A method for recycling machining chips of a particle-reinforced aluminum matrix composite material

Abstract

The present application belongs to the field of recycling of aluminum matrix composite material, and particularly relates to a recycling method of aluminum matrix composite material machining chips, which comprises the following steps: removing oil stains and floating dust on the surface of the machining chips and crushing the machining chips into flaky materials; cleaning the flaky materials by alkali washing and acid washing to remove the oxide layer; determining the mass fraction of the reinforcing phase through the acid washing; performing gravity sedimentation after stirring the flaky materials to obtain particles arranged in parallel; obtaining a blank ingot through low-temperature vacuum sintering; and preparing aluminum matrix composite material with high interfacial bonding strength and good uniformity through high-temperature plastic deformation. The recycling of the particle reinforced aluminum matrix composite material machining chips reduces the machining loss. The removal of the oxide layer reduces the sintering difficulty of the particles. The parallel arrangement of the machining chips solves the problem of non-densification and easy porosity of the flaky aluminum matrix composite material particles due to high strength, and provides a new scheme for recycling of the composite material.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of recycling of aluminum matrix composites, and particularly relates to a method for recycling machining chips of particle-reinforced aluminum matrix composites. BACKGROUND

[0002] Particle-reinforced aluminum matrix composites have good properties such as light weight, high specific strength, high specific modulus, high thermal conductivity, low linear expansion coefficient, and wear resistance, and are increasingly widely used in aerospace, aviation, weapon equipment, electronic packaging, and 3C products, and help the successful implementation of major engineering tasks of many countries. With the large-scale application of particle-reinforced aluminum matrix composites, the technical demand for recycling and reuse is increasingly urgent. Particle-reinforced aluminum matrix composites are high in strength and difficult to deform plastically, and thus are mainly shaped by mechanical machining, resulting in a large amount of machining chips in the process of chip removal. The machining chips still contain a large amount of reinforcing phase particles, and thus are difficult to recycle by traditional aluminum alloy recycling processes. In addition, the strength of the machining chips is much higher than that of aluminum alloys, and when the machining chips are cold-pressed, the machining chips with different orientations are difficult to deform due to their high strength, and thus pores and micro-cracks are easily formed, resulting in a low product yield.

[0003] The prior art with the patent number 202310556719.2 “A method for recycling waste of particle-reinforced aluminum matrix composites” performs solid solution on the powder, and the surface of the waste is easy to react with the quenching medium (usually water), and the quenching medium often contains a high content of impurities, which are difficult to remove by subsequent cleaning with alcohol, and finally the impurities are introduced into the composite billet, which seriously reduces the reliability of the composite material and produces more waste. The prior art with the patent number 202311260213.3 “Powder recycling method of aluminum matrix composites” obtains composite particles with an average particle size of 0.1 cm-3.0 cm, and the particle size span is extremely large, which is easy to cause uneven distribution of large and small particles in the subsequent preparation process, resulting in differences in material performance and limiting the application.

[0004] In summary, it is necessary to provide a method for recycling machining chips of particle-reinforced aluminum matrix composites, which further improves the purity and particle size controllability of the raw material powder on the basis of the existing recycling process. SUMMARY

[0005] In view of the deficiencies of the above process, in order to effectively utilize the waste generated in the mechanical machining process of aluminum matrix composites, the present application provides a method for recycling machining chips of particle-reinforced aluminum matrix composites, and the specific steps are as follows:

[0006] Step (1), crushing the machining chips of particle-reinforced aluminum matrix composites to obtain flaky composite particles;

[0007] Step (2), the flaky composite particles are sequentially subjected to alkali washing and acid washing to remove surface oxides, and a clean surface is obtained.

[0008] Step (3), the flaky composite particles are subjected to acid washing and drying, and the mass fraction of the reinforcing phase is calculated.

[0009] Step (4), the flaky composite particles are loaded into an organic solution and stirred, and parallelly arranged composite particles are obtained through centrifugation and gravity sedimentation.

