Corrosion-resistant titanium alloy bipolar plate and preparation method thereof

Abstract

The invention belongs to the field of titanium alloys and fuel cells, and discloses a corrosion-resistant titanium alloy bipolar plate which comprises niobium, zirconium and tantalum elements, the corrosion-resistant titanium alloy bipolar plate comprises the following components in percentage by mass: 14-18% of niobium, 8-12% of zirconium, 3-7% of tantalum and the balance of titanium and inevitable impurities, and the titanium alloy bipolar plate is good in corrosion resistance in a highly corrosive environment, so that a fuel cell can stably operate under severe conditions, and the service life of the fuel cell is prolonged. In addition, the invention further discloses a preparation method of the corrosion-resistant titanium alloy bipolar plate, alloy raw materials are subjected to hot rolling, annealing, cold rolling and heat treatment after being cast, and therefore a titanium alloy thin plate which is uniform in structure, smooth in surface, free of defects and 1 mm in thickness can be rolled.

Description

Technical Field

[0001] The present invention belongs to the field of titanium alloys and fuel cells, and relates to a bipolar plate in a fuel cell, and in particular to a corrosion-resistant titanium alloy bipolar plate and a preparation method thereof. Background Art

[0002] Bipolar plates, also known as current collectors, are one of the most important components in fuel cells. Their main functions include providing gas flow channels, preventing the mixing of hydrogen and oxygen in the battery gas chamber, and establishing a current path between the positive and negative electrodes in series. According to the type of material, bipolar plates are mainly divided into graphite bipolar plates, composite bipolar plates and metal bipolar plates, each of which has its own advantages and disadvantages. Graphite bipolar plates have excellent corrosion resistance and conductivity, but the high processing cost limits their wide application in the market. Composite bipolar plates have significant advantages in cost and perform well in corrosion resistance, but the current conductivity of composite bipolar plates is still low and has not yet fully met the performance requirements of bipolar plates. Metal bipolar plates significantly enhance corrosion resistance while ensuring good conductivity, thereby significantly extending the service life of fuel cell systems. In addition, the preparation process of metal materials is quite mature, and high-precision complex flow field structures can be processed through stamping, die casting and laser forming processes, which is convenient for large-scale production. Metal materials have become the main choice for preparing proton exchange membrane fuel cell bipolar plates.

[0003] In the prior art, the commonly used matrix materials of metal bipolar plates mainly include stainless steel, aluminum and titanium alloys. Among them, titanium as the substrate of metal bipolar plates has many unique advantages. First, the specific strength of titanium is 3.5 times that of ordinary stainless steel, which means that while ensuring the strength of the bipolar plate, the overall weight of the fuel cell can be significantly reduced, thereby improving the specific power and efficiency of the fuel cell. Secondly, like aluminum, titanium will form a dense oxide film on its surface. This oxide film has good insulation properties, greatly improves the corrosion resistance of titanium materials, and can maintain stable performance in the working environment of fuel cells. In addition, during the operation of the fuel cell, the precipitation of titanium ions has little effect on the contamination of the platinum catalyst in the membrane electrode, which helps to extend the service life of the fuel cell and maintain its efficient electrochemical performance. With the continuous improvement and optimization of titanium materials and their processing technology, it is expected that its application in the field of fuel cells will be further expanded, playing a key role in promoting the commercialization and popularization of fuel cell technology.

[0004] However, the corrosion resistance of bipolar plates made of titanium alloys commonly used in the prior art cannot meet the requirements of long-life operation of fuel cells in sulfuric acid solutions containing fluoride ions. Although titanium alloys have shown excellent performance in many fields, their application in fuel cells still faces challenges, especially the lack of corrosion resistance in highly corrosive environments, which cannot ensure the stable operation and long life of fuel cells under harsh conditions. Summary of the invention

[0005] In view of the defects and shortcomings of the prior art, in a first aspect, the present invention provides a corrosion-resistant titanium alloy bipolar plate; in a second aspect, the present invention provides a method for preparing a corrosion-resistant titanium alloy bipolar plate.

[0006] To achieve the above objectives, the present invention provides the following technical solutions.

