit severe anisotropy, with poor properties perpendicular to the fiber direction. This limits the enhancement of the material's strength, modulus, and tensile properties, and may even lead to performance degradation due to the fiber / matrix interface becoming a weak point. To address this issue, short fibers are combined with long fibers to enhance anisotropy and reduce the occurrence of this problem (the properties along the fiber length will always be higher than in other directions, but the impact is not significant).
[0028] Furthermore, the addition of short fibers has the following advantages: (1) as heterogeneous nucleation sites, refining the initial grains; (2) as a physical barrier, hindering grain boundary migration.
[0029] In this structure, the short-cut ceramic fibers and the long-cut ceramic fibers form a heterogeneous structure, together creating a three-dimensional reinforcement network. The short fibers act as a bridge between the second-phase particles and the long fibers, helping the second-phase particles to suppress grain growth and assisting the long fibers in absorbing crack propagation energy.
[0030] Furthermore, the uniformly distributed short fibers and dispersed second-phase particles within the matrix ensure the basic strength and toughness of the matrix in all directions, while the directional arrangement of long fibers provides additional reinforcement only in the required directions.
[0031] The long-cut ceramic fiber or the short-cut ceramic fiber is any one or more of alumina and titanium carbonitride.
[0032] The content of the short-cut ceramic fibers and the total content of the long-cut ceramic fibers are ≤5 wt.%.
[0033] The content of ceramic fibers is very small, at most no more than 5%. The diameter of the mechanically bonded ceramic fibers is very small, on the order of micrometers. The majority of the material is still metal, so it will not cause defects or cracks due to differences in thermal stress.
[0034] The diameter of the chopped ceramic fibers is ≤Φ5*100μm.
[0035] The long-cut ceramic fibers have a diameter ≤9μm and a length ≥300mm, which is the length of the heating belt.
[0036] Based on the total mass of the material, the content of Mo is 93%~98%, the content of W is 0.05%~0.3%, the content of Ti is 0.05%~0.3%, the content of Zr is 0.03%~0.05%, the content of C is 0.01%~0.05%, and the content of lanthanum oxide is ≤2.1%.
[0037] This invention controls the lanthanum oxide content to below 2.1%, avoiding the problems of agglomeration and pinning effect degradation caused by excessively high lanthanum oxide content during long-term high-temperature service.
[0038] like Figure 2 As shown, the present invention also provides a method for preparing a molybdenum matrix composite heating belt material for vacuum isothermal forging, comprising the following steps: S100. Molybdenum powder, titanium source, tungsten source, carbon source, zirconium source, lanthanum oxide and short-cut ceramic fibers are mixed to obtain composite powder; S200. A molybdenum alloy rod containing second-phase particles and the chopped ceramic fibers is obtained through powder metallurgy. During the sintering process, tungsten, titanium, zirconium react with carbon to generate multi-component complex carbide particles, while titanium and zirconium react with residual oxygen to generate oxide particles. S300. The bar is forged and extruded to form a billet with a grain size ≤50μm, and then rolled into a plate with a width of 300-600mm. A circular arc groove is cut on the surface of the plate. S400. Long-cut ceramic fibers are laid in the arc groove, and then the long-cut ceramic fibers are embedded into the plate through mechanical interlocking by small deformation pressing or rolling. The long-cut ceramic fibers are oriented along the rolling direction. The short-cut fibers randomly distributed in three dimensions inside the material and the oriented interlocking long fibers on the surface together form a multi-scale three-dimensional reinforcement network to obtain a molybdenum alloy composite material. S500: Anneal the molybdenum alloy composite material to stabilize its microstructure.
[0039] Rolling is a type of mechanical bonding. It involves creating holes in the surface of two very thin metal blocks and rolling them together to form a bond, similar to creating a hole filled with fibers. The bond primarily relies on the diffusion of the metals.
[0040] The sheet material has been well processed before rolling, and its grain size and thickness have been specified. During the rolling process, there will be temperature and pressure.
