A method for preparing a lightweight high-rigidity heterogeneous aluminum matrix composite

Abstract

A method for preparing a lightweight, high-stiffness heterogeneous aluminum-based composite material is disclosed, which addresses the challenge of combining aluminum-lithium alloy as a reinforcement with an aluminum matrix. The composite material prepared by this invention exhibits a more designable microstructure. Based on regional compositional differences, this preparation process can theoretically introduce soft and hard regions within the material, and introduce a large number of geometrically necessary dislocations at the interface between the soft and hard regions, inducing back stress strengthening and promoting coordinated deformation, thus contributing to a synergistic improvement in the material's strength and plasticity. The aluminum-lithium alloy powder undergoes surface oxidation to form a lithium oxide shell, strengthening the structural strength of the aluminum-lithium alloy powder. Furthermore, the lithium oxide shell hinders grain boundary migration during recrystallization, effectively suppressing recrystallization in the aluminum-based composite material during subsequent deformation-heat treatment, preserving fine-grain strengthening, work hardening, and dispersion strengthening effects, and effectively improving the strength of the heterogeneous composite material.

Description

Technical Field

[0001] This invention relates to a method for preparing high-stiffness heterogeneous aluminum-based composite materials. Background Technology

[0002] Aluminum-lithium alloys, due to their combination of low density, high specific stiffness, and excellent specific strength, have broad application prospects in fields with urgent lightweighting needs, such as aerospace and rail transportation. If aluminum-lithium alloys are used as reinforcements in combination with aluminum matrices, novel aluminum-based composite materials with heterogeneous characteristics can be prepared.

[0003] However, the process window faces severe challenges in actual infiltration preparation. To ensure good flow and filling capacity of the molten aluminum, the preform needs to be preheated to a high temperature. However, high temperatures weaken the bonding between the reinforcements (aluminum-lithium alloy) in the preform, leading to a sharp decrease in its overall structural strength. When the molten aluminum flows through the pores inside the preform under external pressure, the resulting fluid compressive stress, once exceeding the preform's bearing capacity limit at that temperature, causes irreversible collapse or local deformation. This results in typical casting defects such as reinforcement skeleton crushing and localized enrichment of molten aluminum forming "aluminum sandwich" bands within the final material, severely degrading the material's mechanical properties and microstructure uniformity.

[0004] Therefore, the key to eliminating the structural defects caused by the high-temperature instability of the precast body lies in effectively improving the structural strength of the precast body under preheating conditions. Summary of the Invention

[0005] To address the challenge of combining aluminum-lithium alloys as reinforcements with aluminum matrices, this invention proposes a method for preparing lightweight, high-stiffness heterogeneous aluminum-based composite materials.

[0006] The preparation method of the lightweight, high-stiffness heterogeneous aluminum-based composite material of the present invention is carried out according to the following steps:

[0007] 1. Weigh aluminum-lithium alloy powder and aluminum matrix as raw materials; pre-oxidize the aluminum-lithium alloy powder.

[0008] The pre-oxidation treatment process is as follows: heating to 300°C and holding at that temperature for 1-3 hours in an oxidizing atmosphere;

[0009] 2. Fill aluminum-lithium alloy powder into a mold and cold press it to obtain a preform;

[0010] 3. Preheat the preform and mold; melt the aluminum matrix and heat it to obtain molten aluminum matrix; place the preheated preform on the press table, pour the molten aluminum matrix into the mold, apply pressure to the molten aluminum matrix using the press for pressure impregnation, and demold to obtain the billet after completion;

[0011] The pressure impregnation process is as follows: First, the impregnation pressure is adjusted to 5-20MPa and the impregnation rate is 1-10mm / s; after aluminum liquid seeps out from the bottom of the preform, the impregnation pressure is adjusted to 20-60MPa, and the pressure is maintained for 1-8 minutes after reaching the pressure.

[0012] Fourth, the composite material undergoes deformation treatment and heat treatment, thus completing the process.

[0013] 1. This invention employs a pressure infiltration process to prepare a lightweight, high-stiffness heterogeneous aluminum-based composite material, resulting in a more customizable microstructure. Based on regional compositional differences, this preparation process can, in principle, introduce soft and hard regions within the material, and at the interface between these regions, introduce a large number of geometrically necessary dislocations, inducing back stress strengthening and promoting coordinated deformation, thus contributing to a synergistic improvement in the material's strength and plasticity.

