Method for preparing beryllium-aluminum alloy based on double-melt mixing atomization

Abstract

The invention provides a method for preparing beryllium-aluminum alloy based on double-melt mixing atomization, and belongs to the technical field of non-ferrous metal material metallurgy manufacturing. The method comprises the steps that firstly, a beryllium ingot and an aluminum ingot are smelted through a vacuum smelting technology and then mixed, the mixed melt is added into a crucible above a nozzle of an atomizing chamber to be stirred and smelted, and the melt passes through a rapid solidification cavity in a free falling mode under the action of the nozzle and centrifugal force and falls into a powder collector, so that beryllium-aluminum pre-alloy powder is prepared; and then, the beryllium-aluminum alloy is prepared through spark plasma sintering. According to the method, by means of the mode that a free falling body passes through a rapid solidification channel, atomized particles are shrunk to be spherical while completing instantaneous solidification under the high supercooling degree, grain growth is effectively inhibited, and the internal structure of the powder is of a submicron-level refined structure. The fine grain structure enhances the diffusion driving force in the subsequent sintering process of the powder, so that the material can be densified at a lower temperature in a shorter time.

Description

Technical Field

[0001] This invention belongs to the field of non-ferrous metal materials metallurgical manufacturing technology, specifically relating to a method for preparing beryllium aluminum alloy based on dual melt mixing atomization. Background Technology

[0002] Beryllium-aluminum alloys combine the high stiffness of beryllium with the excellent toughness of aluminum, exhibiting low density, high specific strength, high specific stiffness, and excellent thermal stability, making them important for applications in electronics, automotive manufacturing, and aerospace. The high-melting-point beryllium phase, as a particulate phase, is encapsulated by the low-melting-point aluminum matrix phase, thus giving beryllium-aluminum alloys the characteristics of aluminum-based composite materials, combining the high strength of the beryllium phase with the high toughness of the aluminum phase. However, the inherent brittleness of beryllium, the low solubility between beryllium and aluminum, and the lack of effective technologies for manufacturing beryllium-aluminum alloys limit their further applications. Therefore, it is crucial to employ suitable technologies to prepare beryllium-aluminum alloys while simultaneously optimizing the microstructure of beryllium-aluminum.

[0003] The raw material systems for preparing beryllium-aluminum alloys mainly include two forms: beryllium powder / aluminum powder mixtures and pre-alloyed powders. The development of beryllium powder preparation technology has gone through three stages: early disc milling and ball milling processes produced flake powders that were prone to anisotropy and suffered from defects such as large particle size and insufficient purity; the cold air jet impingement technology developed in the 1970s utilized the cold brittleness of beryllium to prepare blocky, irregularly shaped powders, improving production efficiency while also offering lower costs; in the early 21st century, the United States achieved a breakthrough in atomization powder preparation technology, producing spherical powders. Their excellent flow characteristics can improve powder filling density, providing a new approach to solving the forming defects of traditional flake powders and promoting the development of near-net-shape forming technology. Currently, my country still uses the cold air jet impingement method to prepare beryllium powder and has not conducted engineering application research on beryllium powder atomization powder preparation technology. Therefore, there is an urgent need to break through the atomization powder preparation technology for spherical beryllium powder and beryllium-aluminum pre-alloyed powders.

[0004] Traditional powder metallurgy employs a cold isostatic pressing followed by hot isostatic pressing method, which is characterized by long preparation cycles, high costs, complex processes, and demanding equipment requirements. Due to beryllium's extremely high reactivity, it readily forms nanoscale oxide films on its surface, hindering particle rearrangement and densification during sintering. In contrast, spark plasma sintering (SPSS) offers numerous advantages, including lower sintering temperatures, faster heating rates, shorter sintering times, higher production efficiency, controllable microstructure, uniform heating, higher product density, and energy and cost savings. Furthermore, during SPSS, the pulsed current directly acts on the powder, generating discharge heating between the powder particles, resulting in uniform heating of the sintered body and promoting densification. Therefore, this invention proposes a process for preparing beryllium-aluminum alloys using a combination of "dual-melt mixing + rapid solidification" atomization technology and SPSS. Summary of the Invention

