Hydrogen embrittlement-resistant high-strength titanium alloy and preparation method thereof

Abstract

The invention discloses a hydrogen embrittlement-resistant high-strength titanium alloy and a preparation method thereof. The hydrogen embrittlement-resistant high-strength titanium alloy comprises the following components in percentage by mass: 5.5%-6.5% of aluminum, 3.5%-4.5% of tin, 3.2%-3.8% of zirconium, 0.4%-0.6% of molybdenum, 0.7%-1.2% of tungsten, 0.25%-0.35% of niobium, 0.4%-0.6% of silicon, 0.8%-1.2% of yttrium, 0.03%-0.08% of carbon and the balance of titanium and inevitable impurities. The hydrogen embrittlement-resistant high-strength titanium alloy is prepared through the following steps that after cogging treatment is carried out on a smelted as-cast alloy blank, forging and heat treatment are carried out. The titanium alloy has no hydrogen embrittlement phenomenon after hydrogen charging stretching, the strength and hydrogen embrittlement resistance of the material are both considered, the Rm after hydrogen charging can reach 1180 MPa and is higher than that before hydrogen charging, and the ductility after hydrogen charging can reach 11.3% and is equivalent to that before hydrogen charging.

Description

Technical Field

[0001] The invention belongs to the field of titanium alloys, and in particular relates to a hydrogen embrittlement-resistant high-strength titanium alloy and a preparation method thereof. Background Art

[0002] As a typical lightweight and high-strength metal material, titanium alloy has been widely used in aerospace, marine engineering, chemical equipment and biomedical fields due to its excellent specific strength, corrosion resistance, high temperature resistance and good biocompatibility. With the development of technology, titanium alloy materials are increasingly used to manufacture key load-bearing components with high strength and high stability, such as aircraft engine components, rocket shells, deep-sea probe shells and chemical reactors. However, in these extreme service environments, the infiltration and accumulation of hydrogen poses a serious threat to the mechanical properties of titanium alloys, easily causing hydrogen embrittlement, resulting in a significant decrease in the plasticity and toughness of the material, and even sudden fracture, which greatly affects its service life and safety.

[0003] Hydrogen embrittlement refers to the process in which hydrogen diffuses and penetrates into the interior of metal materials, accumulating at grain boundaries, subgrain boundaries or crystal defects, thereby reducing the deformation capacity of the material and causing the material to exhibit a more brittle form of failure than before. For titanium alloys, the intrusion of hydrogen atoms will trigger a series of complex phase changes and microstructural evolution, specifically manifested in the segregation of hydrogen atoms in the α phase and β phase, the formation of hydrides (such as TiH 2 The formation of ) phases eventually causes local stress concentration and micro cracks in the material. The presence of these hydride phases makes titanium alloys more sensitive to hydrogen embrittlement in hydrogen environments, especially under high temperature or high pressure conditions, where the hydrogen embrittlement problem becomes more significant.

[0004] In order to improve the hydrogen embrittlement resistance of titanium alloys in hydrogen environment, traditional technologies are usually improved in the following ways: first, optimize the alloy composition design, and inhibit the diffusion of hydrogen and the formation of hydride phase by adding elements such as palladium (Pd), chromium (Cr), and vanadium (V); second, adjust the microstructure, control the ratio and morphology of α phase and β phase through heat treatment process, and reduce the segregation of hydrogen at grain boundaries and phase interfaces. However, these methods have obvious limitations in practical applications: on the one hand, the composition design is complex, the alloy cost is high, and some added elements may lead to the deterioration of material toughness and processing performance; on the other hand, traditional heat treatment processes are difficult to take into account both the strength and hydrogen embrittlement resistance of the material, especially when further strengthening high-strength titanium alloys, which is often accompanied by a significant decrease in hydrogen embrittlement resistance.

[0005] Therefore, in response to these problems, the present invention proposes a high-strength titanium alloy rod with hydrogen embrittlement resistance and a preparation method thereof to meet the use requirements of high-strength titanium alloy components that serve for a long time in a hydrogen environment. Summary of the invention

[0006] The technical problem to be solved by the present invention is to overcome the deficiencies and defects mentioned in the above background technology and provide a hydrogen embrittlement resistant high-strength titanium alloy and a preparation method thereof.

