Method for preparing microstructure homogenization of titanium-based intermetallic compound

Abstract

The application discloses a preparation method of microstructure homogenization of titanium-based intermetallic compound, which comprises the following steps: preparing a titanium-based intermetallic compound blank; determining a key temperature interval of the titanium-based intermetallic compound blank; performing open upsetting forging forming, homogenization treatment, single-phase zone forging forming and two-phase zone forging forming on the titanium-based intermetallic compound blank; and evaluating whether iteration regulation and control of a heat treatment system and a forging process are needed. Through the cooperation of multiple processes, and in combination with the design of hot working and heat treatment process parameters, the application effectively solves the prominent problems of different sizes, different appearances and uneven distribution of precipitated phases in the prior art, and finally improves the microstructure homogeneity and comprehensive mechanical properties of the titanium-based intermetallic compound.

Description

Technical Field

[0001] This invention belongs to the field of metal material preparation technology, specifically relating to a method for preparing a homogenized microstructure of titanium-based intermetallic compounds. Background Technology

[0002] Titanium-based intermetallic compounds are a class of lightweight metallic structural materials with excellent comprehensive properties, mainly including alloys such as Ti3Al, Ti2AlNb, and TiAl. These materials, with their outstanding characteristics of low density, high specific strength, and high temperature resistance, have shown broad application prospects in high-end equipment manufacturing fields such as aerospace, weaponry, and nuclear power engineering, playing a key role in promoting the development of related equipment towards lightweight, high efficiency, and long service life.

[0003] However, the practical engineering applications of titanium-based intermetallic compounds have long been constrained by their poor processability and narrow hot working window. Due to their high degree of alloying, these materials exhibit strong directional and covalent bonding between atoms, leading to complex hot deformation behavior and an extremely sensitive microstructure to thermodynamic parameters. This makes precise control of the microstructure a technological bottleneck. Simultaneously, the narrow hot working window means that even small fluctuations in process parameters can cause significant changes in the microstructure, thereby affecting mechanical properties. Therefore, overcoming the challenges of microstructure control in titanium-based intermetallic compounds to optimize mechanical properties has always been an important research direction in this field and a key technological prerequisite for promoting the practical application of these materials in engineering.

[0004] In existing processes for preparing titanium-based intermetallic compounds, microstructure inhomogeneity is a particularly prominent issue. Specifically, due to the significant differences in the diffusion rates of alloying elements within the matrix, and the difficulty in achieving completely uniform distribution of temperature and strain fields during hot working, the final product exhibits variations in precipitate size, morphology, and spatial distribution. This microstructure inhomogeneity not only causes significant fluctuations in the material's mechanical properties but also severely reduces the consistency of product performance, thereby hindering the large-scale application of titanium-based intermetallic compounds in key components of high-end equipment.

[0005] To address the aforementioned issue of microstructure inhomogeneity, some existing research has attempted to improve it by adjusting heat treatment regimes or optimizing deformation process parameters. However, these methods struggle to simultaneously achieve comprehensive homogenization of precipitated phase morphology, size, and distribution, and some process routes are complex and require sophisticated equipment, limiting their industrial application. Therefore, how to effectively improve the microstructure homogenization of titanium-based intermetallic compounds while ensuring process operability, thereby achieving a stable improvement in overall mechanical properties, remains a pressing technical problem to be solved in this field.

[0006] In view of the above technical problems, there is an urgent need to develop a preparation method for homogenizing the microstructure of titanium-based intermetallic compounds. By synergistic design of heat treatment regime and heat processing path, the homogenization of microstructure can be controlled, thereby improving the comprehensive mechanical properties of materials and product consistency. Summary of the Invention

[0007] The purpose of this invention is to provide a method for homogenizing the microstructure of titanium-based intermetallic compounds, thereby improving the uniformity of the microstructure of titanium-based intermetallic compounds such as Ti3Al and Ti2AlNb. This method utilizes a combination of processes such as billet forging, homogenization treatment, single-phase forging, and two-phase forging, combined with the design of hot working and heat treatment process parameters, to homogenize the chemical composition and microstructure of the alloy, thereby significantly improving the comprehensive mechanical properties of titanium-based intermetallic compound materials.