[0005] This invention aims to propose a method for preparing beryllium-aluminum alloys based on dual-melt mixing and atomization. The method employs a dual-melt mixing and atomization scheme combined with spark plasma sintering technology. The core of this method lies in utilizing the two melts, which, after mixing, enter the atomization chamber and, under the action of nozzles and centrifugal force, freely fall through a rapid solidification zone, producing spherical pre-alloyed powder under surface tension. The interconnected three-dimensional network structure of the beryllium and aluminum phases, combined with the activation effect of spark plasma, synergistically achieves efficient densification of the beryllium-aluminum alloy.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A method for preparing beryllium-aluminum alloy based on dual-melt mixing atomization involves firstly, using a vacuum melting process, melting beryllium ingots and aluminum ingots separately and then mixing them. The mixed melt is then added to a crucible above the nozzle of the atomization chamber for stirring and melting. Under the action of the nozzle and centrifugal force, the melt falls freely through a rapid solidification chamber and into a powder collector to prepare beryllium-aluminum pre-alloyed powder. Subsequently, the beryllium-aluminum alloy is prepared by spark plasma sintering.

[0008] As a preferred technical solution of the present invention, the specific steps of the preparation method are as follows:

[0009] Step 1: Dry the beryllium ingot and aluminum ingot samples;

[0010] Step 2: Place the beryllium ingot and aluminum ingot into two separate crucibles. In a vacuum chamber, heat the crucible containing the beryllium ingot to 800-900 ℃ for 2-3 hours, then raise the temperature to 1500-1600 ℃ and hold for 1-2 hours to molten the ingot. In the same vacuum chamber, heat the crucible containing the aluminum ingot to 400-500 ℃ for 2-3 hours, then raise the temperature to 700-800 ℃ and hold for 1-2 hours to molten the ingot.

[0011] Step 3: After mixing the beryllium melt and aluminum melt, place them in the crucible above the atomizing nozzle, keep them warm and stir;

[0012] Step 4: The mixed melt is injected through a rotating nozzle into an atomization chamber where it is blown and cooled by strong argon gas. It falls freely through a rapid solidification chamber and shrinks into a spherical shape under the action of surface tension and rapid cooling and solidification.

[0013] Step 5: Load the beryllium-aluminum pre-alloyed powder obtained in the powder collector into a mold, then place the mold in a manual hydraulic press and pre-press the powder under a pressure of 10 MPa for 1-2 minutes. Place the pre-pressed mold into the discharge plasma furnace and evacuate to a vacuum of 1.0 × 10⁻⁶. -2 Pa, set the sintering temperature to 550~625 ℃, the heating rate to 50 ℃ / min, the sintering pressure to 50 MPa, and the holding time to 5 min.

[0014] As a preferred embodiment of the present invention, the drying temperature in step 1 of the preparation method is 250°C. The weight ratio of beryllium ingot to aluminum ingot is 6~8:2~4.

[0015] As a preferred technical solution of the present invention, in step 2 of the preparation method, the aluminum ingot is wrapped with aluminum foil and then placed in a crucible for melting.

[0016] As a preferred technical solution of the present invention, in step 3 of the preparation method, the temperature is kept at 1500~1600 ℃ and stirred for 30~60 min.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0018] (1) Compared with mechanical alloying, the spherical pre-alloyed beryllium aluminum powder prepared by the "dual melt mixing + rapid solidification" atomization method can eliminate the stress concentration problem at the beryllium / aluminum two-phase interface and avoid element segregation during the pressing stage; the obtained spherical beryllium aluminum alloy powder can significantly reduce the anisotropy of spherical powder, and the good spherical morphology of the powder gives it good fluidity and high filling density; the material can be directly formed by hot isostatic pressing and other forming processes, which can optimize the mechanical properties of the alloy while simplifying the process.