[0007] In a first aspect, the present invention provides a corrosion-resistant titanium alloy bipolar plate, comprising niobium, zirconium and tantalum elements; the corrosion-resistant titanium alloy bipolar plate comprises 14-18% niobium, 8-12% zirconium, 3-7% tantalum by mass content, and the remainder being titanium elements and unavoidable impurities.

[0008] More preferably, niobium accounts for 16%, zirconium accounts for 10%, tantalum accounts for 3-7%, and the balance is titanium element and inevitable impurities.

[0009] Preferably, the metallographic phase of the corrosion-resistant titanium alloy bipolar plate includes a main phase and a secondary phase; the main phase is a fine equiaxed β phase; and the second phase is a fine secondary needle-shaped α phase.

[0010] In a second aspect, the present invention provides a method for preparing a corrosion-resistant titanium alloy bipolar plate, comprising the following steps: Step 1, melting and casting the alloy raw materials to obtain a cast alloy billet; Step 2, subjecting the as-cast alloy to high-temperature blanking treatment, followed by hot rolling, annealing, and cold rolling treatment to obtain a densified titanium alloy sheet; wherein the cold rolling process includes multiple rolling processes, and each rolling process is followed by annealing treatment; Step 3, heat treating the densified titanium alloy sheet to obtain a corrosion-resistant titanium alloy bipolar plate; Among them, the titanium-containing raw material in the alloy raw materials is OA grade sponge titanium; other element raw materials are high-purity niobium, high-purity zirconium and high-purity tantalum; in terms of mass content, niobium is 14~18%, zirconium is 8~12%, tantalum is 3~7%, and the balance is titanium and unavoidable impurities.

[0011] Preferably, in step 1, during smelting, a vacuum consumable electrode arc melting furnace is used to repeatedly melt the alloy raw material 2 to 4 times.

[0012] More preferably, the melting temperature is 1800-1900°C.

[0013] Preferably, in step 1, the titanium-containing raw material in the alloy raw material is OA-grade sponge titanium; and the other element raw materials are high-purity niobium, high-purity zirconium and high-purity tantalum.

[0014] Preferably, in step 2, before blanking, the titanium alloy blank is first heated and kept warm, and then hot forging or hot rolling is performed.

[0015] More preferably, the titanium alloy billet is opened 6 to 10 times.

[0016] More preferably, the blank needs to be heated again and kept warm after each opening.

[0017] Further preferably, before opening the embryo, the heating temperature is 950-1060°C and the insulation time is 3-5h.

[0018] Preferably, in step 2, the sheet after embryonic development is heated and kept warm for a period of time, and then hot rolled, annealed, air cooled, and cold rolled in sequence.

[0019] More preferably, the heating temperature of the plate after opening is 800-850°C, and the insulation time is 60-80min.

[0020] Further preferably, in step 2, the hot rolling includes multiple passes, and the deformation of each pass of the hot rolling is controlled at 30-50%; the hot rolling is ended when the thickness of the plate is 3.0-5.0 mm.

[0021] More preferably, in step 2, the annealing temperature after hot rolling is 750-800° C., and the annealing time is 60-80 min.

[0022] Preferably, in step 2, the cold rolling includes 4 to 10 rolling passes; the total deformation of each rolling pass is 40 to 60%.

[0023] Preferably, in the cold rolling process of step 2, the total deformation amount of each rolling process gradually decreases by 5-10% according to the rolling process sequence.

[0024] Further preferably, after each cold rolling process, the plate is annealed under high-temperature vacuum or high-temperature inert gas conditions, and then air-cooled or gas-cooled with inert gas; further preferably, during high-temperature vacuum annealing, the vacuum degree is ≤10Pa; further preferably, the annealing temperature is 600~650℃; and the annealing time is 40~60min.

[0025] Preferably, in step 2, the thickness of the densified titanium alloy sheet obtained is 1 mm.

[0026] Preferably, in step 3, during the heat treatment, the plate is first subjected to a solution treatment, then the plate is water quenched to room temperature, then artificially aged, and then the plate is oil cooled to room temperature.

