Preparation method of metal matrix composite material

Abstract

The present invention belongs to the technical field of metal-based composite materials, and specifically relates to a method for preparing metal-based composite materials. The steps include: mixing Mn3GaC@Ti, an iron alloy mixed powder, and a binder according to a mass ratio, kneading to obtain a mixed material; cooling the mixed material, granulating to obtain a granular material; injecting the granular material into a mold, injection molding to obtain a formed blank, degreasing, cooling, and sintering to obtain a metal-based composite material. The present invention solves key problems of metal-based composite materials in the prior art, such as poor molding stability under high load conditions, high thermal expansion coefficient, and short service life. The metal-based composite material prepared by the present invention introduces a powder-based negative thermal expansion material to reduce the thermal expansion coefficient, while also regulating the process and improving the stability and reliability of the material.

Description

Technical Field

[0001] The invention belongs to the technical field of metal matrix composite materials, and particularly relates to a preparation method of the metal matrix composite material. Background Art

[0002] The performance of metal matrix composites (MMCs) can be enhanced by using fillers or reinforcements. One of the most effective methods for adjusting the thermal expansion coefficient (CTE) of MMCs is by adding negative CTE fillers. By adding negative CTE fillers, a low CTE can be achieved at low volume fractions. Lowering the CTE improves material stability and reliability. For example, a low CTE reduces thermal mismatch stresses, thereby controlling crack growth.

[0003] However, negative thermal expansion materials exhibit strong chemical activity during high-temperature sintering, making them prone to interfacial reactions or agglomeration with the metal matrix. This can lead to failure of the reactive phase and instability of the composite structure, thus compromising the thermophysical properties and mechanical integrity of the composite. Furthermore, powder-based negative thermal expansion materials exhibit poor thermal stability and are prone to phase transitions or decomposition at conventional sintering temperatures, making it difficult to maintain structural integrity and uniform distribution. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the object of the present invention is to provide a method for preparing a metal matrix composite material.

[0005] To achieve the above-mentioned and other related purposes, the present invention provides the following technical solutions:

[0006] The preparation method of the metal matrix composite material comprises the following steps:

[0007] Mn3GaC@Ti, ferroalloy mixed powder and binder are mixed according to mass ratio and kneaded to obtain a mixed material; the mixed material is cooled and granulated to obtain a granular material; the granular material is injected into a mold and injection molded to obtain a molded blank; the blank is degreased, cooled and sintered to obtain a metal matrix composite material.

[0008] It should be noted that it is difficult for existing metal-based composite materials to simultaneously take into account low thermal expansion and high structural stability. Especially in high-temperature environments or under thermal cycle loads, conventional iron alloys have problems such as excessive thermal expansion coefficients and drastic changes in structural dimensions, which limit their application in precision components. Mn3GaC, as an antiperovskite material with negative thermal expansion properties, is difficult to disperse in a metal matrix, easily agglomerates during sintering, and has poor interfacial bonding with the matrix, resulting in unstable overall performance of the composite system. Traditional binder systems for injection molding are difficult to adapt to the fluidity control and molding stability requirements of high-load composite powders, and defects such as demolding cracks and sintering pores are prone to occur in high-filler systems.

[0009] Therefore, the present invention provides a new method for preparing a metal matrix composite material to solve the difficulties of the prior art. More specific details are as follows:

[0010] In one embodiment, a method for preparing Mn3GaC@Ti comprises the following steps:

[0011] A manganese source, a Ga source, and a gelling agent are dissolved, heated and stirred to form a high-viscosity gel, dried, heat-treated at 400°C-1050°C, and ground to obtain Mn3GaC powder;

[0012] Ti was coated on Mn3GaC powder using CVD method to obtain Mn3GaC@Ti.

[0013] It should be noted that the present invention adopts the sol-gel method to synthesize the Mn3GaC precursor of the antiperovskite structure, accurately proportions the raw materials and regulates the reaction process, and combines preheat treatment with high-temperature reaction to obtain a Mn3GaC powder with controllable particle size and complete crystal form, providing an excellent basic material for subsequent coating. Then, a dense Ti metal shell is deposited on the surface of the Mn3GaC powder using a low-pressure CVD method to form a core-shell structure, Mn3GaC@Ti. The Ti layer plays an effective barrier role, preventing Mn3GaC from directly contacting and reacting with the iron alloy matrix, while improving the structural stability of the particles during mixing, forming and sintering.

