Aluminum alloy magnetorheological fluid polishing method based on magnetic composite abrasive particles

Abstract

The application discloses an aluminum alloy magnetorheological fluid polishing method based on magnetic composite abrasive particles and relates to the technical field of aluminum alloy polishing. The aluminum alloy magnetorheological fluid polishing method based on magnetic composite abrasive particles comprises three steps of magnetic composite abrasive particle preparation, magnetorheological fluid preparation and magnetorheological polishing. The polishing pad formed by the magnetic composite abrasive particles at the grinding head part of the magnetorheological polishing machine has good adaptability, self-sharpening, guiding elasticity, flexibility and other characteristics, and can be widely applied to the finishing machining of the surfaces of complex parts such as planes, curved surfaces, inner and outer circles of bent pipes and the like. The magnetic composite abrasive particles with ferromagnetic material coated on abrasive particles form a flexible polishing pad at the magnetic grinding head, and the shearing force generated by the relative movement between the flexible polishing pad and the machined surface removes the polished material; the flexible polishing pad can also reduce the secondary damage to the surface of the aluminum alloy.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of aluminum alloy polishing, in particular to an aluminum alloy magnetorheological fluid polishing method based on magnetic composite abrasive particles. BACKGROUND

[0002] Aluminum alloy is a soft metal material, and surface damage such as scratches and pits is likely to occur on the surface of an aluminum alloy part during the forming process of the aluminum alloy part. Therefore, the surface of the part needs to be finished to obtain good surface quality. After deburring and polishing, many aluminum alloy parts also need to be subjected to surface treatment processes such as electroplating, spraying, and anodic oxidation to obtain a more smooth and beautiful surface effect. The surface of the aluminum alloy after polishing has a nanoscale ultra-high surface finish, and the light-thermal reflectivity and corrosion resistance of the surface are improved to a certain extent. Because the aluminum alloy material is soft and easily oxidized, many traditional polishing methods such as mechanical polishing, chemical polishing, and electrolytic polishing can cause secondary damage to the base material when polishing the aluminum alloy material. For example, mechanical polishing can cause surface scratches, and chemical polishing and electrolytic polishing can cause excessive corrosion. Therefore, the ultra-finish machining of the aluminum alloy material generally uses flexible polishing methods such as chemical mechanical polishing, magnetorheological fluid polishing, magnetic finishing technology, and air bag flexible polishing, which can protect the soft base material while finishing the aluminum alloy material.

[0003] Magnetorheological finishing (MRF) technology is a deterministic surface finishing technology. This method uses a flexible polishing pad formed by magnetorheological fluid under a gradient magnetic field to polish the material. The magnetorheological fluid, which is generally prepared from magnetic particles, base fluid, and surfactant, has good fluidity under the action of a magnetic field, and its viscosity changes to a Bingham fluid with plasticity in a very short time under the action of a gradient magnetic field. The flexible polishing pad formed by the magnetorheological fluid under the action of the magnetic field has high shear force and certain rigidity. The material surface layer and the polishing pad are in contact and move relative to each other and are sheared by the polishing pad to achieve polishing effect. The magnetorheological fluid polishing technology has the advantages of high machining precision, stable material removal rate, strong surface modification ability, and small subsurface damage because it uses small magnetic particles and abrasive particles and can realize the circulation of rheological form.

[0004] Abrasive particles are an important component of polishing liquid, and the abrasive particles commonly used in the process of metal chemical mechanical polishing include SiO2, CeO2 and Al2O3, etc. In actual polishing operation, it is found that, because the traditional magnetorheological fluid is a suspension formed by mixing ferromagnetic particles and abrasive particles, the phenomena of uneven distribution of abrasive particles and incomplete fixation of abrasive particles by ferromagnetic particles inevitably exist in the preparation and processing process, and uneven distribution of abrasive particles will lead to the decline of the removal capacity of the formed magnetorheological polishing pad material; and the large-diameter ferromagnetic particles in the magnetorheological polishing pad will directly contact the polished surface, thereby causing the decline of the surface quality. Therefore, the present application provides an aluminum alloy magnetorheological fluid polishing method based on magnetic composite abrasive particles to solve the above problems. SUMMARY

[0005] The present application aims to at least solve one of the technical problems existing in the prior art, and provides an aluminum alloy magnetorheological fluid polishing method based on magnetic composite abrasive particles, which can solve the problem of damage to the polished surface caused by large particles of ferromagnetic particles due to uneven distribution of abrasive particles during the rheological process of traditional magnetorheological polishing.