[0010] Step (5), the flaky composite particles are subjected to low-temperature vacuum hot-pressing sintering to obtain a composite billet.

[0011] Step (6), the composite billet is subjected to plastic deformation along the height and diameter directions to improve the interface bonding strength and uniformity, and a final composite material is obtained.

[0012] In order to better achieve the technical effect, the method is further improved as follows:

[0013] In step (1), the reinforcing phase of the particle reinforced aluminum matrix composite machining chips is SiC, B4C or Si particles, and the reinforcing phase content is less than or equal to 30%; the machining chips are one or more of strip chips, C-shaped chips, broken chips, spiral chips and watch spring-shaped chips.

[0014] In step (1), the diameter of the broken flaky composite particles is 5-15 mm.

[0015] Step (2) is specifically that the flaky composite particles are placed in a 20-100 g / L sodium hydroxide solution, and after alkali etching for 20-60 min, they are placed in a 50-150 g / L nitric acid solution for cleaning, and are taken out after the surface oxides of the flaky composite particles are removed.

[0016] Step (3) is specifically that the particles are sieved according to particle size, and in order to reduce calculation error, at least 1 portion of 0.5-1.0 g is weighed from the upper, middle and lower parts of the flaky composite particles, the mass fraction of the reinforcing phase is calculated respectively, the composition of the original machining chips is determined by determining the mass fraction of the reinforcing phase, which is convenient for subsequent use and classification. 10% nitric acid solution is added to the flaky composite particles, heated to complete dissolution, heated again to ensure complete dissolution of Al, and then centrifuged with deionized water for 4-5 times, each time for 10-30 min, at a speed of 2000±500 rpm, and finally dried.

[0017] The step (4) is specifically as follows: the flaky composite material particles after pickling are put into a container containing an organic solution and stirred, and after centrifugation and gravity sedimentation, the excess organic solution is removed by using a pipette or a rubber head dropper, and then the container is dried at 40-80 ℃ for 4-20 h to obtain the parallelly arranged composite material powder; the excess part of the container not carrying the flaky composite material particles is cut off, the upper opening of the container is sealed, and 2-5 small holes with a diameter of 1-3 mm are formed on the upper end face of the container.

[0018] In the step (4), the container is a barrel-shaped container made of 1 series or 6 series aluminum alloy, the wall thickness and the lower bottom thickness of the container are 5-10 mm, the outer diameter is 1-3 mm 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 an aluminum alloy plate with a thickness of 5-10 mm.

[0019] In the step (4), the organic solvent is alcohol or acetone, and alcohol is preferred. The addition amount is 2-4 times the volume of the flaky composite material particles, and the stirring time is 1-5 h.

[0020] The step (5) is specifically as follows: the container is placed in a steel mold for vacuum sintering, the sintering temperature is 400-520 ℃, the holding time is 2-10 h, and the hot pressing pressure is 200-300 MPa, so that the density of the composite material ingot reaches 100%.

[0021] The step (6) is specifically as follows: the composite material ingot together with the container is forged along the height direction and rolled along the diameter direction of the ingot, wherein the forging and rolling temperatures are 530-580 ℃. The plastic deformation sequence is as follows: the composite material ingot together with the container is forged to a height of 30-80 mm, then rolled along the diameter direction, and rolled to a thickness of 5-50 mm to obtain the final particle reinforced aluminum matrix composite material.

[0022] The beneficial effects of the present application are as follows:

[0023] In the present application, different types of machining chips of aluminum matrix composite material generated by machining are crushed, and the surface oxide layer is removed by pickling and alkali washing, and the flaky composite material is arranged in layers, which can increase the density of subsequent low-temperature hot pressing. In addition, the composite material is plastically deformed at high temperature by forging and rolling, which further eliminates the discontinuity of the boundary of the flaky composite material and improves the uniformity and strength of the material, thereby laying a good foundation for the reliability of the subsequent secondary use of the material.

