High-strength molybdenum-niobium alloy and method for producing same

Abstract

This invention discloses a high-strength niobium-molybdenum alloy and its preparation method. The alloy, by atomic percentage, comprises: 13-31% molybdenum, 5-9% zirconium, and at least two elements selected from titanium, chromium, vanadium, and aluminum, with the balance being niobium and unavoidable impurities. The preparation method includes: firstly, weighing high-purity metal particle raw materials according to the designed proportions; employing vacuum induction suspension melting technology, fully melting the raw materials under vacuum conditions ≤5×10⁻³Pa and melting temperature 1800-2400℃; and obtaining a pre-alloy ingot through 3-5 inverted melting processes; subsequently, wrapping the pre-alloy ingot with tantalum foil and performing hot isostatic pressing densification treatment under high-purity argon protection at a pressure of 220-250 MPa and a temperature of 1300-1500℃ to obtain the high-strength niobium-molybdenum alloy. The alloy has a density of ≤8.8 g / cm³, a room temperature strength of ≥663 MPa, a 1000℃ strength of ≥397 MPa, and a 1600℃ strength of ≥127 MPa. Its comprehensive mechanical properties reach or exceed those of commercial C-3009 alloy. At the same time, it replaces expensive elements such as Hf and W with low-cost elements such as Mo and Zr, which significantly reduces the material cost.

Description

Technical Field

[0001] This invention belongs to the field of high-temperature alloy materials technology, specifically relating to a high-strength niobium-molybdenum alloy and its preparation method. Background Technology

[0002] Niobium-based superalloys are valuable in high-end fields such as aerospace due to their excellent high-temperature strength, corrosion resistance, and low density. Currently available commercial niobium alloys mainly include two grades: C-103 and C-3009. The C-103 alloy has a density of 8.86 g / cm³ and good cold formability, but its strength is low above 1000℃, making it difficult to meet the requirements of high-end high-temperature applications. The C-3009 alloy is strengthened by adding W and Hf elements, achieving yield strengths of 397 MPa and 388 MPa at 1000℃ and 1200℃ respectively, and can be used at 1600℃. However, its density is as high as 10.3 g / cm³, and Hf and W elements are expensive, resulting in high manufacturing costs and difficult processing.

[0003] In research on niobium-molybdenum based alloys, although the Nb-Mo-Ti system alloy density is controlled at 7.70~8.03 g / cm³, it has excellent room temperature ductility and strength at 20~1200℃ is better than C-103, but its strength above 600℃ is not as good as C-3009, and its high temperature stability is insufficient, making it difficult to meet the comprehensive requirements of aerospace and other fields for high-temperature, high-strength, low-cost, and low-density materials.

[0004] The existing technologies mainly have the following problems: First, traditional high-performance niobium alloys rely on high-density elements such as W and Hf, resulting in heavy materials that limit their application in scenarios with high lightweight requirements; Second, elements such as Hf and W are expensive and have complex processing techniques, resulting in high costs for alloy preparation and application; Third, although existing niobium-molybdenum based alloys have advantages in low density and room temperature performance, they lack high-temperature strength and stability, making it difficult to balance high-temperature mechanical properties and overall cost-effectiveness. Summary of the Invention

[0005] The purpose of this invention is to provide a high-strength niobium-molybdenum alloy and its preparation method, so as to solve the technical problems of existing niobium-based high-temperature alloys having high density, high cost, and insufficient high-temperature performance.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A high-strength niobium-molybdenum alloy, wherein the alloy comprises, by atomic percentage: 13-31% molybdenum, 5-9% zirconium, and at least two elements selected from titanium, chromium, vanadium and aluminum, with the balance being niobium and unavoidable impurities.

[0008] Furthermore, the alloy also contains 0.1-1% chromium and 1-3% aluminum by atomic percentage.

[0009] Furthermore, the alloy also contains 3-5% titanium and 0.1-1% vanadium by atomic percentage.

[0010] Furthermore, the density of the alloy is ≤8.8 g / cm³.

