A zirconium-niobium alloy prepared by dehydrogenation activation sintering of zirconium hydride and its preparation method
By employing a two-stage sintering process involving zirconium hydride powder and niobium powder, the problems of compositional segregation and oxide film in the preparation of zirconium-niobium alloys were solved, enabling the preparation of zirconium-niobium alloys with high density and excellent performance, reducing production costs and simplifying the process.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- NORTHWEST INSTITUTE FOR NONFERROUS METAL RESEARCH
- Filing Date
- 2026-03-19
- Publication Date
- 2026-05-26
AI Technical Summary
Existing technologies for preparing zirconium-niobium alloys suffer from problems such as compositional segregation, uneven microstructure, low material utilization, and high cost. In particular, traditional smelting methods result in high energy consumption and difficulties in processing complex shaped components, while powder metallurgy methods face challenges such as oxide films hindering sintering and high-temperature densification.
By mixing zirconium hydride powder and niobium powder, and through a two-stage process of dehydrogenation pre-sintering and high-temperature sintering, the highly active Zr atoms generated by the decomposition of ZrH2 are used to break the diffusion barrier of the oxide film, thereby achieving high densification at normal pressure and low temperature, and preparing a zirconium-niobium alloy with high density and uniform composition.
By lowering the sintering temperature under normal pressure, the material properties were improved, the raw material cost was reduced, the process was simplified, making it suitable for industrial production, and high density and excellent mechanical properties were obtained.
Abstract
Description
Technical Field
[0001] This invention belongs to the field of non-ferrous metal metallurgy technology, specifically relating to a zirconium-niobium alloy prepared by dehydrogenation activation sintering of zirconium hydride and its preparation method. Background Technology
[0002] Zirconium-niobium alloys, especially those with a nominal composition of Zr-2.5wt.%Nb, are widely used in high-end fields such as nuclear reactor pressure tubes, fuel cladding, and biomedical implants due to their excellent properties, including high strength, good corrosion resistance, and low thermal neutron absorption cross section.
[0003] Currently, the preparation of Zr-2.5Nb alloys mainly relies on traditional vacuum arc melting or electron beam melting technologies. However, the melting method has obvious limitations: First, the melting points of zirconium and niobium differ significantly (Zr is about 1855℃, and Nb is about 2468℃), which easily leads to severe compositional segregation and uneven microstructure during the melting process; second, the melting process is energy-intensive, and for components with complex shapes, subsequent cumbersome forging and machining processes are often required, resulting in low material utilization and high costs.
[0004] To overcome the shortcomings of the melting method, powder metallurgy technology has received widespread attention as a near-net-shape forming process. In the existing technology, the direct approach is to use pure Zr powder and Nb powder as raw materials for mixed sintering. However, this method faces the following challenges: (1) High-activity pure Zr powder is extremely expensive and is easily oxidized during production, storage and transportation, forming a dense and chemically stable zirconium oxide (ZrO2) film on its surface. This oxide film will seriously hinder the diffusion between zirconium and niobium atoms during sintering, becoming the main obstacle to sintering densification. (2) In order to obtain a relatively dense sintered body, it is often necessary to use external pressure sintering methods such as hot pressing (HP) or hot isostatic pressing (HIP), or to raise the sintering temperature to above 1400°C or even close to the melting point of Zr. The former means huge equipment investment and complex process; the latter will lead to abnormally coarse grains, deteriorate the mechanical properties of the alloy, and impose harsh requirements on the high-temperature resistance of the sintering furnace. Therefore, developing a new method for preparing zirconium-niobium alloy powder metallurgy that can achieve high densification at normal pressure and relatively low temperature is of great significance for reducing production costs, improving material properties, and promoting its wider application. Summary of the Invention
[0005] The technical problem to be solved by this invention is to provide a method for preparing zirconium-niobium alloys based on zirconium hydride dehydrogenation activation sintering, addressing the shortcomings of the prior art. This method uses zirconium hydride powder as raw material, utilizing the chemical activation effect of the ZrH2 decomposition process to break the diffusion barrier of the oxide film on the surface of conventional Zr powder and lower the sintering temperature. This enables the efficient, safe, and low-cost preparation of high-density, uniformly composed, and high-performance zirconium-niobium alloys under normal pressure and relatively low temperature conditions. This solves the problems of high raw material cost, easy oxidation, and difficulty in sintering densification that exist in the prior art when preparing zirconium-niobium alloys using pure Zr powder.
