Titanium alloy preparation method for synergistically improving strength and plasticity and titanium alloy

Abstract

The invention belongs to the field of titanium alloy strengthening, and particularly discloses a titanium alloy preparation method for synergistically improving strength and plasticity and a titanium alloy, and the titanium alloy preparation method comprises the following steps: S1, carrying out heat treatment on the titanium alloy; s2, after the titanium alloy subjected to heat treatment is cooled to the room temperature, magnetic field treatment is conducted on the titanium alloy; and S3, aging treatment is conducted on the titanium alloy subjected to magnetic field treatment. According to the method, heat treatment, magnetic field treatment and aging treatment are combined, aging strengthening and the magnetoplastic effect are comprehensively utilized, the strength and plasticity of the titanium alloy are synergistically improved, the titanium alloy with matched toughness performance is further prepared, and the requirements of high-end equipment and the industrial field for the titanium alloy are met.

Description

Technical Field

[0001] The present invention belongs to the field of titanium alloy strengthening, and more specifically, relates to a titanium alloy preparation method and a titanium alloy capable of synergistically improving strength and plasticity. Background Art

[0002] Titanium alloy has the advantages of low density, high specific strength, good corrosion resistance and fatigue resistance. It is considered to be a lightweight high-strength structural material and one of the most important high-end materials in the industrial field. It has been widely used in high-performance and advanced engineering fields such as aerospace, ocean, military, nuclear power and biomedicine. However, while titanium alloy has high strength, its plasticity is low and difficult to form. The load-bearing process of industrial applications will directly affect the reliability, safety and service life of the alloy, and in severe cases will cause catastrophic damage. Therefore, it is necessary to develop titanium alloy materials with high strength and excellent plasticity to meet the needs of high-end equipment and engineering applications.

[0003] In order to improve the mechanical properties of titanium alloys, heat treatment has become an effective method and a popular way to improve the comprehensive mechanical properties of titanium alloys. Although the heat treatment system can significantly improve the strength of titanium alloys, the plasticity and toughness of the alloys have been significantly reduced. This method still cannot effectively improve the comprehensive mechanical properties of titanium alloys. Summary of the invention

[0004] In view of the above defects or improvement needs of the prior art, the present invention provides a titanium alloy preparation method and a titanium alloy with synergistically improved strength and plasticity, the purpose of which is to achieve synergistic improvement of the strength and plasticity of the titanium alloy.

[0005] To achieve the above object, according to one aspect of the present invention, a method for preparing a titanium alloy with synergistically improved strength and plasticity is proposed, comprising the following steps:

[0006] S1. heat treating the titanium alloy;

[0007] S2, after the titanium alloy that has completed the heat treatment is cooled to room temperature, subjecting it to magnetic field treatment;

[0008] S3. Perform aging treatment on the titanium alloy after magnetic field treatment.

[0009] As further preferred, in step S3, when performing aging treatment, the temperature is 450-650° C. and the insulation time is 2-8 hours.

[0010] As further preferred, in step S2, when the magnetic field treatment is performed, the magnetic field intensity is 0.5 to 12 T, and the magnetic field action time is 30 to 120 min.

[0011] As a further preference, in step S2, when performing magnetic field treatment, the magnetic field type is a pulsed magnetic field or a static magnetic field.

[0012] As further preferred embodiment, in step S1, the titanium alloy before heat treatment is obtained by forging, extrusion or rolling.

[0013] As a further preference, in step S2, when performing magnetic field treatment, the direction of the magnetic field is parallel or perpendicular to the deformation direction of the titanium alloy.

[0014] As a further preferred embodiment, step S1, heat treating the titanium alloy, specifically comprises:

[0015] Solution treatment of titanium alloy;

[0016] Or perform solution treatment and aging treatment on titanium alloy.

[0017] As further preferred, in step S1, the solution treatment is β-phase solution treatment or (α+β)-phase solution treatment, wherein the temperature of the β-phase solution treatment is 30-100°C above the β-phase transformation temperature, and after keeping warm for 10-30 minutes, it is air-cooled or water-quenched to room temperature; the temperature of the (α+β)-phase solution treatment is 30-60°C below the β-phase transformation temperature, and after keeping warm for 30-120 minutes, it is air-cooled or water-quenched to room temperature.

