Rare earth microalloyed titanium alloy substrate, method of manufacture and bipolar plate

Abstract

The present application relates to the technical field of hydrogen production by water electrolysis of proton exchange membrane, and specifically discloses a rare earth micro-alloyed titanium alloy base material, a preparation method and a bipolar plate. The titanium alloy base material can be used for the bipolar plate, and the composition includes, in terms of mass percentage, Nb 0.01%-1%, Mo 0.01%-1.5%, Y 0.01%-0.5%, La 0.01%-0.5%, Ce 0.01%-0.5%, and the balance being titanium. The preparation method includes: according to the component design, ingredients are prepared and smelted to obtain ingots, the slab is forged and processed, hot rolling and cold rolling are processed to obtain titanium alloy strip; the titanium alloy strip is subjected to two-stage grading aging treatment to obtain the titanium alloy base material. Through titanium alloy micro-alloying, the corrosion resistance, strength plasticity and hydrogen embrittlement sensitivity of the titanium alloy are improved. The multiple vacuum consumable smelting method is adopted to ensure the uniformity of the titanium alloy ingot composition. Through smelting, forging, hot rolling, cold rolling and grading aging, the PEM electrolysis cell titanium alloy base material with a thickness of 0.1mm-2mm is finally obtained.

Description

Technical Field

[0001] This invention relates to the field of proton exchange membrane (PEM) electrolysis for hydrogen production, and particularly to a rare earth element microalloyed titanium alloy substrate, its preparation method, and a bipolar plate. Background Technology

[0002] With the rapid development of the global green hydrogen industry, PEM (Polymer Electrolysis) water electrolysis technology has become a core technology for large-scale hydrogen production due to its advantages such as high efficiency, rapid response, and high current density. As a core component of the PEM electrolyzer, the bipolar plate, due to the use of perfluorosulfonic acid (PFSA) membranes, results in a predominantly acidic working environment. Combined with the high voltage and oxygen release on the anode side, this creates a harsh oxidizing environment. Therefore, the bipolar plate, gas diffusion layer, and other structures of the PEM electrolyzer need to possess corrosion resistance. While traditional titanium alloys (such as TA1 and TA2) have excellent corrosion resistance, they are prone to forming a non-conductive passivation film under high voltage and high potential, leading to a sharp increase in contact resistance. Furthermore, their high hydrogen diffusion coefficient makes them susceptible to hydrogen embrittlement failure.

[0003] In addition, existing titanium alloy bipolar plate substrates generally have the following problems:

[0004] 1) Insufficient corrosion resistance: The passivation film has poor stability at high potentials, resulting in high local pitting current density;

[0005] 2) The contradiction between strength and plasticity: the tensile strength is generally lower than 400 MPa, which is difficult to meet the requirements of high-pressure working conditions;

[0006] 3) High process cost: Traditional cladding rolling process is complex, and the cost of precious metal coating (such as Pt, Au) accounts for more than 40%.

[0007] Therefore, there is an urgent need to develop titanium alloy bipolar plate substrates that combine high corrosion resistance, high strength, and low hydrogen embrittlement sensitivity by optimizing the intrinsic properties of the substrate.

[0008] Therefore, existing technologies still need improvement. Summary of the Invention

[0009] To address the aforementioned technical problems, this invention provides a rare-earth element microalloyed titanium alloy substrate, its preparation method, and a bipolar plate, thereby resolving the technical issues of insufficient corrosion resistance, low strength, or high cost of bipolar plates made from titanium alloy substrates in the prior art.

[0010] To address the aforementioned technical problems, in one aspect, some embodiments of the present invention disclose a rare earth element microalloyed titanium alloy substrate, the composition of which, by mass percentage, includes:

[0011] Nb 0.01%~1%,

[0012] Mo 0.01%~1.5%,

[0013] Y 0.01%~0.5%,

[0014] La 0.01%~0.5%,

[0015] Ce 0.01%~0.5%,

[0016] The balance consists of titanium and unavoidable impurities.

[0017] In some embodiments, the rare earth element microalloyed titanium alloy substrate has a thickness of 0.1~2 mm; tensile strength ≥ 400 MPa; yield strength ≥ 300 MPa; elongation ≥ 35%; and corrosion current ≤ 5.0 × 10⁻⁶. -7 A / cm²; contact resistance ≤4.0mΩ·cm²; hydrogen embrittlement sensitivity is 450h without cracking.

[0018] On the other hand, some embodiments of the present invention also disclose a method for preparing the aforementioned rare-earth element microalloyed titanium alloy substrate, which includes:

[0019] Step 1: Prepare the ingredients according to the composition design and smelt them to obtain an ingot;

[0020] Step 2: Forge the ingot into a slab;

[0021] Step 3: The slab is hot-rolled and cold-rolled to obtain titanium alloy strip;

[0022] Step 4: Perform a two-stage graded aging treatment on the titanium alloy strip to obtain a titanium alloy substrate;

[0023] The thickness of the titanium alloy strip is 0.1 to 2 mm.

