A method for preparing a high thermal conductivity ultrathin diamond / aluminum composite material

Abstract

This invention discloses a method for preparing a high thermal conductivity ultrathin diamond / aluminum composite material. The method involves laser cutting to create uniformly arranged through-holes on a synthetic sheet diamond; preparing a 100-200 nm thick titanium protective layer on the surface of the synthetic sheet diamond using vacuum magnetron sputtering; heat-treating the material in a vacuum furnace at 600-700°C followed by cooling; screen printing an aluminum alloy powder-containing printing paste onto the surface of the synthetic sheet diamond while simultaneously filling the holes; wrapping the material with 50-200 μm thick aluminum foil; baking it in a vacuum oven at 150-180°C for 30-45 minutes; and obtaining a preform after cooling; hot-pressing and sintering in a vacuum hot press furnace; and finally grinding and polishing to obtain the high thermal conductivity ultrathin diamond / aluminum composite material. The core layer of this invention is a certain thickness of high thermal conductivity synthetic sheet diamond, and the upper and lower surfaces are made of metallic aluminum. Hot-pressing and sintering yields a diamond / aluminum composite material with ultrathin thickness, high thermal conductivity, low thermal expansion, and weldable surface.

Description

Technical Field

[0001] This invention belongs to the field of composite material technology, and specifically relates to a method for preparing diamond / aluminum composite materials. Background Technology

[0002] The continuous innovation of electronic information technology has driven power devices towards two extremes: ever-increasing output power while miniaturizing device size, resulting in a significant increase in heat flux density. How to effectively dissipate this high heat flux density has become a key technology in system design.

[0003] Diamond is a three-dimensional material with extremely high thermal conductivity, exhibiting near-isotropic thermal conductivity in all directions, ranging from 1200 to 2000 W / mK. Diamond / aluminum is a novel composite material with a thermal conductivity (500–600 W / mK) 2–3 times that of traditional molybdenum-copper heat dissipation materials. Its coefficient of thermal expansion is close to that of semiconductor chip materials, and its density is much lower than that of molybdenum-copper, showing significant application potential in the field of electronic packaging.

[0004] Currently, in diamond / aluminum composites, the volume fraction of diamond particles is high, and the surface consists of an aluminum matrix and diamond particles, making nickel and gold plating difficult and resulting in poor weldability. Furthermore, most diamond / aluminum composites are prepared using a gas pressure melting process, which cannot simultaneously achieve high thermal conductivity and ultra-thinness. Patent CN 104313385 B describes an ultra-high thermal conductivity diamond / aluminum composite material with a diamond volume fraction of 55-70% and a thermal conductivity as high as 670 W / mK, but the thickness cannot be reduced to <0.5 mm.

[0005] Therefore, how to prepare an ultrathin diamond / aluminum composite material with high thermal conductivity, low thermal expansion, and weldable surface has become an urgent technical problem to be solved. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing a high thermal conductivity ultrathin diamond / aluminum composite material, wherein the middle core layer is a certain thickness of high thermal conductivity artificial sheet diamond, and the upper and lower surfaces are metallic aluminum. After hot pressing and sintering, a diamond / aluminum composite material with ultrathin, high thermal conductivity, low thermal expansion and surface weldability is obtained.

[0007] To achieve the above objectives, the following technical solution is adopted:

[0008] A method for preparing a high thermal conductivity ultrathin diamond / aluminum composite material includes the following steps:

[0009] (1) Laser cutting is used to process uniformly arranged through holes on artificial sheet diamond;

[0010] (2) A 100-200 nm thick metallic titanium protective layer was prepared on the surface of artificial sheet diamond using a vacuum magnetron sputtering titanium plating process.

[0011] (3) The artificial sheet diamond with titanium coating is heat-treated in a vacuum furnace at 600-700℃ and then cooled.

[0012] (4) Print the printing paste containing aluminum alloy powder onto the surface of artificial sheet diamond by screen printing and fill the holes at the same time. Wrap it with aluminum foil with a thickness of 50-200um, bake it in a vacuum oven at 150-180℃ for 30-45min, and obtain the preform after cooling.

[0013] (5) The obtained preforms are placed in a vacuum hot press furnace for hot pressing and sintering, and then ground and polished to obtain a high thermal conductivity ultrathin diamond / aluminum composite material.

