Multi-phase synergistically strengthened copper-titanium alloy and preparation method thereof

Abstract

The invention discloses a multiphase synergistically strengthened copper-titanium alloy, the microstructure of the copper-titanium alloy has the following nano-structures: a cellular structure, a nano laminated structure formed by alternately arranging beta-Cu4Ti phases and alpha-Cu matrix phases, the beta-Cu4Ti phases are lamellar or fibrous beta-Cu4Ti discontinuous precipitated phases, and the alpha-Cu matrix phases are lamellar or fibrous beta-Cu4Ti discontinuous precipitated phases; and the beta '-Cu4Ti continuous precipitated phase is uniformly distributed in the alpha-Cu matrix phase and is in a coherent or semi-coherent relationship with the alpha-Cu matrix phase. The invention further discloses a preparation method of the multiphase synergistically strengthened copper-titanium alloy. On the basis of the comprehensive requirements of the strength and the conductivity of the copper-titanium alloy, the Co element is added to regulate and control the interface energy of the precipitated phase, the distribution of the precipitated phase is optimized, a multi-step process of discontinuous precipitation aging, cold rolling deformation and continuous precipitation aging is combined, and the strength of the copper-titanium alloy is improved through interface strengthening, precipitated phase strengthening and heterostructure induction strengthening effects. And the comprehensive performance superior to that of the copper-titanium alloy prepared in a conventional mode can be achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of copper alloy materials, and in particular relates to a multi-phase synergistically strengthened copper-titanium alloy and a preparation method thereof. Background Art

[0002] Copper-beryllium alloys are widely used in circuit components, precision manufacturing, and electrical engineering due to their ultra-high strength and excellent electrical conductivity. However, beryllium's toxicity to the environment and human health has prompted the search for alternative materials with comparable performance and greater environmental safety.

[0003] Copper-titanium alloy is a typical precipitation-strengthened copper-titanium alloy. Its mechanical properties in the peak aging state are comparable to those of copper-beryllium alloy, and it has higher stress relaxation resistance. It is considered to be one of the ideal alternative materials to copper-beryllium alloy. However, due to the strong scattering effect of solid-dissolved Ti atoms on electrons, the electrical conductivity of copper-titanium alloy is relatively low, which seriously restricts the promotion and application of copper-titanium alloy. Adding alloying elements can improve this problem to a certain extent. For example, patent CN113005324A discloses a copper-titanium alloy and a preparation method thereof, and patent CN111733372A discloses an elastic copper-titanium alloy and a preparation method thereof. However, the above methods have limited synergistic effects on improving strength and conductivity, and the introduction of new components puts forward new requirements for production process and cost control. Therefore, it is necessary to develop a new universal method to prepare ultra-high-strength copper-titanium alloys with higher electrical conductivity. Summary of the Invention

[0004] In order to overcome the deficiencies of the prior art, the present invention provides a multiphase synergistically strengthened copper-titanium alloy and a preparation method thereof.

[0005] The technical solution adopted by the present invention to solve the technical problem is: a multiphase synergistically strengthened copper-titanium alloy, the copper-titanium alloy microstructure has the following nanostructure:

[0006] The cellular structure is composed of a β-Cu4Ti phase and an α-Cu matrix phase alternately arranged into a nano-laminated structure, wherein the β-Cu4Ti phase is a β-Cu4Ti discontinuous precipitated phase in the form of a sheet or fiber;

[0007] The β′-Cu4Ti continuous precipitate phase is evenly distributed in the α-Cu matrix phase and presents a coherent or semi-coherent relationship with the α-Cu matrix phase.

[0008] Furthermore, the thickness of the β-Cu4Ti phase is ≤100 nm; the average size of the β′-Cu4Ti continuous precipitated phase is 10±5 nm; and the volume fraction of the cellular structure is ≥80%.

[0009] Furthermore, the copper-titanium alloy has a Vickers hardness of ≥280 HV, a tensile strength of ≥1000 MPa, a conductivity of ≥24% IACS, and a product of strength and conductivity of ≥24000 MPa·% IACS.