[0008] To address the problems existing in the prior art, the present invention provides a method for preparing a homogenized microstructure of a titanium-based intermetallic compound, the preparation method comprising the following steps in sequence: Step 1: Prepare titanium-based intermetallic compound billets, which must simultaneously meet the following three requirements: (1) The titanium-based intermetallic compound billet is an alloy ingot obtained by 3-4 vacuum self-consumption melting processes; (2) The riser and bottom pad of the alloy ingot have been removed; (3) The surface of the alloy ingot is bright, and its rough outer surface and visible surface oxide layer have been removed by machining. Step 2: Determine the critical temperature range for titanium-based intermetallic compound billets. The determination method includes the following steps: S1. Several small-sized test blocks are cut from the titanium-based intermetallic compound billet for subsequent phase transformation point testing; S2. All test blocks used for phase transformation point testing are heated to 1200℃ and held for 1 hour to ensure that the initial microstructure of each test block is consistent. Then, each test block is cooled down step by step in temperature increments of 10-20℃ and held at different temperatures for 1 hour after cooling. After holding, the test blocks are water-cooled to room temperature; S3. The microstructure of each heat-treated test block is characterized to obtain the microstructure morphology of the test blocks at different temperatures; S4. The phase transformation temperature is determined according to the formation law of each type of phase, and three key phase transformation point temperatures are tested. The phase transformation point temperature from the single-phase region to the high-temperature two-phase region is recorded as T1, the phase transformation point temperature from the high-temperature two-phase region to the three-phase region is recorded as T2, and the phase transformation point temperature from the three-phase region to the low-temperature two-phase region is recorded as T3. Step 3: The titanium-based intermetallic compound billet is subjected to gradient heating treatment in a heat treatment furnace. Then, the titanium-based intermetallic compound billet is transferred to a forging equipment for one pass of alternating upsetting and drawing hot deformation, i.e., open billet forging. The cumulative deformation of upsetting and drawing in this pass is 10-50%, and finally a titanium-based intermetallic compound open billet forging billet with a height-to-diameter ratio of 2.8-3.0 is formed. After the open billet forging is completed, it is air-cooled to room temperature. Step 4: The titanium-based intermetallic compound forged billet after forging is homogenized in a heat treatment furnace, and then air-cooled to room temperature after the homogenization process is completed. Step 5: The homogenized titanium-based intermetallic compound billet is subjected to 1-3 passes of single-phase zone forging. Before each single-phase zone forging, the titanium-based intermetallic compound billet is first heated in a heat treatment furnace. Then, the titanium-based intermetallic compound billet is transferred to forging equipment for alternating upsetting and drawing hot deformation. The cumulative deformation of upsetting and drawing is 10-50%. After each single-phase zone forging, a titanium-based intermetallic compound forging billet with a height-to-diameter ratio of 2.5-2.8 is obtained and air-cooled to room temperature. Step Six: The titanium-based intermetallic compound forging billet after single-phase forging is subjected to 5-7 passes of two-phase forging. Before each two-phase forging, the titanium-based intermetallic compound forging billet is first heated in a heat treatment furnace. Then, the titanium-based intermetallic compound forging billet is transferred to forging equipment for alternating upsetting and drawing hot deformation. The cumulative deformation of upsetting and drawing is 10-50%. After each two-phase forging, a titanium-based intermetallic compound forging billet with a height-to-diameter ratio of 2.5-2.8 is obtained and air-cooled to room temperature. Step 7: Take several small samples from different radial positions along the end face of the titanium-based intermetallic compound forging billet after forging in the two-phase region, and test the microstructure of the samples to obtain the morphological characteristics of the precipitated phases; determine whether it is necessary to iteratively adjust the heat treatment regime and forging process based on the test results.

[0009] Preferably, in step one, the titanium-based intermetallic compound blank is cylindrical, with a diameter of not less than 300 mm and a length of not less than 400 mm.

[0010] In any of the above schemes, it is preferred that, in step two, the length, width and height of the test block are all 10-20mm; T1 is the phase transition temperature from the single-phase region to the high-temperature two-phase region, T2 is the phase transition temperature from the high-temperature two-phase region to the three-phase region, and T3 is the phase transition temperature from the three-phase region to the low-temperature two-phase region.

[0011] In any of the above schemes, the preferred embodiment is that, in step three, the gradient heating process is as follows: first, the heat treatment furnace is heated to T.a Then, the titanium-based intermetallic compound billet is placed in a heat treatment furnace and held at that temperature for a time t. a Then, heat to T at a rate of 80-100℃ / h. b Insulation time t b Finally, the temperature is increased to T at a rate of 80-100℃ / h. c Insulation time t c .

[0012] Wherein: T a =T3-50℃, (K1×D1-30)min≤t a ≤(K1×D1+30)min;T b =T2+20℃, (K1×D1-30)min≤t b ≤(K1×D1+30)min;T c =T1~1250℃, (K1×D1-30)min≤t c ≤ (K1×D1+30)min; D1 is the diameter of the titanium-based intermetallic compound billet, in mm; K1 is the temperature coefficient, with a set value of 0.4-0.6mm. -1 .

[0013] In any of the above schemes, the preferred embodiment is that, in step four, the homogenization process is as follows: first, the heat treatment furnace is heated to T. d Then, the titanium-based intermetallic compound forged billet is placed in a heat treatment furnace and held for a time t. d Then, heat to T at a rate of 200-300℃ / h. e Insulation time t e Finally, the temperature is increased to T at a rate of 200-300℃ / h. f Insulation time t f .

[0014] Wherein: T d =300℃, (K2×D2-30)min≤t d ≤(K2×D2+30)min;T e = (T2+T3) / 2, (K2×D2-30)min≤t e ≤(K2×D2+30)min;T f =T1+100℃, (K3×D2)min≤t f ≤ (K4×D2)min; D2 is the diameter of the titanium-based intermetallic compound forged billet after forging, in mm; K2 is the temperature coefficient, with a set value of 0.2mm. -1 K3 is the temperature coefficient, and its set value is 0.5mm. -1K4 is the temperature coefficient, and its set value is 2mm. -1 .

[0015] In any of the above schemes, the preferred embodiment is that, in step five, the heat treatment process for the single-phase forging stage is as follows: first, the heat treatment furnace is heated to T... a Then, the titanium-based intermetallic compound billet is placed in a heat treatment furnace and held at that temperature for a time t. a Then, the temperature is increased to T at a rate of 80-100℃ / h. b Insulation time t b Finally, the temperature is increased to T at a rate of 80-100℃ / h. g Insulation time t g .

[0016] Wherein: T a =T3-50℃, (K1×D3-30)min≤t a ´≤(K1×D3+30)min;T b =T2+20℃, (K1×D3-30)min≤t b ´≤(K1×D3+30)min;T g = (T1+20℃)~(T1+50℃), (K5×D3)min≤t g ≤ (K5×D3+60)min; D3 is the diameter of the titanium-based intermetallic compound billet after homogenization treatment, in mm; K5 is the temperature coefficient, with a set value of 0.3mm. -1 .

[0017] In any of the above schemes, the preferred embodiment is that, in step six, the heat treatment process for the two-phase region forging stage is as follows: first, the heat treatment furnace is heated to T... a Then, the titanium-based intermetallic compound billet is placed in a heat treatment furnace and held at that temperature for a time t. a Then, heat to T at a rate of 80-100℃ / h. b Insulation time t b Finally, the temperature is increased to T at a rate of 80-100℃ / h. h Insulation time t h .