[0014] According to the above scheme, the thermal conductivity of the artificial sheet diamond described in step 1 is 1800-2200 W / mK, and the volume resistivity (25℃) is >10. 15 Ω cm; thickness 0.2–0.3 mm, size 0.1–2 inches.

[0015] According to the above scheme, in step 1, the hole diameter is 0.3 to 0.5 mm and the hole spacing is 1 to 5 mm.

[0016] According to the above scheme, the vacuum magnetron sputtering titanium plating process conditions in step 2 include:

[0017] A sheet diamond is suspended inside a magnetron sputtering machine. The titanium target has a purity >99.99%. Argon gas with a purity of 99.99% is introduced at a flow rate of 30–40 sccm and a working pressure of 0.5–0.8 Pa. The bias voltage applied for magnetron sputtering titanium deposition is -50–60 V, and the power is 40–80 W. Pre-sputtering is performed first for 2–5 min, followed by titanium deposition for 5–10 min.

[0018] According to the above scheme, the vacuum furnace heat treatment time in step 3 is 20-40 minutes, and the vacuum degree is <10. -2 Pa.

[0019] According to the above scheme, the preparation method of the printing paste containing aluminum alloy powder in step 4 includes the following steps:

[0020] A resin mixture solution is obtained by mixing polyester resin, dibasic acid ester organic solvent, and isocyanate curing agent in a mass ratio of 4:5:1.

[0021] A printing paste containing aluminum alloy powder is obtained by mixing aluminum alloy powder and resin solution at a mass ratio of 2:1.

[0022] According to the above scheme, the aluminum alloy powder in step 4 is prepared by a water-air combined atomization powder preparation process, with a particle size of 3-10 μm, preferably 3-5 μm; the composition contains Si: 6-8 wt%, Mg: 1-3 wt%, Cu: 0.5-1 wt%, Zr: 0.2-0.5 wt%, Ti: 0.2-0.8 wt%, Mn: 0.2-0.5 wt%, and the balance is Al.

[0023] According to the above scheme, the printing thickness on the surface of the artificial sheet diamond in step 4 is 8-10 μm.

[0024] According to the above scheme, the hot pressing sintering process conditions in step 5 include:

[0025] Vacuum degree 10 -1 ~10 -2 Pa, in an inert atmosphere or a hydrogen-argon mixed reducing atmosphere with a hydrogen gas fraction of 5%; during the heating process, heat to 300-450°C at a rate of 3-5°C / min and hold for 30-50 min; then start pressurizing to a pressure of 1-3 MPa, while simultaneously heating to 600-620°C at a rate of 1-2°C / min and holding for 10 min.

[0026] The beneficial effects of this invention are as follows:

[0027] Synthetic sheet diamond possesses high thermal conductivity, but its high surface energy makes it difficult to achieve high-strength composites with other materials. This invention employs magnetron sputtering to prepare a protective titanium layer on the surface of sheet diamond. The surface titanium not only protects the diamond and reduces carbide formation but also forms intermetallic compounds such as Ti3Al and TiAl with aluminum, altering the wettability between diamond and aluminum. Studies have shown that a thick metal film on the diamond surface can have a thermal resistance effect, hindering the overall thermal conductivity of the diamond / aluminum ratio. Magnetron sputtering can effectively control the growth rate of titanium, ensuring its uniform coating on the surface of the synthetic diamond sheet. To ensure the adhesion of titanium to the sheet diamond surface, this invention performs vacuum heat treatment after magnetron sputtering. This heat treatment eliminates internal stress in the titanium film and, at a certain temperature, allows titanium to form titanium carbide with the carbon on the diamond surface, improving the bonding strength between the titanium film and the sheet diamond.

[0028] The aluminum alloy powder designed in this invention incorporates trace alloying elements such as Si, Zr, Cu, and Ti. One benefit is that it lowers the melting point of the aluminum alloy powder, allowing the aluminum foil to adhere well to the surface of the sheet diamond. Simultaneously, the trace elements diffuse into each other under the influence of the concentration gradient, forming a gradient material that improves the thermal cycling resistance of the diamond / aluminum structure. Since the maximum solid solubility of Si in metallic aluminum is 12%, this invention increases the Si content to 15-20%, which reduces the coefficient of thermal expansion of the surface aluminum layer, preventing cracking and peeling. Screen printing the aluminum alloy powder onto the surface of the sheet diamond acts as a buffer, ensuring that the sheet diamond does not break during hot pressing and sintering.