[0010] Furthermore, the copper-titanium alloy element content, by mass percentage, is 1-5% Ti, 0-0.5% Co, and the rest is copper and unavoidable impurities.

[0011] Furthermore, the β-Cu4Ti discontinuous precipitation phase is elongated along the rolling direction after cold rolling deformation, forming a cross-scale multi-phase synergistic strengthening structure.

[0012] The present invention also discloses a method for preparing a multiphase synergistically strengthened copper-titanium alloy, comprising the following steps:

[0013] (1) Vacuum melting: According to the composition of copper-titanium alloy, weigh the alloy raw materials respectively and use vacuum induction melting method to obtain alloy ingots;

[0014] (2) Homogenization heat treatment: keep the ingot at 850~950℃ for 4~24h, and then cool it to room temperature with water;

[0015] (3) Hot rolling: The homogenized alloy is hot rolled at 850-950°C with a deformation of 70-80%, and then water-cooled to room temperature;

[0016] (4) Solution heat treatment: The hot-rolled alloy is kept at 850-950 °C for 1-4 h, and then water-cooled to room temperature;

[0017] (5) Discontinuous precipitation aging heat treatment: The alloy after solution heat treatment is kept at 450~550℃ for 2~120h, and then water-cooled to room temperature;

[0018] (6) Cold rolling: The alloy that has undergone discontinuous precipitation aging is cold rolled with a reduction greater than 80%;

[0019] (7) Continuous precipitation aging heat treatment: the cold-rolled alloy is heated to 300-500°C, kept at this temperature for 0.5-8 hours, and then water-cooled to room temperature to obtain the copper-titanium alloy.

[0020] Furthermore, in step (6), dislocation defects are introduced after cold rolling deformation to promote the nucleation of continuous precipitation phase.

[0021] Furthermore, in step (7), the continuous precipitation aging temperature and time satisfy the following relationship: when the temperature is ≤450°C, the holding time is ≥1h; when the temperature is >450°C, the holding time is <1h.

[0022] The present invention uses a copper-titanium alloy as the matrix, with Ti as the primary strengthening element, being the primary forming element of both the continuous and discontinuous precipitates. Co has a low solubility in copper and can refine grains. Furthermore, the reaction between Co and Ti to form a continuous precipitate helps optimize the distribution of the precipitate and provides precipitate strengthening. Excessive addition of Co is detrimental to the formation of discontinuous precipitates, so its content is controlled to 0-0.5%.

[0023] In the preparation process of the alloy of the present invention, the oxidation of the alloy raw materials is effectively suppressed by the vacuum melting method, reducing the deviation of the alloy composition. The combination of homogenization + hot rolling + solution heat treatment eliminates the segregation and aggregation problems in the cast alloy structure, and forms an equiaxed crystal structure, thereby improving the uniformity and thermal stability of the alloy structure. The combination of discontinuous precipitation aging heat treatment + cold rolling deformation + continuous precipitation aging heat treatment greatly reduces the concentration of solid solution elements, changes the spatial orientation of the discontinuous precipitation phase, provides a conductive path, and significantly improves the electrical conductivity of the alloy; at the same time, the discontinuous precipitation phase and its interface and the continuous precipitation phase between phases form a multi-phase synergistic strengthening structure, thereby achieving an increase in the strength of the alloy.

[0024] The beneficial effects of the present invention are as follows: based on the comprehensive requirements of strength and conductivity of copper-titanium alloy, the interfacial energy of the precipitate phase is regulated by adding the Co element, the distribution of the precipitate phase is optimized, and a multi-step process of discontinuous precipitation aging, cold rolling deformation and continuous precipitation aging is combined, and through interface strengthening, precipitation phase strengthening and heterogeneous structure induced strengthening effects, Vickers hardness ≥ 280HV, tensile strength ≥ 1000 MPa, conductivity ≥ 24%IACS, and the product of strength and conductivity ≥ 24000 MPa·%IACS can be achieved, which is superior to the comprehensive performance of copper-titanium alloy prepared by conventional methods, can replace toxic beryllium copper-titanium alloy, meet the future development needs of electronic information, transportation, aerospace and other industries, and have broad industrial application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a flow chart of a method for preparing a multiphase synergistically strengthened copper-titanium alloy according to the present invention.