[0014] 2. The aluminum-lithium alloy powder used in this invention undergoes oxidation to form a lithium oxide shell such as Li2O, Li3N, or Li2CO3 on its surface, thereby strengthening the structural strength of the aluminum-lithium alloy powder. Furthermore, the lithium oxide shell hinders grain boundary migration during recrystallization, effectively suppressing recrystallization in aluminum-based composite materials during subsequent deformation-heat treatment, preserving fine-grain strengthening, work hardening, and dispersion strengthening effects, and effectively improving the strength of heterogeneous composite materials.

[0015] 3. This invention processes the material through extrusion, which helps improve poor bonding in the as-cast microstructure. Deformation helps break up the oxide layer on the surface of the aluminum-lithium alloy powder, making it a reinforcement. Simultaneously, work hardening is introduced, promoting the precipitation of strengthening phases during subsequent heat treatment. The broken oxide layer also helps suppress recrystallization during the solution treatment process, preserving the work hardening effect. Attached Figure Description

[0016] Figure 1 Here is a macroscopic image of the aluminum-based composite material obtained in Example 1;

[0017] Figure 2 This is a macroscopic image of the aluminum-based composite material obtained in Comparative Example 5. Detailed Implementation

[0018] The technical solution of the present invention is not limited to the specific embodiments listed below, but also includes any reasonable combination of the specific embodiments.

[0019] Specific Implementation Method 1: The preparation method of the lightweight, high-stiffness heterogeneous aluminum-based composite material in this implementation method is carried out according to the following steps:

[0020] 1. Weigh aluminum-lithium alloy powder and aluminum matrix as raw materials; pre-oxidize the aluminum-lithium alloy powder.

[0021] The pre-oxidation treatment process is as follows: heating to 300°C and holding at that temperature for 1-3 hours in an oxidizing atmosphere;

[0022] 2. Fill aluminum-lithium alloy powder into a mold and cold press it to obtain a preform;

[0023] 3. Preheat the preform and mold; melt the aluminum matrix and heat it to obtain molten aluminum matrix; place the preheated preform on the press table, pour the molten aluminum matrix into the mold, apply pressure to the molten aluminum matrix using the press for pressure impregnation, and demold to obtain the billet after completion;

[0024] The pressure impregnation process is as follows: First, the impregnation pressure is adjusted to 5-20MPa and the impregnation rate is 1-10mm / s; after aluminum liquid seeps out from the bottom of the preform, the impregnation pressure is adjusted to 20-60MPa, and the pressure is maintained for 1-8 minutes after reaching the pressure.

[0025] Fourth, the composite material undergoes deformation treatment and heat treatment, thus completing the process.

[0026] This embodiment has the following beneficial effects:

[0027] 1. This embodiment uses a pressure infiltration process to prepare a lightweight, high-rigidity heterogeneous aluminum-based composite material, which has a more designable microstructure. Based on regional compositional differences, this preparation process can, in principle, introduce soft and hard regions within the material, and introduce a large number of geometrically necessary dislocations at the interface between the soft and hard regions, inducing back stress strengthening and promoting coordinated deformation, which helps to synergistically improve the strength and plasticity of the material.

[0028] 2. In this embodiment, the aluminum-lithium alloy powder is oxidized to form a lithium oxide shell such as Li2O, Li3N, or Li2CO3 on its surface, thereby strengthening the structural strength of the aluminum-lithium alloy powder. Furthermore, the lithium oxide shell can hinder grain boundary migration during recrystallization, effectively suppressing recrystallization of the aluminum-based composite material during subsequent deformation-heat treatment, preserving the effects of fine-grain strengthening, work hardening, and dispersion strengthening, and effectively improving the strength of the heterogeneous composite material.

[0029] 3. This embodiment processes the material through extrusion, which helps improve poor bonding in the as-cast microstructure. Deformation helps break up the oxide layer on the surface of the aluminum-lithium alloy powder, making it a reinforcement. Simultaneously, work hardening is introduced, promoting the precipitation of strengthening phases during subsequent heat treatment. The broken oxide layer also helps suppress recrystallization during the solution treatment process, preserving the work hardening effect.