[0029] To improve the bonding strength and thermal shock resistance of aluminum and synthetic diamond sheets, this invention designs an "I"-shaped structure, incorporating through-holes in the synthetic diamond sheets. The aluminum alloy within the holes firmly connects the upper and lower aluminum layers into a single unit. This not only protects the synthetic sheet diamond but also adjusts the thermal expansion coefficient of diamond / aluminum by controlling the size and density of the holes, as well as regulating the electrical conductivity of the aluminum-diamond.

[0030] This invention employs high-temperature pressure sintering. Since an oxide film easily forms on the surface of aluminum alloy powder and aluminum foil during high-temperature sintering, hindering sintering, applying an external force during the sintering process can break the oxide film and improve the density of diamond / aluminum.

[0031] Because the manufacturing process of sheet diamond is quite special and it is difficult to achieve a high degree of flatness, this invention covers the surface with 50-200um aluminum foil to ensure surface machinability. After grinding and polishing, the surface roughness Ra≤0.2, diamond / aluminum thickness<0.5mm, and thermal conductivity>800W / mK, which can greatly meet the requirements of high-precision, high-thermal-conductivity heat sink components with high accuracy requirements.

[0032] This invention provides a high thermal conductivity ultrathin diamond / aluminum composite material and its preparation method, in which artificial sheet-like diamond sheets are used as the core layer and the surface is clad with a certain thickness of metallic aluminum. The upper and lower surfaces can be machined, which is used to manufacture high-precision, high thermal conductivity heat sink components with high surface finish requirements.

[0033] The preparation method provided by this invention has a simple preparation process and is suitable for large-scale industrial production. Attached Figure Description

[0034] Figure 1 : Flowchart of the preparation process of the high thermal conductivity ultrathin diamond / aluminum composite material of the present invention.

[0035] Figure 2 : Schematic diagram of the high thermal conductivity ultrathin diamond / aluminum composite material structure of this invention. Detailed Implementation

[0036] The following embodiments further illustrate the technical solution of the present invention, but are not intended to limit the scope of protection of the present invention.

[0037] A specific embodiment provides a method for preparing a high thermal conductivity ultrathin diamond / aluminum composite material, as shown in the attached figure. Figure 1 As shown:

[0038] (1) Laser cutting is used to process uniformly arranged through holes on artificial sheet diamond;

[0039] (2) A 100-200 nm thick metallic titanium protective layer was prepared on the surface of artificial sheet diamond using a vacuum magnetron sputtering titanium plating process.

[0040] (3) The artificial sheet diamond with titanium coating is heat-treated in a vacuum furnace at 600-700℃ and then cooled.

[0041] (4) Print the printing paste containing aluminum alloy powder onto the surface of artificial sheet diamond by screen printing and fill the holes at the same time. Wrap it with aluminum foil with a thickness of 50-200um, bake it in a vacuum oven at 150-180℃ for 30-45min, and obtain the preform after cooling.

[0042] (5) The obtained preform is placed in a vacuum hot press furnace for hot pressing and sintering. After grinding and polishing, a high thermal conductivity ultrathin diamond / aluminum composite material is obtained. See the attached diagram for the structural schematic. Figure 2 As shown.

[0043] Specifically, the artificial sheet diamond described in step 1 has a thermal conductivity of 1800–2200 W / mK and a volume resistivity (25°C) > 10. 15 Ω cm; thickness 0.2–0.3 mm, size 0.1–2 inches.

[0044] Specifically, in step 1, the hole diameter is 0.3 to 0.5 mm and the hole spacing is 1 to 5 mm.

[0045] Specifically, the vacuum magnetron sputtering titanium plating process conditions in step 2 include:

[0046] A sheet diamond is suspended inside a magnetron sputtering machine. The titanium target has a purity >99.99%. Argon gas with a purity of 99.99% is introduced at a flow rate of 30–40 sccm and a working pressure of 0.5–0.8 Pa. The bias voltage applied for magnetron sputtering titanium deposition is -50–60 V, and the power is 40–80 W. Pre-sputtering is performed first for 2–5 min, followed by titanium deposition for 5–10 min.

[0047] Specifically, in step 3, the vacuum furnace heat treatment time is 20-40 minutes, and the vacuum degree is <10. -2 Pa.