[0018] Wherein: T a =T3-50℃,(K1×D4-30)min≤t a ´´≤(K1×D4+30)min;T b =T2+20℃, (K1×D4-30)min≤t b ´´≤(K1×D4+30)min;T h= (T2+20℃)~(T1-20℃), (K6×D4)min≤t h ≤ (K6×D4+60)min; D4 changes with the number of forging cycles in the two-phase region, specifically the diameter of the titanium-based intermetallic compound billet after the previous forging cycle, in mm; K6 is a temperature coefficient, with a set value of 0.3mm. -1 .

[0019] In any of the above schemes, preferably, in step seven, if there are precipitates with obvious banded, non-uniform distribution characteristics, the process returns to the homogenization treatment step and the subsequent single-phase region forging and two-phase region forging steps for re-preparation. If there are precipitates with linear, discontinuous distribution characteristics, the process returns to the single-phase region forging and the subsequent two-phase region forging steps for re-preparation. If there are precipitates with obvious deformation characteristics, the process returns to the two-phase region forging step for re-preparation.

[0020] This invention innovatively employs a process sequence of "forging in the initial billet → homogenization treatment → single-phase forging → two-phase forging." Its core advantage lies in the following: during the initial billet forging process, the forging deformation breaks down the coarse as-cast structure, introducing numerous dislocations, vacancies, and other crystal defects, as well as refined grain boundaries. This provides a rapid pathway for the diffusion of alloying elements during the subsequent homogenization treatment, resulting in higher efficiency and better homogenization. Simultaneously, the combination of multi-pass single-phase and two-phase forging processes with stepped heating further homogenizes the alloy composition and microstructure of the titanium-based intermetallic compound billet, ensuring that the final microstructure is the ideal homogenized state. This process sequence creates a synergistic effect of "deformation introducing defects to promote diffusion + diffusion stabilizing the microstructure," which is more conducive to obtaining a microstructure with highly consistent precipitate size, morphology, and distribution.

[0021] Compared with the prior art, the preparation method for homogenizing the microstructure of titanium-based intermetallic compounds of the present invention has the following beneficial effects: (1) This invention effectively promotes the diffusion uniformity of alloying elements in the matrix by identifying the key temperature range of titanium-based intermetallic compounds and combining the synergistic effect of the cumulative strain field and temperature field during hot working. On this basis, by utilizing the synergistic cooperation of multiple processes such as billet forging, homogenization treatment, single-phase forging and two-phase forging, and by synergistically optimizing the hot working and heat treatment process parameters, the size, morphology and spatial distribution of precipitated phases are systematically controlled, which effectively solves the prominent problems of inconsistent precipitated phase size, different morphologies and uneven distribution in the prior art, and significantly improves the microstructure uniformity of titanium-based intermetallic compounds.

[0022] (2) This invention combines the homogenization treatment of the chemical composition of the alloy with the homogenization treatment of the microstructure, which significantly improves the comprehensive mechanical properties of the titanium-based intermetallic compound. At the same time, the significant improvement in the uniformity of the microstructure effectively reduces the performance fluctuation between product batches, and the consistency and reliability are effectively guaranteed, thus laying the foundation for the large-scale application of titanium-based intermetallic compounds in high-end equipment fields such as aerospace, weaponry and nuclear power engineering.

[0023] (3) This invention fully utilizes the microstructure evolution and thermoforming laws of titanium-based intermetallic compounds. The processes employed, such as billet forging, homogenization treatment, heat treatment, and multi-stage forging, can all be completed in conventional heat treatment furnaces and forging equipment, without the need for additional special equipment or high-cost equipment. The process route of this invention has advantages such as a relatively relaxed process window and easy control of process parameters. Compared with the technical solutions in the prior art that are complex and require high equipment, this invention significantly lowers the threshold for industrial implementation while ensuring the homogenization effect of microstructure. It has strong operability and applicability, and has important engineering application value for the microstructure regulation and performance optimization of titanium-based intermetallic compounds. Attached Figure Description

[0024] Figure 1 A photograph of the initial Ti2AlNb intermetallic compound billet in a preferred embodiment of the preparation method for homogenizing the microstructure of titanium-based intermetallic compounds according to the present invention; Figure 2 for Figure 1 Micrograph of the titanium-based intermetallic compound finally prepared in the illustrated embodiment. Detailed Implementation

[0025] To further understand the invention, the following detailed description of the invention will be provided in conjunction with specific embodiments.

[0026] Example 1: According to a preferred embodiment of the method for preparing homogenized microstructure of titanium-based intermetallic compounds of the present invention, taking the heat treatment and multi-stage forging process of Ti2AlNb intermetallic compounds as an example, the preparation method includes the following steps in sequence: Step 1: Prepare titanium-based intermetallic compound billets, which must simultaneously meet the following three requirements: (1) The titanium-based intermetallic compound billet is an alloy ingot obtained through 3-4 vacuum consumable melting processes; (2) The riser and bottom pad of the alloy ingot have been removed; (3) The surface of the alloy ingot is bright, and its rough outer surface and visible surface oxide layer have been removed by machining. In this embodiment, the titanium-based intermetallic compound billet is cylindrical with a diameter of 300 mm and a length of 400 mm.

[0027] Step 2: Determine the critical temperature range for titanium-based intermetallic compound billets. The determination method includes the following steps: S1. Several small-sized test blocks are cut from the titanium-based intermetallic compound billet for subsequent phase transformation point testing; S2. All test blocks used for phase transformation point testing are heated to 1200℃ and held for 1 hour to ensure that the initial microstructure of each test block is consistent. Then, each test block is cooled down stepwise in increments of 10-20℃ and held at different temperatures for 1 hour after cooling. After holding, the test blocks are water-cooled to room temperature; S3. The microstructure of each heat-treated test block is characterized to obtain the microstructure morphology of the test blocks at different temperatures; S4. The phase transformation temperature is determined according to the formation law of each type of phase, and three key phase transformation point temperatures are tested. The phase transformation point temperature from the single-phase region to the high-temperature two-phase region is recorded as T1, the phase transformation point temperature from the high-temperature two-phase region to the three-phase region is recorded as T2, and the phase transformation point temperature from the three-phase region to the low-temperature two-phase region is recorded as T3.