[0007] In order to solve the above technical problems, the technical solution proposed by the present invention is:

[0008] A high-strength titanium alloy resistant to hydrogen embrittlement, comprising the following components by mass content: 5.5-6.5% aluminum, 3.5-4.5% tin, 3.2-3.8% zirconium, 0.4-0.6% molybdenum, 0.7-1.2% tungsten, 0.25-0.35% niobium, 0.4-0.6% silicon, 0.8-1.2% yttrium, 0.03-0.08% carbon, and the balance being titanium element and unavoidable impurities;

[0009] The hydrogen embrittlement resistant high-strength titanium alloy is prepared by the following steps: after the smelted cast alloy billet is opened, forging and heat treatment are performed;

[0010] The forging includes: reforming forging at 1020-1050°C, reforming forging and forming at 860-940°C, and rolling forming at 900-950°C.

[0011] As a further improvement, it contains the following components by mass content: 5.8% aluminum, 4% tin, 3.5% zirconium, 0.5% molybdenum, 1% tungsten, 0.3% niobium, 0.5% silicon, 1% yttrium, 0.05% carbon, and the balance is titanium element and inevitable impurities.

[0012] The present invention also provides a method for preparing the hydrogen embrittlement resistant high-strength titanium alloy, comprising the following steps:

[0013] S1, mixing alloy raw materials, pressing them into electrode blocks, making the electrode blocks into consumable electrodes, and smelting them to obtain cast alloy billets;

[0014] S2, forging the as-cast alloy billet after billet opening to obtain a titanium alloy bar;

[0015] S3. The forged titanium alloy rod is heat treated to obtain a hydrogen embrittlement-resistant high-strength titanium alloy rod.

[0016] As a further improvement, titanium is added to S1 in the form of sponge titanium, zirconium is added in the form of sponge zirconium, aluminum is added in the form of intermediate alloy and high-purity aluminum, tin is added in the form of high-purity Ti-Sn intermediate alloy, molybdenum is added in the form of Al-Mo intermediate alloy, silicon is added in the form of Al-Si intermediate alloy, tungsten is added in the form of Al-W intermediate alloy, and carbon is added in the form of carbon powder.

[0017] As a further improvement, S1 uses a vacuum consumable electrode arc melting furnace to repeatedly melt the alloy raw materials three times, and the melting temperature is controlled at 1910°C to 1930°C.

[0018] As a further improvement, the blanking treatment in S2 includes: heating the cast alloy blank to 1150-1200° C. for homogenization treatment, and then hot forging the blank.

[0019] As a further improvement, the hot forging blanking deformation is not less than 40%.

[0020] As a further improvement, the forging in S2 includes, in sequence:

[0021] 1) Forging at 1020-1050℃, repeated upsetting and drawing forging, with deformation not less than 50%;

[0022] 2) Forging and forming at 860-940℃, repeated upsetting and drawing forging, and the single pressing deformation during the drawing period does not exceed 20mm;

[0023] 3) Perform multiple rolling processes at 900-950°C, with the deformation of each process being ≤10%.

[0024] As a further improvement, the heat treatment in S3 is first solution treatment and then artificial aging treatment.

[0025] As a further improvement, the temperature of the solution treatment is 900-1025°C, and the temperature of the artificial aging treatment is 550-720°C.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] Research has found that rare earth element Y usually forms rare earth oxides, rare earth carbides or rare earth nitrides in titanium alloys, forming fine, dispersed precipitates in titanium alloys, which act as "hydrogen capture agents", reduce the enrichment of hydrogen at grain boundaries, and effectively inhibit the formation of hydrides. These second phases can form stable hydrogen traps inside the grains or at the grain boundaries, thereby significantly reducing the free diffusion rate of hydrogen in the matrix.

