A high-strength and toughness aluminum alloy and extrusion casting preparation method thereof

Abstract

The present invention relates to a high-strength and toughness aluminum alloy and an extrusion casting preparation method thereof, comprising the following elements by mass percentage: Si 6.5-7.5%, Mg 0.2-0.4%, Cu 0.4-0.8%, RE 0.1-0.3%, Fe 0.1-0.4%, Mo 0.05-0.2%, Ti≤0.06%, Sr 0.01-0.04%, each impurity element content is less than 0.02%, the total impurity element content is less than 0.10%, and the balance is Al. Compared with the prior art, the high-strength and toughness aluminum alloy material prepared by the present invention has a significantly refined structure, and at the same time introduces nano-Al 2 Cu phase, Al 5 Cu 2 Mg 8 Si 6 Phase and micron-scale Al 11 RE 3 , AlFeMoSi phase, while ensuring the strength, significantly improving the thermal stability and plastic toughness of the alloy.

Description

Technical Field

[0001] The invention relates to the field of recycled aluminum alloys, and in particular to a high-strength and toughness aluminum alloy and an extrusion casting preparation method thereof. Background Art

[0002] In the automotive industry, the demand for high-strength and high-temperature resistant materials is growing, and this trend is closely linked to the continuous advancement of automotive technology. Looking to the future, as the demand for lightweight, high-strength, high-temperature resistant and high-toughness materials continues to rise, material innovation becomes particularly important. For example, the scroll disk is a general term for the moving disk and the static disk in the compressor, and is the core part of the air-conditioning compressor of new energy vehicles. The mechanical properties and reliability requirements are extremely high. At present, the mainstream in the industry is to ensure dimensional accuracy through forgings combined with high-precision CNC processing, which has a long cycle and high cost. Faced with the rapid growth of the new energy vehicle industry, the original preparation technology can no longer meet the huge needs of the industry. In addition, the increase in the power density of new energy vehicles has caused the service temperature of the scroll disk to increase to between 180℃-220℃, and compared with the original alloy system, the demand for high-temperature stability is also more urgent. Therefore, it is urgent to develop new alloy materials and preparation technologies to meet the growing needs of the new energy vehicle industry.

[0003] Squeeze casting technology is a preparation technology that directly pours a certain amount of molten metal into a mold cavity coated with lubricant and continuously applies pressure to make the metal crystallize under great pressure and achieve forced shrinkage compensation to obtain castings without casting defects. This technology has the advantages of simple casting process, low production cost, and complex shapes of parts. It also has the characteristics of fine grains, uniform structure, good mechanical properties, and high forming accuracy of die forging products. Therefore, it has become the preferred alternative process for scroll disk preparation technology. In terms of material design, the current mainstream of scroll disks is the traditional hypoeutectic Al-Si-Cu-Mg alloy, and the main strengthening phase is nano-precipitated Al 2 Cu and Mg 2 Si phase. The thermal stability is relatively low. Therefore, how to adopt the extrusion casting process, design new high-strength and tough materials, and realize the preparation of the scroll disk is a key problem faced by the new energy air-conditioning compressor industry.

[0004] Patents CN105522146A, CN103334034A and CN104190876A etc. all avoid the brittleness caused by Si by reducing the Si content (to below 8.5% by mass), but the tensile strength and yield strength of these materials are respectively less than 300 MPa and 100 MPa, which makes it difficult to meet higher performance requirements.

[0005] Patent CN114540672A developed an aluminum alloy material for motor housing. By precisely controlling the content of V, Ti, Mo, and Cu, and introducing Sr for modification, although some yield strength was sacrificed, the tensile strength and thermal conductivity were successfully improved, making its tensile strength exceed 300MPa. However, this is still not enough to meet the stringent standards of the next generation of turbochargers.

[0006] Patents CN114438380A, CN114411020A and CN113930646A focus on improving the strength and toughness of the material, especially by optimizing the content of elements such as Cu and Mo to increase the elongation of the material, thereby providing better protection in vehicle accidents.

