CN111041297A

CN111041297A - A kind of high corrosion resistance in-situ nanoparticle reinforced aluminum matrix composite material and preparation method

Info

Publication number: CN111041297A
Application number: CN201911298187.7A
Authority: CN
Inventors: 赵玉涛; 毛磊; 靳利伟; 黄璐瑶; 高旭
Original assignee: Jiangsu University
Current assignee: Jiangsu University
Priority date: 2019-12-17
Filing date: 2019-12-17
Publication date: 2020-04-21

Abstract

The invention relates to the technical field of preparation of aluminum-based composite materials, in particular to an in-situ nanoparticle-reinforced aluminum-based composite material with high corrosion resistance and a preparation method. _The invention adopts the synergistic effect of the melt reaction method and the helical high-frequency external magnetic field. Obstructing the path of corrosion microcurrent can also reduce the continuity of the Mg ₂ Si phase generated at the grain boundary, thus providing a guarantee for improving the corrosion resistance of the material.

Description

High-corrosion-resistance in-situ nanoparticle reinforced aluminum-based composite material and preparation method thereof

Technical Field

The invention relates to the technical field of preparation of aluminum-based composite materials, in particular to a high-corrosion-resistance in-situ nanoparticle reinforced aluminum-based composite material and a preparation method thereof.

Background

6XXX series aluminum alloys are currently used in the worldThe sheet metal part material is most widely applied in the transportation industry. Among them, Al — Mg — Si aluminum alloys represented by AA6061 are drawing attention because of their excellent formability, mechanical properties of medium and high strength, good weldability, and corrosion resistance. Mg and Si are main alloying elements of AA6061 aluminum alloy, and the two elements can form a large amount of Mg in the alloy under the synergistic action₂The Si strengthening phase can greatly improve various performances of the 6XXX series aluminum alloy after solution aging treatment. But Mg₂The existence of the Si strengthening phase also restricts the further improvement of the corrosion resistance of the AA6061 aluminum alloy material to a certain degree. In corrosive environments, Mg₂A path for corroding micro-current can be formed between the Si and the Al crystal grains, so that the corrosion phenomenon is aggravated, and the material cannot meet the requirements of the service environment and fails. According to statistics, about 3.4% of total domestic product (GDP) is corroded and consumed every year all over the world, and the corrosion rate is up to 5% in China, so that huge economic loss is caused. Worldwide accepted data indicate that the cost of corrosion is greater than the sum of the economic losses of all natural disasters (earthquakes, tsunamis, drought, flooding, etc.). The material in-situ compounding concept provides possibility for improving the corrosion resistance of the 6XXX aluminum alloy.

The advantages of preparing aluminum matrix composites by in situ synthesis techniques have become more prominent in practice. The reason is that the reinforcing body particles generated in the in-situ synthesis technology are directly nucleated and grown in the matrix, the reinforcing body particles are well combined with the matrix, the thermal stability is good, and the reinforcing body particles can be uniformly and finely dispersed in the matrix, which is difficult to realize by an exogenous method. In addition, the main process of the in-situ synthesis technology relies on a direct melt reaction method, and the process method can be flexibly combined with an electromagnetic field and an ultrasonic field, and most probably realizes intensive production with high efficiency and low cost at present. Chinese patent CN 102828056A discloses a preparation method of binary ceramic particle reinforced high-temperature wear-resistant aluminum alloy, which successfully realizes binary (ZrB)₂+Al₃Zr) particles improve the high-temperature wear resistance of the 2024 aluminum alloy, but the particle size of the particles generated by the method is difficult to reach the nanometer level, which is not beneficial to improving the corrosion resistance of the material. Chinese patent CN 109234561A discloses an in-situ nano-tubeThe preparation method of the rice-grain reinforced aluminum-based composite material realizes the binary (ZrB)₂+Al₂O₃) The particles are generated in situ, the particle size of the particles reaches the nanometer level, but the problems of low particle collection efficiency and more reaction wastes exist. At present, relevant patents of high-corrosion-resistance in-situ nanoparticle reinforced aluminum-based composite materials are rarely reported, so that a novel aluminum-based composite material with excellent corrosion resistance is developed and prepared on the basis of the original 6XXX series aluminum alloy, and the method has vital practical significance and engineering application value.