[0027] More preferably, during the solution treatment, the temperature is 800-850° C., the heating rate is 8-12° C. / min, and the holding time is 120-180 min.

[0028] Further preferably, during the artificial aging treatment, the temperature is 550-650°C and the holding time is 3-7h.

[0029] Compared with the prior art, one or more technical solutions provided by the present invention have at least one of the following beneficial effects: (1) The titanium alloy bipolar plate has good corrosion resistance in a highly corrosive environment, so that the fuel cell can operate stably under harsh conditions, thereby increasing the service life of the fuel cell. In addition, a method for preparing the above-mentioned corrosion-resistant titanium alloy bipolar plate is also disclosed, wherein the alloy raw material is melt-casted and then hot-rolled, annealed, cold-rolled, and heat-treated, so that a titanium alloy thin plate with uniform structure, smooth surface, no defects, and a thickness of 1 mm can be rolled out.

[0030] (2) The present invention proposes a method for preparing a titanium alloy sheet. After each rolling process in the cold rolling process, sufficient annealing is performed to uniformly precipitate the second phase on the grain boundary of the alloy. The prepared densified titanium alloy sheet has a fine grain structure, thereby improving the room temperature plasticity and cold rolling forming performance of the titanium alloy, so that a titanium alloy sheet with uniform structure, smooth surface, no defects and a thickness of 1 mm can be rolled. The fine grains ensure the plasticity of the sheet, so that it meets the plasticity requirements of the titanium alloy bipolar plate for fuel cells in the subsequent stamping process. In addition, the uniform metallographic structure can avoid cold rolling defects (defects such as micro cracks and holes), thereby improving the performance of the bipolar plate. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a metallographic analysis diagram of the corrosion-resistant ultra-thin titanium alloy plate prepared in Example 1; Figure 2 This is a scanning electron microscope image of the corrosion-resistant ultrathin titanium alloy plate prepared in Example 1; Figure 3 This is a metallographic analysis diagram of the corrosion-resistant ultra-thin titanium alloy plate prepared in Example 2; Figure 4 This is a scanning electron microscope image of the corrosion-resistant ultrathin titanium alloy plate prepared in Example 2; Figure 5 This is a metallographic analysis diagram of the corrosion-resistant ultra-thin titanium alloy plate prepared in Example 3; Figure 6 This is a scanning electron microscope image of the corrosion-resistant ultrathin titanium alloy plate prepared in Example 3; Figure 7 The current-potential relationship diagram of the corrosion-resistant ultra-thin titanium alloy plate and Ti-0.5Ru titanium alloy prepared in Example 2 in a sulfuric acid solution environment containing fluoride ions. DETAILED DESCRIPTION

[0032] The present invention provides the following specific technical solutions.

[0033] In a first aspect, the present invention provides a corrosion-resistant titanium alloy bipolar plate, comprising niobium, zirconium and tantalum elements; the titanium alloy bipolar plate comprises 16% niobium, 10% zirconium, 3-7% tantalum by mass content, and the remainder is titanium element and unavoidable impurities.

[0034] Preferably, the metallographic phase of the corrosion-resistant titanium alloy bipolar plate includes a main phase and a secondary phase; the main phase is a fine equiaxed β phase; and the second phase is a fine secondary needle-shaped α phase.

[0035] The inventors have found that pure titanium and titanium alloys in the prior art are not suitable for proton exchange membrane fuel cells when exposed to H + 、F - 、SO4 2- In a corrosive medium environment, the surface conductivity is insufficient and cannot meet the requirements of fuel cell output power and service life. The present invention proposes a corrosion-resistant titanium alloy bipolar plate with good corrosion resistance in a highly corrosive environment, so that the fuel cell can operate stably under harsh conditions and improve the service life of the fuel cell. However, the addition of niobium, zirconium and tantalum elements will cause the alloy to solid dissolve or precipitate a coarse and brittle second phase, thereby reducing the room temperature plasticity of the titanium alloy. In the process of preparing ultra-thin plates, the brittle second phase makes it easy for the plate to form defects such as microcracks and holes during the cold rolling process, which is extremely unfavorable for the preparation of ultra-thin plates. It is difficult to produce a defect-free ultra-thin plate with a thickness of 1 mm using the existing densified titanium alloy sheet preparation process. Based on this, the present invention provides a method for preparing a corrosion-resistant titanium alloy bipolar plate, comprising the following steps: Step 1, melting and casting the alloy raw materials to obtain a cast alloy billet; Step 2, subjecting the as-cast alloy to high-temperature blanking treatment, followed by hot rolling and cold rolling treatment to obtain a densified titanium alloy sheet; Step 3: heat-treating the densified titanium alloy sheet to obtain a corrosion-resistant titanium alloy bipolar plate.

