High-strength titanium alloy composite material and preparation method thereof

Abstract

The invention discloses a high-strength titanium alloy composite material and a preparation method thereof, and belongs to the technical field of titanium metal materials. The high-strength titanium alloy composite material comprises the following chemical components: 5.5-7.1 wt% of Al, 1.5-2.5 wt% of Zr, 0.5-2.0 wt% of Mo, 0.8-2.5 wt% of V, 0.8-1.2 wt% of B, 1-2 wt% of Nb, less than or equal to 0.25 wt% of Fe, less than or equal to 0.15 wt% of Si, less than or equal to 0.10 wt% of C, less than or equal to 0.015 wt% of H, less than or equal to 0.15 wt% of O and the balance of Ti. When the high-strength titanium alloy composite material is prepared, firstly, metal raw material powder corresponding to all chemical components is weighed, then smelting, ingot casting and forging are carried out to obtain a bar, then the bar is subjected to electrode induction smelting gas atomization and electron beam powder bed melting, finally, primary heat treatment and secondary heat treatment are sequentially carried out, and the high-strength titanium alloy composite material is obtained. The high-strength titanium alloy composite material prepared by the preparation method disclosed by the invention has relatively good mechanical properties.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of titanium metal materials, in particular to a high-strength titanium alloy composite material and a preparation method thereof. BACKGROUND

[0002] Titanium alloys are widely used in aerospace, biomedical, chemical equipment and other high-end manufacturing fields due to their excellent specific strength, good corrosion resistance and high temperature stability. Among them, TA15 alloy (Ti-6Al-2Zr-1Mo-1V) as a near-alpha titanium alloy has good thermal strength and process performance, and plays an important role in aerospace structures. However, with the increasing demand for lightweight and high load capacity of modern aircraft, the traditional TA15 alloy gradually shows limitations in strength, stiffness and high temperature service performance, especially under high stress or complex load conditions, its comprehensive mechanical properties are difficult to meet the needs of new generation equipment.

[0003] In order to break this bottleneck, researchers generally use the composite strategy in recent years, which introduces high-hardness and high-modulus reinforcing phase to improve the mechanical properties of titanium matrix. Among them, titanium diboride (TiB2) is considered as a potential reinforcing body due to its extremely high melting point, excellent hardness, good chemical stability and similar thermal expansion coefficient with titanium matrix. More importantly, TiB2 can react with titanium in situ to generate one-dimensional TiB whiskers at high temperature, which not only has good interface compatibility with the matrix, but also effectively hinders dislocation movement and grain boundary sliding, thereby significantly improving the strength and stiffness of the material.

[0004] Previous studies have shown that adding appropriate amount of TiB2 particles in TA15 alloy can realize the synergistic effect of fine-grain strengthening, dispersion strengthening and load transfer effect through in-situ synthesis of TiB reinforcing phase, which can improve the strength and improve the plasticity or delay the plasticity decline to some extent. However, the addition amount, distribution uniformity and interface bonding state of TiB2 and the matrix have a decisive influence on the final performance of the composite material. If not properly controlled, it is easy to lead to aggregation of brittle phase, increase of porosity or deterioration of processing performance, which in turn weakens the comprehensive performance of the material. Therefore, how to optimize the introduction method and process parameters of TiB2 to realize the synergistic improvement of high strength and good plasticity has become a key technical difficulty in the research of titanium alloy composite materials.

[0005] Therefore, it is urgent to develop a preparation process of a high-strength titanium alloy composite material using TiB2 as a reinforcing phase suitable for TA15 alloy to solve the above problems. SUMMARY

[0006] The purpose of the present application is to provide a high-strength titanium alloy composite material and a preparation method thereof to solve the technical problems mentioned in the background.

[0007] The technical scheme for achieving the object of the present application is as follows: In a first aspect, a high-strength titanium alloy composite material has the following chemical composition: Al 5.5-7.1 wt%, Zr 1.5-2.5 wt%, Mo 0.5-2.0 wt%, V 0.8-2.5 wt%, B 0.8-1.2 wt%, Nb 1-2 wt%, Fe ≤0.25 wt%, Si ≤0.15 wt%, C ≤0.10 wt%, H ≤0.015 wt%, O ≤0.15 wt%, and Ti as the balance.

