An ordered phase strengthened titanium alloy ring forging and a method for manufacturing the same

Abstract

The application discloses an ordered phase reinforced titanium alloy ring forging and a preparation method thereof, and belongs to the technical field of titanium and titanium alloy processing. The preparation method comprises the following steps: performing primary upsetting on a bar material blank of titanium alloy to obtain a rough forging blank; performing secondary upsetting on the rough forging blank to obtain a fine forging blank; performing primary isothermal die forging on the fine forging blank to obtain a die forging blank; performing secondary isothermal die forging on the die forging blank to obtain an intermediate blank; sequentially performing recrystallization annealing treatment, punching and wire cutting on the intermediate blank to obtain a ring blank; performing radial-axial bidirectional isothermal ring rolling on the ring blank to obtain a ring-shaped forging; and performing solid solution aging treatment on the ring-shaped forging to obtain a ring forging. In the primary upsetting, the secondary upsetting, the primary isothermal die forging and the secondary isothermal die forging, the temperature is sequentially and continuously reduced in steps, the single deformation amount decreases in a decreasing trend with the temperature reduction, and the deformation rate is synchronously reduced with the temperature reduction. The preparation method of the ring forging can take into account the high-temperature performance advantage and the processing formability.

Description

Technical Field

[0001] This invention belongs to the field of titanium and titanium alloy processing technology, specifically relating to an ordered phase reinforced titanium alloy ring forging and its preparation method. Background Technology

[0002] As aero-engines develop towards higher thrust-to-weight ratios, lighter weight, and longer lifespans, annular high-temperature titanium alloy components (such as compressor casings and load-bearing rings) play a crucial role in improving the overall thrust-to-weight ratio and reducing weight. Novel titanium alloys reinforced with Ti-Al-Sn ternary ordered phases such as Ti8AlSn and Ti4AlSn2, as an emerging material system, have become one of the important materials for overcoming the performance bottlenecks of traditional materials and improving the overall thrust-to-weight ratio of aero-engines due to their excellent high-temperature strength and creep resistance.

[0003] However, the microstructure of this type of material is dominated by a titanium matrix with some novel ordered phases dispersed throughout. While this unique microstructure significantly improves the material's high-temperature resistance and thermal stability, it also introduces severe challenges in hot working. First, the ordered phase is characterized by high intrinsic brittleness and few slip systems, resulting in a decrease in the overall plasticity and an increase in brittleness compared to conventional titanium alloys. Second, during the forming process of ring forgings, the billet is highly susceptible to microcrack propagation and even cracking due to localized stress concentration during severe deformation or punching. Furthermore, because the ordered phase is sensitive to thermal history, if traditional processes do not fully consider its narrow processing window, excessively rapid deformation rates can easily lead to internal overheating and grain coarsening, while drastic cooling methods can result in excessive residual stress, further exacerbating the risk of brittle fracture and ultimately causing low yield.

[0004] Existing ring forging techniques are typically designed based on the mechanical behavior of conventional titanium alloys, making them ill-suited to the characteristics of these ordered-phase-reinforced materials. Therefore, developing a dedicated ring forging process that balances high-temperature performance advantages with machinability is of significant practical importance for promoting the engineering application of these high-performance novel titanium alloys in the aerospace field. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the present invention aims to provide an ordered phase reinforced titanium alloy ring forging and its preparation method, which can take into account both high-temperature performance advantages and machinability.

[0006] To achieve the above objectives, the present invention employs the following technical solution: This invention provides a method for preparing ordered phase reinforced titanium alloy ring forgings, comprising the following steps: The titanium alloy bar billet is forged once to obtain the rough forged billet; The rough-forged billet is forged a second time to obtain the fine-forged billet; The precision-forged billet is subjected to one isothermal die forging to obtain a die-forged billet; The forged billet is subjected to secondary isothermal forging to obtain an intermediate billet; The intermediate billet was subjected to recrystallization annealing, punching and wire cutting in sequence to obtain a ring billet; The ring billet is subjected to radial-axial bidirectional isothermal ring rolling to obtain a ring forging; The ring forging is obtained by solution aging treatment. In the processes of primary forging, secondary forging, primary isothermal forging, and secondary isothermal forging, the temperature decreases in a continuous stepwise manner, the amount of deformation per instance decreases with decreasing temperature, and the deformation rate decreases synchronously with decreasing temperature.

[0007] In one embodiment, the ordered phase-reinforced titanium alloy ring forging is composed of the following components by mass percentage: Al 4%~20%, Sn 4%~35%, and small amounts of Nb, W, Si, C, Zr, Mo, and B elements, wherein the content of W is ≤10%, the content of Nb, Si, C, Zr, Mo, and B is ≤4%, and the balance is Ti and unavoidable impurity elements.

[0008] In one embodiment, the primary forging specifically refers to: The titanium alloy bar billet is heated to 5-25 ℃ below the β phase transformation point of the titanium alloy, held for 1-2 h, and then subjected to 1-4 upsetting and drawing deformations. The deformation amount of each upsetting is not less than 40%, and the upsetting reduction rate is controlled between 5-15 mm / s. During upsetting, the surface of the titanium alloy bar billet is covered with heat-insulating material.

[0009] In one embodiment, the secondary forging specifically refers to: The forged billet is heated to 30-50 °C below the β phase transformation point of the titanium alloy and held for 1-2 h. Then, it is upset and drawn in 1-3 heats. The amount of upsetting deformation in a single heat is not less than 35%, and the upsetting reduction rate is between 3-12 mm / s. During upsetting, the surface of the forged billet is covered with heat-insulating material.