[0006] To achieve the above-mentioned purpose, the present application provides the following technical scheme: an aluminum alloy magnetorheological fluid polishing method based on magnetic composite abrasive particles, comprising the following steps:

[0007] S1, magnetic composite abrasive particle preparation

[0008] 1) Equipment and materials:

[0009] Materials: tetraethyl orthosilicate, 300nm Fe3O4, 28% ammonia water, deionized water, anhydrous ethanol;

[0010] Equipment: digital display powerful electric mixer, ultrasonic cleaner, constant temperature digital display water bath, electric heating air drying oven, 800 type centrifuge;

[0011] 2) 1g of Fe3O4 was weighed by using a mechanical balance and placed in 125-150ml of anhydrous ethanol, and ultrasonic dispersion was performed for 25-30 minutes; 25-30ml of deionized water and 3-5ml of ammonia water were measured and mixed and stirred, and then added to the Fe3O4 dispersion solution, and mechanical stirring was performed for 20-30min, and the PH value was measured to be above 8.5-9;

[0012] 3) 10-15ml of tetraethyl orthosilicate was added, and mechanical stirring was performed for 5-6h, and then deionized water and anhydrous ethanol were alternately washed for 3-4 times, and after centrifugation, the prepared magnetic composite abrasive particles were dried for 4h;

[0013] S2, magnetorheological fluid preparation

[0014] The magnetorheological fluid is prepared from SiO2@Fe3O4 magnetic composite abrasive particles with a volume fraction of 30-45%, additives (including PH adjuster (3-4%), complexing agent (2-3%), dispersant (3-4%), corrosion inhibitor (1-1.5%), oxidizing agent (2-3%)) with a volume fraction of 12-15%, and the rest deionized water.

[0015] S3, magnetorheological polishing

[0016] 1) Pretreatment: the 6061 aluminum alloy sample is coarsely ground for 2 minutes using 2000 and 2500 mesh SiC sandpaper, and then coarsely polished for 5 minutes using 3 micron and 1 micron particle size single crystal diamond polishing liquid, and finely polished for 7 minutes using 0.25 micron particle size single crystal diamond polishing liquid;

[0017] 2) Magnetorheological polishing: the magnetorheological fluid is used to magnetorheologically polish the 6061 aluminum alloy, the magnetorheological fluid is fed into the magnetorheological polishing equipment, the magnetic composite abrasive particles form a flexible polishing pad at the magnetic polishing head, and the processing gap is controlled to be 1.8-2.2 mm, the PH value is controlled to be 10.1-10.3, the polishing pressure is controlled to be 6800-6900 pa, the polishing speed is controlled to be 600-700 rpm, the polishing temperature is controlled to be 25-30℃, and the feed speed is 60-70 mm / min.

[0018] 3) Detection result: the surface roughness Ra of the pretreated sample is 0.137 microns, and the surface roughness Ra of the magnetorheologically polished sample is 0.002 microns.

[0019] Preferably, the experimental mechanism of the S1 step is: preparing SiO2-coated Fe3O4 magnetic composite abrasive particles, using tetraethyl orthosilicate (TEOS) as a silicon source, and the tetraethyl orthosilicate undergoes hydrolysis reaction in an alcohol-water solution, the generated silica sol uniformly coats the surface of the Fe3O4 nanoparticles through polycondensation, and the product is dried to obtain a core-shell structure magnetic composite abrasive particle with a SiO2 dry sol on the surface and Fe3O4 in the core.

[0020] The chemical equation of the S1 step reaction is as follows:

[0021] Si(OC2H5)4+4H2O→Si(OH)4+4C2H5OH

[0022] Si(OH)4→SiO2+2H2O.

[0023] Preferably, in the S2 step, the PH adjuster in the magnetorheological fluid is ammonia, the complexing agent is citric acid (H3Cit), the dispersant is polyethylene glycol (PEG20000), the corrosion inhibitor is glycine, and the oxidizing agent is hydrogen peroxide (H2O2).