[0041] The following examples further illustrate this point: Example 1
[0042] 1. Selection of raw materials Molybdenum powder (purity ≥99.9%, average particle size 3μm): balance; Tungsten powder (purity ≥99.5%, average particle size 2μm): addition amount 2.0wt%; Hydrogenated titanium / titanium powder (purity ≥99.5%, average particle size 500nm): addition amount 0.3wt%; (using hydrogenated titanium powder can further purify the alloy, and the oxygen content will be lower) Zirconium hydride / zirconium powder (purity ≥99.5%, average particle size 500nm): addition amount 0.2wt%; Graphite powder (purity ≥99.9%, average particle size 500nm): addition amount 0.1wt% Lanthanum oxide (purity ≥99.5%, average particle size 500nm): addition amount 2.0wt% Short-cut alumina fibers (0.5~2mm in length, 10μm in diameter): 1.0wt% addition; Long alumina continuous fiber bundle (monofilament diameter 12μm, bundle diameter approximately 0.5mm, length 300mm): addition amount 3.0wt%.
[0043] 2. Preparation steps (1) Preparation of composite powder Under an argon protective atmosphere, molybdenum powder, tungsten powder, titanium powder, zirconium powder, graphite powder, and chopped alumina fibers were added together into a star-shaped mixer and mixed for 24 hours to obtain a composite powder. After mixing, the chopped fibers were evenly distributed among the powder particles, with no visible agglomeration.
[0044] (2) Cold pressing and sintering Cold pressing: The composite powder is loaded into a steel mold and cold pressed under a pressure of 200MPa to obtain a round bar with a diameter of 85mm and a length of 150mm.
[0045] Sintering: The billet is placed in a medium-frequency induction sintering furnace under hydrogen atmosphere protection, heated to 1650°C at 10°C / min, held for 2 hours, and cooled with the furnace to obtain a molybdenum alloy rod (diameter 85 mm, length 150 mm) containing short-cut ceramic fibers.
[0046] In-situ formation of the second phase: During sintering, tungsten, titanium, and zirconium react with carbon to form multi-component complex carbide particles (mainly (Ti,Mo,W)C and (Zr,Mo,W)C); simultaneously, titanium and zirconium react with residual oxygen to form TiO2, ZrO2, and a small amount of ZrTiO4 oxide particles. The size of these second-phase particles is 20~100nm, and they are dispersed within the molybdenum grains and grain boundaries.
[0047] (3) Forging Forging and extrusion: The sintered bars were forged under argon protection at 1200°C with a blank forging deformation of 60%, followed by hot extrusion at 1150°C at an extrusion ratio of 4:1 to obtain a square billet with a cross-section of 100mm × 20mm. The billet grain size was found to be ≤50μm.
[0048] Rolling into wide, thin plates: The billet is hot-rolled in multiple passes (≥3) at 1150°C, with a reduction of 10%~15% per pass, ultimately producing a plate with a thickness of 0.6mm and a width of 300mm. (Length is not limited.) Cutting arc grooves: Multiple arc grooves are cut along the length direction (subsequent rolling direction) on the upper surface of the sheet using a CNC machine tool. The groove depth is approximately 0.1 mm, the groove width is approximately 0.1 mm, and the groove spacing is 10 mm. The arc grooves are used to accommodate long-cut ceramic fibers and enhance the mechanical interlocking effect.
[0049] (4) Pressing / rolling embedding Fiber laying: Long continuous alumina fiber bundles are laid parallel in the arc grooves on the surface of the plate, with each fiber bundle aligned with one arc groove. The fiber bundles are arranged along the length of the plate (i.e., the rolling direction). Another plate is then placed on top of the fiber-laying plate.
[0050] Small deformation pressing and embedding: The fiber-laying board is placed in an argon-protected heating furnace, heated to 1100°C, and held for 20 minutes; immediately after removal, it is subjected to single-pass small deformation rolling on a two-roll hot rolling mill with a roll diameter of 300mm, a rolling speed of 0.3m / s, and a reduction of only 5% (small deformation conditions).
