A method for regulating the microstructure and properties of a near-β titanium alloy to achieve high strength and toughness matching

Abstract

The present invention relates to the technical field of non-ferrous metal materials, and particularly relates to a method for regulating the microstructure and properties of a near-β titanium alloy with high strength and toughness matching. The method includes the steps of: placing a near-β titanium alloy ingot at an initial forging temperature of 1100-1150°C for upsetting and drawing forging to obtain a first near-β titanium alloy forging blank; placing the first near-β titanium alloy forging blank at an initial forging temperature 120-150°C above the phase transformation point for upsetting and drawing forging to obtain a second near-β titanium alloy forging blank; placing the second near-β titanium alloy forging blank at an initial forging temperature 20-40°C below the phase transformation point for upsetting and drawing forging to obtain a third near-β titanium alloy forging blank; and placing the third near-β titanium alloy forging blank under set conditions for solution aging heat treatment to obtain a near-β titanium alloy material. The purpose of the method for regulating the microstructure and properties of the near-β titanium alloy with high strength and toughness matching is to solve the technical problem of how to achieve high strength and toughness matching of the near-β titanium alloy based on free forging thermomechanical treatment, and to achieve the effects of simplifying the process, shortening the cycle, and reducing the cost.

Description

Technical Field

[0001] The present invention relates to the technical field of non-ferrous metal materials, and particularly relates to a method for regulating the microstructure and properties of a near-β titanium alloy with high strength and toughness matching. Background Art

[0002] Near-β titanium alloys have a series of characteristics such as high specific strength, high specific stiffness, good heat treatment strengthening effect, large hardenability depth, and good hot and cold working properties, and are ideal materials for important load-bearing structures such as aircraft outer panels, frames, connectors, and fasteners. In recent years, under the guidance of design concepts such as lightweight, long life, and high reliability, the new generation of aircraft has put forward an urgent need for lightweight main load-bearing structural components with good comprehensive mechanical properties, and further requires near-β titanium alloys to have a good match of higher strength with plasticity and toughness, in order to achieve the goals of weight reduction, efficiency increase, and cost reduction through material lightweight and structural lightweight.

[0003] At present, the mechanical property regulation of near-β titanium alloys still follows the strength-plasticity / toughness inversion relationship, that is, the improvement of strength properties is often accompanied by a large decrease in plasticity and toughness. Taking the near-β titanium alloy Ti-55531 alloy (nominal composition: Ti-5Al-5Mo-5V-3Cr-1Zr), which has the highest strength level applied in aircraft at present, as an example, when its strength property increases to more than 1300 MPa, its fracture toughness property decreases to 40 MPa·m 1 / 2 Hereinafter, when its fracture toughness increases to more than 60 MPa·m 1 / 2 Above, its tensile strength property decreases to less than 1200 MPa, and this strength-toughness matching can no longer meet the urgent needs of the new generation of aircraft for lightweight load-bearing structural components with good comprehensive performance. In addition, the microstructure and property regulation of near-β titanium alloys based on free forging thermomechanical treatment requires a complex forging process of "multiple heats, large deformation" with gradually decreasing initial forging temperature to achieve the refinement of the microstructure grains and the morphology regulation of the precipitated phases, resulting in an increase in its preparation cycle and production cost.

[0004] Therefore, the inventor provides a method for regulating the microstructure and properties of a near-β titanium alloy with high strength and toughness matching. Summary of the Invention

[0005] (1) Technical Problems to be Solved

[0006] The embodiment of the present invention provides a method for regulating the microstructure and properties of a near-β titanium alloy with high strength and toughness matching, solves the technical problem of how to achieve high strength and toughness matching of near-β titanium alloys based on free forging thermomechanical treatment, and achieves the effects of simplifying the process, shortening the cycle, and reducing the cost.

[0007] (2) Technical Solutions

[0008] The present invention provides a method for regulating the microstructure and properties of a near-β titanium alloy with high strength and toughness matching, comprising the following steps:

[0009] Place the near-β titanium alloy ingot at an initial forging temperature of 1100 - 1150 °C for at least one pass of upsetting and drawing thermomechanical treatment. After each pass of forging, air cool to room temperature to obtain the first near-β titanium alloy forging blank;

[0010] Place the first near-β titanium alloy forging blank at an initial forging temperature 120 - 150 °C above the phase transformation point for at least one pass of upsetting and drawing thermomechanical treatment. After forging is completed, air cool to room temperature to obtain the second near-β titanium alloy forging blank;

[0011] Place the second near-β titanium alloy forging blank at an initial forging temperature 20 - 40 °C below the phase transformation point for at least one pass of upsetting and drawing thermomechanical treatment. After forging is completed, air cool to room temperature to obtain the third near-β titanium alloy forging blank;

[0012] Subject the third near-β titanium alloy forging blank to solution aging heat treatment under set conditions to obtain the near-β titanium alloy material.