[0026] Figure 2 SEM images of cold-rolled alloy plates.

[0027] Figure 3 TEM image of the alloy after continuous precipitation aging heat treatment. DETAILED DESCRIPTION

[0028] In order to enable those skilled in the art to better understand the solutions of the present invention, the following will provide a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0029] like Figure 1 As shown, the present invention provides a method for preparing a multiphase synergistically strengthened copper-titanium alloy, the method comprising the following steps:

[0030] (1) Vacuum melting: According to the composition of the copper-titanium alloy, the alloy raw materials are weighed separately and melted by vacuum induction melting to obtain alloy ingots; wherein the alloy raw materials are pure copper, pure titanium, pure cobalt or intermediate alloys containing alloy elements;

[0031] Specifically, the copper-titanium alloy element content is calculated by mass percentage, Ti is 1-5%, Co is 0-0.5%, and the rest is copper and unavoidable impurities;

[0032] Among them, the main regulating element Ti constructs a multi-level precipitation phase by forming β′-Cu4Ti and β-Cu4Ti phases; the secondary regulating element Co pins dislocations and regulates the interfacial energy of the precipitation phase in the form of CoTi2 phase and solute atoms;

[0033] (2) Homogenization heat treatment: keep the ingot at 850~950℃ for 4~24h, and then cool it to room temperature with water;

[0034] (3) Hot rolling: The homogenized alloy is hot rolled at 850-950℃ with a deformation of 70-80%, and then water-cooled to room temperature;

[0035] (4) Solution heat treatment: The hot-rolled alloy is kept at 850-950 °C for 1-4 h, and then water-cooled to room temperature;

[0036] (5) Discontinuous precipitation aging heat treatment: The alloy after solution heat treatment is kept at 450~550℃ for 2~120h, and then water-cooled to room temperature;

[0037] (6) Cold rolling: The alloy that has undergone discontinuous precipitation aging is cold rolled with a reduction greater than 80%. In this step, dislocation defects are introduced after cold rolling deformation, which promotes the nucleation of continuous precipitation phases.

[0038] (7) Continuous precipitation aging heat treatment: The cold-rolled alloy is heated to 300-500°C, held at this temperature for 0.5-8 hours, and then water-cooled to room temperature to obtain the copper-titanium alloy. In step (7), the continuous precipitation aging temperature and time satisfy the following relationship: when the temperature is ≤450°C, the holding time is ≥1 hour; when the temperature is greater than 450°C, the holding time is less than 1 hour.

[0039] The multiphase synergistically strengthened copper-titanium alloy obtained by the above preparation method has the following nanostructure:

[0040] The cellular structure has a volume fraction of ≥80%, and is composed of a β-Cu4Ti phase and an α-Cu matrix phase alternately arranged into a nano-laminated structure, wherein the β-Cu4Ti phase is a β-Cu4Ti discontinuous precipitate phase in the form of a sheet or fiber; the thickness of the β-Cu4Ti phase is ≤100 nm; the β-Cu4Ti discontinuous precipitate phase is elongated along the rolling direction after cold rolling deformation, such as Figure 2 shown.

[0041] The β′-Cu4Ti continuous precipitate phase is uniformly distributed in the α-Cu matrix phase and presents a coherent or semi-coherent relationship with the α-Cu matrix phase. The average size of the β′-Cu4Ti continuous precipitate phase is 10±5 nm. Figure 3 shown.

[0042] The copper-titanium alloy has a Vickers hardness of ≥280 HV, a tensile strength of ≥1000 MPa, a conductivity of ≥24% IACS, and a product of strength and conductivity of ≥24000 MPa·% IACS.