[0028] Si is an important high-temperature strengthening element in titanium alloys, which can effectively enhance the performance of solid solutions. The solubility of Si in β-titanium is significantly higher than that in α-titanium, and as the temperature rises, the solubility of Si in α-titanium gradually increases. Si generally exists in two forms: one is solid solution in the matrix, and the other is precipitation in the form of silicide. These two forms improve the thermal strength of titanium alloys through solid solution strengthening and precipitation strengthening, respectively. Common silicides have two crystal structures: S1 type (Ti, Zr) 5 Si 3and S2 type (Ti, Zr) 6 Si 3 The precipitation behavior and growth process of silicides are affected by factors such as alloy composition, heat treatment process and heat treatment conditions, among which the heating temperature has a particularly significant effect on the precipitation, distribution, morphology and particle size of silicides. The two types of silicides in the alloy of the present invention are distributed inside the matrix or at the grain boundaries, forming stable strong hydrogen traps that can effectively inhibit the diffusion of hydrogen into the material.

[0029] The alloy elements of the present invention are used in combination with the hot working process of the present invention and the optimized process conditions, and the microstructure of the alloy obtained is a three-state structure, which generally has better hydrogen embrittlement resistance than the Widmanstatten structure. This is because the uniform two-state or three-state structure can reduce the enrichment of hydrogen at local positions, reducing the possibility of the formation of hydride phases at grain boundaries or phase interfaces.

[0030] The fine grain structure of the alloy of the present invention can significantly improve the comprehensive mechanical properties of the alloy and hinder the diffusion of hydrogen atoms along the grain boundaries to a certain extent. Adding trace elements (such as Si and Mo) at the grain boundaries of the alloy can further inhibit the segregation effect of hydrogen. This is because by introducing a suitable second phase or microscopic defects into the alloy, an effective hydrogen trap can be formed, thereby reducing the diffusion and aggregation of hydrogen in the matrix.

[0031] The alloy after forging and rolling of the present invention will generate a large number of dislocation lines, dislocation entanglements and vacancy clusters in the alloy during plastic deformation or high temperature treatment, and these defects can form effective hydrogen traps in the material. When hydrogen atoms diffuse to these dislocation lines or vacancy clusters, they will be effectively restrained, reducing their movement to grain boundaries or subgrain boundaries, thereby reducing the precipitation of hydrides at grain boundaries. By introducing a high-density dislocation structure (through a large plastic deformation process), the hydrogen capture ability of the material can be significantly improved.

[0032] The present invention starts with the selection of raw materials, adopts the vacuum melting process, and then melts forging and heat treatment, which can avoid the absorption of hydrogen and minimize the introduction of harmful elements such as excessive hydrogen, oxygen, and nitrogen, because they will significantly increase the hydrogen embrittlement sensitivity of the alloy, and can avoid a significant impact on the mechanical properties of the alloy.

[0033] The present invention significantly reduces the diffusion coefficient of hydrogen in titanium alloy and the segregation effect of hydrogen at grain boundaries and phase boundaries through optimized alloy composition design, thereby effectively inhibiting the formation of hydride phase; secondly, a reasonable heat treatment process enables the alloy to obtain a more uniform microstructure, effectively improving the plasticity and toughness of the material.

[0034] The titanium alloy of the present invention will not suffer from hydrogen embrittlement after hydrogen charging and stretching, and both the strength and hydrogen embrittlement resistance of the material are taken into consideration. mIt can reach 1180MPa, which is higher than before hydrogen charging. The elongation after hydrogen charging can reach 11.3%, which is equivalent to that before hydrogen charging. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0036] Figure 1 This is a 200-fold metallographic image of the titanium alloy obtained in Example 1;

[0037] Figure 2 This is a 500-fold metallographic image of the titanium alloy obtained in Example 1;

[0038] Figure 3 This is a 200-fold metallographic image of the titanium alloy obtained in Example 2;

[0039] Figure 4 This is a 500-fold metallographic image of the titanium alloy obtained in Example 2;

[0040] Figure 5 This is the fracture morphology of Example 2 after hydrogen filling and stretching; Figure 6 This is a partial picture of the fracture morphology of Example 2 after hydrogen filling and stretching. DETAILED DESCRIPTION

[0041] In order to facilitate the understanding of the present invention, the present invention will be described more comprehensively and meticulously below in conjunction with the accompanying drawings and preferred embodiments of the present invention, but the protection scope of the present invention is not limited to the following specific embodiments.

