A method for improving the strength and ductility of a metastable beta titanium alloy
By performing solid solution treatment in the α+β dual-phase region combined with water quenching, the precipitation of the α phase near the grain boundary is controlled, which solves the problem of decreased plasticity of metastable β titanium alloys when increasing yield strength in the prior art, and realizes the preparation of high-strength and high-plasticity titanium alloy components.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HUANGHUAI UNIV
- Filing Date
- 2024-04-26
- Publication Date
- 2026-07-24
AI Technical Summary
Existing technologies often sacrifice plasticity while improving the yield strength of metastable β-titanium alloys, and their high preparation cost and complex strengthening methods limit their application and development.
By performing solid solution treatment in the α+β dual-phase region and combining it with water quenching, the precipitation of the α phase near the grain boundary is controlled, avoiding grain coarsening, ensuring that the grain core is the β phase and the grain boundary is the α phase, thereby improving the phase stability of the β phase.
It significantly improves yield strength while ensuring plasticity, is simple to operate and low in cost, and has a wide range of applications. It solves the problems of complex and high cost of existing strengthening methods and realizes the preparation of high-strength and high-plasticity titanium alloy components.
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Figure CN118422093B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of titanium alloy strengthening and toughening technology, specifically relating to a method for improving the strength and plasticity of metastable β titanium alloys. Background Technology
[0002] With the increasing demand for lightweight aerospace and marine equipment, the development of novel structural materials with high specific strength and excellent strength-ductility synergy is becoming increasingly urgent. However, the strength and ductility of metallic structural materials often present a trade-off, facing a pressing strength-ductility dilemma that limits their development in the materials field. Currently, metastable β-titanium alloys, with their excellent cold and hot forming capabilities, deep hardenability, and good corrosion resistance, have been widely used in aerospace, marine, and petrochemical industries.
[0003] Metastable β-titanium alloys have attracted widespread attention due to the low phase stability of the β phase, which leads to twin-induced plasticity and transformation-induced plasticity. This unique deformation mechanism induces a dynamic Hall-Page effect during plastic deformation, resulting in unexpected work hardening capabilities and enabling them to largely overcome the traditional strength-ductility dilemma. Currently, the strengthening methods for metastable β-titanium alloys of a given composition are mainly precipitation phase strengthening or hot working combined with precipitation phase strengthening. Compared with precipitation phase strengthening, the method of strengthening the microstructure by controlling the precipitation phase through hot working is more cumbersome and has a narrow processing window, thus greatly increasing the processing cost. Therefore, strengthening the mechanical properties of alloys by controlling the precipitation phase alone is more practically feasible.
[0004] To date, studies have shown that improving the yield strength of metastable β-titanium alloys through α-phase precipitation or low-temperature short-time aging to ω-phase precipitation is an effective strengthening method. However, while increasing the yield strength of metastable β-titanium alloys through α-phase precipitation, it is accompanied by a significant reduction in elongation due to the substantial suppression of stress-induced twinning / stress-induced martensite effects. Low-temperature short-time aging to ω-phase precipitation faces challenges such as a short heat treatment window and the potential for rapid embrittlement of metastable β-titanium alloys if the precipitation temperature or time is not precisely controlled. Therefore, existing strengthening strategies for improving yield strength severely limit the application and development of metastable β-titanium alloys.
[0005] In summary, how to optimize the microstructure of metastable β-titanium alloys with existing compositions through novel processing methods, so as to significantly improve their yield strength while maintaining their excellent plasticity and achieve an ideal strength-plasticity match, has become a key problem that urgently needs to be solved in this field. Summary of the Invention
[0006] In order to overcome the shortcomings of the prior art, the present invention aims to provide a method for improving the strength and plasticity of metastable β titanium alloys. This method effectively improves the strength and plasticity of metastable β titanium alloys by regulating the precipitation of α phase. It can solve the problems that existing metastable β titanium alloys sacrifice plasticity while improving yield strength, and have high preparation costs and complex strengthening methods.
[0007] Another objective of this invention is to provide a titanium alloy component processed using the above method.
[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:
[0009] A method for improving the strength and ductility of metastable β-titanium alloys includes the following steps:
[0010] (1) The metastable β titanium alloy with equiaxed β structure is solution treated in the α+β two-phase region; the solution treatment temperature is 20℃~50℃ below the β phase transformation point.
[0011] (2) The metastable β titanium alloy after solution treatment is subjected to water quenching. After water quenching, a titanium alloy component with β phase in the grain core and α phase precipitated at the grain boundaries is obtained.