[0013] Further, the step of placing the near-β titanium alloy ingot at an initial forging temperature of 1100 - 1150 °C for at least one pass of upsetting and drawing thermomechanical treatment is specifically as follows:

[0014] For each pass, adopt the process of two-upsetting and two-drawing with intermediate reverse drawing. The single-pass upsetting and drawing forging ratio is controlled between 1.5 and 2.5. After each pass of forging, air cool to room temperature respectively.

[0015] Further, the step of placing the first near-β titanium alloy forging blank at an initial forging temperature 120 - 150 °C above the phase transformation point for at least one pass of upsetting and drawing thermomechanical treatment is specifically as follows:

[0016] For each pass, adopt the process of two-upsetting and two-drawing with intermediate reverse drawing. The single-pass upsetting and drawing forging ratio is controlled between 1.5 and 2.5.

[0017] Further, when performing multi-pass upsetting and drawing thermomechanical treatment at an initial forging temperature 120 - 150 °C above the phase transformation point, after each pass of forging, air cool to room temperature respectively, then reheat and perform the next pass of forging at this temperature.

[0018] Further, when performing multi-pass upsetting and drawing thermomechanical treatment at an initial forging temperature 120 - 150 °C above the phase transformation point, after each pass of forging, directly return to the furnace for heat preservation and tempering. The heat preservation time is 90 - 120 min. After taking out of the furnace, continue with the subsequent thermomechanical treatment deformation until all passes of forging at this temperature are completed and then air cool to room temperature.

[0019] Further, subjecting the second near-β titanium alloy forging billet to upsetting and drawing forging thermo-mechanical treatment at an initial forging temperature 20-40°C below the phase transformation point specifically includes:

[0020] For each heat, a two-upsetting and two-drawing process with intermediate reverse drawing is adopted, and the upsetting and drawing forging ratio per single pass is controlled between 1.5 and 2.0.

[0021] Further, when subjecting to multi-heat upsetting and drawing forging thermo-mechanical treatment at an initial forging temperature 20-40°C below the phase transformation point, after each heat of forging is completed, it is air-cooled to room temperature, reheated, and then the next heat of forging at this temperature is carried out.

[0022] Further, when subjecting to multi-heat upsetting and drawing forging thermo-mechanical treatment at an initial forging temperature 20-40°C below the phase transformation point, after each heat of forging is completed, it is directly returned to the furnace for heat preservation for tempering, the heat preservation time is 60-90 min, and after being taken out of the furnace, subsequent thermo-mechanical treatment deformation is continued until all heats of forging at this temperature are completed and then air-cooled to room temperature.

[0023] Further, subjecting the third near-β titanium alloy forging billet to solution aging heat treatment under specific conditions to obtain a near-β titanium alloy material specifically includes:

[0024] Subjecting the third near-β titanium alloy forging billet to solution heat treatment with heat preservation for t+(30-60) min in a temperature range 15-55°C below the phase transformation point, and then air-cooling to room temperature; subsequently, subjecting to aging heat treatment with heat preservation for 6-10 h in a temperature range of 580-620°C, and after air-cooling to room temperature, the near-β titanium alloy material is obtained; where t is the time required for the sample to reach uniform temperature, obtained by multiplying the heating coefficient by the interface thickness or diameter of the sample, and the heating coefficient is taken as 0.5-0.8 min / mm.

[0025] Further, the near-β titanium alloy material has a microstructure feature with a grain size less than 10 μm, a globular α-phase content of 5-20% and macroscopically uniformly distributed along the grain boundaries, and fine needle-like secondary α-phase dispersedly distributed in the β-phase matrix.