Disclosure of Invention

The invention aims to provide a high-corrosion-resistance in-situ nanoparticle reinforced aluminum-based composite material and a preparation method thereof, so as to adapt to increasingly severe service environments. The technical vacancy of the existing in-situ synthesis aluminum-based composite material in the aspect of improving the corrosion resistance of the material is filled. After the technical scheme is adopted, the corrosion resistance of the material is obviously improved, and the comprehensive mechanical property is excellent.

ZrB of the invention₂The AA6061 in-situ nanoparticle reinforced aluminum-based composite material adopts a melt reaction method and a spiral high-frequency external magnetic field for synergistic action, and the high-frequency magnetic field can effectively promote the nanoscale ZrB₂The in-situ nano particles are uniformly dispersed in the matrix, and the uniformly dispersed nano inorganic particles can not only obstruct the passage of corrosion micro current, but also reduce Mg generated at the grain boundary₂The continuity of the Si phase provides guarantee for improving the corrosion resistance of the material.

K selected by the invention₂ZrF₆-KBF₄Al in situ synthesis reaction system due to the presence of KBF₄The powder is easy to burn, so that K is further optimized₂ZrF₆、KBF₄The adding proportion and the mass ratio of the two industrial common salts are controlled to be 100: 106-₂The yield of the in-situ nano particles is high, and reaction waste is less. Meets the requirement of industrial production, and solves the problems that industrial waste salt is difficult to treat and is easy to pollute the environment.

The content of AA6061 is optimized, especially the composition range of Mg and Si is optimizedThe mass ratio of Mg to Si in the AA6061 matrix is controlled to be 1.5-1.72. This is because when Mg is in the matrix₂After the Si metal intermediate phase is generated, the sensitivity of the material to intergranular corrosion is improved by the excess Si phase. The existence of Cu in the matrix can reduce the corrosion resistance of the material, but the Cu is an alloying element essential for improving the plasticity of the material, so the content of the Cu is limited, and the content of the Cu is controlled to be 0.15-0.2%.

The T73 bipolar aging treatment process is designed, the first-stage solution quenching temperature is 550-; the artificial aging temperature is 180 ℃, and the artificial aging time is 8 h. ZrB finally obtained₂the/AA 6061 in-situ nanoparticle reinforced aluminum-based composite material has excellent corrosion resistance and comprehensive mechanical property.

The technical scheme adopted by the invention comprises the following specific steps:

(1) for industrial purity K₂ZrF₆、KBF₄And (3) carrying out crystallization water removal treatment on the two kinds of reaction salt powder. Industrial pure K₂ZrF₆、KBF₄The primary particle size distribution of the two reaction salt powders is centered between 20 and 220 microns. The two kinds of powder are respectively placed in an electric furnace with the preset temperature of 180-220 ℃ and are kept for 2-10 hours to fully remove the crystal water. The presence of water of crystallization reduces the efficiency of the subsequent in situ synthesis reaction.

(2) According to K₂ZrF₆-KBF₄Taking the appropriate mass of K according to the chemical molar mass ratio of the Al in-situ synthesis reaction system₂ZrF₆、KBF₄And (3) powder. For K₂ZrF₆-KBF₄KBF in-Al in situ Synthesis reaction System₄Easy burning-out, KBF₄The actual addition should be more than 20% excess (compared to the stoichiometric ratio) on the theoretical basis of the original reaction equation and not more than 50% at most. Optimize K₂ZrF₆、KBF₄Mass ratio of two reaction salts, w (K)₂ZrF₆)∶w(KBF₄)＝100∶106～133。

(3) Will K₂ZrF₆、KBF₄Adding the powder into a mortar, mixing, and processing by 30Grinding for min, and wrapping with aluminum foil paper to obtain 5-10 spherical reaction salt preforms. The diameter of the aluminum foil spherical reaction salt preform is 5 cm.

(4) And sequentially pressing the reaction salt preform into the AA6061 aluminum alloy melt in a molten state by using a graphite bell jar to perform in-situ synthesis reaction. The AA6061 aluminum alloy comprises, by mass, 0.15-0.2% of copper Cu, 0.15% of manganese Mn, 1.2% of magnesium Mg, 0.25% of zinc Zn, 0.04-0.35% of chromium Cr, 0.15% of titanium Ti, 0.7-0.8% of silicon Si, 0.3% of iron Fe and the balance of aluminum Al. Ensuring that the mass ratio of Mg to Si in the AA6061 matrix is controlled between 1.5 and 1.72. In the in-situ synthesis reaction stage, the melt temperature of AA6061 aluminum alloy in a molten state is controlled to be between 860 ℃ and 880 ℃.

