A high-performance low-cost titanium alloy with easy cold workability and heat treatable strengthening and a preparation method thereof

Abstract

This invention provides a high-performance, low-cost titanium alloy that is easily cold-workable and heat-treatable, and its preparation method, belonging to the field of titanium alloy preparation technology. By mass percentage, it contains the following components: Cr 3.5~7%, Mo 1~3%, Al 0~1.7%, Zr 0~0.8%, Fe 0~1%, with the balance being Ti and unavoidable impurities, wherein Al, Zr, and Fe are not simultaneously zero. By rationally controlling the content and ratio of each alloying element, and after processing and heat treatment, the annealed alloy exhibits a room temperature fracture elongation exceeding 40%, a strength of approximately 800 MPa, a work hardening rate of approximately 7.5 MPa / %, and excellent cold-working performance; after aging, the strength reaches approximately 1000 MPa, and the fracture elongation exceeds 10%, making it suitable for heat treatment strengthening. Simultaneously, this alloy does not contain expensive elements such as V and Nb, and has a low Mo content, resulting in low raw material costs, achieving a balance between high performance and low cost.

Description

Technical Field

[0001] This invention relates to the field of titanium alloy preparation technology, and in particular to a high-performance, low-cost titanium alloy that is easy to cold work and can be strengthened by heat treatment, and its preparation method. Background Technology

[0002] Titanium alloys are characterized by their low density (approximately 4.5 g / cm³). 3 High specific strength, excellent corrosion resistance, heat resistance, and biocompatibility make titanium alloys promising for applications in aerospace, biomedicine, chemical engineering, automotive, and marine engineering. The ability to perform cold working processes (cold rolling, cold heading, cold drawing, deep drawing, etc.) to achieve extremely high material utilization and dimensional accuracy is a core indicator for measuring the industrial value and application breadth of metallic materials. However, most titanium alloys have low room temperature plasticity and are prone to cracking during cold working, making it difficult to manufacture high-precision thin-walled parts, tubes, springs, and fasteners through cold forming (such as cold rolling, cold heading, cold spinning, cold drawing, etc.). Industrially widely used titanium alloys are mostly α+β titanium alloys, such as Ti-6Al-4V and Ti-3Al-2.5V, with strengths typically greater than 900 MPa, but low room temperature elongation at break. 15% elongation at break, unsuitable for cold working. Industrial pure titanium (such as TA1) has a room temperature elongation at break of over 30%, allowing for cold working such as deep drawing (e.g., cold stamping of titanium cups). However, its strength is relatively low, typically only 200-300 MPa at room temperature, which is insufficient to meet the strength requirements of industrial applications. Currently, the industry urgently needs low-cost titanium alloys that can be cold-worked (elongation greater than 40%) while maintaining a strength of approximately 800 MPa to meet the needs of applications such as fasteners, springs, and thin-walled tubing.

[0003] Currently, titanium alloys with room temperature elongation exceeding 40% generally contain large amounts of expensive elements such as V and Nb, and little or no Al (for example, the Ti-35Nb-9Zr-7Sn-0.3O alloy [Acta Materialia, 2026, 304: 121812] has a room temperature fracture elongation of up to 41% and a strength of approximately 600 MPa). This is because V and Nb are β-phase stabilizing elements, while Al is a strong α-stabilizing element; a stable β-phase in the alloy can significantly improve room temperature plasticity. Large amounts of V and Nb not only increase raw material costs but also significantly increase the alloy's specific gravity, weakening the lightweight advantage of titanium alloys.