[0024] Chemical assisted magnetorheological finishing (CAMRF) is a new high-precision surface treatment technology combining the characteristics of chemical mechanical polishing and magnetorheological finishing to achieve high polishing efficiency and high smoothness. The technology can change the characteristics of the magnetorheological fluid by controlling the processing parameters to realize the deterministic high-precision and high-smoothness surface finishing of the material, and no subsurface damage is generated. The special magnetorheological fluid added with certain chemical components can cause chemical reactions on the material surface to facilitate the polishing removal process and improve the material removal efficiency. The magnetorheological fluid can also adaptively adjust its viscosity and shape according to the surface topography and material properties of the workpiece, so it can adapt to different processing requirements and workpiece shapes.

[0025] The magnetic abrasive particle magnetic finishing technology is a surface finishing method in which magnetic particles and abrasive particles are arranged in a chain or columnar form in a flexible polishing pad at the magnetic abrasive head under the action of a gradient magnetic field. The magnetic composite abrasive particle is a new type of abrasive particle material formed by uniformly coating a layer of abrasive particle material on the surface of a magnetic particle by physical or chemical methods. The polishing pad formed by the magnetic composite abrasive particle can process various complex surfaces such as inner and outer circles of a rotary body, planes, curved surfaces, etc. and has good adaptability, excellent self-sharpening, good guiding elasticity and other advantages and is commonly used for polishing the surface of complex parts.

[0026] Compared with the prior art, the present application has the following advantages:

[0027] The aluminum alloy magnetorheological fluid polishing method based on the magnetic composite abrasive particle has a polishing pad formed at the magnetorheological finishing machine head part by the magnetic composite abrasive material, which has good adaptability, self-sharpening, guiding elasticity, flexibility and other characteristics, and can be widely used in the finishing machining of complex part surfaces such as planes, curved surfaces, inner and outer circles of bent pipes, etc. The application range and scene are wide. The magnetic composite abrasive particle coated with a ferromagnetic material forms a flexible polishing pad at the magnetic abrasive head, and the shearing force generated by the relative movement between the flexible polishing pad and the machined surface removes the polished material. In the polishing of the aluminum alloy surface, not only is there good adaptability to the working environment, but also the flexible polishing pad formed during the machining process can reduce the secondary damage to the aluminum alloy surface.

[0028] The aluminum alloy magnetorheological fluid polishing method based on the magnetic composite abrasive uses a flexible polishing pad formed by the magnetorheological fluid under a gradient magnetic field, and the magnetorheological fluid prepared from the magnetic particles, the base fluid and the surfactant has good fluidity under no magnetic field and changes into the Bingham fluid with plastic viscosity in a very short time under the gradient magnetic field; the flexible polishing pad formed by the magnetorheological fluid under the magnetic field has high shear force and certain rigidity, the material surface layer is in contact with the polishing pad and is removed by shearing of the polishing pad to achieve the polishing effect; the magnetorheological fluid polishing technology has the advantages of high machining precision, stable material removal rate, strong profile finishing ability and small subsurface damage because the magnetic particles and abrasives used are small and can realize the circulation in the rheological form.

[0029] The aluminum alloy magnetorheological fluid polishing method based on the magnetic composite abrasive uses the magnetic composite abrasive as the abrasive and the ferromagnetic particle to participate in the magnetorheological polishing process, so that only the abrasive contacts the polished surface in the polishing process, and the ferromagnetic particle with higher hardness does not participate in the material removal process; meanwhile, the problem of the material removal rate reduction caused by the uneven distribution of the abrasives in the traditional magnetorheological polishing process is avoided. BRIEF DESCRIPTION OF DRAWINGS

[0030] The application is further illustrated below in combination with the drawings and examples:

[0031] Figure 1 The FTIR diagram of Fe3O4 and SiO2@Fe3O4 magnetic composite abrasives;

[0032] Figure 2 The XRD diagram of Fe3O4 and SiO2@Fe3O4 magnetic composite materials;

[0033] Figure 3 The SEM diagram of Fe3O4 and SiO2@Fe3O4 magnetic composite materials;

[0034] Figure 4 The schematic diagram of the magnetorheological polishing process of the magnetic composite abrasive;