(5) In the in-situ synthesis reaction stage, a high-frequency spiral external magnetic field with the magnetic field frequency of 10-20HZ is applied at the same time. Because the reaction time of the in-situ synthesis is 20-30min, the reaction is complete, the magnetic field regulation time is not less than 30min, and the magnetic field regulation time is 30-40 min.

(6) After the in-situ synthesis reaction is finished and the liquid level of the melt is calm, carrying out primary slagging-off and refining treatment. The refining agent is hexachloroethane, and the addition amount of the hexachloroethane is 0.4 percent of the mass of the AA6061 aluminum alloy melt.

(7) And then regulating and controlling trace elements in the melt, supplementing easily-lost Mg elements, supplementing Mg elements at 750 ℃, wherein the adding amount is 1.2% of the mass of the AA6061 aluminum alloy melt, continuously applying a high-frequency spiral external magnetic field during the period, the magnetic field frequency is 10-20HZ, and the magnetic field regulation and control time is 5 min.

(8) And carrying out secondary slagging-off and refining treatment on the melt before casting. The melt was poured into a metal mold at a temperature above the liquidus temperature, 720 ℃.

(9) Finally, performing T73 bipolar heat treatment on the prepared cast ingot, wherein the primary solution quenching temperature is 550-; the artificial aging temperature is 180 ℃, and the artificial aging time is 8 h.

The invention provides a high-corrosion-resistance in-situ nanoparticle reinforced aluminum-based composite material and a preparation method thereof. By direct reaction of the melt with a catalystThe synergistic effect of the frequency spiral non-contact magnetic field improves the nano-scale ZrB₂Tissue distribution of in situ reinforcement particles. The addition amount of reaction salt is quantified, and reaction waste is less. The trouble of multiple transfer of the crucible in the multi-field regulation reaction process is avoided. Creates favorable conditions for industrial scale safe production. Nanoscale ZrB₂The particles are generated in the AA6061 matrix in a large amount, the electrode potential distribution of the AA6061 matrix is improved, and material impedance tests show that the material has excellent corrosion resistance and the corrosion resistance is greatly improved compared with the matrix.

Drawings

FIG. 1 shows 6 wt% ZrB₂The XRD diffraction pattern of the in-situ nanoparticle reinforced aluminum matrix composite material is/AA 6061. By using Al-K₂ZrF₆-KBF₄Preparation of composite material ZrB by in-situ reaction system₂The particle collection efficiency is high. The XRD diffraction pattern is within the range of 0-80 degrees, and remarkable ZrB is observed₂Characteristic peaks of the particles. The in-situ nano-particle reinforced aluminum-based composite material is successfully prepared.

FIG. 2 shows AA6061 matrix and 4 wt% ZrB₂/AA6061、6wt％ZrB₂Stress-strain curve of AA6061 in-situ nano-particle reinforced aluminum-based composite material. Due to ZrB₂Particles being formed in bulk in the matrix, ZrB₂The grains are used as heterogeneous nucleating agents in the cooling and solidifying process of the material, and the effect of fine grain strengthening is achieved. Simultaneous ZrB₂As second phase particles, movement of dislocation defects during material strain is hindered. Therefore, the yield strength of the composite material is improved compared with that of the matrix.

FIG. 3 is a graph of electrochemical impedance of composite materials of different mass fractions. The impedance curves of the composite materials with different mass fractions show obvious difference along with the change of the content of the particles. The impedance arc is an important index for evaluating the corrosion performance of the material, and the Rp value fitted according to the impedance arc reflects the difficulty degree of charge transfer in the corrosion reaction process. It is believed that the larger the impedance arc amplitude, the higher the Rp value. From this graph, the impedance arc amplitude can be seen intuitively: 6 wt% ZrB₂/AA6061＞4wt％ZrB₂AA6061 > AA 6061. Compared with a matrix, the composite material has more excellent corrosion resistance.

Detailed Description

The invention may be practiced according to, but is not limited to, the following examples; the terms used in the present invention, unless otherwise specified, generally have the meanings commonly understood by those of ordinary skill in the art; it should be understood that these examples are illustrative only, and are not intended to limit the scope of the present invention in any way; in the following examples, various procedures and methods not described in detail are conventional methods well known in the art.