[0026] (3) Beneficial effects

[0027] In summary, the present invention promotes the dynamic and static recrystallization of alloy materials by adding thermomechanical treatment in the low-temperature single-phase region, inhibits the excessive growth of grain size in the microstructure at higher temperatures, rapidly refines the grains of the alloy microstructure, and maintains the grain size less than 10 μm. By combining thermomechanical treatment in the high-temperature two-phase region with solution aging heat treatment and comprehensively regulating and optimizing the size and morphology of the precipitated phase, the primary α phase is spheroidized with a volume fraction of about 5-20%, and the secondary α phase is dispersed in the β-phase alloy matrix in the form of fine needles. Through the interaction between grain microstructure, precipitated phase, etc. and dislocations, a good match between the strength, plasticity and toughness of the alloy is achieved. In addition, by combining / canceling the forging thermomechanical treatment processes with similar initial forging temperatures in the traditional microstructure and property regulation path, and adding thermomechanical treatment in the low-temperature single-phase region and intermediate tempering process to accelerate the refinement of grain microstructure, the process flow and cycle of alloy microstructure and property regulation are simplified and shortened, and the uniformity of microstructure and property is improved by combining the intermediate reverse drawing process, thus achieving the effect of reducing the production cost of the alloy. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required to be used in the embodiments of the present invention. Obviously, the following described drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0029] Figure 1 is a schematic flow chart of a method for regulating the microstructure and properties of a near-β titanium alloy with high strength and toughness matching provided by an embodiment of the present invention;

[0030] Figure 2 is a schematic diagram of the microstructure characteristics of a near-β titanium alloy provided by Embodiment 1 of the present invention;

[0031] Figure 3 is a schematic diagram of the microstructure characteristics of a near-β titanium alloy provided by Embodiment 2 of the present invention;

[0032] Figure 4 is a schematic diagram of the microstructure characteristics of a near-β titanium alloy provided by Embodiment 3 of the present invention;

[0033] Figure 5 is a schematic diagram of the microstructure characteristics of a near-β titanium alloy provided by Embodiment 4 of the present invention;

[0034] Figure 6 is a schematic diagram of the microstructure characteristics of a near-β titanium alloy provided by Embodiment 5 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0035] The following further describes in detail the embodiments of the present invention in conjunction with the accompanying drawings and embodiments. The detailed descriptions and drawings of the following embodiments are used to exemplarily illustrate the principles of the present invention, but cannot be used to limit the scope of the present invention, that is, the present invention is not limited to the described embodiments.

[0036] It should be noted that, without conflict, the embodiments in this application and the features in the embodiments can be combined with each other. The following will describe this application in detail with reference to the accompanying drawings and embodiments.

[0037] Figure 1 is a schematic flow chart of a method for regulating the tissue properties of a near-β titanium alloy with high strength and toughness matching, as Figure 1 shown, the method may include the following steps:

[0038] S100: Place the near-β titanium alloy ingot at an initial forging temperature of 1100 - 1150 °C for at least one pass of upsetting and drawing forging thermo-mechanical treatment. After each pass of forging is completed, air-cool to room temperature to obtain the first near-β titanium alloy forging blank;

[0039] S200: Place the first near-β titanium alloy forging blank at an initial forging temperature 120 - 150 °C above the phase transformation point for at least one pass of upsetting and drawing forging thermo-mechanical treatment. After forging is completed, air-cool to room temperature to obtain the second near-β titanium alloy forging blank;

[0040] S300: Place the second near-β titanium alloy forging blank at an initial forging temperature 20 - 40 °C below the phase transformation point for at least one pass of upsetting and drawing forging thermo-mechanical treatment. After forging is completed, air-cool to room temperature to obtain the third near-β titanium alloy forging blank;

[0041] S400: Subject the third near-β titanium alloy forging blank to solution aging heat treatment under set conditions to obtain the near-β titanium alloy material.

[0042] In the above embodiment, adding thermo-mechanical treatment in the low-temperature single-phase region (i.e., 120 - 150 °C above the phase transformation point) promotes the dynamic and static recrystallization of the alloy material, inhibits the excessive growth of the tissue grains at higher temperatures, enables the rapid refinement of the alloy microstructure grains, and maintains the grain size less than 10 μm. Combining thermo-mechanical treatment in the high-temperature two-phase region (i.e., 20 - 40 °C below the phase transformation point) with solution aging heat treatment, comprehensively regulating and optimizing the size and morphology of the precipitated phases, makes the primary α phase spheroidized and the volume fraction is about 5 - 20%, and the secondary α phase is finely needle-shaped and dispersedly distributed in the β-phase alloy matrix. Through the interaction between the tissue grains, precipitated phases, etc. and dislocations, good matching of the strength, plasticity and toughness of the alloy is achieved.

