Component design and preparation method of automotive wrought aluminum alloy based on composite modification of rare earth and refiner

Abstract

The invention discloses a component design and preparation method of a vehicle wrought aluminum alloy based on composite modification of rare earth and a refiner, and belongs to the technical field of alloy materials. The composite modified aluminum alloy based on the rare earth and the refiner comprises the following raw materials: an aluminum-titanium-boron intermediate alloy, Er and an aluminum alloy matrix, the mass fraction of titanium in the aluminum-titanium-boron intermediate alloy is 5wt%, and the mass fraction of boron in the aluminum-titanium-boron intermediate alloy is 1wt%; er is added in the form of an aluminum-erbium alloy, and the mass fraction of Er in the aluminum-erbium alloy is 10 wt%. Based on the refining effect of the aluminum-titanium-boron intermediate alloy refiner in the aluminum alloy and the grain refinement, microalloying and metamorphism effects of the rare earth element Er, Ti and B in the aluminum-titanium-boron intermediate alloy and the rare earth element Er jointly participate in grain refinement, and the aluminum alloy is subjected to compound modification; and therefore, the improvement effect on the aluminum alloy matrix is remarkably improved, and the microstructure and the mechanical property of the alloy are optimized.

Description

Technical Field

[0001] The invention relates to the technical field of alloy materials, and in particular to a composition design and preparation method of a rare earth and refiner composite modified automotive deformed aluminum alloy. Background Art

[0002] In the field of automotive parts, the requirements of lightweight should be met as much as possible, and the comprehensive performance of the parts should be further improved under this circumstance; and because automotive parts are often in different working environments and are easily affected by different environments, how to balance the lightweight performance and strength performance of the workpiece still needs further research. Aluminum alloy is a commonly used raw material in the field of automotive parts, but there is still room for further improvement in plastic processing performance, mechanical properties, etc.

[0003] Grain refinement and rare earth alloying are currently commonly used alloy strengthening methods, and are also one of the effective methods to improve the mechanical properties of aluminum alloys. Rare earth elements can play a role in grain refinement and microalloying of aluminum alloys, improve the morphology and distribution of coarse second phases, and thus improve the strength and plasticity of the alloy. Rare earth elements are known as "industrial vitamins" and can be used as a stable and efficient modifier in the production of aluminum alloys. Among them, rare earth Sc can form Al3Sc with Al elements at high temperatures. This substance has an L12 structure, which is almost the same as the structure of α-Al. The mismatch between Al3Sc and α-Al is only 0.9%, which can be used as a good heterogeneous nucleation site, thereby increasing the number of aluminum alloy grains and refining the grain size. The melting point of Al3Sc is 1320℃, so once Al3Sc is formed, it can be used as a stable modifier; however, the price of Sc is very expensive, which greatly limits its application in the research and development and production of aluminum alloys.

[0004] In addition, aluminum-titanium-boron is a widely used refiner in the aluminum industry, but when used alone, the aggregation and precipitation of TiB2 inside it, as well as the poisoning of elements such as Cr and Zr, will cause the refinement effect to decline or even disappear. In order to improve the comprehensive mechanical properties of aluminum alloys, one of the improvement directions is to use Al-Ti-B-RE intermediate alloy refiners to improve the refinement and modification effect of the base alloy, but the existing aluminum-titanium-boron rare earth intermediate alloy refiners still have a lot of room for improvement in improving the performance of aluminum alloys, and the current process for preparing aluminum-titanium-boron rare earth intermediate alloys is usually more complicated, which is not conducive to reducing the production cost of aluminum alloys. At the same time, extruded profiles in the automotive field usually have a large deformation during the preparation process, and the final product has high requirements for strength, and its comprehensive mechanical properties still need to be improved. Summary of the invention

