High-performance plastic forming method for thermoelectric brittle material

Abstract

The application discloses a high-performance plastic forming method of thermoelectric brittle material, which comprises the following steps: loading a thermoelectric brittle material blank into a hollow metal sleeve, filling bentonite in the gap between the thermoelectric brittle material blank and the hollow metal sleeve, heating the whole to a preset temperature and keeping the temperature for a period of time, performing isothermal forming on the whole, taking out the thermoelectric brittle material in the hollow metal sleeve after cooling to a certain temperature, and obtaining the plastic formed thermoelectric brittle material. The beneficial effects of the technical scheme are that: during the heating and compression process, the bentonite exerts a strong high-pressure effect on the periphery of the internal thermoelectric brittle material blank, and in addition, the pre-compression stress of the mold cavity and the outermost metal sleeve on the internal thermoelectric brittle material blank, the thermoelectric brittle material blank is subjected to compression stress in all directions, the compression stress of the thermoelectric brittle material blank in all directions is relatively uniform, and the cracking or even breaking phenomenon of the thermoelectric brittle material during the compression process is prevented.

Description

Technical Field

[0001] This invention relates to the field of thermoelectric brittle material forming technology, and in particular to a high-performance plastic forming method for thermoelectric brittle materials. Background Technology

[0002] Thermoelectric materials, as a type of clean energy material, can directly convert thermal energy into electrical energy using the thermoelectric conversion effect (e.g., Chinese invention patent application number CN202011099264.9). The thermoelectric conversion effect refers to the directional movement of charge carriers in the material under the influence of a temperature gradient, resulting in charge accumulation and reversible thermal effects caused by current excitation. Thermoelectric materials are characterized by their small size, noiselessness, low pollution, lack of need for transmission components, reliable performance, and long lifespan, making them a promising candidate for waste energy recovery and solid-state refrigeration.

[0003] However, most thermoelectric materials are inorganic semiconductors with very low plasticity (less than 10%), making them essentially brittle and unable to undergo plastic deformation. Unlike other materials, the plasticity of thermoelectric materials does not increase with temperature; they remain brittle regardless of temperature. Thermoelectric materials are typically used in applications with complex shapes, and during compression molding, they may break. Traditional thermoelectric material molding processes require thermal deformation, which easily leads to cracking and other defects. Therefore, current processes cannot achieve large-scale compression molding of thermoelectric materials, hindering their further application and expansion. Summary of the Invention

[0004] In view of this, it is necessary to provide a high-performance plastic forming method for thermoelectric brittle materials to solve the technical problem that the materials are prone to cracking during thermal deformation.

[0005] To achieve the above objectives, the present invention provides a high-performance plastic forming method for thermoelectrically brittle materials, comprising the following steps:

[0006] S1. The thermoelectric brittle material blank is loaded into a hollow metal sleeve, and then bentonite is filled in the gap between the thermoelectric brittle material blank and the hollow metal sleeve. Bentonite is also laid at both ends of the thermoelectric brittle material.

[0007] S2. Heat the hollow metal sleeve filled with thermoelectric brittle material and bentonite to a preset temperature and keep it at that temperature for a period of time.

[0008] S3. The hollow metal sleeve filled with thermoelectric brittle material and bentonite after heating and heat preservation is subjected to isothermal forming.

[0009] S4. Cool the hollow metal sleeve filled with thermoelectric brittle material and bentonite after compression molding. After cooling to a certain temperature, remove the thermoelectric brittle material from the hollow metal sleeve to obtain the thermoelectric brittle material after plastic molding.

[0010] In some embodiments, in step S1, the hollow metal sleeve is made of a low thermal expansion alloy.

[0011] In some embodiments, in step S1, the hollow metal sleeve is made of titanium alloy.

[0012] In some embodiments, in step S1, the thickness of the hollow metal sleeve is 10%-50% of the diameter of the thermoelectrically brittle material blank.

[0013] In some embodiments, in step S1, the thickness of the bentonite layer between the hollow metal sleeve and the thermoelectric brittle material blank is 2%-10% of the diameter of the thermoelectric brittle material blank.

[0014] In some embodiments, in step S2, the hollow metal sleeve filled with thermoelectric brittle material and bentonite is heated to 400-700°C and kept at that temperature for 1-60 minutes.

[0015] In some embodiments, in step S3, the hollow metal sleeve filled with thermoelectric brittle material and bentonite after heating and heat preservation is subjected to a temperature change of 0.001 to 10 seconds. -1 Isothermal forming is performed at a strain rate.