[0030] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the volume fraction of aluminum-lithium alloy powder in the raw materials mentioned in Step One is 30-80%.

[0031] Specific Implementation Method 3: This implementation method differs from Specific Implementation Method 1 or 2 in that the aluminum-lithium alloy powder mentioned in step 1 has a particle size of 1-200μm and a Li content of 0.5-10wt.%.

[0032] Specific Implementation Method Four: This implementation method differs from one of Specific Implementation Methods One to Three in that: the aluminum matrix mentioned in step one is pure aluminum or an aluminum alloy; the aluminum alloy is one or a combination of several of the following: Al-Si alloy, Al-Si-Cu alloy, Al-Cu alloy, Al-Cu-Mg alloy, Al-Cu-Mg-Si alloy, Al-Ag alloy, Al-RE alloy, Al-Zn-Cu alloy, Al-Zn-Mg-Cu alloy, Al-Mg alloy, and Al-Mn alloy.

[0033] Specific Implementation Method 5: This implementation method differs from Specific Implementation Methods 1 to 4 in that the cold pressing process described in step 2 is as follows: the compression speed is 0.1-3 mm / min, the pressure is 5-70 MPa, and the holding time is 10-20 min.

[0034] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that: the heating rate of the preform and mold in step three is 5-20℃ / min, the preheating temperature is 20-60℃ lower than the melting point of aluminum-lithium alloy powder, and the holding time is 1-3h.

[0035] Specific Implementation Method Seven: This implementation method differs from one of Specific Implementation Methods One to Six in that: in step three, the aluminum substrate metal is melted and heated to 200-280°C above the melting point of the aluminum substrate.

[0036] Specific Implementation Method Eight: This implementation method differs from one of the specific implementation methods one to seven in that the deformation treatment described in step four is extrusion or rolling.

[0037] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Method Eight in that the extrusion ratio is 8-18:1 and the cumulative reduction in rolling is 70-99%.

[0038] Specific Implementation Method 10: This implementation method differs from Specific Implementation Methods 1 to 9 in that the heat treatment described in step 4 is one or a combination of several of the following: annealing, solution treatment, quenching, pre-aging, single-stage aging, double-stage aging, and multi-stage aging.

[0039] Example 1:

[0040] The preparation method of the lightweight, high-stiffness heterogeneous aluminum-based composite material in this embodiment is carried out according to the following steps:

[0041] 1. Weigh aluminum-lithium alloy powder and aluminum matrix as raw materials; pre-oxidize the aluminum-lithium alloy powder.

[0042] The volume fraction of aluminum-lithium alloy powder in the raw material is 67%;

[0043] The aluminum-lithium alloy powder has a particle size of 70-90 μm and a Li content of 2 wt.%.

[0044] The aluminum matrix is ​​Al-11Cu-4Mg-0.5Si;

[0045] The pre-oxidation treatment process is as follows: heating to 300°C and holding at that temperature for 2 hours in an oxidizing atmosphere;

[0046] 2. Fill aluminum-lithium alloy powder into a mold and cold press it to obtain a preform;

[0047] The cold pressing process is as follows: compression speed is 1 mm / min, pressure is 50 MPa, and holding time is 10 min;

[0048] 3. Preheat the preform and mold; melt the aluminum matrix and heat it to obtain molten aluminum matrix; place the preheated preform on the press table, pour the molten aluminum matrix into the mold, apply pressure to the molten aluminum matrix using the press for pressure impregnation, and demold to obtain the billet after completion;

[0049] The preform and mold are preheated at a rate of 10℃ / min, a preheating temperature of 610℃, and a holding time of 1h.

[0050] The aluminum matrix metal is melted and heated to 870°C;

[0051] The pressure impregnation process is as follows: First, the impregnation pressure is adjusted to 5MPa and the impregnation rate is 2mm / s; after aluminum liquid seeps out from the bottom of the preform, the impregnation pressure is adjusted to 50MPa and pressure is maintained for 8 minutes after reaching the pressure.

[0052] Fourth, the composite material undergoes deformation treatment and heat treatment to complete the process;

[0053] The deformation treatment is extrusion; the extrusion ratio is 12:1.