[0010] In one embodiment, the single isothermal forging specifically comprises: The forged billet is heated to a temperature of 55-75°C below the β-phase transformation point of the titanium alloy. The die is heated to the billet temperature or within 80°C below the billet temperature. Isothermal forging is performed in 1-3 cycles. The surface of the forged billet is uniformly sprayed with heat-insulating lubricant. The single pressing amount is controlled at 25%-35% of the initial height of the forged billet, and the pressing rate is between 0.5-5 mm / s.

[0011] In one embodiment, the secondary isothermal forging specifically comprises: The forging billet is heated to a temperature 80-100°C below the β-phase transformation point of the titanium alloy. The die is heated to the forging billet temperature or 80°C below the forging billet temperature. Isothermal forging is performed in 1-3 cycles. The surface of the forging billet is uniformly sprayed with heat-insulating lubricant. The single pressing amount is controlled at 18%-25% of the initial height of the billet, and the pressing rate is between 0.5-5 mm / s.

[0012] In one embodiment, the recrystallization annealing process is carried out at a temperature of 700-850 °C for 1.5 h, and the cooling method is air cooling or furnace cooling.

[0013] In one embodiment, the radial-axial bidirectional isothermal ring rolling specifically involves: The ring billet is heated to a temperature 80-120°C below the β-phase transformation point of the titanium alloy. The drive roll, core roll, and guide roll are heated to the ring billet temperature or within 50°C of the ring billet temperature. The linear speed of the drive roll is controlled at 0.5-1.2 m / s, and the feed speed of the core roll is controlled at 0.1-0.3 mm / r. The total radial deformation is 60%-75%, completed in 3-4 passes. The radial deformation per pass is controlled between 15%-25%, and the axial deformation is 20%-30%. Before rolling, the ring billet is coated with a glass-based lubricant. After ring rolling, it is furnace cooled to 500-800°C and then air cooled.

[0014] In one embodiment, in the solution aging treatment, the solution temperature is 5~30°C below the β phase transformation point of the titanium alloy, the holding time is calculated based on the maximum thickness of the ring forging, and the holding time is 0.5~1.0 h for every 50 mm thickness, and the cooling method is air cooling or air cooling; the aging temperature is 550~800°C, the holding time is 10~20 h, and the cooling method is air cooling.

[0015] The present invention also provides a method for preparing ordered phase reinforced titanium alloy ring forgings, wherein the microstructure of the ordered phase reinforced titanium alloy ring forgings comprises Ti-Al-Sn ternary ordered phases, wherein the Ti-Al-Sn ternary ordered phases are Ti8AlSn phase and / or Ti4AlSn2 phase.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention proposes a method for preparing ordered phase-reinforced titanium alloy ring forgings. Addressing the technical challenges of the inherent brittleness of ordered phases and their susceptibility to cracking during hot working, this invention employs a "multi-stage isothermal + low-speed deformation" processing strategy. This leverages the high-temperature plasticity of the titanium matrix for coordinated deformation while effectively avoiding surface hardening and localized stress concentration in the billet caused by rapid die cooling. This significantly reduces the cracking sensitivity of the billet during upsetting and die forging, ensuring the forming stability during hot working. Furthermore, this invention utilizes a radial-axial bidirectional ring rolling process combined with intermediate recrystallization annealing to promote the uniform dispersion of the TiAlSn ordered phase within the titanium matrix. This effectively eliminates defects such as incomplete forging and microstructure segregation in the ring core, ensuring continuous closure of the metal flow lines along the circumference of the ring forging. This significantly improves the uniformity, density, dimensional accuracy, and isotropy of the microstructure of the ring. Meanwhile, this invention, through customized solution aging and slow cooling processes, can precisely control the dissolution and precipitation behavior of ordered phases. While preserving the excellent high-temperature strength of titanium alloy ring forgings, it fully releases the residual stress inside the material, avoids microcrack defects induced by rapid cooling, and ultimately achieves the best match between the strength and toughness of the ring forgings, ensuring that the finished product can stably meet the stringent requirements of aerospace applications for the comprehensive mechanical properties of materials.

[0017] Furthermore, this invention synergistically limits the temperature, deformation amount, and deformation rate of primary forging, secondary forging, primary isothermal forging, and secondary isothermal forging. When the primary forging temperature is higher than the specified range, it easily leads to β-grain growth, weakening the subsequent microstructure refinement effect and potentially causing non-uniform precipitation of ordered or second-phase phases; when the temperature is lower than the specified range, the billet deformation resistance increases, thermoplasticity decreases, and the risk of cracking increases. When the single upsetting deformation amount is lower than the lower limit, core deformation penetration is insufficient, and the improvement in microstructure uniformity is limited. When the secondary forging temperature is higher than the specified range, the tendency for grain growth is enhanced, and the microstructure refinement effect is reduced; when the temperature is lower than the specified range, the material plasticity reserve is insufficient, and the sensitivity to deformation cracking increases. During isothermal forging, when the deformation rate is too high, the risk of local stress concentration and interface damage increases; when the deformation rate is too low, the high-temperature residence time is prolonged, which may lead to grain or ordered phase coarsening. When the primary forging pressure is less than 25%, forming and microstructure refinement are insufficient; when it is higher than 35%, the drum-shaped effect and circumferential tensile stress increase. When the amount of pressure applied during secondary forging is less than 18%, the finishing effect is insufficient; when it is more than 25%, the risk of microcracks increases due to the reduced plasticity reserve of the billet.

