High-elongation optical-grade beryllium material and preparation method thereof

Abstract

The invention discloses a high-elongation optical-grade beryllium material and a preparation method thereof, and belongs to the field of optical-grade beryllium materials. The preparation method comprises the steps that S1, spherical beryllium powder with the purity larger than or equal to 99.3%, the oxygen content smaller than or equal to 1400 ppm and the average particle size of 16-18 microns is prepared; s2, the spherical beryllium powder is subjected to vacuum hot pressing sintering, furnace cooling is conducted to the room temperature after sintering is finished, and a blank is obtained; the heating rate of the vacuum hot pressing sintering is 120-145 DEG C / h, the heat preservation temperature is 850-940 DEG C, the pressure preservation pressure is 22-25 MPa, and the heat preservation and pressure preservation time is 6-8 h; and S3, the blank is subjected to hot isostatic pressing, furnace cooling is conducted to the room temperature after hot isostatic pressing is finished, and the optical-grade beryllium material is obtained. The pressure of hot isostatic pressing is larger than or equal to 120 Mpa, the heat preservation temperature ranges from 650 DEG C to 750 DEG C, and the heat preservation and pressure maintaining time ranges from 2.5 h to 4.5 h. The ductility of the optical-grade beryllium material is larger than or equal to 10%.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical-grade beryllium materials, and particularly relates to an optical-grade beryllium material with high elongation and a preparation method thereof. Background Art

[0002] Due to its excellent properties such as low density, high specific stiffness, good thermal stability and thermal conductivity, beryllium materials are widely used in the optical field. For example, in space optical systems, optical mirror bodies need to be lightweight and maintain stable optical performance in complex temperature environments. Beryllium materials just meet these requirements and are often used to manufacture key optical components such as reflectors. In the manufacture of components such as the mirror support structure of large astronomical telescopes and the lens barrels of aerospace cameras, beryllium materials also play an irreplaceable role with their unique properties, which helps to improve the resolution, stability and overall performance of the optical system.

[0003] However, the elongation of optical-grade beryllium materials obtained by traditional preparation processes is relatively low. In practical applications, beryllium materials with low elongation are prone to brittle fracture when subjected to external forces or thermal stresses generated by temperature changes. For example, during the launch of space optical systems, they will withstand large vibration and shock loads, and components made of beryllium materials with low elongation may crack or even break due to the inability to effectively buffer the stress, seriously affecting the reliability and service life of the optical system. In some scenarios where the beryllium material needs to be plastically deformed to a certain extent to meet the complex optical structure design, the low elongation also limits the selection of processing techniques and the final forming of products, increasing the manufacturing difficulty and cost.

[0004] To improve the elongation of beryllium materials, some measures have been taken in the prior art. Some studies have adjusted the alloy composition and added a small amount of other elements to form beryllium alloys in the hope of improving their plasticity. However, this method may have a negative impact on the excellent optical and thermal properties of beryllium materials themselves, such as changing the thermal expansion coefficient matching, resulting in deformation of optical components during temperature changes and affecting the optical precision. There are also studies that have tried to improve the hot processing technology, such as using specific rolling or forging process parameters, but the effect is limited, and the process control is difficult, and the product quality stability is poor during the production process, making it difficult to achieve large-scale industrial production.

[0005] Therefore, it is of great practical significance to develop a high-elongation optical-grade beryllium material and its preparation method that can significantly improve the elongation of beryllium materials, ensure that their optical properties are not affected, and are suitable for large-scale production. Summary of the Invention

[0006] To solve the above technical problems, the present invention provides an optical-grade beryllium material with high elongation and a preparation method thereof. By using spherical beryllium powder with low oxygen content as the raw material and combining vacuum hot pressing sintering and hot isostatic pressing under double high temperature and high pressure, the elongation of the optical-grade beryllium material is improved, and at the same time, the production process is shortened and the process cost is reduced.

[0007] The first aspect of the present invention provides a preparation method of an optical-grade beryllium material with high elongation, and the preparation method includes:

[0008] Step S1: Prepare spherical beryllium powder with a purity ≥ 99.3%, an oxygen content ≤ 1400 ppm, and an average particle size of 16 - 18 μm.

[0009] Step S2: Perform vacuum hot pressing sintering on the spherical beryllium powder, and after sintering, cool it to room temperature with the furnace to obtain a blank.