[0036] The specific operations are as follows: (1) Titanium alloy ingredients: accurately weigh the elements according to the ratio and mix the ingredients evenly. The titanium alloy ingredients are composed of 14-18wt% niobium, 8-12wt% zirconium, 3-7wt% tantalum, and the balance is titanium and unavoidable impurities. (2) Preparation of titanium alloy ingots: A titanium alloy cylindrical ingot with uniform composition is prepared by a vacuum consumable electrode arc melting method. The titanium alloy ingot is repeatedly remelted 2 to 4 times to ensure the uniformity of the composition of the ingot; (3) Billeting of titanium alloy ingot: the above-mentioned final ingot is machined into a cylindrical billet, the billet obtained in the previous step is first machined to achieve surface finishing, and then the as-cast billet is subjected to high-temperature billeting treatment. During high-temperature billeting, the as-cast titanium alloy billet is first heated to 950-1000°C and kept warm for 3-5 hours, and then 6-10 times of hot forging billeting or hot rolling billeting are performed. After each billeting, the billet needs to be reheated to 950-1000°C and kept warm for 3-5 hours, and finally a square billet is made; (4) Preparation of titanium alloy hot-rolled plates: The square billet obtained by blanking is heated to 800-850°C and kept at this temperature for 60-80 min, and then hot rolled. The plate is rolled to 3.0-5.0 mm by multiple hot rolling passes, and then annealed at a temperature of 750-800°C for 60-80 min, followed by air cooling. The deformation of each hot rolling pass is controlled at 30-50%, and the thickness of the hot-rolled plate is controlled at 3.0-5.0 mm. (5) Preparation of densified titanium alloy sheet: The hot-rolled titanium alloy sheet obtained in the previous step is cold rolled. The cold rolling process is 4 to 10 rolling passes. The total deformation of each rolling pass is controlled at 40 to 60%. The total deformation of each rolling pass is gradually reduced according to the rolling pass sequence. Each rolling pass is annealed at a temperature of 600 to 650 ° C and vacuum or inert gas for 40 to 60 minutes, and then air-cooled or inert gas-cooled to prepare a densified titanium alloy sheet with a thickness of 1 mm. (6) Annealing of densified titanium alloy sheet: The titanium alloy sheet obtained in the previous step is subjected to heat treatment, wherein the heat treatment method is solid solution treatment, the temperature is 800-850°C, the heating rate is 8-12°C / min, and the holding time is 120-180min; after the heat treatment, the sheet is water quenched to room temperature, and then artificially aged at 550-650°C for 3-7h and oil cooled to room temperature.

[0037] The present invention has no particular limitation on the type of the alloy raw material, and the alloy raw materials known to those skilled in the art are used so as to obtain a titanium alloy of target composition. In the present invention, the alloy raw materials preferably include sponge titanium, pure zirconium, pure niobium and pure tantalum.

[0038] The present invention melts and casts the alloy raw material to obtain a cast alloy billet. Before smelting, the present invention preferably ultrasonically cleans the alloy raw material. The present invention has no special requirements for the specific implementation of the ultrasonic cleaning, and the method well known to those skilled in the art can be adopted.

