Preparation method for high thermal-conductivity titanium alloy material

Abstract

The present invention relates to a preparation method for a high thermal-conductivity titanium alloy material, comprising the following steps: S1, preparation of a feeding material: mixing mixed powder with a binder to prepare the feeding material, wherein the mixed powder comprises mixed titanium alloy spherical powder and nickel-coated multi-walled carbon nanotubes; S2, placing the feeding material into an injection molding machine, and performing injection to form a green part; S3, debinding the green part to form a debound part; and S4, sintering the debound part to obtain a sintered part. In the present invention, on the basis of powder injection molding, the nickel-coated multi-walled carbon nanotubes are used, so that the thermal conductivity of the titanium alloy material is effectively improved; moreover, net shaping technology can be achieved, and subsequent machining procedures are reduced.

Description

A method for preparing high thermal conductivity titanium alloy material Technical Field

[0001] The present invention relates to the field of titanium alloy material preparation, and in particular to a method for preparing a high thermal conductivity titanium alloy material. Background Art

[0002] Titanium and titanium alloy materials have the advantages of low density, high specific strength, small thermal expansion coefficient, good corrosion resistance, high compatibility and easy welding. They are widely used in aerospace, chemical, medical and other fields.

[0003] However, titanium alloys continue to face a series of challenges in their use across various fields due to their poor thermal conductivity. First, titanium alloys' low thermal conductivity means they struggle to dissipate heat, creating difficulties in applications requiring high-temperature operation. For example, in aircraft engines, titanium alloy components are subject to the impact of high-temperature gases. Failure to dissipate heat in a timely manner can lead to thermal fatigue, oxidation, cracking, and other damage to the material, impacting engine performance and lifespan. Furthermore, due to its poor thermal conductivity, titanium alloys are susceptible to overheating during hot working, not only due to improper heating that can cause overheating of the forging or raw material, but also due to the thermal effects of deformation during forging, which can cause microstructural changes and produce an overheated Widmanstätten structure. Finally, titanium alloys have a low thermal conductivity, only 1 / 4 that of steel, 1 / 13 that of aluminum, and 1 / 25 that of copper. Heat cannot be dissipated quickly during machining, resulting in localized high temperatures at the cutting edge (the tool tip temperature during machining is more than double that of steel). This can easily lead to high temperatures in the cutting zone, causing significant deformation and rebound in the part after machining. This increases cutting tool torque, accelerates edge wear, and reduces tool durability.

[0004] Summary of the Invention

[0005] The present invention aims to provide a method for preparing a high-thermal-conductivity titanium alloy. This method utilizes nickel-coated multi-walled carbon nanotubes (MWCNTs) through powder injection molding to effectively improve the thermal conductivity of the titanium alloy. This method also achieves a clean-cut process, reducing subsequent processing steps.

[0006] The technical solution for achieving the purpose of the present invention is: the present invention comprises the following steps:

[0007] S1. Feed preparation: Mixing a mixed powder with a feed to form a feed; wherein the mixed powder comprises a mixed titanium alloy spherical powder and nickel-coated multi-walled carbon nanotubes; the titanium alloy spherical powder has a particle size of 1 to 20 μm; the nickel-coated multi-walled carbon nanotubes have a diameter of 20 to 30 nm, an inner diameter of 5 to 10 nm, a length of 10 to 30 μm, and a nickel content greater than 60 wt %; and the amount of nickel-coated multi-walled carbon nanotubes added to the mixed powder is ≤ 1 wt %;

[0008] S2, placing the feed material in an injection molding machine and injecting it to form a green body;

[0009] S3, degreasing the green body to form a degreased body;

[0010] S4. Sintering the degreased blank to obtain a sintered blank.

[0011] Because ordinary carbon nanotubes have a stable structure, a smooth surface, and few dangling bonds, their wettability with metal matrix powders is poor. Therefore, they require a surface modification process involving electroless plating to improve their dispersion and form a good interface between the carbon nanotubes and the metal matrix powder. However, nickel-coated multi-walled carbon nanotubes can achieve a good interface with the metal matrix powder.

[0012] Titanium alloys, due to their high reactivity, readily react with carbon and oxygen to form carbides and oxides. Carbon nanotubes are primarily composed of carbon. To prevent titanium alloy powder from reacting with the carbon nanotube surface during sintering and damaging the carbon nanotube structure, the carbon nanotube surface is nickel-plated. A nickel coating content exceeding 60% minimizes reaction between the titanium alloy and the carbon nanotubes during the powder injection molding process.