[0028] In this embodiment, the length, width and height of the test block are all 10mm; the temperature is gradually reduced in 10℃ increments and kept at different temperatures for 1h. After microstructure testing and quantitative evaluation, T1=1080℃, T2=990℃ and T3=810℃ are determined.

[0029] Step 3: The titanium-based intermetallic compound billet is subjected to gradient heating treatment in a heat treatment furnace. Then, the titanium-based intermetallic compound billet is transferred to a forging equipment for one pass of alternating upsetting and drawing hot deformation, i.e., open billet forging. The cumulative deformation of upsetting and drawing in this pass is 10-50%, and finally a titanium-based intermetallic compound open billet forging billet with a height-to-diameter ratio of 2.8-3.0 is formed. After the open billet forging is completed, it is air-cooled to room temperature.

[0030] The gradient heating process is as follows: first, the heat treatment furnace is heated to T. a Then, the titanium-based intermetallic compound billet is placed in a heat treatment furnace and held at that temperature for a time t. a Then, heat to T at a rate of 80-100℃ / h. b Insulation time t b Finally, the temperature is increased to T at a rate of 80-100℃ / h. c Insulation time t c .

[0031] Wherein: T a =T3-50℃, (K1×D1-30)min≤t a ≤(K1×D1+30)min;T b =T2+20℃, (K1×D1-30)min≤t b ≤(K1×D1+30)min;T c=T1~1250℃, (K1×D1-30)min≤t c ≤ (K1×D1+30)min; D1 is the diameter of the titanium-based intermetallic compound billet, in mm; K1 is the temperature coefficient, with a set value of 0.4-0.6mm. -1 .

[0032] In this embodiment, T a =760℃, T b =1010℃, T c =1080~1250℃ (take 1165℃), 120min≤t a =t b =t c ≤180min (take 150min); D1=300mm, K1=0.5mm -1 The gradient heating process is as follows: First, the heat treatment furnace is heated to 760℃, then the titanium-based intermetallic compound billet is placed in the furnace and held for 150 min; then, the temperature is increased to 1010℃ at a rate of 90℃ / h and held for 150 min; finally, the temperature is increased to 1165℃ at a rate of 90℃ / h and held for 150 min. After one pass of alternating upsetting and drawing hot deformation, with a cumulative deformation of 30%, the final titanium-based intermetallic compound forging billet has a diameter of 230 mm, a length of 650 mm, and a height-to-diameter ratio controlled within the range of 2.8-3.0.

[0033] Step 4: The titanium-based intermetallic compound forged billet after forging is homogenized in a heat treatment furnace, and then air-cooled to room temperature after homogenization.

[0034] The homogenization process is as follows: First, the heat treatment furnace is heated to T. d Then, the titanium-based intermetallic compound forged billet is placed in a heat treatment furnace and held for a time t. d Then, heat to T at a rate of 200-300℃ / h. e Insulation time t e Finally, the temperature is increased to T at a rate of 200-300℃ / h. f Insulation time t f .

[0035] Wherein: T d =300℃, (K2×D2-30)min≤t d ≤(K2×D2+30)min;T e = (T2+T3) / 2, (K2×D2-30)min≤t e ≤(K2×D2+30)min;Tf =T1+100℃, (K3×D2)min≤t f ≤ (K4×D2)min; D2 is the diameter of the titanium-based intermetallic compound forged billet after forging, in mm; K2 is the temperature coefficient, with a set value of 0.2mm. -1 K3 is the temperature coefficient, and its set value is 0.5mm. -1 K4 is the temperature coefficient, and its set value is 2mm. -1 .

[0036] In this embodiment, T d =300℃, T e =900℃, T f =1180℃, 16min≤t d =t e ≤76min (take 46min), 115min≤t f ≤460min (take 280min); D2=230mm, K2=0.2mm -1 K3=0.5mm -1 K4=2mm -1 The homogenization process is as follows: First, the heat treatment furnace is heated to 300℃, and then the titanium-based intermetallic compound forged billet is placed into the heat treatment furnace and held for 46 minutes; then, the temperature is increased to 900℃ at a rate of 250℃ / h and held for 46 minutes; finally, the temperature is increased to 1180℃ at a rate of 250℃ / h and held for 280 minutes.

[0037] Step 5: The homogenized titanium-based intermetallic compound billet is subjected to 1-3 passes of single-phase zone forging. Before each single-phase zone forging, the titanium-based intermetallic compound billet is first heated in a heat treatment furnace. Then, the titanium-based intermetallic compound billet is transferred to forging equipment for alternating upsetting and drawing hot deformation. The cumulative deformation of upsetting and drawing is 10-50%. After each single-phase zone forging, a titanium-based intermetallic compound forging billet with a height-to-diameter ratio of 2.5-2.8 is obtained and air-cooled to room temperature.

[0038] The heat treatment process for the single-phase forging stage is as follows: First, the heat treatment furnace is heated to T. a Then, the titanium-based intermetallic compound billet is placed in a heat treatment furnace and held at that temperature for a time t. a Then, the temperature is increased to T at a rate of 80-100℃ / h. b Insulation time t b Finally, the temperature is increased to T at a rate of 80-100℃ / h. g Insulation time t g .

[0039] Wherein: T a =T3-50℃, (K1×D3-30)min≤t a ´≤(K1×D3+30)min;T b =T2+20℃, (K1×D3-30)min≤t b ´≤(K1×D3+30)min;T g = (T1+20℃)~(T1+50℃), (K5×D3)min≤t g ≤ (K5×D3+60)min; D3 is the diameter of the titanium-based intermetallic compound billet after homogenization treatment, in mm; K5 is the temperature coefficient, with a set value of 0.3mm. -1 .