[0019] (2) This invention achieves in-situ rapid solidification during high-speed spraying after mixing two melts, allowing the beryllium and aluminum phases to undergo high-speed nucleation and solidification simultaneously after molten mixing, thus naturally forming a continuous three-dimensional interconnected network structure. This structure differs from the isolated particle distribution of traditional solid-phase mixed powders, significantly improving the continuity of load transfer within the powder and enhancing the overall mechanical properties of the alloy sintered body.

[0020] (3) This invention utilizes the method of free fall through a rapid solidification channel to enable atomized particles to instantly solidify under high supercooling while shrinking into a spherical shape, effectively inhibiting grain growth and resulting in a submicron-level refined structure inside the powder. This fine grain structure enhances the diffusion driving force in the subsequent sintering process of the powder, enabling the material to achieve densification at a lower temperature and in a shorter time. Attached Figure Description

[0021] Figure 1 A schematic diagram of the process for preparing beryllium-aluminum pre-alloyed powder using a dual-melt mixing and rapid solidification atomization method.

[0022] Figure 2 The image shows the SEM image of the morphology of the beryllium aluminum pre-alloyed powder prepared in Example 1.

[0023] Figure 3 SEM image of the surface morphology of the beryllium aluminum alloy prepared in Example 1. Detailed Implementation

[0024] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings.

[0025] Example 1

[0026] See Figure 1 This embodiment proposes a method for preparing beryllium-aluminum alloy based on dual-melt mixing atomization. A vacuum melting process is employed, where beryllium and aluminum are melted and mixed. The resulting melt is then added to a crucible above the nozzle in the atomization chamber, stirred, and melted. Under the action of the nozzle and centrifugal force, the melt falls freely through a rapid solidification chamber, propelled by strong argon gas, and finally falls into a powder collector, yielding beryllium-aluminum pre-alloy powder with a beryllium-aluminum mass ratio of 6:4. Finally, the beryllium-aluminum alloy is prepared by spark plasma sintering. The raw materials used are: 120 g beryllium ingot and 80 g aluminum ingot. The beryllium ingot was purchased from Shanghai Taiyang Technology Co., Ltd., and the aluminum ingot was purchased from Anhui Kaifei New Material Technology Co., Ltd.

[0027] The preparation method steps are as follows:

[0028] Step 1: Dry the beryllium ingot and aluminum ingot samples at 250 °C, with a weight ratio of 6:4.

[0029] Step 2: Place the beryllium ingot and aluminum ingot into two separate crucibles. In a vacuum chamber, heat the crucible containing the beryllium ingot to 850°C for 2.5 hours, then raise the temperature to 1550°C and hold for 1.5 hours until it becomes molten. In a vacuum chamber, heat the crucible containing the aluminum ingot to 450°C for 2 hours, then raise the temperature to 750°C and hold for 1.5 hours until it becomes molten. Wrap the aluminum ingot in aluminum foil and place it into the crucible.

[0030] Step 3: After mixing the beryllium melt and the aluminum melt, place them in the crucible above the atomizing nozzle, keep them at 1550 ℃ and stir for 45 min.

[0031] Step 4: The mixed melt is injected through a rotating nozzle into an atomization chamber where it is blown and cooled by strong argon gas. It falls freely through a rapid solidification chamber about 3 m long and shrinks into a spherical shape under the action of surface tension and rapid cooling solidification.

[0032] Step 5: The beryllium-aluminum pre-alloyed powder obtained in the powder collector is loaded into a 20 mm diameter mold (pre-laid with carbon paper). The mold is then placed in a manual hydraulic press and pre-pressed at 10 MPa for 2 minutes. The pre-pressed mold is then loaded into a spark plasma sintering furnace and evacuated to a vacuum of 1.0 × 10⁻⁶. -2 Pa, the sintering temperature is set to 600 ℃, the heating rate is 50 ℃ / min, the sintering pressure is 50 MPa, and the holding time is 5 min.