[0010] The heating rate of the vacuum hot pressing sintering is 120 - 145 °C / h, the heat preservation temperature is 850 - 940 °C, the pressure holding pressure is 22 - 25 MPa, and the heat preservation and pressure holding time is 6 - 8 h.

[0011] Step S3: Perform hot isostatic pressing on the blank, and after completion, cool it to room temperature with the furnace to obtain the optical-grade beryllium material.

[0012] The pressure of the hot isostatic pressing is ≥ 120 Mpa, the heat preservation temperature is 650 - 750 °C, and the heat preservation and pressure holding time is 2.5 - 4.5 h.

[0013] According to the preparation method described in the first aspect of the present invention, in the step S1, the sphericity of the spherical beryllium powder is ≥ 87%.

[0014] According to the preparation method described in the first aspect of the present invention, in the step S1, the preparation process of the spherical beryllium powder is as follows:

[0015] Step S11: Inductively melt beryllium beads with a purity ≥ 99% to obtain a beryllium ingot.

[0016] Step S12: Use an atomization powder making process to make the beryllium ingot into spherical beryllium powder.

[0017] According to the preparation method described in the first aspect of the present invention, in the step S2, the heating rate of the vacuum hot pressing sintering is 120 - 135 °C / h, the heat preservation temperature is 880 - 920 °C, the pressure holding pressure is 23 - 24 MPa, and the heat preservation and pressure holding time is 6 - 8 h.

[0018] According to the preparation method described in the first aspect of the present invention, in the step S2, the heating rate of the vacuum hot pressing sintering is 120-125 °C / h, the heat preservation temperature is 890-900 °C, the pressure maintaining pressure is 23-24 MPa, and the heat preservation and pressure maintaining time is 6-8 h.

[0019] According to the preparation method described in the first aspect of the present invention, in the step S3, the pressure of the hot isostatic pressing is ≥130 Mpa, the heat preservation temperature is 670-720 °C, and the heat preservation and pressure maintaining time is 2.5-4.5 h.

[0020] According to the preparation method described in the first aspect of the present invention, in the step S3, the pressure of the hot isostatic pressing is ≥140 Mpa, the heat preservation temperature is 680-700 °C, and the heat preservation and pressure maintaining time is 2.5-4.5 h.

[0021] The second aspect of the present invention provides an optical grade beryllium material with high elongation, and the optical grade beryllium material is prepared by using the foregoing preparation method.

[0022] According to the optical grade beryllium material described in the second aspect of the present invention, the tensile strength of the optical grade beryllium material is 420-435 MPa, the elongation is ≥10%, and the difference between the transverse and longitudinal thermal expansion coefficients is <1.3×10 -7 / °C.

[0023] According to the optical grade beryllium material described in the second aspect of the present invention, the beryllium oxide content of the optical grade beryllium material is ≤3000 ppm, and the purity is ≥99.2%.

[0024] The solution proposed by the present invention has the following technical effects:

[0025] By using spherical beryllium powder with low oxygen content as the raw material and combining vacuum hot pressing sintering and hot isostatic pressing with double high temperature and high pressure treatment, the present invention improves the elongation of the optical grade beryllium material, and at the same time shortens the production process and reduces the process cost. Detailed Embodiments

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0027] In the first aspect of this embodiment, a preparation method for an optical grade beryllium material with high elongation is proposed, and the preparation method includes:

[0028] Step S1, preparing spherical beryllium powder.

[0029] Step S2: Vacuum hot-press sinter the spherical beryllium powder, and after sintering is completed, cool it in the furnace to room temperature to obtain a blank.

[0030] Step S3: Hot isostatic press the blank, and after completion, cool it in the furnace to room temperature to obtain the optical-grade beryllium material.

[0031] In this embodiment, spherical beryllium powder with high fluidity is used as the raw material. On the one hand, it is beneficial to the forming of beryllium materials; on the other hand, spherical beryllium powder can increase the packing density, reduce the porosity, and increase the density of beryllium materials. In addition, spherical beryllium powder can better promote the sintering performance during the vacuum hot-press sintering process in this embodiment. Specifically, the specific surface area of spherical beryllium powder is relatively small and uniform, and the atomic diffusion between particles is easier to carry out, which can better improve the strength and toughness of the sintered body (blank).