[0042] 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.

[0043] 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.

[0044] In some specific embodiments, the hydrogen embrittlement resistant high-strength titanium alloy of the present invention contains the following components by mass content: 5.5-6.5% aluminum, 3.5-4.5% tin, 3.2-3.8% zirconium, 0.4-0.6% molybdenum, 0.7-1.2% tungsten, 0.25-0.35% niobium, 0.4-0.6% silicon, 0.8-1.2% yttrium, 0.03-0.08% carbon, and the balance is titanium element and unavoidable impurities.

[0045] Preferably, the following components are contained in mass content: 5.8% aluminum, 4% tin, 3.5% zirconium, 0.5% molybdenum, 1% tungsten, 0.3% niobium, 0.5% silicon, 1% yttrium, 0.05% carbon, and the balance is titanium element and inevitable impurities.

[0046] In some specific embodiments, the method for preparing the hydrogen embrittlement resistant high-strength titanium alloy of the present invention comprises the following steps:

[0047] S1, mixing alloy raw materials, pressing them into electrode blocks, making the electrode blocks into consumable electrodes, and smelting them to obtain cast alloy billets (ingots);

[0048] Preferably, the raw materials are prepared according to the technical standards, the raw materials are mechanically mixed using a mixer, the mixed raw materials are pressed into electrode blocks using a hydraulic press, the electrode blocks are stacked and welded into consumable electrodes using a vacuum plasma welding box, and the consumable electrodes are then melted in a vacuum consumable electrode arc melting furnace to obtain a cast alloy billet, which is then inspected and the riser and ingot tail are removed.

[0049] The present invention has no particular limitation on the type of alloy raw materials, and alloy raw materials familiar to those skilled in the art are used so as to obtain a titanium alloy of target composition.

[0050] Preferably, titanium is added in the form of titanium sponge, which is 0A-0 grade in GB / T 2524 standard and has a particle size of 0.83-12.7 mm; zirconium is added in the form of zirconium sponge, aluminum is added in the form of master alloy and high-purity aluminum, tin is added in the form of high-purity Ti-Sn master alloy, molybdenum is added in the form of Al-Mo master alloy, silicon is added in the form of Al-Si master alloy, tungsten is added in the form of Al-W master alloy, and carbon is added in the form of carbon powder. The remaining elements are master alloys with low impurity content, melting point, density and particle size close to the base metal.

[0051] Preferably, the alloy raw material is repeatedly smelted three times in a vacuum consumable electrode arc melting furnace to improve smelting uniformity and minimize element segregation. During smelting, the smelting temperature is controlled at 1910°C to 1930°C to ensure that the alloy is completely melted and reaches a stable metallurgical state.

[0052] Preferably, the smelting current during smelting the alloy is 24KA, the voltage is 35KV, and the pressure in the furnace during the last smelting stable stage is no more than 5Pa.

[0053] S2. The smelted cast alloy billet is subjected to high temperature billeting treatment, and then forged with multiple firings, different temperatures and different deformation amounts to obtain a titanium alloy rod.

[0054] The high temperature blanking treatment is preferably performed by heating and keeping the titanium alloy blank before blanking, and then hot forging the blank to obtain a titanium alloy forged blank. Further preferably, the cast alloy blank is heated to 1150-1200°C in the single-phase region for homogenization treatment, and then a fast forging machine or a hydraulic press is used for upsetting and drawing, with rapid upsetting and drawing, and the deformation amount is not less than 40%, and the deformation speed is 40-50 mm / s. The initial forging temperature is ≥1000°C, and the final forging temperature is ≥900°C.

[0055] The forging preferably includes the following three stages:

[0056] 1) Forge the titanium alloy billet in the α+β phase region, and when heated to 1020-1050℃ in the α+β two-phase region, use a fast forging machine or a hydraulic press to perform repeated upsetting and drawing forging, with a deformation amount of not less than 50% and a deformation speed of 40-50mm / s. The initial forging temperature is ≥900℃, and the final forging temperature is ≥800℃.