[0043] By combining / canceling forging thermo-mechanical treatment processes with similar initial forging temperatures in the traditional organizational performance regulation path, and adding thermo-mechanical treatment in the low-temperature single-phase region and intermediate tempering process to accelerate the refinement of the organizational grains, the process flow and cycle of alloy organizational performance regulation are simplified and shortened. Combining with the intermediate reverse drawing process improves the uniformity of organizational performance, thus achieving the effect of reducing the production cost of the alloy.

[0044] The near-β titanium alloy material prepared based on the present invention has a microstructure feature with a grain size less than 10 μm, a globular α-phase content of 5-20% and a macroscopically uniform distribution along the grain boundaries, and fine needle-like secondary α-phases diffusely distributed in the β-phase matrix. The strength, plasticity and toughness properties of this near-β titanium alloy are matched, and compared with the near-β titanium alloy prepared by the existing "multi-fire, large deformation" forging process with gradually decreasing initial forging temperatures, it has been further improved and enhanced.

[0045] As an alternative implementation, in step S100, the near-β titanium alloy ingot is placed at an initial forging temperature of 1100-1150 °C for at least one fire of upsetting and drawing forging thermo-mechanical treatment, specifically: for each fire, the process of two-upsetting and two-drawing with intermediate reverse drawing is adopted, and the single-pass upsetting and drawing forging ratio is controlled between 1.5 and 2.5. After each fire of forging is completed, it is air-cooled to room temperature respectively.

[0046] Among them, the purpose of step S100 is to initially break the coarse organizational grains of the original ingot through thermo-mechanical treatment at a relatively high temperature in the single-phase region, and forge and press the organizational defects such as microscopic pores and looseness that may exist in the ingot.

[0047] As an alternative implementation, in step S200, the first near-β titanium alloy forging blank is placed at an initial forging temperature 120-150 °C above the phase transformation point for at least one fire of upsetting and drawing forging thermo-mechanical treatment, specifically: for each fire, the process of two-upsetting and two-drawing with intermediate reverse drawing is adopted, and the single-pass upsetting and drawing forging ratio is controlled between 1.5 and 2.5.

[0048] Among them, the purpose of step S200 is to promote the dynamic and static recrystallization of the alloy material through thermo-mechanical treatment in the low-temperature single-phase region, and inhibit the excessive growth of organizational grains at a relatively high temperature, so that the grains of the alloy microstructure are rapidly refined.

[0049] As an alternative implementation, in step S200, when performing multi-fire upsetting and drawing forging thermo-mechanical treatment at an initial forging temperature 120-150 °C above the phase transformation point, after each fire of forging is completed, it is air-cooled to room temperature respectively, and then reheated to perform the next fire of forging at this temperature.

[0050] As an alternative embodiment, in step S200, when multi-pass upsetting and drawing forging thermo-mechanical treatment is performed at an initial forging temperature of 120 - 150 °C above the phase transition point, after each pass of forging is completed, it is directly returned to the furnace for heat preservation and tempering. The heat preservation time is 90 - 120 min. After being taken out of the furnace, subsequent thermo-mechanical treatment deformation is continued until all forging passes at this temperature are completed and then air-cooled to room temperature.

[0051] It should be noted here that the above two low-temperature single-phase region upsetting and drawing forging thermo-mechanical treatments are two completely different deformation schemes that can be arbitrarily selected according to actual situations. One is that after each pass of upsetting and drawing forging thermo-mechanical treatment is completed, it is air-cooled to room temperature respectively, and then reheated to perform the next pass of deformation at this temperature; the other is that after each pass of upsetting and drawing forging thermo-mechanical treatment is completed, it is returned to the furnace for heat preservation and tempering, and after being taken out of the furnace, the next pass of deformation is continued until all forging passes at this temperature are completed and then air-cooled to room temperature.

[0052] As an alternative embodiment, in step S300, the second near-β titanium alloy forging billet is placed at an initial forging temperature of 20 - 40 °C below the phase transition point for at least one pass of upsetting and drawing forging thermo-mechanical treatment. Specifically: for each pass, a two-upsetting and two-drawing process with intermediate reverse drawing is adopted, and the single-pass upsetting and drawing forging ratio is controlled between 1.5 and 2.0.

