Injection-molded aluminum alloy plastic-based feedstock and process for its production

Abstract

The application discloses injection molding aluminum alloy plastic base feed and a preparation process thereof, wherein the preparation process comprises the following steps that aluminum alloy raw material powder is weighed according to the following percentage content, a binder is prepared, the feed is prepared, a green body is prepared, catalytic degreasing is carried out, hot debinding and sintering and heat treatment are carried out and the like. In combination with the special requirements of the composition of 6061 aluminum alloy and the injection molding process, the application optimizes the influence of factors such as the binder formula, the degreasing temperature, the degreasing time, the sintering temperature and the sintering time, and introduces a process step such as an oxalic acid steam combined hot air circulation system, so that the comprehensive performance of the feed is obviously improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metal alloy injection molding, in particular to an injection molding aluminum alloy plastic-based feedstock and a preparation process thereof. BACKGROUND

[0002] Metal powder injection molding technology (MIM for short) is an advanced manufacturing method combining high-precision plastic injection molding process with traditional powder metallurgy technology. It is mainly used for producing small metal parts with complex shape and high precision. The MIM process mainly includes four steps: first, finely mixed metal powder and high molecular binder (such as thermoplastic polymer) to make feedstock; then, the feedstock is injected into the mold after heating and cooled to form the preliminary shape of the required part; next, the debinding step removes most of the binder through chemical or thermal treatment; finally, the metal powder particles in the part are combined through high-temperature sintering, and the density and strength are greatly improved, and finally a nearly fully dense metal part is obtained.

[0003] 6061 aluminum alloy (main alloying elements are Mg and Si, typical state is T6) is widely used in aerospace, automobile, industrial machinery and sports equipment due to its high strength, excellent weldability and easy processability. The traditional production process of aluminum alloy includes melting and casting, extrusion molding, die casting and powder metallurgy, etc., among which hot extrusion and forging are the main production methods. However, when it comes to the manufacture of small and complex shape precision parts, these traditional processes face challenges. For example, die casting can guarantee high product density and precision, but it is difficult and costly to produce complex small parts; in contrast, MIM process is more suitable due to its use of smaller raw material powder and higher shape design freedom. However, when applying MIM process to 6061 aluminum alloy, the composition of aluminum alloy, the composition of binder, the debinding temperature, the debinding time, the sintering temperature, the sintering time and other factors affect the product, resulting in problems such as high sintering residual carbon content, low density and poor mechanical properties. SUMMARY

[0004] In order to solve the above-mentioned problems, the present application provides an injection molding aluminum alloy plastic-based feedstock preparation process, which comprises the following steps:

[0005] The aluminum alloy raw material powder is weighed according to the following percentage content: silicon 0.4-0.8%, copper 0.15-0.40%, magnesium 0.9-1.2%, chromium 0.04-0.35%, iron <0.15%, manganese <0.15%, zinc <0.25%, titanium <0.05%, and the rest is aluminum;

[0006] Preparation of binder;

[0007] Preparation of feedstock: aluminum alloy raw material powder and binder are mixed in an atmosphere-protected internal mixer, mixed at a temperature of 150-190℃ for 60-90min, and then extruded and granulated to obtain the feedstock; a reasonable mixing temperature can avoid thermal degradation of the binder and ensure that the binder is fully melted;

[0008] Preparation of green body: the feedstock is melted and plasticized, then injected into a mold cavity, cooled and shaped, and taken out to obtain a green body;

[0009] Catalytic debinding: oxalic acid vapor is injected into a hot air circulation system, and the oxalic acid reacts with the binder in the green body under forced convection to cause catalytic cracking;

[0010] Thermal debinding and sintering: the green body after catalytic debinding is placed in a heating device with an inert protective gas atmosphere, and then gradually heated to 420-450℃ for debinding, and then gradually heated to 590-610℃ for sintering treatment to obtain a sintered part;

[0011] Heat treatment: the sintered part is solid-solved at 510-550℃ for 1-2h and then water-cooled, and then aged at 160-180℃ for 6-12h; a reasonable solid-solution temperature and time can ensure the formation of a supersaturated solid solution, and a reasonable aging temperature and time can help to precipitate the strengthening phase Mg2Si to improve the mechanical properties of the finished product. Here, solid solution refers to heating the alloy material to a certain temperature range, keeping it for a certain time to make as many elements as possible dissolved in the matrix to form a uniform solid solution; here, aging refers to a heat treatment process in which the alloy material after solid solution treatment and quenching is kept at a lower temperature for a certain time to promote the precipitation of a second phase in the supersaturated solid solution, thereby enhancing the strength and hardness of the material.