[0040] In this embodiment, T a =760℃, T b =1010℃, 85min≤t a ´=t b ´≤145min (take 115min), T g =1100~1130℃ (take 1120℃), 69min≤t g ≤129min (100min); D3≈D2=230mm, K1=0.5mm -1 K5=0.3mm -1 The heat treatment process for the single-phase zone forging stage is as follows: First, the heat treatment furnace is heated to 760℃, and then the titanium-based intermetallic compound billet is placed in the heat treatment furnace and held for 115 minutes; then, the temperature is increased to 1010℃ at a rate of 90℃ / h and held for 115 minutes; finally, the temperature is increased to 1120℃ at a rate of 90℃ / h and held for 100 minutes. After three passes of single-phase zone forging, the height-to-diameter ratio of the titanium-based intermetallic compound forging billet is controlled within the range of 2.5-2.8 after each pass of forging; each pass of single-phase zone forging requires alternating upsetting and drawing hot deformation, with a cumulative deformation of 30%; the final titanium-based intermetallic compound forging billet has a diameter of approximately 220 mm and a length of approximately 610 mm.

[0041] Step Six: The titanium-based intermetallic compound forging billet after single-phase forging is subjected to 5-7 passes of two-phase forging. Before each two-phase forging, the titanium-based intermetallic compound forging billet is first heated in a heat treatment furnace. Then, the titanium-based intermetallic compound forging billet is transferred to forging equipment for alternating upsetting and drawing hot deformation. The cumulative deformation of upsetting and drawing is 10-50%. After each two-phase forging, a titanium-based intermetallic compound forging billet with a height-to-diameter ratio of 2.5-2.8 is obtained and air-cooled to room temperature.

[0042] The heat treatment process for the two-phase region forging stage is as follows: First, the heat treatment furnace is heated to T. a Then, the titanium-based intermetallic compound billet is placed in a heat treatment furnace and held at that temperature for a time t. a Then, heat to T at a rate of 80-100℃ / h. b Insulation time t b Finally, the temperature is increased to T at a rate of 80-100℃ / h. h Insulation time t h .

[0043] Wherein: T a =T3-50℃,(K1×D4-30)min≤t a ´´≤(K1×D4+30)min;T b =T2+20℃, (K1×D4-30)min≤t b ´´≤(K1×D4+30)min;T h = (T2+20℃)~(T1-20℃), (K6×D4)min≤t h ≤ (K6×D4+60)min; D4 changes with the number of forging cycles in the two-phase region, specifically the diameter of the titanium-based intermetallic compound billet after the previous forging cycle, in mm; K6 is a temperature coefficient, with a set value of 0.3mm. -1 .

[0044] In this embodiment, after six passes of two-phase forging, the aspect ratio of the titanium-based intermetallic compound forging billet is controlled within the range of 2.5-2.8 after each forging pass. The diameter and length of the billet after each forging pass are 240×610mm, 238×615mm, 234×620mm, 232×625mm, 230×630mm, and 228×635mm, respectively. Each pass of two-phase forging requires alternating upsetting and drawing hot deformation, and the cumulative deformation of upsetting and drawing is 30%.

[0045] T a =760℃, T b =1010℃, Th =1010~1060℃ (take 1035℃); K1=0.5mm -1 K6=0.3mm -1 ;D4=220mm, 240mm, 238mm, 234mm, 232mm, 230mm; t a ´´ and t b The time varies with D4; the calculation of the time for the last six heating treatments takes a uniform value t. h ==100min.

[0046] Step 7: Take several small samples from different radial positions along the end face of the titanium-based intermetallic compound forging billet after forging in the two-phase region, and test the microstructure of the samples to obtain the morphological characteristics of the precipitated phases; determine whether it is necessary to iteratively adjust the heat treatment regime and forging process based on the test results.

[0047] If there are precipitates with obvious banded, non-uniform distribution characteristics, the process returns to the homogenization step and subsequent single-phase forging and two-phase forging steps for re-preparation. If there are precipitates with linear, discontinuous distribution characteristics, the process returns to the single-phase forging and subsequent two-phase forging steps for re-preparation. If there are precipitates with obvious deformation characteristics, the process returns to the two-phase forging step for re-preparation. This embodiment does not contain any of the above three types of precipitates, and iterative control is not required.

[0048] Compared with the prior art, this embodiment has the following beneficial effects: (1) By utilizing multiple processes such as billet forging, homogenization treatment, single-phase forging and two-phase forging, and by coordinating and optimizing the hot working and heat treatment process parameters, the prominent problems of inconsistent precipitate size, different morphology and uneven distribution in the prior art are effectively solved, and the microstructure uniformity of titanium-based intermetallic compounds is significantly improved. (2) By combining the chemical composition homogenization treatment of the alloy with the microstructure homogenization treatment, the comprehensive mechanical properties of titanium-based intermetallic compounds are significantly improved; at the same time, the significant improvement in microstructure uniformity effectively reduces the performance fluctuation between product batches. (3) The billet forging, homogenization treatment and multi-stage forging processes can all be completed in conventional heat treatment furnaces and forging equipment, without the need to add special equipment or high-cost equipment. The process route has the advantages of a relatively loose process window and easy control of process parameters.

[0049] Example 2: Another preferred embodiment of the method for preparing homogenized microstructure of titanium-based intermetallic compounds according to the present invention has the same process flow, technical principle, and beneficial effects as that of Embodiment 1, except that: In step one, the titanium-based intermetallic compound blank is cylindrical with a diameter of 300 mm and a length of 400 mm.

[0050] In step two, the length, width and height of the test block are all 15mm; the temperature is gradually reduced in 15℃ increments and kept at different temperatures for 1 hour. After microstructure testing and quantitative evaluation, T1=1050℃, T2=950℃ and T3=800℃ are determined.