[0032] In addition, this embodiment uses the vacuum hot-press sintering forming combined with the hot isostatic pressing process to replace the conventional cold isostatic pressing combined with the hot isostatic pressing process. Compared with the cold isostatic pressing process, the degassing of the powder state in the vacuum hot-press sintering process is relatively more thorough. Especially in reducing the oxygen content of the powder, the vacuum hot-press sintering has more advantages. For optical-grade beryllium materials, a low oxide content can make their optical properties better and their chemical stability stronger. At the same time, the applicant has found through research that the density of the blank obtained by vacuum hot-press sintering is approximately 1.8 kg / m 3 , while the density of the blank after cold isostatic pressing is approximately 1.4 kg / m 3 ; It can be seen that vacuum hot-press sintering reduces the porosity of the blank, increases the density of the blank, and greatly improves the material properties, especially the elongation.

[0033] Finally, the vacuum hot-press sintering forming combined with the hot isostatic pressing process in this embodiment greatly shortens the production cycle compared with the existing process (conventional cold isostatic pressing combined with the hot isostatic pressing process), which can be shortened from 15 days to 5 days.

[0034] In step S1, prepare spherical beryllium powder.

[0035] The purity of the spherical beryllium powder is ≥99.3%, the oxygen content is ≤1400 ppm, and the average particle size is 16 - 18 μm.

[0036] The lower the oxide content, the more excellent the optical properties of beryllium materials. In order to ensure that the beryllium oxide content of the optical-grade beryllium materials in this embodiment is ≤3000 ppm, in terms of raw material selection, the oxide content of the spherical beryllium powder in this embodiment is strictly limited to ≤1400 ppm, so that the product beryllium materials have more stable mechanical and chemical properties.

[0037] The particle size of spherical beryllium powder is too fine, and its oxide content is higher, the fluidity is poor, and the sintering forming performance is poor. However, when the particle size of spherical beryllium powder exceeds 18 μm, the density of the product beryllium material is low, resulting in poor mechanical properties such as strength and elongation. After a large number of experiments, the applicant found that when the average particle size of spherical beryllium powder is limited to 16 - 18 μm, the tensile strength of the product beryllium material is ≥420 MPa, the elongation is ≥10%, and the difference between the transverse and longitudinal thermal expansion coefficients is < 1.3×10 -7 / ℃.

[0038] In some embodiments, in the step S1, the sphericity of the spherical beryllium powder is ≥87%.

[0039] Spherical beryllium powder has high fluidity, which is beneficial to forming. At the same time, spherical beryllium powder improves the packing density, reduces the porosity, and increases the density. In addition, spherical beryllium powder can better promote the sintering performance in the subsequent vacuum hot pressing sintering process, and the specific surface area of spherical powder is relatively small and uniform, and the atomic diffusion between particles is easier to carry out, thus further improving the strength and toughness of the sintered body. Therefore, the higher the sphericity of spherical beryllium powder, the better, and the minimum cannot be less than 87%.

[0040] In some embodiments, in the step S1, the preparation process of the spherical beryllium powder is as follows:

[0041] Step S11: Induction melting of beryllium beads with a purity ≥99% to obtain a beryllium ingot;

[0042] Step S12: Using an atomization powder making process to make the beryllium ingot into spherical beryllium powder.

[0043] In this embodiment, an atomization powder making process is selected to prepare spherical beryllium powder, and its powder uniformity is better, and it can better promote the sintering performance in the subsequent vacuum hot pressing sintering process.

[0044] In step S2, the spherical beryllium powder is subjected to vacuum hot pressing sintering, and after sintering, it is cooled to room temperature with the furnace to obtain a blank.

[0045] The heating rate of the vacuum hot pressing sintering is 120 - 145℃ / h, the holding temperature is 850 - 940℃, the holding pressure is 22 - 25 MPa, and the holding and pressing time is 6 - 8 h.

[0046] Theoretically, the lower the heating rate, the better. However, considering the manufacturing cost, manufacturing cycle and equipment loss (high temperature and high pressure), the heating rate in this embodiment is limited to 120 - 145℃ / h.

[0047] The raw material selected in this embodiment is spherical beryllium powder with good fluidity. Therefore, the degassing and sintering forming of the powder can be completed only at a low holding temperature of 850 - 940 °C and a low pressure of 22 - 25 MPa. In addition, when the holding time under pressure is less than 6 h, it is difficult for the spherical beryllium powder to densify. When it is greater than 8 h, the degree of densification of the spherical beryllium powder does not increase significantly. Considering both cost, manufacturing cycle, and equipment loss, the holding time under pressure in this embodiment is limited to 6 - 8 h.