[0018] Furthermore, this invention provides synergistic control of recrystallization annealing and radial-axial bidirectional isothermal ring rolling parameters. When the recrystallization annealing temperature is below 700°C, the deformation structure recovery and recrystallization are insufficient, the billet plasticity recovery is inadequate, and the risk of subsequent ring rolling cracking increases. When the temperature is above 850°C, the tendency for grain growth is enhanced, which is not conducive to obtaining a fine and uniform structure. When the ring rolling temperature is above the aforementioned range, the risk of grain and ordered phase coarsening increases, which may reduce the high-temperature strength and microstructure uniformity of the ring. When the temperature is below the aforementioned range, the matrix thermoplasticity is insufficient, and rolling cracks are prone to occur on the end face, inner wall, and local stress concentration areas. When the total radial deformation is insufficient, the core deformation is insufficient, making it difficult to effectively improve microstructure segregation and compactness. When the total radial deformation is too large, the risk of interface damage, micropore aggregation, and microcrack formation increases. When the radial deformation in a single pass is too large, local stress concentration is aggravated, which can easily lead to microstructure inhomogeneity or interface debonding. When the mandrel feed speed is too fast, the deformation temperature rise and local strain unevenness increase, disrupting the isothermal deformation conditions; when the feed speed is too slow, the high-temperature residence time is prolonged, which may cause grain or ordered phase coarsening and reduce production efficiency. When the final cooling temperature in the furnace after ring rolling is inappropriate, it is easy to cause insufficient release of residual stress or deviation of the ordered phase precipitation state from expectations, thereby affecting the microstructure stability and overall performance of the ring forging.

[0019] Furthermore, this invention precisely defines the solution aging parameters. When the solution temperature is above the specified range and approaches or enters the β single-phase region, it easily causes significant growth of β grains and may lead to non-uniform precipitation of subsequent ordered or second-phase phases, reducing plasticity and microstructure uniformity. When the solution temperature is below the specified range, the dissolution of ordered phases and microstructure adjustment are insufficient, making it difficult to fully utilize the subsequent aging strengthening effect. When the solution cooling rate is too slow, pre-precipitation or coarsening of precipitated phases easily occurs, weakening the aging strengthening effect. When the cooling rate is too fast, residual stress increases, and the risk of microcracks increases. When the aging temperature is below 550℃, precipitation motive is insufficient, and the strengthening phase precipitation is incomplete. When the aging temperature is above 800℃, the tendency for coarsening of precipitated phases increases, and the strength stability decreases. When the aging time is insufficient, the amount of ordered phase precipitation is insufficient, and the strengthening effect is limited. When the aging time is too long, over-aging easily occurs, leading to strength decay. Therefore, the process parameters in this invention have a synergistic coupling relationship. When the parameters are under boundary conditions, they need to be matched and adjusted in combination with temperature, deformation amount, deformation rate and heat treatment regime to maintain the stability of the structure, the dispersion of the ordered phase and the comprehensive mechanical properties of the ring forging. Attached Figure Description

[0020] Figure 1 Here is a high-magnification image of the microstructure of the ring forging prepared in Example 1 under solution treatment and aging conditions; Figure 2 EBSD image of the ring forging prepared in Example 1; Figure 3 Here is a high-magnification image of the microstructure of the ring forging prepared in Example 2 under solution treatment and aging conditions; Figure 4 The image shown is an EBSD image of the ring forging prepared in Example 2. Detailed Implementation

[0021] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0022] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0023] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0024] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0025] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0026] This invention provides a novel method for preparing ordered phase-reinforced titanium alloy ring forgings, comprising the following steps: Step 1: Perform multiple rough forgings on the bar billet below the β phase transformation point; Step 2: Perform multiple precision forgings on the billet after rough forging in Step 1 at a lower temperature and a smaller deformation rate than in Step 1. Step 3: The billet after precision forging in Step 2 is initially formed by isothermal die forging at a lower temperature than in Step 2 with a larger downward pressure in the first stage. Step 4: The forging billet obtained in Step 3 is finished by isothermal forging in the second stage at a lower temperature than in Step 3, using a decreasing pressure method, to obtain an intermediate billet. Step 5: Perform recrystallization annealing on the intermediate billet obtained in step 4; Step 6: The recrystallized and annealed billet is punched and wire-cut to form a ring billet; Step 7: The ring billet is rolled into a ring forging by radial-axial bidirectional isothermal ring rolling at 80~120 ℃ below the β phase transformation point. The ring rolling adopts multi-pass radial deformation and axial deformation coordinated control. Step 8: The ring forging is subjected to solution aging treatment to obtain the ring forging.

[0027] The ordered phase-reinforced titanium alloy ring forging, by mass percentage, consists of the following components: Al 4%~20%, Sn 4%~35%, and small amounts of Nb, W, Si, C, Zr, Mo, and B elements, wherein the content of W is ≤10%, and the contents of Nb, Si, C, Zr, Mo, and B are all ≤4%, with the balance being Ti and unavoidable impurity elements; the microstructure of the ordered phase-reinforced titanium alloy ring forging comprises a Ti-Al-Sn ternary ordered phase, wherein the Ti-Al-Sn ternary ordered phase is Ti8AlSn phase and / or Ti4AlSn2 phase.

[0028] In step 1, the bar billet is heated to 5-25°C below the β phase transformation point of the alloy, held for 1-2 hours, and then subjected to 1-4 upsetting and drawing deformation cycles. The amount of deformation per upsetting cycle is not less than 40%, and the upsetting reduction rate is controlled between 5-15 mm / s. During upsetting, the surface of the billet is covered with heat-insulating material.

[0029] In step 2, the billet is heated to 30-50°C below the β phase transformation point, held for 1-2 hours, and then subjected to 1-3 upsetting and drawing deformation cycles. The deformation amount of a single upsetting cycle is not less than 35%, and the upsetting reduction rate is controlled between 3-12 mm / s. During upsetting, the surface of the billet is covered with heat-insulating material.