[0008] Further, in the preparation of the high-strength titanium alloy composite material, the metal raw material powders corresponding to the chemical components are weighed first, then melted, cast into ingots, forged into rods, and then subjected to electrode induction melting gas atomization and electron beam powder bed melting, and finally subjected to first heat treatment and second heat treatment in sequence.

[0009] In a second aspect, a preparation method of the high-strength titanium alloy composite material according to the first aspect includes the following steps: (1) weighing the metal raw material powders corresponding to the chemical components; (2) melting and casting the weighed metal raw material powders into ingots; (3) forging the ingots obtained in step (2) into rods; (4) subjecting the rods obtained in step (3) to electrode induction melting gas atomization to obtain titanium alloy powders; (5) subjecting the titanium alloy powders obtained in step (4) to electron beam powder bed melting to obtain a titanium alloy blank; (6) subjecting the titanium alloy blank obtained in step (5) to first heat treatment; (7) subjecting the titanium alloy blank treated in step (6) to second heat treatment to obtain the high-strength titanium alloy composite material.

[0010] Further, the melting adopts arc melting, and the number of arc melting is at least 1.

[0011] Further, the first heat treatment has a heat treatment temperature of 650-700℃ and a heat treatment duration of 110-120 min, and the cooling mode is air cooling.

[0012] Further, the second heat treatment adopts a cyclic heat treatment process.

[0013] Further, in the cyclic heat treatment process, a single heat treatment cycle step is as follows: first heating to 900-1000℃ for heat treatment and then cooling to 700-800℃.

[0014] Further, the heating rate is 9~10℃ / min, and the cooling rate is 4~5℃ / min.

[0015] Further, the time length of the heat treatment is 9~11min.

[0016] Further, the cycle number of the cycle heat treatment is 2~6 times.

[0017] By adopting the technical scheme, the application has the following beneficial effects: (1) The application takes sponge iron, high-purity aluminum, sponge zirconium, aluminum molybdenum alloy powder, aluminum vanadium alloy powder, metallic niobium powder and titanium diboride powder as metal raw material powder, first, ingredients are weighed according to the following chemical composition: Al 5.5~7.1wt%, Zr 1.5~2.5wt%, Mo 0.5~2.0wt%, V 0.8~2.5wt%, B 0.8~1.2wt%, Nb 1~2wt%, Fe≤0.25wt%, Si≤0.15wt%, C≤0.10wt%, H≤0.015wt%, O≤0.15wt%, Ti is the balance; then, bar stock is obtained through smelting, ingot casting and forging; then, the bar stock is subjected to electrode induction smelting gas atomization and electron beam powder bed melting; finally, the first heat treatment and the second heat treatment are sequentially performed to obtain the high-strength titanium alloy composite material, which has good strength and plasticity.

[0018] (2) The application introduces titanium diboride and metallic niobium on the basis of TA15 alloy, titanium diboride reacts with the titanium matrix in situ during high-temperature smelting to generate TiB whiskers, which can effectively bear external load and hinder dislocation movement as the main reinforcing phase, thereby improving the strength; however, if the TiB whiskers are thickened or poorly combined with the matrix interface, they are easy to become crack initiation sources and damage plasticity; the introduction of metallic niobium not only produces solid solution strengthening in the α-Ti matrix, but more importantly, significantly improves the interface compatibility and bonding strength between TiB and the titanium matrix; Nb atoms are segregated at the TiB / matrix interface, reducing the interface energy and inhibiting interface debonding, thereby improving the load transfer efficiency; Nb has a regulating effect on the stacking fault energy in the titanium alloy, and its ability to stabilize the stacking fault structure promotes the proliferation of dislocations and the formation of a high-density dislocation network during deformation, effectively improving the strength of the titanium alloy composite material, and through the pinning effect, the thickening behavior of the TiB whiskers during high-temperature treatment is effectively inhibited, realizing the refinement and uniform distribution of the TiB whiskers; the synergistic effect of the small, dispersed and well-bonded TiB whiskers and the high-density dislocation structure induced by Nb enhances the titanium alloy composite material while avoiding the brittleness problem caused by traditional ceramic reinforcing phases, so that the obtained high-strength titanium alloy composite material has excellent strength and good plasticity.