[0012] Further, in step (1), the average grain size of the metastable β-titanium alloy is 100 μm to 200 μm. By controlling the grain size of the metastable β-titanium alloy, it is ensured that its grain size is within a suitable range that can activate the stress-induced twinning plasticity effect.
[0013] Furthermore, in step (1), the thickness of the metastable β-titanium alloy is greater than 2 mm.
[0014] This invention is not specifically targeted at the alloy composition system of metastable β titanium alloys. The method and toughening approach of this invention are applicable to different types of metastable β titanium alloys in this field. More preferably, in step (1), the metastable β titanium alloy is composed of one of Ti-8.5Cr-1.5Sn and Ti-4Mo-3Cr-1Fe.
[0015] Further, in step (1), the solution treatment is carried out in a muffle furnace; the solution treatment is carried out after the muffle furnace reaches the required temperature, and then the metastable β titanium alloy is placed into the muffle furnace for solution treatment.
[0016] By controlling the temperature and time of the solution treatment, grain coarsening can be avoided, and the precipitation of the α phase at and near the grain boundaries can be quantitatively controlled. Further, in step (1), the solution treatment time is 5 min to 50 min.
[0017] Furthermore, in step (2), the time interval from the end of the solution treatment to the start of the water quenching treatment is less than 3 seconds.
[0018] Furthermore, when the metastable β-titanium alloy has a composition of Ti-8.5Cr-1.5Sn, the solution treatment temperature is 680℃~710℃ and the time is 30min~45min.
[0019] Furthermore, when the metastable β-titanium alloy has a composition of Ti-4Mo-3Cr-1Fe, the solution treatment temperature is 720℃~750℃ and the time is 4min~7min.
[0020] A titanium alloy component processed using the above method.
[0021] Compared with the prior art, the present invention has the following beneficial technical effects:
[0022] The method for improving the strength and plasticity of metastable β-titanium alloys provided by this invention involves controlling the solution treatment process conditions to perform solution treatment on the metastable β-titanium alloy in the α+β dual-phase region. This, combined with subsequent water quenching, effectively avoids grain coarsening and quantitatively controls the precipitation of the α-phase at and near grain boundaries, resulting in a microstructure where the grain core is composed of the β-phase and the grain boundaries contain α-precipitates. The redistribution of alloying elements caused by the precipitation of the α-phase at the grain boundaries increases the phase stability of the β-phase, thus raising the critical shear stress for stress-induced deformation twins at the grain boundaries. Since there is no α-phase precipitation inside the grains, the β-phase remains metastable, maintaining its ability to induce a large number of deformation twins. Taking Ti-8.5Cr-1.5Sn titanium alloy as an example, processing the metastable Ti-8.5Cr-1.5Sn titanium alloy using the method of this invention can increase its yield strength from 478 MPa to 636 MPa, an increase of 33.1%, while its elongation at break only decreases from 49% to 47%, remaining almost unchanged. Furthermore, taking Ti-4Mo-3Cr-1Fe titanium alloy as an example, processing the metastable Ti-4Mo-3Cr-1Fe alloy using the method of this invention can increase its yield strength to 681 MPa, its tensile strength to 961 MPa, and its elongation only decreases by 7%.
[0023] As can be seen, the method provided by this invention, which improves the phase stability of the β phase near the grain boundaries through solution treatment of the α+β dual-phase region, can significantly increase the yield strength of metastable β titanium alloys while ensuring that the original twin-induced plasticity / phase transformation-induced plasticity effect is not suppressed. This effectively solves the technical problem that existing metastable β titanium alloys sacrifice plasticity while increasing yield strength. Furthermore, the method of this invention has the advantages of simple operation, low cost, and wide applicability, and can solve the problems of high preparation cost and complex strengthening methods in existing preparation methods. Therefore, the method of this invention is highly competitive in strengthening and toughening metastable β titanium alloys and has broad application prospects in the preparation of high-strength, high-toughness, high-quality titanium alloy components. Attached Figure Description
[0024] Figure 1 These are SEM images of the microstructure of the metastable titanium alloy components (Ti-8.5Cr-1.5Sn) obtained from Embodiment 1 and Comparative Examples 1 and 2 of this invention.
[0025] Figure 2 The uniaxial tensile property curves are for the metastable titanium alloy components (Ti-8.5Cr-1.5Sn) obtained in Embodiment 1 and Comparative Examples 1 and 2 of this invention.