[0053] Among them, the purpose of step S300 is to preliminarily regulate the size, morphology and distribution of the precipitated phase through high-temperature two-phase region thermo-mechanical treatment.

[0054] As an alternative embodiment, in step S300, when multi-pass upsetting and drawing forging thermo-mechanical treatment is performed at an initial forging temperature of 20 - 40 °C below the phase transition point, after each pass of forging is completed, it is air-cooled to room temperature respectively, and then reheated to perform the next pass of forging at this temperature.

[0055] As an alternative embodiment, in step S300, when multi-pass upsetting and drawing forging thermo-mechanical treatment is performed at an initial forging temperature of 20 - 40 °C below the phase transition point, after each pass of forging is completed, it is directly returned to the furnace for heat preservation and tempering. The heat preservation time is 60 - 90 min. After being taken out of the furnace, subsequent thermo-mechanical treatment deformation is continued until all forging passes at this temperature are completed and then air-cooled to room temperature.

[0056] It should be noted here that the above two high-temperature two-phase region upsetting and drawing forging thermo-mechanical treatments are two completely different deformation schemes that can be arbitrarily selected according to actual situations. One is that after each pass of upsetting and drawing forging thermo-mechanical treatment is completed, it is air-cooled to room temperature respectively, and then reheated to perform the next pass of deformation at this temperature; the other is that after each pass of upsetting and drawing forging thermo-mechanical treatment is completed, it is returned to the furnace for heat preservation and tempering, and after being taken out of the furnace, the next pass of deformation is continued until all forging passes at this temperature are completed and then air-cooled to room temperature.

[0057] As an alternative embodiment, in step S400, the near-β titanium alloy forging billet is subjected to solution aging heat treatment under set conditions to obtain a near-β titanium alloy material, specifically: the near-β titanium alloy forging billet is held at a temperature range of 15 - 55 °C below the phase transformation point for solution heat treatment for t+(30 - 60) min, and then air-cooled to room temperature; subsequently, it is held at a temperature range of 580 - 620 °C for aging heat treatment for 6 - 10 h, and after air-cooling to room temperature, a near-β titanium alloy material is obtained; where t is the time required for the sample to reach a uniform temperature, obtained by multiplying the heating coefficient by the cross-sectional thickness or diameter of the sample, and the heating coefficient is taken as 0.5 - 0.8 mm / min.

[0058] The purpose of step S400 is to further regulate the size, morphology, quantity, and distribution characteristics of the precipitated phases.

[0059] Example 1

[0060] (1) The Ti-55531 titanium alloy ingot obtained by triple vacuum consumable arc melting is subjected to 3-pass upsetting and drawing forging thermomechanical treatment at an initial forging temperature of 1150 °C. Each pass adopts the process of two-upsetting and two-drawing with intermediate reverse drawing. The single-pass upsetting and drawing forging ratio is controlled between 1.5 and 2.5. After forging, it is air-cooled to room temperature.

[0061] (2) The Ti-55531 titanium alloy forging billet obtained in step (1) is subjected to 3-pass upsetting and drawing forging thermomechanical treatment at an initial forging temperature of 130 °C above the phase transformation point. Each pass adopts the process of two-upsetting and two-drawing with intermediate reverse drawing. The single-pass upsetting and drawing forging ratio is controlled between 1.5 and 2.5. After forging, it is air-cooled to room temperature. Additionally, after each pass of forging, it can be directly returned to the furnace for heat preservation and tempering. The heat preservation time is 90 - 120 min. After taking out of the furnace, subsequent thermomechanical treatment deformation continues until all forging passes at this temperature are completed and then air-cooled to room temperature.

[0062] (3) The Ti-55531 alloy forging billet obtained in step (2) is subjected to 3-pass upsetting and drawing forging thermomechanical treatment at an initial forging temperature of 20 - 40 °C below the phase transformation point. Each pass adopts the process of two-upsetting and two-drawing with intermediate reverse drawing. The single-pass upsetting and drawing forging ratio is controlled between 1.5 and 2.0. After forging, it is air-cooled to room temperature. Additionally, after each pass of forging, it can be directly returned to the furnace for heat preservation and tempering. The heat preservation time is 60 - 90 min. After taking out of the furnace, subsequent thermomechanical treatment deformation continues until all forging passes at this temperature are completed and then air-cooled to room temperature.