[0019] (3) The present application adopts arc melting, and the number of arc melting is at least 1, preferably, the number of arc melting is at least 2. Through repeated melting, not only can the high-melting-point components be effectively promoted to be fully dissolved and dispersed, but also macrosegregation can be significantly reduced, so that the key strengthening elements such as B and Nb can form fine TiB whiskers in the titanium matrix. In addition, repeated melting helps to partially escape gas impurities, reduces the inclusion content, thereby improving the purity and density of the ingot, and ensuring the uniformity of the alloy composition and the consistency of the organization.

[0020] (4) The titanium alloy blank obtained by electron beam powder bed melting is subjected to first heat treatment. Due to the existence of severe local melting and rapid solidification in the additive manufacturing process, significant residual stress is generated inside the blank, which is easy to cause deformation, cracking or affect the subsequent processing and service performance. Through first heat treatment, stress relief annealing can be carried out to effectively relax thermal stress and organizational stress, and at the same time, grain overgrowth or adverse phase structure transformation can be avoided.

[0021] (5) The second heat treatment adopts a cyclic heat treatment process combined with the introduction of TiB and metallic niobium. The cyclic heat treatment promotes the repeated nucleation and refinement of the alpha phase, forms a uniform and fine basket organization, effectively relieves stress concentration and improves the deformation coordination ability. On the other hand, the Nb element is solid-solved in the alpha-Ti matrix, not only enhances the lattice distortion strengthening effect, but also inhibits the rapid slip of dislocations by stabilizing the dislocation structure, promotes the uniform distribution of dislocations, thereby delaying local necking and improving plasticity. While maintaining high strength, the plasticity of the titanium alloy composite material is significantly improved. DETAILED DESCRIPTION

[0022] In order to better understand the above technical solutions, the above technical solutions will be described in detail below in combination with specific embodiments.

[0023] Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor belong to the scope of protection of the present application.

[0024] The following examples are only used to more clearly illustrate the technical solutions of the present application, and cannot be used to limit the protection scope of the present application.

[0025] The metal raw material powder is commercially available, including sponge iron, high-purity aluminum, sponge zirconium, aluminum-molybdenum alloy powder, aluminum-vanadium alloy powder, metallic niobium powder, and titanium diboride powder.

[0026] Example 1 A preparation method of a high-strength titanium alloy composite material, the preparation steps comprising: (1) Weigh the metal raw material powders corresponding to the following chemical compositions: Al 5.5wt%, Zr 1.5wt%, Mo 0.5wt%, V 0.8wt%, B 0.8wt%, Nb 1wt%, Fe ≤ 0.25wt%, Si ≤ 0.15wt%, C ≤ 0.10wt%, H ≤ 0.015wt%, O ≤ 0.15wt%, Ti as balance; (2) The weighed metal raw material powder was ball-milled at 50 rpm for 8 hours, pressed into a consumable electrode with dimensions of 300×60×60 mm, and installed in a consumable electrode vacuum arc melting furnace. The vacuum degree in the furnace before melting was <5×10 -5 Pa was subjected to two electric arc melting processes to obtain an ingot with a diameter of 170 mm. (3) Polish the surface of the ingot obtained in step (2), heat it to 1050°C in a high-temperature furnace and hold it for 2 hours, then use a fast forging machine to forge the 170mm ingot into a 100mm bar, then grind the surface of the bar to remove the oxide scale, heat it to 950°C in a high-temperature furnace and hold it for 2 hours, then use a radial forging machine to forge the 100mm bar to a diameter of 45mm, and then machine the bar into a bar with a diameter of 41mm×400mm and a conical end. (4) The rod obtained in step (3) is subjected to electrode induction melting gas atomization to obtain titanium alloy powder; (5) The titanium alloy powder obtained in step (4) is melted by electron beam powder bed. First, the substrate is preheated to 700~800℃ by electron beam, so that the temperature of the entire printing chamber also reaches 700~800℃. Then, a thin layer of composite powder is spread on the substrate by powder spreading roller, and electron beam defocusing preheating is performed layer by layer to reduce the residual stress generated during the solidification and cooling of the molten layer. The preheating parameters are: current 30mA, electron beam scanning speed 1m / s, voltage 60kV. Then, the preheated layer is subjected to electron beam focusing melting scan, with scanning current of 10~16.5mA, scanning speed of 4~6m / s, layer thickness of 0.05mm, spacing of 0.1mm, and electron beam focusing diameter of 120μm. During the printing process, the vacuum degree in the forming chamber is maintained at 10~5mBar to obtain the titanium alloy blank. (6) The titanium alloy blank obtained in step (5) is subjected to heat treatment at 650℃ for 120 min for the first time; (7) The titanium alloy blank processed in step (6) is subjected to a cyclic heat treatment process to obtain a high-strength titanium alloy composite material. The single heat treatment cycle steps in the cyclic heat treatment process are as follows: first, heat treatment is performed at 9℃ / min to 900℃, and then the temperature is reduced to 700℃ at 4℃ / min. The number of cyclic heat treatment cycles is 2.