[0011] The present invention also provides a method for preparing the above-mentioned high-strength niobium-molybdenum alloy, comprising the following steps:

[0012] S1. Weigh out each metal particle raw material with a purity ≥99.9% according to the design ratio, place it in a water-cooled copper crucible, and use vacuum induction suspension melting technology to fully melt the raw material under the conditions of vacuum degree ≤5×10⁻³ Pa and melting temperature 1800~2400℃. After holding at the temperature for 5~15 min, solidify to obtain an alloy ingot. Turn the alloy ingot over and repeat the melting-solidification process 3~5 times to obtain a pre-alloyed ingot.

[0013] S2. The pre-alloyed ingot is wrapped with tantalum foil and placed in a hot isostatic press. Under the protective atmosphere of high-purity argon gas with a purity of ≥99.99%, it is densified at a pressure of 220~250 MPa, a temperature of 1300~1500℃, and a holding time of 1~2 h. After cooling, the high-strength niobium-molybdenum alloy is obtained.

[0014] Furthermore, in step S1, the heating power of the induction coil is first adjusted to 40~60 kW and kept at that temperature for 0.5~2 min to remove gas and establish initial suspension. Then, it is increased to 100~160 kW to fully melt the material. After complete melting, the power is turned back to 90~110 kW for electromagnetic suspension stirring.

[0015] Furthermore, in step S1, the electromagnetic levitation stirring time is 3~8 minutes.

[0016] Furthermore, in step S2, the thickness of the tantalum foil is 0.03~0.1 mm.

[0017] Furthermore, in step S2, after the densification treatment is completed, the temperature is first cooled to below 500°C, and then cooled to room temperature in the furnace.

[0018] The high-strength niobium-molybdenum alloy and its preparation method provided by this invention have the following beneficial effects:

[0019] By using Mo and Zr as the main alloying elements and introducing at least two elements from Ti, Cr, V, and Al for multi-element synergistic modification, the alloy exhibits both solid solution strengthening and grain refinement strengthening effects, resulting in excellent room temperature and high temperature mechanical properties. The room temperature strength is ≥663 MPa, the strength at 1000℃ is ≥397 MPa, and the strength at 1600℃ is ≥127 MPa, achieving overall mechanical properties at or above the level of commercial C-3009 alloy. Simultaneously, the alloy density is ≤8.8 g / cm³, significantly reducing raw material costs and material density by replacing expensive high-density elements such as Hf and W in traditional alloys with low-cost, low-density elements like Mo and Zr. Furthermore, the use of vacuum induction levitation melting combined with multiple inverted melting processes effectively ensures the uniformity of the alloy composition, while hot isostatic pressing densification eliminates internal porosity and microcracks. This two-step synergistic process provides a reliable technological guarantee for achieving the alloy's excellent comprehensive properties. Attached Figure Description

[0020] Figure 1 This is a photograph of the niobium-molybdenum alloy obtained in Example 1 of the present invention.

[0021] Figure 2 The image shows the microstructure of the niobium-molybdenum alloy obtained in Example 1 of this invention.

[0022] Figure 3 The image shows the microstructure of the niobium-molybdenum alloy obtained in Example 2 of this invention.

[0023] Figure 4 The image shows the microstructure of the niobium-molybdenum alloy obtained in Example 3 of this invention.

[0024] Figure 5 This is a microstructure diagram of the niobium-molybdenum alloy obtained in Example 4 of the present invention. Detailed Implementation

[0025] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. The following embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0026] Example 1

[0027] High-purity metal particles of grade 99.95% were weighed according to the ratio of 75.7%Nb-16.5%Mo-7.8%Zr (at.%), and then stacked from bottom to top in a water-cooled copper crucible of a suspension melting furnace in order of increasing melting point. The furnace cavity was first evacuated to ≤5×10⁻³ Pa, and then filled with high-purity argon. The induction coil was started and the temperature was slowly increased. The heating power of the induction coil was first adjusted to 50 kW and held for 1 minute to remove gas and establish initial suspension. Then it was increased to 110~150 kW, and finely adjusted according to the height of the molten pool and the suspension stability to ensure that the material was fully melted and did not come into contact with the crucible. After complete melting, the power was reduced to 98 kW, and the molten liquid was suspended in the center of the crucible by an electromagnetic field and forced to eddy current for 5 minutes to achieve uniform composition and float inclusions. After stirring, the melt was slowly cooled and solidified into an alloy ingot of Φ50 mm×70 mm through a water-cooled copper mold, and then removed from the furnace after 30 minutes of furnace cooling. Flip the ingot 180° and repeat the above melting-suspension-solidification cycle 3 times.

