Stirring head for friction stir welding and preparation method thereof

Abstract

The invention provides a stirring head for friction stir welding, a preparation method of the stirring head, a gradient tungsten alloy material and a preparation method of the gradient tungsten alloy material. The stirring head for friction stir welding comprises a clamping part, a stirring head shaft shoulder and a stirring head needle tip part, the two tail ends of the stirring head shaft shoulder are connected with the clamping part and the stirring head needle tip part respectively, the clamping part, the stirring head shaft shoulder and the stirring head needle tip part are all prepared from tungsten-rhenium alloy, and the clamping part is connected with the stirring head shaft shoulder through a connecting rod. And the gradient of the tungsten content in the tungsten-rhenium alloy of the stirring head shaft shoulder and the stirring head needle point part is sequentially reduced. The pure tungsten-rhenium stirring head is subjected to component gradient change, parts with different performance requirements are prepared according to alloys with different components, the service life of a stirring head material can be effectively prolonged, and the material cost can be effectively reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of gradient material preparation, and in particular to a stirring head for friction stir welding and a preparation method thereof, as well as a gradient tungsten alloy material and a preparation method thereof. Background Art

[0002] Gradient materials are heterogeneous composite materials whose composition, structure, or properties exhibit continuous or quasi-continuous variations in space. Their core characteristic is that gradient design within the material optimizes the functional combination of different regions, thereby resolving the problem of traditional homogeneous materials being unable to balance multiple properties. Gradient materials are widely used in aerospace, healthcare, biomedical engineering, electronics and semiconductors, friction stir welding, nanotechnology, and smart materials. They are particularly valuable in applications such as rotating anode targets for small-sized tubes and stir tips for friction stir welding.

[0003] Tungsten has a high melting point, high density, good thermal conductivity, and a high elastic modulus, but it also suffers from disadvantages such as low-temperature brittleness, a high ductile-brittle transition temperature (DBTT), and recrystallization embrittlement. Performance can generally be improved through strengthening mechanisms such as solid solution strengthening, grain refinement, and dispersion strengthening. Solid solution strengthening is typically achieved through the addition of metallic rhenium. Compared to pure tungsten, WRe alloys offer improved high-temperature resistance, ductility, low vapor pressure, low electron work function, and a low ductile-brittle transition temperature. Alloy properties vary with the Re content. At room temperature, the yield strength of WRe alloys is lowest at 7% Re, while the fracture toughness is highest. Grain refinement is particularly pronounced in W10Re, which can improve the material's strength and thermal shock resistance. Therefore, designing gradient materials with different compositions, tailored to the application, can improve the material's performance and lifespan.

[0004] Currently, rotating anode targets for small-sized tubes are mostly pure tungsten targets, which is not conducive to target surface machining. Furthermore, the target surface is prone to thermal cracking under the continuous bombardment of high-energy electron beams, leading to target surface damage and tube failure. The high-hardness and high-melting-point stirring tips used in friction stir welding are composed of a uniform tungsten-rhenium alloy, which is costly and hinders the widespread application of this material. To improve material performance and extend component life, gradient materials with different compositions are being prepared to adapt to specific environments. However, there are few reports on the preparation and research of tungsten alloy gradient materials.

[0005] Therefore, the preparation and research of tungsten alloy gradient materials will help to solve the shortcomings and disadvantages of a single material in different environments. Summary of the Invention

[0006] Technical issues To address the problems and shortcomings of the existing technology, the present invention provides a friction stir welding stir head and its preparation method, as well as a gradient tungsten alloy material and its preparation method. By designing tungsten alloy materials with different composition gradients—that is, by adding additives of varying composition or content to tungsten—the shortcomings and deficiencies inherent in the tungsten material itself are overcome or improved. The resulting gradient material has superior performance and service life, effectively reduces material costs, and further enhances the application of gradient materials.

