High-temperature-resistant super-structured aluminum alloy and preparation method thereof

Abstract

The application discloses a kind of high-temperature-resistant superstructure aluminum alloy and preparation method thereof, preparation process is: a certain amount of aluminum powder or aluminum alloy powder is weighed, a certain amount of boehmite and process control agent is added, the three are fully mixed and then ball milled;The obtained composite powder is loaded into a special mold and cold-pressed, then pressure sintering is carried out;After sintering is completed, it is cooled in the furnace to obtain the required superstructure aluminum alloy;The prepared high-temperature-resistant superstructure aluminum alloy contains in-situ generated nano Al-O amorphous structure and nano Al-O solid solution structure, and precipitated acicular nano Al2O3 structure.The application realizes the dispersion of a large number of oxygen atoms in the aluminum alloy powder, the uniform dispersion of high-density nano-strengthening phase;A variety of strengthening phases are formed in the aluminum alloy, and better synergistic strengthening effect is obtained;High-temperature strength is greatly improved, and service temperature can exceed 350 DEG C.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of high-performance aluminum alloy materials, and particularly relates to a high-temperature-resistant super-structured aluminum alloy and a preparation method thereof. BACKGROUND

[0002] With the development of cutting-edge technology, there are increasingly high requirements for light-weight metal materials resistant to high temperature. Traditional heat-resistant aluminum alloys have been unable to meet the actual needs of industrial applications due to insufficient high-temperature strength. The currently developed high-temperature-resistant aluminum alloys mainly improve the high-temperature performance of the materials by adding rare earth elements to form high-temperature-resistant precipitates, which has high raw material costs and complex heat treatment processes, limiting the industrial application of high-temperature-resistant aluminum alloys. Moreover, the precipitates containing rare earth elements have insufficient high-temperature stability above 350℃, making it difficult for the service temperature of the high-temperature-resistant aluminum alloys to exceed 350℃. Ceramic materials have high melting points and excellent high-temperature mechanical properties, and are ideal strengthening phases for improving the high-temperature mechanical properties of aluminum alloys.

[0003] Traditional processes generally add micron or nanometer SiC, B4C, Al2O3, carbon nanotubes, and graphene, etc. ceramic phases to the aluminum alloy melt by stirring or mix the ceramic powder with the aluminum alloy powder by powder metallurgy to prepare aluminum matrix composites, obtaining certain high-temperature mechanical properties. However, the aluminum matrix composites prepared by this external method have poor plasticity and toughness due to the easy agglomeration of particles, making the processing difficult, and the service temperature is limited by the aluminum alloy matrix, which is also difficult to achieve a high service temperature.

[0004] In recent years, a large number of research works have attempted to use in-situ generated particulate TiB2, TiC, Ti3AlC2, Al4C3, AlN, and Al2O3, etc. ceramic phases to strengthen aluminum alloys and improve the high-temperature performance of aluminum alloys. For example, the invention patent “Preparation method of multi-element nano-composite reinforced heat-resistant aluminum matrix composite material” discloses a method of converting the precursor in the nano-carbon into nano-oxide by heat reaction treatment, thereby obtaining a nano-carbon and nano-oxide composite reinforced heat-resistant aluminum matrix composite material. The invention patent “Nano-AlN particle reinforced mixed crystal heat-resistant aluminum matrix composite material and preparation method” discloses a method of using magnesium nitride and aluminum as raw materials to generate in-situ AlN nano-enhanced particles in the sintering process to prepare a heat-resistant aluminum matrix composite material. The above-mentioned in-situ generated ceramic phases are generated by chemical reaction between the added raw materials and the aluminum alloy powder on the surface, and the ceramic phases are mainly in the form of particles, with a low volume fraction in the composite material, and most of them are located at the grain boundaries, which has insufficient hindering effect on the intragranular plastic deformation of the aluminum alloy matrix. SUMMARY

[0005] In order to overcome the problem of insufficient high-temperature strength of existing aluminum alloy materials, the present application provides a high-temperature-resistant super-structured aluminum alloy and a preparation method thereof.

[0006] The application discloses a preparation method of a high-temperature-resistant super-structured aluminum alloy.

[0007] Step 1: a certain amount of aluminum powder or aluminum alloy powder is weighed, a certain amount of boehmite and a process control agent are added, and the three are fully mixed and then ball milled.

[0008] Step 2: the composite powder obtained in step 1 is loaded into a special mold and cold-pressed to form, and then pressure sintering is performed; after sintering is completed, the furnace is cooled to obtain the required super-structured aluminum alloy; during pressure sintering, the sintering temperature is 580-660 DEG C, a unidirectional load of 10-300 MPa is applied during the sintering process, and the holding time is 15-120 min.