[0018] As further preferred, in step S1, the aging treatment temperature is 200-450°C, and after keeping the temperature for 2-24 hours, the mixture is air-cooled or water-quenched to room temperature.

[0019] According to another aspect of the present invention, there is provided a titanium alloy prepared by the above-mentioned method for preparing a titanium alloy for synergistically improving strength and plasticity.

[0020] In general, the above technical solution conceived by the present invention has the following technical advantages compared with the prior art:

[0021] 1. The present invention preliminarily improves the strength of titanium alloy through conventional heat treatment, and then effectively combines magnetic field treatment and aging treatment, thereby performing aging strengthening on the basis of the magnetoplastic effect produced by magnetic field treatment, thereby achieving a synergistic improvement in the strength and toughness of titanium alloy, thereby obtaining a titanium alloy with matched strength and toughness, meeting the demand for titanium alloys in high-end equipment and industrial fields.

[0022] 2. When titanium alloy is treated with magnetic field, the magnetic field can transform free radical pairs from the ground state to the excited state, reduce the resistance between dislocation and obstacle, promote the dislocation to be unpinned from the pinning point, and increase the flexibility of dislocation movement. In addition, the magnetic field can promote atomic diffusion, increase the spacing of slip planes, reduce the critical shear stress of dislocation movement, promote dislocation movement, increase dislocation density, significantly improve the plasticity of the alloy, and produce magneto-plastic effect.

[0023] Then, aging treatment is carried out after magnetic field treatment: the dislocation density increased by magnetic field treatment can provide energy and precipitation sites for the subsequent precipitation of polymorphic and diffusely distributed secondary α phase during aging; at the same time, the thermal energy during aging treatment can provide energy and accelerate the diffusion rate of atoms; these two factors promote the precipitation of α phase and increase the content of α phase and α / β phase interface.

[0024] Therefore, the combination of magnetic field and aging can promote the precipitation of α phase, increase the number of α / β phase interfaces, and refine the grains. The α / β interface can hinder the movement of dislocations, causing high-density dislocations to accumulate at the interface, thereby strengthening the alloy; at the same time, the α / β interface can serve as an effective dislocation source, promoting plastic deformation by generating dislocations, thereby improving plasticity. For the increased α phase, the activation cone<c+a> Slip can provide five independent slip systems to coordinate the deformation along the crystal c axis and promote plastic deformation. In addition, the primary α phase (α p ) can be preserved in the magnetic field and aging process, micron or submicron α p It can coordinate deformation and improve plasticity.

[0025] 3. The present invention performs high-temperature aging after magnetic field treatment, which can provide energy and promote the transformation of metastable phase or β phase into α phase; S3 aging transforms the metastable phase into α phase, which can avoid the existence of brittle and hard metastable phase and reduce the impact on the plasticity of titanium alloy. Magnetic field treatment of titanium alloy at room temperature can better promote the precipitation of micron-level α phase, increase dislocation density, thereby improving plasticity and showing magneto-plastic effect. At the same time, it can avoid the complex process involving multiple effects, multiple scales and multiple mechanisms of coupling of magnetic field and heating process, which brings convenience to the study of alloy strengthening and toughening mechanism and law, and reduces equipment cost.

[0026] 4. Furthermore, the present invention performs high-temperature, short-time aging at 450-650°C for 2-8h after the magnetic field. If aging is performed in step S1, the metastable phase in S1 can be further converted into an α phase, and a secondary α phase with a larger content and a smaller size is precipitated. If aging is not performed in step S1, the high-temperature aging in S3 can convert the metastable phase of the titanium alloy after solid solution treatment into an α phase, promote the phase change process, and increase the α phase content.