[0063] (4) The Ti-55531 alloy forging billet obtained in step (3) is subjected to solution heat treatment at 35 °C below the phase transformation point for 45 min, and then air-cooled to room temperature. Subsequently, it is subjected to aging heat treatment at 600 °C for 8 h, and then air-cooled to room temperature.

[0064] After comprehensively regulating the microstructure and properties of Ti-55531 titanium alloy by the above thermomechanical treatment and heat treatment, a microstructure can be obtained with a grain size less than 10 μm, a globular α-phase content of 5-20% and a macroscopically uniform distribution along the grain boundaries, and fine needle-like secondary α-phase dispersedly distributed in the β-phase matrix (as Figure 2 shown), thereby enabling the alloy to achieve a good match of high strength and toughness, that is: tensile strength R m = 1387 MPa, yield strength R p0.2 = 1352 MPa, elongation after fracture A = 9.5%, fracture toughness K IC = 57 MPa·m 1 / 2 .

[0065] Example 2

[0066] (1) Place the Ti-55531 titanium alloy ingot obtained by triple vacuum consumable arc melting at an initial forging temperature of 1100 °C for two-pass upsetting and drawing forging thermomechanical treatment. For each pass, use the process of two-upsetting and two-drawing with intermediate reverse drawing. The upsetting and drawing forging ratio per single pass is controlled between 1.5 and 2.5. After forging, air-cool to room temperature.

[0067] (2) Place the Ti-55531 titanium alloy forging blank obtained in step (1) at an initial forging temperature 130 °C above the phase transformation point for two-pass upsetting and drawing forging thermomechanical treatment. For each pass, use the process of two-upsetting and two-drawing with intermediate reverse drawing. The upsetting and drawing forging ratio per single pass is controlled between 1.5 and 2.5. After forging, air-cool to room temperature. In addition, after each pass of forging, it can be directly returned to the furnace for heat preservation and tempering. The heat preservation time is 90-120 min. After taking out of the furnace, continue with subsequent thermomechanical treatment deformation until after all forging passes at this temperature are completed and then air-cool to room temperature.

[0068] (3) Place the Ti-55531 alloy forging blank obtained in step (2) at an initial forging temperature 20-40 °C below the phase transformation point for two-pass upsetting and drawing forging thermomechanical treatment. For each pass, use the process of two-upsetting and two-drawing with intermediate reverse drawing. The upsetting and drawing forging ratio per single pass is controlled between 1.5 and 2.0. After forging, air-cool to room temperature. In addition, after each pass of forging, it can be directly returned to the furnace for heat preservation and tempering. The heat preservation time is 60-90 min. After taking out of the furnace, continue with subsequent thermomechanical treatment deformation until after all forging passes at this temperature are completed and then air-cool to room temperature.

[0069] (4) Place the Ti-55531 alloy forging blank obtained in step (3) at 35 °C below the phase transformation point for solution heat treatment with heat preservation for 45 min, and then air-cool to room temperature. Subsequently, perform aging heat treatment with heat preservation at 600 °C for 8 h, and then air-cool to room temperature.

[0070] After comprehensively regulating the microstructure and properties of Ti-55531 titanium alloy through the above thermomechanical treatment and heat treatment, a microstructure can be obtained with a grain size less than 10 μm, a globular α-phase content of 5-20% and macroscopically uniform distribution along the grain boundaries, and fine needle-like secondary α-phase dispersedly distributed in the β-phase matrix (as Figure 3 shown), thereby enabling the alloy to achieve a good match of high strength and toughness, that is: R m = 1332 MPa, R p0.2 = 1316 MPa, A = 13.5%, K IC = 50 MPa·m 1 / 2 .

[0071] Example 3

[0072] This embodiment is a method for regulating the microstructure and properties of a Ti-55531 titanium alloy with a high strength and toughness match. The specific implementation steps are as follows:

[0073] (1) Place the Ti-55531 titanium alloy ingot obtained by triple vacuum consumable arc melting at an initial forging temperature of 1150 °C for one-pass upsetting and drawing forging thermomechanical treatment. For each pass, use the process of two-upsetting and two-drawing with intermediate reverse drawing. The single-pass upsetting and drawing forging ratio is controlled between 1.5 and 2.5. After forging, air-cool to room temperature.

[0074] (2) Place the Ti-55531 titanium alloy forging blank obtained in step (1) at an initial forging temperature 150 °C above the phase transformation point for one-pass upsetting and drawing forging thermomechanical treatment. For each pass, use the process of two-upsetting and two-drawing with intermediate reverse drawing. The single-pass upsetting and drawing forging ratio is controlled between 1.5 and 2.5. After forging, air-cool to room temperature.