[0016] In some embodiments, in step S4, the hollow metal sleeve filled with thermoelectric brittle material and bentonite after compression molding is cooled to room temperature.

[0017] In some embodiments, the specific method for removing the thermoelectrically brittle material inside the hollow metal sleeve in step S4 includes:

[0018] S41. Cut the hollow metal sleeve and then peel it off.

[0019] S42. Continue to peel off the bentonite to obtain the thermoelectrically brittle material after plastic forming.

[0020] In some embodiments, in step S41, a wire cutting machine is used to cut the hollow metal sleeve.

[0021] Compared with the prior art, the beneficial effects of the technical solution proposed in this invention are as follows: Because the internal thermoelectric brittle material blank is encased in bentonite, it can prevent the thermoelectric brittle material blank from reacting with the outer hollow metal sleeve and causing adhesion during compression molding. Since the thermal expansion coefficient of bentonite is greater than that of the outer metal sleeve and the internal thermoelectric material blank, and the strength of the outer hollow metal sleeve is much greater than that of the internal thermoelectric brittle material blank, the bentonite will apply strong high pressure to the periphery of the internal thermoelectric brittle material blank during heating and compression. Combined with the pre-compression stress of the mold cavity and the outermost metal sleeve on the internal thermoelectric brittle material blank, the thermoelectric brittle material blank is subjected to compressive stress in all directions. This compressive stress is relatively uniform, which is beneficial for its forming. The plasticity of the thermoelectric brittle material blank is greatly improved, significantly preventing cracking or even breakage of the thermoelectric brittle material during compression. This process can achieve large deformation compression molding of thermoelectric materials, which is beneficial for the further application and expansion of thermoelectric materials. Attached Figure Description

[0022] Figure 1 This is a schematic flowchart of an embodiment of the high-performance plastic forming method for thermoelectrically brittle materials provided by the present invention;

[0023] Figure 2 yes Figure 1 A schematic diagram of each step in the high-performance plastic forming method for thermoelectrically brittle materials;

[0024] Figure 3 yes Figure 1 A flowchart illustrating the specific method for removing the thermoelectrically brittle material from the hollow metal sleeve in step S4. Detailed Implementation

[0025] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0026] Please refer to Figure 1 and Figure 2 This invention provides a high-performance plastic forming method for thermoelectrically brittle materials, comprising the following steps:

[0027] S1. The thermoelectric brittle material blank is loaded into a hollow metal sleeve, and then bentonite is filled in the gap between the thermoelectric brittle material blank and the hollow metal sleeve. Bentonite is also applied to both ends of the thermoelectric brittle material. The purpose of the bentonite is to prevent the thermoelectric brittle material blank from reacting with the outer hollow metal sleeve during the subsequent isothermal compression process, which would cause adhesion.

[0028] Preferably, the hollow metal sleeve is made of a low thermal expansion alloy. Specifically, the hollow metal sleeve is made of titanium alloy. Low thermal expansion alloys such as titanium alloy have high strength and low thermal expansion rate, which facilitates the application of inward pressure to the thermoelectrically brittle material blank by the difference in expansion rate between titanium alloy and bentonite during the subsequent isothermal compression process.

[0029] Preferably, the thickness of the hollow metal sleeve is 10%-50% of the diameter of the thermoelectric brittle material blank. If the thickness of the hollow metal sleeve is too large, it will increase the cost of use. If the thickness of the hollow metal sleeve is too small, its strength may not be sufficient to meet the requirements of this process.

[0030] Preferably, the thickness of the bentonite layer between the hollow metal sleeve and the thermoelectric brittle material blank is 2%-10% of the diameter of the thermoelectric brittle material blank. The function of the bentonite is to prevent the thermoelectric brittle material blank from reacting with the outer hollow metal sleeve during the subsequent isothermal compression process, which would cause adhesion.

[0031] S2. Heat the hollow metal sleeve filled with thermoelectric brittle material and bentonite to a preset temperature and keep it at that temperature for a period of time.

[0032] Specifically, the hollow metal sleeve filled with thermoelectric brittle material and bentonite is heated to 400-700°C and held at that temperature for 1-60 minutes.

[0033] S3. The hollow metal sleeve filled with thermoelectric brittle material and bentonite after heating and heat preservation is subjected to isothermal forming.

