Method for recovering processing scraps of particle reinforced aluminum matrix composite

Abstract

The invention belongs to the field of aluminum-based composite material recycling, and particularly relates to an aluminum-based composite material machining chip recycling method which comprises the steps that oil stains and floating dust on the surfaces of machining chips are removed, and the machining chips are crushed into sheets; carrying out alkali washing and acid washing cleaning to remove an oxide layer; determining a reinforced phase mass fraction through pickling; stirring the flaky material, and performing gravity settling to obtain particles arranged in parallel; performing low-temperature vacuum sintering to obtain a billet; and the aluminum-based composite material with high interface bonding strength and good uniformity is prepared through high-temperature plastic deformation. And the particle reinforced aluminum matrix composite material processing chips are recycled, so that the machining loss is reduced. And the oxide layer is removed, and the particle sintering difficulty is reduced. And the processing chips are arranged in parallel, so that the problems that the sheet-shaped aluminum-based composite material particles are not dense in hot pressing and easy to generate pores due to high strength are solved, and a new scheme is provided for recycling and reusing the composite material.

Description

Technical Field

[0001] This invention belongs to the field of aluminum-based composite material recycling, specifically relating to a method for recycling processing debris from particle-reinforced aluminum-based composite materials. Background Technology

[0002] Particle-reinforced aluminum matrix composites possess excellent properties such as lightweight, high specific strength, high specific modulus, high thermal conductivity, low coefficient of linear expansion, and wear resistance. Their use in aerospace, aviation, weaponry, electronic packaging, and 3C products is becoming increasingly widespread, contributing to the successful implementation of numerous major national engineering projects. With the large-scale application of particle-reinforced aluminum matrix composites, the need for recycling and reuse technologies is becoming increasingly urgent. Particle-reinforced aluminum matrix composites themselves have high strength but are difficult to plastically deform, therefore, machining is still the primary method for achieving shapes, resulting in a large amount of machining chips during the cutting process. These chips contain a large number of reinforcing phase particles, making them difficult to recover using traditional aluminum alloy recycling processes. Furthermore, the strength of composite machining chips is much higher than that of aluminum alloys. When cold-pressing these chips, the high strength of chips with different orientations makes deformation difficult, easily leading to porosity and microcracks, resulting in low product yield.

[0003] The prior art, "A method for reusing waste of particle-reinforced aluminum matrix composites," with patent number 202310556719.2, involves solid solution treatment of powder. During this process, the waste surface readily reacts with the quenching medium (usually water), which often contains high levels of impurities. These impurities are difficult to remove through subsequent cleaning with alcohol or similar methods, ultimately introducing them into the composite ingot, severely reducing the reliability of the composite material and generating more waste. The current technology, "A method for the powder-based recycling of aluminum matrix composites," with patent number 202311260213.3, yields composite material particles with an average particle size of 0.1 cm to 3.0 cm. This wide particle size range easily leads to uneven particle distribution during subsequent preparation, causing variations in material properties and limiting applications.

[0004] In summary, it is necessary to provide a method for recycling processing debris from particle-reinforced aluminum matrix composites, which can further improve the purity and particle size controllability of raw material powder based on existing recycling processes. Summary of the Invention

[0005] In view of the shortcomings of the above-mentioned processes, in order to further and effectively utilize the waste generated during the machining of aluminum matrix composites, this invention provides a method for recycling machining chips of particle-reinforced aluminum matrix composites, the specific steps of which are as follows: Step (1): Crush the granular reinforced aluminum matrix composite material processing chips to obtain sheet-like composite material particles; Step (2): The sheet-like composite material particles are subjected to alkali washing and acid washing in sequence to remove surface oxides and obtain a clean surface; Step (3): Pickle and dry the sheet-like composite material particles, and calculate the mass fraction of the reinforcing phase; Step (4): The sheet-like composite material particles are loaded into an organic solution and stirred. After centrifugation and gravity sedimentation, parallel-arranged composite material particles are obtained. Step (5): The sheet-like composite material particles are subjected to low-temperature vacuum hot pressing sintering to obtain a composite material billet; Step (6): Plastically deform the composite material billet along the height and diameter directions to improve the interfacial bonding strength and uniformity, and obtain the final composite material.