[0054] The heat treatment consists of solution treatment and single-stage aging: first, solution treatment is performed in a muffle furnace at 520°C for 1 hour, followed by water quenching to room temperature; finally, aging is performed at 175°C for 16 hours.

[0055] Example 2

[0056] The preparation method of the lightweight, high-stiffness heterogeneous aluminum-based composite material in this embodiment is carried out according to the following steps:

[0057] 1. Weigh aluminum-lithium alloy powder and aluminum matrix as raw materials; pre-oxidize the aluminum-lithium alloy powder.

[0058] The volume fraction of aluminum-lithium alloy powder in the raw material is 67%;

[0059] The aluminum-lithium alloy powder has a particle size of 70-90 μm and a Li content of 2 wt.%.

[0060] The aluminum matrix is ​​Al-11Cu-4Mg-0.5Si;

[0061] The pre-oxidation treatment process is as follows: heating to 300°C and holding at that temperature for 2 hours in an oxidizing atmosphere;

[0062] 2. Fill aluminum-lithium alloy powder into a mold and cold press it to obtain a preform;

[0063] The cold pressing process is as follows: compression speed is 1 mm / min, pressure is 50 MPa, and holding time is 10 min;

[0064] 3. Preheat the preform and mold; melt the aluminum matrix and heat it to obtain molten aluminum matrix; place the preheated preform on the press table, pour the molten aluminum matrix into the mold, apply pressure to the molten aluminum matrix using the press for pressure impregnation, and demold to obtain the billet after completion;

[0065] The preform and mold are preheated at a rate of 10℃ / min, a preheating temperature of 610℃, and a holding time of 1h.

[0066] The aluminum matrix metal is melted and heated to 870°C;

[0067] The pressure impregnation process is as follows: First, the impregnation pressure is adjusted to 5MPa and the impregnation rate is 2mm / s; after aluminum liquid seeps out from the bottom of the preform, the impregnation pressure is adjusted to 50MPa and pressure is maintained for 8 minutes after reaching the pressure.

[0068] Fourth, the composite material undergoes deformation treatment and heat treatment to complete the process;

[0069] The deformation treatment is rolling; the rolling temperature is 450 ℃, the single-pass reduction is 20%, and the cumulative reduction is 70%.

[0070] The heat treatment consists of solution treatment and single-stage aging: first, solution treatment is performed in a muffle furnace at 520°C for 1 hour, followed by water quenching to room temperature; finally, aging is performed at 175°C for 16 hours.

[0071] Example 3

[0072] The difference between this embodiment and Embodiment 1 is that:

[0073] The preparation method of the lightweight, high-stiffness heterogeneous aluminum-based composite material in this embodiment is carried out according to the following steps:

[0074] 1. Weigh aluminum-lithium alloy powder and aluminum matrix as raw materials; pre-oxidize the aluminum-lithium alloy powder.

[0075] The volume fraction of aluminum-lithium alloy powder in the raw material is 67%;

[0076] The aluminum-lithium alloy powder has a particle size of 70-90 μm and a Li content of 2 wt.%.

[0077] The aluminum matrix is ​​Al-11Cu-4Mg-0.5Si;

[0078] The pre-oxidation treatment process is as follows: heating to 300°C and holding at that temperature for 2 hours in an oxidizing atmosphere;

[0079] 2. Fill aluminum-lithium alloy powder into a mold and cold press it to obtain a preform;

[0080] The cold pressing process is as follows: compression speed is 1 mm / min, pressure is 50 MPa, and holding time is 10 min;

[0081] 3. Preheat the preform and mold; melt the aluminum matrix and heat it to obtain molten aluminum matrix; place the preheated preform on the press table, pour the molten aluminum matrix into the mold, apply pressure to the molten aluminum matrix using the press for pressure impregnation, and demold to obtain the billet after completion;

[0082] The preform and mold are preheated at a rate of 10℃ / min, a preheating temperature of 610℃, and a holding time of 1h.

[0083] The aluminum matrix metal is melted and heated to 870°C;

[0084] The pressure impregnation process is as follows: First, the impregnation pressure is adjusted to 5MPa and the impregnation rate is 2mm / s; after aluminum liquid seeps out from the bottom of the preform, the impregnation pressure is adjusted to 50MPa and pressure is maintained for 8 minutes after reaching the pressure.

