A high-strength, high-corrosion-resistance, low-cost titanium alloy for spent fuel reprocessing and a preparation method thereof

Abstract

The application discloses a high-strength, high-corrosion-resistance and low-cost titanium alloy suitable for spent fuel reprocessing and a preparation method thereof, and belongs to the field of structural materials for spent fuel reprocessing. The chemical composition of the titanium alloy comprises the following components in percentage by mass: Al 4%, Zr 3%, V 0.5%-5.0%, H <0.008%, O <0.08%, N <0.04%, C <0.08%, and the balance Ti. The preparation method comprises the following steps: raw material drying and preheating, vacuum / argon protection smelting, overturning remelting, casting and hot forging. The forging breakdown temperature is 1000 DEG C, the final forging temperature is greater than or equal to 880 DEG C, the cumulative deformation is 40+ / -5%, the strain rate is 3 s ‑1 ~8 s ‑1 . The alloy has excellent corrosion rate and high yield strength in 6 mol / L HNO3 containing oxidizing ions at 100 DEG C, and is suitable for corrosion-resistant load-bearing components of spent fuel reprocessing equipment.

Description

Technical Field

[0001] This invention belongs to the field of structural materials for spent fuel reprocessing, specifically relating to a high-strength, high-corrosion-resistant, low-cost titanium alloy suitable for spent fuel reprocessing and its preparation method. Background Technology

[0002] Currently, the PUREX (Plutonium-Uranium Oxidation-Reduction Extraction) process is widely used internationally for spent fuel reprocessing. The core equipment of this process, such as the continuous dissolver and the high-level radioactive waste evaporator, operates continuously in a high-concentration, high-temperature (typically reaching boiling point, such as 100℃~120℃) nitric acid medium. Simultaneously, the solution is enriched with a large amount of highly oxidizing fission product ions and corrosion product ions (such as Ce). 4+ Cr 6+ V 5+ The presence of these high-valence ions generates strong cathodic depolarization, causing a sharp increase in the redox potential of the material surface (reaching over 1.2 V with a standard hydrogen electrode as a reference), far exceeding the overpassivation potential of conventional stainless steel. This easily breaks through the passivation film of conventional metallic materials, leading to problems such as intergranular corrosion and uniform corrosion, resulting in catastrophic equipment failure. Furthermore, core moving components such as the stirring shaft, centrifuge rotor, and pump shaft are also subjected to complex alternating stresses and wear loads. Therefore, the structural components of spent fuel reprocessing equipment place extremely stringent dual requirements on the corrosion resistance and mechanical load-bearing capacity of the materials.

[0003] Currently, the main technical bottlenecks for candidate materials used in the manufacture of equipment for highly corrosive environments in spent fuel reprocessing engineering are as follows:

[0004] (1) Special stainless steel materials:

[0005] Ultra-low carbon austenitic stainless steels such as 304ULC, 316ULC, and 310ULC are representative examples. These materials have low cost, good processing performance, and a certain degree of structural strength. However, in the high-temperature boiling nitric acid environment containing strong oxidizing ions, the chromium passivation film on the stainless steel surface is extremely prone to over-passivation dissolution, leading to severe intergranular corrosion and sensitization problems. The corrosion rate generally exceeds 0.5 mm / year, which cannot meet the service requirements of nuclear-grade equipment with a design life of 40-60 years. Therefore, stainless steel is difficult to use as a key structural material in reprocessing equipment that directly contacts high-temperature concentrated nitric acid.

[0006] (2) Pure titanium and near-α titanium alloys:

[0007] Industrial pure titanium, such as TA2 and TA10, is a prime example. Pure titanium and low-alloy titanium alloys exhibit excellent resistance to uniform corrosion in strongly oxidizing nitric acid due to the TiO2 passivation film formed on their surface (corrosion rate typically <0.05 mm / year). However, the microstructure of these materials is usually composed of coarse equiaxed α grains, resulting in relatively low room temperature yield strength (approximately 350 MPa for TA2 and 480 MPa for TA10). Under the high stress, high speed, and heavy load conditions of large-scale post-processing equipment, the structural load-bearing capacity and wear resistance of pure titanium and low-strength titanium alloys are severely insufficient, making them unsuitable for use as critical load-bearing structural components.