[0009] Further, the ball milling is performed in a planetary ball mill, a full-range ball mill, a stirring ball mill or a swing ball mill, so that the boehmite and the aluminum powder or aluminum alloy powder are fully reacted, and the oxygen atoms in the boehmite are solid-solved into the aluminum powder or aluminum alloy powder.

[0010] Further, the mass ratio of the boehmite to the aluminum powder or aluminum alloy powder in step 1 is 0.5-20:100.

[0011] Further, the process control agent in step 1 is one or more of methanol, ethanol, isopropyl alcohol, tert-butyl alcohol, ethylene glycol, stearic acid or glycerol, and the mass fraction of the added process control agent is less than 5%.

[0012] Further, a vacuum, a closed air or argon atmosphere protection is adopted during the ball milling process in step 1, so as to prevent the surface of the aluminum powder or aluminum alloy powder from being excessively oxidized.

[0013] The high-temperature-resistant super-structured aluminum alloy prepared by the preparation method of the high-temperature-resistant super-structured aluminum alloy contains in-situ generated nano Al-O amorphous structures and nano Al-O solid solution structures, and precipitated needle-shaped nano Al2O3 structures.

[0014] Further, the in-situ generated nano Al-O amorphous structures, the nano Al-O solid solution structures and the needle-shaped nano Al2O3 structures are uniformly distributed in the interior of the matrix grains or at the grain boundaries, and can also be located in the interiors of two grains.

[0015] Further, the in-situ generated nano Al-O amorphous structures, the nano Al-O solid solution structures and the needle-shaped nano Al2O3 structures have excellent high-temperature stability, and can still maintain structural stability after long-time high-temperature heat treatment at 600 DEG C.

[0016] The application has the following beneficial technical effects:

[0017] (1) The application uses solid boehmite as an oxygen source, so that a large amount of oxygen atoms can be better dispersed in the aluminum alloy powder.

[0018] (2) The present application realizes the uniform dispersion of high-density nano-strengthening phase by high-energy ball milling to make oxygen atoms in a non-equilibrium state to be dissolved in aluminum alloy, and then forming nano-amorphous structure and solid solution structure in the subsequent pressure sintering process, and part of which is uniformly precipitated from the aluminum alloy to form nano-needle-shaped Al2O3 structure.

[0019] (3) The present application forms nano-Al-O amorphous structure, nano-Al-O solid solution structure and nano-needle-shaped Al2O3 structure and other strengthening phases in the aluminum alloy, which has better synergistic strengthening effect.

[0020] 4) The nano-Al-O amorphous structure, nano-Al-O solid solution structure and nano-needle-shaped Al2O3 structure formed by the present application greatly improve the high-temperature strength of aluminum matrix composite materials, and the service temperature can exceed 350℃. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 TEM diagram of the high-temperature resistant super-structured aluminum alloy material prepared in Example 1 of the present application (wherein a is nano-Al-O amorphous structure, b is nano-Al-O solid solution structure, and c is nano-needle-shaped Al2O3 structure).

[0022] Figure 2 EDS spectrum of the high-temperature resistant super-structured aluminum alloy material prepared in Example 1 of the present application.

[0023] Figure 3 Quasi-static compression mechanical property test results of the high-temperature resistant super-structured aluminum alloy material prepared in Example 1 of the present application at different temperatures. DETAILED DESCRIPTION

[0024] The present application will be further described in detail below in combination with the drawings and specific examples.

[0025] The present application is a preparation method of a high-temperature resistant super-structured aluminum alloy, comprising the following steps:

[0026] Step 1: Weigh aluminum powder or industrial aluminum alloy powder, add a certain amount of boehmite and ball milling process control agent and ball mill;

[0027] Pure aluminum powder or industrial aluminum alloy powder is selected as raw material, and the particle size and shape of the pure aluminum powder or industrial aluminum alloy powder are not limited.

[0028] The weighed pure aluminum powder or industrial aluminum alloy powder and boehmite are added into a ball mill tank, and 1-5% of a process control agent is added, which can be selected from methanol, ethanol, isopropyl alcohol, tert-butyl alcohol, ethylene glycol, stearic acid and glycerol. The process control agent inhibits the cold welding between the metal powders during the ball milling process, which is beneficial to the grain refinement. The boehmite as the O source reacts with aluminum in situ to generate a strong phase of Al-O structure.

[0029] The ball mill tank is protected by airtight air or argon atmosphere. The ball milling is performed by using a planetary ball mill, a omnidirectional ball mill, a stirring ball mill or a swing ball mill, etc. The ball milling time is 5-50 h, the ball-to-material ratio is 5-50:1, and the rotation speed is 100-500 rpm, so that the process control agent and the boehmite are uniformly dispersed on the surface of the refined powder.