[0024] In some embodiments, step five, the two-stage graded timeliness processing includes:

[0025] First-level aging: Hold at a temperature 150-250°C lower than the alloy's phase transformation temperature for 3-4 hours;

[0026] Secondary aging: Hold at a temperature 300-400°C lower than the alloy phase transformation temperature for 5-6 hours.

[0027] In some embodiments, in step one, the melting is carried out in a vacuum arc remelting furnace more than 3 times. During the melting process, the vacuum degree in the vacuum arc remelting furnace is ≤3.0Pa, the arc stabilizing current is 3~10A, the melting voltage is 35~42V, the melting current is 5~12kA, and the melting current and melting voltage are increased successively to obtain ingots with a diameter of Φ200~300mm.

[0028] In some embodiments, step two, the forging process includes: measuring the phase transformation temperature T of the Ti-Nb-Mo-Y-La-Ce alloy. β Then it undergoes four rounds of forging.

[0029] The heating temperature for the first forging is T. β +120~T β +150℃, the heating temperature for the second forging is T. β +80~T β +100℃, the heating temperature for triple-fire forging is T β ±10℃, the heating temperature for four-fire forging is T β ±10℃.

[0030] In some embodiments, in step two, during the forging process, the holding time for the first forging is (0.6~0.8) × ingot diameter min; the holding time for the N-forging is (0.6~0.8) × the minimum value of the length, width, and height of the slab before this forging, min, where N = 2, 3, or 4; and the unit of the ingot diameter or the length, width, and height of the slab is mm.

[0031] In some embodiments, step three, which involves hot rolling and cold rolling the slab, includes:

[0032] The slab is subjected to multiple hot rolling processes, with the heating temperature being 20-40°C lower than the alloy phase transformation temperature, and the holding time being (1.5-1.8) × plate thickness in min, to obtain hot-rolled plates with a thickness of 3-4 mm, wherein the unit of plate thickness is mm.

[0033] In some embodiments, step three, which involves hot rolling and cold rolling the slab, further includes: annealing and surface finishing the hot-rolled sheet at a temperature 150–250°C lower than the phase transformation temperature, followed by cold rolling to produce a cold-rolled strip with a thickness of 0.1–2 mm, and then performing online stress-relief annealing at an annealing temperature 150–250°C lower than the phase transformation temperature to obtain a titanium alloy strip.

[0034] Thirdly, embodiments of the present invention also disclose a bipolar plate comprising the aforementioned rare earth element microalloyed titanium alloy substrate.

[0035] By adopting the above technical solution, the present invention has at least the following beneficial effects:

[0036] This invention provides a rare earth element microalloyed titanium alloy substrate and its preparation method. Targeting titanium alloy substrates for bipolar plates, the invention improves the corrosion resistance, strength, plasticity, and resistance to hydrogen embrittlement of the titanium alloy through microalloying. A multiple vacuum consumable melting method is employed to ensure the uniformity of the titanium alloy ingot composition. Through processes such as melting, forging, hot rolling, cold rolling, and graded aging, a PEM electrolytic cell titanium alloy substrate with a thickness of 0.1 mm to 2 mm is finally obtained. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1 This is a process flow diagram of a method for preparing a rare earth element microalloyed titanium alloy substrate disclosed in some embodiments of the present invention. Detailed Implementation

[0039] The embodiments of this disclosure will be further described in detail below with reference to the accompanying drawings and examples. The detailed description of the embodiments and the accompanying drawings are used to illustrate the principles of this disclosure by way of example, but should not be used to limit the scope of this disclosure. This disclosure can be implemented in many different forms and is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

[0040] These embodiments are provided to make the disclosure thorough and complete, and to fully express the scope of the disclosure to those skilled in the art. It should be noted that, unless otherwise specifically stated, the relative arrangement of components and steps, material composition, numerical expressions, and values ​​set forth in these embodiments should be interpreted as exemplary only and not as limiting.

[0041] It should be noted that, in the description of this disclosure, unless otherwise stated, "a plurality of" means two or more; the terms "upper," "lower," "left," "right," "inner," and "outer," etc., indicating orientation or positional relationship, are only for the convenience of describing this disclosure and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this disclosure. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0042] Furthermore, as used in this disclosure, words such as "including" or "comprising" mean that the element preceding the word covers the element listed after the word, and do not exclude the possibility that other elements may also be covered.

[0043] All terms used in this disclosure have the same meaning as understood by one of ordinary skill in the art to which this disclosure pertains, unless otherwise specifically defined. It should also be understood that terms defined in general dictionaries should be interpreted as having meanings consistent with their meanings in the context of the relevant art, and not as idealized or highly formalized, unless expressly defined herein.

[0044] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, they should be considered part of the specification.