[0039] The present invention performs an embryonic treatment on the heated and heat-insulated cast alloy to obtain a densified alloy billet. The embryonic treatment process is preferably hot rolling, and the total deformation amount of hot rolling deformation is preferably 65-80%, and more preferably 70-75%. The present invention performs a deformation treatment after heat preservation treatment to cause thermal deformation, refine the grains, and generate a large number of dislocations, which helps to improve the strength and plasticity of the alloy; the embryonic treatment by hot rolling can effectively eliminate casting defects, compact the structure, and refine the grains. The hot rolling process can generate a large number of dislocations, which can improve the mechanical properties of the alloy in the rolling direction.

[0040] The present invention has no special requirements on the specific implementation of the rolling deformation, and any method known to those skilled in the art may be adopted.

[0041] The hot rolling process after embryo opening of the present invention adopts a multi-pass rolling deformation method to control the deformation amount of a single pass, overcome the thermal processing resistance of the titanium alloy, and achieve the finest possible grains; and the present invention adopts multi-pass rolling, which is more conducive to the crushing and refinement of the matrix structure grains and is not easy to crack.

[0042] The present invention performs a solution treatment on the densified alloy billet; the cooling method of the solution treatment is preferably water quenching, and it is further preferred to perform water quenching in room temperature water. The present invention has no special requirements for the specific implementation of the solution treatment, and an implementation method familiar to those skilled in the art can be adopted. The insulation process of the solution treatment is preferably carried out under a protective atmosphere, and the protective atmosphere is specifically an argon protective atmosphere. The solution treatment can eliminate the residual stress caused by thermal deformation as much as possible, thereby improving the strength of the material while having a certain plasticity, and better regulating the performance of the alloy.

[0043] The present invention improves the stability and corrosion resistance of the alloy in a corrosive environment through the synergistic effect of each element, and the solid solution formed by Ta and Ti can further enhance the solid solution strengthening effect. The passivation potential of the Ta element is more negative than that of the Ti element, and the passivation reaction can be promoted even in a weakly oxidizing environment, thereby improving the ability to form a dense surface oxide film, significantly improving the corrosion resistance of the alloy, and achieving solid solution strengthening. In addition, the main phase and the second phase of the titanium alloy bipolar plate provided by the present invention have fine grains and few structural defects, which can further improve the strength of the alloy, thereby improving the stability of the titanium alloy bipolar plate in a highly corrosive environment and the operating life of the fuel cell.

[0044] In order to make the technical problems, technical solutions and technical advantages to be solved by the present invention more clear, they will be described in detail below with reference to specific examples, but the protection scope of the present invention is not limited to the following specific embodiments.

[0045] Unless otherwise defined, all professional terms used below have the same meanings as those generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0046] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0047] Embodiment 1: Step 1: OA-grade titanium sponge, high-purity niobium, high-purity zirconium and high-purity tantalum are precisely weighed and mixed evenly according to an element ratio of 16wt.% of niobium element, 10wt.% of zirconium element, 3wt.% of tantalum element and the remainder of titanium element to obtain a mixed metal powder.

[0048] Step 2, using vacuum consumable electrode arc melting to melt and cast 60 kg of mixed metal powder at 1850° C. for 4 hours to prepare a titanium alloy cylindrical ingot with uniform composition, and the titanium alloy ingot is repeatedly remelted 3 times.

[0049] Step 3, heating the titanium alloy cylindrical ingot to 950° C. and keeping it warm for 3 hours, then hot forging and blanking by a fast forging machine, repeating the heating, keeping warm and blanking steps 6 times, and the manufactured square blank has a thickness of 50 mm, thereby obtaining a titanium alloy blank.

[0050] Step 4, heating the titanium alloy billet to 800°C and keeping it warm for 60 minutes, then hot rolling the plate on a hot rolling mill, controlling the deformation of the hot rolling pass to 30%, and annealing when the thickness of the hot-rolled plate is controlled to 3 mm, the annealing temperature is 750°C, the annealing time is 60 minutes, and then air cooling is performed to obtain a titanium alloy hot-rolled plate.

[0051] Step 5: Cold-roll the hot-rolled titanium alloy plate using a cold rolling mill. The cold rolling process is divided into four rolling passes, and the total deformation of the four rolling passes is 60%, 55%, 50%, and 40%, respectively. After each rolling pass, the plate is annealed at 600°C under inert gas for 40 minutes, and then air-cooled to finally prepare a densified titanium alloy sheet with a thickness of 1 mm.