[0048] Specifically, the method for preparing the printing paste containing aluminum alloy powder in step 4 includes the following steps:

[0049] A resin mixture solution is obtained by mixing polyester resin, dibasic acid ester organic solvent, and isocyanate curing agent in a mass ratio of 4:5:1.

[0050] A printing paste containing aluminum alloy powder is obtained by mixing aluminum alloy powder and resin solution at a mass ratio of 2:1.

[0051] Specifically, the aluminum alloy powder mentioned in step 4 is prepared by a water-air combined atomization powder preparation process, with a particle size of 3-10 μm, preferably 3-5 μm; the composition contains Si: 6-8 wt%, Mg: 1-3 wt%, Cu: 0.5-1 wt%, Zr: 0.2-0.5 wt%, Ti: 0.2-0.8 wt%, Mn: 0.2-0.5 wt%, and the balance is Al.

[0052] Specifically, in step 4, the printing thickness on the surface of the artificial sheet diamond is 8–10 μm.

[0053] Specifically, the hot pressing sintering process conditions in step 5 include:

[0054] Vacuum degree 10 -1 ~10 -2 Pa, in an inert atmosphere or a hydrogen-argon mixed reducing atmosphere with a hydrogen gas fraction of 5%; during the heating process, heat to 300-450°C at a rate of 3-5°C / min and hold for 30-50 min; then start pressurizing to a pressure of 1-3 MPa, while simultaneously heating to 600-620°C at a rate of 1-2°C / min and holding for 10 min.

[0055] Example 1

[0056] 1) Select a 0.3mm thick, 25*25mm artificial sheet diamond and drill through it with a laser. The hole diameter is 0.5mm and the hole spacing is 4.5mm.

[0057] 2) Magnetron sputtering titanium thin film treatment on synthetic sheet diamond surface: The synthetic sheet diamond is vertically suspended in a magnetron sputtering coating machine, with a titanium target purity > 99.99%. Argon gas with a purity of 99.99% is introduced at a flow rate of 35 sccm and a working pressure of 0.6 Pa. Titanium is deposited by magnetron sputtering with a bias voltage of -50V and a power of 50W. Pre-sputtering is performed for 3 minutes, followed by titanium sputtering for 6 minutes, resulting in a titanium layer thickness of 120 nm.

[0058] 3) Place the titanium-plated artificial diamond sheet in a vacuum furnace and heat-treat at 650℃ for 30 minutes. Cool to room temperature and remove. The vacuum degree should be <10.-2 Pa.

[0059] 4) Polyester resin, dibasic acid ester organic solvent, and isocyanate curing agent are thoroughly mixed at a mass ratio of 4:5:1 to obtain a resin mixture solution. Aluminum alloy powder is mixed with the resin mixture solution at a mass ratio of 2:1 and then printed onto the surface of a titanium-plated diamond sheet. The aluminum alloy powder is a pre-alloyed powder prepared by a water-air combined atomization powder preparation process, with a particle size of 5μm. Its composition by mass fraction is: Si: 15%, Mg: 3%, Cu: 0.8%, Zr: 0.3%, Ti: 0.5%, Mn: 0.5%, Al: balance, and the printing thickness is approximately 8μm.

[0060] 5) Cover the screen-printed sheet diamond surface with a 100um aluminum foil, and bake it in a vacuum oven at 160℃ for 30 minutes. After cooling, a high thermal conductivity ultrathin diamond / aluminum composite material preform is obtained.

[0061] 6) The obtained preforms are placed in a vacuum hot press furnace for hot pressing sintering. The process conditions are as follows: vacuum degree of 6.5*10 -2 A hydrogen-argon mixed reducing atmosphere with a hydrogen gas fraction of 5% was used. The mixture was heated to 400°C at a rate of 3°C / min and held for 45 min. Then, pressure was increased to 2 MPa, and the mixture was simultaneously heated to 615°C at a rate of 2°C / min and held for 10 min. After grinding and polishing, a diamond / aluminum composite material with a thickness of 0.4 mm was obtained.

[0062] The high thermal conductivity ultrathin diamond / aluminum composite material prepared in this case exhibits a peel strength of 103 N / mm between the aluminum layer and the artificial sheet diamond, a comprehensive thermal conductivity of 882 W / Mk, and a coefficient of thermal expansion of 6.65 × 10⁻⁶. -6 / ℃.