[0012] Preferably, the preparation of the binder comprises the following steps: mixing 44-74 parts by mass of polyformaldehyde, 5-9 parts of maleic anhydride grafted polypropylene, 4-10 parts of polyethylene glycol, 10-20 parts of polyvinyl alcohol, 2-6 parts of silane coupling agent KH550, 1-3 parts of nano-talc powder, 2-4 parts of triethyl citrate, 1-2 parts of epoxy soybean oil, and 1-2 parts of sodium bicarbonate.

[0013] Preferably, the polyethylene glycol is any one of PEG-400, PEG-2000, and PEG-4000.

[0014] Preferably, the aluminum alloy raw material powder D10 is 3-5 μm, D50 is 10-12 μm, and D90 is 10-25 μm; D10 of 3-5 μm means that 10% of the particles in the entire aluminum alloy raw material have a particle size of less than or equal to 3-5 μm, D50 of 10-12 μm means that 50% of the particles in the entire aluminum alloy raw material have a particle size of less than or equal to 10-12 μm, and D90 of 10-25 μm means that 90% of the particles in the entire aluminum alloy raw material have a particle size of less than or equal to 10-25 μm; such a particle size distribution characteristic has good matching with the injection molding process, which can ensure the flowability of the feeding system and is conducive to promoting the densification behavior in the subsequent sintering stage.

[0015] Preferably, in the preparation of the preparation feeding step, the aluminum alloy raw material and the binder are mixed in a volume ratio of 55.6-60%:40-44.4%; too high a proportion of the binder will result in insufficient green body strength after injection, high porosity after debinding, high shrinkage rate during sintering, and difficulty in obtaining a high-density metal part; too low a proportion of the binder will result in high viscosity and poor flowability of the feed, and problems such as rough surface and flow marks of the metal part.

[0016] Preferably, in the preparation of the green body step, the melting plasticization temperature is 160-190°C; a reasonable melting plasticization temperature can not only avoid thermal degradation of the binder but also ensure good flowability of the binder and avoid uneven filling.

[0017] Preferably, in the catalytic debinding step, the temperature of the hot air circulation system is controlled at 120-130°C, and the supply rate of oxalic acid vapor is 3-7 g / min; suitable catalytic reaction temperature and oxalic acid vapor supply rate can not only promote rapid and uniform removal of the binder but also avoid rapid debinding that causes the green body to deform or have structural defects.

[0018] Preferably, in the thermal debinding and sintering step, the temperature is gradually increased to 420-450°C for debinding as follows: first increased to 160-170°C, kept for 30-60 min to ensure that the low molecular components fully escape, then increased to 250-280°C, kept for 90-120 min to control the decomposition rate and reduce structural defects, continuously increased to 350-380°C, kept for 90-120 min to remove residual binder, and the process temperature is too high, which can cause the embryo to deform, and then increased to 420-450°C, kept for 30-60 min, and the process temperature is too high, which can prematurely enter the sintering stage.

[0019] Preferably, in the heat debindering step, the sintering process is as follows: continue to heat from 420~450℃ to 580~600℃, maintain the vacuum heating, and keep the temperature for 40~60min, the temperature is too high, which may cause local melting; continue to heat to 590~610℃, and keep the temperature for 2~3h, then cool to 190~210℃, the temperature and time control is suitable, which can realize sufficient sintering and avoid producing coarse grains.

[0020] Another purpose of the present application is to provide an injection molded aluminum alloy plastic-based feedstock prepared by the above-mentioned injection molding aluminum alloy plastic-based feedstock preparation process.