[0027] 5. Furthermore, the present invention designs the magnetic field strength. When the magnetic field strength is small, the effect on increasing the dislocation density is limited, which leads to limited effect of subsequent aging treatment and difficulty in matching the strength and toughness of titanium alloy. When the magnetic field strength is too large, the magnetic field equipment is forced to become large-scale and the requirements for the equipment are extremely strict. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a flow chart of a method for preparing a titanium alloy with synergistically improved strength and plasticity according to an embodiment of the present invention;

[0029] Figure 2 The microstructures of Ti-6554 alloys in different states according to the embodiments of the present invention are shown in Figure 1, wherein (a) is solid solution, (b) is solid solution + magnetic field, (c) is solid solution + aging, and (d) is solid solution + magnetic field + aging.

[0030] Figure 3 is the engineering stress-strain curve of the titanium alloy of the embodiment of the present invention;

[0031] Figure 4 This is a diagram of the mechanical properties of the titanium alloy according to an embodiment of the present invention;

[0032] Figure 5 This is the average Schmidt factor diagram of the α phase of the Ti-6554 alloy after solid solution + magnetic field and solid solution + magnetic field + aging treatment in an embodiment of the present invention. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0034] The embodiment of the present invention provides a method for preparing a titanium alloy with synergistically improved strength and plasticity, such as Figure 1 As shown, the following steps are included:

[0035] S1. heat treating the titanium alloy;

[0036] S2, after the titanium alloy that has completed the heat treatment is cooled to room temperature, subjecting it to magnetic field treatment;

[0037] S3. Perform aging treatment on the titanium alloy after magnetic field treatment.

[0038] Further, in step S1, heat treatment is performed on the titanium alloy, specifically:

[0039] Solution treatment of titanium alloy;

[0040] Or perform solution treatment and aging treatment on titanium alloy.

[0041] Among them, solution treatment: the forged, extruded or rolled titanium alloy is heated to the solution temperature with the furnace, and the sample is taken out after being kept at the solution temperature for a certain period of time and cooled to room temperature. Solution treatment is divided into β phase and (α+β) phase solution treatment, in which the temperature of β phase solution treatment is 30-100℃ above the β phase transformation temperature, the holding time is 10-30min, and air cooling or water quenching is performed to room temperature; the temperature of (α+β) phase solution treatment is 30-60℃ below the β phase transformation temperature, the holding time is 30-120min, and air cooling or water quenching is performed to room temperature.

[0042] Aging treatment: After the heating furnace is heated to the predetermined aging temperature, the solution-treated titanium alloy is placed in the heating furnace for a certain period of time, then taken out and cooled to room temperature. The aging treatment temperature is 200-450°C, the holding time is 2-24h, preferably 12-24h, and air-cooled or water-quenched to room temperature.

[0043] After solution treatment, titanium alloy forms a metastable titanium alloy. After aging treatment, polymorphic and dispersed secondary α phases are precipitated, forming more α / β phase interfaces, effectively hindering dislocation movement and strengthening the alloy. In addition, the aging setting in S1 is low temperature and long time aging, which is equivalent to pre-aging, which can better precipitate the metastable phase.

[0044] Furthermore, step S2 of magnetic field treatment includes: placing the titanium alloy in a magnetic field device for magnetic field treatment for a certain period of time and then taking it out. The magnetic field intensity of the magnetic field treatment is 0.5 to 12T, preferably 9 to 12T, and the magnetic field action time is 30 to 120min; in some embodiments, the magnetic field intensity may be 9T, 10T, 11T, 12T, and the magnetic field action time may be 30min, 60min, 90min, 120min. The magnetic field type is a pulsed magnetic field or a static magnetic field, and the direction of the magnetic field is parallel or perpendicular to the plastic deformation direction of the sample before solution treatment.

[0045] Furthermore, step S3 aging treatment includes: placing the sample treated by the magnetic field in a heating furnace at a predetermined temperature for a certain period of time, taking it out, and cooling it to room temperature. The aging temperature is 450-650°C, the insulation time is 2-8 hours, and air cooling or water quenching is performed to room temperature. In some embodiments, the aging temperature can be 450, 500°C, 550°C, 600°C, 650°C, and the insulation time can be 2 hours, 4 hours, 6 hours, or 8 hours.