[0057] 2) The titanium alloy forging blank is forged and formed in the α+β phase region. When heated to 860℃-940℃ in the α+β two-phase region, a fast forging machine or a hydraulic press is used for repeated upsetting and drawing forging. The single pressing deformation during the drawing period does not exceed 20mm, and the deformation rate is 20-25mm / s. The initial forging temperature is ≥800℃, and the final forging temperature is ≥700℃.

[0058] 3) The titanium alloy forging blank is multi-pass rolled and formed in the α+β phase region, the heating temperature is 900-950° C., and the forging blank is rolled into shape, and the deformation of each pass is ≤10%.

[0059] S3. The forged titanium alloy rod is placed in a resistance furnace with an inert gas for multiple heat treatments to obtain a finished high-strength titanium alloy rod resistant to hydrogen embrittlement.

[0060] Preferably, in step 3, during the heat treatment, the rod is first subjected to a solution treatment, then the rod is oil-cooled to room temperature, then subjected to an artificial aging treatment, and then the rod is air-cooled to room temperature.

[0061] Preferably, during the solution treatment, the temperature is 900-1025° C., the heating rate is 8-12° C. / min, and the holding time is 120-480 min.

[0062] Preferably, during artificial aging treatment, the temperature is 550-720°C, the holding time is 4-10 hours, and then air-cooled.

[0063] The hydrogen embrittlement resistant high-strength titanium alloy of the present invention has a tri-state structure, wherein the three phases are respectively two sizes of equiaxed primary α phase and lath-shaped secondary α phase or the three phases are respectively equiaxed primary α phase and two sizes of coarse and fine lath-shaped secondary α phase.

[0064] Embodiment 1:

[0065] Step 1, titanium is added in the form of small-grained 0a-grade sponge titanium, zirconium is added in the form of sponge zirconium, aluminum is added in the form of master alloy and high-purity aluminum, tin is added in the form of high-purity Ti-Sn master alloy, molybdenum is added in the form of Al-Mo master alloy, silicon is added in the form of Al-Si master alloy, tungsten is added in the form of Al-W master alloy, and carbon is added in the form of carbon powder. Yttrium uses high-purity yttrium, and the remaining elements are added in the form of master alloy, according to the ingredients of 5.8wt.% aluminum, 4wt.% tin, 3.5wt.% zirconium, 0.5wt.% molybdenum, 1wt.% tungsten, 0.3wt.% niobium, 1wt.% yttrium, 0.5wt.% silicon, 0.05wt.% carbon, and the balance is titanium. The configured alloy is mechanically mixed in a mixer for 2 hours to ensure that it is evenly mixed.

[0066] Step 2: Press the mixed raw materials into electrode blocks, stack and weld the electrode blocks into consumable electrodes using a vacuum plasma welding box. The density of the electrode blocks is 3.45-3.50 g / cm 3 The alloy raw materials were repeatedly melted three times in a vacuum consumable electrode arc melting furnace. During the melting, the melting temperature was controlled at 1920℃-1930℃, the melting current was 24KA, the voltage was 35KV, and the pressure in the furnace during the last melting stabilization stage should not be greater than 5Pa. The ultrasonic flaw detection of the cast alloy after melting was carried out with a Φ0.8 flat bottom hole and -12dB acceptance. The final ingot diameter was about 720mm, and then the riser and ingot tail were cut off.

[0067] Step 3, using a resistance furnace, heat the ingot to 1150℃ in the single-phase region for homogenization treatment, and then use a fast forging machine to upset and draw, quickly upsetting and drawing, with a deformation amount of 40% and a deformation speed of 40mm / s. The initial forging temperature is ≥1000℃, and the final forging temperature is ≥900℃.

[0068] Step 4: Use a resistance furnace to heat the ingot to 1020°C in the α+β two-phase region, and use a fast forging machine or a hydraulic press to perform repeated upsetting and drawing forging, with a deformation amount of 55% and a deformation speed of 40 mm / s. The initial forging temperature is ≥900°C and the final forging temperature is ≥800°C.