[0030] In step 3, the billet is heated to 55-75°C below the β phase transformation point, the die is heated to the billet temperature or below 80°C, and isothermal forging is performed 1-3 times. The surface of the billet is uniformly sprayed with heat-insulating lubricant, the single pressing amount is controlled at 25%-35% of the initial height of the billet, and the pressing rate is controlled between 0.5-5 mm / s.

[0031] In step 4, the billet is heated to 80-100°C below the β phase transformation point, the die is heated to the billet temperature or 80°C below it, and isothermal forging is performed 1-3 times. The surface of the billet is uniformly sprayed with heat-insulating lubricant, the single pressing amount is controlled at 18%-25% of the initial height of the billet, and the pressing rate is controlled between 0.5-5 mm / s.

[0032] In step 5, the recrystallization annealing temperature is 700~850 ℃, the holding time is 1.5 h, and the cooling method is air cooling or furnace cooling.

[0033] In step 7, the ring billet is heated to 80-120°C below the β phase transformation point. The drive roller, core roller, and guide roller are heated to the ring billet temperature or within 50°C below it. The linear speed of the drive roller is controlled at 0.5-1.2 m / s, the feed speed of the core roller is controlled at 0.1-0.3 mm / r, the total radial deformation is 60%-75%, and it is completed in 3-4 passes. The radial deformation per pass is controlled between 15%-25%, and the axial deformation is 20%-30%. Before rolling, a glass-based lubricant is applied to the ring billet. After ring rolling, it is furnace cooled to 500-800°C and then air cooled.

[0034] In step 8, the solution temperature is 5~30 ℃ below the β phase transformation point of the alloy, the holding time is calculated based on the maximum thickness of the forging, and the holding time is 0.5~1.0 h for every 50 mm thickness. The cooling method is air cooling or air cooling. The aging temperature is 550~800 ℃, the holding time is 10~20 h, and the cooling method is air cooling.

[0035] In one embodiment, a method for preparing an ordered phase-reinforced titanium alloy ring forging is proposed, comprising the following steps: Step 1: One-time forging of bar stock The bar billet is heated to 5-25 ℃ below the β phase transformation point and held for 1-2 h. It is then subjected to 1-4 upsetting and drawing deformation cycles, with a single upsetting deformation of not less than 40% and an upsetting reduction rate between 5-15 mm / s. The surface of the billet is covered with insulation material during upsetting.

[0036] Step 2: Secondary forging of bar stock The billet is then heated to 30-50 ℃ below the β phase transformation point and held for 1-2 h. It is then upset and drawn in 1-3 heats, with a single upset deformation amount of not less than 35% and an upset reduction rate between 3 and 12 mm / s. The billet surface is covered with insulation material during upset. After this step, the bar forging is completed.

[0037] Step 3: One-time die forging The billet is heated to 55-75°C below the β phase transformation point, and the die is heated to the billet temperature or within 80°C below it to perform 1-3 isothermal forging cycles. The surface of the billet is uniformly sprayed with heat-insulating lubricant. The single pressing amount is controlled at 25%-35% of the initial height of the billet, and the pressing rate is between 0.5-5 mm / s. After this step, a forged billet is obtained.

[0038] Step 4: Secondary forging The billet is heated to 80-100°C below the β phase transformation point, and the die is heated to the billet temperature or within 80°C below it to perform 1-3 isothermal forging cycles. The surface of the billet is uniformly sprayed with heat-insulating lubricant. The single pressing amount is controlled at 18%-25% of the initial height of the billet, and the pressing rate is between 0.5-5 mm / s. After this step, an intermediate billet is obtained.

[0039] Step 5: Intermediate heat treatment Before ring rolling, recrystallization annealing (700~850 ℃×1.5 h, air cooling or furnace cooling) is required to refine the deformed structure after die forging and restore plasticity.

[0040] Step 6: Punching and machining The intermediate billet is punched and wire-cut to obtain a ring billet.

[0041] Step 7: Ring rolling The ring billet is heated to 80~120 ℃ below the β phase transformation point and rolled in both radial and axial directions using a ring rolling mill. The radial and axial pairs of rolls are heated to the billet temperature or within 50 ℃ below it to perform isothermal ring rolling. Through the synergistic action of the drive roll, core roll, and guide roll, the wall thickness of the ring is reduced, the diameter is increased, and the height is precisely controlled to obtain a ring forging of fixed size.

[0042] The drive roller linear speed is 0.5~1.2 m / s, the core roller feed speed is 0.1~0.3 mm / r, the total radial deformation is 60~75% (divided into 3-4 passes, with the radial deformation per pass controlled between 15%~25%), and the axial deformation is 20~30%. Before rolling, a glass-based lubricant is applied to the ring billet, and after ring rolling, it is furnace cooled to 500~800 ℃ and then air cooled.

[0043] Step 8: Heat treatment after ring rolling The ring forging is subjected to solution aging treatment at a temperature 5-30 ℃ below the β phase transformation point. The holding time is calculated based on the maximum thickness of the forging, with a holding time of 0.5-1.0 h for every 50 mm of thickness. The cooling method is air cooling or air cooling, with an aging temperature of 550-800 ℃ and a holding time of 10-20 h, followed by air cooling to finally obtain the ring forging.

[0044] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0045] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0046] Example 1: Typical process for high Sn content alloys The chemical composition of the bar material selected in this embodiment, by mass percentage, is: Ti-6Al-8.5Sn-2.5W-0.5Si-0.05C, and its β phase transformation point was measured to be 1085℃ by metallographic method.

[0047] Step 1: One-time forging of bar stock The bar billet is heated to 15°C below the β phase transformation point (i.e., 1070°C), held for 1.5 h, and then subjected to upsetting and drawing deformation in 3 heats. The upsetting deformation amount in a single heat is 45%, and the upsetting reduction rate is controlled at 10 mm / s. The surface of the billet is covered with heat-insulating material during upsetting.