[0052] Step 6, heat treating the densified titanium alloy thin plate by solution treatment at a temperature of 800°C, a heating rate of 8°C / min, and a holding time of 120min; after heat treatment, quenching with water to room temperature, and then artificially aging at 600°C for 5h and then oil cooling to room temperature to obtain a corrosion-resistant ultra-thin titanium alloy plate.

[0053] Embodiment 2: Step 1: OA-grade titanium sponge, high-purity niobium, high-purity zirconium and high-purity tantalum are precisely weighed and mixed evenly according to an element ratio of 14wt.% of niobium element, 8wt.% of zirconium element, 5wt.% of tantalum element and the remainder of titanium element to obtain a mixed metal powder.

[0054] Step 2, using vacuum consumable electrode arc melting to melt and cast mixed metal powder, using vacuum consumable electrode arc melting to melt and cast 60 kg of mixed metal powder, melting and casting at 1800° C. for 4 hours; preparing a titanium alloy cylindrical ingot with uniform composition, and repeatedly remelting the titanium alloy ingot 3 times.

[0055] Step 3, heating the titanium alloy cylindrical ingot to 980° C. and keeping it warm for 4 hours, then hot forging and blanking by a fast forging machine, repeating the heating, keeping warm and blanking steps 6 times, and the manufactured square blank has a thickness of 50 mm, thereby obtaining a titanium alloy blank.

[0056] Step 4, heating the titanium alloy billet to 820°C and keeping it warm for 70 minutes, then hot rolling the plate on a hot rolling mill, controlling the deformation of the hot rolling pass to 30%, and annealing when the thickness of the hot-rolled plate is controlled to 3 mm, the annealing temperature is 780°C, the annealing time is 70 minutes, and then air cooling to obtain a titanium alloy hot-rolled plate.

[0057] Step 5: Cold-roll the hot-rolled titanium alloy plate using a cold rolling mill. The cold rolling process is divided into 6 rolling processes. The total deformation of the 6 rolling processes is 60%, 56%, 52%, 48%, 44%, and 40%, respectively. After each rolling process, the plate is annealed at 620°C under inert gas for 50 minutes, and then air-cooled to finally prepare a densified titanium alloy sheet with a thickness of 1 mm.

[0058] Step 6, heat treating the densified titanium alloy thin plate by solution treatment at 820°C, a heating rate of 10°C / min, and a holding time of 150min; after heat treatment, water quenching is performed to room temperature, and then artificial aging treatment is performed at 600°C for 5h and then oil cooling is performed to room temperature to obtain a corrosion-resistant ultra-thin titanium alloy plate.

[0059] Embodiment 3: Step 1: OA-grade titanium sponge, high-purity niobium, high-purity zirconium and high-purity tantalum are precisely weighed and mixed evenly according to an element ratio of 18wt.% of niobium element, 12wt.% of zirconium element, 7wt.% of tantalum element and the balance of titanium element to obtain a mixed metal powder.

[0060] Step 2, using vacuum consumable electrode arc melting to melt and cast mixed metal powder, using vacuum consumable electrode arc melting to melt and cast 60 kg of mixed metal powder, melting and casting at 1900° C. for 4 hours; preparing a titanium alloy cylindrical ingot with uniform composition, and repeatedly remelting the titanium alloy ingot 3 times.

[0061] Step 3, heating the titanium alloy cylindrical ingot to 1000° C. and keeping it warm for 5 hours, then hot forging and blanking by using a fast forging machine, repeating the heating, keeping warm and blanking steps 6 times, and the manufactured square blank has a thickness of 50 mm, thereby obtaining a titanium alloy blank.

[0062] Step 4, heating the titanium alloy billet to 850°C and keeping it warm for 80 minutes, then hot rolling the plate on a hot rolling mill, controlling the deformation of the hot rolling pass to 30%, and annealing when the thickness of the hot-rolled plate is controlled to 3 mm, the annealing temperature is 800°C, the annealing time is 80 minutes, and then air cooling to obtain a titanium alloy hot-rolled plate.