[0008] (3) Corrosion-resistant titanium alloys containing refractory precious metals:

[0009] Examples of titanium alloys include Ti35 (Ti-6Ta), Ti-5Ta, Grade 7 (Ti-0.15Pd), and Grade 12 (Ti-0.3Mo-0.8Ni). To balance strength and corrosion resistance, existing technologies often incorporate elements such as Ta, Pd, Ru, and Mo into the titanium matrix. Among these, Ti35 alloy is currently the most widely used high-corrosion-resistant titanium alloy in China's spent fuel reprocessing field, exhibiting good corrosion resistance in high-temperature concentrated nitric acid. However, this type of alloy has three inherent drawbacks: First, its cost is extremely high. Ta is a rare refractory metal, with a market price approximately 10 to 20 times that of titanium, resulting in a persistently high raw material cost for Ti35 alloy (3 million yuan per ton), severely restricting its widespread application in large-scale equipment. Second, smelting is difficult. Ta has a melting point as high as 2996℃, far exceeding that of titanium (1668℃), requiring higher energy input and more complex process control during smelting. This easily leads to compositional segregation and unmelted Ta inclusions, reducing the yield. Thirdly, there is the risk of nuclear contamination from Ni-containing alloys. Some Ni-containing titanium alloys (such as Grade 12) are prone to producing long-lived radioactive isotopes under neutron irradiation. 63 Ni increases the difficulty of waste disposal and the risk of radiation exposure for personnel.

[0010] (4) "Technological bias" regarding element V in the prior art:

[0011] In the field of titanium alloy research, vanadium (V) is one of the most commonly used β-stabilizing elements, widely used to improve the strength of titanium alloys (a typical example being Ti-6Al-4V). However, in the field of high corrosion-resistant titanium alloys for spent fuel reprocessing, there has long been a prevalent technical bias: the belief that V undergoes a change in valence and dissolution in high-temperature, strongly oxidizing nitric acid (V2O ... 4+ / V 5+This generates additional redox reactions, damaging the integrity and stability of the passivation film and severely impairing the material's corrosion resistance. Therefore, existing high-corrosion-resistant titanium alloys (such as Ti35, Grade 7, and Grade 12) deliberately avoid V, instead using more "inert" elements like Ta, Nb, and Pd. This technological bias has long constrained the development of low-cost, high-strength, and highly corrosion-resistant titanium alloys, often leaving engineering applications facing a dilemma of either insufficient strength, excessive cost, or decreased corrosion resistance.

[0012] In summary, existing structural materials for spent fuel reprocessing struggle to achieve a good balance between cost, strength, and corrosion resistance. Pure titanium and low-strength titanium alloys lack sufficient strength; corrosion-resistant titanium alloys containing elements such as Ta and Pd are expensive and difficult to smelt; and stainless steel's corrosion resistance does not meet requirements. More importantly, due to the long-standing technological bias that "V will severely impair corrosion resistance," there has been a lack of a low-cost titanium alloy solution that does not contain expensive refractory / precious metals and can simultaneously achieve high strength and excellent resistance to high-temperature nitric acid corrosion.

[0013] Therefore, there is an urgent need in this field to develop a new titanium alloy material to break away from the dependence on expensive refractory precious metals in order to control costs. At the same time, it is necessary to ensure that the material can form a dense, continuous and self-healing composite passivation film in a high-temperature boiling nitric acid environment containing high-valence oxidizing ions, while significantly improving the mechanical strength of the material, through precise alloying design and microstructure control. This will meet the urgent needs of the nuclear industry for low-cost, high-strength, and long-life structural materials. Summary of the Invention