[0030] Step 2: The mixed powder after the ball milling in step 1 is cold-pressed into a shape, and then pressure sintering is performed. After the sintering is completed, the furnace is cooled to obtain the required aluminum-based composite material.

[0031] The pressure sintering is performed at a sintering temperature of 580-640℃, a load of 10-300 MPa during the sintering process, and a holding time of 15-120 min.

[0032] The sintering is performed by using a vacuum hot-pressing sintering furnace, a hot isostatic pressing sintering furnace or a vibration pressure sintering furnace.

[0033] The in-situ generated nano Al-O amorphous structure, nano Al-O solid solution structure and needle-shaped nano Al2O3 structure are uniformly distributed in the matrix material, and can still maintain structural stability after long-term high-temperature heat treatment at 600℃.

[0034] The prepared high-temperature-resistant super-structured aluminum alloy material has excellent high-temperature mechanical properties, and the service temperature can be higher than 350℃.

[0035] Example 1:

[0036] The high-temperature-resistant super-structured aluminum alloy is prepared according to the following steps:

[0037] Step 1: The aluminum powder with a purity of 99.9% is selected as the raw material, and is loaded into a ball mill tank under the protection of argon atmosphere in a glove box. 5% of anhydrous ethanol is added as a dispersant, and 5% of boehmite is added as an O source. The above mixture is ball milled on a planetary ball mill for 30 h at a rotation speed of 210 rpm and a ball-to-material ratio of 25:1, so that it is uniformly dispersed on the surface of the refined aluminum powder and is solid-solved.

[0038] Step 2: The composite powder obtained in step 1 is loaded into a mold and cold-pressed, and then the sample is sintered in a vacuum hot-press sintering furnace, the sintering temperature is 620 DEG C, the load is 50 MPa, and the sample is cooled to room temperature in the furnace after holding for 30 min.

[0039] Figure 1 The TEM image of the sample of the present embodiment is shown in FIG. 1. Figure 1 As can be seen from FIG. 1, the high-temperature-resistant super-structured aluminum alloy composite prepared by the present application contains various strengthening phases, including nano-Al-O amorphous structure, nano-Al-O solid solution structure and needle-shaped nano-Al2O3 structure.

[0040] Figure 2 The EDS spectrum of the high-temperature-resistant super-structured aluminum alloy composite prepared in the present embodiment is shown in FIG. 2. Figure 2 As can be seen from FIG. 2, O elements are enriched in the local area, which is consistent with the morphology and size of the nano-Al-O amorphous structure, nano-Al-O solid solution structure and needle-shaped nano-Al2O3 structure.

[0041] Figure 3 The quasi-static mechanical property test results of the high-temperature-resistant super-structured aluminum alloy composite prepared in the present embodiment at different temperatures are shown in FIG. 3. Figure 3 As can be seen from FIG. 3, by introducing O elements from boehmite into the aluminum matrix, the room temperature strength of the aluminum matrix composite reaches 600 MPa, and the material still has a high temperature strength of 200 MPa at 500 DEG C.

[0042] Embodiment 2

[0043] The high-temperature-resistant super-structured aluminum alloy is prepared according to the following steps:

[0044] Step 1: Aluminum powder with a purity of 99.9% is selected as a raw material, and is loaded into a ball milling tank under the protection of argon gas in a glove box, and 1.5% of stearic acid by mass fraction is added as a dispersant; 10% of boehmite by mass fraction. The above mixture is ball milled on a planetary ball mill for 40 h at a speed of 280 rpm, and the ball-to-material ratio is 15:1, so that it is uniformly dispersed on the surface of the refined aluminum powder and is solid-solved.

[0045] Step 2: The composite powder obtained in step 1 is loaded into a mold and cold-pressed, and then the sample is sintered in a vacuum hot-press sintering furnace, the sintering temperature is 620 DEG C, the load is 50 MPa, and the sample is cooled to room temperature in the furnace after holding for 30 min.

[0046] Embodiment 3

[0047] The high-temperature-resistant super-structured aluminum alloy is prepared according to the following steps:

[0048] Step 1: ZL114A aluminum alloy powder is selected as raw material, and is loaded into a ball mill tank under the protection of argon atmosphere in a glove box, and 5% of anhydrous ethanol by mass fraction is added as a dispersant; 2% of boehmite by mass fraction is added as an O source. The above mixture is ball milled on a planetary ball mill for 30 h at a speed of 240 rpm, and the ball-to-material ratio is 20:1, so that the mixture is uniformly dispersed on the surface of the refined aluminum alloy powder and is solid-solved.