[0043] The following are specific embodiments and comparative examples:

[0044] Example 1

[0045] (1) Vacuum melting: Weigh the alloy raw materials according to the mass percentage, with Ti: 3.2% and the balance being Cu, and then place the raw materials together in a crucible and melt the alloy ingot by vacuum induction melting; wherein the alloy raw materials are pure copper, pure titanium, pure cobalt or an intermediate alloy containing alloy elements;

[0046] (2) Homogenization heat treatment: keep the ingot at 950℃ for 24h and then cool it to room temperature with water;

[0047] (3) Hot rolling: The homogenized alloy is hot rolled at 850°C with a deformation of 75%, and then water-cooled to room temperature;

[0048] (4) Solution heat treatment: The hot-rolled alloy was kept at 850 °C for 1 h and then water-cooled to room temperature;

[0049] (5) Discontinuous precipitation aging heat treatment: The alloy after solution heat treatment is kept at 500 °C for 48 h and then water-cooled to room temperature;

[0050] (6) Cold rolling: The alloy after discontinuous precipitation aging is cold rolled with a reduction of 95%;

[0051] (7) Continuous precipitation aging heat treatment: The cold-rolled alloy is heated to 350° C., kept at this temperature for 1 hour, and then water-cooled to room temperature to obtain the copper-titanium alloy.

[0052] Example 2

[0053] (1) Vacuum melting: Weigh the alloy raw materials according to the mass percentage of Ti: 3%, Co: 0.2%, and the balance Cu, then put the raw materials into a crucible and melt the alloy ingot by vacuum induction melting; wherein the alloy raw materials are pure copper, pure titanium, pure cobalt or an intermediate alloy containing alloy elements;

[0054] (2) Homogenization heat treatment: keep the ingot at 850℃ for 24h and then cool it to room temperature with water;

[0055] (3) Hot rolling: The homogenized alloy is hot rolled at 850°C with a deformation of 75%, and then water-cooled to room temperature;

[0056] (4) Solution heat treatment: The hot-rolled alloy was kept at 850 °C for 1 h and then water-cooled to room temperature;

[0057] (5) Discontinuous precipitation aging heat treatment: The alloy after solution heat treatment is kept at 500 °C for 120 h and then water-cooled to room temperature;

[0058] (6) Cold rolling: The alloy after discontinuous precipitation aging is cold rolled with a reduction of 95%;

[0059] (7) Continuous precipitation aging heat treatment: The cold-rolled alloy is heated to 400°C, kept at this temperature for 2 hours, and then water-cooled to room temperature to obtain the copper-titanium alloy.

[0060] Example 3

[0061] (1) Vacuum melting: Weigh the alloy raw materials according to the mass percentage of Ti: 3%, Co: 0.2%, and the balance Cu, then put the raw materials into a crucible and melt the alloy ingot by vacuum induction melting; wherein the alloy raw materials are pure copper, pure titanium, pure cobalt or an intermediate alloy containing alloy elements;

[0062] (2) Homogenization heat treatment: keep the ingot at 850℃ for 24h and then cool it to room temperature with water;

[0063] (3) Hot rolling: The homogenized alloy is hot rolled at 850°C with a deformation of 75%, and then water-cooled to room temperature;

[0064] (4) Solution heat treatment: The hot-rolled alloy was kept at 850 °C for 1 h and then water-cooled to room temperature;

[0065] (5) Discontinuous precipitation aging heat treatment: The alloy after solution heat treatment was kept at 550 °C for 4 h and then water-cooled to room temperature;

[0066] (6) Cold rolling: The alloy after discontinuous precipitation aging is cold rolled with a reduction of 95%;

[0067] (7) Continuous precipitation aging heat treatment: The cold-rolled alloy is heated to 450°C, kept at this temperature for 1 hour, and then water-cooled to room temperature to obtain the copper-titanium alloy.