[0048] Step 2: Secondary forging of bar stock The billet is heated to 40°C below the β phase transformation point (i.e., 1045°C), held for 1.5 h, and then subjected to two upsetting and drawing deformations. The upsetting deformation amount in a single upsetting is 38%, and the upsetting reduction rate is controlled at 8 mm / s. During upsetting, the surface of the billet is covered with heat-insulating material. After this step, the bar forging is completed.

[0049] Step 3: One-time die forging The billet is heated to 65°C below the β phase transformation point (i.e., 1020°C), and the die is heated to the billet temperature (1020°C). Two-stage isothermal forging is performed. The surface of the billet is uniformly sprayed with heat-insulating lubricant. The single pressing amount is controlled at 30% of the initial height of the billet, and the pressing rate is controlled at 2 mm / s. After this step, a forged billet is obtained.

[0050] Step 4: Secondary forging The billet is heated to 90°C below the β phase transformation point (i.e., 995°C), and the die is heated to the billet temperature (995°C). Two-stage isothermal forging is performed. The surface of the billet is uniformly sprayed with heat-insulating lubricant. The single pressing amount is controlled at 22% of the initial height of the billet, and the pressing rate is controlled at 1.5 mm / s. After this step, an intermediate billet is obtained.

[0051] Step 5: Intermediate heat treatment Recrystallization annealing is performed before ring rolling: 750℃×1.5h, air cooling, to refine the deformed structure after die forging and restore plasticity.

[0052] Step 6: Punching and machining The intermediate billet is punched and wire-cut to obtain a ring billet.

[0053] Step 7: Ring rolling The ring billet is heated to 100°C below the β phase transformation point (i.e., 985°C), and the drive roll, mandrel, and guide roll are heated to the ring billet temperature (985°C). Isothermal ring rolling is performed in both radial and axial directions. The linear speed of the drive roll is controlled at 0.8 m / s, the feed speed of the mandrel is controlled at 0.2 mm / r, the total radial deformation is 68%, and it is completed in 4 passes (the radial deformation per pass is controlled at 17%~20%), and the axial deformation is 25%. Before rolling, a glass-based lubricant is applied to the ring billet, and after ring rolling, it is cooled to 630°C by furnace cooling and then air-cooled.

[0054] Step 8: Heat treatment after ring rolling The ring forging was subjected to solution aging treatment: the solution temperature was 20℃ below the β phase transformation point (i.e., 1065℃), the holding time was calculated based on the maximum thickness of the forging, with 0.5 h held for every 50 mm of thickness, and air cooling was used; the aging temperature was 650℃, the holding time was 12 h, and air cooling was performed to obtain the final ring forging. The microstructure of the final ring forging is as follows. Figure 1 As shown, it exhibits a uniform and fine equiaxed α+β dual-phase structure, without obvious coarse grains or metallurgical defects; EBSD orientation analysis is as follows. Figure 2 As shown, the grain orientation is randomly distributed with no significant preferred texture, and the overall structure is highly uniform. The tensile properties of the product are shown in Table 1. The room temperature tensile strength is about 1180 MPa, and the high temperature tensile strength at 650℃ is about 675 MPa. The difference between the inner and outer surface properties is small, and it has both high strength and good high temperature plasticity.

[0055] Table 1 Tensile properties of the ring forging in Example 1

[0056] Example 2: Typical process for alloys with higher Sn content The chemical composition of the rod material selected in this embodiment, by mass percentage, is: Ti 5Al The metallographic determination of 15Sn-2.5W-0.5Si-0.05C showed that its β-phase transformation point was 1130℃.

[0057] Step 1: One-time forging of bar stock The bar billet is heated to 10°C below the β phase transformation point (i.e., 1120°C), held for 1.5 h, and then subjected to upsetting and drawing deformation in 3 heats. The upsetting deformation in a single heat is 42%, and the upsetting reduction rate is controlled at 8 mm / s. The surface of the billet is covered with heat-insulating material during upsetting.

[0058] Step 2: Secondary forging of bar stock The billet is heated to 35°C below the β phase transformation point (i.e., 1095°C), held for 1.5 h, and then subjected to two upsetting and drawing deformations. The upsetting deformation amount in a single pass is 36%, and the upsetting reduction rate is controlled at 6 mm / s. During upsetting, the surface of the billet is covered with heat-insulating material. After this step, the bar forging is completed.

[0059] Step 3: One-time die forging The billet is heated to 60°C below the β phase transformation point (i.e., 1070°C), and the die is heated to the billet temperature (1070°C). Two-stage isothermal forging is performed. The surface of the billet is uniformly sprayed with heat-insulating lubricant. The single pressing amount is controlled at 28% of the initial height of the billet, and the pressing rate is controlled at 1.5 mm / s. After this step, a forged billet is obtained.

[0060] Step 4: Secondary forging The billet is heated to 85°C below the β phase transformation point (i.e., 1045°C), and the die is heated to the billet temperature (1045°C). Two-stage isothermal forging is performed. The surface of the billet is uniformly sprayed with heat-insulating lubricant. The single pressing amount is controlled at 20% of the initial height of the billet, and the pressing rate is controlled at 1.0 mm / s. After this step, an intermediate billet is obtained.

[0061] Step 5: Intermediate heat treatment Recrystallization annealing is performed before ring rolling: 780℃×1.5h, air cooling, to refine the deformed structure after die forging and restore plasticity.

[0062] Step 6: Punching and machining The intermediate billet is punched and wire-cut to obtain a ring billet.