[0014] Addressing the prominent issues of existing high-corrosion-resistant titanium alloys for spent fuel reprocessing, which generally rely on the addition of high-melting-point refractory metals (such as Ta and Mo) or expensive precious metals (such as Pd), leading to high costs and smelting difficulties, or containing easily activated elements (such as Ni) that pose a nuclear contamination risk, and the traditional technological bias that V element would severely impair corrosion resistance and is therefore deliberately avoided, this invention aims to provide a high-strength, high-corrosion-resistant, low-cost titanium alloy suitable for spent fuel reprocessing, free of Ta, Nb, Mo, W, Pd, Pt, Ru, and Ni elements, as well as its preparation method. Through systematic component screening and performance evaluation, this invention is the first to discover that adding 0.5% to 5.0% V to a Ti-4Al-3Zr matrix, combined with an optimized forging process, can achieve a synergistic effect of "high strength, high corrosion resistance, and low cost," with the optimal overall performance achieved at a V content of 1%. This discovery breaks through long-standing technological biases and provides a completely new technical solution for structural materials used in spent fuel reprocessing.

[0015] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0016] A method for preparing a high-strength, high-corrosion-resistant, and low-cost titanium alloy suitable for spent fuel reprocessing includes the following key steps:

[0017] S1: Material preparation;

[0018] Weigh the required amounts of titanium, aluminum, zirconium, and vanadium raw materials, and preheat each raw material at 110℃~160℃; the chemical composition of the titanium alloy, by mass percentage, is: Al 4%, Zr 3%, V 0.5%~5.0% and unavoidable impurity elements: H<0.008%, O<0.08%, N<0.04%, C<0.08%, with the balance being Ti;

[0019] S2: Vacuum melting;

[0020] The preheated raw materials are loaded into a water-cooled crucible. The furnace is evacuated to a high vacuum of 0.02 Pa and then filled with argon gas at a pressure of 0.08 MPa to form an inert protective atmosphere. Melting is carried out at 1950℃~2050℃.

[0021] S3: Casting;

[0022] The melt is poured and then cooled after pouring.

[0023] S4: Forging;

[0024] For forging titanium alloy ingots, the initial deformation is first carried out by rough forging at a temperature in the β phase region or near the β phase region to break the coarse as-cast structure. Then, the fine forging deformation in the α+β two-phase region is carried out at the forging temperature, with a final forging temperature ≥880℃.

[0025] In the above preparation method:

[0026] In step S1, industrial-grade sponge titanium with a purity ≥ 99.5% and metallic aluminum, metallic zirconium, and metallic vanadium with a purity ≥ 99.5% are selected as raw materials.

[0027] In step S2, the cold water inlet temperature of the water-cooled crucible furnace is 11℃~12℃, and the ambient temperature water inlet temperature is 28℃~30℃.

[0028] In step S2, melting is carried out at 1950℃~2050℃ for 10~15 minutes. To ensure high uniformity of alloy composition, the ingot is then turned over and melted 3~5 times at the same melting temperature and time. This temperature range ensures that all components are fully melted while avoiding excessive volatilization loss and crucible contamination risks caused by excessively high temperatures.

[0029] In step S3, the ingot tapping temperature is set to 20℃~40℃. After sufficient melting and homogenization, the melt is poured into a preheated mold. After pouring, the ingot is slowly cooled in the furnace under an inert atmosphere or air-cooled after tapping. This controlled cooling method reduces the internal stress of the ingot and avoids microstructure segregation and crack defects caused by rapid cooling, ultimately obtaining a titanium alloy ingot with uniform microstructure, few defects, and low internal stress.

[0030] In step S4, the β-phase region starting temperature is 1000℃, the cumulative deformation is 40±5%, and the strain rate is 3 s. -1 ~8 s -1 This combination of process parameters aims to achieve significant grain refinement through sufficient dynamic recrystallization, improve microstructure uniformity and density, eliminate casting defects, and provide a good foundation for subsequent heat treatment.

[0031] In the above preparation method, the V content in the titanium alloy is 2.0%~4.0% by mass percentage, which is suitable for application scenarios with higher strength requirements and less stringent requirements for corrosion resistance.