[0068] Example 4

[0069] (1) Vacuum melting: Weigh the alloy raw materials according to the mass percentage of Ti: 3%, Co: 0.2%, and the balance Cu, then put the raw materials into a crucible and melt the alloy ingot by vacuum induction melting; wherein the alloy raw materials are pure copper, pure titanium, pure cobalt or an intermediate alloy containing alloy elements;

[0070] (2) Homogenization heat treatment: keep the ingot at 850℃ for 24h and then cool it to room temperature with water;

[0071] (3) Hot rolling: The homogenized alloy is hot rolled at 850°C with a deformation of 75%, and then water-cooled to room temperature;

[0072] (4) Solution heat treatment: The hot-rolled alloy was kept at 850 °C for 1 h and then water-cooled to room temperature;

[0073] (5) Discontinuous precipitation aging heat treatment: The alloy after solution heat treatment is kept at 500 °C for 48 h and then water-cooled to room temperature;

[0074] (6) Cold rolling: The alloy after discontinuous precipitation aging is cold rolled with a reduction of 80%;

[0075] (7) Continuous precipitation aging heat treatment: The cold-rolled alloy is heated to 300°C, kept at this temperature for 8 hours, and then water-cooled to room temperature to obtain the copper-titanium alloy.

[0076] Example 5

[0077] (1) Vacuum melting: Weigh the alloy raw materials according to the mass percentage of Ti: 3%, Co: 0.2%, and the balance Cu, then put the raw materials into a crucible and melt the alloy ingot by vacuum induction melting; wherein the alloy raw materials are pure copper, pure titanium, pure cobalt or an intermediate alloy containing alloy elements;

[0078] (2) Homogenization heat treatment: keep the ingot at 950℃ for 4h and then cool it to room temperature with water;

[0079] (3) Hot rolling: The homogenized alloy is hot rolled at 950°C with a deformation of 75%, and then water-cooled to room temperature;

[0080] (4) Solution heat treatment: The hot-rolled alloy was kept at 950 °C for 1 h and then water-cooled to room temperature;

[0081] (5) Discontinuous precipitation aging heat treatment: The alloy after solution heat treatment was kept at 550 °C for 4 h and then water-cooled to room temperature;

[0082] (6) Cold rolling: The alloy after discontinuous precipitation aging is cold rolled with a reduction of 90%;

[0083] (7) Continuous precipitation aging heat treatment: The cold-rolled alloy is heated to 500°C, kept at this temperature for 0.5 h, and then water-cooled to room temperature to obtain the copper-titanium alloy.

[0084] Comparative Example 1

[0085] The alloy raw materials are weighed according to the mass percentage, Ti: 3.2%, and the balance is Cu. The raw materials are then placed in a crucible and melted into an alloy ingot using a vacuum induction melting method.

[0086] The alloy ingot was heated to 950°C in an argon atmosphere and kept at this temperature for 24 hours for homogenization heat treatment, and then water-cooled to room temperature; then heated to 850°C for hot rolling with a hot rolling deformation of 75% to obtain a copper-titanium alloy slab; then the obtained copper-titanium alloy slab was solution treated at 850°C, kept at this temperature for 1 hour, and water-cooled to room temperature to obtain a solid solution alloy billet;

[0087] The solid solution alloy billet is subjected to continuous precipitation aging heat treatment at 500°C for 2 hours, and then water-cooled to room temperature to obtain a peak-aged copper-titanium alloy.

[0088] Comparative Example 2

[0089] The alloy raw materials are weighed according to the mass percentage, Ti: 3%, Co: 0.2%, and the balance is Cu, and then the raw materials are put into a crucible and melted into an alloy ingot by vacuum induction melting;

[0090] The alloy ingot was heated to 850°C in an argon atmosphere and kept at this temperature for 24 hours for homogenization heat treatment, and then water-cooled to room temperature; then heated to 850°C for hot rolling with a hot rolling deformation of 75% to obtain a copper-titanium alloy slab; then the obtained copper-titanium alloy slab was solution treated at 850°C, kept at this temperature for 2 hours, and water-cooled to room temperature to obtain a solid solution alloy billet;

[0091] The solid solution alloy billet is cold rolled and deformed with a cold rolling deformation of 80% to obtain a cold rolled alloy plate; the cold rolled plate is then subjected to a continuous precipitation aging heat treatment at 450°C for 2 hours to obtain a pre-deformed aged copper-titanium alloy.