[0049] Step 2: The composite powder obtained in step 1 is loaded into a mold and cold-pressed, and is sintered in a vibration sintering furnace, the sintering temperature is 580 DEG C, the loaded pressure is 50 MPa, and the holding time is 30 min, and the furnace is cooled to room temperature, so that the sample is obtained.

[0050] Example 4

[0051] A high-temperature-resistant super-structured aluminum alloy is prepared according to the following steps:

[0052] Step 1: 7075 aluminum alloy powder is selected as raw material, and is loaded into a ball mill tank under the protection of argon atmosphere in a glove box, and 1.5% of stearic acid by mass fraction is added as a dispersant; 2% of boehmite by mass fraction is added as an O source. The above mixture is ball milled on a planetary ball mill for 30 h at a speed of 180 rpm, and the ball-to-material ratio is 25:1, so that the mixture is uniformly dispersed on the surface of the refined aluminum alloy powder and is solid-solved.

[0053] Step 2: The composite powder obtained in step 1 is loaded into a mold and cold-pressed, and is sintered in a vacuum hot-pressing sintering furnace, the sintering temperature is 580 DEG C, the loaded pressure is 30 MPa, and the holding time is 30 min, and the furnace is cooled to room temperature, so that the sample is obtained.

[0054] The high-temperature-resistant super-structured aluminum alloy composite material prepared in the above examples of the application has a greatly improved high-temperature strength, and the service temperature can be higher than 350 DEG C.

[0055] Different from the conventional in-situ growth method, the application combines high-energy ball milling and hot-pressing sintering process, realizes the solid solution of oxygen atoms through the reaction of boehmite and aluminum matrix, instead of directly reacting on the surface to form Al2O3 particles, and obtains in-situ generated nano Al-O amorphous structure, nano Al-O solid solution structure and needle-shaped nano Al2O3 structure after subsequent sintering. They are dispersedly distributed in the aluminum matrix and form good interface bonding, and the synergistic strengthening of multiple strengthening phases greatly improves the strength of the aluminum matrix composite material at high temperature.

Claims

1. A method for preparing a high-temperature resistant metamorphic aluminum alloy, characterized in that, Includes the following steps: Step 1: Weigh a certain amount of aluminum powder or aluminum alloy powder, add a certain amount of boehmite and process control agent, mix the three thoroughly and then ball mill them; The ball milling method is planetary ball milling, omnidirectional ball milling, stirring ball milling or oscillating ball milling; the ball milling time is 5 to 50 hours, the ball-to-material ratio is 5 to 50:1, and the rotation speed is 100 to 500 rpm; The ratio of the mass of boehmite to the mass of aluminum powder or aluminum alloy powder is 0.5~20:100; Step 2: The composite powder obtained in Step 1 is loaded into a special mold and cold-pressed, and then pressure sintered; after sintering, it is cooled in the furnace to obtain the desired superstructure aluminum alloy; during pressure sintering, the sintering temperature is 580~660 ℃, and a unidirectional load of 10~300MPa is applied simultaneously during the sintering process, with a holding time of 15-120 min.

2. The method for preparing a high-temperature resistant metamorphic aluminum alloy according to claim 1, characterized in that, In step 1, the process control agent is one or more of methanol, ethanol, isopropanol, tert-butanol, ethylene glycol, stearic acid, or glycerol, and the mass fraction of the added process control agent is less than 5%.

3. The method for preparing a high-temperature resistant metamorphic aluminum alloy according to claim 1, characterized in that, In step 1, the ball milling process is protected by a vacuum, sealed air, or argon atmosphere.

4. The high-temperature resistant metamorphic aluminum alloy prepared by the method for preparing high-temperature resistant metamorphic aluminum alloys according to any one of claims 1-3, characterized in that, The high-temperature resistant metamorphic aluminum alloy contains in-situ generated nano-Al-O amorphous structure and nano-Al-O solid solution structure, as well as precipitated needle-like nano-Al2O3 structure.

5. The high-temperature resistant metamorphic aluminum alloy according to claim 4, characterized in that, The in-situ generated nano-Al-O amorphous structures, nano-Al-O solid solution structures, and needle-like nano-Al2O3 structures are uniformly distributed inside the matrix grains or at the grain boundaries, and may also be located inside two grains simultaneously.

6. The high-temperature resistant metamorphic aluminum alloy according to claim 4, characterized in that, The in-situ generated nano-Al-O amorphous structure, nano-Al-O solid solution structure, and needle-like nano-Al2O3 structure exhibit excellent high-temperature stability and can maintain structural stability even after long-term high-temperature heat treatment at 600 ℃.

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