[0063] Step 7: Ring rolling The ring billet is heated to 90°C below the β phase transformation point (i.e., 1040°C), and the drive roll, mandrel, and guide roll are heated to the ring billet temperature (1040°C). Isothermal ring rolling is performed in both radial and axial directions. The linear speed of the drive roll is controlled at 0.6 m / s (lower than in Example 1, to control the temperature rise and deformation rate), the feed speed of the mandrel is controlled at 0.15 mm / r, the total radial deformation is 65%, and it is completed in 4 passes (the radial deformation per pass is controlled at 15%~18%), and the axial deformation is 22%. Before rolling, a glass-based lubricant is applied to the ring billet, and after ring rolling, it is cooled to 650°C by furnace cooling and then air-cooled.

[0064] Step 8: Heat treatment after ring rolling The ring forging was subjected to solution aging treatment: the solution temperature was 15℃ below the β phase transformation point (i.e., 1115℃), the holding time was calculated based on the maximum thickness of the forging, with a holding time of 0.75 h for every 50 mm of thickness, and the cooling method was air cooling; the aging temperature was 600℃, the holding time was 14 h, and the ring was air cooled to obtain the final ring forging. The microstructure of the final ring forging is as follows: Figure 3 As shown, it exhibits an α+β dual-phase microstructure, free from metallurgical defects such as coarse grains, inclusions, and porosity; EBSD orientation analysis is as follows. Figure 4 As shown, the grain orientation is randomly distributed overall, with only slight deformation texture, and the overall structure is very uniform. The tensile properties of the product are shown in Table 2. The room temperature tensile strength is about 1220 MPa, and the high temperature tensile strength at 650℃ is about 700 MPa, which is a further improvement over the strength level of Example 1. Moreover, the difference between the inner and outer surface properties is small, showing excellent high temperature load-bearing capacity.

[0065] Table 2 Tensile properties of the ring forging in Example 2

[0066] Example 3: Applicability of low Al / Sn content alloys at low-end ring rolling temperatures The chemical composition of the material used in this embodiment, by mass percentage, is: Ti-5.0Al-4.0Sn-0.5W-0.4Si-0.04C, and its β phase transformation point, as measured by metallography, is 1040℃.

[0067] Step 1: One-time forging of bar stock The bar billet is heated to 15°C below the β phase transformation point, i.e., 1025°C, and held for 1.5 h. It is then subjected to three upsetting and drawing deformations, with a single upsetting deformation of 43% and an upsetting reduction rate of 8 mm / s. The surface of the billet is covered with insulation material.

[0068] Step 2: Secondary forging of bar stock The billet was heated to 40°C below the β phase transformation point, i.e. 1000°C, and held for 1.5 h. It was then subjected to two upsetting and drawing deformation processes. The upsetting deformation amount in a single process was 37%, and the upsetting reduction rate was 6 mm / s.

[0069] Step 3: One-time isothermal die forging The billet is heated to 65°C below the β phase transformation point, i.e., 975°C. The die is heated to 975°C, and two-stage isothermal forging is performed. The single-stage reduction is 29%, and the reduction rate is 1.5 mm / s.

[0070] Step 4: Secondary isothermal die forging The forging billet is heated to 90°C below the β phase transformation point, i.e., 950°C. The die is heated to 950°C, and two-stage isothermal forging is performed. The single-stage pressing amount is 21%, and the pressing rate is 1.0 mm / s.

[0071] Step 5: Intermediate heat treatment The intermediate billet was subjected to recrystallization annealing at 740℃ for 1.5 h followed by air cooling.

[0072] Step 6: Punching and wire cutting The intermediate billet is punched and wire-cut to obtain a ring billet.

[0073] Step 7: Radial-axial bidirectional isothermal ring rolling The ring billet is heated to 920°C, 120°C below the β phase transformation point. The drive roll, mandrel, and guide roll are also heated to 920°C for radial-axial bidirectional isothermal ring rolling. The drive roll linear speed is 0.6 m / s, the mandrel feed speed is 0.12 mm / r, and the total radial deformation is 62%, completed in 4 passes. The radial deformation per pass is 15%–16%, and the axial deformation is 22%. A glass-based lubricant is applied before rolling, and the ring is furnace cooled to 600°C after ring rolling, followed by air cooling.

[0074] Step 8: Solution treatment and aging The solution temperature is 20°C below the β phase transition point, i.e., 1020°C. The solution is held at this temperature for 0.5 h for every 50 mm thickness, followed by air cooling. Then, the solution is held at 620°C for 12 h, followed by air cooling.

[0075] The resulting ring forgings had a complete shape, with no through cracks on the inner and outer walls, and a relatively uniform α+β dual-phase microstructure. The tensile properties of the products are shown in Table 3. Since the ring rolling temperature in this embodiment was set at the lower end, the material deformation resistance was relatively high. However, by reducing the ring rolling feed speed and the number of passes for deformation, good microstructure continuity and dimensional integrity could still be obtained.

[0076] Table 3 Tensile properties of the ring forging in Example 3

[0077] Example 4: Suitability of medium Al / Sn content alloys at high-end solution temperatures The chemical composition of the material used in this embodiment, by mass percentage, is: Ti-6.5Al-6.5Sn-1.5W-0.3Si-0.05C, and its β phase transformation point, measured by metallographic method, is 1080℃.

[0078] Step 1: One-time forging of bar stock The bar billet was heated to 15°C below the β phase transformation point, i.e., 1065°C, and held for 1.5 h. It was then subjected to three upsetting and drawing deformations, with a single upsetting deformation of 44% and an upsetting reduction rate of 9 mm / s.

[0079] Step 2: Secondary forging of bar stock The billet was heated to 40°C below the β phase transformation point, i.e., 1040°C, and held for 1.5 h. It was then subjected to two upsetting and drawing deformations, with a single upsetting deformation of 37% and an upsetting reduction rate of 7 mm / s.