The invention is further described below

Example 1

Preparation of 4 wt% ZrB₂AA6061 in-situ nanoparticle reinforced aluminum-based composite material

K after being processed by crystallization water removal treatment at 200 ℃ for 3h₂ZrF₆、KBF₄The two reaction salt powders were prepared into spherical reaction salt preforms with a diameter of 5 cm. Wherein K₂ZrF₆Dry weight 180.26g, KBF₄192.19g in net weight, 100: 106 in mass ratio. 1124.40g of AA6061 aluminum alloy is placed in an electromagnetic induction furnace and heated to a molten state, and the melting temperature is 860 ℃. And pressing the reaction salt preform into the position below the liquid level of the molten aluminum alloy and at the center of the melt by using a graphite bell jar to perform in-situ synthesis reaction, continuously applying a spiral high-frequency magnetic field for 30min during the reaction, measuring the temperature by using a thermocouple every 5min, and controlling the temperature of the melt to 860 ℃ all the time, wherein the frequency of the magnetic field is 15 HZ. And after the reaction is finished, the liquid level is stable, slag is removed, and refining and degassing are carried out. Supplementing 13.49g of Mg element at 750 ℃, continuously applying a high-frequency spiral external magnetic field during the period, wherein the frequency of the magnetic field is 12HZ, and the regulating and controlling time of the magnetic field is 5 min. Secondary slag skimming, refining and degassing. Pouring the cast material into a metal mold at 720 ℃ and cooling the cast material to room temperature, carrying out T73 bipolar aging treatment on the cast material, wherein the primary solution quenching temperature is 560 ℃, the secondary solution quenching temperature is 570 ℃, the solution heat preservation time is 1.5 hours respectively, and water quenching is carried out at room temperature; the artificial aging temperature is 180 ℃, and the artificial aging time is 8 h. The tensile strength of the composite material is 397MPa, the yield strength is 375MPa, and the elongation is 17%. Obtained by fitting electrochemical corrosion impedance spectrum, Rs is 3.695ohms, CPE-T is 4.07E-5, CPE-P is 0.88, and Rp is 4884ohms。

Example 2

Preparation of 6 wt% ZrB₂AA6061 in-situ nanoparticle reinforced aluminum-based composite material

K after being processed by crystallization water removal treatment at 180 ℃ for 5h₂ZrF₆、KBF₄The two reaction salt powders were prepared into spherical reaction salt preforms with a diameter of 5 cm. Wherein K₂ZrF₆Dry weight 180.26g, KBF₄192.19g in net weight, 100: 106 in mass ratio. 1094.00g of AA6061 aluminum alloy is placed in an electromagnetic induction furnace and heated to a molten state, and the melting temperature is 860 ℃. And pressing the reaction salt preform into the position below the liquid level of the molten aluminum alloy and at the center of the melt by using a graphite bell jar to perform in-situ synthesis reaction, continuously applying a high-frequency spiral non-contact magnetic field during the reaction, measuring the temperature by using a thermocouple every 5min, controlling the temperature of the melt to 860 ℃ all the time, controlling the frequency of the magnetic field to be 16HZ, and regulating and controlling the time to be 40 min. And after the reaction is finished, the liquid level is stable, slag is removed, and refining and degassing are carried out. Supplementing 13.37g of Mg element at 750 ℃, continuously applying a high-frequency spiral external magnetic field during the period, wherein the frequency of the magnetic field is 13HZ, and the regulating and controlling time of the magnetic field is 5 min. Secondary slag skimming, refining and degassing. Pouring the cast material into a metal mold at 720 ℃ and cooling the cast material to room temperature, carrying out T73 bipolar aging treatment on the cast material, wherein the primary solution quenching temperature is 560 ℃, the secondary solution quenching temperature is 570 ℃, the solution heat preservation time is 1.5 hours respectively, and water quenching is carried out at room temperature; the artificial aging temperature is 180 ℃, and the artificial aging time is 8 h. The tensile strength of the composite material is 438MPa, the yield strength is 420MPa, and the elongation is 15%. And after electrochemical corrosion impedance spectrum fitting, Rs is 3.658ohms, CPE-T is 2.83E-5, CPE-P is 0.88, and Rp is 15154 ohms.