[0026] Figure 3 The images show the microstructure of the metastable β-titanium alloy components (Ti-4Mo-3Cr-1Fe) obtained in Example 2 and Comparative Examples 3 and 4 of this invention, as shown in the SEM images.
[0027] Figure 4 The uniaxial tensile property curves are those corresponding to the metastable β titanium alloy components (Ti-4Mo-3Cr-1Fe) obtained by processing in Embodiment 2 and Comparative Examples 3 and 4 of the present invention. Detailed Implementation
[0028] The technical solution of the present invention will be further described below with reference to specific embodiments, but this does not constitute a limitation on the present invention. Unless otherwise specified, the test materials involved in the following embodiments and experimental examples can be obtained through conventional commercial channels.
[0029] In the following embodiments, the present invention uses Ti-8.5Cr-1.5Sn titanium alloy (wt.%) and Ti-4Mo-3Cr-1Fe titanium alloy (wt.%) as examples to illustrate the specific implementation method and beneficial effects of the present invention. It should be noted that the present invention is not particularly targeted at alloy composition systems, and the method of the present invention is also applicable to other metastable β titanium alloys other than those in the embodiments. It can also significantly improve the yield strength while ensuring that the original twin-induced plasticity / phase transformation-induced plasticity effect is not suppressed.
[0030] In the following examples, the average grain size of the metastable β-titanium alloy is 100 μm to 200 μm.
[0031] Example 1
[0032] This embodiment provides a method for improving the strength and plasticity of metastable β-titanium alloys, taking Ti-8.5Cr-1.5Sn titanium alloy as an example, and specifically includes the following steps:
[0033] Step (1): The metastable β titanium alloy sample with equiaxed β structure was subjected to uniaxial tensile treatment in the α+β two-phase region by muffle furnace, and the solution treatment temperature was controlled at 700℃ and the solution treatment time was 40min.
[0034] The uniaxial tensile sample has a composition of Ti-8.5Cr-1.5Sn, a β phase transformation temperature of 745℃, an average grain size of 141.7μm, a sample thickness of 2mm, and the dimensions of the parallel portion of the uniaxial tensile sample are 5mm×2mm×2mm. The solution treatment should ensure that the muffle furnace reaches the predetermined temperature within 2 minutes, and the sample should be placed in the muffle furnace for solution treatment after the predetermined temperature is reached.
[0035] Step (2): The metastable β titanium alloy after solution treatment is immediately subjected to water quenching within an interval of 3 seconds to obtain a titanium alloy tensile component with β phase in the grain core and α phase precipitated at the grain boundaries.
[0036] Example 2
[0037] This embodiment provides a method for improving the strength and ductility of metastable β-titanium alloys, taking Ti-4Mo-3Cr-1Fe titanium alloy as an example, and specifically includes the following steps:
[0038] Step (1): The metastable β titanium alloy sample with equiaxed β structure was subjected to uniaxial tensile treatment in the α+β two-phase region by muffle furnace, and the solution treatment temperature was controlled at 740℃ and the solution treatment time was 5min.
[0039] The uniaxial tensile sample has a composition of Ti-4Mo-3Cr-1Fe, a phase transformation temperature of 759℃, an average grain size of 155.6μm, a sample thickness of 2mm, and the dimensions of the parallel portion of the uniaxial tensile sample are 5mm×2mm×2mm. The solution treatment should ensure that the muffle furnace recovers to the predetermined temperature within 2 minutes, and the sample is placed in the muffle furnace for solution treatment only after the predetermined temperature is reached.
[0040] Step (2): The metastable β titanium alloy after solution treatment is immediately subjected to water quenching within an interval of 3 seconds to obtain a titanium alloy tensile component with β phase in the grain core and α phase precipitated at the grain boundaries.
[0041] Comparative Example 1
[0042] The comparative example provides a metastable β titanium alloy (Ti-8.5Cr-1.5Sn) with an equiaxed β structure, i.e., the original metastable β titanium alloy without processing.
[0043] Comparative Example 2
[0044] This comparative example provides a method for processing a metastable β titanium alloy. The alloy composition and steps (1) are the same as in Example 1. The only difference is that in step (2), the metastable β titanium alloy after solution treatment is air-cooled to room temperature, and then placed back into a muffle furnace and heated to 700°C for 3 minutes and immediately water-quenched to eliminate the isothermal ω phase generated during air cooling and prevent the mechanical properties from becoming embrittled due to the isothermal ω phase. Thus, the titanium alloy sample of this comparative example is obtained.