[0004] In summary, existing titanium alloy systems struggle to simultaneously achieve excellent cold-working properties, high strength, and low raw material costs. There is an urgent need to develop a new type of titanium alloy: one that exhibits room-temperature elongation exceeding 40% during processing, demonstrating excellent cold-working performance; an alloy strength exceeding 800 MPa; and one that avoids the excessive addition of expensive β-phase stabilizing elements (such as V and Nb) and minimizes the addition of high-density alloying elements (such as Mo and Zr) to control raw material costs and maintain a lightweight advantage. Summary of the Invention

[0005] The purpose of this invention is to provide a high-performance, low-cost titanium alloy that is easy to cold work and can be strengthened by heat treatment, and a method for preparing the same, so as to solve the problem that existing titanium alloys cannot simultaneously achieve excellent processing performance, high performance and low raw material cost.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a high-performance, low-cost titanium alloy that is easy to cold work and can be strengthened by heat treatment, comprising the following components by mass percentage: Cr 3.5~7%, Mo 1~3%, Al 0~1.7%, Zr 0~0.8%, Fe 0~1%, with the balance being Ti and unavoidable impurities, wherein Al, Zr and Fe are not simultaneously 0.

[0007] This invention also provides a method for preparing a high-performance, low-cost titanium alloy that is easy to cold work and can be strengthened by heat treatment, comprising the following steps: 1) Weigh the raw materials according to the raw material ratio, melt them under vacuum or protective atmosphere, and obtain alloy ingots after cooling; 2) The alloy ingot is processed and then annealed to obtain the annealed alloy; 3) The annealed alloy is subjected to aging treatment to obtain the aged alloy.

[0008] Furthermore, the melting is carried out in a vacuum electric arc furnace, a magnetic levitation furnace, a consumable furnace, or a vacuum induction furnace.

[0009] Furthermore, in step 2), the annealing temperature is 700~1000℃ and the annealing time is ≥10min.

[0010] Furthermore, the processing includes hot processing or cold processing. The hot processing includes one or more of hot rolling, hot forging and hot extrusion. The heat treatment temperature is 700~1000℃ to obtain billets of different shapes.

[0011] Furthermore, the cold working process includes one or more of cold rolling, cold drawing, cold heading, and cold extrusion. When the deformation of the cold working process exceeds 30%, intermediate annealing is required, and the annealing temperature is 700~1000℃.

[0012] Furthermore, in step 3), the aging treatment temperature is 550~700℃, and the aging treatment time is ≥1h.

[0013] The beneficial effects of this invention are: (1) This invention reduces the β phase transformation temperature by rationally adjusting the content and ratio of alloy elements. After annealing, the alloy can be rapidly cooled to obtain a single β phase with a strength of about 800 MPa, excellent plasticity (room temperature fracture elongation ≥ 40%), and a work hardening rate of about 7.5 MPa / %, which is very suitable for cold working.

[0014] (2) After the annealed alloy is processed and formed, it can be further strengthened by aging heat treatment, with a strength of about 1000MPa and a fracture elongation of more than 10%.

[0015] (3) The titanium alloy of the present invention does not contain high-valence elements such as V and Nb, resulting in lower raw material costs; the content of high-specific-weight elements such as Mo and Zr is also low, and will not significantly increase the specific gravity of the titanium alloy. Therefore, the titanium alloy of the present invention has the advantage of low cost. Attached Figure Description

[0016] Figure 1 The figures show the room temperature tensile stress-strain curves of the annealed and aged alloys in Example 3 of this invention.

[0017] Figure 2 This is the microstructure of the annealed and aged alloy in Example 3 of the present invention. Detailed Implementation

[0018] This invention provides a high-performance, low-cost titanium alloy that is easy to cold work and can be strengthened by heat treatment, comprising the following components by mass percentage: Cr 3.5~7%, Mo 1~3%, Al 0~1.7%, Zr 0~0.8%, Fe 0~1%, with the balance being Ti and unavoidable impurities, wherein Al, Zr and Fe are not simultaneously 0.

[0019] In this invention, the following components are included by weight percentage: Cr 4.0~6.5%, Mo 1.5~3%, Al 0.5~1.5%, Zr 0~0.5%, Fe 0.4~1%, with the balance being Ti and unavoidable impurities, wherein Al, Zr and Fe are not simultaneously 0.

[0020] In this invention, Cr is a β-phase stabilizing element, significantly reducing the β-transformation temperature and effectively improving the solid solution strengthening effect of the alloy. However, excessive Cr can lead to the formation of brittle intermetallic compounds, impairing the alloy's plasticity. Therefore, the Cr mass percentage is controlled at 3.5~7%.