[0080] Step 3: One-time isothermal die forging The billet is heated to 65°C below the β phase transformation point, i.e., 1015°C. The die is heated to 1015°C, and two-stage isothermal forging is performed. The single-stage pressing amount is 30%, and the pressing rate is 1.8 mm / s.

[0081] Step 4: Secondary isothermal die forging The forging billet is heated to 90°C below the β phase transformation point, i.e., 990°C. The die is heated to 990°C, and two isothermal forging processes are performed. The single reduction amount is 22%, and the reduction rate is 1.2 mm / s.

[0082] Step 5: Intermediate heat treatment Recrystallization annealing was carried out at 760℃ for 1.5 h, followed by air cooling.

[0083] Step 6: Punching and wire cutting The intermediate billet is punched and wire-cut to obtain a ring billet.

[0084] Step 7: Radial-axial bidirectional isothermal ring rolling The ring billet is heated to 980°C, 100°C below the β-phase transformation point. The drive roll, mandrel, and guide roll are also heated to 980°C for radial-axial bidirectional isothermal ring rolling. The drive roll linear speed is 0.8 m / s, the mandrel feed speed is 0.18 mm / r, and the total radial deformation is 66%, completed in 4 passes. The radial deformation per pass is 16%–18%, and the axial deformation is 24%. After ring rolling, the billet is furnace cooled to 630°C and then air cooled.

[0085] Step 8: Solution treatment and aging The solution treatment temperature was set at the high end, 5°C below the β phase transition point, i.e., 1075°C. The solution was held at this temperature for 0.5 h for every 50 mm thickness, followed by air cooling. Then, the solution was held at 650°C for 12 h, followed by air cooling.

[0086] The resulting ring forgings exhibited a uniform microstructure without significant continuous growth of coarse β grains. The tensile properties of the products are shown in Table 4. Due to the solution temperature being close to the β phase transformation point, the reinforcing phase dissolved sufficiently, resulting in high strength after subsequent aging, but slightly lower plasticity.

[0087] Table 4 Tensile properties of the ring forging in Example 4

[0088] Comparative Example 1: The temperature was not decreased in a continuous stepwise manner, but rather increased in a stepwise manner. The chemical composition of the material used in this comparative example, by mass percentage, is: Ti-6Al-8.5Sn-2.5W-0.5Si-0.05C, and its β phase transformation point, as determined by metallographic method, is 1085℃.

[0089] This comparative example is basically the same as Example 1, except that the temperatures for the first forging, second forging, first isothermal forging, and second isothermal forging are not decreased in a continuous stepwise manner, but rather by a reverse stepwise heating regime: The primary forging temperature is 90°C below the β phase transformation point, i.e., 995°C. The secondary forging temperature is 65°C below the β phase transformation point, i.e., 1020°C; The temperature for one isothermal forging is 40°C below the β phase transformation point, i.e., 1045°C. The secondary isothermal forging temperature is 15°C below the β phase transformation point, i.e., 1070°C.

[0090] The remaining deformation amounts, deformation rates, ring rolling, and solution aging regimes are consistent with those in Example 1.

[0091] The tensile properties of the product are shown in Table 5. Due to the low temperature during the initial rough forging stage and the large upsetting deformation, the billet lacked thermoplasticity, resulting in fine cracks at the edges and in localized bulging areas. Although subsequent heated die forging reduced the deformation resistance, the microcracks formed in the early stage failed to heal completely and propagated along the local streamline direction during the subsequent ring rolling process. Ultimately, localized microcracks appeared on the inner wall and end face of the ring, the microstructure uniformity decreased, and the difference in surface properties between the inner and outer surfaces increased.

[0092] Table 5 Tensile properties of ring forgings in Comparative Example 1

[0093] Comparative Example 2: Deformation rate exceeds recommended range The chemical composition of the material used in this comparative example, by mass percentage, is: Ti-6Al-8.5Sn-2.5W-0.5Si-0.05C, and its β phase transformation point, as determined by metallographic method, is 1085℃.

[0094] This comparative example is basically the same as Example 1, except that the main thermal deformation rates all exceed the range recommended by this invention: The rate of rough pressing in a single forging upsetting process is increased to 20 mm / s; The rate of roughing reduction in secondary forging upsetting is increased to 18 mm / s; The reduction rate of isothermal die forging in one pass was increased to 8 mm / s; The reduction rate of secondary isothermal die forging was increased to 8 mm / s; During ring rolling, the core roll feed speed is increased to 0.5 mm / r.

[0095] The remaining temperature, deformation amount, and heat treatment regime are consistent with those in Example 1.

[0096] The tensile properties of the product are shown in Table 6. The excessively high deformation rate makes it difficult for the material to flow in a coordinated manner during isothermal deformation, and the local stress concentration is significantly enhanced. The excessively fast feed of the mandrel during the ring rolling stage leads to uneven strain distribution in the wall thickness direction, accompanied by local temperature rise and end face instability. The resulting ring part has many microcracks at the inner hole edge and end face area, and there are banded deformation structures in some areas. The plasticity and high-temperature elongation are significantly reduced.

[0097] Table 6 Tensile properties of ring forgings in Comparative Example 2

[0098] In summary, to address the challenges posed by the ordered phase structure, such as high intrinsic brittleness, easy cracking during ring forging, and drastic temperature drop, a manufacturing process based on multi-stage temperature gradient control and isothermal deformation control is provided. This process mitigates temperature drop by setting multi-stage gradually decreasing temperature ranges, combined with appropriate deformation rates and insulation material coverage; it introduces radial-axial bidirectional isothermal ring rolling, coupled with glass-based lubricants and roll temperature control; and it incorporates recrystallization annealing and specific furnace cooling processes between key steps. This invention effectively suppresses internal hole cracking and surface oxidation defects during deformation, improves microstructure uniformity, coordinates high strength and ductility, and enhances the production stability and yield of this type of alloy ring forging.