[0035] Figure 5 The schematic diagram of the traditional magnetorheological polishing;

[0036] Figure 6 The schematic diagram of the magnetorheological polishing of the magnetic composite abrasive;

[0037] Figure 7 The appearance comparison diagram of Fe3O4 and the prepared magnetic composite abrasive. DETAILED DESCRIPTION

[0038] This part will describe the specific embodiments of the present application in detail, the preferred embodiments of the present application are shown in the drawings, the role of the drawings is to supplement the description of the text part of the description, so that people can intuitively and visually understand each technical feature and the overall technical scheme of the present application, but it cannot be understood as a limitation on the protection scope of the present application. Embodiments

[0039] A kind of aluminum alloy magnetorheological fluid polishing method based on magnetic composite abrasive particles, comprising the following steps:

[0040] S1, magnetic composite abrasive particle preparation: 1) equipment and materials: materials: tetraethyl orthosilicate, 300nm Fe3O4, 28% ammonia water, deionized water, anhydrous ethanol; Equipment: digital strong electric mixer, ultrasonic cleaner, constant temperature digital water bath, electric heating air drying oven, 800 type centrifuge; 2) 1g Fe3O4 is weighed using a mechanical balance and placed in 125ml anhydrous ethanol, ultrasonic dispersion for 25 minutes; 25ml deionized water, 3ml ammonia water are measured and mixed thoroughly after stirring, then added to the Fe3O4 dispersion solution, mechanically stirred for 20min, and the PH value is measured to be above 8.5; 3) add 10ml tetraethyl orthosilicate, mechanically stir for 5h, then rinse with deionized water and anhydrous ethanol alternately for 3 times, dry for 4h after centrifugation to obtain the prepared magnetic composite abrasive particles; Experimental mechanism: prepare SiO2 coated Fe3O4 magnetic composite abrasive particles, use tetraethyl orthosilicate (TEOS) as silicon source, tetraethyl orthosilicate hydrolyzes in alcohol water solution, the generated silica sol is uniformly coated on the surface of Fe3O4 nanoparticles through polycondensation, and the product is dried to obtain a shell-core structure magnetic composite abrasive particle with SiO2 dry sol on the surface and Fe3O4 in the core;

[0041] Reaction chemical equation:

[0042] Si (OC2H5) 4+ 4H2O→Si (OH) 4+ 4C2H5OH

[0043] Si (OH) 4→SiO2+ 2H2O;

[0044] S2, magnetorheological fluid preparation: the magnetorheological fluid is prepared from 30% SiO2@Fe3O4 magnetic composite abrasive particles by volume fraction, 13% additives (including PH regulator (3%), complexing agent (3%), dispersant (4%), corrosion inhibitor (1%), oxidizing agent (2%)) and the balance of deionized water; The PH regulator is ammonia water, the complexing agent is citric acid (H3Cit), the dispersant is polyethylene glycol (PEG20000), the corrosion inhibitor is glycine, and the oxidizing agent is hydrogen peroxide (H2O2);

[0045] S3, magnetorheological finishing: 1) pretreatment: the 6061 aluminum alloy sample is coarsely polished for 2 minutes using 2000 and 2500 mesh SiC sandpaper, and then is successively coarsely polished for 5 minutes using 3-micron and 1-micron single-crystal diamond polishing liquid, and is finely polished for 7 minutes using 0.25-micron single-crystal diamond polishing liquid; 2) magnetorheological finishing: the 6061 aluminum alloy is subjected to magnetorheological finishing using the magnetorheological liquid described above, the magnetorheological liquid is fed into a magnetorheological finishing device, the magnetic composite abrasive particles form a flexible polishing pad at the magnetic abrasive head, the machining gap is controlled to be 1.8 mm, the PH value is controlled to be 10.1, the polishing pressure is controlled to be 6800 pa, the polishing speed is controlled to be 600-700 rpm, the polishing temperature is controlled to be 25°C, and the feeding speed is 60 mm / min, and specific operations are described in detail in CN 106 593 593 A Figure 4 ; 3) detection result: the surface roughness Ra of the sample after the pretreatment is 0.137 microns, and the surface roughness Ra of the sample after the magnetorheological finishing is 0.002 microns. Embodiment