[0048] In some embodiments, in the step S2, the heating rate of the vacuum hot pressing sintering is 120 - 135 °C / h, the holding temperature is 880 - 920 °C, the pressure under pressure is 23 - 24 MPa, and the holding time under pressure is 6 - 8 h.

[0049] In some embodiments, in the step S2, the heating rate of the vacuum hot pressing sintering is 120 - 125 °C / h, the holding temperature is 890 - 900 °C, the pressure under pressure is 23 - 24 MPa, and the holding time under pressure is 6 - 8 h.

[0050] In step S3, the green body is subjected to hot isostatic pressing, and after completion, it is cooled to room temperature with the furnace to obtain the optical grade beryllium material.

[0051] The pressure of the hot isostatic pressing is ≥120 Mpa, the holding temperature is 650 - 750 °C, and the holding time under pressure is 2.5 - 4.5 h.

[0052] When the pressure of the hot isostatic pressing is ≥120 MPa, further densification of the green body will occur. The process of the present invention uses vacuum hot pressing sintering instead of the conventional cold isostatic pressing process. The billet has much higher strength and density than that after cold isostatic pressing. Therefore, the hot isostatic pressing link in this embodiment mainly plays a heat treatment role to further reduce the porosity and increase the density, thereby improving the elongation of the product beryllium material. Secondly, considering the processing cost, processing cycle, and machine loss, the holding temperature of the hot isostatic pressing is limited to 650 - 750 °C, and the holding time under pressure is 2.5 - 4.5 h.

[0053] In some embodiments, in the step S3, the pressure of the hot isostatic pressing is ≥130 Mpa, the holding temperature is 670 - 720 °C, and the holding time under pressure is 2.5 - 4.5 h.

[0054] In some embodiments, in the step S3, the pressure of the hot isostatic pressing is ≥140 Mpa, the holding temperature is 680 - 700 °C, and the holding time under pressure is 2.5 - 4.5 h.

[0055] In the second aspect of this embodiment, an optical grade beryllium material is proposed, and the optical grade beryllium material is prepared by using the aforementioned preparation method.

[0056] In some embodiments, the tensile strength of the optical grade beryllium material is 420 - 435 MPa, the elongation rate is ≥10%, and the difference between the transverse and longitudinal thermal expansion coefficients is < 1.3*10 -7 / °C.

[0057] In some embodiments, the beryllium oxide content of the optical grade beryllium material is ≤3000 ppm, and the purity is ≥99.2%. Specific Example 1

[0059] First step: High-purity beryllium beads with a purity of 99.2% are induction melted to obtain a beryllium ingot.

[0060] Second step: The beryllium ingot is atomized to produce spherical beryllium powder. The spherical beryllium powder has a purity of 99.3%, an oxygen content of 1170 ppm, an average particle size of 17.1 μm, and a powder sphericity of 87%.

[0061] Third step: The spherical beryllium powder is loaded into a graphite mold, baked, and then placed in a vacuum hot press furnace for heating and sintering. After sintering, it is cooled to room temperature with the furnace, and then demolded to obtain a blank.

[0062] Process conditions: Heating starts at a vacuum of 1*10 -2 Pa, the heating rate is 145°C / h, the holding temperature is 850°C, the holding pressure is 22 MPa, and the holding time is 6 h.

[0063] Fourth step: The hot-pressed blank is directly subjected to hot isostatic pressing, and after completion, it is cooled to room temperature with the furnace to obtain the optical grade beryllium material.

[0064] Process conditions: Pressing is carried out under a pressure of 128 MPa, the holding temperature is 650°C, and the holding time is 3.0 h.

[0065] After testing, the optical grade beryllium material prepared in Specific Example 1 has a tensile strength of 422 MPa, an elongation rate of 10.7%, a beryllium oxide content of 2370 ppm, a purity of 99.2%, and the difference between the transverse and longitudinal thermal expansion coefficients (isotropic) of 1.28*10 -7 / °C. Specific Example 2

[0067] First step: High-purity beryllium beads with a purity of 99.3% are induction melted to obtain a beryllium ingot.

[0068] Second step: The beryllium ingot is atomized to produce spherical beryllium powder. The spherical beryllium powder has a purity of 99.3%, an oxygen content of 1200 ppm, an average particle size of 16.2 μm, and a powder sphericity of 88%.

[0069] Third step: The spherical beryllium powder is loaded into a graphite mold, baked, and then placed in a vacuum hot press furnace for heating and sintering. After sintering, it is cooled to room temperature with the furnace, and then demolded to obtain a blank.