[0034] Preferably, the hollow metal sleeve filled with thermoelectric brittle material and bentonite after heating and heat preservation is subjected to a process of 0.001 to 10 s. -1 The strain rate is used for isothermal forming, and the isothermal forming temperature is equal to the temperature of the heat preservation stage.

[0035] In this invention, the internal thermoelectric brittle material, encased in bentonite, prevents it from reacting with the outer hollow metal sleeve and sticking together during compression molding. Since the thermal expansion coefficient of bentonite is greater than that of the outer metal sleeve and the internal thermoelectric material blank, and the strength of the outer hollow metal sleeve is much greater than that of the internal thermoelectric brittle material blank, the bentonite applies strong high pressure to the periphery of the internal thermoelectric brittle material blank during heating and compression. Combined with the pre-compression stress from the mold cavity and the outermost metal sleeve, the thermoelectric brittle material blank is subjected to compressive stress in all directions. This relatively uniform compressive stress facilitates its forming and reduces the probability of defects such as cracking.

[0036] S4. Cool the hollow metal sleeve filled with thermoelectric brittle material and bentonite after compression molding. After cooling to a certain temperature, remove the thermoelectric brittle material from the hollow metal sleeve to obtain the thermoelectric brittle material after plastic molding.

[0037] Specifically, the hollow metal sleeve filled with thermoelectric brittle material and bentonite after compression molding is cooled to room temperature.

[0038] Specifically, please refer to Figure 3 In step S4, the specific method for removing the thermoelectrically brittle material inside the hollow metal sleeve includes:

[0039] S41. Cut the hollow metal sleeve and then peel it off; specifically, use a wire cutting machine to cut the hollow metal sleeve.

[0040] S42. Continue to peel off the bentonite to obtain the thermoelectrically brittle material after plastic forming.

[0041] The beneficial effects of the technical solution provided by this invention are as follows: Because the internal thermoelectric brittle material blank is encased in bentonite, it prevents the thermoelectric brittle material blank from reacting with the outer hollow metal sleeve and causing adhesion during compression molding. Since the thermal expansion coefficient of bentonite is greater than that of the outer metal sleeve and the internal thermoelectric material blank, and the strength of the outer hollow metal sleeve is much greater than that of the internal thermoelectric brittle material blank, the bentonite applies strong high pressure to the periphery of the internal thermoelectric brittle material blank during heating and compression. Combined with the pre-compression stress of the mold cavity and the outermost metal sleeve on the internal thermoelectric brittle material blank, the thermoelectric brittle material blank is subjected to compressive stress in all directions. This compressive stress is relatively uniform, which is beneficial for its forming. The plasticity of the thermoelectric brittle material blank is greatly improved, significantly preventing cracking or even breakage of the thermoelectric brittle material during compression. This process enables large deformation compression molding of thermoelectric materials, which is beneficial for the further application and expansion of thermoelectric materials.

[0042] The present invention will be further described in detail below with reference to specific embodiments.

[0043] Example 1

[0044] This invention provides a high-performance plastic forming method for thermoelectrically brittle materials, using N-type Bi2Te3 blanks as forming materials, specifically including the following steps:

[0045] Step 1: Pre-treatment of the sealing structure of the thermoelectric material blank: Using a Bi2Te3 blank with a diameter of 9.7mm and a height of 11.9mm, the Bi2Te3 blank is inserted into a TC4 hollow metal sleeve. The inner diameter of the hollow metal sleeve is 10.9mm, the height of the hollow metal sleeve is 12.6mm, the thickness of the hollow metal sleeve is 4mm, and the gap between the hollow metal sleeve and the thermoelectric material blank is 0.6mm. Bentonite is filled into the gap and the upper and lower end faces to form a sealing structure.

[0046] Step 2: Heating the sealing structure: The entire sealing structure containing the Bi2Te3 blank is heated to 500℃ and held for 15 minutes;

[0047] Step 3, Hot Compression of the Billet: The thermoelectric material billet after heat preservation is hot compressed at a rate of 0.01s. -1 The strain rate was used for compression forming, with a deformation of 40%.

[0048] Step 4: Remove the metal sleeve: Take out the sealing structure and cool it, remove the outer hollow metal sleeve, take out the inner Bi2Te3 material, and obtain the formed N-type Bi2Te3 thermoelectric material.