[0045] This invention discloses a rare-earth element microalloyed titanium alloy substrate and its preparation method. Through synergistic optimization of composition design, melting process, cold and hot deformation process, and heat treatment process, significant improvements in multiple properties are achieved. Regarding corrosion resistance, rare-earth elements (Y, La, Ce) can refine grains, purify grain boundaries, and form nano-oxides (such as Y₂O₃ and La₂TiO₅), increasing the density of the passivation film and reducing corrosion current. In terms of strength and plasticity synergy, a tensile strength ≥400 MPa and an elongation ≥35% are achieved. Regarding hydrogen embrittlement resistance, its resistance to hydrogen embrittlement sensitivity is improved.

[0046] The rare earth element microalloyed titanium alloy substrate, by mass percentage, comprises: Nb 0.01%~1%, Mo 0.01%~1.5%, Y 0.01%~0.5%, La 0.01%~0.5%, Ce 0.01%~0.5%, with the balance being titanium and unavoidable impurities. Titanium alloy substrates with a thickness of 0.1~2 mm can be produced; the mechanical properties and other parameters are as follows: tensile strength ≥400 MPa; yield strength ≥300 MPa; elongation ≥35%; corrosion current ≤5.0×10⁻⁶. -7 A / cm²; contact resistance ≤4.0 mΩ·cm²; hydrogen embrittlement sensitivity is 450h without cracking.

[0047] like Figure 1 As shown, the specific process scheme for its preparation method is as follows:

[0048] (1) Composition design: Trace amounts of Nb, Mo, Y, La, and Ce alloying elements are added to improve the strength and corrosion resistance of the titanium substrate. The element addition amounts (mass percentage) are: 0.01%≤[Nb]%≤1%, 0.01%≤[Mo]%≤1.5%, 0.01%≤[Y]%≤0.5%, 0.01%≤[La]%≤0.5%, 0.01%≤[Ce]%≤0.5%, with the balance being titanium and unavoidable impurities. To address the high requirements for conductivity and corrosion resistance of the PEM electrolytic cell bipolar plate, a micro-alloying design using Nb, Mo, Y, La, and Ce is adopted, which improves the material's corrosion resistance, strength, plasticity, and hydrogen embrittlement sensitivity.

[0049] (2) Vacuum self-consuming furnace smelting: 0A grade sponge titanium, Ti-Mo master alloy, high-purity niobium powder (Nb 99.9%), and high-purity rare earth metals (Y 99.95%, La 99.96%, Ce 99.95%) are used as raw materials. The raw materials are batched according to the mass percentage in step (1), and vacuum self-consuming furnace smelting is carried out more than 3 times. During the smelting process, the vacuum degree in the vacuum self-consuming furnace is ≤3.0Pa, the arc current is 3~10A, the smelting voltage is 35~42V, and the smelting current is 5~12kA to obtain ingots with a specification of Φ200~300mm. The ingots are peeled and flattened to remove surface oxides and impurities. After the surface is polished, hot working is carried out. 0A grade sponge titanium is selected with impurity element content of [C]%≤0.01%, [N]%≤0.01%, and [O]%≤0.01%. The impurity content of the titanium alloy ingot is ≤0.04%, [H]%≤0.001%, and [Fe]%≤0.02%. A Ti-Mo master alloy is selected, with impurity element content of [Fe]%≤0.05%, [N]%≤0.01%, and [O]%≤0.04%. High-purity niobium powder is selected, with impurity element content of [Fe]%≤0.05%, [N]%≤0.01%, and [O]%≤0.04%. High-purity rare earth metals (Y, La, Ce) are selected, with impurity element content of [Fe]%≤0.05%, [N]%≤0.01%, and [O]%≤0.04%. By employing a vacuum arc remelting method, which has excellent non-metallic impurity removal capabilities, the purity and compositional uniformity of the titanium alloy ingot are ensured. More than three vacuum remelting processes guarantee the uniform distribution of alloying elements and rare earth elements in the titanium alloy ingot.

[0050] (3) Slab forging: The phase transformation point T of the Ti-Nb-Mo-Y-La-Ce alloy was determined by differential thermal analysis. β The ingot obtained in step (2) is subjected to four-stage XYZ reversal forging, with the first forging heating temperature T. β + (120~150)℃, holding time t1=(0.6~0.8)D1 (D1 represents the ingot diameter), forging into a slab with a thickness of 200~250mm; the second forging temperature is T β+80~100℃, holding time is t2=(0.6~0.8)D2 (D2 is the minimum dimension of the length, width, height and depth of the square billet, i.e., slab, forged in one heat), forging to a slab with a thickness of 200~250mm; three-heat forging temperature is T β ±10℃, holding time is t3=(0.6~0.8)D3 (D3 is the minimum dimension of length, width, height and depth of the square billet forged in the second heat), forging into a slab with a thickness of 200~250mm; the fourth heat forging temperature is T β The temperature is ±10℃, and the holding time is t4=(0.6~0.8)D4 (D4 is the minimum dimension of the length, width, height and depth of the three-fire forging square billet). The billet is forged into a slab with a thickness of 200~250mm. After the four-fire forging is completed, the plate is rolled after milling.