[0063] Step 5, cold rolling the hot-rolled titanium alloy plate by a cold rolling mill. The cold rolling process is divided into 8 rolling processes. The total deformation of the 8 rolling processes is 60%, 57%, 54%, 51%, 58%, 46%, 43% and 40%, respectively. After each rolling process, the plate needs to be annealed at 650°C under inert gas for 60 minutes, and then air-cooled to finally prepare a densified titanium alloy sheet with a thickness of 1 mm.

[0064] Step 6, heat treating the densified titanium alloy thin plate by solution treatment at 850°C, a heating rate of 12°C / min, and a holding time of 180min; after heat treatment, quenching with water to room temperature, and then artificially aging at 600°C for 5h and then oil cooling to room temperature to obtain a corrosion-resistant ultra-thin titanium alloy plate.

[0065] Figure 1 This is the metallographic analysis diagram of the titanium alloy obtained in Example 1. Figure 2 is a scanning electron microscope image of the titanium alloy obtained in Example 1, Figure 1 and Figure 2 It can be seen that the titanium alloy prepared in Example 1 is composed of fine equiaxed β phase and secondary needle-shaped α phase, and the sizes of the equiaxed β phase and the secondary needle-shaped α phase are similar, both of which are about 45-50 μm.

[0066] Figure 3 This is the metallographic analysis diagram of the titanium alloy obtained in Example 2. Figure 4 is a scanning electron microscope image of the titanium alloy obtained in Example 2, Figure 3 and Figure 4 It can be seen that the titanium alloy prepared in Example 2 is composed of fine equiaxed β phase and secondary needle-shaped α phase, and the sizes of the equiaxed β phase and the secondary needle-shaped α phase are similar, both of which are about 45-50 μm.

[0067] Figure 5 This is the metallographic analysis diagram of the titanium alloy obtained in Example 3. Figure 6 is a scanning electron microscope image of the titanium alloy obtained in Example 3, Figure 5 and Figure 6It can be seen that the titanium alloy prepared in Example 3 is composed of fine equiaxed β phase and secondary needle-shaped α phase, and the sizes of the equiaxed β phase and the secondary needle-shaped α phase are similar, both of which are about 45-50 μm.

[0068] Depend on Figure 1 , Figure 3 and Figure 5 It can be proved that the main phase and the secondary phase in the corrosion-resistant titanium alloy bipolar plate provided by the present invention have fine grains and few structural defects, which can also be proved from the side that the strength of the corrosion-resistant titanium alloy bipolar plate provided by the present invention is improved, thereby improving the stability of the titanium alloy bipolar plate in a highly corrosive environment and the operating life of the fuel cell.

[0069] The corrosion-resistant ultra-thin titanium alloy plate prepared in Example 2 and the Ti-0.5Ru titanium alloy commonly used in the prior art were made into the shape of bipolar plates that meet the requirements, and then the characteristics of the proton exchange membrane fuel cell bipolar plates were tested in accordance with the national standard GB / T20042.6-2011. The tests were carried out using an electrochemical workstation at a test temperature of 80°C and a 0.5M sulfuric acid + 5ppm fluoride ion solution. Figure 7 The current-potential relationship curves of the corrosion-resistant ultra-thin titanium alloy plate and the bipolar plate made of Ti-0.5Ru titanium alloy prepared in Example 2 are shown in FIG. Figure 7 It can be seen that the corrosion current of the corrosion-resistant ultra-thin titanium alloy plate obtained in Example 2 is much smaller than the corrosion current of Ti-0.5Ru, which shows that the titanium alloy provided by the present invention has excellent corrosion resistance. It can be reasonably predicted that the use of the titanium alloy plate provided by the present invention to prepare bipolar plates can enable the fuel cell to operate stably under harsh conditions and improve the long life of the fuel cell.

[0070] The embodiments described above are only preferred specific implementation modes of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical solutions and concepts of the present invention within the technical scope of the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A corrosion-resistant titanium alloy bipolar plate, characterized in that: Including niobium, zirconium and tantalum elements; the corrosion-resistant titanium alloy bipolar plate contains 14-18% niobium, 8-12% zirconium, 3-7% tantalum by mass content, and the remainder is titanium and unavoidable impurities.