[0021] Mo provides solid solution strengthening, increasing alloy strength. It is also a β-phase stabilizing element, improving alloy plasticity. However, excessive Mo will increase alloy cost and density. Therefore, the Mo mass percentage should be controlled between 1% and 3%.

[0022] Zr can improve the strength of alloys but reduce their plasticity. Excessive Zr will significantly increase the cost and specific gravity of the alloy. Therefore, the Zr mass percentage should be controlled between 0% and 0.8%.

[0023] Fe is an inexpensive and strong β-phase stabilizing element that can significantly improve the strength and cold / hot working properties of alloys, and has a high annealing strengthening effect. However, Fe also easily forms brittle intermetallic compounds, and excessive addition will significantly reduce the plasticity of the alloy. Therefore, the Fe mass percentage should be controlled at 0~1%.

[0024] Al is an α-phase stabilizing element, effectively promoting the precipitation of the α-phase during aging, thereby improving the alloy's strength. Furthermore, Al has a lower density than Ti, and adding Al can reduce the specific gravity of titanium alloys. However, when the Al content is too high, the α-phase precipitates in the annealed alloy, significantly reducing its room-temperature plasticity and cold workability. Simultaneously, excessive Al may also form brittle intermetallic compounds with Ti and other elements, further impairing the alloy's ductility and toughness. Therefore, the Al mass percentage should be controlled between 0% and 1.7%.

[0025] This invention also provides a method for preparing a high-performance, low-cost titanium alloy that is easy to cold work and can be strengthened by heat treatment, comprising the following steps: 1) Weigh the raw materials according to the raw material ratio, melt them under vacuum or protective atmosphere, and obtain alloy ingots after cooling; 2) The alloy ingot is processed and then annealed to obtain the annealed alloy; 3) The annealed alloy is subjected to aging treatment to obtain the aged alloy.

[0026] In this invention, the melting is carried out in a vacuum arc furnace, a magnetic levitation furnace, a consumable furnace, or a vacuum induction furnace, preferably in a vacuum arc furnace.

[0027] In this invention, in step 2), the annealing temperature is 700~1000℃, preferably 750~950℃, and more preferably 800~900℃; the annealing time is ≥10min, preferably 15~60min.

[0028] In this invention, the processing includes hot processing or cold processing. The hot processing includes one or more of hot rolling, hot forging and hot extrusion, preferably hot rolling. The temperature of the heat treatment is 700~1000℃, preferably 750~950℃, and more preferably 800~900℃, to obtain billets of different shapes.

[0029] In this invention, the cold working process includes one or more of cold rolling, cold drawing, cold heading and cold extrusion, preferably cold rolling; when the deformation of the cold working process exceeds 30%, intermediate annealing is required, and the annealing temperature is 700~1000℃, preferably 750~950℃, and more preferably 800~900℃.

[0030] In this invention, in step 3), the aging treatment temperature is 550~700℃, preferably 600~650℃; the aging treatment time is ≥1h, preferably 2~20h.

[0031] In this invention, the annealed alloy has a room temperature fracture elongation of over 40%, a strength of approximately 800 MPa, and a work hardening rate of approximately 7.5 MPa / ; the aged alloy has a strength of approximately 1000 MPa and a fracture elongation of over 10%.

[0032] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0033] Example 1

[0034] Metal raw materials with a purity ≥ 99.5% are prepared according to the following alloy composition (mass percentage): Cr: 5.5%, Mo: 3.0%, Al: 1.0%, Zr: 0.5%, Fe: 0.4%, with the remainder being Ti and unavoidable impurities.

[0035] Raw materials are weighed according to the raw material ratio, melted and mixed evenly in an electric arc melting furnace under a protective atmosphere to obtain alloy ingots.

[0036] The alloy ingot was hot-rolled at 950℃ to a reduction of ~85%, and the hot-rolled titanium sheet was annealed at 800℃ for 20 minutes and then rapidly cooled to room temperature to obtain the annealed alloy. The annealed alloy can be cold-worked at room temperature, and no cracks were observed when it was cold-rolled at room temperature to a reduction of about ~40%.