[0070] Process conditions: Starting from a vacuum of 2*10 -2 Pa, heat up at a rate of 140 °C / h, hold the temperature at 880 °C, maintain the pressure at 23 MPa, and hold for 6.5 h.

[0071] Step 4: Directly perform hot isostatic pressing on the hot-pressed blank, and then cool it in the furnace to room temperature to obtain the optical-grade beryllium material.

[0072] Process conditions: Press under a pressure of 130 MPa, hold the temperature at 680 °C, and hold for 2.5 h.

[0073] After testing, the tensile strength of the optical-grade beryllium material prepared in Specific Example 2 is 430 MPa, the elongation is 11.2%, the beryllium oxide content is 2540 ppm, the purity is 99.3%, and the difference in thermal expansion coefficient between the transverse and longitudinal directions (isotropic) is 1.24*10 -7 / °C. Specific Example 3

[0075] Step 1: Obtain a beryllium ingot by induction melting of high-purity beryllium beads with a purity of 99.5%.

[0076] Step 2: Obtain spherical beryllium powder by atomizing the beryllium ingot. The purity of the spherical beryllium powder is 99.4%, the oxygen content is 1320 ppm, the average particle size is 17.8 μm, and the powder sphericity is 89%.

[0077] Step 3: Load the spherical beryllium powder into a graphite mold, bake it, and then put it into a vacuum hot pressing furnace for heating and sintering. After sintering, cool it in the furnace to room temperature, and then demold to obtain a blank.

[0078] Process conditions: Starting from a vacuum of 3*10 -2 Pa, heat up at a rate of 135 °C / h, hold the temperature at 900 °C, maintain the pressure at 24 MPa, and hold for 7 h.

[0079] Step 4: Directly perform hot isostatic pressing on the hot-pressed blank, and then cool it in the furnace to room temperature to obtain the optical-grade beryllium material.

[0080] Process conditions: Press under a pressure of 132 MPa, hold the temperature at 700 °C, and hold for 3.5 h.

[0081] After testing, the tensile strength of the optical-grade beryllium material prepared in Specific Example 3 is 426 MPa, the elongation is 10.9%, the beryllium oxide content is 2700 ppm, the purity is 99.3%, and the difference in thermal expansion coefficient between the transverse and longitudinal directions (isotropic) is 1.26*10 -7 / °C. Specific Example 4

[0083] Step 1: The high-purity beryllium beads with a purity of 99.3% are subjected to induction melting to obtain a beryllium ingot.

[0084] Step 2: The beryllium ingot is atomized to produce spherical beryllium powder. The spherical beryllium powder has a purity of 99.5%, an oxygen content of 1380 ppm, an average particle size of 18.0 μm, and a powder sphericity of 90%.

[0085] Step 3: The spherical beryllium powder is loaded into a graphite mold, baked, and then placed in a vacuum hot press furnace for heating and sintering. After sintering, it is cooled to room temperature in the furnace, and then demolded to obtain a blank.

[0086] Process conditions: Heating starts at a vacuum of 3×10 -2 Pa, the heating rate is 120 °C / h, the holding temperature is 940 °C, the holding pressure is 25 MPa, and the holding time is 8 h.

[0087] Step 4: The hot-pressed blank is directly subjected to hot isostatic pressing, and after completion, it is cooled to room temperature in the furnace to obtain the optical-grade beryllium material.

[0088] Process conditions: Pressing is carried out under a pressure of 134 MPa, the holding temperature is 750 °C, and the holding time is 4.0 h.

[0089] After testing, the tensile strength of the optical-grade beryllium material prepared in Specific Example 4 is 430 MPa, the elongation is 11.2%, the beryllium oxide content is 2810 ppm, the purity is 99.4%, and the difference in thermal expansion coefficients in the transverse and longitudinal directions (isotropic) is 1.22×10 -7 / °C. Specific Example 5

[0091] Step 1: The high-purity beryllium beads with a purity of 99.3% are subjected to induction melting to obtain a beryllium ingot.

[0092] Step 2: The beryllium ingot is atomized to produce spherical beryllium powder. The spherical beryllium powder has a purity of 99.4%, an oxygen content of 1280 ppm, an average particle size of 16.5 μm, and a powder sphericity of 87%.

[0093] Step 3: The spherical beryllium powder is loaded into a graphite mold, baked, and then placed in a vacuum hot press furnace for heating and sintering. After sintering, it is cooled to room temperature in the furnace, and then demolded to obtain a blank.