[0028] After peeling the ingot, wrap it with 0.05 mm thick tantalum foil, place it in a hot isostatic press, evacuate to ≤1×10⁻³Pa, and introduce high-purity argon gas to 220 MPa; heat to 1400℃ and hold for 2 h; after holding, cool to below 500℃, then cool to room temperature with the furnace, peel off the skin, and polish the surface to obtain the finished alloy ingot.

[0029] The density of the alloy was measured to be 8.6 g / cm³ using a densitometer. Tensile specimens required for room temperature and high temperature tests were fabricated on the sheet metal sample using a fast wire EDM. The measured strengths of this alloy were: 612 MPa at room temperature, 398 MPa at 1000℃, and 168 MPa at 1600℃.

[0030] The alloy sample of Example 1 is shown below. Figure 1 As shown, the microstructure is as follows Figure 2 As shown.

[0031] Example 2

[0032] High-purity metal particles of grade 99.95% were weighed according to the ratio of 60.6%Nb-30.8%Mo-8.6%Zr (at.%), and then stacked from bottom to top in a water-cooled copper crucible of a suspension melting furnace in order of increasing melting point. The furnace cavity was first evacuated to ≤5×10⁻³ Pa, and then filled with high-purity argon. The induction coil was started and the temperature was slowly increased. The heating power of the induction coil was first adjusted to 50 kW and held for 1 minute to remove gas and establish initial suspension. Then it was increased to 120~160 kW, and finely adjusted according to the height of the molten pool and the suspension stability to ensure that the material was fully melted and did not come into contact with the crucible. After complete melting, the power was reduced to 100 kW, and the molten liquid was suspended in the center of the crucible by an electromagnetic field and forced to eddy current for 5 minutes to achieve uniform composition and float inclusions. After stirring, the melt was slowly cooled and solidified into an alloy ingot of Φ50 mm×70 mm through a water-cooled copper mold, and then removed from the furnace after 30 minutes of furnace cooling. Flip the ingot 180° and repeat the above melting-suspension-solidification cycle 3 times.

[0033] After peeling the ingot, wrap it with 0.05 mm thick tantalum foil, place it in a hot isostatic press, evacuate to ≤1×10⁻³Pa, and introduce high-purity argon gas to 220 MPa; heat to 1450℃ and hold for 2 h; after holding, cool to below 500℃, then cool to room temperature with the furnace, peel off the skin, and polish the surface to obtain the finished alloy ingot.

[0034] The density of the alloy was measured to be 8.79 g / cm³ using a densitometer. The strength of this alloy was measured to be 674 MPa at room temperature, 447 MPa at 1000℃, and 196 MPa at 1600℃.

[0035] The microstructure of Example 2 is as follows Figure 3 As shown.

[0036] Example 3

[0037] High-purity metal particles of grade 99.95% were weighed according to the following ratio: 71.4%Nb-17.3%Mo-8.1%Zr-1%Cr-2.2%Al (at.%). These particles were then stacked from bottom to top in a water-cooled copper crucible of a suspension melting furnace, arranged in ascending order of melting point. The furnace chamber was first evacuated to ≤5×10⁻³ Pa, and then filled with high-purity argon. The induction coil was started and the temperature was slowly increased. The heating power was initially set to 50 kW and held for 1 minute to remove gas and establish initial suspension. The power was then increased to 110~140 kW, finely adjusted according to the height of the molten pool and suspension stability to ensure complete melting of the material without contact with the crucible. After complete melting, the power was reduced to 95 kW, and the molten liquid was suspended in the center of the crucible using an electromagnetic field and subjected to forced eddy current stirring for 5 minutes to achieve uniform composition and allow inclusions to float. After stirring, the melt is slowly cooled and solidified into an alloy ingot of Φ50 mm × 70 mm through a water-cooled copper mold. After furnace cooling for 30 minutes, the ingot is removed from the furnace. The ingot is then rotated 180° and the above melting-suspension-solidification cycle is repeated 3 times.