[0085] Fourth, the composite material undergoes deformation treatment and heat treatment to complete the process;

[0086] The deformation treatment is extrusion; the extrusion ratio is 12:1.

[0087] The heat treatment process is as follows: the extruded material is placed in a muffle furnace at 520°C and kept at that temperature for 1 hour, then quenched in water to room temperature, and then kept at 120°C for 10 hours for the first stage of aging treatment; finally, it is kept at 175°C for 14 hours for the second stage of aging treatment.

[0088] Example 4

[0089] The preparation method of the lightweight, high-stiffness heterogeneous aluminum-based composite material in this embodiment is carried out according to the following steps:

[0090] 1. Weigh aluminum-lithium alloy powder and aluminum matrix as raw materials; pre-oxidize the aluminum-lithium alloy powder.

[0091] The volume fraction of aluminum-lithium alloy powder in the raw material is 67%;

[0092] The aluminum-lithium alloy powder has a particle size of 70-90 μm and a Li content of 2 wt.%.

[0093] The aluminum matrix is ​​Al-11Cu-4Mg-0.5Si;

[0094] The pre-oxidation treatment process is as follows: heating to 300°C and holding at that temperature for 2 hours in an oxidizing atmosphere;

[0095] 2. Fill aluminum-lithium alloy powder into a mold and cold press it to obtain a preform;

[0096] The cold pressing process is as follows: compression speed is 1 mm / min, pressure is 50 MPa, and holding time is 10 min;

[0097] 3. Preheat the preform and mold; melt the aluminum matrix and heat it to obtain molten aluminum matrix; place the preheated preform on the press table, pour the molten aluminum matrix into the mold, apply pressure to the molten aluminum matrix using the press for pressure impregnation, and demold to obtain the billet after completion;

[0098] The preform and mold are preheated at a rate of 10℃ / min, a preheating temperature of 610℃, and a holding time of 1h.

[0099] The aluminum matrix metal is melted and heated to 870°C;

[0100] The pressure impregnation process is as follows: First, the impregnation pressure is adjusted to 5MPa and the impregnation rate is 2mm / s; after aluminum liquid seeps out from the bottom of the preform, the impregnation pressure is adjusted to 50MPa and pressure is maintained for 8 minutes after reaching the pressure.

[0101] Fourth, the composite material undergoes deformation treatment and heat treatment to complete the process;

[0102] The deformation treatment is rolling; the rolling temperature is 450 ℃, the single-pass reduction is 20%, and the cumulative reduction is 70%.

[0103] The heat treatment process is as follows: the extruded material is placed in a muffle furnace at 520°C and kept at that temperature for 1 hour, then quenched in water to room temperature, and then kept at 120°C for 10 hours for the first stage of aging treatment; finally, it is kept at 175°C for 14 hours for the second stage of aging treatment.

[0104] Comparative Example 1

[0105] The preparation method of this comparative aluminum-based composite material is carried out according to the following steps:

[0106] 1. Weigh out aluminum-lithium alloy powder and aluminum matrix as raw materials;

[0107] The volume fraction of aluminum-lithium alloy powder in the raw material is 67%;

[0108] The aluminum-lithium alloy powder has a particle size of 70-90 μm and a Li content of 2 wt.%.

[0109] The aluminum matrix is ​​Al-11Cu-4Mg-0.5Si;

[0110] 2. Under an Ar atmosphere, the weighed raw materials are melted in a crucible and heated to 720°C. The molten metal is then poured into a cast iron mold at room temperature. After cooling, the composite material is demolded.

[0111] Third, the composite material undergoes deformation treatment and heat treatment to complete the process;

[0112] The deformation treatment is extrusion; the extrusion ratio is 12:1.

[0113] The heat treatment consists of solution treatment and single-stage aging: first, solution treatment is performed in a muffle furnace at 520°C for 1 hour, followed by water quenching to room temperature; finally, aging is performed at 175°C for 16 hours.

[0114] Comparative Example 2

[0115] The difference between this comparative example and Comparative Example 1 is that:

[0116] Step 3 involves deforming and heat-treating the composite material;

[0117] The deformation treatment is rolling; the rolling temperature is 450 ℃, the single-pass reduction is 20%, and the cumulative reduction is 70%.