[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: a method for preparing zirconium-niobium alloys based on zirconium hydride dehydrogenation activation sintering, characterized in that the method includes the following steps: Step 1: According to the composition ratio of the target product zirconium-niobium alloy, mix zirconium hydride powder and niobium powder to obtain mixed powder; Step 2: Press the mixed powder from Step 1 into a shape to obtain a green body; Step 3: Sinter the green billet from Step 2, including: (1) Dehydrogenation pre-sintering stage: Under vacuum or inert atmosphere protection, heat the green billet to 300℃~800℃ and hold it to decompose ZrH2; (2) High temperature sintering stage: Then raise the temperature to 1250℃~1400℃ and hold it to alloy and densify Zr and Nb to obtain zirconium-niobium alloy.
[0007] This invention involves mixing zirconium hydride powder and niobium powder, pressing them into a green body with a specific shape and strength, and then performing a two-stage sintering process. In the dehydrogenation pre-sintering stage, heating and holding allow ZrH2 to fully decompose into highly chemically active Zr atoms and release hydrogen gas, while avoiding cracking of the green body due to rapid hydrogen release. The dehydrogenation activation effect during the ZrH2 decomposition process effectively destroys the oxide film on the surface of Zr particles, significantly promoting the sintering driving force. Then, in the high-temperature sintering stage, the temperature is further increased and held, and the high activity of the newly formed Zr atoms greatly promotes the interdiffusion between Zr and Nb atoms, achieving densification. Thus, a zirconium-niobium alloy with uniform structure and high density is successfully prepared under normal pressure and relatively low temperature.
[0008] The above-mentioned method for preparing zirconium-niobium alloys based on zirconium hydride dehydrogenation activation sintering is characterized in that the average particle size of the zirconium hydride powder and niobium powder in step one does not exceed 50 μm. This invention controls the average particle size of the zirconium hydride powder and niobium powder. On the one hand, by using fine-particle-size powders with a larger specific surface area, the contact area between the zirconium hydride powder and niobium powder is increased, promoting atomic interdiffusion during subsequent alloying. On the other hand, the fine-particle-size zirconium hydride powder decomposes more fully and uniformly during slow heating, avoiding the problem of incomplete dehydrogenation within coarse-particle-size powders. Simultaneously, the fine-particle-size niobium powder can quickly combine with the highly active Zr atoms after ZrH2 decomposition, inhibiting early Zr grain growth, ultimately obtaining a fine and uniform alloy microstructure. This avoids the problems of insufficient powder contact and incomplete dehydrogenation caused by excessively large powder particle size, which leads to decreased density and compositional segregation in the zirconium-niobium alloy.
[0009] The method for preparing zirconium-niobium alloys based on zirconium hydride dehydrogenation activation sintering, as described above, is characterized in that the mixing in step one is mechanical mixing, carried out under the protection of an inert gas with a vacuum degree of less than -0.1 kPa or a purity of 99.9% or higher, and the mixing time is not less than 2 hours. Typically, the mixing time is 2 hours to 8 hours.
[0010] The above-mentioned method for preparing zirconium-niobium alloy based on zirconium hydride dehydrogenation activation sintering is characterized in that the pressing pressure in step two is 200MPa~400MPa, and the holding time is 1min~5min.
[0011] The method for preparing zirconium-niobium alloys based on zirconium hydride dehydrogenation activation sintering described above is characterized in that the vacuum degree in step three is less than 1×10⁻⁶. -2 Pa; the inert atmosphere is argon gas with a purity of 99.9%.