[0007] Patent CN110735070A discloses that the aluminum alloy material is composed of an α-Al matrix, primary silicon, eutectic silicon and a strengthening phase, wherein the primary silicon and the eutectic silicon are dispersed in the α-Al matrix; the strengthening phase includes an inhibitor, and the inhibitor is used to inhibit the growth of the primary silicon. The primary silicon and the eutectic silicon are dispersed in the α-Al matrix, and the organization is evenly distributed. Compared with the 4032 material, the strength is increased by about 28.9% and the hardness is increased by about 32.9%. In this patent, the Ni element easily reacts with α-Al, which is a poisoning phenomenon, so that it not only fails to play a strengthening role, but also reduces the strength of the material.

[0008] Patent CN116287886A discloses an Al-Si-Cu-Mg-Sr alloy material, in which the alloy elements and weight percentages are: Si 9.0%-11.0%; Cu 1.0%-2.0%; Mg 0.8%-1.3%; Ni 0.5%-1.3%; Fe≤1.0%; Cr≤0.10%; Zn≤0.25%; Sr 0.02%-0.04%, and the rest is Al and unavoidable impurities; the alloy material has nano-sized Al 2 Cu and Mg 2 Si composite nano-strengthening phase, and submicron-level dot-shaped eutectic silicon; the main strengthening phase in this patent is nano-precipitated Al 2 Cu and Mg 2 Si phase, thermal stability is relatively low.

[0009] Patent CN115852214A reasonably designs the range of Si / Cu (wt% / wt%, indicating the ratio of mass fraction, the same below) and the content of trace elements such as Mo and V, and utilizes the different diffusion rates of Mo and V to form precipitates of different crystal forms, thereby obtaining gradient and regularly distributed intermetallic compounds, and inheriting them to the aging stage, thereby significantly improving the tensile strength and yield strength of the aluminum alloy, among which the tensile strength can be increased to more than 400MPa, and the yield strength can be increased to more than 300MPa. At the same time, the elongation can still be maintained at 4.5-8%, and the toughness and wear resistance are greatly improved. It is very suitable for manufacturing automotive parts such as turbochargers, new energy vehicle air-conditioning turbine discs, and brake clamps.

[0010] In summary, although the research and development of heat-treatable high-strength and toughness aluminum alloys has made significant progress in recent years, the material properties have gradually approached the limit, and the contradiction between strength and toughness and forming ability has become more prominent. Therefore, it has become an urgent task to develop a new generation of high-strength and toughness materials to meet the stringent requirements of key automotive parts such as turbochargers, new energy vehicle air conditioning turbine discs, and brake clamps. Summary of the invention

[0011] In order to solve the above problems in the prior art, the present invention provides a high-strength and toughness aluminum alloy material and an extrusion casting preparation method thereof.

[0012] In order to achieve the above object, the main technical solutions adopted by the present invention include:

[0013] A high-strength and tough aluminum alloy material, wherein the weight percentages of the components are as follows: Si 6.5-7.5%, Mg 0.2-0.4%, Cu 0.4-0.8%, RE 0.1-0.3%, Fe 0.1-0.4%, Mo 0.05-0.2%, Ti≤0.06%, Sr 0.01-0.04%, the content of each impurity element is less than 0.02%, the total impurity element content is less than 0.10%, and the balance is Al.

[0014] A method for preparing a high-strength and tough aluminum alloy by extrusion casting comprises the following steps:

[0015] S1: Drying: drying pure aluminum, pure magnesium, aluminum silicon, aluminum iron, aluminum copper, and aluminum rare earth master alloy;

[0016] Preferably, in step S1, the drying temperature is 200-250° C. and the preheating time is 2-6 hours. The preheating temperature and time can effectively remove moisture from the raw materials.

[0017] Preferably, in step S1, the aluminum-silicon master alloy is an Al-20Si master alloy; the aluminum-iron master alloy is an Al-20Fe master alloy; the aluminum-copper master alloy is an Al-50Cu master alloy; the aluminum-rare earth master alloy includes an Al-5Ti-B master alloy, an Al-10Sr master alloy, an Al-5Mo master alloy and an Al-10RE master alloy.