[0051] After rolling, the sheet is placed in a high-temperature furnace for annealing, with the annealing temperature being less than or equal to the rolling temperature.
[0052] Long-cut ceramic fibers are pressed into arc grooves and further embedded inside the plate, forming a tight mechanical interlocking interface with the molybdenum matrix, and are highly oriented along the rolling direction.
[0053] Cooling: Air-cool to room temperature to obtain molybdenum alloy composite heating belt plate. After edge trimming and shaping, it can be installed and used after passing inspection.
[0054] Example 2
[0055] 1. The raw materials are the same as in Example 1; 2. The preparation method is the same as in Example 1, except that the amount of long alumina continuous fiber bundle added is 2.0 wt%.
[0056] Example 3
[0057] 1. The raw materials are the same as in Example 1; 2. The preparation method is the same as in Example 1, except that the amount of long alumina continuous fiber bundle added is 4.0 wt%.
[0058] Comparative Example 1: A molybdenum alloy material with short fibers but without long fiber intercalation was prepared, with the amount of short fibers added being 4.0 wt%.
[0059] Comparative Example 2: Prepare a molybdenum alloy material without short fibers but with long fiber intercalation, with the long fiber addition amount being 4.0 wt%.
[0060] 3. Material structure and properties (1) Material composition analysis The national standard refers to GB / TB222-2025 for testing, and the other elements are tested according to the standards of third-party testing institutions.
[0061] The component (mass fraction wt.%) contents of different embodiments are shown in Table 1: Table 1
[0062] Table 1 shows the measured mass fractions of key elements in the molybdenum-based composite materials prepared in Examples 1-3. All examples used molybdenum (Mo) as the matrix, with the balance being mainly molybdenum.
[0063] Analysis shows that in Examples 1-3, the contents of non-aluminum elements such as Ti, Zr, La, W, and C are highly consistent, namely Ti 0.28 wt.%, Zr 0.17 wt.%, La 1.92 wt.%, W 1.95 wt.%, and C 0.09 wt.%. This indicates that the powder mixing and powder metallurgy process used has good stability and repeatability, and can precisely control the introduction of multi-element alloying elements.
[0064] The Al content is approximately equal to the sum of short and long fibers. According to the Al analysis in Examples 1-3, the higher the amount of long fibers added, the higher the Al content.
[0065] Furthermore, the C content was controlled at 0.09 wt.%, slightly lower than the theoretical addition amount (0.1 wt.%), indicating that the carbon source (graphite powder) fully participated in the reaction during the sintering process, generating the expected carbide second phase, and there was no excess free carbon residue, ensuring the purity of the matrix.
[0066] The total content of active elements such as Ti, Zr, and La is approximately 2.37 wt.%. They preferentially combine with residual oxygen in the system to form stable oxide particles (such as TiO2, ZrO2, and La2O3), playing a dual role in purifying the matrix and generating the second phase of oxides in situ.
[0067] Composition analysis confirmed that the method of this invention successfully prepared a multi-component molybdenum-based composite material that meets the design requirements. The content of each element was precisely controlled, providing a material basis for the subsequent excellent mechanical properties and anti-recrystallization properties.
[0068] (2) Detection of second-phase particles GB / T18876.1-2002 / GB_T18876.1-2024 Standard test methods for determination of metallographic structure, inclusion content and grade in steel and other metals by automatic image analysis - Part 1: Image analysis and stereographic determination of inclusion or second phase structure content in steel and other metals.
[0069] This demonstrates that the second-phase particles in Examples 1-3 were successfully introduced.
[0070] (3) Detection of recrystallization behavior The recrystallization behavior was tested according to GB / T6394-2017 "Method for Determination of Average Grain Size of Metals".
[0071] (4) Plane strain fracture toughness Characterizing a material's ability to resist crack propagation is an important indicator for measuring its fracture resistance. The standard is GB / T4161-2007 Metallic Materials, and the KIC test method for plane strain fracture toughness is adopted.