[0075] (3) Place the Ti-55531 alloy forging blank obtained in step (2) at an initial forging temperature 20-40 °C below the phase transformation point for one-pass upsetting and drawing forging thermomechanical treatment. For each pass, use the process of two-upsetting and two-drawing with intermediate reverse drawing. The single-pass upsetting and drawing forging ratio is controlled between 1.5 and 2.0. After forging, air-cool to room temperature.

[0076] (4) Place the Ti-55531 alloy forging blank obtained in step (3) at 35 °C below the phase transformation point for solution heat treatment with a holding time of 45 min, and then air-cool to room temperature. Subsequently, perform aging heat treatment at 600 °C with a holding time of 8 h, and then air-cool to room temperature.

[0077] After comprehensively regulating the microstructure and properties of Ti-55531 titanium alloy through the above thermomechanical treatment and heat treatment, a microstructure can be obtained with a grain size less than 10 μm, a globular α-phase content of 5-20% and macroscopically uniform distribution along the grain boundaries, and fine needle-like secondary α-phase dispersedly distributed in the β-phase matrix (as Figure 4as shown in the figure, which further enables the alloy to achieve a good match of high strength and toughness, i.e., R m = 1289 MPa, R p0.2 = 1283 MPa, A = 13.0%, K IC = 59 MPa·m 1 / 2 .

[0078] Example 4

[0079] The difference between this embodiment and Embodiment 1 lies in Step (4), and its aging temperature is 620 °C, which enables the alloy to achieve a good match of high strength and toughness, i.e., R m = 1305 MPa, R p0.2 = 1284 MPa, A = 8.5%, K IC = 79 MPa·m 1 / 2 . Its microstructural characteristics are as Figure 5 shown.

[0080] Example 5

[0081] The difference between this embodiment and Embodiment 1 lies in Step (4), and its aging time is 10 h, which enables the alloy to achieve a good match of high strength and toughness, i.e., R m = 1321 MPa, R p0.2 = 1306 MPa, A = 11.0%, K IC = 66 MPa·m 1 / 2 . Its microstructural characteristics are as Figure 6 shown.

[0082] It should be clear that each embodiment in this specification is described in a progressive manner. For the same or similar parts between each embodiment, reference can be made to each other. The key point of each embodiment is to illustrate the differences from other embodiments. The present invention is not limited to the specific steps and structures described above and shown in the figures. And, for the sake of brevity, the detailed description of known method technologies is omitted here.

[0083] The above are only the embodiments of the present application and do not limit the present application. For those skilled in the art, the present application can have various changes and modifications without departing from the scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present application shall be included within the scope of the claims of the present application.

Claims

1. A method for regulating the microstructure and properties of a near-β titanium alloy with high strength and toughness matching, characterized in that, the method comprises the following steps: Placing a near-β titanium alloy ingot at an initial forging temperature of 1100 - 1150 °C for at least one-pass upsetting and drawing forging thermo-mechanical treatment, and after each pass of forging, air-cooling to room temperature to obtain a first near-β titanium alloy forging blank; Placing the first near-β titanium alloy forging blank at an initial forging temperature 120 - 150 °C above the phase transformation point for at least one-pass upsetting and drawing forging thermo-mechanical treatment to promote the dynamic and static recrystallization of the alloy material, inhibit the excessive growth of the microstructure grains at high temperature, and rapidly refine the grains of the alloy microstructure. After forging is completed, air-cool to room temperature to obtain a second near-β titanium alloy forging blank; Placing the second near-β titanium alloy forging blank at an initial forging temperature 20 - 40 °C below the phase transformation point for at least one-pass upsetting and drawing forging thermo-mechanical treatment, and after forging is completed, air-cool to room temperature to obtain a third near-β titanium alloy forging blank; Placing the third near-β titanium alloy forging blank under set conditions for solution aging heat treatment to obtain a near-β titanium alloy material with high strength and toughness matching.

2. The method for regulating the microstructure and properties of a near-β titanium alloy with high strength and toughness matching according to claim 1, characterized in that, the step of placing the near-β titanium alloy ingot at an initial forging temperature of 1100 - 1150 °C for at least one-pass upsetting and drawing forging thermo-mechanical treatment is specifically: Adopting a two-upsetting and two-drawing, intermediate-reversing drawing process for each pass, with the single-pass upsetting and drawing forging ratio controlled between 1.5 and 2.5, and after each pass of forging, air-cooling to room temperature respectively.

