High-strength aluminum alloy containing ceramic particles and preparation method

Abstract

The invention discloses a high-strength aluminum alloy containing ceramic particles and a preparation method of the high-strength aluminum alloy. Ceramic reinforced phase particles and Al-Zn-Mg-Cu series aluminum alloy powder are subjected to blending and ball milling, and homogenized mixed powder is prepared; placing the uniformly mixed powder in a mold for pre-pressing, keeping for a period of time, and then taking out to obtain a blank; the blank is subjected to hot extrusion and air cooling to the room temperature, and a bar is obtained; and the bar is subjected to two-stage solution treatment and artificial aging treatment, and finally air cooling is conducted to the room temperature. The selected Al-Zn-Mg-Cu series aluminum alloy powder contains Zr and Sc elements and has a remarkable grain refining effect, and the strength, plasticity and other comprehensive mechanical properties of the base material are high; the high-strength aluminum alloy powder is mechanically mixed with BN and B4C powder, so that reinforced phase particles are distributed more uniformly, and the interface bonding rate is increased; after hot extrusion, the intergranular micron-sized reinforcement can effectively reduce the grain boundary energy, improve the grain boundary stability and binding force, play a pinning role and improve the deformation resistance.

Description

Technical Field

[0001] The invention relates to a high-strength aluminum alloy containing ceramic particles and a preparation method thereof. Background Art

[0002] Ultra-high-strength aluminum alloys are considered to be ideal materials for replacing titanium alloys or steel used below 310°C in the aviation and aerospace fields to achieve weight reduction and cost reduction, and their research and application are highly valued. Composites can further improve the comprehensive mechanical properties of materials and are an important method to achieve light weight and high strength. In recent years, ceramic-reinforced metal matrix composites (MMCs) have received widespread attention. For example, ceramic reinforcements such as oxides, carbides, nitrides, and borides are used to improve the strength, wear resistance, thermal conductivity and other properties of materials.

[0003] The production of high-strength aluminum-based composite materials using traditional casting, forging and other methods may cause uneven element distribution, segregation and agglomeration, many metallurgical defects, easy cracking, and large material waste. During the extrusion process of high-strength aluminum-based composite materials, due to the high material strength, it is easy to cause mold wear, which directly affects the dimensional accuracy and surface quality of the product. At the same time, due to the low plasticity, it is easy to crack, so the process control is more difficult. The use of traditional powder metallurgy technology requires powder making, compaction, sintering (including hot isostatic pressing, cold isostatic pressing, etc.), forging and finishing processes. The process is complicated, the aluminum alloy powder is severely oxidized, the product size is limited, and the cost is high, which limits its promotion and application.

[0004] Compared with the traditional powder metallurgy method, the powder hot extrusion method does not require sintering, the process is simpler, and the extruded alloy has the advantages of small grain size, uniform structure, and small component segregation. Compared with conventional casting-hot extrusion, the extrusion force required for powder hot extrusion is smaller, and the extrusion temperature and extrusion ratio range that can be used are wider. However, there are currently few studies on hot extrusion of high-strength aluminum alloy powders containing ceramic particles, and there is a lack of related process methods. Summary of the invention

[0005] The present invention provides a high-strength aluminum alloy containing ceramic particles and a preparation method in order to solve the problems existing in the above-mentioned prior art. The present invention can be used to prepare ceramic-reinforced aluminum-based composite material profiles with ultra-high strength and good strength-toughness matching.

[0006] The technical solutions adopted in the present invention are:

[0007] A method for preparing a high-strength aluminum alloy containing ceramic particles comprises the following steps:

[0008] (1) blending ceramic reinforcement phase particles with Al-Zn-Mg-Cu aluminum alloy powder by ball milling to prepare a homogenized mixed powder;

[0009] (2) placing the uniformly mixed powder in a mold for pre-pressing, and taking it out after keeping it for a period of time to obtain a blank;

[0010] (3) hot extruding the blank and air cooling it to room temperature to obtain a rod;

[0011] (4) The rod is subjected to a double-stage solution treatment and an artificial aging treatment, and finally air-cooled to room temperature.