[0021] The beneficial effects are as follows: the new compounded binder added by the present application for the injection molding process of 6061 aluminum alloy plastic-based feedstock not only has strong intermolecular force and good interface compatibility with 6061 aluminum alloy, but also has decomposition temperature matching with the sintering temperature of 6061 aluminum alloy, high debinding efficiency, less sintering residual carbon, good fluidity, and compatibility with subsequent solid solution and aging heat treatment process, which can significantly improve the density and mechanical properties of 6061 aluminum alloy plastic-based feedstock. Specifically, the new compounded binder mainly uses polyformaldehyde as the main binder, which has low viscosity and excellent melt flowability. Polyethylene glycol and polyvinyl alcohol with low viscosity and easy melting are used to significantly reduce the melt viscosity of the whole binder. The added triethyl citrate has low viscosity and high plasticizing efficiency, and has good compatibility with polyethylene glycol. Combined with the good dispersibility of nano-talc powder, the rheological property of the feedstock is adjusted to ensure that the feedstock can quickly fill the complex cavity during injection molding, laying a complete blank foundation for subsequent processing. The amino functional group of silane coupling agent KH550 forms a chemical bond with aluminum and magnesium elements in 6061 aluminum alloy, and the maleic anhydride group of PP-g-MAH and the epoxy group in the molecule of epoxy soybean oil react with the aluminum oxide film on the surface of 6061 aluminum alloy to enhance the interface bonding force between the metal powder and the binder, reduce the risk of cracking or delamination after debinding, improve the uniformity and stability of the feedstock, and greatly reduce the risk of component segregation in the blank. The decomposition temperature range of the main component of the binder, polyformaldehyde, is highly matched with the pre-sintering temperature of 6061 aluminum alloy. Oxalic acid is used in combination with hot air to accelerate the removal of polyformaldehyde, polyvinyl alcohol, and polyethylene glycol. Then, sodium bicarbonate is used to form a microporous network by decomposing gas, which promotes the diffusion and discharge of decomposition products such as formaldehyde and carbon dioxide, significantly shortens the debinding time, reduces the carbon residue in the blank after debinding, and the residual carbon content in the blank after sintering is less than 0.02%. At the same time, it promotes the uniform precipitation of Mg2Si strengthening phase when the carbon element forms brittle Al4C3 phase with aluminum, finally makes the hardness of 6061 aluminum alloy feedstock reach more than 100HV, the tensile strength reach more than 310MPa, the yield strength reach more than 270MPa, and the elongation after heat treatment reach more than 11%, which significantly optimizes the comprehensive mechanical properties of 6061 aluminum alloy plastic-based feedstock injection molded products. Detailed Implementation

[0022] The present invention will now be described in further detail with reference to specific embodiments, so that those skilled in the art can more clearly understand the present invention.

[0023] The following embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. All other embodiments obtained by those skilled in the art based on the specific embodiments of the invention without inventive effort are within the protection scope of the invention.

[0024] In the embodiments of the present invention, unless otherwise specified, all raw material components are commercially available products well known to those skilled in the art; in the embodiments of the present invention, unless specifically specified, the technical means used are conventional means well known to those skilled in the art.

[0025] Raw material source:

[0026] Polyoxymethylene (POM), model M270-44 from Polyplastics Japan, purchased from Shanghai Handar New Materials Co., Ltd.

[0027] Maleic anhydride-grafted polypropylene (PP-g-MAH) was purchased from Shanghai Kaiyin Chemical Co., Ltd.

[0028] Polyethylene glycol, PEG-400, PEG-2000, and PEG-4000 were all purchased from Haian Petrochemical Plant in Jiangsu Province.

[0029] Polyvinyl alcohol (PVA), purchased from Chengdu Blue Whale Technology Co., Ltd.;

[0030] Silane coupling agent KH550 was purchased from Jinan Xiangfeng Weiye Chemical Co., Ltd.

[0031] Nano-talc powder, purchased from Foshan Huoju Refractory Materials Co., Ltd.;

[0032] Triethyl citrate (TEC), purchased from Jinan Xiangfeng Weiye Chemical Co., Ltd.;

[0033] Epoxidized soybean oil (ESO) was purchased from Shandong Kexing Chemical Co., Ltd.

[0034] Sodium bicarbonate was purchased from Quanzhou Hali Chemical Co., Ltd.

[0035] Paraffin wax, purchased from Shandong Xufa Chemical Co., Ltd.;

[0036] Silane coupling agent KH560 was purchased from Shandong Yuanjin New Materials Co., Ltd.

[0037] All other reagents were commercially available.