[0072] (5) Long-term thermal cycling verification Accelerated life tests were conducted on Examples 1-3 and Comparative Examples 1-2 under simulated long-term repeated heating conditions in a forging chamber to verify the long-term stability of the fiber network and the grain retention.
[0073] The results are shown in Table 2: Table 2
[0074] Note: For tensile tests, samples are taken along the length direction, consistent with the fiber arrangement direction. For plane strain fracture toughness tests, samples are taken perpendicular to the fiber arrangement direction. Table 2 compares the differences between Examples 1-3 and Comparative Examples 1-2 in terms of mechanical properties, grain size, and high-temperature recrystallization resistance. The analysis is as follows: (1) Example 2 yielded the highest tensile strength (751 MPa) and elongation (15.7%). This indicates that when the amount of long fiber added is 2.0 wt% and the amount of short fiber added is 1.0 wt%, the three-dimensional reinforcing network formed by the short fiber, long fiber and second phase particles is optimized, achieving a good match between strength and toughness.
[0075] Compared to Comparative Example 1, Comparative Example 2 (long fiber only) showed acceptable plane strain fracture toughness (26.9), but its strength (710 MPa) and elongation (14.2%) were both reduced. This demonstrates that long fibers can significantly improve the toughness of materials, but the effect of a single fiber in enhancing toughness is limited. The synergistic effect of long and short fibers (Example 3) can more effectively transfer loads and suppress crack propagation, thereby improving the strength of materials.
[0076] Example 3 (4.0 wt% long fibers) showed a significant decrease in elongation (14.1%), which may be due to the increased matrix interface caused by the excessive long fiber content, or the local stress concentration during small deformation rolling embedding, which is not conducive to elongation. However, its strength was significantly improved compared to Comparative Example 2.
[0077] (2) The grain size (12.4-13.5 μm) of all embodiments was significantly smaller than that of Comparative Example 1 (16.3 μm) and Comparative Example 2 (14.3 μm). This demonstrates that the chopped ceramic fibers uniformly distributed within the matrix and the in-situ generated second-phase particles act as heterogeneous nucleation sites and physical barriers, effectively refining the grains during thermal processing.
[0078] The grains in both Comparative Examples 1 and 2 showed significant coarsening, indicating that single long or short fibers lack sufficient and continuous second-phase pinning force under long-term high-temperature conditions.
[0079] As can be seen, in this invention, the dispersed nanoscale multi-component complex carbide and oxide particles (Zener pinning effect) and the three-dimensional ceramic fiber network (physical barrier effect) work together to greatly suppress the formation of recrystallization nuclei and the migration of grain boundaries, thereby achieving extraordinary high-temperature structural stability.
[0080] In summary, the overall performance of Examples 1-3 is significantly better than that of the comparative examples, especially Example 2, which maintains the highest strength and plasticity while also having excellent resistance to high-temperature grain growth.
[0081] When molybdenum recrystallizes, its fine and hard second-phase particles act like "nails" on the grain boundaries, hindering the migration and growth of the grain boundaries. This delays the recrystallization process to occur at higher temperatures. However, there is a limit to the amount of second-phase particles that can be added; adding too many will severely damage the plasticity of the material.
[0082] The presence of long and short fibers follows specific patterns, and their proportions and structural relationships have particular significance. Specifically, with a fixed number of long fibers, the number of short fibers and precipitates leads to smaller grain size and an increased recrystallization temperature. With a fixed number of short fibers, increasing the number of long fibers can also lead to smaller grains and an increased recrystallization temperature to some extent, but its effect is smaller than the former. Simultaneously, long fibers exhibit greater brittleness, and their increased content results in decreased plasticity. The second phase and short fibers provide more nucleation sites for grains than long fibers.
[0083] This invention successfully solves the problem of grain coarsening in molybdenum-based materials during long-term high-temperature service by using a multi-level composite structure of "nano-second phase particles + short-cut fibers (internal distribution) + long-cut fibers (directional intercalation)".