[0118] The heat treatment consists of solution treatment and single-stage aging: first, solution treatment is performed in a muffle furnace at 520°C for 1 hour, followed by water quenching to room temperature; finally, aging is performed at 175°C for 16 hours.

[0119] Comparative Example 3

[0120] The difference between this comparative example and Comparative Example 1 is that:

[0121] Step 3 involves deforming and heat-treating the composite material;

[0122] The deformation treatment is extrusion; the extrusion ratio is 12:1.

[0123] The heat treatment process is as follows: the extruded material is placed in a muffle furnace at 520°C and kept at that temperature for 1 hour, then quenched in water to room temperature, and then kept at 120°C for 10 hours for the first stage of aging treatment; finally, it is kept at 175°C for 14 hours for the second stage of aging treatment.

[0124] Comparative Example 4

[0125] The difference between this comparative example and Comparative Example 1 is that:

[0126] Step 3 involves deforming and heat-treating the composite material;

[0127] The deformation treatment is rolling; the rolling temperature is 450 ℃, the single-pass reduction is 20%, and the cumulative reduction is 70%.

[0128] The heat treatment process is as follows: the extruded material is placed in a muffle furnace at 520°C and kept at that temperature for 1 hour, then quenched in water to room temperature, and then kept at 120°C for 10 hours for the first stage of aging treatment; finally, it is kept at 175°C for 14 hours for the second stage of aging treatment.

[0129] Comparative Example 5

[0130] The preparation method of this comparative lightweight high-stiffness heterogeneous aluminum-based composite material is carried out according to the following steps:

[0131] 1. Weigh out aluminum-lithium alloy powder and aluminum matrix as raw materials;

[0132] The volume fraction of aluminum-lithium alloy powder in the raw material is 67%;

[0133] The aluminum-lithium alloy powder has a particle size of 70-90 μm and a Li content of 2 wt.%.

[0134] The aluminum matrix is ​​Al-11Cu-4Mg-0.5Si;

[0135] 2. Fill aluminum-lithium alloy powder into a mold and cold press it to obtain a preform;

[0136] The cold pressing process is as follows: compression speed is 1 mm / min, pressure is 50 MPa, and holding time is 10 min;

[0137] 3. Preheat the preform and mold; melt the aluminum matrix and heat it to obtain molten aluminum matrix; place the preheated preform on the press table, pour the molten aluminum matrix into the mold, apply pressure to the molten aluminum matrix using the press for pressure impregnation, and demold to obtain the billet after completion;

[0138] The preform and mold are preheated at a rate of 10℃ / min, a preheating temperature of 610℃, and a holding time of 1h.

[0139] The aluminum matrix metal is melted and heated to 870°C;

[0140] The pressure impregnation process is as follows: First, the impregnation pressure is adjusted to 5MPa and the impregnation rate is 2mm / s; after aluminum liquid seeps out from the bottom of the preform, the impregnation pressure is adjusted to 50MPa and pressure is maintained for 8 minutes after reaching the pressure.

[0141] Fourth, the composite material undergoes deformation treatment and heat treatment to complete the process;

[0142] The deformation treatment is extrusion; the extrusion ratio is 12:1.

[0143] The heat treatment consists of solution treatment and single-stage aging: first, solution treatment is performed in a muffle furnace at 520°C for 1 hour, followed by water quenching to room temperature; finally, aging is performed at 175°C for 16 hours.

[0144] Table 1 Performance Test Results

[0145]

[0146] Figure 1 The image shows a macroscopic picture of the aluminum-based composite material obtained in Example 1. It can be seen that the material has good uniformity and no obvious casting defects such as collapse or aluminum layer inclusions were observed. Figure 2 The image shown is a macroscopic view of the aluminum-based composite material obtained in Comparative Example 5. The material height is less than the preform height under pre-compression, and significant collapse and aluminum layer inclusion are observed. The underlying reason for the collapse and aluminum inclusion is that the structural strength of the preform during pressure infiltration is less than the pressure required for molten aluminum to fill the pores. The pressure required for molten aluminum filling is affected by fluidity, composition, porosity, pore size, and wettability, and is difficult to change for a specific material. The structural strength of the preform is greatly affected by temperature; the higher the temperature, the lower the strength. During pressure infiltration, heat exchange occurs between the preform and the molten aluminum, further increasing the preform temperature and continuously reducing its strength. Therefore, it is difficult to adjust the structural strength of the preform by controlling its preheating temperature. No defects were observed in Example 1 because the strength of the oxide layer obtained during pre-oxidation is less affected by temperature, resulting in improved structural strength of the preform.