[0051] (4) Hot rolling and cold rolling: The slab obtained in step (3) is subjected to multiple hot rolling processes at a heating temperature of T. β - (20~40)℃, heat preservation time is t=(1.5~1.8)d (d is the thickness of plate or slab), to obtain hot-rolled plates with a thickness of 3~4mm, and then perform T on the hot-rolled plates. β After annealing at -150~250℃ and surface finishing, the strip undergoes cold rolling. During cold working, when the strip deformation exceeds 60%, online stress-relieving annealing is performed at a temperature of T. β -(150~250)℃, finally rolled to obtain titanium alloy strip with a width of 450~550mm and a thickness of 0.1mm~2mm; among them, when the strip thickness is less than 1mm, a 20-roll narrow titanium strip mill can be used to ensure the width and thickness accuracy of the base material and industrial production.

[0052] (5) Graded aging: The titanium alloy substrate from step (4) is placed in a high vacuum annealing furnace (vacuum degree ≤ 5×10). - 3 Pa), subject to a two-stage expiratory period. ① First-stage expiratory period: T β - Holding at (150~250)℃ for 3~4h, during this aging process, nano-sized Nb-Ti intermetallic compounds precipitate in the β-phase matrix, which helps to improve the strength of the alloy; ② Secondary aging: T β Holding at (300~400)℃ for 5~6 hours allows rare earth elements Y, La, and Ce to segregate at grain boundaries, forming Y2O3, La2TiO5, and CeO2, further purifying the grain boundaries and improving the alloy's corrosion resistance and resistance to hydrogen embrittlement. Annealing the titanium alloy substrate in a high-vacuum vacuum annealing furnace avoids oxide contamination on the substrate surface, ensuring surface cleanliness. Simultaneously, staged aging further enhances the strength, corrosion resistance, and resistance to hydrogen embrittlement of the titanium alloy substrate.

[0053] Example 1

[0054] (1) Composition design: The composition is designed by mass percentage as follows: Nb 0.3%, Mo 0.8%, Y 0.15%, La 0.1%, Ce 0.1%, with the balance being titanium and unavoidable impurities.

[0055] (2) Vacuum self-consuming furnace smelting: 0A grade sponge titanium, Ti-Mo master alloy, high-purity niobium powder (Nb 99.9%), and high-purity rare earth metals (Y 99.95%, La 99.96%, Ce 99.95%) are used as raw materials. The raw materials are prepared according to the mass percentage in step (1) and vacuum self-consuming furnace smelting is carried out 5 times. During the smelting process, the vacuum degree in the vacuum self-consuming furnace is ≤3.0Pa. The arc stabilization current of the 5 vacuum smelting is 6A, 8A, 9A, 10A and 11A respectively. The smelting voltage of the 5 vacuum smelting stages is 28V, 30V, 32V, 34V and 36V respectively. The smelting current of the 5 vacuum smelting is 5kA, 7kA, 8kA, 10kA and 11kA respectively. After each smelting, the ingot is flipped 180° to eliminate compositional segregation. Finally, a Φ250mm ingot is obtained, which is then peeled and flattened to remove surface oxides and impurities. After surface finishing, it undergoes heat treatment.

[0056] (3) Slab forging: The alloy phase transformation point T was determined by differential thermal analysis. β =888℃, and perform four-stage XYZ reversing forging: the first forging temperature is 1008℃, and the holding time is 200min; the second forging temperature is 968℃, and the holding time is 160min; the third forging temperature is 878℃, and the holding time is 160min; the fourth forging temperature is 878℃, and the holding time is 160min. The forging is to produce a 200mm thick slab, which is then milled and rolled into sheet metal.

[0057] (4) Hot rolling and cold rolling: The slab is heated to 848℃ and held for t=360min. It is rolled into a 3.5mm hot-rolled plate after four hot rolling cycles. The final rolling temperature is 735℃. After the hot-rolled plate is annealed at 638℃ and the surface is polished, it is cold-rolled. The cold rolling is divided into three rolling passes to produce a 0.5mm thick cold-rolled strip. The online stress-relief annealing treatment is carried out at a temperature of 638℃ and the holding time is 30min. Finally, a titanium alloy strip with a width of 450mm and a thickness of 0.5mm is obtained.

[0058] (5) Graded aging: The titanium alloy substrate from step (4) is placed in a high vacuum annealing furnace (vacuum degree ≤ 5×10). - 3The titanium alloy underwent a two-stage aging process. ① First-stage aging: holding at 638℃ for 4 hours. During this aging process, nano-sized Nb-Ti intermetallic compounds precipitate in the β-phase matrix, which helps to improve the strength of the alloy. ② Second-stage aging: holding at 488℃ for 6 hours. Rare earth elements Y, La, and Ce segregate at the grain boundaries to form Y₂O₃, La₂TiO₅, and CeO₂, further purifying the grain boundaries and improving the alloy's corrosion resistance and resistance to hydrogen embrittlement. The performance parameters of the obtained titanium alloy substrate are shown in Table 1.