[0038] After peeling the ingot, wrap it with 0.05 mm thick tantalum foil, place it in a hot isostatic press, evacuate to ≤1×10⁻³Pa, and introduce high-purity argon gas to 200 MPa; heat to 1400℃ and hold for 2 h; after holding, cool to below 500℃, and then cool to room temperature with the furnace, peel off the skin, and polish the surface to obtain the finished alloy ingot.

[0039] The density of the alloy was measured to be 8.48 g / cm³ using a densitometer. The yield strength of this alloy was measured to be 784 MPa at room temperature, 435 MPa at 1000℃, and 131 MPa at 1600℃.

[0040] The microstructure of Example 3 is as follows Figure 4 As shown.

[0041] Example 4

[0042] High-purity metal particles of grade 99.95% were weighed according to the following ratio: 72.6%Nb-13.1%Mo-8.2%Zr-4.9%Ti-1%V (at.%). These particles were then stacked from bottom to top in a water-cooled copper crucible of a suspension melting furnace, arranged in ascending order of melting point. The furnace chamber was first evacuated to ≤5×10⁻³ Pa, and then filled with high-purity argon. The induction coil was started and the temperature was slowly increased. The heating power was initially set to 50 kW and held for 1 minute to remove gas and establish initial suspension. The power was then increased to 110~140 kW, finely adjusted according to the height of the molten pool and suspension stability to ensure complete melting of the material without contact with the crucible. After complete melting, the power was reduced to 95 kW, and the molten liquid was suspended in the center of the crucible using an electromagnetic field and subjected to forced eddy current stirring for 5 minutes to achieve uniform composition and allow inclusions to float. After stirring, the melt is slowly cooled and solidified into an alloy ingot of Φ50 mm × 70 mm through a water-cooled copper mold. After furnace cooling for 30 minutes, the ingot is removed from the furnace. The ingot is then rotated 180° and the above melting-suspension-solidification cycle is repeated 3 times.

[0043] After peeling the ingot, wrap it with 0.05 mm thick tantalum foil, place it in a hot isostatic press, evacuate to ≤1×10⁻³Pa, and introduce high-purity argon gas to 200 MPa; heat to 1400℃ and hold for 2 h; after holding, cool to below 500℃, and then cool to room temperature with the furnace, peel off the skin, and polish the surface to obtain the finished alloy ingot.

[0044] The density of the alloy was measured to be 8.33 g / cm³ using a densitometer. The yield strength of this alloy was measured to be 710 MPa at room temperature, 398 MPa at 1000℃, and 152 MPa at 1600℃.

[0045] The microstructure of Example 4 is as follows Figure 5 As shown.

[0046] Comparative Example 1 (using conventional C-103 alloy)

[0047] A commercially available C-103 alloy (composition: Nb-10Hf-1Ti-0.7Zr, at.%) was used as a comparative example. The C-103 alloy has a density of 8.86 g / cm³, a room temperature tensile strength of approximately 295 MPa, and a strength of less than 150 MPa at 1000℃.

[0048] Comparative Example 2 (using conventional C-3009 alloy)

[0049] A commercially available C-3009 alloy (composition: Nb-22.4Hf-5.9W, at.%) was used as a comparative example. The C-3009 alloy has a density of 10.3 g / cm³, and yield strengths of 395 MPa and 388 MPa at 1000℃ and 1200℃, respectively. Although C-3009 exhibits high high-temperature strength, its density is significantly greater than that of the alloy in the embodiments of this invention (8.33~8.79 g / cm³), and the Hf and W elements in the raw materials are expensive, resulting in a significantly higher preparation cost compared to the alloy of this invention.