[0007] Technical Solution According to a first aspect of the present invention, a SPS method for preparing a gradient tungsten alloy material is provided, which comprises the following steps: Step 1: Prepare a plurality of tungsten alloy powders with different tungsten contents, and / or a plurality of powder mixtures of metal tungsten powder, other metal powders and any metal oxide powder, mix them evenly and then dry them; Step 2: Pour the various tungsten alloy powders, and / or the various powder mixtures, and / or the metallic tungsten powders obtained in Step 1, with different tungsten contents, into a graphite mold in layers to form multiple layers with a gradient distribution of tungsten content. Pre-press the mold after each layer is laid before laying the next layer. The pre-pressing pressure is 5-15 MPa. Step 3: Place the mold filled with gradient composition powder in the SPS furnace chamber and evacuate to below 5 Pa for sintering. The preparation process is as follows: Axial pressure: 20~50MPa, Heating rate: 20~80℃ / min, Sintering temperature: 1500~1800℃, Insulation time: 20~60min, Cooling rate: The cooling rate from sintering temperature to 1000℃ is 3~15℃ / min, and the cooling from 1000℃ to room temperature is furnace cooling; Step 4: Demolding the gradient material obtained after sintering, cooling and machining to obtain the gradient tungsten alloy material.

[0008] Preferably, the tungsten content in the plurality of tungsten alloy powders or the plurality of powder mixtures in step 1 is 85 wt % to 99 wt % relative to the total weight of the tungsten alloy powders or the powder mixture.

[0009] Preferably, the plurality of tungsten alloy powders or the plurality of powder mixtures in step 1 are composed of rhenium having a content greater than 0 and less than 15 wt %, zirconium oxide having a content of 0 wt % to 3 wt %, and the balance tungsten.

[0010] Preferably, the mixing in step 1 is carried out by planetary ball milling or V-type mixing.

[0011] Preferably, the process conditions described in step 3 are: Axial pressure: 20~40MPa, Heating rate: 40~55℃ / min, Sintering temperature: 1750~1800℃, Insulation time: 20~40min, Cooling rate: The cooling rate from sintering temperature to 1000℃ is 15℃ / min, and the cooling from 1000℃ to room temperature is furnace cooling.

[0012] The above preferred process is obtained based on a large number of experimental tests. Under this condition, the gradient material prepared has better comprehensive performance.

[0013] Preferably, the shear strength of the gradient material interface joint is preferably above 200 MPa.

[0014] According to a second aspect of the present invention, a gradient tungsten alloy product is provided, which is prepared by processing a gradient tungsten alloy material prepared by the SPS method for preparing a gradient tungsten alloy material according to the present invention.

[0015] Preferably, the gradient tungsten alloy product is an anode target or a stirring head for friction stir welding.

[0016] According to a third aspect of the present invention, a stirring head for stir friction welding is provided, which includes: a clamping part, a stirring head shoulder and a stirring head needle tip, the two ends of the stirring head shoulder are respectively connected to the clamping part and the stirring head needle tip, and the clamping part, the stirring head shoulder and the stirring head needle tip are all made of tungsten-rhenium alloy, wherein the tungsten content gradient in the tungsten-rhenium alloy of the clamping part, the stirring head shoulder and the stirring head needle tip decreases successively.

[0017] Preferably, the clamping portion is composed of 1 wt% to 3 wt% rhenium and 97 wt% to 99 wt% tungsten; more preferably, the clamping portion is composed of 3 wt% rhenium and 97 wt% tungsten.

[0018] Preferably, the stirring head shoulder is composed of rhenium with a content greater than 3wt% and less than 9wt% and tungsten with a content greater than 91wt% and less than 97wt%; more preferably, the stirring head shoulder is composed of 5wt% rhenium and 95wt% tungsten.

[0019] Preferably, the tip of the stirring head is composed of 7wt%~13wt% rhenium, 1wt%~3wt% zirconium oxide and the balance tungsten; more preferably, the tip of the stirring head is composed of 10wt% rhenium, 2wt% ZrO2 and 88wt% tungsten.