[0059] Example 2

[0060] (1) Composition design: The composition is designed by mass percentage as follows: Nb 0.5%, Mo 1.2%, Y 0.25%, La 0.2%, Ce 0.2%, with the balance being titanium and unavoidable impurities.

[0061] (2) Vacuum self-consuming furnace smelting: 0A grade sponge titanium, Ti-Mo master alloy, high-purity niobium powder (Nb 99.9%), and high-purity rare earth metals (Y 99.95%, La 99.96%, Ce 99.95%) are used as raw materials. The raw materials are prepared according to the mass percentage in step (1) and vacuum self-consuming furnace smelting is carried out 5 times. During the smelting process, the vacuum degree in the vacuum self-consuming furnace is ≤3.0Pa. The arc stabilization current of the 5 vacuum smelting is 6A, 8A, 9A, 10A and 11A respectively. The smelting voltage of the 5 vacuum smelting stages is 28V, 30V, 32V, 34V and 36V respectively. The smelting current of the 5 vacuum smelting is 5kA, 7kA, 8kA, 10kA and 11kA respectively. After each smelting, the ingot is flipped 180° to eliminate compositional segregation. Finally, a Φ250mm ingot is obtained, which is then peeled and flattened to remove surface oxides and impurities. After surface finishing, it undergoes heat treatment.

[0062] (3) Slab forging: The alloy phase transformation point T was determined by differential thermal analysis. β =884℃, and perform four-stage XYZ reversing forging: the first forging temperature is 1034℃, and the holding time is 150min; the second forging temperature is 984℃, and the holding time is 150min; the third forging temperature is 894℃, and the holding time is 120min; the fourth forging temperature is 894℃, and the holding time is 150min. The forging is to produce a 250mm thick slab, which is then milled and rolled into sheet metal.

[0063] (4) Hot rolling and cold rolling: The slab is heated to 864℃ and held for 375 minutes. It is rolled into a 3.5mm hot-rolled plate in four passes. The final rolling temperature is 768℃. After the hot-rolled plate is annealed at 734℃ and the surface is polished, it is cold-rolled. The cold rolling is divided into three passes to produce a 0.5mm thick cold-rolled strip. The online stress-relieving annealing treatment is carried out at a temperature of 734℃ and the holding time is 30 minutes. Finally, a titanium alloy strip with a width of 550mm and a thickness of 0.5mm is obtained.

[0064] (5) Graded aging: The titanium alloy substrate from step (4) is placed in a high vacuum annealing furnace (vacuum degree ≤ 5×10). - 3 The titanium alloy underwent a two-stage aging process. ① First-stage aging: holding at 734℃ for 3 hours. During this aging process, nano-sized Nb-Ti intermetallic compounds precipitate in the β-phase matrix, which helps to improve the strength of the alloy. ② Second-stage aging: holding at 584℃ for 5 hours. Rare earth elements Y, La, and Ce segregate at the grain boundaries to form Y₂O₃, La₂TiO₅, and CeO₂, further purifying the grain boundaries and improving the alloy's corrosion resistance and resistance to hydrogen embrittlement. The performance parameters of the obtained titanium alloy substrate are shown in Table 1.

[0065] Example 3

[0066] (1) Composition design: The composition is designed by mass percentage as follows: Nb 0.1%, Mo 0.5%, Y 0.08%, La 0.05%, Ce 0.05%, with the balance being titanium and unavoidable impurities.

[0067] (2) Vacuum self-consuming furnace smelting: 0A grade sponge titanium, Ti-Mo master alloy, high-purity niobium powder (Nb 99.9%), and high-purity rare earth metals (Y 99.95%, La 99.96%, Ce 99.95%) are used as raw materials. The raw materials are prepared according to the mass percentage in step (1) and vacuum self-consuming furnace smelting is carried out 5 times. During the smelting process, the vacuum degree in the vacuum self-consuming furnace is ≤3.0Pa. The arc stabilization current of the 5 vacuum smelting is 6A, 8A, 9A, 10A and 11A respectively. The smelting voltage of the 5 vacuum smelting stages is 28V, 30V, 32V, 34V and 36V respectively. The smelting current of the 5 vacuum smelting is 5kA, 7kA, 8kA, 10kA and 11kA respectively. After each smelting, the ingot is flipped 180° to eliminate compositional segregation. Finally, a Φ250mm ingot is obtained, which is then peeled and flattened to remove surface oxides and impurities. After surface finishing, it undergoes heat treatment.

[0068] (3) Slab forging: The alloy phase transformation point T was determined by differential thermal analysis. β=892℃, and perform four-stage XYZ reversing forging: the first forging temperature is 1022℃, and the holding time is 150min; the second forging temperature is 982℃, and the holding time is 120min; the third forging temperature is 892℃, and the holding time is 120min; the fourth forging temperature is 892℃, and the holding time is 120min. The forging is to produce a 200mm thick slab, which is then milled and rolled into sheet metal.