[0032] Furthermore, the titanium alloy contains 1.0% V, a composition that has been experimentally proven to exhibit excellent corrosion resistance and mechanical properties: at 100°C, with a V content... 5+ Cr 6+ Ce 4+ In a 6 mol / L HNO3 solution, the polarization resistance R of this titanium alloy p =1932 Ω·cm 2 The corrosion rate is 0.008 mm / year, the yield strength is 798 MPa, and the tensile strength is 815 MPa. Its overall performance is superior to that of commercial Ti35 alloy.

[0033] A high-strength, high-corrosion-resistant, low-cost titanium alloy suitable for spent fuel reprocessing is prepared by the above-mentioned preparation method for a high-strength, high-corrosion-resistant, low-cost titanium alloy suitable for spent fuel reprocessing.

[0034] The titanium alloy does not contain elements such as Ta, Nb, Mo, W, Pd, Pt, Ru, or Ni.

[0035] The beneficial effects of this invention are as follows: First, this invention breaks the long-standing technical prejudice in the industry that "vanadium inevitably impairs the corrosion resistance of titanium alloys in strongly oxidizing nitric acid." For the first time, a performance window effect of 0.5%~5.0% vanadium content was discovered in a Ti-4Al-3Zr matrix, achieving a synergistic unity of high strength and high corrosion resistance in the material. Traditionally, it is believed that vanadium, as a variable valence element, undergoes a V2 reaction in high-temperature strongly oxidizing nitric acid systems. 4+ / V 5+Redox reactions disrupt the structure of the TiO2 passivation film; therefore, existing high corrosion-resistant titanium alloys such as Ti35 and Grade 7 avoid vanadium and use inert elements such as Ta and Pd. This invention demonstrates that when the vanadium content is within the aforementioned window range, vanadium can, on the one hand, generate stable V2O5 and VO2 compounds at the passivation film-matrix interface, filling microscopic defects in the TiO2 passivation film and improving film density and stability; on the other hand, vanadium, as a β-eutectoid stabilizing element, can introduce fine and dispersed β phases, improving mechanical properties through the dual effects of grain refinement strengthening and precipitation strengthening. Experimental results show that when the vanadium content is 1%, the alloy exhibits a corrosion rate as low as 0.008 mm / year in a 6 mol / L nitric acid solution containing strong oxidizing ions at 100℃, with a yield strength reaching 798 MPa, representing an improvement of over 12.5% ​​compared to a vanadium-free matrix. Its overall performance is superior to commercially available Ti35 alloys.

[0036] Secondly, this invention completely abandons the expensive refractory metals and precious metals such as Ta and Pd commonly used in existing high corrosion-resistant titanium alloys, using only three low-cost alloying elements: Al, Zr, and V. Furthermore, it does not add easily activated nickel, resulting in significant overall advantages. Using Ti35 (Ti-6Ta) alloy as a reference, the cost of raw materials for this invention is reduced by more than 80%. The market price of Ti35 is approximately 3 million RMB per ton, while the vanadium, zirconium, and aluminum raw materials used in this invention are inexpensive, greatly improving the economic efficiency of the project. Since tantalum, with a melting point as high as 2996℃, is no longer added, the alloy melting temperature can be controlled between 1950℃ and 2050℃, completely avoiding melting defects such as infusible inclusions and component segregation caused by high-melting-point elements. In addition, the alloy does not contain easily activated nickel components found in materials such as Grade 12, thus avoiding the formation of long-lived radioactive isotopes under neutron irradiation. 63 Ni effectively reduces the risks of radioactive contamination and waste disposal, and has stronger nuclear-grade compatibility.

[0037] Third, this invention constructs a proprietary forging process precisely matched to the alloy composition, forming a synergistic control system across the entire chain of "composition-forging process-microstructure-properties." This differs from conventional titanium alloys with a ≤1 s... -1 Compared to low-strain-rate forging and isothermal forging which requires a high-cost mold heating system, this invention controls the forging strain rate to 3 s. -1 ~8 s -1 Within the mid-to-high range, the following process parameters were determined: β-phase region initial billet temperature 1000℃, final forging temperature ≥880℃, and cumulative engineering strain 40±5%. This parameter combination offers significant advantages: the strain rate is below the adiabatic shear instability threshold of titanium alloys by 10 s. -1 This ensures complete forging and uniform structure; processing can be completed using ordinary high-speed forging machines and presses, eliminating the need for expensive isothermal forging equipment and lowering the threshold for industrialization.