[0024] Reference signs

[0025] Figure 1 : metallographic phase diagram of the particle reinforced aluminum matrix composite material obtained in Example 1 by using the method;

[0026] Figure 2Microstructure of the particulate reinforced aluminum matrix composite obtained in Example 1 without using the method. DETAILED DESCRIPTION

[0027] Example 1

[0028] Step (1): The ribbon chips generated during the machining of a part with a composition of 15 vol.% SiC / 2009 Al were crushed and sieved to obtain machining chips with a size of about 15 mm, which were placed in an alcohol solvent and ultrasonically cleaned for 30 min to remove surface oil and dust.

[0029] Step (2): The cleaned machining chips 2 kg were first washed with 100 g / L sodium hydroxide solution for 20 min, and then the surface water spots of the machining chips were blown dry after being taken out. Then the machining chips were cleaned in 50 g / L nitric acid solution, and after the surface grayness disappeared, the sheet-shaped machining chips were taken out and dried.

[0030] Step (3): One portion of powder was taken from each of the top, middle and bottom of the sheet-shaped powder after acid and alkali washing, each portion weighing about 0.5 g, and an electronic balance with a precision of 0.1 mg was used for weighing. Then the weighed powder was placed in 10% nitric acid solution and heated to completely dissolve, and repeated 2 times. Then it was centrifuged 4 times with deionized water, the centrifugation time was 20 min, and the speed was 2000 r / min. After testing with aluminum reagent, aluminum ions were found, and after repeating the centrifugation 4 times, no aluminum ions were detected. The average mass fraction of SiC was calculated to be 16.54%.

[0031] Step (6): A steel mold with an inner diameter of 160 mm and a height of 150 mm was selected as the hot pressing mold. The above particles were loaded into a 1060 Al-made jacket, the lower bottom and wall thickness of the jacket were 5 mm, the outer diameter was 158 mm, and the height was 230 mm. 2 Kg of powder was loaded into the aluminum jacket, and an alcohol solution with a volume of 2 times the aluminum chip was added, stirred for 1 h, and then centrifuged and settled.

[0032] Step (7): After the settlement was completed, the excess alcohol was sucked off, and the sheet-shaped aluminum chips were dried. Then a 5 mm thick circular aluminum sheet was selected to seal the opening of the aluminum jacket by welding, and after sealing, 5 small holes with a diameter of 1 mm were opened on the upper end surface of the jacket. After cutting off the excess part of the jacket height, it was loaded into the steel mold.

[0033] Step (8): The steel mold was vacuum sintered at a sintering temperature of 400°C for 2 h, and the hot pressing pressure was 200 MPa. After hot pressing was completed, the billet with aluminum jacket was taken out.

[0034] Step (9): the billet with a height of about 40 mm is forged at 530℃, and the single pass deformation is 5%. After being forged to 30 mm, the material is rolled along the diameter direction, and the single pass deformation is not more than 8%. After being rolled to 5 mm, the surface aluminum alloy sheath is milled away by a gantry mill to obtain the final composite material.

[0035] As shown in Figs. 1 and 2, the metallographic structures of Example 1 and Example 1 without parallel arrangement of machining chips are respectively shown. Figure 1 and Figure 2 As shown in Figs. 1 and 2, the metallographic structures of Example 1 and Example 1 without parallel arrangement of machining chips are respectively shown. Figure 2 A large area of white aluminum alloy region appears in Fig. 2, and it can be found that the composition inhomogeneity in the metallographic structure without parallel arrangement is more obvious, which leads to abnormal properties of material mechanics, density, elastic modulus and thermal expansion, and causes great safety hazards to the subsequent use of the material.

[0036] Example 2:

[0037] Step (1): the spring-shaped chips generated in the machining process of the billet with a composition of 27% Si / Al are crushed and sieved to obtain machining chips with a size of about 8 mm. The machining chips are placed in an alcohol solvent and ultrasonically cleaned for 30 min to remove surface oil stains and dust.