[0084] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. All such modifications or substitutions should be covered within the protection scope of this application, and should not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application. Therefore, the protection scope of this application should be determined by the protection scope of the claims.
Claims
1. A method for preparing a molybdenum-based composite heating belt material for vacuum isothermal forging, characterized in that, Includes the following steps: S100. Molybdenum powder, titanium source, tungsten source, carbon source, zirconium source, lanthanum oxide and short-cut ceramic fibers are mixed to obtain composite powder; S200. A molybdenum alloy rod containing second-phase particles and the chopped ceramic fibers is obtained through powder metallurgy. During the sintering process, tungsten, titanium, zirconium react with carbon to generate multi-component complex carbide particles, while titanium and zirconium react with residual oxygen to generate oxide particles. S300. The bar is forged and extruded to form a billet with a grain size ≤50μm, and then rolled into a plate with a width of 300-600mm. A circular arc groove is cut on the surface of the plate. S400. Long-cut ceramic fibers are laid in the arc groove, and then the long-cut ceramic fibers are embedded into the plate through mechanical interlocking by small deformation pressing or rolling. The long-cut ceramic fibers are oriented along the rolling direction. The short-cut fibers randomly distributed in three dimensions inside the material and the oriented interlocking long fibers on the surface together form a multi-scale three-dimensional reinforcement network to obtain a molybdenum alloy composite material. S500: Anneal the molybdenum alloy composite material to stabilize its microstructure.
2. The method for preparing the molybdenum matrix composite heating belt material for vacuum isothermal forging according to claim 1, characterized in that, The long-cut ceramic fiber or the short-cut ceramic fiber is any one or more of alumina and titanium carbonitride.
3. A molybdenum-based composite heating belt material for vacuum isothermal forging, characterized in that, The material is obtained by the preparation method according to claim 1 or 2, wherein the material comprises: Molybdenum matrix; The second phase particles are dispersed in the molybdenum matrix, and the second phase particles include at least one of TiC, WC, ZrC, and lanthanum oxide, and at least one of (Ti,Mo,W)C and (Zr,Mo,W)C multi-component complex carbides generated by in-situ reaction; The particle size of the second phase particles is 10 nm to 500 nm; Short-cut ceramic fibers uniformly distributed within the molybdenum matrix; Long-cut ceramic fibers are oriented along the length direction in the molybdenum matrix, and a mechanical interlocking interface is formed between the long-cut ceramic fibers and the molybdenum matrix; In this structure, the second phase particles and the long-cut ceramic fibers form a heterogeneous structure in the molybdenum matrix, which synergistically inhibits the recrystallization and grain growth of the molybdenum matrix through the pinning effect of the second phase. At the same time, Ti and Zr elements preferentially combine with oxygen impurities to purify the matrix and reduce the ductile-brittle transition temperature of the matrix. The short-cut ceramic fibers and the long-cut ceramic fibers together form a three-dimensional reinforcing network to improve the high-temperature toughness and thermal shock resistance of the molybdenum matrix.
4. The molybdenum matrix composite heating belt material for vacuum isothermal forging according to claim 3, characterized in that, The total content of the short-cut ceramic fibers and the long-cut ceramic fibers is 0.5 to 5 wt.% of the total mass of the material, and the ratio of their addition is 1:2 to 4.
5. The molybdenum matrix composite heating belt material for vacuum isothermal forging according to claim 4, characterized in that, The chopped ceramic fibers have a diameter of 0.5~5μm and a length of 1~100μm.
6. The molybdenum matrix composite heating belt material for vacuum isothermal forging according to claim 4, characterized in that, The diameter of the long-cut ceramic fiber is 5~9μm and the length is ≥300mm.
7. The molybdenum matrix composite heating belt material for vacuum isothermal forging according to claim 3, characterized in that, Based on the total mass of the material, the content of Mo is 93%~98%, the content of W is 0.05%~0.3%, the content of Ti is 0.05%~0.3%, the content of Zr is 0.03%~0.05%, the content of C is 0.01%~0.05%, and the content of lanthanum oxide is ≤2.1%.