[0018] S2: Smelting, first add pure aluminum ingot and aluminum silicon master alloy, heat to 750-800℃ for complete melting; then add aluminum iron, aluminum copper, aluminum rare earth master alloy in sequence, after complete melting, reduce the temperature to 670-690℃, add preheated pure magnesium; after the alloy is completely melted, heat to 740-760℃, add refining agent for refining, then stand at 720-740℃ for 15-20min, skim off scum, and obtain aluminum alloy melt;

[0019] Preferably, in step S2, before adding the refining agent, Al-5Ti-B refining agent is first added, and after refining, Al-10Sr master alloy is added at 720-740°C; this can optimally ensure the grain refinement and modification effect of the eutectic Si phase.

[0020] S3: forming, transferring the aluminum alloy melt or the melt obtained by remelting the ingot prepared in step S2 to the mold cavity of the extrusion casting machine for extrusion casting after field treatment, the pouring temperature is controlled at 720-740°C, the mold temperature is controlled at 200-250°C, the speed is controlled at 0.5-2.0m / s, the boost pressure is 80-120MPa, and finally the aluminum alloy casting is obtained. The aluminum alloy casting is subjected to solid solution aging treatment to further improve its strength.

[0021] Preferably, in step S3, the aluminum alloy melt or the melt after remelting the aluminum alloy ingot is poured into a metal mold preheated to 200-250°C at 720-740°C, and cooled to obtain an aluminum alloy casting. Further preferably, the pouring temperature and the mold temperature can ensure that the melt has good fluidity in the mold and ensure the filling of the scroll disk.

[0022] The beneficial effects of the present invention are:

[0023] 1. Compared with the prior art, the high-strength and tough aluminum alloy material prepared by the present invention has a significantly refined structure and introduces nano-Al 2 Cu phase, Al 5 Cu 2 Mg 8 Si 6 Phase and micron-scale Al 11 RE 3, AlFeMoSi phase, while ensuring the strength, significantly improving the thermal stability and plastic toughness of the alloy.

[0024] 2. This preparation method is simple, has good process stability, short cycle and high process controllability. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1 is the theoretical calculation result of the alloy phase composition of Example 1 of the present invention;

[0027] Figure 2 is the theoretical calculation result of the alloy phase composition of Example 2 of the present invention;

[0028] Figure 3 is a low-power optical microscopic photograph of the alloy of Example 1 of the present invention;

[0029] Figure 4 This is a high-power optical microscopic micrograph of the alloy of Example 1 of the present invention;

[0030] Figure 5 is the hardness evolution curve of Example 2 of the present invention and Comparative Example 1 at 180°C;

[0031] Figure 6 is a SEM photograph of the AlFeMoSi phase in the alloy of Example 3 of the present invention;

[0032] Figure 7 It is a comparison of typical tensile curves of the alloys of Example 4 of the present invention and Comparative Example 1. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0034] Embodiment 1:

[0035] The chemical composition (mass percentage) of the high-strength and toughness aluminum alloy material of this embodiment is: 7.5% Si, 0.4% Mg, 0.8% Cu, 0.2% Mo, 0.4% Fe, 0.3% RE, 0.06% Ti, 0.04% Sr, the total of other inevitable impurities is less than 0.1%, and the rest is Al.

[0036] The aluminum alloy material preparation method involved in this embodiment is:

[0037] (1) Drying: Pure aluminum, pure magnesium, Al-20Si master alloy, Al-50Cu master alloy, Al-20Fe master alloy, Al-5Ti-B master alloy, Al-10Sr master alloy, Al-5Mo master alloy and Al-10RE master alloy are dried at a temperature of 250° C. for 4 hours;

[0038] (2) Melting: first add pure aluminum ingot and aluminum silicon master alloy, heat to 800°C for complete melting; then add aluminum iron, aluminum copper, Al-5Mo, Al-10RE master alloy in sequence, after complete melting, reduce the temperature to 680°C, add preheated pure magnesium; after the alloy is completely melted, heat to 750°C, add Al-5Ti-B refiner, keep warm for 10 minutes, then add refining agent for refining, then stand at 720°C for 15 minutes, skim off the scum, and finally add Al-10Sr master alloy to obtain aluminum alloy melt or ingot;

[0039] (3) Forming: The prepared aluminum alloy melt or the melt obtained after remelting the ingot is transferred to the mold cavity of the extrusion casting machine for extrusion casting after field treatment. The pouring temperature is controlled at 720℃, the mold temperature is controlled at 250℃, the speed is controlled at 2.0m / s, and the boost pressure is 120MPa. Finally, the aluminum alloy material A1 is obtained. The aluminum alloy casting is subjected to solid solution at 540℃-2h, and after quenching, it is artificially aged at 180℃-8h to further improve its strength.