[0038] Step (2): the cleaned machining chips 6 kg are first washed with 80 g / L sodium hydroxide solution for 30 min. After being taken out, the surface water stains of the machining chips are blown dry. Then, the machining chips are washed in 100 g / L nitric acid solution. After observing that the surface ash disappears, the sheet-shaped machining chips are taken out and dried.

[0039] Step (3): 1 portion of powder is taken from each of the upper, middle and lower parts of the sheet-shaped particles after acid and alkali washing, and each portion of powder weighs about 1.0 g. An electronic balance with a precision of 0.1 mg is used to weigh the powder. Then, the weighed powder is placed into 10% nitric acid solution and heated to completely dissolve. The process is repeated twice. Then, the powder is centrifuged with deionized water for 5 times, and the centrifugation time is 10 min and the rotation speed is 2500 r / min. After being tested by aluminum reagent, it is found that there are aluminum ions. After being centrifuged for 3 more times, no aluminum ions are detected. It is calculated that the average mass fraction of Si is 26.36%.

[0040] Step (6): a steel mold with an inner diameter of 210 mm and a height of 200 mm is selected as a hot pressing mold. The powder is loaded into an aluminum sheath with a lower bottom and a wall thickness of 10 mm, an outer diameter of 206 mm and a height of 600 mm. 6 kg of powder is loaded into the aluminum sheath, and an alcohol solution with a volume of 3 times that of the sheet-shaped aluminum chips is added. After stirring for 3 h, the powder is centrifuged and settled.

[0041] Step (7): After the end of the sedimentation, the excess alcohol is sucked off, and the sheet-shaped aluminum chips are dried. Then, a 10 mm thick circular aluminum sheet is selected to seal the opening of the aluminum sheath by welding. After sealing, two 3 mm small holes are opened on the upper end face of the sheath. After cutting off the excess part of the sheath height, it is loaded into a steel mold.

[0042] Step (8): The steel mold is vacuum sintered at a sintering temperature of 450°C for 4h, and the hot pressing pressure is 250MPa. After hot pressing, the billet with the aluminum sheath is taken out.

[0043] Step (9): The billet with a height of about 100mm is forged at 560°C, and the single pass deformation is 5%. After forging to 50mm, rolling is performed in the diameter direction, and the single pass deformation is not more than 8%. After rolling to 30mm, the surface aluminum alloy sheath is milled off with a gantry mill to obtain the final composite material.

[0044] As shown in Table 1, the performance comparison of the composite materials of Example 2 and Example 2 without forging and rolling can be found that the mechanical properties of the material can be significantly improved after forging and rolling.

[0045] Table 1 Performance comparison of 27%Si / Al under different conditions in Example 2

[0046]

[0047] Example 3:

[0048] Step (1): The screw chips generated during the processing of the billet with a composition of 30%B4C / 6061Al are crushed and sieved to obtain processing chips with a size of about 6mm. The processing chips are placed in an alcohol solvent and ultrasonically cleaned for 30min to remove surface oil and dust.

[0049] Step (2): The cleaned processing chips 4kg are first etched with 20g / L sodium hydroxide solution for 60min. After blowing dry the water spots on the surface of the processing chips, they are then washed in a 150g / L nitric acid solution. After observing that the surface grayness disappears, the sheet-shaped processing chips are taken out and dried.

[0050] Step (3): From the sheet-shaped powder after acid and alkali washing, 1 portion of powder is taken from each of the upper, middle and lower parts, with each portion weighing about 1.0g. The weighed powder is then placed in a 10% nitric acid solution and heated to completely dissolve, and the process is repeated twice. Then, the powder is centrifuged 5 times with deionized water, with a centrifugation time of 30min and a rotation speed of 1500r / min. After testing with aluminum reagent, aluminum ions are found. After continuing to centrifuge for 2 more times, no aluminum ions are detected. The average mass fraction of boron carbide is calculated to be 29.37%.