Claims

1. a preparation method of high corrosion resistance in-situ nano-particle reinforced aluminum-based composite material, is characterized in that, concrete steps are as follows:

(1) Decrystallization water treatment of industrial pure K ₂ ZrF ₆ and KBF ₄ reactive salt powders;

(2) Weighing K ₂ ZrF ₆ and KBF ₄ powder, grinding and mixing, wrapping with aluminum foil paper to form a spherical reaction salt preform;

(3) The reaction salt preform is sequentially pressed into the molten AA6061 aluminum alloy melt with a graphite bell to generate an in-situ synthesis reaction; the mass ratio of Mg and Si in the AA6061 matrix is controlled at 1.5-1.72, Cu The elements are controlled at 0.15-0.2%; in the in-situ synthesis reaction stage, a high-frequency spiral external magnetic field is applied at the same time;

(4) until the in-situ synthesis reaction is terminated, and after the melt level is calm, carry out the first slag removal and refining treatment;

(5) Next, the trace elements in the melt are regulated to supplement the easily lost Mg element; during the period, a high-frequency spiral external magnetic field is continuously applied;

(6) carry out secondary slag removal and refining treatment to the melt before pouring, and then pour the melt into the metal mold;

(7) T73 bipolar heat treatment process is adopted for the obtained ingot.

2. The preparation method of a high corrosion resistance in-situ nano-particle reinforced aluminum-based composite material according to claim 1, wherein in step (1), two kinds of reactions of industrial pure K ₂ ZrF ₆ and KBF ₄ The initial particle size distribution of the salt powder is concentrated in 20-220 microns; the two powders are respectively placed in an electric furnace with a preset temperature of 180-220 ° C, and kept for 2-10 hours to fully remove the crystal water.

3. the preparation method of a kind of high corrosion resistance in-situ nano-particle reinforced aluminum-based composite material as claimed in claim 1, is characterized in that, in step (2), for K ₂ ZrF ₆ -KBF ₄ -Al in situ In the synthesis reaction system, KBF ₄ is easy to burn out. The actual addition amount of KBF ₄ should be more than 20% more than the stoichiometric ratio, and should not exceed 50% at most; the mass ratio of K ₂ ZrF ₆ and KBF ₄ two reaction salts , w(K ₂ ZrF ₆ ): w(KBF ₄ )=100:106～133; K ₂ ZrF ₆ and KBF ₄ powders were added to the mortar and mixed, and after grinding for 30min, wrapped with aluminum foil paper into 5-10 A spherical reaction salt preform. The diameter of the aluminum foil spherical reaction salt preform is 5 cm.

4. the preparation method of a kind of high corrosion resistance in-situ nano-particle reinforced aluminum matrix composite material as claimed in claim 1, is characterized in that, in step (3), the element content of AA6061 aluminum alloy is by mass percentage, Cu : 0.15～0.2%, Mn: 0.15%, Mg: 1.2%, Zn: 0.25%, Cr: 0.04～0.35%, Ti: 0.15%, Si: 0.7-0.8%, Fe: 0.3%, Al: balance; In the in-situ synthesis reaction stage, the melt temperature of AA6061 aluminum alloy in the molten state is controlled between 860-880 °C; in the in-situ synthesis reaction stage, a high-frequency spiral external magnetic field is applied at the same time, the magnetic field frequency is 10-20HZ, and the magnetic field is regulated. The time is 30-40min.

5. the preparation method of a kind of high corrosion resistance in-situ nano-particle reinforced aluminum-based composite material as claimed in claim 1, is characterized in that, in step (4), refining agent selects hexachloroethane, and add-on is AA6061 0.4% of the mass of the aluminum alloy melt.

6. the preparation method of a kind of high corrosion resistance in-situ nano-particle reinforced aluminum matrix composite material as claimed in claim 1, is characterized in that, in step (5), at 750 ℃, Mg element is supplemented, and the added amount is AA6061 1.2% of the mass of the aluminum alloy melt, during which a high-frequency spiral external magnetic field was continuously applied, the magnetic field frequency was 10-20HZ, and the magnetic field regulation time was 5min.

7. The preparation method of a high corrosion resistance in-situ nanoparticle-reinforced aluminum-based composite material according to claim 1, wherein in step (6), at a temperature higher than the liquidus temperature, that is, 720° C., The melt is poured into a metal mold.

8. The preparation method of a high corrosion resistance in-situ nanoparticle-reinforced aluminum matrix composite material as claimed in claim 1, wherein in step (7), the T73 bipolar heat treatment process, the first stage The solution quenching temperature is 550-560 ℃, the second-stage solution quenching temperature is 560-570 ℃, the solution holding time is 1.5 hours each, and the room temperature is water quenched; the artificial aging temperature is 180 ℃, and the artificial aging time is 8 hours.