[0027] Example 2 A method for preparing a high-strength titanium alloy composite material, comprising the following steps: (1) Weigh the metal raw material powders corresponding to the following chemical compositions: Al 6.3wt%, Zr 2wt%, Mo 1wt%, V 1wt%, B 1wt%, Nb 2wt%, Fe ≤ 0.25wt%, Si ≤ 0.15wt%, C ≤ 0.10wt%, H ≤ 0.015wt%, O ≤ 0.15wt%, Ti as balance; (2) The weighed metal raw material powder was ball-milled at 50 rpm for 8 hours, pressed into a consumable electrode with dimensions of 300×60×60 mm, and installed in a consumable electrode vacuum arc melting furnace. The vacuum degree in the furnace before melting was <5×10 -5 Pa was subjected to two electric arc melting processes to obtain an ingot with a diameter of 170 mm. (3) Polish the surface of the ingot obtained in step (2), heat it to 1050°C in a high-temperature furnace and hold it for 2 hours, then use a fast forging machine to forge the 170mm ingot into a 100mm bar, then grind the surface of the bar to remove the oxide scale, heat it to 950°C in a high-temperature furnace and hold it for 2 hours, then use a radial forging machine to forge the 100mm bar to a diameter of 45mm, and then machine the bar into a bar with a diameter of 41mm×400mm and a conical end. (4) The rod obtained in step (3) is subjected to electrode induction melting gas atomization to obtain titanium alloy powder; (5) The titanium alloy powder obtained in step (4) is melted by electron beam powder bed. First, the substrate is preheated to 700~800℃ by electron beam, so that the temperature of the entire printing chamber also reaches 700~800℃. Then, a thin layer of composite powder is spread on the substrate by powder spreading roller, and electron beam defocusing preheating is performed layer by layer to reduce the residual stress generated during the solidification and cooling of the molten layer. The preheating parameters are: current 30mA, electron beam scanning speed 1m / s, voltage 60kV. Then, the preheated layer is subjected to electron beam focusing melting scan, with scanning current of 10~16.5mA, scanning speed of 4~6m / s, layer thickness of 0.05mm, spacing of 0.1mm, and electron beam focusing diameter of 120μm. During the printing process, the vacuum degree in the forming chamber is maintained at 10~5mBar to obtain the titanium alloy blank. (6) The titanium alloy blank obtained in step (5) is subjected to heat treatment at 650℃ for 120 min for the first time; (7) The titanium alloy blank processed in step (6) is subjected to a cyclic heat treatment process to obtain a high-strength titanium alloy composite material. The single heat treatment cycle steps in the cyclic heat treatment process are as follows: first, heat treatment is performed at 9℃ / min to 950℃, and then the temperature is reduced to 750℃ at 4℃ / min. The number of cyclic heat treatment cycles is 4.