[0040] The room temperature mechanical properties of the high strength and toughness aluminum alloy material obtained in Example 1 of the present invention were tested using a universal tensile testing machine. The test results are shown in Table 3.

[0041] Embodiment 2:

[0042] The chemical composition (mass percentage) of the high-strength and toughness aluminum alloy material of this embodiment is: 6.5% Si, 0.2% Mg, 0.4% Cu, 0.05% Mo, 0.1% Fe, 0.1% RE, 0.01% Sr, the total of other inevitable impurities is less than 0.1%, and the rest is Al.

[0043] The aluminum alloy material preparation method involved in this embodiment is:

[0044] (1) Drying: Pure aluminum, pure magnesium, Al-20Si master alloy, Al-50Cu master alloy, Al-20Fe master alloy, Al-10Sr master alloy, Al-5Mo master alloy and Al-10RE master alloy are dried at a temperature of 250° C. for 4 hours;

[0045] (2) Melting: first add pure aluminum ingot and aluminum silicon master alloy, heat to 800°C for complete melting; then add aluminum iron, aluminum copper, Al-5Mo, Al-10RE master alloy in sequence, after complete melting, reduce the temperature to 680°C, add preheated pure magnesium; after complete melting, heat to 750°C, then add refining agent for refining, and stand at 720°C for 15 minutes, skim off the scum, and finally add Al-10Sr master alloy to obtain aluminum alloy melt or ingot;

[0046] (3) Forming: The prepared aluminum alloy melt or the melt obtained after remelting the ingot is transferred to the mold cavity of the extrusion casting machine for extrusion casting after field treatment. The pouring temperature is controlled at 720℃, the mold temperature is controlled at 250℃, the speed is controlled at 2.0m / s, and the boost pressure is 120MPa. Finally, the aluminum alloy material A1 is obtained. The aluminum alloy casting is subjected to solid solution at 540℃-2h, and after quenching, it is artificially aged at 180℃-8h to further improve its strength.

[0047] The room temperature mechanical properties of the die-cast aluminum alloy obtained in Example 2 of the present invention were tested using a universal tensile testing machine. The test results are shown in Table 3.

[0048] Embodiment 3:

[0049] The chemical composition (mass percentage) of the high-strength and toughness aluminum alloy material of this embodiment is: 7% Si, 0.3% Mg, 0.6% Cu, 0.1% Mo, 0.2% Fe, 0.2% RE, 0.03% Ti, 0.03% Sr, the total of other inevitable impurities is less than 0.1%, and the rest is Al.

[0050] The aluminum alloy material preparation method involved in this embodiment is:

[0051] (1) Drying: Pure aluminum, pure magnesium, Al-20Si master alloy, Al-50Cu master alloy, Al-20Fe master alloy, Al-5Ti-B master alloy, Al-10Sr master alloy, Al-5Mo master alloy and Al-10RE master alloy are dried at a temperature of 250° C. for 4 hours;

[0052] (2) Melting: first add pure aluminum ingot and aluminum silicon master alloy, heat to 800°C for complete melting; then add aluminum iron, aluminum copper, Al-5Mo, Al-10RE master alloy in sequence, after complete melting, reduce the temperature to 680°C, add preheated pure magnesium; after the alloy is completely melted, heat to 750°C, add Al-5Ti-B refiner, keep warm for 10 minutes, then add refining agent for refining, then stand at 720°C for 15 minutes, skim off the scum, and finally add Al-10Sr master alloy to obtain aluminum alloy melt or ingot;

[0053] (3) Forming: The prepared aluminum alloy melt or the melt obtained after remelting the ingot is transferred to the mold cavity of the extrusion casting machine for extrusion casting after field treatment. The pouring temperature is controlled at 720℃, the mold temperature is controlled at 250℃, the speed is controlled at 2.0m / s, and the boost pressure is 120MPa. Finally, the aluminum alloy material A1 is obtained. The aluminum alloy casting is subjected to solid solution at 540℃-2h, and after quenching, it is artificially aged at 180℃-8h to further improve its strength.