[0051] Step (6): A steel mold with an inner diameter of 160 mm and a height of 300 mm is selected as a hot-pressing mold. The powder is loaded into an aluminum jacket made of 6061 Al, the lower bottom and wall thickness of the jacket are 5 mm, the outer diameter is 154 mm, and the height is 800 mm. 4 Kg of powder is loaded into the aluminum jacket, and an alcohol solution with a volume of 4 times that of the aluminum flake is added. After stirring for 3 h, centrifugation and sedimentation are performed.

[0052] Step (7): After the sedimentation is completed, the excess alcohol is removed, and the aluminum flake is dried. Then, a 5 mm thick circular aluminum sheet is selected to seal the opening of the aluminum jacket by welding. After sealing, two 2 mm small holes are opened on the upper end surface of the jacket, and the excess part of the jacket is cut off and loaded into the steel mold.

[0053] Step (8): The steel mold is vacuum sintered at a sintering temperature of 520°C for 10 h, and hot-pressing pressure is 300 MPa. After hot-pressing is completed, the billet with the aluminum jacket is taken out.

[0054] Step (9): The billet with a height of about 100 mm is forged at 580°C, and the single pass deformation is 5%. After forging to 80 mm, rolling is performed in the diameter direction, and the single pass deformation is not greater than 5%. After rolling to 50 mm, the surface aluminum alloy jacket is milled off by a gantry mill to obtain the final composite material.

[0055] As shown in Table 2, the performance comparison of the composite materials of Example 3 and Example 3 without acid washing and alkali washing can be found that the mechanical properties of the material can be significantly improved after acid washing and alkali washing.

[0056] Table 2 Performance comparison of 31% B4C / 6061 under different conditions in Example 3

[0057]

[0058] The above examples are only for illustrating the technical concept and characteristics of the present application, and the purpose is to enable those skilled in the art to understand the content of the present application and to implement it, and it cannot limit the protection scope of the present application. Any equivalent changes or modifications made according to the spirit and essence of the present application should be covered within the protection scope of the present application.

[0059] The above examples only express several embodiments of the present application, and the description is more specific and detailed, but it cannot be understood as limiting the scope of the present application. It should be pointed out that for ordinary skilled persons in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are within the protection scope of the present application.

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): The sheet-like composite material particles obtained in step 2 are acid-washed, dried, and the mass fraction of the reinforcing phase is calculated. Step (4): The sheet-like composite material particles obtained in step 2 are loaded into an aluminum casing, and an organic solution is added and stirred. After centrifugation and gravity sedimentation, parallel sheet-like composite material particles are obtained. Step (5): The aluminum package containing parallel-arranged sheet-like composite material particles is inserted into a steel mold, and the steel mold is vacuum sintered to obtain a composite material billet. Step (6): Plastic deformation is performed on the composite material billet along the height and diameter directions to improve the interfacial bonding strength and uniformity, and the final composite material is obtained. Step (6) specifically involves forging the composite material billet along the axial direction and rolling it along the diameter direction of the billet, with the forging and rolling temperature being 530-580℃. The plastic deformation sequence is to forge the composite material billet along the sleeve to a height of 30-80mm and then roll it along the diameter direction to a thickness of 5-50mm. Finally, the outer sleeve is removed to obtain the final particle-reinforced aluminum matrix 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) specifically involves loading the sheet-like composite material particles obtained in step (2) into an aluminum sleeve containing an 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 sleeve that does not support the sheet-like composite material particles is cut off, the top of the sleeve is sealed, and 2-5 small holes with a diameter of 1-3 mm are opened on the upper end face of the sleeve.

7. The method for recycling processing debris from particle-reinforced aluminum matrix composites according to claim 1, characterized in that: In step (4), the casing is made of 1-series or 6-series aluminum alloy in a barrel shape. 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 package 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.

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