[0020] Preferably, the friction stir welding stirring head is integrally formed by SPS sintering.

[0021] Preferably, the shear strength of the interface joint of the friction stir welding stirring head is greater than 200 MPa.

[0022] According to a fourth aspect of the present invention, there is provided a method for preparing a stirring head for friction stir welding, comprising the following steps: 1) Powder preparation: prepare a first powder composed of 7wt% to 13wt% rhenium, 1wt% to 3wt% zirconium oxide, and the balance tungsten; a second powder composed of a rhenium content greater than 3wt% and less than 9wt% and a tungsten content greater than 91wt% and less than 97wt%; and a third powder composed of a rhenium content of 1wt% to 3wt% and a tungsten content of 97wt% to 99wt%. When preparing each powder, first add the raw materials and stir them evenly, then place them in a cemented carbide ball milling jar, add cemented carbide balls, and achieve a ball-to-material ratio of 5:1. Evacuate the cemented carbide jar filled with the materials and place it in a planetary ball mill for ball milling and mixing. 2) After ball milling, the powder is vacuum dried; 3) The first powder, second powder, and third powder obtained by drying in step 2) are sequentially layered into a graphite mold, and pre-pressed after each layer is completed before the next layer is laid. The pre-pressing pressure is 5-15 MPa. 4) Place the mold in the SPS furnace chamber and evacuate to below 5Pa for sintering. The preparation process is as follows: Axial pressure: 20~50MPa, Heating rate: 20~80℃ / min, Sintering temperature: 1500~1800℃, Insulation time: 20~60min, Cooling rate: The cooling rate from sintering temperature to 1000℃ is 3~15℃ / min, and the cooling from 1000℃ to room temperature is furnace cooling; 5) The gradient material obtained after sintering is demolded, cooled, and then machined.

[0023] According to a fifth aspect of the present invention, an anode target disk is provided, which has a surface layer and a base layer, wherein the base layer is metal tungsten, and the surface layer is a tungsten-rhenium alloy, and the rhenium content in the tungsten-rhenium alloy is 3wt%~10wt%.

[0024] Preferably, the thickness of the surface layer is 0.7-1.5 mm.

[0025] Beneficial effects 1. Design material composition gradient to solve the problem that some properties of single-component materials cannot better meet actual application requirements and improve material service life.

[0026] 2. By changing the gradient composition of materials, material waste can be effectively reduced, especially playing a very important role in protecting the resources of rare metals such as tungsten and rhenium, and reducing the cost of using tungsten and rhenium materials.

[0027] 3. Spark plasma sintering (SPS) technology can be used to quickly and effectively prepare gradient materials, which can simplify the production process. This method has short sintering time, low energy consumption, and low vacuum requirements for equipment, effectively improving the production and preparation of gradient materials.

[0028] 4. The present invention changes the composition gradient of the pure tungsten target and uses a tungsten-rhenium alloy as the surface for electron beam bombardment, which can effectively solve the surface processing brittleness of the tungsten material and improve the target surface's ability to withstand electron beam bombardment, thereby increasing its service life. The shear strength of the interface between the tungsten-rhenium alloy and tungsten can reach over 200 MPa.

[0029] 5. The present invention makes a gradient change in the composition of the pure tungsten-rhenium stirring head, and prepares components with different performance requirements according to the alloys of different compositions. Since the components formed by sintering the metal tungsten-metal rhenium-ZrO2 mixed powder containing 1wt%~3wt% zirconium oxide, 7wt%~13wt% rhenium and the balance tungsten have higher hardness and wear resistance, it is used as the head area involved in stir friction welding, and W5Re-W3Re is connected to the equipment as the shaft, which effectively improves the life of the stirring head material and reduces the material cost. The room temperature shear strength of the two joints can reach more than 200MPa, and the hardness of W10Re2ZrO2 can reach 450HV 0.5 above. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Schematic diagram showing an anode target prepared according to Example 1 of the present invention.