[0051] In step three, T a =750℃, T b =970℃, T c =1050~1250℃ (take 1150℃), 120min≤t a =t b =t c ≤180min (take 130min); D1=300mm, K1=0.5mm -1 The gradient heating process is as follows: First, the heat treatment furnace is heated to 750℃, then the titanium-based intermetallic compound billet is placed in the furnace and held for 130 minutes; then, the temperature is increased to 970℃ at a rate of 80℃ / h and held for 130 minutes; finally, the temperature is increased to 1150℃ at a rate of 80℃ / h and held for 130 minutes. After one pass of alternating upsetting and drawing hot deformation, with a cumulative deformation of 30%, the final titanium-based intermetallic compound forging billet has a diameter of 230mm, a length of 650mm, and a height-to-diameter ratio controlled within the range of 2.8-3.0.

[0052] In step four, T d =300℃, T e =875℃, T f =1150℃, 16min≤t d =t e ≤76min (take 46min), 115min≤t f ≤460min (take 280min); D2=230mm, K2=0.2mm -1 K3=0.5mm -1 K4=2mm -1 The homogenization process is as follows: First, the heat treatment furnace is heated to 300℃, and then the titanium-based intermetallic compound forged billet is placed into the heat treatment furnace and held for 46 minutes; then, the temperature is increased to 875℃ at a rate of 200℃ / h and held for 46 minutes; finally, the temperature is increased to 1150℃ at a rate of 200℃ / h and held for 280 minutes.

[0053] In step five, T a =750℃, T b =970℃, 85min≤ta ´=t b ´≤145min (take 115min), T g =1100~1130℃ (take 1115℃), 69min≤t g ≤129min (100min); D3≈D2=230mm, K1=0.5mm -1 K5=0.3mm -1 The heat treatment process for the single-phase zone forging stage is as follows: First, the heat treatment furnace is heated to 750℃, and then the titanium-based intermetallic compound billet is placed in the heat treatment furnace and held for 115 minutes; then, the temperature is increased to 970℃ at a rate of 90℃ / h and held for 115 minutes; finally, the temperature is increased to 1115℃ at a rate of 90℃ / h and held for 100 minutes. After three passes of single-phase zone forging, the height-to-diameter ratio of the titanium-based intermetallic compound forging billet is controlled within the range of 2.5-2.8 after each pass of forging; each pass of single-phase zone forging requires alternating upsetting and drawing hot deformation, with a cumulative deformation of 30%; the final titanium-based intermetallic compound forging billet has a diameter of approximately 220 mm and a length of approximately 610 mm.

[0054] In step six, after six passes of two-phase forging, the aspect ratio of the resulting titanium-based intermetallic compound forged billet is controlled within the range of 2.5-2.8 after each forging pass. The diameter and length of the billet after each forging pass are 240×610mm, 238×615mm, 234×620mm, 232×625mm, 230×630mm, and 228×635mm, respectively. Each pass of two-phase forging requires alternating upsetting and drawing hot deformation, with a cumulative deformation of 30% from upsetting and drawing. a =750℃, T b =970℃, T h =970-1030℃ (take 1000℃); K1=0.5mm -1 K6=0.3mm -1 D4 = 220mm, 240mm, 238mm, 234mm, 232mm, 230mm; the heat treatment time for the last six heat treatments is taken as a uniform value t. h ==100min.

[0055] Example 3: Another preferred embodiment of the method for preparing homogenized microstructure of titanium-based intermetallic compounds according to the present invention has the same process flow, technical principle, and beneficial effects as that of Embodiment 1, except that: In step one, the titanium-based intermetallic compound blank is cylindrical with a diameter of 300 mm and a length of 400 mm.

[0056] In step two, the length, width and height of the test block are all 20mm; the temperature is gradually reduced in 20℃ increments and kept at different temperatures for 1 hour. After microstructure testing and quantitative evaluation, T1=1060℃, T2=980℃ and T3=810℃ are determined.

[0057] In step three, T a =760℃, T b =1000℃, T c =1060~1250℃ (take 1155℃), 120min≤t a =t b =t c ≤180min (take 160min); D1=300mm, K1=0.5mm -1 The gradient heating process is as follows: First, the heat treatment furnace is heated to 760℃, then the titanium-based intermetallic compound billet is placed in the furnace and held for 160 min; then, the temperature is increased to 1000℃ at a rate of 100℃ / h and held for 160 min; finally, the temperature is increased to 1155℃ at a rate of 100℃ / h and held for 160 min. After one pass of alternating upsetting and drawing hot deformation, with a cumulative deformation of 30%, the final titanium-based intermetallic compound forging billet has a diameter of 230 mm, a length of 650 mm, and a height-to-diameter ratio controlled within the range of 2.8-3.0.

[0058] In step four, T d =300℃, T e =895℃, T f =1160℃, 16min≤t d =t e ≤76min (take 46min), 115min≤t f ≤460min (take 280min); D2=230mm, K2=0.2mm -1 K3=0.5mm -1 K4=2mm -1 The homogenization process is as follows: First, the heat treatment furnace is heated to 300℃, and then the titanium-based intermetallic compound forged billet is placed into the heat treatment furnace and held for 46 minutes; then, the temperature is increased to 895℃ at a rate of 300℃ / h and held for 46 minutes; finally, the temperature is increased to 1160℃ at a rate of 300℃ / h and held for 280 minutes.