[0005] The purpose of the present invention is to provide a design and preparation method of a deformed aluminum alloy composition for automobiles based on rare earth and refiner composite modification, so as to solve the above-mentioned problems in the background technology. The present invention is based on the refinement effect of the aluminum-titanium-boron master alloy refiner in the aluminum alloy and the grain refinement, microalloying and modification effect of the rare earth element Er. The present invention can carry out composite modification on the aluminum alloy by allowing Ti and B in the aluminum-titanium-boron master alloy and the rare earth element Er to participate in grain refinement together, thereby significantly improving the improvement effect on the aluminum alloy matrix and optimizing the alloy microstructure and mechanical properties.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] One of the technical solutions of the present invention is to provide a rare earth and refiner composite modified aluminum alloy, wherein the raw materials include an aluminum-titanium-boron master alloy, Er and an aluminum alloy matrix; the mass fraction of titanium in the aluminum-titanium-boron master alloy is 5wt%, and the mass fraction of boron is 1wt%; the Er is added in the form of an aluminum-erbium alloy, and the mass fraction of Er in the aluminum-erbium alloy is 10wt%.

[0008] Preferably, the addition amount of the aluminum-titanium-boron master alloy is 0.05-0.5wt% of the composite modified aluminum alloy; and the addition amount of Er is 0.05-0.5wt% of the composite modified aluminum alloy.

[0009] Preferably, the aluminum alloy substrate is 6061 aluminum alloy.

[0010] The second technical solution of the present invention is to provide a method for preparing the above-mentioned rare earth and refiner composite modified aluminum alloy, comprising the following steps:

[0011] Prepare the aluminum-titanium-boron master alloy, Er and aluminum alloy matrix in proportion, and smelt them in an oxygen-free atmosphere to obtain alloy pouring liquid;

[0012] The alloy casting liquid is poured and cooled to obtain the rare earth and refiner-based composite modified aluminum alloy.

[0013] Preferably, the pouring temperature is 720-760°C.

[0014] Preferably, after the cooling operation is completed, the steps of homogenization treatment, extrusion deformation treatment, solution treatment and aging treatment are further included.

[0015] Preferably, the homogenization treatment is carried out at a temperature of 520 to 550° C. and for a time of 5 to 24 hours.

[0016] Preferably, the solution treatment is carried out by keeping the temperature at 520-560° C. for 0.5-3.5 h, followed by water quenching.

[0017] Preferably, the aging treatment is carried out by keeping the temperature at 160-200° C. for 1-12 hours and then cooling with air.

[0018] The third technical solution of the present invention is to provide an application of the above-mentioned rare earth and refiner composite modified aluminum alloy in the field of automotive aluminum alloy materials.

[0019] The beneficial technical effects of the present invention are as follows:

[0020] The present invention is based on the refining effect of the aluminum-titanium-boron master alloy refiner in the aluminum alloy and the grain refining, microalloying and modification effect of the rare earth element Er. The Ti and B in the aluminum-titanium-boron master alloy and the rare earth element Er can participate in grain refining together to perform composite modification on the aluminum alloy, thereby significantly improving the improvement effect on the aluminum alloy matrix and optimizing the alloy microstructure and mechanical properties. The aluminum alloy designed by the present invention based on the composite modification of rare earth and refiner has a significantly refined grain structure in its alloy structure, and the morphology distribution of the Mg2Si phase and the Fe-rich phase is significantly improved compared with the original aluminum alloy matrix.

[0021] By adopting the preparation method designed by the present invention, an aluminum alloy material with refined grains, significantly improved Fe-rich phase, excellent processing performance and comprehensive mechanical properties can be obtained, and the aluminum alloy material has good application value.

[0022] Different from the addition form of first preparing Al-Ti-B-RE master alloy and then adding, the present invention adds aluminum-titanium-boron, rare earth Er to the aluminum alloy matrix, and controls the addition amount and addition form of the two modifiers to improve the microstructure and macroscopic performance of the matrix alloy material, thereby achieving the refinement modification effect and simplifying the production steps. The present invention finds that directly adding rare earth Er alloy and aluminum-titanium-boron master alloy in a specific proportion and a specific addition form can effectively improve the morphology and distribution of β-Fe and α-Fe phases on the basis of grain refinement, significantly improve the alloy plasticity while ensuring the alloy strength, and the modification effect is better than the traditional rare earth alloying method. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 This is a polarized microstructure diagram of the 6061 aluminum alloy used in the present invention.

[0025] Figure 2This is the polarized microstructure image of the product of Example 1.

[0026] Figure 3 This is the polarized microstructure image of the product of Example 2.

[0027] Figure 4 This is the polarized microstructure image of the product of Comparative Example 1.