[0038] Example 1

[0039] The embodiment provides a preparation process of an injection-molded aluminum alloy plastic-based feed, and comprises the following steps:

[0040] Aluminum alloy raw material powder is weighed according to the following percentage content: 0.4% of silicon, 0.15% of copper, 0.9% of magnesium, 0.04% of chromium, and the rest is aluminum; wherein the D10 of the aluminum alloy raw material powder is 3 μm, the D50 is 10 μm, and the D90 is 10 μm;

[0041] The binder is prepared: the binder is prepared by mixing 74 parts of polyformaldehyde, 5 parts of maleic anhydride grafted polypropylene, 4 parts of polyethylene glycol PEG-400, 10 parts of polyvinyl alcohol, 2 parts of silane coupling agent KH550, 1 part of nano-talcum powder, 2 parts of triethyl citrate, 1 part of epoxy soybean oil and 1 part of sodium bicarbonate according to the mass fraction;

[0042] The feed is prepared: the aluminum alloy raw material powder and the binder are added into a banbury mixer in an argon atmosphere protection, mixed at a temperature of 150 ℃ for 60 min, and then extruded and granulated to obtain a 1 mm feed after forming a uniform paste;

[0043] The green body is prepared: the feed is added into an injection molding machine, melted and plasticized at 160 ℃, and then injected into a mold cavity, cooled and shaped, taken out, and a green body is obtained;

[0044] Catalytic debinding: oxalic acid vapor is injected into a hot air circulation system at 120 ℃ at a supply rate of 3 g / min, and the oxalic acid and the binder in the green body are subjected to a catalytic cracking reaction in a forced convection environment;

[0045] Thermal debinding and sintering: the green body after the catalytic debinding is placed in a graphite vacuum furnace with an argon protection gas atmosphere, and is subjected to debinding by gradually increasing the temperature to 420 ℃, and then is subjected to sintering treatment by gradually increasing the temperature to 590 ℃, so that a sintered part is obtained; more specifically, the process is as follows: first, the temperature is increased to 160 ℃, and the temperature is maintained for 30 min; then, the temperature is increased to 250 ℃, and the temperature is maintained for 90 min; then, the temperature is continuously increased to 350 ℃, and the temperature is maintained for 90 min; then, the temperature is continuously increased to 420 ℃, and the temperature is maintained for 30 min; then, the temperature is continuously increased to 580 ℃, and the temperature is maintained for 40 min in a vacuum; then, the temperature is continuously increased to 590 ℃, and the temperature is maintained for 2 h; and then, the temperature is decreased to 190 ℃;

[0046] Thermal treatment: the sintered part is subjected to solid solution at 510 ℃ for 1 h, and then is subjected to aging treatment at 160 ℃ for 6 h.

[0047] Embodiment 2

[0048] The embodiment provides a preparation process of an injection-molded aluminum alloy plastic-based feed, and comprises the following steps:

[0049] The aluminum alloy raw material powder is weighed according to the following percentage content: silicon 0.6%, copper 0.25%, magnesium 1.1%, chromium 0.2%, iron 0.1%, manganese 0.1%, zinc 0.12%, titanium 0.03%, and the rest is aluminum; wherein the D10 of the aluminum alloy raw material powder is 4 μm, the D50 is 11 μm, and the D90 is 17 μm;

[0050] The binder is prepared: the binder is prepared by mixing 59 parts of polyformaldehyde, 7 parts of maleic anhydride grafted polypropylene, 7 parts of polyethylene glycol PEG-2000, 15 parts of polyvinyl alcohol, 4 parts of silane coupling agent KH550, 2 parts of nano-talc powder, 3 parts of triethyl citrate, 1.5 parts of epoxy soybean oil, and 1.5 parts of sodium bicarbonate according to the mass fraction;

[0051] The feedstock is prepared: the aluminum alloy raw material powder and the binder are added to a banbury mixer under argon atmosphere protection and mixed, and then mixed at a temperature of 170°C for 75 min to form a uniform paste, and then the paste is extruded and granulated to obtain a 4mm feedstock;

[0052] The green body is prepared: the feedstock is added to an injection molding machine and melted and plasticized at 175°C, and then injected into a mold cavity, and then cooled and shaped, and then taken out to obtain a green body;

[0053] Catalytic debinding: oxalic acid vapor is injected into a hot air circulation system at a temperature of 125°C at a supply rate of 5g / min, and the oxalic acid reacts with the binder in the green body in a forced convection environment to cause catalytic cracking;

[0054] Thermal debinding and sintering: the green body after catalytic debinding is placed in a graphite vacuum furnace with an argon protection gas atmosphere, and then gradually heated to 430°C for debinding, and then gradually heated to 595°C for sintering treatment to obtain a sintered part; more specifically, the process is as follows: first heated to 165°C and kept for 45 min, then heated to 265°C and kept for 105 min, then heated to 365°C and kept for 105 min, then heated to 435°C and kept for 45 min, then heated to 590°C and kept for 50 min, then heated to 595°C and kept for 2.5h, and then cooled to 200°C;

[0055] Heat treatment: the sintered part is solution treated at 530°C for 1.5h and then water cooled, and then aged at 170°C for 9h.