[0059] In step five, T a =760℃, T b =1000℃, 85min≤ta ´=t b ´≤145min (take 115min), T g =1080-1110℃ (take 1095℃), 69min≤t g ≤129min (100min); D3≈D2=230mm, K1=0.5mm -1 K5=0.3mm -1 The heat treatment process for the single-phase zone forging stage is as follows: First, the heat treatment furnace is heated to 760℃, and then the titanium-based intermetallic compound billet is placed in the heat treatment furnace and held for 115 minutes; then, the temperature is increased to 1000℃ at a rate of 90℃ / h and held for 115 minutes; finally, the temperature is increased to 1095℃ at a rate of 90℃ / h and held for 100 minutes. After three passes of single-phase zone forging, the height-to-diameter ratio of the titanium-based intermetallic compound forging billet is controlled within the range of 2.5-2.8 after each pass of forging; each pass of single-phase zone forging requires alternating upsetting and drawing hot deformation, with a cumulative deformation of 30%; the final titanium-based intermetallic compound forging billet has a diameter of approximately 220 mm and a length of approximately 610 mm.

[0060] In step six, after six passes of two-phase forging, the aspect ratio of the resulting titanium-based intermetallic compound forged billet is controlled within the range of 2.5-2.8 after each forging pass. The diameter and length of the billet after each forging pass are 240×610mm, 238×615mm, 234×620mm, 232×625mm, 230×630mm, and 228×635mm, respectively. Each pass of two-phase forging requires alternating upsetting and drawing hot deformation, with a cumulative deformation of 30% from upsetting and drawing. a =760℃, T b =1000℃, T h =1000-1040℃ (take 1020℃); K1=0.5mm -1 K6=0.3mm -1 D4 = 220mm, 240mm, 238mm, 234mm, 232mm, 230mm; the heat treatment time for the last six heat treatments is taken as a uniform value t. h ==100min.

[0061] The Ti2AlNb intermetallic compounds prepared in the above three examples were subjected to comprehensive mechanical property tests. The test methods, test environment and test equipment were the same. The test results are shown in Table 1.

[0062]

[0063] The test results in Table 1 show that the three embodiments significantly improved the comprehensive mechanical properties of titanium-based intermetallic compounds by utilizing multiple processes such as billet forging, homogenization treatment, single-phase forging and two-phase forging, and by synergistically optimizing the hot working and heat treatment process parameters.

[0064] Special Note: The technical solution of this invention involves numerous parameters, and the synergistic effects between these parameters must be comprehensively considered to achieve the beneficial effects and significant progress of this invention. Furthermore, the value ranges of each parameter in the technical solution were obtained through extensive experimentation. For each parameter and the combinations thereof, the inventors have recorded a large amount of experimental data; however, due to space limitations, the specific experimental data is not disclosed here.

[0065] It will be readily understood by those skilled in the art that this invention includes any combination of the inventive description and specific embodiments outlined in the foregoing specification, as well as the various parts shown in the accompanying drawings. Due to space limitations and for the sake of brevity, not all of these combinations have been described in detail. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A method for preparing a titanium-based intermetallic compound with homogenized microstructure, characterized in that, The preparation method includes the following steps in sequence: Step 1: Prepare titanium-based intermetallic compound billets, which must simultaneously meet the following three requirements: (1) The titanium-based intermetallic compound billet is an alloy ingot obtained by 3-4 vacuum self-consumption melting processes; (2) The riser and bottom pad of the alloy ingot have been removed; (3) The surface of the alloy ingot is bright, and its rough outer surface and visible surface oxide layer have been removed by machining. Step 2: Determine the critical temperature range for titanium-based intermetallic compound billets. The determination method includes the following steps: S1. Several small-sized test blocks are cut from the titanium-based intermetallic compound billet for subsequent phase transformation point testing; S2. All test blocks used for phase transformation point testing are heated to 1200℃ and held for 1 hour to ensure that the initial microstructure of each test block is consistent. Then, each test block is cooled down step by step in temperature increments of 10-20℃ and held at different temperatures for 1 hour after cooling. After holding, the test blocks are water-cooled to room temperature; S3. The microstructure of each heat-treated test block is characterized to obtain the microstructure morphology of the test blocks at different temperatures; S4. The phase transformation temperature is determined according to the formation law of each type of phase, and three key phase transformation point temperatures are tested. The phase transformation point temperature from the single-phase region to the high-temperature two-phase region is recorded as T1, the phase transformation point temperature from the high-temperature two-phase region to the three-phase region is recorded as T2, and the phase transformation point temperature from the three-phase region to the low-temperature two-phase region is recorded as T3. Step 3: The titanium-based intermetallic compound billet is subjected to gradient heating treatment in a heat treatment furnace. Then, the titanium-based intermetallic compound billet is transferred to a forging equipment for one pass of alternating upsetting and drawing hot deformation, i.e., open billet forging. The cumulative deformation of upsetting and drawing in this pass is 10-50%, and finally a titanium-based intermetallic compound open billet forging billet with a height-to-diameter ratio of 2.8-3.0 is formed. After the open billet forging is completed, it is air-cooled to room temperature. Step 4: The titanium-based intermetallic compound forged billet after forging is homogenized in a heat treatment furnace, and then air-cooled to room temperature after the homogenization process is completed. Step 5: The homogenized titanium-based intermetallic compound billet is subjected to 1-3 passes of single-phase zone forging. Before each single-phase zone forging, the titanium-based intermetallic compound billet is first heated in a heat treatment furnace. Then, the titanium-based intermetallic compound billet is transferred to forging equipment for alternating upsetting and drawing hot deformation. The cumulative deformation of upsetting and drawing is 10-50%. After each single-phase zone forging, a titanium-based intermetallic compound forging billet with a height-to-diameter ratio of 2.5-2.8 is obtained and air-cooled to room temperature. Step Six: The titanium-based intermetallic compound forging billet after single-phase forging is subjected to 5-7 passes of two-phase forging. Before each two-phase forging, the titanium-based intermetallic compound forging billet is first heated in a heat treatment furnace. Then, the titanium-based intermetallic compound forging billet is transferred to forging equipment for alternating upsetting and drawing hot deformation. The cumulative deformation of upsetting and drawing is 10-50%. After each two-phase forging, a titanium-based intermetallic compound forging billet with a height-to-diameter ratio of 2.5-2.8 is obtained and air-cooled to room temperature. Step 7: Take several small samples from different radial positions along the end face of the titanium-based intermetallic compound forging billet after forging in the two-phase region, and test the microstructure of the samples to obtain the morphological characteristics of the precipitated phases; determine whether it is necessary to iteratively adjust the heat treatment regime and forging process based on the test results.