[0028] Figure 5 This is the polarized microstructure image of the product of Comparative Example 2.

[0029] Figure 6 BSE diagram of the microstructure of the 6061 aluminum alloy used in the present invention.

[0030] Figure 7 This is the BSE microstructure diagram of the product in Example 1.

[0031] Figure 8 This is the BSE diagram of the microstructure of the product of Example 2.

[0032] Fig. 9 This is the BSE diagram of the microstructure of the product of Comparative Example 1.

[0033] Fig.10 This is the BSE diagram of the microstructure of the product of Comparative Example 2.

[0034] Fig.11 It is a comparison chart of the tensile stress-strain curves of the products of Examples 1-3, the products of Comparative Examples 1-2, and the 6061 aluminum alloy used in the present invention. DETAILED DESCRIPTION

[0035] Now, various exemplary embodiments of the present invention are described in detail, and this detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, characteristics and embodiments of the present invention. It should be understood that the terms described in the present invention are only for describing specific embodiments and are not used to limit the present invention.

[0036] In addition, for the numerical range in the present invention, it is understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0037] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the invention pertains. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention.

[0038] The words “include,” “including,” “have,” “contain,” etc. used in the present invention are open-ended terms, meaning including but not limited to.

[0039] The invention provides a rare earth and refiner composite modified aluminum alloy, wherein the raw materials comprise an aluminum-titanium-boron master alloy, Er and an aluminum alloy matrix; the mass fraction of titanium in the aluminum-titanium-boron master alloy is 5wt%, the mass fraction of boron is 1wt%, and the balance is aluminum; the Er is added in the form of an aluminum-erbium alloy, and the mass fraction of Er in the aluminum-erbium alloy is 10wt%.

[0040] Preferably, the addition amount of the aluminum-titanium-boron master alloy is 0.05-0.5wt% of the composite modified aluminum alloy; and the addition amount of Er is 0.05-0.5wt% of the composite modified aluminum alloy.

[0041] Rare earth Er can form nano-scale Al3Er strengthening phase in aluminum, effectively refine aluminum alloy grains, inhibit recrystallization, promote the precipitation of main strengthening phases, improve strength and plasticity, and replace Sc element to a certain extent, but its price is only 1 / 40 of Sc. Compared with the rare earth element Sc, Er has a lower cost, which to a certain extent solves the application limitation caused by the cost of Sc.

[0042] Preferably, the mass ratio of the aluminum-titanium-boron master alloy to the aluminum-erbium alloy is 1-5:5-1.

[0043] Within this ratio range, the rare earth element Er can better play a synergistic role with the refiner, so that the original aluminum alloy grains are significantly refined, and the distribution of the brittle and hard Fe-rich phase and the strengthening phase of the original aluminum alloy is significantly improved, thereby effectively improving the comprehensive mechanical properties of the alloy.

[0044] Preferably, the addition amount of the aluminum-titanium-boron master alloy is 0.2-0.4wt% of the composite modified aluminum alloy; and the addition amount of Er is 0.1-0.2wt% of the composite modified aluminum alloy.

[0045] The present invention also provides a method for preparing the rare earth and refiner composite modified aluminum alloy, comprising the following steps:

[0046] Prepare the aluminum-titanium-boron master alloy, Er and aluminum alloy matrix in proportion, put them into a vacuum induction melting furnace, and place the aluminum-titanium-boron master alloy and Er in the middle of the aluminum alloy matrix, put the preheated metal mold into the furnace chamber of the vacuum induction melting furnace, evacuate and fill with argon protection, and melt them under electromagnetic stirring until they are completely melted to obtain alloy casting liquid;

[0047] The alloy casting liquid is poured into a metal mold and cooled in a furnace, and then taken out and air-cooled to room temperature to obtain the rare earth and refiner-based composite modified aluminum alloy.

[0048] Preferably, after completing the air cooling to room temperature operation, the process further comprises the steps of homogenization treatment, extrusion deformation treatment, solution treatment and aging treatment.

[0049] By adding Al-Ti-B refiner and rare earth elements, a heterogeneous nucleation core with a low mismatch with the matrix is ​​formed to refine the grains and improve the morphology of the large-sized Fe-rich phase. The composite modified aluminum alloy is prepared according to the designed content of each component, which can optimize the microstructure of the matrix, improve the mechanical properties of the product, and prepare a composite modified aluminum alloy with excellent comprehensive performance.