[0069] Step 5, using a resistance furnace, heat the ingot to 920℃ in the α+β two-phase region, and use a fast forging machine for repeated upsetting and drawing forging. The 750mm*L forging billet is tempered twice along the axial direction to the 350mm*L forging billet in the square. After sawing and dividing, the forging billet is tempered twice by the square 300mm*L and drawn and rounded to obtain a 150mm*L forging billet. The single downward pressure deformation during the drawing period does not exceed 20mm, and the deformation rate is 20mm / s. The initial forging temperature is ≥800℃, and the final forging temperature is ≥700℃. Tempering is allowed for each fire, and the upsetting deformation is controlled for each fire. When forging defects such as cracking and pinching occur, the forging should be stopped immediately, and the forging should be continued after grinding and removing the damage; grinding between fires can be reduced according to the surface state of the billet, and two fires are allowed to be produced continuously when the surface is good.

[0070] Step 6, using a resistance furnace, the ingot is heated to 950°C, and the forming method is to grind the forging blank after 15 passes from Ф150mm→Ф60mm, and then grind the Ф60mm bar blank after turning (single side 0.4-0.5mm) and grinding, and then perform secondary rolling from Ф60mm→Ф24, Ф22mm through 15 passes, and the deformation of each pass is ≤10%.

[0071] Step 7, heat treatment of the titanium alloy hot-forged rod, the heat treatment method is solution treatment, the temperature is 980°C, the heating rate is 10°C / min, and the holding time is 240min; after the heat treatment, oil cooling is reduced to room temperature, and then artificial aging treatment is performed at 720°C for 8h and air cooling is performed to room temperature.

[0072] Embodiment 2:

[0073] Step 1, titanium is added in the form of small-grained 0a-grade sponge titanium, zirconium is added in the form of sponge zirconium, aluminum is added in the form of master alloy and high-purity aluminum, tin is added in the form of high-purity Ti-Sn master alloy, molybdenum is added in the form of Al-Mo master alloy, silicon is added in the form of Al-Si master alloy, tungsten is added in the form of Al-W master alloy, and carbon is added in the form of carbon powder. Yttrium uses high-purity yttrium, and the remaining elements are added in the form of master alloy, according to the ingredients of 5.8wt.% aluminum, 4wt.% tin, 3.5wt.% zirconium, 0.5wt.% molybdenum, 1wt.% tungsten, 0.3wt.% niobium, 1wt.% yttrium, 0.5wt.% silicon, 0.05wt.% carbon, and the balance is titanium. The configured alloy is mechanically mixed in a mixer for 2 hours to ensure that it is evenly mixed.

[0074] Step 2: Press the mixed raw materials into electrode blocks, stack and weld the electrode blocks into consumable electrodes using a vacuum plasma welding box. The density of the electrode blocks is 3.45-3.50 g / cm 3The alloy raw materials were repeatedly melted three times in a vacuum consumable electrode arc melting furnace. During the melting, the melting temperature was controlled at 1910℃-1930℃, the melting current was 24KA, the voltage was 35KV, and the pressure in the furnace during the last melting stabilization stage should not be greater than 5Pa. The ultrasonic flaw detection of the cast alloy after melting was carried out with a Φ0.8 flat bottom hole and -12dB acceptance. The final ingot diameter was about 720mm, and then the riser and ingot tail were cut off.

[0075] Step 3, using a resistance furnace, heat the ingot to 1150℃ in the single-phase region for homogenization treatment, and then use a fast forging machine to upset and draw, quickly upsetting and drawing, with a deformation amount of 55% and a deformation speed of 50mm / s. The initial forging temperature is ≥1000℃, and the final forging temperature is ≥900℃.

[0076] Step 4: Use a resistance furnace to heat the ingot to 1050°C in the α+β two-phase region, and use a fast forging machine or a hydraulic press to perform repeated upsetting and drawing forging, with a deformation amount of 50% and a deformation speed of 40mm / s. The initial forging temperature is ≥900°C, and the final forging temperature is ≥800°C.