[0006] To achieve better technical results, this method can be further improved as follows: In step (1), the reinforcing phase of the particle-reinforced aluminum matrix composite processing chips is SiC, B4C or Si particles, and the content of the reinforcing phase is less than or equal to 30%; the processing chips are one or more of the following: ribbon chips, C-shaped chips, fragmented chips, spiral chips and hairpin-shaped chips.

[0007] In step (1), the diameter of the crushed sheet-like composite material particles is 5-15 mm.

[0008] Step (2) involves placing the sheet-like composite material particles in a 20-100 g / L sodium hydroxide solution, etching them with alkali for 20-60 minutes, then rinsing them in a 50-150 g / L nitric acid solution, and removing them after the oxides on the surface of the sheet-like composite material particles have been removed.

[0009] Step (3) specifically involves sieving the particles using a sieve according to their size. To reduce calculation errors, at least one portion (0.5-1.0g) is weighed from the upper, middle, and lower parts of the sheet-like composite material particles, and the mass fraction of the reinforcing phase is calculated for each portion. Determining the mass fraction of the reinforcing phase confirms the composition of the original processing chips, facilitating subsequent use and classification. A 10% nitric acid solution is added to the sheet-like composite material particles and heated until completely dissolved. The mixture is then heated again to ensure complete Al dissolution. The particles are then centrifuged 4-5 times with deionized water, each centrifugation lasting 10-30 minutes at a speed of 2000±500 rpm. Finally, the particles are dried.

[0010] Step (4) involves placing the acid-washed flake composite material particles into a container filled with organic solution and stirring. After centrifugation and gravity sedimentation, excess organic solution is removed using a pipette or dropper. The mixture is then dried at 40-80℃ for 4-20 hours to obtain parallel-arranged composite material powder. The excess portion of the container that does not support the flake composite material particles is removed, the container is sealed, and 2-5 small holes with a diameter of 1-3 mm are opened on the upper surface of the container.

[0011] In step (4), the container is a barrel-shaped container made of 1-series or 6-series aluminum alloy. The container wall thickness and bottom thickness are 5-10mm, the outer diameter is 1-3mm smaller than the inner diameter of the composite material steel mold, and the height is 1.5-3 times the height of the composite material mold. The upper opening of the container is sealed by welding with an aluminum alloy plate with a thickness of 5-10mm.

[0012] In step (4), the organic solvent is alcohol or acetone, with alcohol being preferred. The amount added is 2-4 times the volume of the sheet-like composite material particles, and the stirring time is 1-5 hours.

[0013] Step (5) specifically involves placing the container in a steel mold for vacuum sintering at a temperature of 400-520℃, a holding time of 2-10h, and a hot pressing pressure of 200-300MPa to obtain a composite material billet with a density of 100%.

[0014] Step (6) specifically involves forging the composite material billet along with the container along the height direction and rolling it along the billet diameter direction, wherein the forging and rolling temperature is 530-580℃. The plastic deformation sequence is to forge the composite material billet along with the container to a height of 30-80mm, and then roll it along the diameter direction to a thickness of 5-50mm, thus obtaining the final particle-reinforced aluminum matrix composite material.

[0015] The beneficial effects of this invention are as follows: This invention involves breaking down different types of machining chips from aluminum-based composite materials generated during machining, removing the surface oxide layer through acid and alkali washing, and arranging the sheet-like composite material in a layered manner, which increases the density of subsequent low-temperature hot pressing. Furthermore, forging and rolling are used to plastically deform the composite material at high temperatures, further eliminating the discontinuities at the boundaries of the sheet-like composite material, improving the material's uniformity and strength, and laying a solid foundation for the reliability of subsequent secondary use of the material.

[0016] Figure Labels Figure 1 Metallographic image of the particle-reinforced aluminum matrix composite material obtained by this method in Example 1; Figure 2 Metallographic image of the particle-reinforced aluminum matrix composite material obtained in Example 1 without using this method. Detailed Implementation

[0017] Example 1: Step (1): The ribbon-like chips generated during the machining of the part with a composition of 15 vol.% SiC / 2009Al are crushed and sieved to obtain machining chips with a size of about 15 mm. The chips are placed in an alcohol solvent and ultrasonically cleaned for 30 minutes to remove surface oil and dust.