[0050] Preferably, the aluminum alloy matrix is ​​a 6xxx aluminum alloy, more preferably a 6061 aluminum alloy.

[0051] As a type of Al-Mg-Si alloy, 6061 aluminum alloy has the advantages of light weight, high strength, corrosion resistance and good welding performance. It is easy to manufacture parts with complex structures and is an ideal automotive component material.

[0052] Placing the aluminum-titanium-boron master alloy, Er, in the middle of the aluminum alloy matrix can prevent the rare earth elements from settling to the bottom or floating up and mixing in the slag as much as possible, thereby reducing losses and reducing the volatilization of alloy elements.

[0053] Vacuum induction melting can strictly control the content of active elements such as aluminum and titanium in the alloy, effectively remove gas, non-metallic inclusions and non-ferrous metal impurities in the alloy, improve the purity of the alloy, and achieve precise production control, high product purity, less inclusions, and overall more convenient and safer operation.

[0054] Preferably, the homogenization treatment is carried out at a temperature of 520 to 550° C. and for a time of 5 to 24 hours.

[0055] Preferably, the solution treatment is carried out by keeping the temperature at 520-560° C. for 0.5-3.5 h, followed by water quenching.

[0056] Preferably, the aging treatment is carried out by keeping the temperature at 160-200° C. for 1-12 hours and then cooling with air.

[0057] Preferably, the preheating temperature of the metal mold is 300°C.

[0058] Preferably, the argon gas protection after evacuation is evacuated to a vacuum degree of 10 -3 Pa, and then filled with argon to a pressure of 0.02MPa.

[0059] Preferably, during the smelting process, the smelting temperature is controlled by controlling the power of the vacuum induction melting furnace, specifically: first increase the power from 0 to 5 kW, keep warm for 2 minutes, then increase from 5 kW to 10 kW, keep warm for 3 minutes, then increase from 10 kW to 15 kW, keep warm for 3 minutes, then reduce the power from 15 kW to 10 kW, keep warm for 1 minute, and finally reduce the power to 0 kW and let it stand for 1 minute.

[0060] Compared with direct temperature control, power control is easier to operate, and the error of smelting conditions in each batch is small, and the quality stability of the obtained products is better; the initial power loading process must be slow to allow the crucible and the alloy materials in the furnace to be baked for a certain period of time to remove moisture and other attachments.

[0061] Under this smelting condition, not only can the loss be reduced, but also the rare earth element Er and the refiner can better interact with the alloying elements in the aluminum alloy matrix, thereby generating substances that are beneficial to grain refinement and reducing iron-rich phase impurities around the grain boundaries, significantly improving the morphology and distribution of the second phase.

[0062] Preferably, the pouring temperature is 720-760° C.; and the cooling time in the furnace is 15-20 min.

[0063] Preferably, the extrusion deformation treatment comprises the following steps: preheating the extrusion barrel and the die to 420-460° C., and preheating the material to be extruded to 480-520° C., and then extruding at an extrusion speed of 1-2 mm / s.

[0064] Preferably, the method for preparing the aluminum-erbium alloy comprises the following steps:

[0065] Put pure aluminum in a smelting furnace to melt it to obtain molten aluminum liquid;

[0066] Adding metallic erbium to the molten aluminum liquid for secondary smelting, and after the metallic erbium is completely melted, sequentially performing slag removal and degassing treatment to obtain aluminum-erbium alloy liquid;

[0067] The aluminum-erbium alloy liquid is cooled to a pouring temperature and allowed to stand before pouring. After the pouring is completed, the aluminum-erbium alloy is cooled and solidified to obtain the aluminum-erbium alloy.

[0068] Preferably, the smelting temperature is 730-750° C.; the secondary smelting temperature is 810-840° C.; the pouring temperature is 770-790° C.; and the standing time is 3-5 min.

[0069] In the aluminum-titanium-boron master alloy used in the following embodiments and comparative examples of the present invention, the mass fraction of titanium is 5wt%, the mass fraction of boron is 1wt%, and the balance is aluminum.