[0028] Example 3 A method for preparing a high-strength titanium alloy composite material, comprising the following steps: (1) Weigh the metal raw material powders corresponding to the following chemical compositions: Al 7.1wt%, Zr 2.5wt%, Mo 2.0wt%, V 2.5wt%, B 1.2wt%, Nb 2wt%, Fe≤0.25wt%, Si≤0.15wt%, C≤0.10wt%, H≤0.015wt%, O≤0.15wt%, Ti as balance; (2) The weighed metal raw material powder was ball-milled at 50 rpm for 8 hours, pressed into a consumable electrode with dimensions of 300×60×60 mm, and installed in a consumable electrode vacuum arc melting furnace. The vacuum degree in the furnace before melting was <5×10 -5 Pa was subjected to two electric arc melting processes to obtain an ingot with a diameter of 170 mm. (3) Polish the surface of the ingot obtained in step (2), heat it to 1050°C in a high-temperature furnace and hold it for 2 hours, then use a fast forging machine to forge the 170mm ingot into a 100mm bar, then grind the surface of the bar to remove the oxide scale, heat it to 950°C in a high-temperature furnace and hold it for 2 hours, then use a radial forging machine to forge the 100mm bar to a diameter of 45mm, and then machine the bar into a bar with a diameter of 41mm×400mm and a conical end. (4) The rod obtained in step (3) is subjected to electrode induction melting gas atomization to obtain titanium alloy powder; (5) The titanium alloy powder obtained in step (4) is melted by electron beam powder bed. First, the substrate is preheated to 700~800℃ by electron beam, so that the temperature of the entire printing chamber also reaches 700~800℃. Then, a thin layer of composite powder is spread on the substrate by powder spreading roller, and electron beam defocusing preheating is performed layer by layer to reduce the residual stress generated during the solidification and cooling of the molten layer. The preheating parameters are: current 30mA, electron beam scanning speed 1m / s, voltage 60kV. Then, the preheated layer is subjected to electron beam focusing melting scan, with scanning current of 10~16.5mA, scanning speed of 4~6m / s, layer thickness of 0.05mm, spacing of 0.1mm, and electron beam focusing diameter of 120μm. During the printing process, the vacuum degree in the forming chamber is maintained at 10~5mBar to obtain the titanium alloy blank. (6) The titanium alloy blank obtained in step (5) is subjected to heat treatment at 700℃ for 110 min for the first time. (7) The titanium alloy blank processed in step (6) is subjected to a cyclic heat treatment process to obtain a high-strength titanium alloy composite material. The single heat treatment cycle steps in the cyclic heat treatment process are as follows: first, heat treatment is performed at 10℃ / min to 1000℃, and then the temperature is reduced to 800℃ at 5℃ / min. The number of cyclic heat treatment cycles is 6.

[0029] Examples 4-5 The only difference between Examples 4 and 5 and Example 2 is that the number of cycles of cyclic heat treatment is 3 and 5, respectively.

[0030] Comparative Examples 1-5 The only difference between Comparative Examples 1-5 and Example 2 is that the Nb content in the high-strength titanium alloy composite material is 0 wt%, 0.6 wt%, 0.8 wt%, 2.2 wt%, and 2.4 wt%, respectively.

[0031] Comparative Example 6 The difference between Comparative Example 6 and Example 2 is that step (7) is deleted. The heat treatment is carried out by heating to 950°C at 10°C / min and holding for 2 hours, followed by cooling with the furnace.

[0032] Comparative Examples 7-9 The only difference between Examples 7-9 and Example 2 is that the number of cycles of cyclic heat treatment is 1, 7, and 8, respectively.

[0033] Example of effect Table 1 below shows the performance test results of the high-strength titanium alloy composite materials prepared in Examples 1-5 and Comparative Examples 1-9: Table 1

[0034] As shown in Table 1, the high-strength titanium alloy composite materials prepared in Examples 1-5 have both good strength and plasticity. The only difference between Examples 4-5 and Example 2 is that the number of cycles of cyclic heat treatment is 3 and 5, respectively. The only difference between Comparative Examples 1-5 and Example 2 is that the Nb content in the high-strength titanium alloy composite materials is 0wt%, 0.6wt%, 0.8wt%, 2.2wt%, and 2.4wt, respectively. The difference between Comparative Example 6 and Example 2 is that step (7) is deleted, and the heat treatment is carried out by heating to 950℃ at 10℃ / min and holding for 2 hours and then cooling with the furnace. The only difference between Examples 7-9 and Example 2 is that the number of cycles of cyclic heat treatment is 1, 7, and 8, respectively.