[0012] Furthermore, the Al-Zn-Mg-Cu aluminum alloy powder is produced by gas atomization method and is composed of the following elements:

[0013] Zn: 6.0%~8.5%, Mg: 1.8%~3.2%, Cu: 1.0%~2.5%, Zr: 0.10%~0.25%, Sc: 0.10%~0.25%, and the rest are Al and unremovable impurity elements.

[0014] Furthermore, the Al-Zn-Mg-Cu aluminum alloy powder has a particle size of less than 70 μm, an average particle size of 32 to 36 μm, and a median particle size of 28 to 31 μm.

[0015] Furthermore, the ceramic reinforcement phase particles are BN particles and B4C particles, and in terms of mass percentage, the total addition amount of the two particles accounts for between 5% and 15% of the total mass.

[0016] Furthermore, the median particle size of the BN particles is 3-4 μm, the median particle size of the B4C particles is 1.5-2 μm, and the purity of the BN particles and the B4C particles is above 99.5%.

[0017] Furthermore, during the blending and ball milling in step (1), 0.5% to 1% of stearic acid is added.

[0018] Furthermore, in step (1), the ball-to-material ratio is 3-7:1, the rotation speed is 250-400 rpm, and the ball milling time is 0.5-2 h, thereby obtaining a high-strength aluminum alloy mixed powder containing BN and B4C ceramic particles.

[0019] Furthermore, step (2) uses vacuum short-time hot prepressing, and the chamber vacuum degree is 1×10 -2 Pa, pre-pressing temperature 350~400℃, pressure 10~20MPa; time 10~20min.

[0020] Furthermore, the extrusion ratio of step (3) is 15-30:1, the extrusion temperature is 450-550°C, and the extrusion speed is 1-2 mm / s.

[0021] Furthermore, in the two-stage solution treatment process of step (4), the first-stage solution temperature is 410-450°C, and the time is 1-2 hours; the second-stage solution temperature is 460-490°C, and the time is 1-2 hours, and then the test rod is quickly quenched into water.

[0022] Furthermore, in step (4), the treatment temperature of the artificial aging treatment is 120 to 160° C., and the time is 6 to 24 hours.

[0023] The invention also discloses a high-strength aluminum alloy prepared by the preparation method.

[0024] The present invention has the following beneficial effects:

[0025] 1) The selected Al-Zn-Mg-Cu aluminum alloy powder contains Zr and Sc elements, which has a significant grain refinement effect, and the comprehensive mechanical properties of the substrate, such as strength and plasticity, are high; the high-strength aluminum alloy powder is mechanically mixed with BN and B4C powders by ball milling, which can make the distribution of reinforcement phase particles more uniform and improve the interface bonding rate; after hot extrusion, the intergranular micron-level reinforcement can effectively reduce the grain boundary energy, improve the grain boundary stability and bonding force, play a pinning role, and improve the deformation resistance.

[0026] 2) Different from the traditional method of cold pressing powder into a blank followed by hot extrusion and the method of hot extrusion by encapsulation, the present invention adopts vacuum short-time hot pre-pressing to form a blank, which requires small pressure and does not require encapsulation. The blank is then directly extruded to achieve complete metallurgical bonding. The process is short and efficient. The prepared aluminum-based composite material has the advantages of refined grains, uniform distribution of the second phase, high density and high strength.

[0027] 3) The use of two-stage solution treatment can make the solid solution elements dissolve into the matrix more fully and controllably, improve the strength and toughness of the alloy, promote the precipitation of Al3 (Zr / Sc) phase, provide grain boundary strengthening and precipitation strengthening, and inhibit recrystallization during subsequent heat treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a flow chart of the present invention.

[0029] Figure 2 This is a microscopic morphology of the powder particles after ball milling in Example 1 of the present invention.

[0030] Figure 3 This is the microstructure diagram of the extruded state of Example 1 of the present invention. DETAILED DESCRIPTION

[0031] The present invention will be further described below in conjunction with the accompanying drawings.