[0070] In the aluminum-erbium alloy used in the following embodiments and comparative examples of the present invention, the mass fraction of Er is 10 wt %.

[0071] In the 6061 aluminum alloy used in the following embodiments and comparative examples of the present invention, the content of each element is: Al 92.2wt%, C 2.41wt%, O 2.18wt%, Si 0.649wt%, Cu 0.290wt%, Mg 0.757wt%, Zn 0.454wt%, Mn 0.325wt%, Ti 0.0351wt%, Cr 0.0499wt%, Fe 0.290wt%, P 0.0206wt%, S 0.0180wt%, Ca 0.0175wt%, Ni 0.0159wt%, and the balance is impurities.

[0072] The "room temperature" in the present invention is 10-30°C unless otherwise specified.

[0073] All raw materials used in the following examples and comparative examples of the present invention are commercially available products.

[0074] Example 1

[0075] A rare earth and refiner-based composite modified aluminum alloy is prepared from aluminum-titanium-boron master alloy, aluminum-erbium alloy and 6061 aluminum alloy as raw materials; the addition amount of the aluminum-titanium-boron master alloy is 0.26wt% of the composite modified aluminum alloy; the addition amount of Er in the aluminum-erbium alloy is 0.14wt% of the composite modified aluminum alloy.

[0076] The preparation method is as follows:

[0077] (1) Prepare aluminum-titanium-boron master alloy, aluminum-erbium alloy and 6061 aluminum alloy in proportion, put them into a vacuum induction melting furnace, and place the aluminum-titanium-boron master alloy and aluminum-erbium alloy in the middle of the 6061 aluminum alloy. Put the metal mold preheated to 300°C into the furnace cavity of the vacuum induction melting furnace, preheat the pouring cup to 600°C, and evacuate to 10 -3 After Pa, fill with argon until the vacuum reading is 0.02MPa;

[0078] (2) controlling the melting temperature by controlling the power of the vacuum induction melting furnace (specifically: first increasing the power from 0 to 5 kW, keeping the temperature for 2 min, then increasing the power from 5 kW to 10 kW, keeping the temperature for 3 min, then increasing the power from 10 kW to 15 kW, keeping the temperature for 3 min, then reducing the power from 15 kW to 10 kW, keeping the temperature for 1 min, and finally reducing the power to 0 kW and standing for 1 min, so that the slag floats close to the furnace wall), and melting under electromagnetic stirring until it is completely melted to obtain an alloy casting liquid;

[0079] (3) The temperature of the alloy pouring liquid is controlled at 740°C and poured into a preheated metal mold. After the pouring is completed, the alloy pouring liquid is cooled in an argon atmosphere in a furnace for 20 minutes, and then taken out and air-cooled to room temperature in an open environment to obtain a rare earth and refiner composite modified aluminum alloy (cast alloy).

[0080] Example 2

[0081] The only difference from Example 1 is that the addition amount of the aluminum-titanium-boron master alloy is modified to 0.14wt% of the composite modified aluminum alloy, and the addition amount of Er in the aluminum-erbium alloy is modified to 0.26wt% of the composite modified aluminum alloy.

[0082] Example 3

[0083] The only difference from Example 1 is that after completing the air cooling to room temperature in step (3), homogenization treatment, extrusion deformation treatment, solution treatment and aging treatment are further performed;

[0084] The temperature of the homogenization treatment is kept at 550°C for 6 hours, and then cooled to room temperature; the steps of the extrusion deformation treatment are as follows: preheat the extrusion barrel and the mold to 450°C, and preheat the material to be extruded to 500°C, and then extrude at an extrusion speed of 1 to 2 mm / s; the solid solution treatment is kept at 540°C for 1 hour, and then water quenched; the aging treatment is kept at 180°C for 5 hours, and then air cooled.

[0085] Comparative Example 1

[0086] The only difference from Example 1 is that no aluminum-erbium alloy is added, and the addition amount of the aluminum-titanium-boron master alloy is modified to 0.4wt% of the composite modified aluminum alloy.

[0087] Comparative Example 2

[0088] The only difference from Example 1 is that no aluminum-titanium-boron master alloy is added, and the addition amount of Er in the aluminum-erbium alloy is modified to 0.4wt% of the composite modified aluminum alloy.