[0056] Example 3

[0057] The present embodiment provides a process for preparing an injection molded aluminum alloy plastic-based feedstock, comprising the following steps:

[0058] Weigh the aluminum alloy raw material powder according to the following percentage content: silicon 0.8%, copper 0.40%, magnesium 1.2%, chromium 0.35%, iron 0.15%, manganese 0.15%, zinc 0.25%, titanium 0.05%, and the remainder is aluminum; wherein the aluminum alloy raw material powder has a D10 of 5μm, a D50 of 12μm, and a D90 of 25μm.

[0059] Preparation of adhesive: The adhesive is prepared by mixing 44 parts polyoxymethylene, 9 parts maleic anhydride grafted polypropylene, 10 parts polyethylene glycol PEG-4000, 20 parts polyvinyl alcohol, 6 parts silane coupling agent KH550, 3 parts nano talc, 4 parts triethyl citrate, 2 parts epoxidized soybean oil, and 2 parts sodium bicarbonate according to the mass ratio.

[0060] Preparation of feedstock: Aluminum alloy raw material powder and binder are added to an argon atmosphere-protected internal mixer at a volume ratio of 60%:40% and mixed at 190°C for 90 minutes to form a uniform paste. The paste is then extruded and granulated to obtain 6mm feedstock.

[0061] Preparation of green preform: The feed material is added to the injection molding machine and melted and plasticized at 190℃, then injected into the mold cavity, cooled and shaped, and removed to obtain the green preform;

[0062] Catalytic degreasing: Oxalic acid vapor is injected into a 130°C hot air circulation system at a supply rate of 7 g / min, and the oxalic acid reacts with the binder in the green embryo under forced convection.

[0063] Hot debinding and sintering: The green preform after catalytic debinding is placed in a graphite vacuum furnace with an argon protective gas atmosphere. The temperature is gradually increased to 450℃ for debinding, and then gradually increased to 600℃ for sintering to obtain the sintered part. More specifically, the process is as follows: first, the temperature is increased to 170℃ and held for 60 minutes, then increased to 280℃ and held for 120 minutes, then increased to 380℃ and held for 120 minutes, then increased to 450℃ and held for 60 minutes, then increased to 600℃ and held under vacuum for 60 minutes; then increased to 610℃ and held for 3 hours, and then cooled to 210℃.

[0064] Heat treatment: The sintered part was solution-treated at 550℃ for 2 hours, then water-cooled, and then aged at 180℃ for 12 hours.

[0065] Comparative Example 1

[0066] The difference between this comparative example and Example 2 is that paraffin wax was used to replace the binder in Example 2, and the binder preparation step was omitted. All other components and experimental steps are the same as in Example 2.

[0067] Comparative Example 2

[0068] The difference between the present comparative example and Example 2 is that maleic anhydride grafted polypropylene is not added in the preparation of the binder step, and other ingredients and experimental procedures are the same as those of Example 2.

[0069] Comparative Example 3

[0070] The difference between the present comparative example and Example 2 is that silane coupling agent KH560 is used instead of silane coupling agent KH550 in the preparation of the binder step, and other ingredients and experimental procedures are the same as those of Example 2.

[0071] Comparative Example 4

[0072] The difference between the present comparative example and Example 2 is that sodium bicarbonate is not added in the preparation of the binder step, and other ingredients and experimental procedures are the same as those of Example 2.

[0073] Comparative Example 5

[0074] The difference between the present comparative example and Example 2 is that the melt plasticization temperature is 210℃ in the preparation of the green body step, and other ingredients and experimental procedures are the same as those of Example 2.