[0037] The annealed alloy was aged at 600℃ for 8 hours and then air-cooled to room temperature to obtain an aged titanium alloy.

[0038] The annealed alloy has a yield strength of 550 MPa, a tensile strength of 789 MPa, and an elongation after fracture of 48%; the aged alloy has a yield strength of 900 MPa and a tensile strength of 967 MPa, and an elongation after fracture of 10%.

[0039] Example 2

[0040] Metal raw materials with a purity ≥ 99.5% are prepared according to the following alloy composition (mass percentage): Cr: 6.0%, Mo: 3.0%, Al: 1.0%, Fe: 0.4%, with the remainder being Ti and unavoidable impurities.

[0041] Raw materials are weighed according to the raw material ratio, melted and mixed evenly in an electric arc melting furnace under a protective atmosphere to obtain alloy ingots.

[0042] The alloy ingot is hot-rolled at 950℃ to a reduction of ~85%. The hot-rolled titanium plate is annealed at 800℃ for 20 minutes and then rapidly cooled to room temperature to obtain the annealed alloy. After aging at 600℃ for 10 hours, it is air-cooled to room temperature to obtain the aged alloy.

[0043] The annealed alloy has a yield strength of 550 MPa, a tensile strength of 801 MPa, and an elongation after fracture of 46%; after aging, the alloy has a yield strength of 900 MPa and a tensile strength of 981 MPa, and an elongation after fracture of 11%.

[0044] Example 3

[0045] Metal raw materials are prepared using metals with a purity ≥ 99.5% according to the following alloy composition (mass percentage): Cr: 5.5%, Mo: 3.0%, Al: 1.0%, Zr: 0.5%, with the remainder being Ti and unavoidable impurities.

[0046] Raw materials are weighed according to the raw material ratio, melted and mixed evenly in an electric arc melting furnace under a protective atmosphere to obtain alloy ingots.

[0047] The alloy ingot is hot-rolled at 850℃ to a reduction of ~85%. The hot-rolled titanium plate is annealed at 800℃ for 20 minutes and then rapidly cooled to room temperature to obtain the annealed alloy. After aging at 600℃ for 8 hours, it is air-cooled to room temperature to obtain the aged titanium alloy.

[0048] Figure 1 The room temperature tensile curves of the alloy in the annealed and aged states of this embodiment are shown. The annealed alloy has a yield strength of 520 MPa, a tensile strength of 801 MPa, an elongation after fracture of 45%, a strain of 1%-38%, and a hardening rate of 7.4 MPa / s. The aged alloy has a yield strength of 950 MPa and a tensile strength of 1010 MPa, and an elongation after fracture of 12%.

[0049] Figure 2The microstructures of the annealed and aged alloys in this embodiment are shown. It is clear that the annealed alloy is a pure β alloy, while the aged alloy is an α+β two-phase alloy.

[0050] Comparative Example 1

[0051] Compared with Example 1, except that the Cr content in the raw materials is adjusted to 3% by mass, the other steps and conditions are exactly the same as in Example 1, that is, the Cr content is lower than the scope of the present invention.

[0052] The room temperature elongation after fracture of the annealed alloy obtained in Comparative Example 1 decreased to 30%, indicating that when the Cr content is lower than the range of the present invention, the alloy's plasticity and cold workability decrease.

[0053] Comparative Example 2

[0054] Compared with Example 1, except that the Cr content in the raw materials was adjusted to 8% by mass, the other steps and conditions were exactly the same as in Example 1, that is, the Cr content was higher than the scope of the present invention.

[0055] The room temperature elongation after fracture of the annealed alloy obtained in Comparative Example 2 decreased to 14%, indicating that when the Cr content is higher than the range of the present invention, the plasticity and cold workability of the alloy decrease.

[0056] Comparative Example 3

[0057] Compared with Example 1, except that the Al content in the raw materials was adjusted to 1.8% by mass, the other steps and conditions were exactly the same as in Example 1, that is, the Al content was higher than the scope of the present invention.