[0031] Figure 2 Schematic diagram showing a stirring head for friction stir welding prepared according to Example 3 of the present invention. DETAILED DESCRIPTION

[0032] The present invention will be described in detail below with reference to the embodiments and drawings. The following embodiments are implemented based on the technical solutions of the present invention, and provide detailed implementation methods and specific operating procedures. However, the protection scope of the present invention is not limited to the following embodiments.

[0033] The spark plasma sintering furnace used in the following examples was a LABOX-6020 spark plasma sintering system manufactured by Sinter Land Inc., Japan. The current type was a DC pulse current with a pulse sequence of 40:7. The shear strength test was performed using an in-situ tensile and compressive testing system with a shear rate of 0.5 mm / min. -1.

[0034] The W powder used in the following examples, with a D50 of less than 3 μm, was purchased from Xi'an Feilian New Materials Co., Ltd. The rhenium powder used, D50 < 3 μm, was purchased from Xi'an Feilian New Materials Co., Ltd. The ZrO2 powder used, D50 < 4 μm, was purchased from Zhuzhou Runfeng New Materials; Shear strength measurement equipment: in-situ tension and compression testing system.

[0035] Implementation Column 1 Preparation of anode target Step 1: Pour tungsten powder into a cemented carbide pot. Then, add 100g of rhenium powder to 900g of tungsten powder and carbide grinding balls, achieving a ball-to-powder ratio of 5:1. Evacuate the carbide pot and place it in a planetary ball mill for milling. Once completed, remove the pot and place it in a vacuum drying oven, evacuate the air, and heat to 100°C to dry the powder. Similarly, dry the tungsten powder in the drying oven.

[0036] Step 2: Pour the dried W10Re powder into a graphite mold, and then use a hydraulic press to pre-press the powder to 10 MPa. Then add tungsten powder and continue to pre-press it to 10 MPa. The pressing head has a truncated cone-shaped mold cavity.

[0037] Step 3: Place the graphite mold filled with W10Re-W double-layer powder into the SPS furnace chamber and evacuate to below 5 Pa. The preparation process is as follows: Axial pressure: 30MPa, Heating rate: 50℃ / min, Target temperature: 1700°C, Insulation time: 30min, Cooling rate: The rate of cooling from the target temperature to 1000°C is 10°C / min, and cooling from 1000°C to room temperature is furnace cooling, and then machining is performed.

[0038] The thickness of the tungsten-rhenium layer is 1.2±0.5 mm.

[0039] like Figure 1 As shown in the figure, the anode target disk obtained after machining has two parts. The upper thin layer is the W10Re alloy target surface, which is bombarded by the electron beam and produces X-rays. The thickness is 1.2±0.5mm. The lower thick layer is the W substrate, with a thickness range of 16±0.5mm.

[0040] The interface joint shear strength of the W10Re-W gradient material prepared in this embodiment is 202 MPa at room temperature, and the hardness of the W10Re alloy is 350 HV. 0.5 , the hardness of W is 315HV0.5 .

[0041] Implementation 2 Preparation of anode target Step 1: Pour tungsten powder into a cemented carbide pot, then add 100g of rhenium powder to 900g of tungsten powder and carbide grinding balls, with a ball-to-powder ratio of 5:1. Evacuate the carbide pot and place it in a planetary ball mill for milling. Once completed, remove the pot and place it in a vacuum drying oven, evacuate the air, heat to 100°C, and dry the powder. Similarly, dry the corresponding tungsten powder in the drying oven.

[0042] Step 2: Pour the dried W10Re powder into a graphite mold, and then use a hydraulic press to pre-press the powder to 10 MPa. Then add tungsten powder and continue to pre-press it to 10 MPa.