[0013] Spherical titanium alloy powder was chosen because its regular shape reduces the gaps between the powder particles, making it easier to form sintering necks between the powder particles, which is beneficial for sintering densification. Furthermore, mixing spherical titanium alloy powder with nickel-coated multi-walled carbon nanotubes allows the nickel-coated multi-walled carbon nanotubes to better coat the powder particle surfaces.

[0014] Furthermore, the preparation of the feed in the above step S1 includes the following steps:

[0015] A. adding nickel-coated multi-walled carbon nanotubes into an anhydrous ethanol solution containing a dispersant for dispersion;

[0016] B. After the nickel-coated multi-walled carbon nanotubes are completely dispersed, the mixture is placed in a heatable vacuum distillation apparatus for drying to obtain dispersed nickel-coated multi-walled carbon nanotubes;

[0017] C. Fully mixing the nickel-coated multi-walled carbon nanotubes and the mixed titanium alloy spherical powder according to the ratio described in step S1 of claim 1;

[0018] D. Add a binder and mix to prepare feed.

[0019] Due to the strong van der Waals forces between carbon nanotubes, these carbon nanomaterials are attracted to each other and easily form clusters. During the molding process, the carbon nanomaterials that aggregate into clusters cannot form a strong bond with the matrix. This will cause problems such as uneven distribution of carbon nanoreinforcements in the matrix, poor interfacial bonding, and the presence of voids and holes, seriously affecting the various properties of the material. Carbon nanotubes have few surface defects and lack active groups, and their solubility in various solvents is very low. Carbon nanotubes are composed of graphite with a lamellar structure, and the sp2 hybridization of carbon atoms forms highly delocalized electrons. By adding a suitable surfactant, non-covalent bonds are formed to obtain non-covalently functionalized carbon nanotubes, while the solubility is increased and the carbon nanotubes are dispersed in the medium.

[0020] Furthermore, the ratio of the mixed powder to the binder in the above feed is 0.5≤V1 / V2≤1.9, wherein V1 is the volume of the mixed powder and V2 is the volume of the binder.

[0021] The volume ratio of the powder mix to the binder is related to the actual tap density of the selected powder mix. Choosing a reasonable volume ratio based on the actual tap density of the powder helps the binder completely coat the powder particles, avoiding excessive powder particles that could lead to poor feed flowability, and excessive binder content that could impair the conformability of the injection product.

[0022] As an optimized design, the volume proportion of the mixed powder is 58% to 63%, and the rest is a binder; the components of the binder include 60% to 70% polyoxymethylene, 12% to 15% polyethylene, 15% to 20% polypropylene and 3% to 5% stearic acid in terms of mass percentage; the loading range of the feed is 53%-73%.

[0023] As an optimized design, the volume ratio of the above-mentioned adhesive is 35% to 45%, and the components of the adhesive are: 75% to 80% polyoxymethylene, 5% to 10% polyethylene, 5% to 10% polypropylene, 3% to 5% lubricant and 1% to 3% antioxidant.

[0024] Furthermore, in the above step S2, the mold temperature during injection is 80-120°C, the feed heating temperature is 160-220°C, the injection pressure is 80-120 MPa, and the holding time is 1-2.5 s.

[0025] Furthermore, in the above step S4, the sintering temperature T satisfies the following condition: 0.6TL≤T≤0.95TL, where TL is the theoretical melting point temperature of the mixed powder.

[0026] The present invention has positive effects: (1) The present invention aims to improve the poor thermal conductivity of titanium alloy by adding a certain amount of highly thermally conductive nickel-coated multi-walled carbon nanotubes to titanium alloy spherical powder. Nickel-coated multi-walled carbon nanotubes, as a reinforcement of metal-based composite materials, can not only improve the thermal conductivity of titanium alloy materials, but also improve the mechanical properties of titanium alloy materials to a certain extent.