[0063] Example 2

[0064] 1) Select a 0.2mm thick, 25*25mm large artificial diamond sheet and drill through it with a laser. The hole diameter is 0.3mm and the hole spacing is 3mm.

[0065] 2) Magnetron sputtering titanium film coating was performed on the surface of artificial sheet diamond with a thickness of 0.2 mm: The artificial sheet diamond was vertically suspended in a magnetron sputtering coating machine, and 99.99% pure argon gas was introduced at a flow rate of 35 sccm and a working pressure of 0.6 Pa. For magnetron sputtering titanium coating, a bias voltage of -50V and a power of 60W were applied; pre-sputtering was performed for 3 minutes, followed by titanium sputtering for 10 minutes, resulting in a titanium layer thickness of 200 nm.

[0066] 3) Place the titanium-plated artificial diamond sheet in a vacuum furnace and heat-treat at 650℃ for 30 minutes. Cool to room temperature and remove. The vacuum degree should be <10. -2 Pa.

[0067] 3) Polyester resin, dicarboxylic acid ester organic solvent, and isocyanate curing agent are thoroughly mixed at a mass ratio of 4:5:1 to obtain a resin mixture solution. Aluminum alloy powder is mixed with the resin mixture solution at a mass ratio of 2:1 and then printed onto the surface of a titanium-plated diamond sheet. The aluminum alloy powder is a pre-alloyed powder prepared by a water-air combined atomization powder preparation process, with a particle size of 5μm. Its composition by mass fraction is: Si: 20%, Mg: 1.5%, Cu: 0.8%, Zr: 0.3%, Ti: 0.6%, Mn: 0.3%, Al: balance, and the printing thickness is approximately 8μm.

[0068] 4) Cover the screen-printed sheet diamond surface with a 100um aluminum foil, and bake it in a vacuum oven at 160℃ for 30 minutes. After cooling, a high thermal conductivity ultrathin diamond / aluminum composite material preform is obtained.

[0069] 5) The obtained preforms are placed in a vacuum hot press furnace for hot pressing sintering. The process conditions are as follows: vacuum degree of 6.5*10 -2 A hydrogen-argon mixed reducing atmosphere with a hydrogen gas fraction of 5% was used. The mixture was heated to 400°C at a rate of 3°C / min and held for 45 min. Then, pressure was increased to 1 MPa, and the mixture was simultaneously heated to 615°C at a rate of 2°C / min and held for 10 min. After grinding and polishing, a diamond / aluminum composite material with a thickness of 0.3 mm was obtained.

[0070] The high thermal conductivity ultrathin diamond / aluminum composite material prepared in this case exhibits a peel strength of 140 N / mm between the aluminum layer and the artificial sheet diamond, a comprehensive thermal conductivity of 802 W / mk, and a coefficient of thermal expansion of 7.65 × 10⁻⁶. -6 / ℃.

[0071] Comparative Example 1

[0072] The thickness of the magnetron sputtered Ti film in Example 1 was varied, and the experimental results are shown in Table 1.

[0073] Table 1

[0074] Comparative experiment Magnetron sputtering Ti thin film thickness result 1 50nm Uneven coating, peel strength 60 N / mm, overall thermal conductivity 625 W / mk 2 120nm Uneven coating, peel strength 103 N / mm, overall thermal conductivity 882 W / mk 3 400nm Uneven coating, peel strength 82 N / mm, overall thermal conductivity 422 W / mk

[0075] Comparative Example 2

[0076] The pore distribution of the artificial diamond sheet in Example 1 was changed, and the experimental results are shown in Table 2.

[0077] Table 2

[0078]

[0079] Comparative Example 3

[0080] The hot pressing sintering parameters in Example 1 were changed, and the experimental results are shown in Table 3.

[0081] Table 3

[0082] Comparative experiment temperature pressure result 1 580℃ 2Mpa At excessively low temperatures, the peel strength is 2 N / mm, and voids are present at the joint. 2 615℃ 2Mpa The temperature was just right, the peel strength was 40 N / mm, and there were no voids at the joint. 3 650℃ 2Mpa The surface aluminum layer melts when the temperature is too high. 4 615℃ 0.5Mpa Insufficient pressure causes the aluminum foil to curl up. 5 615℃ 3Mpa How much pressure causes a sheet diamond to break?