[0014] Further gelling agents include citric acid, manganese sources include manganese (III) acetylacetonate, and Ga sources include Ga(NO3)3·8H2O.

[0015] Furthermore, Ti is coated on the Mn3GaC powder using a CVD method, comprising the following steps:

[0016] The Mn3GaC powder is dried, spread evenly and then sent into the CVD reaction chamber.

[0017] Evacuate the CVD reaction chamber to place it in a low-pressure environment;

[0018] Argon was used as the carrier gas to bring TiCl4 vapor into the reaction chamber at a flow rate of 50-100 mL / min;

[0019] A mixed gas of argon and hydrogen was introduced into the reaction chamber at a total flow rate of 100 mL / min. The temperature of the reaction chamber was simultaneously increased to 300-600° C. The reaction was maintained at this temperature to deposit Ti on the surface of Mn 3 GaC to obtain Mn 3 GaC@Ti.

[0020] In one embodiment, the metal elements of the iron alloy mixed powder include Fe, Cr, and Ni.

[0021] In one embodiment, the binder includes polyoxymethylene, low-density polyethylene, stearic acid, and yttrium acetylacetonate solution.

[0022] It should be noted that when using the above technical solution to prepare metal-based composite materials, the iron alloy mixed powder adopts the Fe-Cr-Ni system, in which Cr is used to improve the antioxidant ability and Ni is used to adjust the thermal expansion coefficient, forming an alloy matrix that matches the thermal expansion of Mn3GaC as a whole; in terms of binder, polyoxymethylene (POM), low-density polyethylene (LDPE) and stearic acid are used to form a basic system, and yttrium acetylacetonate is added to form a rare earth complex cross-linking reinforcement system, which can improve rheological stability and reduce stress accumulation during the molding process, and form a thermally stable microporous network structure during the degreasing process, promote uniform gas escape, and reduce defects.

[0023] In one embodiment, the injection molding parameters include an injection temperature range of 150-180° C., an injection pressure of 80-120 MPa, and a holding time of 50-10 seconds.

[0024] In one embodiment, degreasing includes the following steps:

[0025] The formed blank is placed in an organic solvent and heated for soaking. After soaking, it is subjected to thermal degreasing treatment under a nitrogen protective atmosphere at a heating rate of 1-3°C / min, gradually heated to 300-450°C, and kept warm for 1-2 hours.

[0026] In one embodiment, sintering includes the following steps:

[0027] The cooled billet is placed in a high-temperature sintering furnace and sintered in an argon protective atmosphere with a heating rate of 3-5°C / min, a holding temperature of 1100-1300°C, and a holding time of 1-3 hours, maintaining a sintering atmosphere flow rate of 100-300 mL / min.

[0028] In one embodiment, Mn3GaC@Ti, iron alloy mixed powder, and binder are mixed in a mass ratio of 5-20:75-93:2-5.

[0029] The beneficial effects of the present invention are:

[0030] By constructing a Ti shell layer, the present invention significantly improves the interface adaptation problem between the negative thermal expansion particles Mn3GaC and the metal matrix, reduces the occurrence of particle agglomeration, interface debonding and thermal cracks during sintering, and improves the structural integrity and service life of the composite material.

[0031] Compared with the traditional composite system of uncoated or untreated Mn3GaC particles, the present invention can achieve a reduction in the overall thermal expansion coefficient by 20%-30% while maintaining the mechanical strength of the alloy matrix, thereby improving the material's application capability in precision components.

[0032] The binder system modified by rare earth complexes has good injection fluidity, high-temperature thermal stability and sustained release in the degreasing stage. In the high-filler system of Mn3GaC and ferroalloy powder, it can still achieve stable demolding and dense molding, which is superior to the traditional system.