[0033] Step 6: After the mold has cooled, demold and remove the carbon paper coating from the surface of the beryllium aluminum alloy sample.

[0034] Example 2

[0035] This embodiment compares the properties of beryllium-aluminum pre-alloyed powders with different beryllium-aluminum composition ratios and their samples. The preparation steps in this embodiment are the same as in Example 1, except that the ratio of beryllium to aluminum in the prepared spherical beryllium-aluminum pre-alloyed powder is adjusted to 7:3. The raw materials used are: 140 g beryllium ingot and 60 g aluminum ingot. The beryllium ingot was purchased from Shanghai Taiyang Technology Co., Ltd., and the aluminum ingot was purchased from Anhui Kaifei New Material Technology Co., Ltd.

[0036] The preparation method steps are as follows:

[0037] Step 1: Dry the beryllium ingot and aluminum ingot samples at 250 °C, with a weight ratio of 7:3.

[0038] Step 2: Place the beryllium ingot and aluminum ingot into two separate crucibles. In a vacuum chamber, heat the crucible containing the beryllium ingot to 850°C for 2.5 hours, then raise the temperature to 1550°C and hold for 1.5 hours until it becomes molten. In a vacuum chamber, heat the crucible containing the aluminum ingot to 450°C for 2 hours, then raise the temperature to 750°C and hold for 1.5 hours until it becomes molten. Wrap the aluminum ingot in aluminum foil and place it into the crucible.

[0039] Step 3: After mixing the beryllium melt and the aluminum melt, place them in the crucible above the atomizing nozzle, keep them at 1550 ℃ and stir for 45 min.

[0040] Step 4: The mixed melt is injected through a rotating nozzle into an atomization chamber where it is blown and cooled by strong argon gas. It falls freely through a rapid solidification chamber about 3 m long and shrinks into a spherical shape under the action of surface tension and rapid cooling solidification.

[0041] Step 5: The beryllium-aluminum pre-alloyed powder obtained in the powder collector is loaded into a 20 mm diameter mold (pre-laid with carbon paper). The mold is then placed in a manual hydraulic press and pre-pressed at 10 MPa for 2 minutes. The pre-pressed mold is then loaded into a spark plasma sintering furnace and evacuated to a vacuum of 1.0 × 10⁻⁶. -2 Pa, the sintering temperature is set to 600 ℃, the heating rate is 50 ℃ / min, the sintering pressure is 50 MPa, and the holding time is 5 min.

[0042] Step 6: After the mold has cooled, demold and remove the carbon paper coating from the surface of the beryllium aluminum alloy sample.

[0043] Example 3

[0044] This embodiment compares the properties of beryllium-aluminum pre-alloyed powders with different beryllium-aluminum composition ratios and their samples. The preparation steps in this embodiment are the same as in Example 1, except that the amount of raw materials added is adjusted to achieve a beryllium to aluminum ratio of 8:2 in the prepared spherical beryllium-aluminum pre-alloyed powder. The raw materials used are: 160 g of beryllium ingot and 40 g of aluminum ingot. The beryllium ingot was purchased from Shanghai Taiyang Technology Co., Ltd., and the aluminum ingot was purchased from Anhui Kaifei New Material Technology Co., Ltd.

[0045] The preparation method steps are as follows:

[0046] Step 1: Dry the beryllium ingot and aluminum ingot samples at 250 ℃, with a weight ratio of 8:2.

[0047] Step 2: Place the beryllium ingot and aluminum ingot into two separate crucibles. In a vacuum chamber, heat the crucible containing the beryllium ingot to 850°C for 2.5 hours, then raise the temperature to 1550°C and hold for 1.5 hours until it becomes molten. In a vacuum chamber, heat the crucible containing the aluminum ingot to 450°C for 2 hours, then raise the temperature to 750°C and hold for 1.5 hours until it becomes molten. Wrap the aluminum ingot in aluminum foil and place it into the crucible.