[0094] Process conditions: Heating starts at a vacuum of 2×10 -2 Pa, the heating rate is 130 °C / h, the holding temperature is 890 °C, the holding pressure is 23.5 MPa, and the holding time is 7.5 h.

[0095] Step 4: The hot-pressed blank is directly subjected to hot isostatic pressing, and after completion, it is cooled to room temperature in the furnace to obtain the optical-grade beryllium material.

[0096] Process conditions: Compression is carried out under a pressure of 140 MPa, the heat preservation temperature is 720 °C, and the heat preservation and pressure holding time is 4.5 h.

[0097] After testing, the tensile strength of the optical grade beryllium material prepared in Specific Example 1 is 435 MPa, the elongation is 11.7%, the beryllium oxide content is 2700 ppm, the purity is 99.3%, and the difference in thermal expansion coefficient between the transverse and longitudinal directions (isotropy) is 1.27*10 -7 / °C.

[0098] In summary, the solution proposed by the present invention has the following technical effects:

[0099] By using spherical beryllium powder with low oxygen content as the raw material and combining vacuum hot pressing sintering and hot isostatic pressing with double high temperature and high pressure treatment, the present invention improves the elongation of the optical grade beryllium material, and at the same time shortens the production process and reduces the process cost.

[0100] The above embodiments only represent several implementation manners of the present application. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the appended claims.

Claims

1. A preparation method of an optical-grade beryllium material with high elongation rate, characterized in that, The preparation method includes the following steps: Step S1: Prepare spherical beryllium powder with a purity ≥ 99.3%, an oxygen content ≤ 1400 ppm, and an average particle size of 16 - 18 μm; Step S2: Perform vacuum hot - pressing sintering on the spherical beryllium powder, and after sintering, cool it in the furnace to room temperature to obtain a blank; For the vacuum hot - pressing sintering, the heating rate is 120 - 145 °C / h, the holding temperature is 850 - 940 °C, the holding pressure is 22 - 25 MPa, and the holding time is 6 - 8 h; Step S3: Perform hot isostatic pressing on the blank, and after completion, cool it in the furnace to room temperature to obtain the optical - grade beryllium material; For the hot isostatic pressing, the pressure ≥ 120 Mpa, the holding temperature is 650 - 750 °C, and the holding time is 2.5 - 4.5 h.

2. The preparation method according to claim 1, characterized in that, In the step S1, the sphericity of the spherical beryllium powder ≥ 87%.

3. The preparation method according to claim 1, characterized in that, In the step S1, the preparation process of the spherical beryllium powder is as follows: Step S11: Inductively melt beryllium beads with a purity ≥ 99% to obtain a beryllium ingot; Step S12: Use an atomization powder - making process to make the beryllium ingot into spherical beryllium powder.

4. The preparation method according to claim 1, characterized in that, In the step S2, for the vacuum hot - pressing sintering, the heating rate is 120 - 135 °C / h, the holding temperature is 880 - 920 °C, the holding pressure is 23 - 24 MPa, and the holding time is 6 - 8 h.

5. The preparation method according to claim 1, characterized in that In the step S2, for the vacuum hot - pressing sintering, the heating rate is 120 - 125 °C / h, the holding temperature is 890 - 900 °C, the holding pressure is 23 - 24 MPa, and the holding time is 6 - 8 h.

6. The preparation method according to claim 1, wherein In the step S3, for the hot isostatic pressing, the pressure ≥ 130 Mpa, the holding temperature is 670 - 720 °C, and the holding time is 2.5 - 4.5 h.

7. The preparation method according to claim 1, wherein In the step S3, for the hot isostatic pressing, the pressure ≥ 140 Mpa, the holding temperature is 680 - 700 °C, and the holding time is 2.5 - 4.5 h.

8. An optical-grade beryllium material with a high elongation rate, characterized in that, The optical - grade beryllium material is prepared by the preparation method described in any one of claims 1 - 7.

9. The optical grade beryllium material according to claim 8, wherein The tensile strength of the optical-grade beryllium material is 420-435 MPa, the elongation rate is ≥10%, and the difference between the transverse and longitudinal thermal expansion coefficients is <1.3*10 -7 / °C.

10. The optical-grade beryllium material according to claim 9, wherein The beryllium oxide content of the optical - grade beryllium material ≤ 3000 ppm, and the purity ≥ 99.2%.