[0050] The performance comparison of each embodiment and comparative example is shown in the table below:

[0051] serial number Ingredients (at.%) Density (g / cm³) Room temperature strength (MPa) Strength at 1000℃ (MPa) Strength at 1600℃ (MPa) Example 1 75.7Nb-16.5Mo-7.8Zr 8.60 612 398 168 Example 2 60.6Nb-30.8Mo-8.6Zr 8.79 674 447 196 Example 3 71.4Nb-17.3Mo-8.1Zr-1Cr-2.2Al 8.48 784 435 131 Example 4 72.6Nb-13.1Mo-8.2Zr-4.9Ti-1V 8.33 710 398 152 Comparative Example 1 (C-103) Nb-10Hf-1Ti-0.7Zr 8.86 295 145 - Comparative Example 2 (C-3009) Nb-22.4Hf-5.9W 10.3 - 395 -

[0052] As shown in the table above, the alloy densities of all embodiments of the present invention are ≤8.8 g / cm³, significantly lower than the 10.3 g / cm³ of C-3009 alloy, and comparable to C-103 alloy. Regarding mechanical properties, Example 2 achieves strengths of 447 MPa and 196 MPa at 1000℃ and 1600℃ respectively, both superior to C-3009 alloy; Example 3 achieves a room temperature strength of 784 MPa, the highest among all embodiments. In summary, the alloys of the present invention achieve a good balance in terms of density, cost, and mechanical properties, overcoming the shortcomings of existing niobium-based high-temperature alloys.

Claims

1. A high-strength niobium-molybdenum alloy, characterized in that, The alloy, by atomic percentage, comprises: 13-31% molybdenum, 5-9% zirconium, and at least two elements selected from titanium, chromium, vanadium, and aluminum, with the balance being niobium and unavoidable impurities.

2. The high-strength niobium-molybdenum alloy according to claim 1, characterized in that, The alloy also contains 0.1-1% chromium and 1-3% aluminum by atomic percentage.

3. The high-strength niobium-molybdenum alloy according to claim 1, characterized in that, The alloy also contains 3-5% titanium and 0.1-1% vanadium by atomic percentage.

4. The high-strength niobium-molybdenum alloy according to any one of claims 1 to 3, characterized in that, The density of the alloy is ≤8.8 g / cm³.

5. A method for preparing a high-strength niobium-molybdenum alloy as described in any one of claims 1 to 4, characterized in that, Includes the following steps: S1. Weigh out each metal particle raw material with a purity ≥99.9% according to the design ratio, place it in a water-cooled copper crucible, and use vacuum induction suspension melting technology to fully melt the raw material under the conditions of vacuum degree ≤5×10⁻³ Pa and melting temperature 1800~2400℃. After holding at the temperature for 5~15 min, solidify to obtain an alloy ingot. Turn the alloy ingot over and repeat the melting-solidification process 3~5 times to obtain a pre-alloyed ingot. S2. The pre-alloyed ingot is wrapped with tantalum foil and placed in a hot isostatic press. Under the protective atmosphere of high-purity argon gas with a purity of ≥99.99%, it is densified at a pressure of 220~250 MPa, a temperature of 1300~1500℃, and a holding time of 1~2 h. After cooling, the high-strength niobium-molybdenum alloy is obtained.

6. The preparation method according to claim 5, characterized in that, In step S1, the heating power of the induction coil is first adjusted to 40~60 kW and kept at that temperature for 0.5~2 min to remove gas and establish initial suspension. Then, the power is increased to 100~160 kW to fully melt the material. After complete melting, the power is turned back to 90~110 kW for electromagnetic suspension stirring.

7. The preparation method according to claim 5, characterized in that, In step S1, the electromagnetic levitation stirring time is 3~8 min.

8. The preparation method according to claim 5, characterized in that, In step S2, the thickness of the tantalum foil is 0.03~0.1 mm.

9. The preparation method according to claim 5, characterized in that, In step S2, after the densification process is completed, the temperature is first cooled to below 500°C, and then cooled to room temperature in the furnace.

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