[0075] Comparative Example 6

[0076] The difference between the present comparative example and Example 2 is that the gradual heating to 460℃ debinding process is as follows: first heated to 180℃, kept for 20min, then heated to 290℃, kept for 70min, continued to heat to 390℃, kept for 70min, and then heated to 460℃, kept for 20min, and other ingredients and experimental procedures are the same as those of Example 2.

[0077] Comparative Example 7

[0078] The difference between the present comparative example and Example 2 is that the gradual heating to 620℃ sintering process is as follows: continued to heat from 435℃ to 610℃, maintained vacuum sintering and kept for 30min, continued to heat to 620℃ and kept for 1.5h, and then cooled to 180℃, and other ingredients and experimental procedures are the same as those of Example 2.

[0079] The feedstocks prepared in Examples 1-3 and Comparative Examples 1-7 were tested for performance.

[0080] Test method:

[0081] The sintering density was tested according to the Archimedes drainage method in GB / T 3850-2015 standard;

[0082] The residual carbon content was tested according to the inert gas melting method in GB / T 38981-2020 Clause 4.1 standard;

[0083] The sintered oxygen content was tested according to GB / T 20975.25-2008 "Chemical analysis of aluminium and aluminium alloys - Part 25: Determination of oxygen content - Inert gas fusion-infrared absorption method";

[0084] The heat treatment hardness was tested according to GB / T 4340.1-2009 "Metallic materials - Vickers hardness test - Part 1 : test method";

[0085] The tensile strength, yield strength and elongation after heat treatment were all tested according to GB / T 228.1-2021 standard;

[0086] Table 1. Feeding test results table

[0087]

[0088] From the above table, the aluminum alloy feed prepared in Examples 1-3 all showed excellent performance in various properties, with a sintered density of 2.7 g / cm 3The residual carbon content is as low as 0.02wt%, the sintered oxygen content is as low as 0.15wt%, the hardness reaches 100HV or higher, the tensile strength reaches 310MPa or higher, the yield strength reaches 270MPa or higher, and the elongation after heat treatment reaches 11% or higher. Since the new compound binders added in the above embodiments are designed for the injection molding process requirements of 6061 aluminum alloy plastic matrix feed, they not only have strong intermolecular forces and good interfacial compatibility with 6061 aluminum alloy, but also match the decomposition temperature with the sintering temperature of 6061 aluminum alloy. This can effectively improve the degreasing efficiency and reduce the residual carbon in sintering. At the same time, they are compatible with subsequent heat treatment processes such as solution treatment and aging, promote the uniform precipitation of Mg2Si strengthening phase, and significantly improve the density and mechanical properties of 6061 aluminum alloy plastic matrix feed. In Comparative Example 1, after replacing the binder in Example 2 with paraffin wax, the sintering density decreased to 2.52 g / cm³, the residual carbon content increased to 0.18 wt%, the tensile strength was only 245 MPa, and the elongation after heat treatment was only 5.3%, indicating that the paraffin wax residue was severely degreased and the interfacial bonding was poor, resulting in a significant decline in the mechanical properties of the feedstock. In Comparative Example 2, after omitting maleic anhydride-grafted polypropylene, the sintering oxygen content increased, and the hardness and tensile strength decreased. This may be due to the weakened interfacial bonding between the binder and the metal powder after the absence of maleic anhydride-grafted polypropylene. In Comparative Example 3, replacing silane coupling agent KH550 with silane coupling agent KH560 also resulted in a decrease in density, an increase in residual carbon content, and a decline in mechanical properties. This may be because the epoxy groups contained in silane coupling agent KH560 are difficult to form effective chemical bonds with aluminum, magnesium elements, polyoxymethylene, maleic anhydride-grafted polypropylene, and other components in the aluminum alloy, leading to a decrease in the interfacial compatibility between the metal powder and the binder, and a deterioration in the uniformity of the feedstock. In Comparative Example 4, without the addition of sodium bicarbonate, the discharge of decomposition products was hindered, leading to an increase in residual carbon content. In Comparative Example 5, the excessively high melt plasticizing temperature caused binder degradation, resulting in decreased feed fluidity and insufficient filling, leading to a decrease in density. Both Comparative Examples 6 and 7 exhibited decreased density, deteriorated mechanical strength, and reduced elongation. This may be due to improper temperature and time control during the debinding and sintering process, causing preform deformation or grain coarsening. The above comparative examples fully demonstrate that the synergistic optimization of the binder formulation and process parameters in this application plays a crucial role in improving the overall performance of aluminum alloy injection molding feedstocks.