[0018] Step (2): First, use 100g / L sodium hydroxide solution to etch 2kg of cleaned machining chips for 20min. After taking them out, blow dry the water stains on the surface of the machining chips. Then, wash them in 50g / L nitric acid solution. After observing that the surface dust has disappeared, take out the flaky machining chips and dry them.

[0019] Step (3): Take one portion of powder from the top, middle and bottom of the acid-alkali washed flake powder, each weighing about 0.5g. Weigh the powder using an electronic balance with an accuracy of 0.1mg. Then, put the weighed powder into a 10% nitric acid solution and heat until completely dissolved. Repeat this process twice. Then, centrifuge the powder four times with deionized water for 20 minutes at a speed of 2000r / min. After testing with aluminum reagent, aluminum ions were found. After repeating the centrifugation four more times, no aluminum ions were detected. The average mass fraction of SiC was calculated to be 16.54%.

[0020] Step (6): Select a steel mold with an inner diameter of 160 mm and a height of 150 mm as a hot pressing mold. Put the above particles into a sleeve made of 1060Al. The bottom and wall thickness of the sleeve is 5 mm, the outer diameter is 158 mm, and the height is 230 mm. Put 2 kg of powder into the aluminum sleeve and add an alcohol solution with a volume of 2 times that of the flaky aluminum chips. Stir for 1 hour and then centrifuge and settle.

[0021] Step (7): After settling, remove excess alcohol and dry the flaky aluminum shavings. Then, use a 5mm thick circular aluminum sheet to weld and seal the opening of the aluminum sheath. After sealing, make 5 small holes of 1mm on the upper surface of the sheath, cut off the excess height of the sheath, and then insert it into a steel mold.

[0022] Step (8): Vacuum sinter the steel mold at a temperature of 400℃ for 2 hours and a hot pressing pressure of 200MPa. After hot pressing, remove the billet with aluminum sheath.

[0023] Step (9): Forge the billet with a height of about 40mm at 530℃ with a single-pass deformation of 5%. After forging to 30mm, roll it along the diameter direction with a single-pass deformation of no more than 8%. After rolling to 5mm, use a gantry milling machine to remove the surface aluminum alloy cladding to obtain the final composite material.

[0024] like Figure 1 and Figure 2 The figures shown are the metallographic structures of Example 1 and Example 1 in which the machining chips were not arranged in parallel, respectively. Figure 2 A large white area of ​​aluminum alloy was found in the sample, indicating significant compositional inhomogeneity in the non-parallel metallographic structure. This resulted in abnormalities in the material's mechanical, density, elastic modulus, and thermal expansion properties, posing a significant safety hazard to the subsequent use of the material.

[0025] Example 2: Step (1): The spring-shaped shavings generated during the processing of the billet with a composition of 27% Si / Al are crushed and sieved to obtain processing shavings with a size of about 8mm. They are then placed in an alcohol solvent and ultrasonically cleaned for 30 minutes to remove surface oil and dust.

[0026] Step (2): First, use 6 kg of cleaned machining chips to alkali-etch with 80 g / L sodium hydroxide solution for 30 min. After taking them out, blow dry the water stains on the surface of the machining chips. Then, wash them in 100 g / L nitric acid solution. After observing that the surface dust disappears, take out the flaky machining chips and dry them.

[0027] Step (3): Take one portion of powder from the top, middle and bottom of the acid- and alkali-washed flaky particles, each weighing about 1.0g. Weigh the powder using an electronic balance with an accuracy of 0.1mg. Then, put the weighed powder into a 10% nitric acid solution and heat it until it is completely dissolved. Repeat this process twice. Then, centrifuge it five times with deionized water for 10 minutes at a speed of 2500r / min. After testing with aluminum reagent, aluminum ions were found. After repeating the centrifugation three more times, no aluminum ions were detected. The average mass fraction of Si was calculated to be 26.36%.

[0028] Step (6): Select a steel mold with an inner diameter of 210 mm and a height of 200 mm to make a hot pressing mold. Put the above powder into a sleeve made of 1060Al. The bottom and wall thickness of the sleeve is 10 mm, the outer diameter is 206 mm, and the height is 600 mm. Put 6 kg of powder into the aluminum sleeve and add an alcohol solution with a volume of 3 times that of the flaky aluminum chips. Stir for 3 hours and then centrifuge and settle.