[0089] Effect verification

[0090] (1) Comparison of microstructure morphology

[0091] The microstructures of the products of Examples 1-2 and Comparative Examples 1-2, as well as the unmodified 6061 aluminum alloy, were analyzed using a FEIQUANTA650 FEG field emission environmental scanning electron microscope from FEI Company of the United States; and polarized microstructure analysis was performed using a German Leica DM4P polarizing microscope. The test results are shown in Figure 2. Figure 1-10 shown.

[0092] Figure 1 This is a polarized microstructure diagram of the 6061 aluminum alloy used in the present invention.

[0093] Figure 2 This is the polarized microstructure image of the product of Example 1.

[0094] Figure 3 This is the polarized microstructure image of the product of Example 2.

[0095] Figure 4 This is the polarized microstructure image of the product of Comparative Example 1.

[0096] Figure 5 This is the polarized microstructure image of the product of Comparative Example 2.

[0097] Figure 6 BSE diagram of the microstructure of the 6061 aluminum alloy used in the present invention.

[0098] Figure 7 This is the BSE microstructure diagram of the product in Example 1.

[0099] Figure 8 This is the BSE diagram of the microstructure of the product of Example 2.

[0100] Fig. 9 This is the BSE diagram of the microstructure of the product of Comparative Example 1.

[0101] Fig.10 This is the BSE diagram of the microstructure of the product of Comparative Example 2.

[0102] right Figure 1-Figure 5 By comparison, it can be found that the 6061 aluminum alloy ( Figure 1 ) has coarse grains, and after adding rare earth and refiner in 6061 aluminum alloy (Examples 1-2), the grain size of the alloy is significantly reduced. Compared with Comparative Examples 1 and 2, the composite modified alloy of Example 1 has the smallest grain size and the grain distribution is more uniform.

[0103] Depend on Figure 6-Figure 10 The displayed content shows that the unmodified 6061 aluminum alloy is mainly composed of α-Al, Chinese character-shaped and needle-shaped iron-rich phases, and dispersed Mg2Si; after adding rare earth, a distinct rare earth phase is formed, and the large-sized Fe-rich phase is obviously refined and spheroidized, and the phase edge becomes smooth. At the same time, the needle-shaped iron-rich phase is reduced, and small-sized short rod-shaped or spherical iron-rich phases appear. This is the result of rare earth element modification of the original Fe-rich phase. In the microstructure of only adding aluminum, titanium and boron ( Fig. 9 ), it can be clearly observed that the large-sized Fe-rich phase still exists without any essential change. A large number of Chinese character-shaped Fe-rich phases are distributed along the grain boundaries and are relatively dense. Based on their distribution state, it can be inferred that their grain refinement is relatively poor.

[0104] pass Figure 1-10It can be inferred from the polarized microstructure diagram and microstructure BSE diagram that the composite modification of rare earth and aluminum-titanium-boron master alloy refiner weakens the harm of brittle and hard Fe-rich phase to the organizational properties, and its precipitate phase distribution characteristics have the effects of both additives while tending to the effect of rare earth elements.

[0105] (2) Comparison of mechanical properties

[0106] The products of Examples 1-3 and Comparative Examples 1-2, as well as the 6061 aluminum alloy used in the present invention, were subjected to mechanical property tests. Tensile tests were performed using an Instron 5900 tensile testing machine in accordance with the national standard GB / T228.1-2021, and stress-strain curves were statistically analyzed. The test results are shown in Table 1. Fig.11 shown.

[0107] Fig.11 It is a comparison chart of the tensile stress-strain curves of the products of Examples 1-3, the products of Comparative Examples 1-2, and the 6061 aluminum alloy used in the present invention.

[0108] Fig.11 Among them, aluminum titanium boron: rare earth = 2:1 (extruded T6 state) represents Example 3; aluminum titanium boron: rare earth = 2:1 represents Example 1; aluminum titanium boron: rare earth = 1:2 represents Example 2; aluminum titanium boron: rare earth = 1:0 represents Comparative Example 1; aluminum titanium boron: rare earth = 0:1 represents Comparative Example 2; 6061 represents 6061 aluminum alloy.