[0069] (4) Hot rolling and cold rolling: The slab is heated to 862℃ and held for 300 min. It is rolled into a 3.5 mm hot-rolled plate in four passes. The final rolling temperature is 750℃. After the hot-rolled plate is annealed at 692℃ and the surface is polished, it is cold-rolled. The cold rolling is divided into three passes to roll into a 0.5 mm thick cold-rolled strip. The online stress relief annealing treatment is carried out at a temperature of 692℃ and the holding time is 30 min. Finally, a titanium alloy strip with a width of 500 mm and a thickness of 0.5 mm is obtained.

[0070] (5) Staged aging: The titanium alloy substrate from step (4) was placed in a high-vacuum annealing furnace (vacuum degree ≤ 5×10-3 Pa) for two-stage aging. ① First-stage aging: 692℃ for 3h. During this aging process, nano-sized Nb-Ti intermetallic compounds precipitate in the β-phase matrix, which helps to improve the strength of the alloy. ② Second-stage aging: 542℃ for 5h. Rare earth elements Y, La, and Ce segregate at the grain boundaries to form Y2O3, La2TiO5, and CeO2, further purifying the grain boundaries and improving the corrosion resistance and hydrogen embrittlement sensitivity of the alloy. The various performance parameters of the obtained titanium alloy substrate are shown in Table 1.

[0071] Example 4

[0072] (1) Composition design: The composition is designed by mass percentage as follows: Nb 0.01%, Mo 1.5%, Y 0.5%, La 0.01%, Ce 0.02%, with the balance being titanium and unavoidable impurities.

[0073] (2) Vacuum self-consuming furnace smelting: 0A grade sponge titanium, Ti-Mo master alloy, high-purity niobium powder (Nb 99.9%), and high-purity rare earth metals (Y 99.95%, La 99.96%, Ce 99.95%) are used as raw materials. The raw materials are prepared according to the mass percentage in step (1) and vacuum self-consuming furnace smelting is carried out 5 times. During the smelting process, the vacuum degree in the vacuum self-consuming furnace is ≤3.0Pa. The arc stabilization current of the 5 vacuum smelting is 6A, 8A, 9A, 10A and 11A respectively. The smelting voltage of the 5 vacuum smelting stages is 28V, 30V, 32V, 34V and 36V respectively. The smelting current of the 5 vacuum smelting is 5kA, 7kA, 8kA, 10kA and 11kA respectively. After each smelting, the ingot is flipped 180° to eliminate compositional segregation. Finally, a Φ250mm ingot is obtained, which is then peeled and flattened to remove surface oxides and impurities. After surface finishing, it undergoes heat treatment.

[0074] (3) Slab forging: The alloy phase transformation point T was determined by differential thermal analysis. β =884℃, and perform four-stage XYZ reversing forging: the first forging temperature is 1014℃, and the holding time is 150min; the second forging temperature is 974℃, and the holding time is 120min; the third forging temperature is 884℃, and the holding time is 120min; the fourth forging temperature is 884℃, and the holding time is 120min. The forging is to produce a 200mm thick slab, which is then milled and rolled into sheet metal.

[0075] (4) Hot rolling and cold rolling: The slab is heated to 854℃ and held for 300 min. It is rolled into a 3.5 mm hot-rolled plate in four passes. The final rolling temperature is 750℃. After the hot-rolled plate is annealed at 684℃ and the surface is polished, it is cold-rolled. The cold rolling is divided into 5 passes to roll into a 0.1 mm thick cold-rolled strip. The online stress relief annealing treatment is carried out at 684℃ and the holding time is 30 min. Finally, a titanium alloy foil with a width of 500 mm and a thickness of 0.1 mm is obtained.

[0076] (5) Graded aging: The titanium alloy substrate from step (4) is placed in a high vacuum annealing furnace (vacuum degree ≤ 5×10). - 3 The titanium alloy underwent a two-stage aging process. ① First-stage aging: holding at 684℃ for 3 hours. During this aging process, nano-sized Nb-Ti intermetallic compounds precipitate in the β-phase matrix, which helps to improve the strength of the alloy. ② Second-stage aging: holding at 534℃ for 5 hours. Rare earth elements Y, La, and Ce segregate at the grain boundaries to form Y₂O₃, La₂TiO₅, and CeO₂, further purifying the grain boundaries and improving the alloy's corrosion resistance and resistance to hydrogen embrittlement. The performance parameters of the obtained titanium alloy substrate are shown in Table 1.

[0077] Example 5

[0078] (1) Composition design: The composition is designed by mass percentage as follows: Nb 1%, Mo 0.01%, Y 0.01%, La 0.5%, Ce 0.5%, with the balance being titanium and unavoidable impurities.