[0032] Example 1

[0033] The raw material used is spherical Al-Zn-Mg-Cu aluminum alloy powder produced by gas atomization method. According to the mass percentage of elements, the powder contains: 6.0% Zn, 3.0% Mg, 2.5% Cu, 0.25% Zr, 0.25% Sc, and the rest is Al and impurity elements that cannot be removed. The powder particle size is less than 70μm, the average particle size is 33.6μm, and the median particle size is 29.2μm.

[0034] A planetary ball mill was used to add 3% BN, 3% B4C powder and aluminum alloy powder, 0.5% stearic acid, a ball-to-material ratio of 3:1, a rotation speed of 300 r / pm, and a ball milling time of 0.5 h to obtain a high-strength aluminum alloy mixed powder containing BN and B4C ceramic particles, such as Figure 2 As shown;

[0035] The mixed powder was placed in a high-purity graphite mold and pre-pressed in a vacuum hot press. The vacuum degree of the chamber was 1×10 - 2 Pa, temperature 350℃, pressure 20MPa, time 20min, and a billet with a density of about 90% was obtained;

[0036] The blank was placed in a hot press, heated to 550°C, extruded into a rod at an extrusion ratio of 27:1 and an extrusion speed of 1.5 mm / s, and cooled to room temperature in air;

[0037] The microstructure of the sample after extrusion is as follows Figure 3 The bars were solution treated at 410℃ / 2h+475℃ / 1.5h, then immediately quenched with room temperature water, followed by aging treatment at 160℃ for 6h, and then air cooled to room temperature.

[0038] Example 2

[0039] The raw material used is a spherical Al-Zn-Mg-Cu aluminum alloy powder produced by gas atomization. According to the mass percentage of the elements, the powder contains: 7.3% Zn, 2.4% Mg, 1.8% Cu, 0.15% Zr, 0.15% Sc, and the rest is Al and impurity elements that cannot be removed. The powder particle size is less than 70μm, the average particle size is 33.6μm, and the median particle size is 29.2μm;

[0040] A planetary ball mill was used to add 5% BN, 5% B4C powder and aluminum alloy powder, 0.5% stearic acid, a ball-to-material ratio of 7:1, a rotation speed of 250 rpm, and a ball milling time of 2 h to obtain a high-strength aluminum alloy mixed powder containing BN and B4C ceramic particles;

[0041] The mixed powder was placed in a high-purity graphite mold and pre-pressed in a vacuum hot press. The vacuum degree of the chamber was 1×10- 2 Pa, temperature 380℃, pressure 15MPa; time 15min, obtain a billet with a density of about 90%;

[0042] The blank was placed in a hot pressing device, heated to 500°C, extruded into a rod at an extrusion ratio of 20:1 and an extrusion speed of 2 mm / s, and cooled to room temperature in air;

[0043] The bars were solution treated at 430°C / 2h+460°C / 2h, then immediately quenched with room temperature water, followed by aging treatment at 140°C for 12h, and then air cooled to room temperature.

[0044] Example 3

[0045] The raw material used is a spherical Al-Zn-Mg-Cu aluminum alloy powder produced by gas atomization. According to the mass percentage of the elements, the powder contains: 8.5% Zn, 2.0% Mg, 1.2% Cu, 0.15% Zr, 0.10% Sc, and the rest is Al and impurity elements that cannot be removed. The powder particle size is less than 70μm, the average particle size is 33.6μm, and the median particle size is 29.2μm;

[0046] A planetary ball mill was used to add 7% BN, 7% B4C powder and aluminum alloy powder, 1% stearic acid, a ball-to-material ratio of 7:1, a rotation speed of 400 rpm, and a ball milling time of 1.5 h to obtain a high-strength aluminum alloy mixed powder containing BN and B4C ceramic particles;

[0047] The mixed powder was placed in a high-purity graphite mold and pre-pressed in a vacuum hot press. The vacuum degree of the chamber was 1×10 - 2 Pa, temperature 400℃, pressure 10MPa; time 10min, obtain a billet with a density of about 90%;

[0048] The blank was placed in a hot press, heated to 450°C, extruded into a rod at an extrusion ratio of 15:1 and an extrusion speed of 1 mm / s, and cooled to room temperature in air;

[0049] The test bars were solution treated at 450°C / 1h+490°C / 1h, then immediately quenched with room temperature water, followed by aging treatment at 120°C for 24h, and then air cooled to room temperature.