[0048] Step 3: After mixing the beryllium melt and the aluminum melt, place them in the crucible above the atomizing nozzle, keep them at 1550 ℃ and stir for 45 min.

[0049] Step 4: The mixed melt is injected through a rotating nozzle into an atomization chamber where it is blown and cooled by strong argon gas. It falls freely through a rapid solidification chamber about 3 m long and shrinks into a spherical shape under the action of surface tension and rapid cooling solidification.

[0050] Step 5: The beryllium-aluminum pre-alloyed powder obtained in the powder collector is loaded into a 20 mm diameter mold (pre-laid with carbon paper). The mold is then placed in a manual hydraulic press and pre-pressed at 10 MPa for 2 minutes. The pre-pressed mold is then loaded into a spark plasma sintering furnace and evacuated to a vacuum of 1.0 × 10⁻⁶. -2 Pa, the sintering temperature is set to 600 ℃, the heating rate is 50 ℃ / min, the sintering pressure is 50 MPa, and the holding time is 5 min.

[0051] Step 6: After the mold has cooled, demold and remove the carbon paper coating from the surface of the beryllium aluminum alloy sample.

[0052] Example 4

[0053] This experiment serves as a comparative example, comparing beryllium-aluminum alloy powder prepared by the traditional mechanical alloying method with beryllium powder particles obtained by impact powdering and spherical high-purity aluminum powder. Finally, beryllium-aluminum alloy was prepared by spark plasma sintering.

[0054] The preparation method steps are as follows:

[0055] Step 1: Weigh out 60 g of beryllium powder and 40 g of aluminum powder in the glove box.

[0056] Step 2: According to the specified proportions, load the beryllium powder, aluminum powder, and an appropriate amount of tungsten balls weighed in Step 1 into an aluminum alloy ball mill jar. Purge the ball mill jar with argon in a glove box. Seal the argon-purified ball mill jar and perform ball milling within the argon-protected glove box. The ball-to-powder ratio is selected as 6:1, the ball milling speed is 200 r / min, and the ball milling time is 6 h. To avoid excessive temperature rise during ball milling, interrupt the program for 10 min every 30 min of ball milling. Vacuum-store the milled powder to obtain beryllium-aluminum powder with a beryllium content of 60 wt%.

[0057] Step 3: Calculate the amount of powder to be used according to the dimensions of the mold design. Put the beryllium aluminum powder obtained in Step 2 into a mold with a diameter of 20 mm. Then place the mold in a manual hydraulic press and pre-press the powder under a pressure of 10 MPa for 2 minutes to ensure that the powder is filled evenly and to prevent the powder from leaking out. This will reduce the initial pressure load on the mold and protect the mold and equipment.

[0058] Step 4: Load the pre-pressed mold into the spark plasma sintering furnace and evacuate to a vacuum level of 1.0 × 10⁻⁶. -2 The sintering temperature was set at 600 ℃, the heating rate was 50 ℃ / min, the sintering pressure was applied at a rate of 5 MPa / min up to 50 MPa, and the holding time was 5 min. After sintering, the sample was cooled to room temperature and depressurized in the furnace to finally obtain beryllium aluminum alloy.

[0059] Table 1 Comparison of mechanical properties of beryllium aluminum alloys prepared in Examples 1-4

[0060] Material Elastic modulus (GPa) Tensile strength (MPa) Elongation (%) Example 1 76.05±0.20 264.52 3.9 Example 2 63.85±0.17 285.79 3.4 Example 3 90.14±0.31 295.22 2.8 Example 4 38.16±0.15 208.95 3.1

[0061] As can be seen from Table 1, the mechanical properties of the samples (Examples 1, 2, and 3) prepared by the spherical beryllium-aluminum pre-alloyed powder prepared by the dual-melt mixing combined with rapid solidification atomization method are superior to those of the samples prepared by the mechanical alloying method. Compared with samples with different beryllium-aluminum composition ratios, the beryllium-aluminum alloy materials prepared by the dual-melt mixing combined with rapid solidification atomization method show a significant improvement in tensile strength and yield strength, as well as a certain improvement in elongation.