[0099] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of this invention.

Claims

1. A method for preparing ordered phase reinforced titanium alloy ring forgings, characterized in that, Includes the following steps: The titanium alloy bar billet is forged once to obtain the rough forged billet; The rough-forged billet is forged a second time to obtain the fine-forged billet; The precision-forged billet is subjected to one isothermal die forging to obtain a die-forged billet; The forged billet is subjected to secondary isothermal forging to obtain an intermediate billet; The intermediate billet was subjected to recrystallization annealing, punching and wire cutting in sequence to obtain a ring billet; The ring billet is subjected to radial-axial bidirectional isothermal ring rolling to obtain a ring forging; The ring forging is obtained by solution aging treatment. In the processes of primary forging, secondary forging, primary isothermal forging, and secondary isothermal forging, the temperature decreases in a continuous stepwise manner, the amount of deformation per instance decreases with decreasing temperature, and the deformation rate decreases synchronously with decreasing temperature.

2. The method for preparing an ordered phase-reinforced titanium alloy ring forging according to claim 1, characterized in that, The ordered phase-reinforced titanium alloy ring forging is composed of the following components by mass percentage: Al 4%~20%, Sn 4%~35%, and small amounts of Nb, W, Si, C, Zr, Mo, and B elements, wherein the content of W is ≤10%, and the contents of Nb, Si, C, Zr, Mo, and B are all ≤4%, with the balance being Ti and unavoidable impurity elements.

3. The method for preparing an ordered phase-reinforced titanium alloy ring forging according to claim 1, characterized in that, The specific forging process is as follows: The titanium alloy bar billet is heated to 5-25 ℃ below the β phase transformation point of the titanium alloy, held for 1-2 h, and then subjected to 1-4 upsetting and drawing deformations. The deformation amount of each upsetting is not less than 40%, and the upsetting reduction rate is controlled between 5-15 mm / s. During upsetting, the surface of the titanium alloy bar billet is covered with heat-insulating material.

4. The method for preparing an ordered phase-reinforced titanium alloy ring forging according to claim 1, characterized in that, The secondary forging specifically refers to: The forged billet is heated to 30-50 °C below the β phase transformation point of the titanium alloy and held for 1-2 h. Then, it is upset and drawn in 1-3 heats. The amount of upsetting deformation in a single heat is not less than 35%, and the upsetting reduction rate is between 3-12 mm / s. During upsetting, the surface of the forged billet is covered with heat-insulating material.

5. The method for preparing an ordered phase-reinforced titanium alloy ring forging according to claim 1, characterized in that, The aforementioned isothermal die forging specifically refers to: The forged billet is heated to a temperature of 55-75°C below the β-phase transformation point of the titanium alloy. The die is heated to the billet temperature or within 80°C below the billet temperature. Isothermal forging is performed in 1-3 cycles. The surface of the forged billet is uniformly sprayed with heat-insulating lubricant. The single pressing amount is controlled at 25%-35% of the initial height of the forged billet, and the pressing rate is between 0.5-5 mm / s.

6. The method for preparing an ordered phase-reinforced titanium alloy ring forging according to claim 1, characterized in that, The secondary isothermal die forging specifically refers to: The forging billet is heated to a temperature 80-100°C below the β-phase transformation point of the titanium alloy. The die is heated to the forging billet temperature or 80°C below the forging billet temperature. Isothermal forging is performed in 1-3 cycles. The surface of the forging billet is uniformly sprayed with heat-insulating lubricant. The single pressing amount is controlled at 18%-25% of the initial height of the billet, and the pressing rate is between 0.5-5 mm / s.

7. A method for preparing an ordered phase-reinforced titanium alloy ring forging according to claim 1, characterized in that, In the recrystallization annealing process, the temperature is 700~850 ℃, the holding time is 1.5 h, and the cooling method is air cooling or furnace cooling.

8. The method for preparing an ordered phase-reinforced titanium alloy ring forging according to claim 1, characterized in that, The radial-axial bidirectional isothermal ring rolling specifically refers to: The ring billet is heated to a temperature 80-120°C below the β-phase transformation point of the titanium alloy. The drive roll, core roll, and guide roll are heated to the ring billet temperature or within 50°C of the ring billet temperature. The linear speed of the drive roll is controlled at 0.5-1.2 m / s, and the feed speed of the core roll is controlled at 0.1-0.3 mm / r. The total radial deformation is 60%-75%, completed in 3-4 passes. The radial deformation per pass is controlled between 15%-25%, and the axial deformation is 20%-30%. Before rolling, the ring billet is coated with a glass-based lubricant. After ring rolling, it is furnace cooled to 500-800°C and then air cooled.

9. A method for preparing an ordered phase-reinforced titanium alloy ring forging according to claim 1, characterized in that, In the solution aging treatment, the solution temperature is 5~30 ℃ below the β phase transformation point of the titanium alloy, the holding time is calculated based on the maximum thickness of the ring forging, and the holding time is 0.5~1.0 h for every 50 mm thickness, and the cooling method is air cooling or air cooling; the aging temperature is 550~800 ℃, the holding time is 10~20 h, and the cooling method is air cooling.

10. An ordered phase reinforced titanium alloy ring forging, characterized in that, The titanium alloy ring forging with ordered phase reinforcement is prepared by any one of claims 1 to 9. The microstructure of the titanium alloy ring forging with ordered phase reinforcement comprises a Ti-Al-Sn ternary ordered phase, wherein the Ti-Al-Sn ternary ordered phase is a Ti8AlSn phase and / or a Ti4AlSn2 phase.

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