[0077] Step 5: Use a resistance furnace to heat the ingot to 900°C in the α+β two-phase region, and use a fast forging machine to repeatedly upsetting and drawing forging. The 750mm*L forging billet is tempered twice and drawn along the axial direction to a 350mm*L forging billet in a square. After sawing and dividing, the forging billet is tempered twice and drawn and rounded from a 300mm*L forging billet in a square to obtain a 150mm*L forging billet. The single downward deformation during the drawing period does not exceed 20mm, and the deformation rate is 25mm / s. The initial forging temperature is ≥800°C, and the final forging temperature is ≥700°C.

[0078] Step 6, use a resistance furnace to heat the ingot to 900°C, roll the forging blank from 150mm to 60mm for 16 passes and then grind it, and roll the 60mm bar blank for a second time from 60mm to 24 and 22mm through 20 passes, with deformation of each pass ≤8%.

[0079] Step 7, heat treating the titanium alloy hot-forged rod, wherein the heat treatment method is solution treatment, the temperature is 950°C, the heating rate is 10°C / min, and the holding time is 480min; after the heat treatment, air-cooling to room temperature, then keeping at 930°C for 30min and then air-cooling to room temperature, and then artificially aging treatment at 700°C for 10h and air-cooling to room temperature.

[0080] Comparative Example 1:

[0081] The titanium alloy in this comparative example is TC4 titanium alloy.

[0082] Comparative Example 2:

[0083] The only difference between the preparation method of the titanium alloy in this comparative example and that in Example 2 is that no Y element is added.

[0084] Comparative Example 3:

[0085] The only difference between the preparation method of the titanium alloy in this comparative example and that in Example 2 is that no Si element is added.

[0086] Comparative Example 4:

[0087] The only difference between the preparation method of the titanium alloy in this comparative example and that in Example 2 is the following steps:

[0088] Step 3, using a resistance furnace, heat the ingot to 1150℃ in the single-phase region for homogenization treatment, and then use a fast forging machine to upset and draw, quickly upsetting and drawing, with a deformation amount of 35% and a deformation speed of 50mm / s. The initial forging temperature is ≥1000℃, and the final forging temperature is ≥900℃.

[0089] Step 4: Use a resistance furnace to heat the ingot to 1050°C in the α+β two-phase region, and use a fast forging machine or a hydraulic press to perform repeated upsetting and drawing forging, with a deformation amount of 35% and a deformation speed of 40mm / s. The initial forging temperature is ≥900°C, and the final forging temperature is ≥800°C.

[0090] Step 6, use a resistance furnace to heat the ingot to 900°C, roll the forging blank from 150mm to 60mm for 16 passes and then grind it, and roll the 60mm bar blank for a second time from 60mm to 24 and 22mm for 30 passes, with deformation of each pass ≤4%.

[0091] Comparative Example 5:

[0092] The only difference between the preparation method of the titanium alloy in this comparative example and that in Example 2 is that the cast state is not deformed or heat treated, and steps 3-7 are omitted.

[0093] Figure 1 This is a 200-fold metallographic image of the titanium alloy obtained in Example 1. Figure 2 This is a 500-fold metallographic 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 mainly composed of a three-state structure, with two sizes of primary α phase and a thin lath-like secondary α phase.

[0094] Figure 3 This is a 200-fold metallographic image of the titanium alloy obtained in Example 2. Figure 4 This is a 500-fold metallographic image of the titanium alloy obtained in Example 2. Figure 3 and Figure 4It can be seen that the titanium alloy prepared in Example 2 is mainly composed of a three-state structure, with the presence of a primary α phase and secondary α phases of coarse and fine laths.

[0095] In order to evaluate the hydrogen embrittlement sensitivity of titanium alloy, a slow tensile rate test (SSRT) was used. The electrochemical cathode hydrogenation method was used for hydrogenation. The hydrogenation solution consisted of a mixed solution of 0.5 M sulfuric acid and 3 g / L thiourea. The hydrogenation process lasted for 24 hours with a current density of 50 mA / cm 2 After the hydrogen filling was completed, the tensile test was carried out immediately. The tensile rate of all tensile tests was 1×10- 5 s-1. Figure 5 The fracture morphology of Example 2 after hydrogen filling and stretching is shown. It can be observed that no hydrogen embrittlement occurs, and the fracture edge shows a fracture feature of a combination of tearing edges and dimples, and no hydrogen-induced embrittlement region is formed.