[0049] Example 2

[0050] This invention provides a high-performance plastic forming method for thermoelectrically brittle materials, using N-type Bi2Te3 blanks as forming materials, specifically including the following steps:

[0051] Step 1: Pre-treatment of the sealing structure of the thermoelectric material billet: Using a Bi2Te3 billet with a diameter of 9.7mm and a height of 12.3mm, the Bi2Te3 billet is inserted into a TC4 hollow metal sleeve. The inner diameter of the hollow metal sleeve is 10.9mm, the height of the hollow metal sleeve is 12.8mm, the thickness of the hollow metal sleeve is 4mm, and the gap between the hollow metal sleeve and the Bi2Te3 billet is 0.6mm. Bentonite is filled in the gap and on the top and bottom surfaces to form a sealing structure.

[0052] Step 2: Heating the billet: The entire sealed structure containing the Bi2Te3 billet is heated to 550℃ and held for 15 minutes;

[0053] Step 3, Hot Compression of Billet: The billet after heat preservation is hot compressed at a rate of 0.01s. -1 Strain rate compression forming;

[0054] Step 4: Remove the metal sleeve: Take out the sealing structure and let it cool. Remove the outer metal sleeve and take out the inner Bi2Te3 material to obtain the formed N-type Bi2Te3 thermoelectric material.

[0055] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A high-performance plastic forming method for thermoelectrically brittle materials, characterized in that, Includes the following steps: S1. A thermoelectric brittle material blank is inserted into a hollow metal sleeve, and bentonite is filled into the gap between the thermoelectric brittle material blank and the hollow metal sleeve. Bentonite is also laid at both ends of the thermoelectric brittle material. The thermal expansion coefficient of the bentonite is greater than that of the hollow metal sleeve and the thermoelectric brittle material, and the strength of the hollow metal sleeve is greater than that of the thermoelectric brittle material. S2. Heat the hollow metal sleeve filled with thermoelectric brittle material and bentonite to a preset temperature and keep it at that temperature for a period of time. S3. The hollow metal sleeve filled with thermoelectric brittle material and bentonite after heating and heat preservation is subjected to isothermal forming. S4. Cool the hollow metal sleeve filled with thermoelectric brittle material and bentonite after compression molding. After cooling to a certain temperature, remove the thermoelectric brittle material from the hollow metal sleeve to obtain the thermoelectric brittle material after plastic molding.

2. The high-performance plastic forming method for thermoelectrically brittle materials according to claim 1, characterized in that, In step S1, the hollow metal sleeve is made of a low thermal expansion alloy.

3. The high-performance plastic forming method for thermoelectrically brittle materials according to claim 2, characterized in that, In step S1, the hollow metal sleeve is made of titanium alloy.

4. The high-performance plastic forming method for thermoelectrically brittle materials according to claim 1, characterized in that, In step S1, the thickness of the hollow metal sleeve is 10%-50% of the diameter of the thermoelectrically brittle material blank.

5. The high-performance plastic forming method for thermoelectrically brittle materials according to claim 1, characterized in that, In step S1, the thickness of the bentonite layer between the hollow metal sleeve and the thermoelectric brittle material blank is 2%-10% of the diameter of the thermoelectric brittle material blank.

6. The high-performance plastic forming method for thermoelectrically brittle materials according to claim 1, characterized in that, In step S2, the hollow metal sleeve filled with thermoelectric brittle material and bentonite is heated to 400-700°C and kept at that temperature for 1-60 minutes.

7. The high-performance plastic forming method for thermoelectrically brittle materials according to claim 1, characterized in that, In step S3, the hollow metal sleeve filled with thermoelectric brittle material and bentonite, after being heated and kept at a constant temperature, is subjected to a temperature change of 0.001–10 s. -1 Isothermal forming is performed at a strain rate.

8. The high-performance plastic forming method for thermoelectrically brittle materials according to claim 1, characterized in that, In step S4, the hollow metal sleeve filled with thermoelectric brittle material and bentonite after compression molding is cooled to room temperature.

9. The high-performance plastic forming method for thermoelectrically brittle materials according to claim 1, characterized in that, In step S4, the specific method for removing the thermoelectrically brittle material inside the hollow metal sleeve includes: S41. Cut the hollow metal sleeve and then peel it off. S42. Continue to peel off the bentonite to obtain the thermoelectrically brittle material after plastic forming.

10. The high-performance plastic forming method for thermoelectrically brittle materials according to claim 9, characterized in that, In step S41, a wire cutting machine is used to cut the hollow metal sleeve.

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