[0079] (2) Vacuum self-consuming furnace smelting: 0A grade sponge titanium, Ti-Mo master alloy, high-purity niobium powder (Nb 99.9%), and high-purity rare earth metals (Y 99.95%, La 99.96%, Ce 99.95%) are used as raw materials. The raw materials are prepared according to the mass percentage in step (1) and vacuum self-consuming furnace smelting is carried out 5 times. During the smelting process, the vacuum degree in the vacuum self-consuming furnace is ≤3.0Pa. The arc stabilization current of the 5 vacuum smelting is 6A, 8A, 9A, 10A and 11A respectively. The smelting voltage of the 5 vacuum smelting stages is 28V, 30V, 32V, 34V and 36V respectively. The smelting current of the 5 vacuum smelting is 5kA, 7kA, 8kA, 10kA and 11kA respectively. After each smelting, the ingot is flipped 180° to eliminate compositional segregation. Finally, a Φ250mm ingot is obtained, which is then peeled and flattened to remove surface oxides and impurities. After surface finishing, it undergoes heat treatment.

[0080] (3) Slab forging: The alloy phase transformation point T was determined by differential thermal analysis. β =891℃, and perform four-stage XYZ reversing forging: the first forging temperature is 1021℃, and the holding time is 150min; the second forging temperature is 981℃, and the holding time is 120min; the third forging temperature is 891℃, and the holding time is 120min; the fourth forging temperature is 891℃, and the holding time is 120min. The forging is to produce a 200mm thick slab, which is then milled and rolled into sheet metal.

[0081] (4) Hot rolling and cold rolling: The slab is heated to 861℃ and held for 300 min. It is rolled into a 3.5 mm hot-rolled plate in four passes. The final rolling temperature is 750℃. After the hot-rolled plate is annealed at 691℃ and the surface is polished, it is cold-rolled. The cold rolling is divided into one rolling pass to produce a 2 mm thick cold-rolled strip. The online stress-relieving annealing treatment is carried out at an annealing temperature of 691℃ and the holding time is 30 min. Finally, a titanium alloy strip with a width of 500 mm and a thickness of 2 mm is obtained.

[0082] (5) Graded aging: The titanium alloy substrate from step (4) is placed in a high vacuum annealing furnace (vacuum degree ≤ 5×10). - 3The titanium alloy underwent a two-stage aging process. ① First-stage aging: holding at 691℃ for 3 hours. During this aging process, nano-sized Nb-Ti intermetallic compounds precipitate in the β-phase matrix, which helps to improve the strength of the alloy. ② Second-stage aging: holding at 541℃ for 5 hours. Rare earth elements Y, La, and Ce segregate at the grain boundaries to form Y₂O₃, La₂TiO₅, and CeO₂, further purifying the grain boundaries and improving the alloy's corrosion resistance and resistance to hydrogen embrittlement. The performance parameters of the obtained titanium alloy substrate are shown in Table 1.

[0083] Comparative Example 1

[0084] (1) Composition design: The composition is designed by mass percentage as follows: Nb 0.3%, Mo 0.8%, with the balance being titanium and unavoidable impurities.

[0085] (2) Vacuum self-consuming furnace smelting: 0A grade sponge titanium, Ti-Mo master alloy, high-purity niobium powder (Nb 99.9%), and high-purity rare earth metals (Y 99.95%, La 99.96%, Ce 99.95%) are used as raw materials. The raw materials are prepared according to the mass percentage in step (1) and vacuum self-consuming furnace smelting is carried out 5 times. During the smelting process, the vacuum degree in the vacuum self-consuming furnace is ≤3.0Pa. The arc stabilization current of the 5 vacuum smelting is 6A, 8A, 9A, 10A and 11A respectively. The smelting voltage of the 5 vacuum smelting stages is 28V, 30V, 32V, 34V and 36V respectively. The smelting current of the 5 vacuum smelting is 5kA, 7kA, 8kA, 10kA and 11kA respectively. After each smelting, the ingot is flipped 180° to eliminate compositional segregation. Finally, a Φ250mm ingot is obtained, which is then peeled and flattened to remove surface oxides and impurities. After surface finishing, it undergoes heat treatment.

[0086] (3) Slab forging: The alloy phase transformation point Tβ was determined to be 888℃ using differential thermal analysis. Four-stage XYZ reversal forging was performed: the first forging temperature was 1018℃ and the holding time was 150min; the second forging temperature was 978℃ and the holding time was 120min; the third forging temperature was 888℃ and the holding time was 120min; and the fourth forging temperature was 888℃ and the holding time was 120min. The forged slab was 200mm thick and then rolled into sheet metal after milling.

[0087] (4) Hot rolling and cold rolling: The slab is heated to 858℃ and held for 300 min. It is rolled into a 3.5 mm hot-rolled plate in four passes. The final rolling temperature is 750℃. After the hot-rolled plate is annealed at 688℃ and the surface is polished, it is cold-rolled. The cold rolling is divided into three passes to roll into a 0.5 mm thick cold-rolled strip. The online stress relief annealing treatment is carried out at an annealing temperature of 688℃ and the holding time is 30 min. Finally, a titanium alloy strip with a width of 500 mm and a thickness of 0.5 mm is obtained.