[0045] Comparative Example 3
[0046] The comparative example provides a metastable β titanium alloy (Ti-4Mo-3Cr-1Fe) with an equiaxed β structure, i.e., the original metastable β titanium alloy without processing.
[0047] Comparative Example 4
[0048] This comparative example provides a method for preparing a metastable β titanium alloy. The alloy composition and step (2) are the same as in Example 2. The only difference between the two is that in step (1), the solid solution temperature is 700℃ and the solid solution time is 40min. The rest of the process is the same as in Example 2, and a titanium alloy with α phase microstructure precipitated at both grain boundaries and within the grains is obtained.
[0049] Experimental Example 1
[0050] Scanning electron microscopy (SEM) analysis was performed on the three metastable Ti-8.5Cr-1.5Sn alloys of the same specifications obtained in Example 1, Comparative Example 1, and Comparative Example 2. Figure 1 The SEM microstructures of the metastable Ti-8.5Cr-1.5Sn titanium alloys obtained in Embodiment 1 and Comparative Examples 1-2 of this invention after undergoing different process treatments are shown.
[0051] in, Figure 1 (a) is a SEM image of the original titanium alloy (Ti-8.5Cr-1.5Sn) with equiaxed β structure in Comparative Example 1. The image shows that the original titanium alloy has equiaxed β grains and low β stability within and at the grain boundaries. Figure 1 (b) is a SEM image of the microstructure of the Ti-8.5Cr-1.5Sn alloy processed by the method of the present invention in Example 1 of the present invention. The image shows that the α phase precipitates along the grain boundaries, while the β phase is in the grain center. Figure 1(c) is a SEM image of the microstructure of the Ti-8.5Cr-1.5Sn alloy prepared in Comparative Example 2. The image shows that the α phase precipitates simultaneously at grain boundaries and within grains. It is evident that different processing methods result in significant differences in the microstructure and phase distribution of the obtained titanium alloys.
[0052] Uniaxial tensile tests were further conducted on the three metastable Ti-8.5Cr-1.5Sn alloys of the same specifications prepared in Example 1, Comparative Example 1, and Comparative Example 2. The test results of yield strength and elongation at break are as follows: Figure 2 And as shown in Table 1.
[0053] Table 1
[0054] Example 1 (700-40min + water cooling) 636 47 Comparative Example 1 (Original) 478 49 Comparative Example 2 (700-40min + air cooling) 760 31
[0055] Depend on Figure 2 As shown in Table 1, the yield strength of the tensile sample treated using the method of the present invention is 636 MPa, and the elongation at break is 47%. Compared with the original microstructure of Comparative Example 1, the yield strength is increased by 33.1%, while the elongation at break is only decreased by 2%, exhibiting excellent strength-plasticity matching. This allows the metastable β-titanium alloy to significantly improve its yield strength while ensuring that the original twin-induced plasticity effect is not suppressed.
[0056] Experimental Example 2
[0057] This experimental example presents scanning electron microscopy (SEM) analysis of three metastable Ti-4Mo-3Cr-1Fe alloys of the same specifications obtained in Example 2, Comparative Example 3, and Comparative Example 4. Figure 3 These are SEM microstructure images of the three metastable Ti-4Mo-3Cr-1Fe titanium alloys finally obtained in Example 2 and Comparative Examples 3-4 of this invention.
[0058] in, Figure 3 (a) is a SEM image of the microstructure of the original titanium alloy (Ti-4Mo-3Cr-1Fe) with equiaxed β structure in Comparative Example 3. The image shows that the original titanium alloy has equiaxed β grains and low β stability within and at the grain boundaries. Figure 3 (b) is a SEM image of the microstructure of the Ti-4Mo-3Cr-1Fe alloy obtained in Example 2 of the present invention. The image shows that the α phase precipitates along the grain boundaries, while the β phase is in the grain center. Figure 3 (c) is a SEM image of the microstructure of the Ti-4Mo-3Cr-1Fe alloy obtained from Comparative Example 4. The image shows that the α phase precipitates simultaneously at grain boundaries and within grains, exhibiting high β stability both within and at grain boundaries. It is evident that different processing methods result in significant differences in the microstructure and phase distribution of the obtained titanium alloys.
[0059] Uniaxial tensile tests were further conducted on the three metastable Ti-4Mo-3Cr-1Fe alloys of the same specifications obtained in Example 2, Comparative Example 3, and Comparative Example 4. The test results of yield strength, tensile strength, and elongation at break are as follows: Figure 4 And as shown in Table 2.