[0092] Table 1 Performance comparison between examples and comparative examples

[0093]

[0094] As can be seen from Table 1, unlike the traditional solid solution + continuous precipitation aging process and the solid solution + pre-deformation + continuous aging process, the mechanical properties and electrical conductivity of the copper-titanium alloy prepared by the method of the present invention are greatly improved. In particular, under the premise of ensuring that the hardness and tensile strength are basically not reduced, the electrical conductivity of the copper-titanium alloy prepared by the method of the present invention is increased by at least 2 times compared with the traditional copper-titanium alloy, showing excellent comprehensive performance.

[0095] The above specific embodiments are used to illustrate the present invention rather than to limit the present invention. Any modifications and changes made to the present invention within the spirit of the present invention and the protection scope of the claims shall fall within the protection scope of the present invention.

Claims

1. A multiphase synergistically strengthened copper-titanium alloy, characterized in that: The microstructure of copper-titanium alloy has the following nanostructure: The cellular structure is composed of a β-Cu4Ti phase and an α-Cu matrix phase alternately arranged into a nano-laminated structure, wherein the β-Cu4Ti phase is a β-Cu4Ti discontinuous precipitated phase in the form of a sheet or fiber; The β′-Cu4Ti continuous precipitate phase is evenly distributed in the α-Cu matrix phase and presents a coherent or semi-coherent relationship with the α-Cu matrix phase.

2. The multiphase synergistically strengthened copper-titanium alloy according to claim 1, characterized in that: The thickness of the β-Cu4Ti phase is ≤100 nm; the average size of the β′-Cu4Ti continuous precipitated phase is 10±5 nm; and the volume fraction of the cellular structure is ≥80%.

3. The multiphase synergistically strengthened copper-titanium alloy according to claim 1, characterized in that: The copper-titanium alloy has a Vickers hardness of ≥280 HV, a tensile strength of ≥1000 MPa, a conductivity of ≥24% IACS, and a product of strength and conductivity of ≥24000 MPa·% IACS.

4. The multiphase synergistically strengthened copper-titanium alloy according to claim 1, characterized in that: The copper-titanium alloy element content is calculated by mass percentage, with Ti being 1-5%, Co being 0-0.5%, and the remainder being copper and unavoidable impurities.

5. The multiphase synergistically strengthened copper-titanium alloy according to claim 1, characterized in that: The β-Cu4Ti discontinuous precipitation phase is elongated along the rolling direction after cold rolling deformation, forming a cross-scale multi-phase synergistic strengthening structure.

6. A method for preparing a multiphase synergistically strengthened copper-titanium alloy according to any one of claims 1 to 5, characterized in that: The following steps are involved: (1) Vacuum melting: According to the composition of copper-titanium alloy, weigh the alloy raw materials respectively and use vacuum induction melting method to obtain alloy ingots; (2) Homogenization heat treatment: keep the ingot at 850~950℃ for 4~24h, and then cool it to room temperature with water; (3) Hot rolling: The homogenized alloy is hot rolled at 850-950°C with a deformation of 70-80%, and then water-cooled to room temperature; (4) Solution heat treatment: The hot-rolled alloy is kept at 850-950 °C for 1-4 h, and then water-cooled to room temperature; (5) Discontinuous precipitation aging heat treatment: The alloy after solution heat treatment is kept at 450~550℃ for 2~120h, and then water-cooled to room temperature; (6) Cold rolling: The alloy that has undergone discontinuous precipitation aging is cold rolled with a reduction greater than 80%; (7) Continuous precipitation aging heat treatment: the cold-rolled alloy is heated to 300-500°C, kept at this temperature for 0.5-8 hours, and then water-cooled to room temperature to obtain the copper-titanium alloy.

7. The preparation method according to claim 6, characterized in that: In the step (6), dislocation defects are introduced after cold rolling deformation to promote the nucleation of continuous precipitation phase.

8. The preparation method according to claim 6, characterized in that: In the step (7), the continuous precipitation aging temperature and time satisfy the following relationship: when the temperature is ≤450°C, the holding time is ≥1h; when the temperature is >450°C, the holding time is <1h.

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