[0109] Fig.11 It is recorded that the yield strength of the rare earth and refiner composite modified aluminum alloy prepared by the method of Example 1 is 84.27MPa, the ultimate tensile strength is 172Mpa, and the elongation reaches 15.2%; while the yield strength of the unmodified 6061 aluminum alloy is 89.85MPa, the ultimate tensile strength is 173MPa, and the elongation is 9.09%. The yield strength and ultimate tensile strength do not change significantly, but the elongation of Example 1 is increased by 67.2% compared with Comparative Example 1.

[0110] The rare earth and refiner composite modified aluminum alloy prepared by the method of Example 2 has a yield strength of 82.48 MPa, an ultimate tensile strength of 168.19 MPa, and an elongation of 13.7%. Compared with the original 6061 aluminum alloy, the yield strength and ultimate tensile strength are slightly reduced, but the elongation is significantly improved by 50.7%.

[0111] The rare earth and refiner composite modified aluminum alloy prepared by the method of Example 3 has a yield strength of 139.16 MPa, a tensile strength of 350.48 MPa, and an elongation of 16.2%. Compared with the original 6061 aluminum alloy, the yield strength, tensile strength, and elongation are increased by 54.9%, 102.6%, and 78.2%, respectively, achieving a significant improvement in technical effects.

[0112] The yield strength of the product of comparative example 1 (without adding aluminum-erbium alloy) is 88.45MPa, the ultimate tensile strength is 173.93Mpa, and the elongation reaches 10.1%; the yield strength of the product of comparative example 2 (without adding aluminum-titanium-boron intermediate alloy) is 79.76MPa, the ultimate tensile strength is 158.78Mpa, and the elongation reaches 12%.

[0113] The above test results show that the aluminum alloy based on rare earth and refiner composite modified by Example 1 and Example 2 has greatly improved plasticity, and the effect is obvious, whether compared with the original 6061 alloy or the aluminum alloy modified only by rare earth or refiner. By comparing Example 1 and Example 2, Comparative Example 1 and Comparative Example 2, it can be found that the iron-rich phase and rare earth phase of Example 1 are more densely distributed and smaller in size, mainly because the synergistic superposition of the aluminum-titanium-boron intermediate alloy and the aluminum-erbium alloy in the solidification process of the alloy has a certain influence on the nucleation and growth mechanism of the iron-rich phase, reduces the size of the iron-rich phase, and has a favorable improvement effect on the plasticity of the alloy. After the modification treatment of Example 3, the improvement effect of the comprehensive performance is more significant.

[0114] By comparing comparative examples 1-2 respectively, it can be found that when the total amount of modifier added is the same, the strength effect of the product prepared when only the aluminum-titanium-boron intermediate alloy is added without adding the aluminum-titanium-boron intermediate alloy is better, but the plasticity is relatively poor, while the strength and plasticity of the product prepared when only the aluminum-titanium-boron intermediate alloy is added without adding the aluminum-titanium-boron intermediate alloy are relatively poor. This may be because: when the rare earth element Er is not added, the heterogeneous nucleation phases TiB2 and TiAl3 in the alloy are easy to aggregate and precipitate, causing the refinement effect of aluminum-titanium-boron to decline. The addition of the rare earth element Er under a specific proportion can reduce the aggregation and precipitation of the heterogeneous nucleation phases TiB2 and TiAl3 when the amount of Er added is very small, and promote the refinement of aluminum-titanium-boron, but the Er addition amount continues to increase, which may convert its effect into a modified precipitation phase. For example, when the addition amount is greater than or equal to the addition amount in Example 1, the main strengthening phase is Mg2Si, and the Fe-rich phase is divided into α and β. The large-sized β-Fe phase is generally considered to be a harmful brittle precipitation phase. In the samples with Er added, the needle-shaped micron phase is the β-Fe phase, and some dispersed finer and sharper needle-shaped or point-shaped phases are more likely to be the Mg2Si phase after energy spectrum testing. Secondly, a few obviously bright white network or point-shaped phases are the phases containing rare earth Er.

[0115] In the cast and unheat-treated state, the product (Comparative Example 1) in which only the aluminum-titanium-boron intermediate alloy and the 6061 aluminum alloy matrix are added has a main strengthening phase of a circular dispersed distribution of Mg2Si, and due to the grain refinement effect, the comprehensive performance is improved compared with the original 6061 aluminum alloy. At the same time, due to the presence of some β-Fe phase therein, the strength improvement is limited.