[0062] from Figure 2 As can be seen from (ac), the prepared spherical beryllium-aluminum pre-alloyed powder has good sphericity, with most spherical powder surfaces exhibiting a three-dimensional network structure of alternating beryllium and aluminum phases, and a small portion of small particles adsorbing onto larger particles to form satellite-like structures. However, from... Figure 2As can be seen from (de), some powder particles have a relatively large surface roughness and an uneven structure. Meanwhile, through... Figure 2 (f) shows that the submicron-sized beryllium grains are uniformly distributed.

[0063] from Figure 3 As can be seen, the bright white aluminum phase and the dark black beryllium phase interweave in a network structure, presenting a patterned and radial morphology. During the sintering process, the aluminum phase flows and fills the gaps between the particles, resulting in the phenomenon of local aluminum phase aggregation.

Claims

1. A method for preparing beryllium aluminum alloy based on dual-melt mixed atomization, characterized in that, First, a vacuum melting process is used to melt beryllium ingots and aluminum ingots separately and then mix them. The mixed melt is added to a crucible above the nozzle of the atomizing chamber and stirred and melted. Under the action of the nozzle and centrifugal force, the melt falls freely through the rapid solidification chamber and into the powder collector to prepare beryllium-aluminum pre-alloy powder. Subsequently, beryllium-aluminum alloy is prepared by spark plasma sintering.

2. The method for preparing beryllium aluminum alloy based on dual-melt mixed atomization as described in claim 1, characterized in that, The steps are as follows: Step 1: Dry the beryllium ingot and aluminum ingot samples; Step 2: Place the beryllium ingot and aluminum ingot into two separate crucibles. In a vacuum chamber, heat the crucible containing the beryllium ingot to 800-900℃ for 2-3 hours, then raise the temperature to 1500-1600℃ and hold for 1-2 hours to molten the ingot. In the same vacuum chamber, heat the crucible containing the aluminum ingot to 400-500℃ for 2-3 hours, then raise the temperature to 700-800℃ and hold for 1-2 hours to molten the ingot. Step 3: After mixing the beryllium melt and aluminum melt, place them in the crucible above the atomizing nozzle, keep them warm and stir; Step 4: The mixed melt is injected through a rotating nozzle into an atomization chamber where it is blown and cooled by strong argon gas. It falls freely through a rapid solidification chamber and shrinks into a spherical shape under the action of surface tension and rapid cooling and solidification. Step 5: Load the beryllium-aluminum pre-alloyed powder obtained in the powder collector into a mold, then place the mold in a manual hydraulic press and pre-press the powder under a pressure of 10 MPa for 1-2 minutes. Place the pre-pressed mold into the discharge plasma furnace and evacuate to a vacuum of 1.0 × 10⁻⁶. -2 Pa, set the sintering temperature to 550~625 ℃, the heating rate to 50 ℃ / min, the sintering pressure to 50 MPa, and the holding time to 5 min.

3. The method for preparing beryllium aluminum alloy based on dual-melt mixed atomization as described in claim 2, characterized in that, The drying temperature in step 1 is 250℃.

4. The method for preparing beryllium aluminum alloy based on dual-melt mixed atomization as described in claim 2, characterized in that, In step 1, the weight ratio of beryllium ingot to aluminum ingot is 6~8:2~4.

5. The method for preparing beryllium aluminum alloy based on dual-melt mixed atomization as described in claim 2, characterized in that, In step 2, the aluminum ingot is wrapped in aluminum foil and then placed in a crucible for melting.

6. The method for preparing beryllium aluminum alloy based on dual-melt mixed atomization as described in claim 2, characterized in that, In step 3, keep the temperature at 1500~1600 ℃ and stir for 30~60 min.

7. The beryllium aluminum alloy prepared by the method according to any one of claims 1 to 6.

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