[0038] Fourth, this invention is equipped with a complete experimental verification system, and the technical solution is well-supported and highly reliable. The invention includes six sets of examples, covering the entire vanadium content range of 0% to 5%, and incorporates electrochemical polarization curves (…). Figure 1 ), polarization resistor ( Figure 2 ), Immersion corrosion rate ( Figure 3 ), room temperature tensile properties ( Figure 4 Multiple testing methods, including [list of methods], were used to fully reveal the quantitative influence of vanadium content on the corrosion resistance and mechanical properties of the alloy. A performance comparison between vanadium content of 1% (Example 2) and 5% (Example 6) directly verified the significant increase in corrosion rate when the vanadium content exceeds the specified window range, providing solid experimental support for the vanadium element window effect. The alloy of this invention exhibits excellent performance in high-temperature nitric acid flow corrosion, electrochemical conditions, and heavy-duty load-bearing components, fully meeting the requirements of spent fuel reprocessing equipment for low-cost, high-strength, and long-life structural materials, and has broad engineering application prospects. Attached Figure Description

[0039] Figure 1 The titanium alloys prepared in Examples 1-6 of this invention contain strong oxidizing ions (V2) at 100°C. 5+ Cr 6+ Ce 4+ The potentiodynamic polarization curves were obtained by electrochemical corrosion tests in a 6 mol / L nitric acid solution. The results showed that all alloys in the examples exhibited a wide and stable passivation region, indicating their excellent passivation ability and corrosion resistance.

[0040] Figure 2 The polarization resistance (R) of the titanium alloys prepared in Examples 1-6 of this invention was obtained by fitting electrochemical impedance spectroscopy (EIS). p R value. p The higher the value, the stronger the corrosion resistance of the material. The results show that the R value of Example 1 (0% V) is... p The highest value (2524 Ω·cm) 2 ( ), with the best corrosion resistance.

[0041] Figure 3 The titanium alloys prepared in Examples 1-6 of this invention contain various oxidizing ions (V2) under high temperature conditions of 100°C. 5 + Cr 6+ Ce 4+ The results of comparing the average corrosion rates after soaking in a 6 mol / L nitric acid solution for 10 days.

[0042] Figure 4The data are engineering stress-strain curves obtained from tensile tests conducted at room temperature on the titanium alloys prepared in Examples 1-6 of this invention. The results show that the addition of V significantly improves the strength of the alloy, but at the cost of some plasticity, and the peak strength is reached when the V content reaches 4 wt.%. Detailed Implementation

[0043] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the scope of protection of the present invention is not limited to these embodiments. Experimental methods not specifically described in the embodiments are generally carried out under conventional conditions. All raw materials used are commercially available industrial-grade products with a purity ≥99.5%.

[0044] Performance testing methods:

[0045] The titanium alloys obtained in the embodiments and comparative examples of this invention were tested for corrosion resistance and mechanical properties under the same conditions. The corrosion test solution was 6 mol / L HNO3, with added oxidizing metal ions, including Ce. 4+ The concentration was 2.06 g / L, V 5+ The concentration was 1.70 g / L, Cr 6+ The concentration was 0.125 g / L. The test temperature was 100℃. The immersion corrosion test lasted for 10 days. Samples were cleaned, dried, and weighed before and after the test. The corrosion rate was calculated using the weight loss method, with the following formula:

[0046]

[0047] Where CR is the corrosion rate, in mm / year; Δm is the mass loss before and after corrosion, in g; and ρ is the alloy density, in g / cm³. 3 S represents the exposed area of ​​the sample, in cm². 2 t represents the soaking time in hours (h). Each component should be tested in at least three parallel trials, and the average value of the results should be taken.