2. The corrosion-resistant titanium alloy bipolar plate according to claim 1, characterized in that: The metallographic phase of the corrosion-resistant titanium alloy bipolar plate includes a main phase and a secondary phase; the main phase is a fine equiaxed β phase; and the second phase is a fine secondary needle-shaped α phase.

3. A method for preparing a corrosion-resistant titanium alloy bipolar plate, characterized in that: The steps include: Step 1, melting and casting the alloy raw materials to obtain a cast alloy billet; Step 2, subjecting the as-cast alloy to high-temperature blanking treatment, followed by hot rolling, annealing, and cold rolling treatment to obtain a densified titanium alloy sheet; wherein the cold rolling process includes multiple rolling processes, and each rolling process is followed by annealing treatment; Step 3, heat treating the densified titanium alloy sheet to obtain a corrosion-resistant titanium alloy bipolar plate; Among them, the titanium-containing raw material in the alloy raw materials is OA grade sponge titanium; other element raw materials are high-purity niobium, high-purity zirconium and high-purity tantalum; in terms of mass content, the niobium is 14~18%, the zirconium is 8~12%, the tantalum is 3~7%, and the balance is titanium and unavoidable impurities.

4. The method for preparing the corrosion-resistant titanium alloy bipolar plate according to claim 3, characterized in that: In step 1, during smelting, a vacuum consumable electrode arc melting furnace is used to repeatedly melt the alloy raw material 2 to 4 times; the smelting temperature is 1800 to 1900° C.; the titanium-containing raw material in the alloy raw material is OA-grade sponge titanium; and other element raw materials are high-purity niobium, high-purity zirconium and high-purity tantalum.

5. The method for preparing the corrosion-resistant titanium alloy bipolar plate according to claim 3, characterized in that: In step 2, before opening the blank, the titanium alloy blank is first heated and kept warm, and then hot forging or hot rolling is performed; the titanium alloy blank is opened 6 to 10 times; after each opening, the blank needs to be heated again and kept warm, the heating temperature is 950 to 1060°C, and the holding time is 3 to 5 hours.

6. The method for preparing the corrosion-resistant titanium alloy bipolar plate according to claim 3 or 5, characterized in that: In step 2, the cast alloy is heated to 800-850° C. and kept at this temperature for 60-80 minutes before hot rolling; the hot rolling includes multiple passes, and the deformation of each pass of the hot rolling is controlled at 30-50%; the hot rolling is terminated when the thickness of the plate is 3.0-5.0 mm.

7. The method for preparing the corrosion-resistant titanium alloy bipolar plate according to claim 3 or 5, characterized in that: In step 2, the annealing temperature after hot rolling is 750-800°C, and the annealing time is 60-80 minutes.

8. The method for preparing the corrosion-resistant titanium alloy bipolar plate according to claim 3, characterized in that: In step 2, the cold rolling includes 4 to 10 rolling passes; the total deformation of each rolling pass is 40 to 60%; further preferably, in the cold rolling process, the total deformation of each rolling pass gradually decreases by 5 to 10% according to the order of the rolling passes.

9. The method for preparing the corrosion-resistant titanium alloy bipolar plate according to claim 3 or 7, characterized in that: After each cold rolling process, the plates are annealed under high temperature vacuum or high temperature inert gas conditions, and then air cooled or cooled with inert gas. The annealing temperature is 600~650℃; the annealing time is 40~60min.

10. The method for preparing the corrosion-resistant titanium alloy bipolar plate according to claim 3, characterized in that: In step 3, during heat treatment, the plate is first subjected to solution treatment, then water quenched to room temperature, then artificially aged, and then oil cooled to room temperature; The method for preparing a corrosion-resistant titanium alloy bipolar plate according to claim 9, characterized in that: During solution treatment, the temperature is 800~850℃, the heating rate is 8~12℃ / min, and the holding time is 120~180min; during artificial aging treatment, the temperature is 550~650℃, and the holding time is 3~7h.

Images