[0046] A magnetorheological liquid polishing method for aluminum alloy based on magnetic composite abrasive particles, comprising the following steps:

[0047] S1, magnetic composite abrasive particle preparation: 1) equipment and materials: materials: tetraethyl orthosilicate, 300 nm Fe3O4, 28% ammonia water, deionized water, anhydrous ethanol; equipment: digital display powerful electric mixer, ultrasonic cleaner, constant temperature digital display water bath, electric heating air drying oven, 800 type centrifuge; 2) 1g of Fe3O4 is weighed using a mechanical balance and is placed in 150ml of anhydrous ethanol, and is ultrasonically dispersed for 25 minutes; 30ml of deionized water and 3ml of ammonia water are respectively measured, are fully mixed and stirred, and then are added to the Fe3O4 dispersion solution, and are mechanically stirred for 25 minutes, and the PH value is measured to be above 8.8; 3) 12ml of tetraethyl orthosilicate is added, and is mechanically stirred for 5.5h, and is then washed with deionized water and anhydrous ethanol alternately for 4 times, and is dried for 4h after centrifugation to obtain the prepared magnetic composite abrasive particles; the experimental mechanism is that: the SiO2-coated Fe3O4 magnetic composite abrasive particles are prepared, tetraethyl orthosilicate (TEOS) is used as a silicon source, the tetraethyl orthosilicate is subjected to a hydrolysis reaction in an alcohol-water solution, the generated silica sol uniformly coats the surface of the Fe3O4 nanoparticles through a condensation reaction, the product is dried to obtain a shell-core structure magnetic composite abrasive particle with a SiO2 dry sol on the surface and Fe3O4 in the core;

[0048] S2, magnetorheological fluid: the magnetorheological fluid is prepared from 35% by volume of SiO2@Fe3O4 magnetic composite abrasive particles, 14% by volume of additives (including PH adjuster (3.5%), complexing agent (2.5%), dispersant (4%), corrosion inhibitor (1%), and oxidizing agent (3%)), and the balance of deionized water; the PH adjuster is ammonia water, the complexing agent is citric acid (H3Cit), the dispersant is polyethylene glycol (PEG20000), the corrosion inhibitor is glycine, and the oxidizing agent is hydrogen peroxide (H2O2);

[0049] S3, magnetorheological polishing: 1) pretreatment: the 6061 aluminum alloy sample is coarsely polished for 2 minutes using 2000 and 2500 mesh SiC sandpaper, then coarsely polished for 5 minutes using 3 micron and 1 micron particle size single crystal diamond polishing liquid, and finely polished for 7 minutes using 0.25 micron particle size single crystal diamond polishing liquid; 2) magnetorheological polishing: the 6061 aluminum alloy is subjected to magnetorheological polishing treatment using the above magnetorheological fluid, the magnetorheological fluid is fed into a magnetorheological polishing device, the magnetic composite abrasive particles form a flexible polishing pad at the magnetic grinding head, and the processing gap is controlled to be 2 mm, the PH value is controlled to be 10.2, the polishing pressure is controlled to be 6850 pa, the polishing speed is controlled to be 650 rpm, the polishing temperature is controlled to be 27℃, and the feed speed is 65 mm / min, for details, refer to Figure 4 ; 3) detection result: the surface roughness Ra of the pretreated surface is 0.137 microns, and the surface roughness Ra of the magnetorheologically polished surface is 0.002 microns. Embodiment

[0050] A magnetorheological fluid polishing method for aluminum alloy based on magnetic composite abrasive particles, comprising the following steps:

[0051] S1, magnetic composite abrasive particle preparation: 1) equipment and materials: materials: tetraethyl orthosilicate, 300nm Fe3O4, 28% ammonia water, deionized water, anhydrous ethanol; equipment: digital strong electric mixer, ultrasonic cleaner, constant temperature digital water bath, electric heating air drying oven, 800 type centrifuge; 2) 1g Fe3O4 was weighed using a mechanical balance and placed in 150ml anhydrous ethanol, and ultrasonic dispersion was performed for 30 minutes; 30ml deionized water and 5ml ammonia water were measured and mixed and stirred, then added to the Fe3O4 dispersion solution, and mechanical stirring was performed for 30min, and the PH value was measured to be above 9; 3) 15ml of tetraethyl orthosilicate was added, mechanical stirring was performed for 6h, and deionized water and anhydrous ethanol were used to rinse alternately for 3 times, and after centrifugation, drying was performed for 4h to obtain the prepared magnetic composite abrasive particle; the experimental mechanism is: the SiO2 coated Fe3O4 magnetic composite abrasive particle is prepared, tetraethyl orthosilicate (TEOS) is used as the silicon source, tetraethyl orthosilicate undergoes hydrolysis reaction in alcohol water solution, the generated silica sol is uniformly coated on the surface of Fe3O4 nanoparticles through polycondensation, the product is dried to obtain a core-shell structure magnetic composite abrasive particle with SiO2 dry sol on the surface and Fe3O4 in the core;

[0052] S2, magnetic fluid preparation: the magnetic fluid is prepared from 45% by volume of SiO2@Fe3O4 magnetic composite abrasive particle, 15% by volume of additive (including PH regulator (4%), complexing agent (3%), dispersant (4%), corrosion inhibitor (1.5%), oxidizing agent (2.5%)) and the balance of deionized water; the PH regulator is ammonia water, the complexing agent is citric acid (H3Cit), the dispersant is polyethylene glycol (PEG20000), the corrosion inhibitor is glycine, and the oxidizing agent is hydrogen peroxide (H2O2);

[0053] S3, magnetic rheological polishing: 1) pretreatment: the 6061 aluminum alloy sample is coarsely ground using 2000 and 2500 mesh SiC sandpaper for 2 minutes, then coarsely polished using 3 micron and 1 micron particle size single crystal diamond polishing liquid for 5 minutes, and finely polished using 0.25 micron particle size single crystal diamond polishing liquid for 7 minutes; 2) magnetic rheological polishing: the 6061 aluminum alloy is subjected to magnetic rheological polishing treatment using the above magnetic fluid, the magnetic fluid is fed into the magnetic rheological polishing equipment, the magnetic composite abrasive particle forms a flexible polishing pad at the magnetic grinding head, and the processing gap is controlled to be 2.2mm, the PH value is controlled to be 10.3, the polishing pressure is controlled to be 6900pa, the polishing speed is controlled to be 700rpm, the polishing temperature is controlled to be 30℃, and the feed speed is 70mm / min, for details, refer to Figure 4 ; 3) detection result: the surface roughness Ra of the pretreated surface is 0.137 microns, and the surface roughness Ra of the magnetic rheological polished surface is 0.002 microns.

[0054] Please refer to Figure 5, 6 7. Weigh out 2g of Fe3O4 and the prepared magnetic composite abrasive. It can be seen that the magnetic composite abrasive is a gray-black fine powder with some agglomeration. The magnetic composite abrasive is darker in color and larger in volume than Fe3O4. It has good powder dispersion and no adhesion.

[0055] Analysis of FTIR results of magnetic composite abrasive particles:

[0056] Figure 1 Fourier transform infrared (FTIR) spectra of the silica-coated magnetite (Fe3O4) magnetic composite abrasive particles are shown. The sharp absorption peak observed at 3419.25°C is attributed to the stretching vibrations of -OH groups in the structure and adsorbed water on the surface. The broader absorption peak at 1628.17°C represents the variable-angle vibrations of -OH groups in the structure, adsorbed water, and HOH groups. The high-intensity absorption peak at 1092.89°C is the antisymmetric stretching vibration of Si-O-Si groups, and the characteristic peak at 797.43°C is the symmetric stretching vibration of Si-O-Si groups. Since this characteristic peak is a single peak near 800°C, it can be determined that the silica coating on the magnetite is amorphous. Comparing the FTIR spectra of the magnetite material, the strong absorption peaks at 566.43°C and 467.75°C are identified as the antisymmetric and symmetric stretching vibrations of the Fe-O bonds in the magnetite lattice, respectively.