[0046] The following are specific embodiments:

[0047] A forged metastable β titanium alloy (Ti-6554) with a length of 40 mm × width of 15 mm × height of 20 mm was subjected to conventional heat treatment, magnetic field treatment, and aging treatment after magnetic field pretreatment. The conventional heat treatment was performed before the magnetic field treatment. Specifically, the following steps were included:

[0048] A. Solution treatment: The forged Ti-6554 titanium alloy is subjected to (α+β) phase solution treatment. The forged Ti-6554 titanium alloy is heated to 740°C in a furnace and kept for 1 hour, then the sample is taken out and air-cooled to room temperature.

[0049] B. Magnetic field treatment: The solid solution Ti-6554 titanium alloy is placed in a nuclear magnetic resonance spectrometer with a magnetic field strength of 11.7 T for 1 hour. The direction of the magnetic field is vertical, parallel to the deformation direction of the forged Ti-6554 titanium alloy, that is, the length direction.

[0050] C. Aging treatment: The Ti-6554 titanium alloy sample that has undergone solid solution and magnetic field treatment is placed in a heating furnace for high-temperature aging treatment. The aging temperature is 600°C and the insulation time is 6 hours. After the aging process is completed, the sample is taken out and air-cooled to room temperature.

[0051] The Ti-6554 titanium alloy samples after solution treatment, magnetic field treatment and aging treatment were subjected to X-ray diffraction, scanning electron microscopy (SEM), electron backscatter diffraction detection and mechanical property tests. Table 1 lists the dislocation density of Ti-6554 titanium alloy after solution treatment, solution + magnetic field treatment and solution + magnetic field + aging treatment. After solution treatment, the dislocation density of Ti-6554 titanium alloy increased from 1.05×10 14 m -2 Increased to 1.25×10 14 m -2 The reason is that magnetic field treatment can reduce the resistance between dislocations and obstacles, promote dislocations to be unpinned from pinning points, promote dislocation movement, and increase the flexibility of dislocation movement; in addition, the magnetic field can promote atomic diffusion, increase the spacing of slip planes, reduce the critical shear stress of dislocation movement, promote dislocation movement, and increase dislocation density. After magnetic field treatment, aging treatment is carried out. The higher dislocation density of magnetic field treatment can provide diffusion channels and energy for atomic diffusion, promote the precipitation of secondary α phase during aging, consume part of dislocations, and reduce dislocation density. The high temperature and long-term heat preservation of aging treatment can provide energy for the movement of dislocations, increase the mobility of dislocations, and accelerate the interaction between dislocations. When dislocations of opposite signs meet on the same slip plane, they will attract each other, promote the rearrangement and mutual annihilation of dislocations, and reduce dislocation density.

[0052] Table 1 Dislocation density

[0053]

[0054] SEM images of Ti-6554 titanium alloy after solid solution, solid solution + aging, solid solution + magnetic field, and solid solution + magnetic field + aging treatment are shown in the figure below. Figure 2As shown in Table 2, the average size and volume fraction of the α phase are shown in Table 2. As can be seen from Table 2, the size and volume fraction of the α phase treated by solid solution + magnetic field are increased compared with those treated by solid solution. The reason is that the magnetic field provides energy, accelerates atomic diffusion and phase transformation, and promotes the coarsening and precipitation of the α phase. After solid solution + magnetic field + aging treatment, the size of the α phase decreases, but the volume fraction increases. The reason is that the dislocation density increased by the magnetic field treatment can provide energy and precipitation sites for the subsequent aging precipitation of the α phase. At the same time, the thermal energy during the aging treatment can provide energy and accelerate the diffusion rate of atoms; these two factors promote the precipitation of the α phase, increase the α phase content, and refine the α phase size. While increasing the α phase content, the α / β phase interface is also increased, which has the effect of refining the grains and strengthening the alloy.

[0055] Table 2 Average size and volume fraction of α phase

[0056]

[0057] Figure 3 and Figure 4 The engineering stress-strain curves and mechanical properties of Ti-6554 titanium alloy after solid solution, solid solution + aging, solid solution + magnetic field, and solid solution + magnetic field + aging are shown in Table 3. The corresponding mechanical properties data are shown in Table 3. As can be seen from Table 3, the elongation of magnetic field treatment after solid solution is about 30% higher than that of solid solution treatment, showing a significant magnetoplastic effect, but the strength is also significantly reduced. After solid solution, combined with magnetic field and aging treatment, the tensile strength and elongation at break of solid solution + magnetic field + aging treatment are about 14% and 21% higher than those of solid solution treatment alone.