[0033] The present invention solves the key problems in the prior art of metal-based composite materials, such as poor forming stability under high load conditions, high thermal expansion coefficient, and short service life. DETAILED DESCRIPTION

[0034] The present invention is further described in detail below with reference to specific embodiments.

[0035] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, a person skilled in the art can understand the specific meaning of the professional terms in the present invention in specific circumstances.

[0036] Unless otherwise specified, the materials used in the examples can be easily obtained from commercial companies.

[0037] The raw materials used in the following examples and comparative examples are as follows:

[0038] Manganese(III) acetylacetonate and Ga(NO3)3·8H2O and yttrium acetylacetonate, 99% purity;

[0039] Citric acid and ethanol, analytical grade;

[0040] Polyoxymethylene (POM): melt index 9-13 g / 10min (190°C);

[0041] Low-density polyethylene (LDPE): melt index 2-4 g / 10min;

[0042] Stearic acid and n-heptane: technical grade.

[0043] Example 1

[0044] The specific steps for preparing Mn3GaC antiperovskite compound are as follows:

[0045] Prepare an ethanol solution with a volume ratio of ethanol to deionized water of 70:30.

[0046] Take 6.0mmol of manganese (III) acetylacetonate, 2.0mmol of Ga(NO3)3·8H2O, and 12.0mmol of citric acid, add them to 100mL of ethanol solution in sequence, heat to 70℃ under magnetic stirring, and continue stirring for 1 hour to completely dissolve them and react to form a transparent solution.

[0047] Continue heating and stirring until the system gradually becomes viscous. After 1-2 hours, adjust the pH to 4-6 to obtain a green, high-viscosity gel.

[0048] The gel was transferred to a drying dish and dried with hot air at 80° C. for 12 hours to obtain a foamy solid precursor.

[0049] The dried precursor is ground into powder, placed in an alumina crucible, and placed in a tube furnace or box furnace for heat treatment in an argon flow. The temperature is first raised to 400°C at 2K / min and held for 2 hours to remove the residual organic ligands. The temperature is then raised to 1050°C at 3K / min and held for 3 hours to promote the reaction of Mn, Ga, and C elements in the solid phase, resulting in a black sponge-like material.

[0050] After the heat treatment, the mixture is cooled to room temperature and ground to obtain powder of a Mn3GaC antiperovskite compound with a particle size of 0.5-5 μm, namely, Mn3GaC powder.

[0051] Example 2

[0052] The Mn3GaC antiperovskite compound is coated based on chemical vapor deposition (CVD). The specific steps are as follows:

[0053] CVD equipment mainly consists of a reaction chamber, a heating system, a gas system, an exhaust system, and a control system.

[0054] The Mn3GaC powder prepared in Example 1 was vacuum dried at 80°C for 12 hours to fully remove moisture. Then, 5.0 g was weighed and evenly spread on an alumina support boat, and then introduced into the central area of ​​the CVD reaction chamber.

[0055] The CVD reaction chamber was evacuated to 10 -2 Torr, making the reaction chamber in a low pressure environment.

[0056] Using the gas system, TiCl4 is placed in a constant temperature oil bath and maintained below 60°C. The volatilization rate of TiCl4 is controlled, and argon is used as a carrier gas to bring the TiCl4 vapor into the reaction chamber at a flow rate of 50-100 mL / min.

[0057] A mixed gas of argon and hydrogen was introduced into the reaction chamber at a total flow rate of 100 mL / min. At the same time, the temperature of the reaction chamber was raised to 500°C by a heating system and kept at that temperature for 2 hours. Ti was reduced and deposited on the surface of the Mn3GaC powder to form a continuous metal shell.

[0058] After the reaction is completed, the TiCl4 vapor and the heating system are turned off and the system is cooled to room temperature using an argon gas flow.

[0059] The alumina support boat was taken out and the black-gray powder was collected to obtain Mn3GaC@Ti, that is, Mn3GaC as the core and Ti as the shell.

[0060] Example 3

[0061] The specific steps for preparing the metal matrix composite material are as follows:

[0062] Prepare ferroalloy mixed powder: The ferroalloy mixed powder is a spherical FeCrNi alloy powder, in which the Fe element, Cr element, and Ni element account for 93:5:2 respectively. It can also be understood that the ferroalloy mixed powder has an Fe element content of 93%, a Cr element content of 5%, and a Ni element content of 2%.