[0057] XRD analysis of magnetic composite abrasive particles:

[0058] Figure 2 The XRD patterns of Fe3O4 material and silicon dioxide-coated Fe3O4 magnetic composite material are shown. XRD analysis reveals that the Fe3O4 crystal structure has a 2θ of 18.36. 0 30.18 0 35.56 0 37.20 0 43.22 0 53.66 0 57.16 0 62.72 0 74.18 0 The nine characteristic peaks at 2θ correspond to the (111), (220), (311), (222), (400), (422), (511), (440), and (533) crystal planes of the cubic anti-spinel Fe3O4 material (JCPDS: No. 99-0073). The diffraction pattern of the SiO2@Fe3O4 composite material is basically consistent with that of the Fe3O4 material. Due to the thin and amorphous nature of the coated silica layer, the peaks at 2θ = 20° are more pronounced. 0 -27 0There is a small and wide steamed bun peak in the Fe3O4 diffraction pattern, which corresponds to amorphous silicon dioxide. The SiO2@Fe3O4 composite material diffraction pattern does not appear the characteristic diffraction peak of other substances, which shows that the SiO2@Fe3O4 composite material has good purity and no other substances are generated.

[0059] SEM result analysis of magnetic composite abrasive particles:

[0060] The SEM diagram of Fe3O4 material is shown in Figure 3 a, Figure 3 b, from which it can be seen that the nano-Fe3O4 material is spherical, and the surface roughness is about 300 nm. Because of the large specific surface area, it is easy to produce agglomeration. The SEM result of SiO2@Fe3O4 magnetic composite material is shown in Figure 3 c, Figure 3 d, it can be seen that compared with the Fe3O4 material before coating, due to the presence of silicon hydroxyl on the surface of SiO2@Fe3O4 magnetic composite material, its dispersibility is better than that of Fe3O4 nanoparticles, and there is no obvious adhesion. The coated composite nanoparticles are regular spherical, the surface is smooth, and the particle size is about 500 nm.

[0061] Aluminum and its alloys are widely used in shipbuilding engineering, aerospace, optical manufacturing, medical devices, precision instruments and other fields as a non-ferrous structural metal due to its high specific strength, good electrical and thermal conductivity, excellent corrosion resistance and weldability, strong plasticity and processability, good reflectivity and low cost. With the continuous development of mechanical manufacturing industry, related high-tech industries have higher and higher requirements for the surface quality of aluminum alloy parts such as aircraft parts, high-performance parts for marine engineering, and optical system mirrors.

[0062] Chemical mechanical polishing process is a polishing process that uses chemical components in the polishing liquid to react with the polished material to form a passivation layer more suitable for the polishing process, and then removes the passivation layer by abrasive mechanical removal to achieve polishing effect and protect the substrate material. Although this process has good polishing effect, good surface morphology and roughness, the traditional chemical mechanical polishing method is difficult to process complex curved surfaces or narrow working space aluminum alloy parts because the abrasive head part is usually a soft polymer material adsorbed with free abrasive. The magnetic composite abrasive polishing pad used in magnetic finishing technology has good adaptability, self-sharpening, guiding elasticity, flexibility and other characteristics, and is widely used in the finishing of complex parts such as flat surfaces, curved surfaces, and inner and outer circles of bent pipes.

[0063] The magnetic composite abrasive magnetic finishing technology is a flexible polishing process using the magnetic composite abrasive coated with ferromagnetic material prepared by physical or chemical reaction to form a flexible polishing pad at the magnetic grinding head, and the shear force generated by the relative movement of the flexible polishing pad and the machined surface removes the polished material; the magnetic finishing technology has good adaptability to the working environment and can reduce the secondary damage to the aluminum alloy surface during the processing.

[0064] The method provided by the application combines the characteristics of chemical mechanical polishing and magnetic composite abrasive magnetic finishing technology, and aims at the problems in the traditional magnetorheological polishing process of aluminum alloy materials, such as the material removal rate reduction caused by uneven distribution of abrasives and the surface quality reduction caused by the participation of ferromagnetic particles in polishing, and proposes a new processing technology of using silica-coated ferroferric oxide magnetic composite abrasive combined with chemical auxiliary magnetic finishing of 6061 aluminum alloy. By using the self-made magnetic composite abrasive as the abrasive, the aluminum alloy special chemical mechanical polishing liquid is configured, and the magnetorheological fluid polishing technology is combined to conduct the polishing experimental research on the 6061 aluminum alloy plane material; the relationship between the processing parameters and the surface quality after the material polishing and the relationship between the different particle size magnetic composite abrasives and the surface quality after the material polishing are researched to determine the optimal polishing parameters of the new technology.