[0058] Table 3 Mechanical properties

[0059]

[0060] Figure 3 and Figure 4 The comprehensive mechanical properties of Ti-6554 titanium alloy treated with solid solution + magnetic field + aging are shown to be improved in strength and plasticity compared with conventional heat treatment (solid solution or solid solution + aging). The reasons are as follows: the magnetic field increases the dislocation density, promotes the precipitation of α phase in the subsequent aging process, increases the content of α phase and α / β phase interface, and plays a strengthening effect of grain boundary strengthening, dislocation strengthening and interface strengthening, such as Figure 2 In addition, the α / β interface can act as an effective dislocation source, promoting plastic deformation by generating dislocations, thereby improving plasticity; the primary α phase (α p ) can be preserved in the magnetic field and aging process, micron or submicron α p Can coordinate deformation and improve plasticity; for α phase, activate the cone surface<c+a> Slip, such as Figure 5As shown in Figure 1, five independent slip systems can be provided to coordinate the deformation along the crystal c-axis and promote plastic deformation. The above factors synergistically improve the strength and plasticity of Ti-6554 titanium alloy.

[0061] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a titanium alloy that synergistically improves strength and plasticity, characterized in that: The steps include: S1. heat treating the titanium alloy; S2, after the titanium alloy that has completed the heat treatment is cooled to room temperature, subjecting it to magnetic field treatment; S3. Perform aging treatment on the titanium alloy after magnetic field treatment.

2. The method for preparing a titanium alloy with synergistically improved strength and plasticity according to claim 1, characterized in that: In step S3, when performing aging treatment, the temperature is 450-650° C. and the insulation time is 2-8 hours.

3. The method for preparing a titanium alloy with synergistically improved strength and plasticity according to claim 1, characterized in that: Step S2, when performing magnetic field treatment, the magnetic field intensity is 9 to 12 T, and the magnetic field action time is 30 to 120 minutes.

4. The method for preparing a titanium alloy with synergistically improved strength and plasticity according to claim 1, characterized in that: Step S2, when performing magnetic field processing, the magnetic field type is a pulse magnetic field or a static magnetic field.

5. The method for preparing a titanium alloy with synergistically improved strength and plasticity according to claim 1, characterized in that: Step S1, the titanium alloy before heat treatment is obtained by forging, extrusion or rolling.

6. The method for preparing a titanium alloy with synergistically improved strength and plasticity as claimed in claim 5, characterized in that: In step S2, when performing magnetic field treatment, the direction of the magnetic field is parallel or perpendicular to the deformation direction of the titanium alloy.

7. The method for preparing a titanium alloy with synergistically improved strength and plasticity according to any one of claims 1 to 6, characterized in that: Step S1, heat treating the titanium alloy, specifically: Solution treatment of titanium alloy; Or perform solution treatment and aging treatment on titanium alloy.

8. The method for preparing a titanium alloy with synergistically improved strength and plasticity according to claim 7, characterized in that: Step S1, the solution treatment is β-phase solution treatment or (α+β)-phase solution treatment, wherein the temperature of the β-phase solution treatment is 30-100°C above the β-phase transformation temperature, and after keeping warm for 10-30 minutes, it is air-cooled or water-quenched to room temperature; the temperature of the (α+β)-phase solution treatment is 30-60°C below the β-phase transformation temperature, and after keeping warm for 30-120 minutes, it is air-cooled or water-quenched to room temperature.

9. The method for preparing a titanium alloy with synergistically improved strength and plasticity according to claim 7, characterized in that: Step S1, the aging treatment temperature is 200-450°C, and after keeping the temperature for 2-24 hours, the mixture is air-cooled or water-quenched to room temperature.

10. A titanium alloy, characterized in that: The titanium alloy is prepared by the method for preparing a titanium alloy for synergistically improving strength and plasticity as described in any one of claims 1 to 9.

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