[0012] The method for preparing zirconium-niobium alloy based on zirconium hydride dehydrogenation activation sintering described above is characterized in that the heating rate of the dehydrogenation pre-sintering stage in step three is 1℃ / min~3℃ / min, and the holding time is 0~2h. A holding time of 0h indicates that the green blank is heated to 300℃~800℃ during the dehydrogenation pre-sintering stage without holding, and directly enters the high-temperature sintering stage. By controlling the slow heating rate of 1℃ / min~3℃ during the dehydrogenation pre-sintering stage, it is possible to avoid the rapid decomposition of ZrH2 and release of hydrogen, which could lead to cracking of the green blank. On the other hand, it ensures that ZrH2 fully destroys the oxide film on the surface of Zr particles during the decomposition process, releasing highly active Zr atoms. This avoids problems such as cracking of the green blank, incomplete dehydrogenation, and insufficient destruction of the oxide film that can easily occur with excessively rapid heating. At the same time, ZrH2 can gradually complete its decomposition within the temperature range of 300℃~800℃ during the slow heating process. Therefore, even if no holding time is taken after heating to the target temperature (0h), it can be ensured that ZrH2 is fully decomposed into highly active Zr atoms and hydrogen is completely removed. The holding time of 0.5h~2h can further improve the thoroughness of dehydrogenation, which is suitable for molded parts with larger blank thickness and allows for flexible adaptation to different blank specifications.
[0013] The above-mentioned method for preparing zirconium-niobium alloys based on zirconium hydride dehydrogenation activation sintering is characterized in that the heating rate in the high-temperature sintering stage in step three is within 5℃ / min, and the holding time is 1h~4h. More preferably, the holding time is 2h. By using a heating rate within 5℃ / min in the high-temperature sintering stage, slow and uniform alloying of Zr and Nb is achieved. The highly active Zr atoms generated in the dehydrogenation pre-sintering stage gradually interdiffusion with Nb atoms during the heating process, avoiding abnormal local grain growth caused by rapid heating, while ensuring the uniformity of alloy composition. Furthermore, this heating rate is connected to the slow heating process in the preceding dehydrogenation pre-sintering stage, avoiding damage to the billet structure caused by a sudden temperature rise.
[0014] Meanwhile, the present invention also discloses a zirconium-niobium alloy, characterized in that it is prepared by the above-described method.
[0015] The zirconium-niobium alloy described above is characterized in that the density of the zirconium-niobium alloy is not less than 95%.
[0016] The aforementioned zirconium-niobium alloy is characterized by having a uniform Zr(Nb) solid solution microstructure. In this invention, Nb atoms are uniformly dissolved in the Zr lattice to form a substitutional solid solution, resulting in a significant solid solution strengthening effect. This greatly improves the alloy's tensile strength, yield strength, and other mechanical properties. Furthermore, the uniform solid solution structure eliminates significant component segregation and second-phase precipitation, ensuring consistent corrosion resistance and preventing localized corrosion failure. Simultaneously, it guarantees the biocompatibility and mechanical durability of biomedical implants, making it suitable for nuclear industry applications such as nuclear reactor pressure tubes and fuel cladding.
[0017] Compared with the prior art, the present invention has the following advantages: 1. Activated sintering, reducing energy consumption: This invention uses zirconium hydride powder as raw material and combines a two-stage sintering process including dehydrogenation pre-sintering and high-temperature sintering. It utilizes the highly active "newborn" Zr atoms generated by the decomposition of ZrH2 to break the diffusion barrier of the dense oxide film on the surface of traditional pure Zr powder, resulting in an "activated sintering" effect. This reduces the high-temperature sintering temperature for densification of the alloy, which is much lower than the temperature required for using pure Zr powder (usually >1400℃), resulting in significant energy savings.
[0018] 2. Excellent product performance: By reducing the high-temperature sintering temperature, this invention effectively suppresses grain coarsening, which is conducive to obtaining a fine and uniform alloy microstructure. At the same time, the high sintering driving force promotes the interdiffusion between Zr and Nb atoms, ensuring that the niobium-zirconium alloy has high density (not less than 95%) and excellent mechanical properties.