[0035] Experimental results show that, under the same processing conditions, the strength of the material continuously increases with the increase of Nb content, while the elongation at break shows a trend of first increasing and then decreasing. This indicates that Nb not only strengthens the matrix and improves the TiB / matrix interface bonding, but also promotes the uniform distribution of dislocations by stabilizing the stacking fault structure, thereby improving both strength and plasticity. However, when the Nb content is too high, the plasticity decreases, possibly due to the effect of excessive solid solution strengthening leading to the obstruction of dislocation movement. With a fixed Nb content, the cyclic heat treatment process of this invention maintains a basically stable material strength compared to the conventional heat treatment of Comparative Example 6, while the elongation at break... The significantly improved yield indicates that cyclic heat treatment effectively refined the α-phase microstructure, optimized the two-phase distribution, and alleviated the residual stress and microstructure inhomogeneity caused by additive manufacturing. Further analysis of the effect of the number of cycles shows that moderately increasing the number of cycles has little impact on strength but is beneficial to improving plasticity. However, when the number of cycles is too high, repeated thermal cycling may cause grain boundary weakening or α-phase coarsening, resulting in a significant decrease in strength. In summary, this invention, by introducing TiB reinforcing phase and metallic niobium into TA15 alloy and combining it with an optimized cyclic heat treatment secondary heat treatment process, successfully and significantly improved the plasticity of titanium alloy composite materials while maintaining high strength.

[0036] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-strength titanium alloy composite material, characterized in that, The chemical composition of the high-strength titanium alloy composite material is as follows: Al 5.5~7.1wt%, Zr 1.5~2.5wt%, Mo 0.5~2.0wt%, V 0.8~2.5wt%, B 0.8~1.2wt%, Nb 1~2wt%, Fe≤0.25wt%, Si≤0.15wt%, C≤0.10wt%, H≤0.015wt%, O≤0.15wt%, and Ti as the balance.

2. The high-strength titanium alloy composite material according to claim 1, characterized in that, In the preparation of the high-strength titanium alloy composite material, the metal raw material powders corresponding to each chemical composition are first weighed, and then smelted, cast into ingots, and forged to obtain bars. Next, the bars are subjected to electrode induction melting gas atomization and electron beam powder bed melting, and finally subjected to first heat treatment and second heat treatment in sequence.

3. A method for preparing a high-strength titanium alloy composite material as described in any one of claims 1 to 2, characterized in that, The preparation steps include: (1) Weigh the metal raw material powders corresponding to each chemical component; (2) Melt and cast the weighed metal raw material powder into ingots; (3) Forge the ingot obtained in step (2) into a bar; (4) The rod obtained in step (3) is subjected to electrode induction melting gas atomization to obtain titanium alloy powder; (5) The titanium alloy powder obtained in step (4) is subjected to electron beam powder bed melting to obtain a titanium alloy billet; (6) Perform the first heat treatment on the titanium alloy billet obtained in step (5); (7) The titanium alloy blank processed in step (6) is subjected to secondary heat treatment to obtain a high-strength titanium alloy composite material.

4. The method for preparing the high-strength titanium alloy composite material according to claim 3, characterized in that, The smelting process employs electric arc melting, and the electric arc melting is performed at least once.

5. The method for preparing the high-strength titanium alloy composite material according to claim 3, characterized in that, The initial heat treatment temperature is 650~700℃, the heat treatment duration is 110~120min, and the cooling method is air cooling.

6. The method for preparing the high-strength titanium alloy composite material according to claim 3, characterized in that, The secondary heat treatment employs a cyclic heat treatment process.

7. The method for preparing the high-strength titanium alloy composite material according to claim 6, characterized in that, The steps of a single heat treatment cycle in the cyclic heat treatment process are as follows: first, heat the temperature to 900~1000℃ for heat treatment, and then cool it down to 700~800℃.

8. The method for preparing the high-strength titanium alloy composite material according to claim 7, characterized in that, The heating rate is 9~10℃ / min, and the cooling rate is 4~5℃ / min.

9. The method for preparing the high-strength titanium alloy composite material according to claim 7, characterized in that, The duration of each heat treatment is 9 to 11 minutes.

10. The method for preparing the high-strength titanium alloy composite material according to claim 9, characterized in that, The number of cycles for the cyclic heat treatment is 2 to 6.

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