[0065] The embodiments of the application are described in detail above in combination with the drawings, but the application is not limited to the above embodiments, and various changes can be made within the knowledge of those skilled in the art without departing from the purpose of the application.

Claims

1. A method of polishing an aluminum alloy using a magnetorheological fluid based on magnetic composite abrasive grains, characterized by, Comprising the following steps: S1, magnetic composite abrasive particle preparation 1) Equipment and materials: Materials: tetraethyl orthosilicate, 300nm Fe3O4, 28% ammonia water, deionized water, anhydrous ethanol; Equipment: digital strong power electric mixer, ultrasonic cleaner, constant temperature digital water bath, electric heating air drying oven, 800 type centrifuge; 2) 1g of Fe3O4 was weighed using a mechanical balance and placed in 125-150ml of anhydrous ethanol, and ultrasonic dispersion was performed for 25-30 minutes; 25-30ml of deionized water and 3-5ml of ammonia water were measured and mixed and stirred, then added to the Fe3O4 dispersion solution, and mechanical stirring was performed for 20-30min, and the PH value was measured to be above 8.5; 3) 10-15ml of tetraethyl orthosilicate was added, mechanical stirring was performed for 5-6h, and then deionized water and anhydrous ethanol were used to rinse alternately for 3-4 times, and after centrifugation, the prepared magnetic composite abrasive particle was dried for 4h; Experimental mechanism: SiO2-coated Fe3O4 magnetic composite abrasive particles were prepared, using tetraethyl orthosilicate TEOS as the silicon source, and the tetraethyl orthosilicate underwent hydrolysis reaction in the alcohol-water solution, and the generated silica sol uniformly coated the surface of the Fe3O4 nanoparticles through polycondensation, and the product was dried to obtain a core-shell structure magnetic composite abrasive particle with a SiO2 dry sol on the surface and Fe3O4 in the core; S2, magnetic fluid preparation The magnetic fluid was prepared from 30-45% by volume of SiO2@Fe3O4 magnetic composite abrasive particles, 12-15% by volume of additives, and the balance of deionized water, and the 12-15% by volume of additives included 3-4% of PH adjuster, 2-3% of complexing agent, 3-4% of dispersant, 1-1.5% of corrosion inhibitor, and 2-3% of oxidizing agent; S3, magnetic rheological polishing 1) Pretreatment: the 6061 aluminum alloy sample was coarsely ground for 2 minutes using 2000 and 2500 mesh SiC sandpaper, and then coarsely polished for 5 minutes using 3 micron and 1 micron particle size single crystal diamond polishing liquid, and finally finely polished for 7 minutes using 0.25 micron particle size single crystal diamond polishing liquid; 2) Magnetic rheological polishing: the 6061 aluminum alloy was subjected to magnetic rheological polishing treatment using the above magnetic fluid, and the magnetic fluid was fed into the magnetic rheological polishing equipment, and the magnetic composite abrasive particles formed a flexible polishing pad at the magnetic grinding head, and the processing gap was controlled to be 1.8-2.2mm, the PH value was controlled to be 10.1-10.3, the polishing pressure was controlled to be 6800-6900pa, the polishing speed was controlled to be 600-700rpm, the polishing temperature was controlled to be 25-30℃, and the feed speed was 60-70mm / min; 3) Detection results: the surface roughness Ra of the pretreated surface was measured to be 0.137 microns using a handheld surface roughness measuring instrument, and the surface roughness Ra after magnetic rheological polishing was measured to be 0.002 microns.

2. The method of claim 1, wherein the magnetic composite abrasive particles are made of a magnetic material. The chemical equation of the S1 step reaction is as follows: Si(OC2H5)4+4H2O→Si(OH)4+4C2H5OH Si(OH)4→SiO2+2H2O.

3. The method of claim 2, wherein the magnetic composite abrasive particles are comprised of a magnetic core and a coating layer. The PH regulator in the configured magneto-rheological fluid in the S2 step is ammonia water, the complexing agent is citric acid H3Cit, the dispersing agent is polyethylene glycol PEG20000, the corrosion inhibitor is glycine, and the oxidizing agent is hydrogen peroxide H2O2.

Images