[0019] 3. Significantly reduced raw material costs: This invention uses inexpensive ZrH2 powder to replace expensive high-activity pure zirconium powder, achieving the preparation of high-density niobium-zirconium alloy and significantly reducing raw material costs.
[0020] 4. Simple process, suitable for industrialization: The entire process of this invention can be completed under normal pressure, without relying on complex and expensive hot pressing or hot isostatic pressing equipment. The process is simple, highly reliable, and very suitable for large-scale industrial production.
[0021] The technical solution of the present invention will be further described in detail below through embodiments. Detailed Implementation
[0022] Example 1 This embodiment includes the following steps: Step 1: Raw material preparation: Based on the composition ratio of the target product, zirconium-niobium alloy Zr-2.5wt%Nb, select the average particle size (D). 50ZrH2 powder with an average particle size of 5 μm and Nb powder with an average particle size of 3 μm were weighed and placed in a double cone mixer and mixed for 5 hours under the protection of argon atmosphere to obtain mixed powder. Step 2, pressing and molding: The mixed powder from Step 1 is loaded into the mold and held under a uniaxial pressure of 300MPa for 2 minutes to obtain a circular green sheet with a diameter of 20mm and a thickness of 5mm. Step 3, Dehydrogenation Sintering: The circular green blanks from Step 2 are placed in a vacuum sintering furnace for sintering treatment: (1) Dehydrogenation Pre-sintering Stage: Vacuum is drawn until the vacuum degree is less than 5×10 -3 After Pa, heating begins. First, the temperature is increased from room temperature to 300℃ at a heating rate of 10℃ / min, and then increased to 800℃ at a heating rate of 2℃ / min and held for 1h to ensure that ZrH2 is fully decomposed; (2) High temperature sintering stage: The temperature is increased to 1350℃ at a heating rate of 5℃ / min and held for 2h to alloy and densify Zr and Nb. After cooling to room temperature with the furnace, the Zr-Nb alloy is obtained.
[0023] Example 2 This embodiment includes the following steps: Step 1: Raw material preparation: According to the composition ratio of the target product zirconium-niobium alloy Zr-2.5wt%Nb, select ZrH2 powder with a particle size range of 15μm~50μm and Nb powder with a particle size range of 1μm~10μm, weigh them and place them in a double cone mixer, mix them for 3 hours under the protection of argon atmosphere to obtain mixed powder. Step 2, pressing and molding: The mixed powder from Step 1 is loaded into the mold and held under a uniaxial pressure of 300MPa for 3 minutes to obtain a cylindrical green body with a diameter of 25mm and a height of 25mm. Step 3, Dehydrogenation Sintering: The cylindrical green billet from Step 2 is sintered: (1) Dehydrogenation Pre-sintering Stage: It is placed in a sintering furnace with flowing high-purity argon gas of 99.9% purity. It is heated from room temperature to 300℃ at a heating rate of 5℃ / min, and then heated to 800℃ at a heating rate of 2℃ / min and held for 1h to ensure that ZrH2 is fully decomposed; (2) High-Temperature Sintering Stage: It is heated to 1400℃ at a heating rate of 3℃ / min and held for 2h to alloy and densify Zr and Nb. After cooling to room temperature with the furnace, it is taken out to obtain zirconium-niobium alloy.
[0024] Example 3 The difference between this embodiment and embodiment 1 is that the pressing pressure in step 2 is 200 MPa and the holding time is 1 min.
[0025] Example 4 The difference between this embodiment and embodiment 1 is that the pressing pressure in step 2 is 400 MPa and the holding time is 5 min.
[0026] Example 5 The difference between this embodiment and Embodiment 1 is that in the dehydrogenation pre-sintering stage of step three, the temperature is increased to 800°C at a heating rate of 1°C / min and held for 2 hours to ensure that ZrH2 is fully decomposed.
[0027] Example 6 The difference between this embodiment and Embodiment 1 is that in the dehydrogenation pre-sintering stage of step three, the temperature is increased to 800°C at a heating rate of 3°C / min and held for 0 hours, i.e., no holding is required.