[0029] Step (7): After settling, remove excess alcohol and dry the flaky aluminum shavings. Then, use a 10mm thick circular aluminum sheet to weld and seal the opening of the aluminum sheath. After sealing, make two 3mm holes on the upper surface of the sheath, cut off the excess height of the sheath, and then insert it into a steel mold.

[0030] Step (8): Vacuum sinter the steel mold at a temperature of 450℃ for 4 hours and hot pressing at a pressure of 250MPa. After hot pressing, remove the billet with aluminum sheath.

[0031] Step (9): Forge a billet with a height of about 100 mm at 560°C with a single-pass deformation of 5%. After forging to 50 mm, roll it along the diameter direction with a single-pass deformation of no more than 8%. After rolling to 30 mm, use a gantry milling machine to remove the surface aluminum alloy cladding to obtain the final composite material.

[0032] Table 1 shows a comparison of the properties of the composite materials in Example 2 and those in Example 2 without forging and rolling. It can be seen that forging and rolling can significantly improve the mechanical properties of the materials.

[0033] Table 1. Performance comparison of 27% Si / Al under different conditions in Example 2 Example 3: Step (1): Crush and sieve the screw shavings generated during the processing of the billet with a composition of 30% B4C / 6061Al to obtain processing shavings with a size of about 6mm. Place them in an alcohol solvent and perform ultrasonic cleaning for 30 minutes to remove surface oil and dust.

[0034] Step (2): First, use 20g / L sodium hydroxide solution to etch 4kg of cleaned machining chips for 60min. After removing them, blow dry the water stains on the surface of the machining chips. Then, wash them in 150g / L nitric acid solution. After observing that the surface dust has disappeared, remove the flaky machining chips and dry them.

[0035] Step (3): Take one portion of powder from the top, middle and bottom of the acid-alkali washed flake powder, each weighing about 1.0g. Weigh the powder using an electronic balance with an accuracy of 0.1mg. Then, put the weighed powder into a 10% nitric acid solution and heat until completely dissolved. Repeat this process twice. Then, centrifuge the powder five times with deionized water for 30 minutes at a speed of 1500r / min. After testing with aluminum reagent, aluminum ions were found. After repeating the centrifugation twice more, no aluminum ions were detected. The average mass fraction of boron carbide was calculated to be 29.37%.

[0036] Step (6): Select a steel mold with an inner diameter of 160 mm and a height of 300 mm as a hot pressing mold. Put the above powder into a sleeve made of 6061Al. The bottom and wall thickness of the sleeve are 5 mm, the outer diameter is 154 mm, and the height is 800 mm. Put 4 kg of powder into the aluminum sleeve and add an alcohol solution with a volume of 4 times that of the flaky aluminum chips. Stir for 3 hours and then centrifuge and settle.

[0037] Step (7): After settling, remove excess alcohol and dry the flaky aluminum shavings. Then, use a 5mm thick round aluminum sheet to weld and seal the opening of the aluminum sleeve. After sealing, make two 2mm holes on the upper surface of the sleeve, cut off the excess height of the sleeve, and then insert it into a steel mold.

[0038] Step (8): Vacuum sinter the steel mold at a temperature of 520℃ for 10 hours and a hot pressing pressure of 300MPa. After hot pressing, remove the billet with aluminum sheath.

[0039] Step (9): Forge a billet with a height of about 100 mm at 580°C with a single-pass deformation of 5%. After forging to 80 mm, roll it along the diameter direction with a single-pass deformation of no more than 5%. After rolling to 50 mm, use a gantry milling machine to remove the surface aluminum alloy cladding to obtain the final composite material.

[0040] Table 2 shows a comparison of the properties of the composite materials in Example 3 and those without acid washing and alkaline washing, respectively. It can be seen that acid washing and alkaline washing can significantly improve the mechanical properties of the materials.