[0088] (6) Staged aging: The titanium alloy substrate from step (5) was placed in a high-vacuum annealing furnace (vacuum degree ≤ 5×10-3 Pa) for two-stage aging. ① First-stage aging: 688℃ for 3 hours; ② Second-stage aging: 538℃ for 5 hours. The various performance parameters of the obtained titanium alloy substrate are shown in Table 1.

[0089] Table 1

[0090]

[0091] Specifically, the obtained titanium alloy substrates were subjected to tensile property, corrosion current, contact resistance, and hydrogen embrittlement sensitivity tests. The corrosion current and contact resistance test methods were based on the national standard GB / T20042.6-2011; the mechanical property test methods were based on the standard GB / T228.1-2010. As can be seen from Table 1, the titanium alloy substrates of Examples 1-5 of this invention have higher room temperature tensile strength and yield strength, lower corrosion current and contact resistance, and lower hydrogen embrittlement sensitivity. In contrast, the titanium alloy substrate of Comparative Example 1, which does not contain rare earth elements, has lower tensile strength and yield strength, higher corrosion current and contact resistance, poorer corrosion resistance, and severe cracks appear within 200 hours, indicating poor hydrogen embrittlement sensitivity.

[0092] The embodiments of this disclosure have now been described in detail. To avoid obscuring the concept of this disclosure, some details known in the art have not been described. Those skilled in the art can fully understand how to implement the technical solutions disclosed herein based on the above description.

[0093] While specific embodiments of this disclosure have been described in detail by way of examples, those skilled in the art should understand that the examples are for illustrative purposes only and not intended to limit the scope of this disclosure. Those skilled in the art should understand that modifications can be made to the above embodiments or equivalent substitutions can be made to some technical features without departing from the scope and spirit of this disclosure. In particular, as long as there is no structural conflict, the technical features mentioned in the various embodiments can be combined in any manner.

Claims

1. A method of producing a rare earth microalloyed titanium alloy substrate, characterized by, include: Step 1: Prepare the ingredients according to the composition design and smelt them to obtain an ingot; Step 2: Forge the ingot into a slab; Step 3: The slab is hot-rolled and cold-rolled to obtain titanium alloy strip; Step 4: Perform a two-stage graded aging treatment on the titanium alloy strip to obtain a titanium alloy substrate; The thickness of the titanium alloy strip is 0.1–2 mm; The rare earth element microalloyed titanium alloy substrate comprises, by weight percentage, the following components: Nb 0.01%~1%, Mo 0.01%~1.5%, Y0.01%~0.5%， La 0.01%~0.5%, Ce 0.01%~0.5%, The balance consists of titanium and unavoidable impurities; Tensile strength ≥ 453 MPa; Yield strength ≥ 300 MPa; Elongation ≥ 35%; Corrosion current ≤ 8.0 × 10⁻⁶ -8 A / cm²; Contact resistance ≤4.0mΩ·cm²; Hydrogen embrittlement sensitivity is 500h without cracking; Step four, the two-stage graded timeliness processing includes: First-level aging: Hold at a temperature 150–250°C lower than the alloy's phase transformation temperature for 3–4 hours; Secondary aging: Hold at a temperature 300-400°C lower than the alloy phase transformation temperature for 5-6 hours.

2. The preparation method according to claim 1, characterized in that, In step one, the smelting is carried out in a vacuum arc remelting furnace more than 3 times. During the smelting process, the vacuum degree in the vacuum arc remelting furnace is ≤3.0Pa, the arc stabilizing current is 3~10A, the smelting voltage is 35~42V, the smelting current is 5~12kA, and the smelting current and smelting voltage are increased one by one to obtain ingots with a diameter of Φ200~300mm.

3. The preparation method according to claim 1, characterized in that, In the second step, the forging process includes: measuring phase transition point temperature T of the Ti-Nb-Mo-Y-La-Ce alloy β and then performing four times of forging; wherein the heating temperature for the first fire forging is T β ± 10°C β ± 10°C β ± 10°C β ± 10°C β ± 10°C β ± 10°C During the forging process, the holding time for the first forging is (0.6~0.8) × ingot diameter min; the holding time for the N-forging is (0.6~0.8) × the minimum value of the length, width and height of the slab before this forging, min, where N = 2, 3 or 4; and the unit of the ingot diameter or the length, width and height of the slab is mm.

4. The production method according to claim 1, characterized by, Step three, which involves hot rolling and cold rolling the slab, includes: The slab is subjected to multiple hot rolling processes, with the heating temperature being 20-40°C lower than the alloy phase transformation temperature, and the holding time being (1.5-1.8) × plate thickness in min, to obtain hot-rolled plates with a thickness of 3-4 mm, wherein the unit of plate thickness is mm.

5. The preparation method according to claim 4, characterized in that, Step three, the hot rolling and cold rolling of the slab further includes: annealing and surface finishing the hot-rolled sheet at a temperature 150-250°C lower than the phase transformation temperature, followed by cold rolling to produce cold-rolled strip with a thickness of 0.1-2 mm, and then performing online stress-relief annealing at an annealing temperature 150-250°C lower than the phase transformation temperature to obtain titanium alloy strip.

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