[0058] The room temperature elongation after fracture of the annealed alloy obtained in Comparative Example 3 was 29%, indicating that when the Al content is higher than the range of the present invention, the plasticity and cold workability of the alloy decrease.

[0059] Comparative Example 4

[0060] Compared with Example 1, except that the Mo content in the raw materials is adjusted to 0% by mass, the other steps and conditions are exactly the same as in Example 1, that is, the Mo content is lower than the scope of the present invention.

[0061] The room temperature elongation after fracture of the annealed alloy obtained in Comparative Example 4 decreased to 27%, indicating that when the Mo content is lower than the range of the present invention, the alloy's plasticity and cold workability decrease.

[0062] Comparative Example 5

[0063] Compared with Example 2, except that the Zr content in the raw materials was adjusted to 1% by mass, the other steps and conditions were exactly the same as in Example 2, that is, the Zr content was higher than that of the present invention.

[0064] The annealed alloy obtained in Comparative Example 5 has a yield strength of 520 MPa, a tensile strength of 823 MPa, and an elongation after fracture of 30%, indicating that when the Zr content is higher than the range of the present invention, the plasticity and cold workability decrease.

[0065] In summary, the room temperature elongation at break of the alloys exceeding the composition range specified in this invention is all below 35%, which increases the difficulty of cold working.

[0066] Table 1. Tensile properties of titanium alloys in annealed state in Examples 1-3 and Comparative Examples 1-5

[0067] Table 2. Tensile property data of titanium alloys in aged state in Examples 1-3

[0068] As can be seen from the above embodiments, the present invention provides a high-performance, low-cost titanium alloy that is easy to cold work and can be strengthened by heat treatment, and its preparation method. By rationally controlling the content and ratio of alloying elements Cr, Mo, Al, Zr, and Fe, and through processing and heat treatment, the annealed alloy exhibits a room temperature fracture elongation exceeding 40%, a strength of approximately 800 MPa, a work hardening rate of approximately 7.5 MPa / %, and excellent cold workability. After aging, the strength reaches approximately 1000 MPa, and the fracture elongation exceeds 10%, making it suitable for heat treatment strengthening. Furthermore, this alloy does not contain expensive elements such as V and Nb, and has a low Mo content, resulting in low raw material costs, thus achieving a balance between high performance and low cost.

[0069] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A high-performance, low-cost titanium alloy that is easily cold-workable and heat-treatable, characterized in that, By weight percentage, it contains the following ingredients: Cr 3.5~7%, Mo 1~3%, Al 0~1.7%, Zr 0~0.8%, Fe 0~1%, with the balance being Ti and unavoidable impurities, wherein Al, Zr and Fe are not simultaneously 0.

2. The method for preparing the high-performance, low-cost titanium alloy that is easily cold-workable and heat-treatable as described in claim 1, characterized in that, Includes the following steps: 1) Weigh the raw materials according to the raw material ratio, melt them under vacuum or protective atmosphere, and obtain alloy ingots after cooling; 2) The alloy ingot is processed and then annealed to obtain the annealed alloy; 3) The annealed alloy is subjected to aging treatment to obtain the aged alloy.

3. The preparation method according to claim 2, characterized in that, The melting is carried out in a vacuum electric arc furnace, magnetic levitation furnace, consumable furnace or vacuum induction furnace.

4. The preparation method according to claim 2 or 3, characterized in that, In step 2), the annealing temperature is 700~1000℃ and the annealing time is ≥10min.

5. The preparation method according to claim 4, characterized in that, The processing includes hot processing or cold processing. The hot processing includes one or more of hot rolling, hot forging and hot extrusion. The heat treatment temperature is 700~1000℃, resulting in billets of different shapes.

6. The preparation method according to claim 5, characterized in that, The cold working process includes one or more of cold rolling, cold drawing, cold heading and cold extrusion. When the deformation of the cold working process exceeds 30%, intermediate annealing is required, and the annealing temperature is 700~1000℃.

7. The preparation method according to claim 2 or 6, characterized in that, In step 3), the aging treatment temperature is 550~700℃ and the aging treatment time is ≥1h.

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