[0048] Electrochemical testing employed a three-electrode system, with the titanium alloy sample as the working electrode, a platinum electrode as the counter electrode, and a saturated calomel electrode as the reference electrode. A salt bridge was used to isolate the reference electrode from the high-temperature nitric acid solution. Before testing, the open-circuit potential was monitored for 30 min. Subsequently, electrochemical impedance spectroscopy (EIS) was performed in the frequency range of 10 kHz to 0.01 Hz, with an AC perturbation voltage amplitude of 10 mV. The potentiodynamic polarization (PVP) test was conducted at a scan rate of 0.5 mV / s, covering a range from 0.5 V to 2.0 V negative relative to the open-circuit potential (SCE).

[0049] The room temperature tensile test was conducted according to GB / T 228.1-2021. Tensile specimens were sampled along the rolling direction of the sheet and prepared by machining. The specimen surface was sanded to remove oxide scale. The tensile strain rate was 10... -3 s -1 Each component requires at least three parallel samples, and the results are averaged.

[0050] Example 1

[0051] The high-strength, high-corrosion-resistant, low-cost titanium alloy (Ti-4Al-3Zr) suitable for spent fuel reprocessing prepared in this embodiment has the following chemical composition by mass percentage: Al 4.0%, Zr 3.0%, unavoidable impurities: H < 0.008%, O < 0.08%, N < 0.04%, C < 0.08%, balance Ti. The preparation process steps are as follows:

[0052] Preparation: Weigh out sponge titanium, aluminum granules and sponge zirconium with a purity of ≥99.5% according to the proportion, and dry them at 150℃ for 2 hours to remove the moisture and gas adsorbed on the surface.

[0053] Vacuum melting: The raw materials are placed into a water-cooled crucible furnace (the inlet water temperature of the water-cooled crucible furnace is 11℃~12℃, and the inlet water temperature of room temperature is 28℃~30℃). After evacuating to 0.02 Pa, high-purity argon gas with a purity ≥99.999% is backfilled to 0.08 MPa to form an inert protective atmosphere. Melting is carried out at 1950℃~2000℃ for 15 minutes, and the melting is repeated 5 times by turning the furnace.

[0054] Casting: After casting, the ingot is cooled to 20°C and then removed from the furnace.

[0055] Forging: The ingot is heated to 1000℃ and held for 1 hour. The initial forging deformation is about 20%. Then, it is drawn in multiple passes at 900℃~950℃, with a cumulative deformation of 40%. The strain rate is controlled at 5 s. -1 The final forging temperature is around 900℃, and the material is air-cooled.

[0056] Performance characterization: at 100℃, containing V 5+ Cr 6+ Ce 4+ In a 6 mol / L HNO3 solution, the potentiodynamic polarization curve of this alloy is as follows: Figure 1 Polarization resistance R p 2524 Ω·cm 2 ( Figure 2 The corrosion rate after immersion for 10 days was 0.007 mm / year. Figure 3 The room temperature yield strength is 709 MPa and the tensile strength is 723 MPa. Figure 4 This alloy has excellent corrosion resistance but the lowest strength.

[0057] Example 2

[0058] The high-strength, high-corrosion-resistant, low-cost titanium alloy (Ti-4Al-3Zr-1V) suitable for spent fuel reprocessing prepared in this embodiment has the following chemical composition by mass percentage: Al 4.0%, Zr 3.0%, V 1.0%, with impurity control as in Example 1. The preparation process is the same as in Example 1.

[0059] Performance characterization: Test conditions were the same as in Example 1, at 100°C and containing V. 5+ Cr 6+ Ce 4+ In a 6 mol / L HNO3 solution, the potentiodynamic polarization curve of this alloy is as follows: Figure 1 R p =1932 Ω·cm 2 ( Figure 2 Corrosion rate 0.008 mm / year ( Figure 3 Yield strength 798 MPa, tensile strength 815 MPa Figure 4 Compared with Example 1, the strength is increased by about 12.5%, the corrosion resistance is slightly reduced but still meets the nuclear engineering superior grade standard (<0.1 mm / year), and the overall performance is optimal.