[0096] According to GB / T 39039-2020, the tensile strength and elongation of the titanium alloys prepared in the examples and comparative examples before and after electrochemical cathode hydrogen charging were tested by constant load tensile test. The results are shown in Table 1:

[0097] Table 1 Mechanical tensile properties of titanium alloy before and after hydrogen charging in the examples and comparative examples

[0098]

[0099] The above is only a preferred embodiment of the present invention and does not limit the present invention in any form. Therefore, any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the scope of protection of the technical solution of the present invention.

Claims

1. A high-strength titanium alloy resistant to hydrogen embrittlement, characterized in that: It contains the following components by mass content: 5.5-6.5% aluminum, 3.5-4.5% tin, 3.2-3.8% zirconium, 0.4-0.6% molybdenum, 0.7-1.2% tungsten, 0.25-0.35% niobium, 0.4-0.6% silicon, 0.8-1.2% yttrium, 0.03-0.08% carbon, and the balance is titanium element and unavoidable impurities; The hydrogen embrittlement resistant high-strength titanium alloy is prepared by the following steps: after the smelted cast alloy billet is opened, forging and heat treatment are performed; The forging includes: reforming forging at 1020-1050°C, reforming forging and forming at 860-940°C, and rolling forming at 900-950°C.

2. The hydrogen embrittlement resistant high-strength titanium alloy according to claim 1, characterized in that: It contains the following components by mass content: 5.8% aluminum, 4% tin, 3.5% zirconium, 0.5% molybdenum, 1% tungsten, 0.3% niobium, 0.5% silicon, 1% yttrium, 0.05% carbon, and the balance is titanium element and inevitable impurities.

3. A method for preparing the hydrogen embrittlement resistant high-strength titanium alloy according to claim 1 or 2, characterized in that: The steps include: S1, mixing alloy raw materials, pressing them into electrode blocks, making the electrode blocks into consumable electrodes, and smelting them to obtain cast alloy billets; S2, forging the as-cast alloy billet after billet opening to obtain a titanium alloy bar; S3. The forged titanium alloy rod is heat treated to obtain a hydrogen embrittlement-resistant high-strength titanium alloy rod.

4. The preparation method according to claim 3, characterized in that: In S1, titanium is added in the form of sponge titanium, zirconium is added in the form of sponge zirconium, aluminum is added in the form of master alloy and high-purity aluminum, tin is added in the form of high-purity Ti-Sn master alloy, molybdenum is added in the form of Al-Mo master alloy, silicon is added in the form of Al-Si master alloy, tungsten is added in the form of Al-W master alloy, and carbon is added in the form of carbon powder.

5. The preparation method according to claim 3, characterized in that: In S1, a vacuum consumable electrode arc melting furnace is used to repeatedly melt the alloy raw materials three times, and the melting temperature is controlled at 1910°C to 1930°C.

6. The preparation method according to claim 3, characterized in that: The blanking treatment in S2 includes: heating the as-cast alloy blank to 1150-1200° C. for homogenization treatment, and then hot forging the blank.

7. The preparation method according to claim 6, characterized in that: The hot forging blanking deformation amount is not less than 40%.

8. The preparation method according to claim 3, characterized in that: The forging in S2 includes, in sequence: 1) Forging at 1020-1050℃, repeated upsetting and drawing forging, with deformation not less than 50%; 2) Forging and forming at 860-940℃, repeated upsetting and drawing forging, and the single pressing deformation during the drawing period does not exceed 20mm; 3) Perform multiple rolling processes at 900-950°C, with the deformation of each process being ≤10%.

9. The preparation method according to claim 3, characterized in that: The heat treatment in S3 is first solution treatment and then artificial aging treatment.

10. The preparation method according to claim 9, characterized in that: The temperature of the solution treatment is 900-1025°C, and the temperature of the artificial aging treatment is 550-720°C.

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