[0028] Testing revealed that the zirconium-niobium alloy prepared in this embodiment has a density of 96.2%, a uniform Zr(Nb) solid solution microstructure, and no hydrogen residue or component segregation.
[0029] Example 7 The difference between this embodiment and embodiment 1 is that in step two, cold isostatic pressing is used for molding, and the pressure is 350MPa.
[0030] Example 8 The difference between this embodiment and Embodiment 1 is that the heat preservation time in the high-temperature sintering stage in step three is 4 hours.
[0031] Testing revealed that the zirconium-niobium alloy prepared in this embodiment had a density of 98.1%, a uniform Zr(Nb) solid solution microstructure, and grain refinement to 15 μm.
[0032] Example 9 The difference between this embodiment and Embodiment 1 is that the heat preservation time in the high-temperature sintering stage in step three is 1 hour.
[0033] Testing revealed that the zirconium-niobium alloy prepared in this embodiment has a density of 95.3% and a uniform Zr(Nb) solid solution microstructure.
[0034] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Any simple modifications, alterations, and equivalent changes made to the above embodiments based on the inventive essence shall still fall within the protection scope of the present invention.
Claims
1. A method for preparing zirconium-niobium alloys based on zirconium hydride dehydrogenation activation sintering, characterized in that, The method includes the following steps: Step 1: According to the composition ratio of the target product zirconium-niobium alloy, mix zirconium hydride powder and niobium powder to obtain mixed powder; Step 2: Press the mixed powder from Step 1 into a shape to obtain a green body; Step 3: Sinter the green billet from Step 2, including: (1) Dehydrogenation pre-sintering stage: Under vacuum or inert atmosphere protection, heat the green billet to 300℃~800℃ and hold it to decompose ZrH2; (2) High temperature sintering stage: Then raise the temperature to 1250℃~1400℃ and hold it to alloy and densify Zr and Nb to obtain zirconium-niobium alloy.
2. The method for preparing zirconium-niobium alloy based on zirconium hydride dehydrogenation activation sintering according to claim 1, characterized in that, The average particle size of the zirconium hydride powder and niobium powder mentioned in step one does not exceed 50 μm.
3. The method for preparing zirconium-niobium alloy based on zirconium hydride dehydrogenation activation sintering according to claim 1, characterized in that, The mixing described in step one is mechanical mixing, which is carried out under the protection of an inert gas with a vacuum degree of less than -0.1 kPa or a purity of more than 99.9%, and the mixing time is not less than 2 hours.
4. The method for preparing zirconium-niobium alloy based on zirconium hydride dehydrogenation activation sintering according to claim 1, characterized in that, The pressing pressure in step two is 200MPa~400MPa, and the holding time is 1min~5min.
5. The method for preparing zirconium-niobium alloy based on zirconium hydride dehydrogenation activation sintering according to claim 1, characterized in that, The vacuum level mentioned in step three is less than 1×10⁻⁶. -2 Pa; the inert atmosphere is argon gas with a purity of 99.9%.
6. The method for preparing zirconium-niobium alloy based on zirconium hydride dehydrogenation activation sintering according to claim 1, characterized in that, The heating rate in the dehydrogenation pre-sintering stage described in step three is 1℃ / min to 3℃ / min, and the holding time is 0 to 2h.
7. The method for preparing zirconium-niobium alloy based on zirconium hydride dehydrogenation activation sintering according to claim 1, characterized in that, The heating rate in the high-temperature sintering stage described in step three is less than 5℃ / min, and the holding time is 1h to 4h.
8. A zirconium-niobium alloy, characterized in that, Prepared by the method described in any one of claims 1 to 7.
9. A zirconium-niobium alloy according to claim 8, characterized in that, The density of the zirconium-niobium alloy is not less than 95%.
10. A zirconium-niobium alloy according to claim 8 or 9, characterized in that, The microstructure of the zirconium-niobium alloy is a uniform Zr(Nb) solid solution.