[0041] Table 2. Performance Comparison of 31% B4C / 6061 under Different Conditions in Example 3 The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

[0042] The above-described embodiments are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A method for recycling processing debris from particle-reinforced aluminum matrix composites, characterized in that: Includes the following steps: Step (1): Crush the granular reinforced aluminum matrix composite material processing chips to obtain sheet-like composite material particles; Step (2): The sheet-like composite material particles are subjected to alkali washing and acid washing in sequence to remove surface oxides and obtain a clean surface; Step (3): Pickle and dry the sheet-like composite material particles, and calculate the mass fraction of the reinforcing phase; Step (4): The sheet-like composite material particles are loaded into an organic solution and stirred. After centrifugation and gravity sedimentation, parallel-arranged composite material particles are obtained. Step (5): The sheet-like composite material particles are subjected to low-temperature vacuum hot pressing sintering to obtain a composite material billet; Step (6): Plastically deform the composite material billet along the height and diameter directions to improve the interfacial bonding strength and uniformity, and obtain the final composite material.

2. The method for recycling processing debris from particle-reinforced aluminum matrix composites according to claim 1, characterized in that: In step (1), the reinforcing phase of the particle-reinforced aluminum matrix composite processing chips is SiC, B4C or Si particles, and the content of the reinforcing phase is less than or equal to 30%; the processing chips are one or more of the following: ribbon chips, C-shaped chips, fragmented chips, spiral chips and hairpin-shaped chips.

3. The method for recycling processing debris from particle-reinforced aluminum matrix composites according to claim 1, characterized in that: In step (1), the diameter of the crushed sheet-like composite material particles is 5-15 mm.

4. The method for recycling processing debris from particle-reinforced aluminum matrix composites according to claim 1, characterized in that: Step (2) involves placing the sheet-like composite material particles in a 20-100 g / L sodium hydroxide solution, etching them with alkali for 20-60 minutes, then rinsing them in a 50-150 g / L nitric acid solution, and removing them after the oxides on the surface of the sheet-like composite material particles have been removed.

5. The method for recycling processing debris from particle-reinforced aluminum matrix composites according to claim 1, characterized in that: Step (3) involves adding 10% nitric acid solution to the sheet-like composite material particles, heating until completely dissolved, heating again, centrifuging with deionized water 4-5 times, each centrifugation time being 10-30 minutes and the rotation speed being 2000±500 rpm, and finally drying.

6. The method for recycling processing debris from particle-reinforced aluminum matrix composites according to claim 1, characterized in that: Step (4) involves loading the acid-washed flake composite material particles into a container filled with organic solution and stirring. After centrifugation and gravity sedimentation, the supernatant is removed, and the mixture is dried to obtain parallel-arranged composite material powder. The excess portion of the container that does not support the flake composite material particles is removed, the container is sealed, and 2-5 small holes with a diameter of 1-3 mm are opened on the upper surface of the container.

7. The method for recycling processing debris from particle-reinforced aluminum matrix composites according to claim 1, characterized in that: In step (4), the container is a barrel-shaped container made of 1-series or 6-series aluminum alloy. The container wall thickness and bottom thickness are 5-10mm, the outer diameter is 1-3mm smaller than the inner diameter of the composite material steel mold, and the height is 1.5-3 times the height of the composite material mold. The upper opening of the container is sealed by welding with an aluminum alloy plate with a thickness of 5-10mm.

8. The method for recycling processing debris from particle-reinforced aluminum matrix composites according to claim 6, characterized in that: In step (4), the organic solvent is alcohol or acetone, and the amount added is 2-4 times the volume of the sheet-like composite material particles. The stirring time is 1-5 hours.

9. The method for recycling processing debris from particle-reinforced aluminum matrix composites according to claim 1, characterized in that: Step (5) specifically involves placing the container in a steel mold for vacuum sintering at a temperature of 400-520℃, a holding time of 2-10h, and a hot pressing pressure of 200-300MPa to obtain a composite material billet with a density of 100%.

10. A method for recycling processing debris from particle-reinforced aluminum matrix composites according to claim 1, characterized in that: Step (6) specifically involves forging the composite material billet along with the container along the axial direction and rolling it along the diameter direction of the billet. The forging and rolling temperature is 530-580℃. The plastic deformation sequence is to forge the composite material billet along with the container to a height of 30-80mm and then roll it along the diameter direction to a thickness of 5-50mm. Then, the outer container is removed to obtain the final particle-reinforced aluminum matrix composite material.

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