[0083] The above comparison shows that the distribution of through holes in the synthetic diamond sheet, different magnetron sputtered titanium film thicknesses, excessively high or low sintering temperatures, and sintering pressure and time all affect product performance.

Claims

1. A method for preparing a high thermal conductivity ultrathin diamond / aluminum composite material, characterized in that... Includes the following steps: (1) Using laser cutting, uniformly arranged through holes are processed on artificial sheet diamond; (2) A 100-200 nm thick metallic titanium protective layer was prepared on the surface of artificial sheet diamond using a vacuum magnetron sputtering titanium plating process; (3) The artificial sheet diamond with titanium coating is heat-treated in a vacuum furnace at 600~700℃ and then cooled; (4) Print the printing paste containing aluminum alloy powder onto the surface of artificial sheet diamond by screen printing and fill the holes at the same time. Wrap it with aluminum foil with a thickness of 50~200μm, bake it in a vacuum oven at 150-180℃ for 30-45min, and obtain the preform after cooling. (5) The obtained preforms are placed in a vacuum hot press furnace for hot pressing and sintering, and then ground and polished to obtain a high thermal conductivity ultrathin diamond / aluminum composite material.

2. The preparation method of the high thermal conductivity ultrathin diamond / aluminum composite material as described in claim 1, characterized in that... The synthetic sheet diamond described in step 1 has a thermal conductivity of 1800~2200 W / mK and a volume resistivity of >10 at 25℃. 15 Ω·cm; thickness 0.2~0.3mm, size: 0.1~2 inches.

3. The preparation method of the high thermal conductivity ultrathin diamond / aluminum composite material as described in claim 1, characterized in that... In step 1, the hole diameter is 0.3~0.5mm and the hole spacing is 1~5mm.

4. The preparation method of the high thermal conductivity ultrathin diamond / aluminum composite material as described in claim 1, characterized in that... The vacuum magnetron sputtering titanium plating process conditions described in step 2 include: A sheet diamond is suspended inside a magnetron sputtering machine. The titanium target has a purity >99.99%. Argon gas with a purity of 99.99% is introduced at a flow rate of 30-40 sccm and a working pressure of 0.5-0.8 Pa. The bias voltage applied for magnetron sputtering titanium deposition is -50-60V, and the power is 40-80W. Pre-sputtering is performed first for 2-5 minutes, followed by titanium deposition for 5-10 minutes.

5. The method for preparing the high thermal conductivity ultrathin diamond / aluminum composite material as described in claim 1, characterized in that... In step 3, the vacuum furnace heat treatment time is 20-40 minutes, and the vacuum degree is <10. -2 Pa.

6. The method for preparing the high thermal conductivity ultrathin diamond / aluminum composite material as described in claim 1, characterized in that... The method for preparing the printing paste containing aluminum alloy powder in step 4 includes the following steps: A resin mixture solution is obtained by mixing polyester resin, dibasic acid ester organic solvent, and isocyanate curing agent in a mass ratio of 4:5:

1. A printing paste containing aluminum alloy powder is obtained by mixing aluminum alloy powder and resin solution at a mass ratio of 2:

1.

7. The method for preparing the high thermal conductivity ultrathin diamond / aluminum composite material as described in claim 1, characterized in that... The aluminum alloy powder mentioned in step 4 is prepared by a water-air combined atomization powder preparation process, with a particle size of 3~10μm; the composition contains Si: 15~20wt%, Mg: 1~3wt%, Cu: 0.5~1wt%, Zr: 0.2~0.5wt%, Ti: 0.2~0.8wt%, Mn: 0.2~0.5wt%, and the balance is Al.

8. The method for preparing the high thermal conductivity ultrathin diamond / aluminum composite material as described in claim 1, characterized in that... Step 4 involves printing a thickness of 8-10 μm on the surface of the artificial sheet diamond.

9. The method for preparing the high thermal conductivity ultrathin diamond / aluminum composite material as described in claim 1, characterized in that... The hot pressing sintering process conditions in step 5 include: Vacuum degree 10 -1 ~10 -2 Pa, in an inert atmosphere or a hydrogen-argon mixed reducing atmosphere with a hydrogen gas fraction of 5%; during the heating process, heat to 300-450℃ at a rate of 3-5℃ / min and hold for 30-50min; then start pressurizing to a pressure of 1-3MPa, while heating to 600-620℃ at a rate of 1-2℃ / min and holding for 10min.

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