[0060] Example 3

[0061] The high-strength, high-corrosion-resistant, low-cost titanium alloy (Ti-4Al-3Zr-2V) suitable for spent fuel reprocessing prepared in this embodiment has the following chemical composition by mass percentage: Al 4.0%, Zr 3.0%, V 2.0%. Impurity control is the same as in Example 1, and the preparation process is the same as in Example 1.

[0062] Performance characterization: Test conditions were the same as in Example 1, at 100°C and containing V. 5+ Cr 6+ Ce 4+ In a 6 mol / L HNO3 solution, the potentiodynamic polarization curve of this alloy is as follows: Figure 1 R p =1622 Ω·cm 2 ( Figure 2 Corrosion rate: 0.014 mm / year Figure 3 Yield strength 805 MPa, tensile strength 833 MPa Figure 4 ).

[0063] Example 4

[0064] The high-strength, high-corrosion-resistant, low-cost titanium alloy (Ti-4Al-3Zr-3V) suitable for spent fuel reprocessing prepared in this embodiment has the following chemical composition by mass percentage: Al 4.0%, Zr 3.0%, V 3.0%. Impurity control is the same as in Example 1, and the preparation process is the same as in Example 1.

[0065] Performance characterization: Test conditions were the same as in Example 1, at 100°C and containing V. 5+ Cr 6+ Ce 4+ In a 6 mol / L HNO3 solution, the potentiodynamic polarization curve of this alloy is as follows: Figure 1 R p =1479 Ω·cm 2 ( Figure 2 Corrosion rate: 0.026 mm / year Figure 3 Yield strength 831 MPa, tensile strength 838 MPa Figure 4 ).

[0066] Example 5

[0067] The high-strength, high-corrosion-resistant, low-cost titanium alloy (Ti-4Al-3Zr-4V) suitable for spent fuel reprocessing prepared in this embodiment has the following chemical composition by mass percentage: Al 4.0%, Zr 3.0%, V 4.0%. Impurity control is the same as in Example 1, and the preparation process is the same as in Example 1.

[0068] Performance characterization: Test conditions were the same as in Example 1, at 100°C and containing V. 5+ Cr 6+ Ce 4+ In a 6 mol / L HNO3 solution, the potentiodynamic polarization curve of this alloy is as follows: Figure 1 R p =1220 Ω·cm 2 ( Figure 2 Corrosion rate: 0.042 mm / year Figure 3 Yield strength 880 MPa, tensile strength 904 MPa (peak strength) Figure 4 ).

[0069] Example 6

[0070] The high-strength, high-corrosion-resistant, low-cost titanium alloy (Ti-4Al-3Zr-5V) suitable for spent fuel reprocessing prepared in this embodiment has the following chemical composition by mass percentage: Al 4.0%, Zr 3.0%, V 5.0%. The impurity control is the same as in Example 1, and the preparation process is the same as in Example 1.

[0071] Performance characterization: Test conditions were the same as in Example 1, at 100°C and containing V. 5+ Cr6+ Ce 4+ In a 6 mol / L HNO3 solution, the potentiodynamic polarization curve of this alloy is as follows: Figure 1 R p =999 Ω·cm 2 ( Figure 2 ), corrosion rate 0.060 mm / year ( Figure 3 Yield strength 836 MPa, tensile strength 862 MPa Figure 4 ).

[0072] It should be noted that this invention selects 3 seconds. -1 ~8 s -1 The higher strain rate is based on the following process considerations: compared to the 0.001 s required for isothermal forging or superplastic forming. -1 ~0.1 s -1 The extremely low strain rate allows the parameter range of this invention to be achieved on a conventional high-speed forging machine or press, avoiding expensive die heating systems and significantly lowering the engineering threshold; simultaneously, this rate is controlled within the typical adiabatic shear instability threshold of titanium alloys (10 s⁻¹). -1 The following ensures the uniformity of the microstructure and the integrity of the forming process during forging.