3. The method for regulating the microstructure and properties of a near-β titanium alloy with high strength and toughness matching according to claim 1, characterized in that, the step of placing the first near-β titanium alloy forging blank at an initial forging temperature 120 - 150 °C above the phase transformation point for at least one-pass upsetting and drawing forging thermo-mechanical treatment is specifically: Adopting a two-upsetting and two-drawing, intermediate-reversing drawing process for each pass, with the single-pass upsetting and drawing forging ratio controlled between 1.5 and 2.

5.

4. The method for regulating the microstructure and properties of a near-β titanium alloy with high strength and toughness matching according to claim 1 or 3, characterized in that, When performing multi-pass upsetting and drawing forging thermo-mechanical treatment at an initial forging temperature 120 - 150 °C above the phase transformation point, after each pass of forging, air-cool to room temperature respectively, reheat and then perform the next pass of forging at this temperature.

5. The method for regulating the microstructure and properties of a near-β titanium alloy with high strength and toughness matching according to claim 1 or 3, characterized in that, When performing multi-pass upsetting and drawing forging thermo-mechanical treatment at an initial forging temperature 120 - 150 °C above the phase transformation point, after each pass of forging, directly return to the furnace for heat preservation and tempering, with the heat preservation time being 90 - 120 min. After taking out of the furnace, continue with subsequent thermo-mechanical treatment deformation until all forging passes at this temperature are completed and then air-cool to room temperature.

6. The method for regulating the microstructure and properties of a near-β titanium alloy with high strength and toughness matching according to claim 1, characterized in that, the step of placing the second near-β titanium alloy forging blank at an initial forging temperature 20 - 40 °C below the phase transformation point for at least one-pass upsetting and drawing forging thermo-mechanical treatment is specifically: For each heat, a two-upsetting and two-drawing process with intermediate re-direction for drawing is adopted, and the upsetting and drawing forging ratios per single pass are controlled between 1.5 and 2.

0.

7. The method for regulating the microstructure and properties with high strength and toughness matching of the near-β titanium alloy according to claim 1 or 6, characterized in that when multi-heat upsetting and drawing thermo-mechanical treatment is carried out at an initial forging temperature 20 - 40 °C below the phase transformation point, after each heat of forging is completed, it is air-cooled to room temperature respectively, and then reheated to carry out the forging of the next heat at this temperature.

8. The method for regulating the microstructure and properties with high strength and toughness matching of the near-β titanium alloy according to claim 1 or 6, characterized in that when multi-heat upsetting and drawing thermo-mechanical treatment is carried out at an initial forging temperature 20 - 40 °C below the phase transformation point, after each heat of forging is completed, it is directly returned to the furnace for heat preservation and tempering, the heat preservation time is 60 - 90 min, and after taking out of the furnace, subsequent thermo-mechanical treatment deformation is continued until after all forging heats at this temperature are completed, and then it is air-cooled to room temperature.

9. The method for regulating the microstructure and properties with high strength and toughness matching of the near-β titanium alloy according to claim 1, characterized in that subjecting the third near-β titanium alloy forging blank to solution aging heat treatment under set conditions to obtain the near-β titanium alloy material, specifically: subjecting the third near-β titanium alloy forging blank to solution heat treatment with heat preservation for t + (30 - 60) min in the temperature range of 15 - 55 °C below the phase transformation point, and then air-cooling to room temperature; subsequently, subjecting it to aging heat treatment with heat preservation for 6 - 10 h in the temperature range of 580 - 620 °C, and after air-cooling to room temperature, the near-β titanium alloy material is obtained; where t is the time required for the sample to reach uniform temperature, which is obtained by multiplying the heating coefficient by the interface thickness or diameter of the sample, and the heating coefficient is taken as 0.5 - 0.8 min / mm.

10. The method for regulating the microstructure and properties with high strength and toughness matching of the near-β titanium alloy according to claim 1, characterized in that the near-β titanium alloy material has a microstructure feature with a grain size less than 10 μm, a globular α-phase content of 5 - 20% and macroscopically uniformly distributed along the grain boundaries, and fine acicular secondary α-phase dispersedly distributed in the β-phase matrix.

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