[0116] In the product (Comparative Example 2) in the cast state without heat treatment, only the Al-Ti-B master alloy and the 6061 Al alloy matrix are added, it is possible that Er plays a modifying role on the original precipitated Fe-rich phase and Mg2Si phase, making the precipitated phases become finer and more dispersed (such as Figure 5 , Fig.10 As shown in ), the plasticity may be improved as a result. And whether it is Comparative Example 2 or Example 1, where only the aluminum-erbium alloy is added, there are more iron-rich phases in the shape of Chinese characters or skeletons, while in the sample without adding aluminum-erbium alloy (Comparative Example 1), there are more refined iron-rich phases in the shape of Chinese characters (such as Figure 7 , Fig. 9 , Fig.10 In addition, the Fe-rich phase of the Er-added product is more finely dispersed, discontinuous, and even partially converted into a rare earth phase compared to the 6061 aluminum alloy, thus effectively reducing the harmful effects of the Fe-rich phase.

[0117] By using Er and aluminum-titanium-boron master alloy refiner in combination and adjusting the dosage and ratio of the two, the erbium element can effectively play a modifying role, thereby promoting the full play of the refinement effect of the aluminum-titanium-boron refiner, and can also make Er effectively play an improvement effect on the harmful phase and strengthening phase in the 6061 aluminum alloy, thereby obtaining a better improvement effect on the alloy performance, especially in terms of plasticity, which is more beneficial to the deformation processing of aluminum alloys and is a good automotive aluminum alloy material.

[0118] The present invention utilizes rare earth erbium and aluminum-titanium-boron master alloy to play the multiple effects of refinement and heterogeneous nucleation in aluminum alloy, plays the effect of modifying and modifying α-Al and iron-rich phase, improves the microstructure and morphology size of α-Al and iron-rich phase, enhances the comprehensive mechanical properties of the product, and can realize the in-depth application of high-performance aluminum alloy in the field of automotive aluminum alloy materials.

[0119] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A rare earth and refiner composite modified aluminum alloy, characterized in that: The raw materials include aluminum-titanium-boron master alloy, Er and aluminum alloy matrix; the mass fraction of titanium in the aluminum-titanium-boron master alloy is 5wt%, and the mass fraction of boron is 1wt%; the Er is added in the form of aluminum-erbium alloy, and the mass fraction of Er in the aluminum-erbium alloy is 10wt%.

2. The composite modified aluminum alloy according to claim 1, characterized in that: The addition amount of the aluminum-titanium-boron master alloy is 0.05-0.5wt% of the composite modified aluminum alloy; the addition amount of Er is 0.05-0.5wt% of the composite modified aluminum alloy.

3. The composite modified aluminum alloy according to claim 1, characterized in that: The aluminum alloy substrate is 6061 aluminum alloy.

4. A method for preparing a rare earth and refiner composite modified aluminum alloy according to any one of claims 1 to 3, characterized in that: The following steps are involved: Prepare the aluminum-titanium-boron master alloy, Er and aluminum alloy matrix in proportion, and smelt them in an oxygen-free atmosphere to obtain alloy pouring liquid; The alloy casting liquid is poured and cooled to obtain the rare earth and refiner-based composite modified aluminum alloy.

5. The preparation method according to claim 4, characterized in that: The pouring temperature is 720-760°C.

6. The preparation method according to claim 4, characterized in that: After the cooling operation is completed, the steps of homogenization treatment, extrusion deformation treatment, solution treatment and aging treatment are also included.

7. The preparation method according to claim 6, characterized in that: The temperature of the homogenization treatment is 520-550° C., and the time is 5-24 hours.

8. The preparation method according to claim 6, characterized in that: The solution treatment is carried out by keeping the temperature at 520-560° C. for 0.5-3.5 hours and then quenching with water.

9. The preparation method according to claim 6, characterized in that: The aging treatment is to keep the temperature at 160-200° C. for 1-12 hours and then cool in air.

10. Use of the rare earth and refiner composite modified aluminum alloy according to any one of claims 1 to 3 in the field of automotive aluminum alloy materials.

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