[0073] The above embodiments fully verify the alloy composition (Al 4%, Zr 3%, V 0.5%~5.0%) and preparation process (3~5 times of tumbling melting, forging strain rate 3 s) of the present invention. -1 ~8 s -1 The effectiveness and necessity of the deformation amount (40±5%) were discussed. Example 2 (V=1%) demonstrated the optimal combination of "high strength-high corrosion resistance-low cost". All equivalent substitutions, improvements, or combinations made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A method for preparing a high-strength, high-corrosion-resistant, low-cost titanium alloy suitable for spent fuel reprocessing, characterized in that, This includes the following key steps: S1: Material preparation; Weigh the required amounts of titanium, aluminum, zirconium, and vanadium raw materials, and preheat each raw material at 110℃~160℃; the chemical composition of the titanium alloy, by mass percentage, is: Al 4%, Zr 3%, V 0.5%~5.0% and unavoidable impurity elements: H<0.008%, O<0.08%, N<0.04%, C<0.08%, with the balance being Ti; S2: Vacuum melting; The preheated raw materials are loaded into a water-cooled crucible. The furnace is evacuated to a high vacuum of 0.02 Pa and then filled with argon gas at a pressure of 0.08 MPa to form an inert protective atmosphere. Melting is carried out at 1950℃~2050℃. S3: Casting; The melt is poured and then cooled after pouring. S4: Forging; For forging titanium alloy ingots, the initial deformation is first carried out by rough forging at a temperature in the β phase region or near the β phase region to break the coarse as-cast structure. Then, the fine forging deformation in the α+β two-phase region is carried out at the forging temperature, with a final forging temperature ≥880℃.

2. The method for preparing high-strength, high-corrosion-resistant, low-cost titanium alloy suitable for spent fuel reprocessing according to claim 1, characterized in that, In step S1, industrial-grade sponge titanium with a purity ≥ 99.5% and metallic aluminum, metallic zirconium, and metallic vanadium with a purity ≥ 99.5% are selected as raw materials.

3. The method for preparing a high-strength, high-corrosion-resistant, low-cost titanium alloy suitable for spent fuel reprocessing according to claim 1, characterized in that, In step S2, the cold water inlet temperature of the water-cooled crucible furnace is 11℃~12℃, and the ambient temperature water inlet temperature is 28℃~30℃.

4. The method for preparing a high-strength, high-corrosion-resistant, low-cost titanium alloy suitable for spent fuel reprocessing according to claim 1, characterized in that, In step S2, the ingot is smelted at 1950℃~2050℃ for 10~15 minutes. Then, the ingot is turned over and smelted 3~5 times at the same smelting temperature and time.

5. The method for preparing a high-strength, high-corrosion-resistant, low-cost titanium alloy suitable for spent fuel reprocessing according to claim 1, characterized in that, In step S3, the ingot tapping temperature is set to 20℃~40℃.

6. The method for preparing a high-strength, high-corrosion-resistant, low-cost titanium alloy suitable for spent fuel reprocessing according to claim 1, characterized in that, In step S4, the initial temperature of the β phase region is 1000℃, the cumulative deformation is 40±5%, and the strain rate is 3 s. -1 ~8s -1 .

7. The method for preparing a high-strength, high-corrosion-resistant, low-cost titanium alloy suitable for spent fuel reprocessing according to claim 1, characterized in that, The titanium alloy contains 2.0% to 4.0% V by mass percentage.

8. The method for preparing a high-strength, high-corrosion-resistant, low-cost titanium alloy suitable for spent fuel reprocessing according to claim 7, characterized in that, The titanium alloy contains 1.0% V by mass percentage, and at 100°C, it contains V... 5+ Cr 6+ Ce 4+ In a 6 mol / L HNO3 solution, the polarization resistance R of this titanium alloy p =1932 Ω·cm 2 The corrosion rate is 0.008 mm / year, the yield strength is 798 MPa, and the tensile strength is 815 MPa.

9. A high-strength, high-corrosion-resistant, low-cost titanium alloy suitable for spent fuel reprocessing, characterized in that, The high-strength, high-corrosion-resistant, low-cost titanium alloy suitable for spent fuel reprocessing, as described in any one of claims 1-8, was prepared.

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