[0050] According to the national standard, the high-strength aluminum alloy materials containing ceramic particles prepared in Examples 1 to 3 were used to prepare tensile specimens by wire cutting, and room temperature tensile tests were carried out. The tensile properties of the aluminum alloys prepared in Examples 1 to 3 are shown in Table 1.

[0051] Table 1 Room temperature tensile properties

[0052] Example Yield strength(MPa) Tensile strength(MPa) Elongation(%) Example 1 586 673 13.1 Example 2 625 718 11.3 Example 3 668 751 9.7

[0053] The above description is only a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several improvements without departing from the principle of the present invention, and these improvements should also be regarded as within the protection scope of the present invention.

Claims

1. A method for preparing a high-strength aluminum alloy containing ceramic particles, characterized in that: The steps include: (1) ball-milling the ceramic reinforcement phase particles and Al-Zn-Mg-Cu aluminum alloy powder to prepare a homogenized mixed powder; (2) placing the uniformly mixed powder in a mold for pre-pressing, and taking it out after keeping it for a period of time to obtain a blank; (3) hot extruding the billet and air cooling it to room temperature to obtain a rod; (4) The rod is subjected to double-stage solution treatment and artificial aging treatment, and finally air-cooled to room temperature.

2. The method for preparing a high-strength aluminum alloy containing ceramic particles according to claim 1, characterized in that: The Al-Zn-Mg-Cu aluminum alloy powder is produced by gas atomization method and is composed of the following elements: Zn: 6.0%~8.5%, Mg: 1.8% ~3.2%, Cu: 1.0%~2.5%, Zr: 0.10%~0.25%, Sc: 0.10%~0.25%, and the rest are Al and non-removable impurity elements.

3. The method for preparing a high-strength aluminum alloy containing ceramic particles according to claim 2, characterized in that: The Al-Zn-Mg-Cu aluminum alloy powder has a particle size of less than 70 μm, an average particle size of 32 to 36 μm, and a median particle size of 28 to 31 μm.

4. The method for preparing a high-strength aluminum alloy containing ceramic particles according to claim 1, characterized in that: The ceramic reinforcement phase particles are BN particles and B4C particles. In terms of mass percentage, the total addition amount of the two particles accounts for between 5% and 15% of the total mass.

5. The method for preparing a high-strength aluminum alloy containing ceramic particles according to claim 4, characterized in that: The median particle size of the BN particles is 3-4 μm, the median particle size of the B4C particles is 1.5-2 μm, and the purity of the BN particles and the B4C particles is above 99.5%.

6. The method for preparing a high-strength aluminum alloy containing ceramic particles according to claim 1, characterized in that: In step (1), 0.5% to 1% of stearic acid is added during the blending ball milling.

7. The method for preparing a high-strength aluminum alloy containing ceramic particles according to claim 1, characterized in that: Step (2) Use vacuum short-time hot prepressing, the chamber vacuum degree is 1×10 −2 Pa, pre-pressing temperature 350~400℃, pressure 10~20MPa; time 10~20min.

8. The method for preparing a high-strength aluminum alloy containing ceramic particles according to claim 1, characterized in that: In the two-stage solution treatment process of step (4), the first-stage solution temperature is 410-450°C for 1-2 hours; the second-stage solution temperature is 460-490°C for 1-2 hours, and then the test rod is quickly quenched into water.

9. The method for preparing a high-strength aluminum alloy containing ceramic particles according to claim 1, characterized in that: In step (4), the treatment temperature of artificial aging treatment is 120-160°C and the time is 6-24h.

10. A high-strength aluminum alloy prepared by the preparation method according to any one of claims 1 to 9.

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