2. The method for preparing homogenized microstructure of titanium-based intermetallic compounds according to claim 1, characterized in that, In step one, the titanium-based intermetallic compound blank is cylindrical with a diameter of not less than 300 mm and a length of not less than 400 mm.

3. The method for preparing homogenized microstructure of titanium-based intermetallic compounds according to claim 2, characterized in that, In step two, the length, width, and height of the test block are all 10-20 mm; T1 is the phase transition temperature from the single-phase region to the high-temperature two-phase region, T2 is the phase transition temperature from the high-temperature two-phase region to the three-phase region, and T3 is the phase transition temperature from the three-phase region to the low-temperature two-phase region.

4. The method for preparing homogenized microstructure of titanium-based intermetallic compounds according to claim 3, characterized in that, In step three, the gradient heating process is as follows: first, the heat treatment furnace is heated to T. a Then, the titanium-based intermetallic compound billet is placed in a heat treatment furnace and held at that temperature for a time t. a Then, heat to T at a rate of 80-100℃ / h. b Insulation time t b Finally, the temperature is increased to T at a rate of 80-100℃ / h. c Insulation time t c ; Wherein: T a =T3-50℃, (K1×D1-30)min≤t a ≤(K1×D1+30)min;T b =T2+20℃, (K1×D1-30)min≤t b ≤(K1×D1+30)min;T c =T1~1250℃, (K1×D1-30)min≤t c ≤ (K1×D1+30)min; D1 is the diameter of the titanium-based intermetallic compound billet, in mm; K1 is the temperature coefficient, with a set value of 0.4-0.6mm. -1 .

5. The method for preparing homogenized microstructure of titanium-based intermetallic compounds according to claim 4, characterized in that, In step four, the homogenization process is as follows: first, the heat treatment furnace is heated to T. d Then, the titanium-based intermetallic compound forged billet is placed in a heat treatment furnace and held for a time t. d Then, heat to T at a rate of 200-300℃ / h. e Insulation time t e Finally, the temperature is increased to T at a rate of 200-300℃ / h. f Insulation time t f ; Wherein: T d =300℃, (K2×D2-30)min≤t d ≤(K2×D2+30)min;T e = (T2+T3) / 2, (K2×D2-30)min≤t e ≤(K2×D2+30)min;T f =T1+100℃, (K3×D2)min≤t f ≤ (K4×D2)min; D2 is the diameter of the titanium-based intermetallic compound forged billet after forging, in mm; K2 is the temperature coefficient, with a set value of 0.2mm. -1 K3 is the temperature coefficient, and its set value is 0.5mm. -1 K4 is the temperature coefficient, and its set value is 2mm. -1 .

6. The method for preparing homogenized microstructure of titanium-based intermetallic compounds according to claim 5, characterized in that, In step five, the heat treatment process for the single-phase forging stage is as follows: first, the heat treatment furnace is heated to T. a Then, the titanium-based intermetallic compound billet is placed in a heat treatment furnace and held at that temperature for a time t. a Then, the temperature is increased to T at a rate of 80-100℃ / h. b Insulation time t b Finally, the temperature is increased to T at a rate of 80-100℃ / h. g Insulation time t g ; Wherein: T a =T3-50℃, (K1×D3-30)min≤t a ´≤(K1×D3+30)min;T b =T2+20℃, (K1×D3-30)min≤t b ´≤(K1×D3+30)min;T g = (T1+20℃)~(T1+50℃), (K5×D3)min≤t g ≤ (K5×D3+60)min; D3 is the diameter of the titanium-based intermetallic compound billet after homogenization treatment, in mm; K5 is the temperature coefficient, with a set value of 0.3mm. -1 .

7. The method for preparing homogenized microstructure of titanium-based intermetallic compounds according to claim 6, characterized in that, In step six, the heat treatment process for the two-phase region forging stage is as follows: First, the heat treatment furnace is heated to T. a Then, the titanium-based intermetallic compound billet is placed in a heat treatment furnace and held at that temperature for a time t. a Then, heat to T at a rate of 80-100℃ / h. b Insulation time t b Finally, the temperature is increased to T at a rate of 80-100℃ / h. h Insulation time t h ; Wherein: T a =T3-50℃,(K1×D4-30)min≤t a ´´≤(K1×D4+30)min;T b =T2+20℃, (K1×D4-30)min≤t b ´´≤(K1×D4+30)min;T h = (T2+20℃)~(T1-20℃), (K6×D4)min≤t h ≤ (K6×D4+60)min; D4 changes with the number of forging cycles in the two-phase region, specifically the diameter of the titanium-based intermetallic compound billet after the previous forging cycle, in mm; K6 is a temperature coefficient, with a set value of 0.3mm. -1 .

8. The method for preparing homogenized microstructure of titanium-based intermetallic compounds according to claim 7, characterized in that, If there are precipitates with obvious banded non-uniform distribution characteristics in step seven, return to the homogenization treatment step and the subsequent single-phase region forging and two-phase region forging steps to prepare again.

9. The method for preparing homogenized microstructure of titanium-based intermetallic compounds according to claim 8, characterized in that, In step seven, if there are linear discontinuous precipitates, return to the single-phase forging step and the subsequent two-phase forging step to prepare again.

10. The method for preparing homogenized microstructure of titanium-based intermetallic compounds according to claim 9, characterized in that, If obvious deformation-characteristic precipitate morphology exists in step seven, return to the two-phase region forging and molding step to prepare again.

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