[0043] Step 3: Place the graphite mold filled with W10Re-W double-layer powder into the SPS furnace chamber and evacuate to below 5 Pa. The preparation process is as follows: Axial pressure: 30MPa, Heating rate: 50℃ / min, Target temperature: 1800°C, Insulation time: 30min, Cooling rate: The rate from the target temperature to 1000℃ is 10℃ / min, and the rate from 1000℃ to room temperature is furnace cooling.

[0044] The thickness of the tungsten-rhenium layer is 1.2±0.5 mm.

[0045] The room temperature shear strength of the interface joint of the W10Re-W gradient material prepared in this embodiment is 235 MPa, and the hardness of the W10Re alloy is 365 HV. 0.5 , the hardness of W is 319HV 0.5 .

[0046] Implementation 3 Preparation of stirring head for friction stir welding Step 1: Pour tungsten powder into a cemented carbide jar, then add 100g of rhenium powder to 880g of tungsten powder, then add 20g of ZrO2 powder, and place cemented carbide grinding balls into the jar, with a ball-to-material ratio of 5:1. The jar is then evacuated and placed in a planetary ball mill for milling. After milling, the mixture is removed from the jar and placed in a vacuum drying oven, evacuated, heated to 100°C, and dried to obtain W10Re2ZrO2 powder. W3Re powder with a rhenium content of 3wt% and W5Re powder with a rhenium content of 5wt% are prepared in the same manner.

[0047] Step 2: Pour the dried W10Re2ZrO2 powder into the graphite mold first, and then use a hydraulic press to pre-press the powder to 10MPa, then add W5Re powder and continue to pre-press it to 10MPa, and finally add W3Re powder and pre-press it to 10MPa.

[0048] Step 3: Place the graphite mold containing the three-layer powder of W10Re2ZrO2-W5Re-W3Re into the SPS furnace chamber and evacuate to below 5Pa. The preparation process is as follows: Axial pressure: 30MPa, Heating rate: 40℃ / min, Target temperature: 1650℃, Insulation time: 30min, Cooling rate: The rate of cooling from the target temperature to 1000°C is 10°C / min, and cooling from 1000°C to room temperature is furnace cooling, and then mechanical processing is performed to obtain a stirring head for stir friction welding.

[0049] After machining, the stirring head for friction stir welding is obtained. Figure 2 As shown. The upper portion of the friction stir welding stirring head is the clamping portion, which is primarily connected to the equipment end and does not directly participate in the friction stir of the weld material. Wear resistance and strength requirements are relatively low, so a tungsten-rhenium alloy with a low rhenium content (W3Re alloy) is used. The middle portion of the friction stir welding stirring head is the stirring head shoulder, which serves as the transition zone for the stirring head material. It participates in the surface friction of the weld material and continuously stirs and pressurizes the softened metal. It is required to have certain strength, toughness, and wear resistance, and is composed of W5Re alloy. The lower portion of the friction stir welding stirring head is the stirring head needle tip, which directly participates in the friction stir within the weld material. It is required to have high strength, high toughness, and good wear resistance, and is composed of W10Re2ZrO2 composite material.

[0050] The room temperature shear strength of the W10Re2ZrO2-W5Re and W5Re-W3Re interface joints of the W10Re2ZrO2-W5Re-W3Re gradient material prepared in this embodiment is 205MPa and 212MPa respectively, and the hardness of the W10Re2ZrO2 alloy is 496HV. 0.5 , W5Re alloy hardness is 332HV 0.5 , the hardness of W3Re is 323HV 0.5 .

[0051] Implementation 4 Preparation of stirring head for friction stir welding Step 1: Pour tungsten powder into a cemented carbide jar, then add 100g of rhenium powder to 880g of tungsten powder. Then, add 20g of ZrO2 powder and place cemented carbide grinding balls into the jar, achieving a ball-to-powder ratio of 5:1. The jar is then evacuated and placed in a planetary ball mill for milling. After milling, the mixture is removed from the jar and placed in a vacuum drying oven, where it is evacuated and heated to 100°C for powder drying. W3Re powder with a rhenium content of 3wt% and W5Re powder with a rhenium content of 5wt% are prepared in the same manner.