Claims

1. A method for preparing a lightweight, high-stiffness heterogeneous aluminum-based composite material, characterized in that: The preparation method of lightweight, high-stiffness heterogeneous aluminum-based composite materials is carried out according to the following steps:

1. Weigh aluminum-lithium alloy powder and aluminum matrix as raw materials; pre-oxidize the aluminum-lithium alloy powder. The pre-oxidation treatment process is as follows: heating to 300°C and holding at that temperature for 1-3 hours in an oxidizing atmosphere; 2. Fill aluminum-lithium alloy powder into a mold and cold press it to obtain a preform; 3. Preheat the preform and mold; melt the aluminum matrix and heat it to obtain molten aluminum matrix; place the preheated preform on the press table, pour the molten aluminum matrix into the mold, apply pressure to the molten aluminum matrix using the press for pressure impregnation, and demold to obtain the billet after completion; The pressure impregnation process is as follows: First, the impregnation pressure is adjusted to 5-20MPa and the impregnation rate is 1-10mm / s; after aluminum liquid seeps out from the bottom of the preform, the impregnation pressure is adjusted to 20-60MPa, and the pressure is maintained for 1-8 minutes after reaching the pressure. Fourth, the composite material undergoes deformation treatment and heat treatment, thus completing the process.

2. The method for preparing lightweight, high-stiffness heterogeneous aluminum-based composite materials according to claim 1, characterized in that: The volume fraction of aluminum-lithium alloy powder in the raw materials mentioned in step one is 30-80%.

3. The method for preparing lightweight, high-stiffness heterogeneous aluminum-based composite materials according to claim 1, characterized in that: The aluminum-lithium alloy powder mentioned in step one has a particle size of 1-200 μm and a Li content of 0.5-10 wt.%.

4. The method for preparing the lightweight, high-stiffness heterogeneous aluminum-based composite material according to claim 1, characterized in that: The aluminum matrix mentioned in step one is pure aluminum or an aluminum alloy; the aluminum alloy is one or a combination of several of the following: Al-Si alloy, Al-Si-Cu alloy, Al-Cu alloy, Al-Cu-Mg alloy, Al-Cu-Mg-Si alloy, Al-Ag alloy, Al-RE alloy, Al-Zn-Cu alloy, Al-Zn-Mg-Cu alloy, Al-Mg alloy, and Al-Mn alloy.

5. The method for preparing lightweight, high-stiffness heterogeneous aluminum-based composite materials according to claim 1, characterized in that: The cold pressing process described in step two is as follows: compression speed is 0.1-3 mm / min, pressure is 5-70 MPa, and holding time is 10-20 min.

6. The method for preparing lightweight, high-stiffness heterogeneous aluminum-based composite materials according to claim 1, characterized in that: The heating rate of the preform and mold in step three is 5-20℃ / min, the preheating temperature is 20-60℃ lower than the melting point of aluminum-lithium alloy powder, and the holding time is 1-3h.

7. The method for preparing lightweight, high-stiffness heterogeneous aluminum-based composite materials according to claim 1, characterized in that: In step three, the aluminum substrate is melted and heated to 200-280°C above the melting point of the aluminum substrate.

8. The method for preparing lightweight, high-stiffness heterogeneous aluminum-based composite materials according to claim 1, characterized in that: The deformation treatment described in step four is extrusion or rolling.

9. The method for preparing lightweight, high-stiffness heterogeneous aluminum-based composite materials according to claim 8, characterized in that: The extrusion ratio in step four is 8-18:1; the cumulative reduction in rolling is 70-99%.

10. The method for preparing the lightweight, high-stiffness heterogeneous aluminum-based composite material according to claim 1, characterized in that: The heat treatment described in step four is one or a combination of several of the following: annealing, solution treatment, quenching, pre-aging, single-stage aging, double-stage aging, and multi-stage aging.

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