[0060] Table 2
[0061] Example 1 (740℃-5min) 681 961 38.2 Comparative Example 1 (Original) 620 924 45 Comparative Example 2 (700℃-40min) 858 869 13
[0062] Depend on Figure 4 As shown in Table 2, using the method of this invention, the yield strength of the treated tensile sample increased to 681 MPa relative to the original microstructure, and the tensile strength increased to 961 MPa relative to the original microstructure. The elongation was 38.2%, a decrease of only 7%, exhibiting excellent strength-plasticity matching. This allows the metastable β-titanium alloy to significantly improve its yield strength while ensuring that the original twin-induced plasticity effect is not suppressed.
[0063] In summary, the method for improving the strength and plasticity of metastable β-titanium alloys provided by this invention, through solution treatment of the metastable β-titanium alloy in the α+β dual-phase region combined with subsequent water quenching, can avoid grain coarsening and quantitatively control the precipitation of the α phase at and near grain boundaries, thereby obtaining a microstructure in which the grain core is composed of the β phase and the grain boundaries are composed of α precipitates. The redistribution of alloying elements caused by the precipitation of the α phase at the grain boundaries increases the phase stability of the β phase, thus increasing the critical shear stress for stress-induced deformation twins at the grain boundaries. Since there is no precipitation of the α phase inside the grains, the β phase remains metastable, thus maintaining its ability to induce a large number of deformation twins. Experiments have confirmed that the method provided by this invention, which improves the phase stability of the β phase near the grain boundaries through solution treatment of the α+β dual-phase region, can significantly increase the yield strength of metastable β-titanium alloys while ensuring that the original twin-induced plasticity / phase transformation-induced plasticity effect is not suppressed, effectively solving the technical problem that existing metastable β-titanium alloys sacrifice plasticity while increasing yield strength. Furthermore, the method of this invention has advantages such as simple operation, low cost, and wide applicability, and can solve the problems of high preparation cost and complex strengthening methods in existing preparation methods. Therefore, the method of this invention is highly competitive in strengthening and toughening metastable β-titanium alloys and has broad application prospects in the preparation of high-strength, high-toughness, high-quality titanium alloy components.
[0064] The above description is merely illustrative of the technical concept of this invention and should not be construed as limiting the scope of protection of this invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.
Claims
1. A method for improving the strength and plasticity of metastable β-titanium alloys, characterized in that, Includes the following steps: (1) The metastable β titanium alloy with equiaxed β structure is subjected to solid solution treatment in the α+β two-phase region; the solid solution treatment temperature is 20℃~50℃ below the β phase transformation point; (2) The metastable β titanium alloy after solution treatment is subjected to water quenching. After water quenching, a titanium alloy component with β phase in the grain core and α phase precipitated at the grain boundaries is obtained. In step (1), the average grain size of the metastable β titanium alloy is 100μm~200μm; the composition of the metastable β titanium alloy is one of Ti-8.5Cr-1.5Sn and Ti-4Mo-3Cr-1Fe; and the solution treatment time is 5min~50min.
2. The method for improving the strength and plasticity of metastable β-titanium alloy according to claim 1, characterized in that, In step (1), the thickness of the metastable β-titanium alloy is greater than 2 mm.
3. The method for improving the strength and plasticity of metastable β-titanium alloy according to claim 1 or 2, characterized in that, In step (1), the solution treatment is carried out in a muffle furnace; the solution treatment is carried out after the muffle furnace reaches the required temperature, and then the metastable β titanium alloy is placed into the muffle furnace for solution treatment.
4. The method for improving the strength and plasticity of metastable β-titanium alloy according to claim 1 or 2, characterized in that, In step (2), the time interval from the end of the solution treatment to the start of the water quenching treatment is less than 3 seconds.
5. The method for improving the strength and plasticity of metastable β-titanium alloy according to claim 1 or 2, characterized in that, When the metastable β-titanium alloy has a composition of Ti-8.5Cr-1.5Sn, the solution treatment temperature is 680℃~710℃ and the time is 30min~45min.
6. The method for improving the strength and plasticity of metastable β-titanium alloy according to claim 1 or 2, characterized in that, When the metastable β-titanium alloy has a composition of Ti-4Mo-3Cr-1Fe, the solution treatment temperature is 720℃~750℃ and the time is 4min~7min.
7. A titanium alloy component prepared by the method described in any one of claims 1 to 6.