[0052] Step 2: Pour the dried W10Re2ZrO2 powder into the graphite mold first, and then use a hydraulic press to pre-press the powder to 10MPa, then add W5Re powder and continue to pre-press it to 10MPa, and finally add W3Re powder and pre-press it to 10MPa.

[0053] Step 3: Place the graphite mold containing the three-layer powder of W10Re2ZrO2-W5Re-W3Re into the SPS furnace chamber and evacuate to below 5Pa. The preparation process is as follows: Axial pressure: 30MPa, Heating rate: 40℃ / min, Target temperature: 1800°C, Insulation time: 30min, Cooling rate: The rate of cooling from the target temperature to 1000°C is 10°C / min, and cooling from 1000°C to room temperature is furnace cooling, and then mechanical processing is performed to obtain a stirring head for stir friction welding.

[0054] The room temperature shear strength of the W10Re2ZrO2-W5Re and W5Re-W3Re interface joints of the W10Re2ZrO2-W5Re-W3Re gradient material prepared in this embodiment is 228MPa and 223MPa respectively, and the hardness of the W10Re2ZrO2 alloy is 512HV. 0.5 , W5Re alloy hardness is 338HV 0.5 , the hardness of W3Re is 326HV 0.5 .

Claims

1. A stirring head for friction stir welding, comprising: The clamping part, the stirring head shoulder and the stirring head needle tip, and the two ends of the stirring head shoulder are respectively connected to the clamping part and the stirring head needle tip, and the clamping part, the stirring head shoulder and the stirring head needle tip are all made of tungsten-rhenium alloy, wherein the tungsten content gradient in the tungsten-rhenium alloy of the clamping part, the stirring head shoulder and the stirring head needle tip decreases successively.

2. The stirring head for friction stir welding according to claim 1, wherein: The clamping portion is composed of 1 wt% to 3 wt% of rhenium and 97 wt% to 99 wt% of tungsten; preferably, the clamping portion is composed of 3 wt% of rhenium and 97 wt% of tungsten.

3. The stirring head for friction stir welding according to claim 1, wherein: The stirring head shoulder is composed of rhenium with a content greater than 3wt% and less than 9wt% and tungsten with a content greater than 91wt% and less than 97wt%; Preferably, the stirring head shoulder is composed of 5wt% rhenium and 95wt% tungsten.

4. The stirring head for friction stir welding according to claim 1, wherein: The tip of the stirring head is composed of 7wt% to 13wt% rhenium, 1wt% to 3wt% zirconium oxide and the balance tungsten; Preferably, the tip of the stirring head is composed of 10wt% rhenium, 2wt% ZrO2 and 88wt% tungsten.

5. The stirring head for friction stir welding according to claim 1, wherein: The friction stir welding stirring head is integrally formed by SPS sintering; and / or The shear strength of the interface joint of the stirring head for friction stir welding is above 200 MPa.

6. A method for preparing a stirring head for friction stir welding, comprising the following steps: 1) Powder preparation: prepare a first powder composed of 7wt% to 13wt% rhenium, 1wt% to 3wt% zirconium oxide, and the balance tungsten; a second powder composed of a rhenium content greater than 3wt% and less than 9wt% and a tungsten content greater than 91wt% and less than 97wt%; and a third powder composed of a rhenium content of 1wt% to 3wt% and a tungsten content of 97wt% to 99wt%. When preparing each powder, first add the raw materials and stir them evenly, then place them in a cemented carbide ball milling jar, add cemented carbide balls, and achieve a ball-to-material ratio of 5:

1. Evacuate the cemented carbide jar filled with the materials and place it in a planetary ball mill for ball milling and mixing. 2) After ball milling, the powder is vacuum dried; 3) The first powder, second powder, and third powder obtained by drying in step 2) are sequentially layered into a graphite mold, and pre-pressed after each layer is completed before the next layer is laid. The pre-pressing pressure is 5-15 MPa. 4) Place the mold in the SPS furnace chamber and evacuate to below 5Pa for sintering. The preparation process is as follows: Axial pressure: 20~50MPa, Heating rate: 20~80℃ / min, Sintering temperature: 1500~1800℃, Insulation time: 20~60min, Cooling rate: The cooling rate from sintering temperature to 1000℃ is 3~15℃ / min, and the cooling from 1000℃ to room temperature is furnace cooling; 5) The gradient material obtained after sintering is demolded, cooled, and then machined.

7. The method for preparing a stirring head for friction stir welding according to claim 6, wherein: The first powder consists of 7wt% to 13wt% of rhenium powder, 1wt% to 3wt% of zirconium oxide powder and the balance of tungsten powder; and / or The second powder consists of 5 wt % rhenium powder and 95 wt % tungsten powder; and / or The third powder consists of 3 wt % rhenium powder and 97 wt % tungsten powder; and / or The first powder, the second powder and the third powder obtained by drying in step 2) are sequentially layered and laid in a graphite mold, and pre-pressed after each layer is laid before laying the next layer, with a pre-pressing pressure of 5-15 MPa; and / or The process conditions of step 4 are: Axial pressure: 20~40MPa, Heating rate: 40~55℃ / min, Sintering temperature: 1750~1800℃, Insulation time: 20~40min, Cooling rate: The cooling rate from sintering temperature to 1000℃ is 15℃ / min, and the cooling from 1000℃ to room temperature is furnace cooling.

8. A SPS method for preparing a gradient tungsten alloy material, comprising the following steps: Step 1: preparing a plurality of tungsten alloy powders with different tungsten contents, and / or a plurality of powder mixtures of metal tungsten powder, other metal powders and optional metal oxide powders, mixing them uniformly and then drying them; Step 2: Pour the various tungsten alloy powders, and / or the various powder mixtures, and / or the metallic tungsten powders obtained in Step 1, with different tungsten contents, into a graphite mold in layers to form multiple layers with a gradient distribution of tungsten content. Pre-press the mold after each layer is laid before laying the next layer. The pre-pressing pressure is 5-15 MPa. Step 3: Place the mold filled with gradient composition powder in the SPS furnace chamber and evacuate to below 5 Pa for sintering. The preparation process is as follows: Axial pressure: 20~50MPa, Heating rate: 20~80℃ / min, Sintering temperature: 1500~1800℃, Insulation time: 20~60min, Cooling rate: The cooling rate from sintering temperature to 1000℃ is 3~15℃ / min, and the cooling from 1000℃ to room temperature is furnace cooling; Step 4: Demolding the gradient material obtained after sintering, cooling and machining to obtain the gradient tungsten alloy material.

9. the SPS method for preparing gradient tungsten alloy material according to claim 8, wherein, The tungsten content of the plurality of tungsten alloy powders or the plurality of powder mixtures in step 1 is 85 wt % to 99 wt % relative to the total weight of the tungsten alloy powders or the powder mixture; and / or The plurality of tungsten alloy powders or the plurality of powder mixtures in step 1 are composed of rhenium having a content greater than 0 and less than 15 wt %, zirconium oxide having a content of 0 wt % to 3 wt %, and the balance being tungsten; and / or The mixing in step 1 is carried out by planetary ball milling or V-type mixing; and / or The process conditions of step 3 are: Axial pressure: 20~40MPa, Heating rate: 40~55℃ / min, Sintering temperature: 1750~1800℃, Insulation time: 20~40min, Cooling rate: The cooling rate from sintering temperature to 1000℃ is 15℃ / min, and the cooling from 1000℃ to room temperature is furnace cooling.

10. The SPS method for preparing a gradient tungsten alloy material according to claim 8, wherein The shear strength of the gradient material interface joint is preferably above 200 MPa.

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