[0063] Prepare the binder: the mass ratio of polyoxymethylene (POM), low-density polyethylene (LDPE), stearic acid, and yttrium acetylacetonate solution dissolved in ethanol is 70:25:2:3.

[0064] Mixing / kneading: Mn3GaC@Ti, ferroalloy mixed powder, and binder were mixed in a mass ratio of 10:87:3, and high shear kneading was performed at 90-120°C for 40 minutes to form a uniform mixture.

[0065] Granulation: The mixed material is cooled to room temperature, coarsely crushed, and then granulated by a screw extruder or pelletizer to obtain granular materials with a particle size of about 1-3 mm.

[0066] Injection molding: Using an injection molding machine, the granular material is injected into the mold. The injection temperature is set between 150-180°C, the injection pressure is between 80-120 MPa, and the holding time is between 50-10 seconds to obtain the finished blank. It is worth noting that this step can be used to shape the blank into the desired part shape.

[0067] Solvent degreasing: Place the formed blank into n-heptane solvent, control the temperature at 40-60℃, soak for 12-24 hours to remove the binder.

[0068] Thermal debinding: Place the solvent-degreased blank in a heat treatment furnace and perform thermal debinding under a nitrogen atmosphere. Heating at a rate of 1-3°C / min, gradually raise the temperature to 300-450°C, and hold for 1-2 hours to remove any remaining insoluble thermoplastic components.

[0069] Cooling treatment: Under an inert gas or vacuum environment, cool the degreased blank to room temperature and keep it warm for 1-2 hours to further remove volatiles.

[0070] Sintering: The cooled billet is placed in a high-temperature sintering furnace and sintered under an argon atmosphere at a heating rate of 3-5°C / min, holding at 1100-1300°C for 1-3 hours, and maintaining a sintering atmosphere flow rate of 200 mL / min. This densifies the material and forms the final metal part, the metal matrix composite. During sintering, the binder between the powder particles is completely removed, allowing the metal particles to bond and achieve the desired mechanical properties.

[0071] Post-processing: Depending on the actual needs in the later stage, the sintered parts may need to be heat treated, machined or surface treated to meet the performance and dimensional requirements of the final application.

[0072] Comparative Example 1

[0073] Different from Example 3, the Mn3GaC powder prepared in Example 1 was used instead of Mn3GaC@Ti, and the remaining steps were the same as in Example 3.

[0074] Comparative Example 2

[0075] Different from Example 3, the binder components are replaced as follows:

[0076] Prepare the binder: the mass ratio of polyoxymethylene (POM), low-density polyethylene (LDPE), and stearic acid is 70:27:3.

[0077] The rest is the same as Example 3.

[0078] The metal matrix composite materials prepared by the sintering steps of Example 3, Comparative Example 1, and Comparative Example 2 were tested, and the shapes of the metal matrix composite materials were uniform.

[0079] Coefficient of Thermal Expansion (CTE): Thermal expansion behavior was measured in the range of 25-600°C using a thermomechanical analyzer (TMA) according to ASTM E831.

[0080] The results are as follows: the thermal expansion coefficient of Example 3 is 9.3×10^-6 / K, the thermal expansion coefficient of Comparative Example 1 is 12.8×10^-6 / K, and the thermal expansion coefficient of Comparative Example 2 is 10.0×10^-6 / K.

[0081] Compressive strength: Test the maximum breaking load according to GB / T 7314.

[0082] The results are as follows: the compressive strength of Example 3 is 826 MPa, the compressive strength of Comparative Example 1 is 712 MPa, and the compressive strength of Comparative Example 2 is 768 MPa.

[0083] Analysis: Regarding the thermal expansion coefficient, the composite material of Comparative Example 1 exhibited a significant number of pores during the sintering process, and its thermal expansion coefficient was significantly higher than that of Example 3. Although Comparative Example 2 used a coating material, the lack of a rare earth complex-assisted binder system resulted in insufficient molding density and sintering uniformity, resulting in suboptimal thermal expansion performance. Example 3 exhibited the lowest thermal expansion coefficient, demonstrating that the coating treatment effectively suppressed thermal expansion. The introduction of a rare earth cross-linked binder system improved feed fluidity, avoided stress concentration during demolding, and avoided uneven sintering gas release, significantly improving density.