[0089] In summary, this application optimizes the influence of factors such as binder formulation, degreasing temperature, degreasing time, sintering temperature, and sintering time, taking into account the specific requirements of the composition of 6061 aluminum alloy and its injection molding process. It also introduces process steps such as oxalic acid vapor combined with a hot air circulation system, which ultimately significantly improves the feed density and mechanical properties.

[0090] The above merely illustrates the embodiments of the present application, but should not be taken as limitations. The present application can have various modifications and changes for those skilled in the art. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of the present application should be included in the scope of claims of the present application.

Claims

1. A process for preparing injection-molded aluminum alloy plastic matrix feedstock, characterized in that, Includes the following steps: Weigh the aluminum alloy raw material powder according to the following percentage content: silicon 0.4~0.8%, copper 0.15~0.40%, magnesium 0.9~1.2%, chromium 0.04~0.35%, iron <0.15%, manganese <0.15%, zinc <0.25%, titanium <0.05%, and the remainder is aluminum; Preparation of adhesives; Preparation of feedstock: The aluminum alloy raw material powder and the binder are added to an atmosphere-protected internal mixer and mixed. The mixture is then kneaded at 150~190℃ for 60~90 minutes to form a uniform paste. The paste is then extruded and granulated to obtain the feedstock. Preparation of the green preform: The feed material is melted and plasticized and then injected into the mold cavity, cooled and shaped, and then removed to obtain the green preform; Catalytic degreasing: Oxalic acid vapor is injected into a hot air circulation system, and the oxalic acid and the binder in the green embryo undergo a catalytic cracking reaction under forced convection. Hot degreasing and sintering: The green embryo after catalytic degreasing is placed in a heating device with an inert protective gas atmosphere, and the temperature is gradually increased to 420~450℃ for degreasing, and then gradually increased to 590~610℃ for sintering treatment to obtain sintered parts; Heat treatment: The sintered part is solution treated at 510~550℃ for 1~2h, then water cooled, and then aged at 160~180℃ for 6~12h. The preparation of the adhesive includes the following steps: the adhesive, according to the specified mass parts, is prepared by mixing 44-74 parts of polyoxymethylene, 5-9 parts of maleic anhydride-grafted polypropylene, 4-10 parts of polyethylene glycol, 10-20 parts of polyvinyl alcohol, 2-6 parts of silane coupling agent KH550, 1-3 parts of nano talc, 2-4 parts of triethyl citrate, 1-2 parts of epoxidized soybean oil, and 1-2 parts of sodium bicarbonate; In the preparation of the green embryo, the melt plasticizing temperature is 160~190℃; In the hot desintering step, the degreasing process of gradually raising the temperature to 420~450℃ is as follows: first raise the temperature to 160~170℃, hold for 30~60 min, then raise the temperature to 250~280℃, hold for 90~120 min, continue to raise the temperature to 350~380℃, hold for 90~120 min, and then raise the temperature to 420~450℃, hold for 30~60 min; In the hot desintering step, the sintering process of gradually raising the temperature to 590~610℃ is as follows: continue to raise the temperature from 420~450℃ to 580~600℃, maintain vacuum firing, and hold for 40~60 minutes; continue to raise the temperature to 590~610℃ and hold for 2~3 hours, and then lower the temperature to 190~210℃.

2. The injection molding aluminum alloy substrate feeding process according to claim 1, characterized in that, The polyethylene glycol is any one of PEG-400, PEG-2000, and PEG-4000.

3. The injection molding aluminum alloy substrate feeding process according to claim 1, characterized in that, The aluminum alloy raw material powder has a D10 of 3~5μm, a D50 of 10~12μm, and a D90 of 10~25μm.

4. The injection molding aluminum alloy substrate feeding process according to claim 1, characterized in that, In the feed preparation step, the aluminum alloy raw material and the binder are mixed at a volume ratio of 55.6~60%: 40~44.4%.

5. The injection molding aluminum alloy substrate feeding process according to claim 1, characterized in that, In the catalytic degreasing step, the temperature of the hot air circulation system is controlled at 120~130℃, and the oxalic acid vapor supply rate is 3~7g / min.

6. A feedstock for injection molding aluminum alloy substrates, characterized in that, The aluminum alloy plastic matrix is ​​prepared by the injection molding process according to any one of claims 1 to 5.

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