[0027] (2) The method of the present invention is simple and feasible and can be implemented on conventional MIM equipment without the need for additional equipment and processes. The product of the present invention has excellent electrical conductivity, thermal conductivity, and mechanical strength and can be widely used in aerospace, automotive, medical, electronics and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below based on specific embodiments and in conjunction with the accompanying drawings, wherein

[0029] FIG1 is a comparison photo of nickel-coated multi-walled carbon nanotubes before and after dispersion according to the present invention. DETAILED DESCRIPTION

[0030] (Comparative Example)

[0031] The present invention comprises the following steps:

[0032] S1. Feed preparation: preparing titanium alloy powder with a particle size range of 1 to 20 μm (D50: 10 to 13 μm) and mixing it with a binder; kneading the titanium alloy powder and the binder to form a feed; wherein the volume ratio of the titanium alloy mixed powder to the binder is 1.7; the titanium alloy powder accounts for 63% by volume of the feed, and the remainder is the binder; the components of the binder include, by mass percentage, 60% to 70% of polyoxymethylene, 12% to 15% of polyethylene, 15% to 20% of polypropylene, and 3% to 5% of stearic acid;

[0033] S2. Place the feed material in an injection molding machine and inject it into an injection blank through a mold; the injection parameters are: mold temperature of 80-120°C, feed material heating temperature of 160-220°C, injection pressure of 80-120 MPa; holding time of 1-2.5 s;

[0034] S3, degreasing the injection blank to obtain a degreased blank; the specific technical parameters of the degreasing are: degreasing is carried out by catalytic degreasing using oxalic acid as a medium, the degreasing time is degreasing time t≥(60+60*h)min, h is the maximum thickness of the injection blank, unit is mm;

[0035] S4. The degreased blank is subjected to high vacuum sintering to obtain a sintered blank. The specific technical parameters of the sintering are: a metal cavity sintering furnace is used for high vacuum sintering, and the pressure in the furnace is ≤1.0×10-3 Pa, sintering temperature T satisfies 0.65TL≤T≤0.85TL.

[0036] The density of the sintered part is 4.41g / cm 3 The yield strength reaches 1032MPa, the elongation is about 13%, and the thermal conductivity is about 7W / mK.

[0037] (Example 1)

[0038] The present invention comprises the following steps:

[0039] S1. Feed preparation: 0.5 wt% nickel-coated multi-walled carbon nanotubes were added to an anhydrous ethanol solution containing a dispersant for dispersion and drying. This is a treatment of the agglomerated nickel-coated multi-walled carbon nanotubes. The specific effect can be seen in FIG1 .

[0040] The mixed powder is then mixed with titanium alloy spherical powder having a particle size range of 1 to 20 μm (D50: 10 to 13 μm) to prepare a mixed powder; the mixed powder is kneaded with a binder to prepare a feed; wherein the ratio of the mixed powder to the binder is 1.7; the titanium alloy mixed powder accounts for 63% by volume of the feed, and the remainder is the binder; the components of the polymer binder include, by mass percentage, 60% to 70% of polyoxymethylene, 12% to 15% of polyethylene, 15% to 20% of polypropylene, and 3% to 5% of stearic acid;

[0041] S2. Place the feed material in an injection molding machine and inject it into an injection blank through a mold; the injection parameters are: mold temperature of 80-120°C, feed material heating temperature of 160-220°C, injection pressure of 80-120 MPa; holding time of 1-2.5 s;

[0042] S3, degreasing the injection blank to obtain a degreased blank; the specific technical parameters of the degreasing are: degreasing is carried out by catalytic degreasing using oxalic acid as a medium, the degreasing time is degreasing time t≥(60+60*h)min, h is the maximum thickness of the injection blank, unit is mm;

[0043] S4. The degreased blank is subjected to high vacuum sintering to obtain a sintered blank. The specific technical parameters of the sintering are: a metal cavity sintering furnace is used for high vacuum sintering, and the pressure in the furnace is ≤1.0×10 -3 Pa, sintering temperature T satisfies 0.65TL≤T≤0.85TL.

[0044] The density of the sintered part is 4.41g / cm 3 The yield strength reaches 1015MPa, the elongation is about 10%, and the thermal conductivity is about 20W / mK.

[0045] (Example 2)

[0046] The present invention comprises the following steps:

[0047] S1. Feed preparation: adding 1 wt% nickel-coated multi-walled carbon nanotubes to an anhydrous ethanol solution containing a dispersant, dispersing the mixture, and drying the mixture;

[0048] The titanium alloy spherical powder having a particle size range of 1 to 20 μm (D50: 10 to 13 μm) is then mixed to prepare a mixed powder; the mixed powder is kneaded with a binder to form a feed; wherein the ratio of the mixed powder to the binder is 1.7; the titanium alloy mixed powder accounts for 63% by volume of the feed, and the remainder is the binder; the components of the binder include, by mass percentage, 60% to 70% of polyoxymethylene, 12% to 15% of polyethylene, 15% to 20% of polypropylene, and 3% to 5% of stearic acid;