[0084] Regarding compressive strength, the uncoated Mn3GaC has a high interfacial activity with the matrix, resulting in a loose sintered structure. However, the use of Ti coating to form a core-shell structure can effectively protect the active phase, improving structural integrity and thermal stability. Because Comparative Example 1 was uncoated, Mn3GaC reacted and agglomerated severely with the ferroalloy interface during the sintering process, resulting in reduced structural strength. Although Comparative Example 2 used Mn3GaC@Ti particles, it lacked a rare earth binder, resulting in uneven stress during the injection process and localized failure of the interface bonding, affecting the overall strength.

[0085] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will readily appreciate that other variations or modifications based on the above descriptions are possible. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A method for preparing a metal matrix composite material, characterized in that: The steps include: The Mn3GaC@Ti, iron alloy mixed powder and binder are mixed according to a mass ratio and kneaded to obtain a mixed material; the mixed material is cooled and granulated to obtain a granular material; the granular material is injected into a mold, injection-molded to obtain a molded blank, degreased, cooled and sintered to obtain a metal matrix composite material; The preparation method of Mn3GaC@Ti comprises the following steps: A manganese source, a Ga source, and a gelling agent are dissolved, heated and stirred to form a high-viscosity gel, dried, subjected to high-temperature heat treatment, and ground to obtain Mn3GaC powder; Ti was coated on Mn3GaC powder using CVD method to obtain Mn3GaC@Ti.

2. The method for preparing the metal matrix composite material according to claim 1, wherein: The gelling agent includes citric acid, the manganese source includes manganese (III) acetylacetonate, and the Ga source includes Ga(NO3)3·8H2O.

3. The method for preparing the metal matrix composite material according to claim 1, wherein: Ti is coated on Mn3GaC powder using a CVD method, comprising the following steps: The Mn3GaC powder is dried, spread evenly and then sent into the CVD reaction chamber. Evacuate the CVD reaction chamber to place it in a low-pressure environment; Argon was used as the carrier gas to bring TiCl4 vapor into the reaction chamber at a flow rate of 50-100 mL / min; A mixed gas of argon and hydrogen was introduced into the reaction chamber at a total flow rate of 100 mL / min. The temperature of the reaction chamber was simultaneously increased to 300-600° C. The reaction was maintained at this temperature to deposit Ti on the surface of Mn 3 GaC to obtain Mn 3 GaC@Ti.

4. The method for preparing the metal matrix composite material according to claim 1, wherein: The metal elements of the ferroalloy mixed powder include Fe, Cr, and Ni.

5. The method for preparing the metal matrix composite material according to claim 1, wherein: The binder includes polyoxymethylene, low-density polyethylene, stearic acid, and yttrium acetylacetonate solution.

6. The method for preparing the metal matrix composite material according to claim 1, wherein: The parameters of injection molding include injection temperature range of 150-180℃, injection pressure of 80-120MPa, and holding time of 50-10 seconds.

7. The method for preparing the metal matrix composite material according to claim 1, wherein: Degreasing includes the following steps: The formed blank is placed in an organic solvent and heated for soaking. After soaking, it is subjected to thermal degreasing treatment under a nitrogen protective atmosphere at a heating rate of 1-3°C / min, gradually heated to 300-450°C, and kept warm for 1-2 hours.

8. The method for preparing the metal matrix composite material according to claim 1, wherein: Sintering includes the following steps: The cooled billet is placed in a high-temperature sintering furnace and sintered in an argon protective atmosphere with a heating rate of 3-5°C / min, a holding temperature of 1100-1300°C, and a holding time of 1-3 hours, maintaining a sintering atmosphere flow rate of 100-300 mL / min.

9. The method for preparing the metal matrix composite material according to claim 1, wherein: Mn3GaC@Ti, ferroalloy mixed powder and binder are mixed in a mass ratio of 5-20:75-93:2-5.