[0049] S3. Place the feed material in an injection molding machine and inject it into an injection blank through a mold; the injection parameters are: mold temperature of 80-120°C, feed material heating temperature of 160-220°C, injection pressure of 80-120 MPa; holding time of 1-2.5 s;

[0050] S4. Degreasing the injection blank to obtain a degreased blank; the specific technical parameters of the degreasing are: degreasing is performed by catalytic degreasing using an oxalic acid medium, and the degreasing time is t≥(60+60*h)min, where h is the maximum thickness of the injection blank, in mm;

[0051] S5. The degreased blank is subjected to high vacuum sintering to obtain a sintered blank. The specific technical parameters of the sintering are: a metal cavity sintering furnace is used for high vacuum sintering, and the pressure in the furnace is ≤1.0×10 -3 Pa, sintering temperature T satisfies 0.65TL≤T≤0.85TL.

[0052] The density of the sintered part is 4.41g / cm 3 The yield strength reaches 979MPa, the elongation is about 7%, and the thermal conductivity is about 35W / mK.

[0053] By comparing the technical parameters of the sintered parts in the comparative example, example 1 and example 2, it can be seen that the thermal conductivity of the titanium alloy material can be greatly increased by coating the nickel-coated multi-walled carbon nanotubes.

[0054] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above are only 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 in the scope of protection of the present invention.

Claims

1. A method for preparing a high thermal conductivity titanium alloy material, characterized in that The following steps are involved: S1. Feed preparation: Mixing a mixed powder with a feed to form a feed; wherein the mixed powder comprises a mixed titanium alloy spherical powder and nickel-coated multi-walled carbon nanotubes; the titanium alloy spherical powder has a particle size of 1 to 20 μm; the nickel-coated multi-walled carbon nanotubes have a diameter of 20 to 30 nm, an inner diameter of 5 to 10 nm, a length of 10 to 30 μm, and a nickel content of greater than 60 wt%; the amount of nickel-coated multi-walled carbon nanotubes added to the mixed powder is ≤ 1 wt%; S2, placing the feed material in an injection molding machine and injecting it to form a green body; S3, degreasing the green body to form a degreased body; S4, sintering the degreased blank to obtain a sintered blank.

2. The method for preparing a high thermal conductivity titanium alloy material according to claim 1, characterized in that: The preparation of feed in step S1 comprises the following steps: A. adding nickel-coated multi-walled carbon nanotubes into an anhydrous ethanol solution containing a dispersant for dispersion; B. After the nickel-coated multi-walled carbon nanotubes are completely dispersed, they are placed in a heatable vacuum distillation device for drying to obtain dispersed nickel-coated multi-walled carbon nanotubes; C. Fully mixing the nickel-coated multi-walled carbon nanotubes and the mixed titanium alloy spherical powder according to the ratio described in step S1 of claim 1; D. Add a binder and mix to prepare feed.

3. The method for preparing a high thermal conductivity titanium alloy material according to claim 1 or 2, characterized in that: The ratio of the mixed powder to the binder in the feed is 0.5≤V1 / V2≤1.9, wherein V1 is the volume of the mixed powder and V2 is the volume of the binder.

4. The method for preparing a high thermal conductivity titanium alloy material according to claim 3, characterized in that: The volume proportion of the mixed powder is 58% to 63%, and the rest is a binder; the components of the binder include 60% to 70% polyoxymethylene, 12% to 15% polyethylene, 15% to 20% polypropylene and 3% to 5% stearic acid in terms of mass percentage; the loading range of the feed is 53%-73%.

5. The method for preparing a high thermal conductivity titanium alloy material according to claim 3, characterized in that: The volume ratio of the adhesive is 35% to 45%, and the ingredients of the adhesive are: 75% to 80% of polyoxymethylene, 5% to 10% of polyethylene, 5% to 10% of polypropylene, 3% to 5% of lubricant and 1% to 3% of antioxidant.

6. The method for preparing a high thermal conductivity titanium alloy material according to claim 1, characterized in that: In the step S2, during injection, the mold temperature is 80-120° C., the feed heating temperature is 160-220° C., the injection pressure is 80-120 MPa, and the holding time is 1-2.5 s.

7. The method for preparing a high thermal conductivity titanium alloy material according to claim 1, characterized in that: In the step S4, the sintering temperature T satisfies the following condition: 0.6TL≤T≤0.95TL, where TL is the theoretical melting point temperature of the mixed powder.

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