[0054] The room temperature mechanical properties of the die-cast aluminum alloy obtained in Example 3 of the present invention were tested using a universal tensile testing machine. The test results are shown in Table 3.

[0055] Embodiment 4:

[0056] The chemical composition (mass percentage) of the high-strength and toughness aluminum alloy material of this embodiment is: 6.5% Si, 0.4% Mg, 0.8% Cu, 0.05% Mo, 0.1% Fe, 0.3% RE, 0.04% Ti, 0.02% Sr, the total of other inevitable impurities is less than 0.1%, and the rest is Al.

[0057] The aluminum alloy material preparation method involved in this embodiment is:

[0058] (1) Drying: Pure aluminum, pure magnesium, Al-20Si master alloy, Al-50Cu master alloy, Al-20Fe master alloy, Al-5Ti-B master alloy, Al-10Sr master alloy, Al-5Mo master alloy and Al-10RE master alloy are dried at a temperature of 250° C. for 4 hours;

[0059] (2) Melting: first add pure aluminum ingot and aluminum silicon master alloy, heat to 800°C for complete melting; then add aluminum iron, aluminum copper, Al-5Mo, Al-10RE master alloy in sequence, after complete melting, reduce the temperature to 680°C, add preheated pure magnesium; after the alloy is completely melted, heat to 750°C, add Al-5Ti-B refiner, keep warm for 10 minutes, then add refining agent for refining, then stand at 720°C for 15 minutes, skim off the scum, and finally add Al-10Sr master alloy to obtain aluminum alloy melt or ingot;

[0060] (3) Forming: The prepared aluminum alloy melt or the melt obtained after remelting the ingot is transferred to the mold cavity of the extrusion casting machine for extrusion casting after field treatment. The pouring temperature is controlled at 720℃, the mold temperature is controlled at 250℃, the speed is controlled at 2.0m / s, and the boost pressure is 120MPa. Finally, the aluminum alloy material A1 is obtained. The aluminum alloy casting is subjected to solid solution at 540℃-2h, and after quenching, it is artificially aged at 180℃-8h to further improve its strength.

[0061] The room temperature mechanical properties of the die-cast aluminum alloy obtained in Example 4 of the present invention were tested using a universal tensile testing machine. The test results are shown in Table 3.

[0062] Embodiment 5:

[0063] The chemical composition (mass percentage) of the high-strength and toughness aluminum alloy material of this embodiment is: 7% Si, 0.2% Mg, 0.4% Cu, 0.2% Mo, 0.4% Fe, 0.3% RE, 0.06% Ti, 0.04% Sr, the total of other inevitable impurities is less than 0.1%, and the rest is Al.

[0064] The aluminum alloy material preparation method involved in this embodiment is:

[0065] (1) Drying: Pure aluminum, pure magnesium, Al-20Si master alloy, Al-50Cu master alloy, Al-20Fe master alloy, Al-5Ti-B master alloy, Al-10Sr master alloy, Al-5Mo master alloy and Al-10RE master alloy are dried at a temperature of 250° C. for 4 hours;

[0066] (2) Melting: first add pure aluminum ingot and aluminum silicon master alloy, heat to 800°C for complete melting; then add aluminum iron, aluminum copper, Al-5Mo, Al-10RE master alloy in sequence, after complete melting, reduce the temperature to 680°C, add preheated pure magnesium; after the alloy is completely melted, heat to 750°C, add Al-5Ti-B refiner, keep warm for 10 minutes, then add refining agent for refining, then stand at 720°C for 15 minutes, skim off the scum, and finally add Al-10Sr master alloy to obtain aluminum alloy melt or ingot;

[0067] (3) Forming: The prepared aluminum alloy melt or the melt obtained after remelting the ingot is transferred to the mold cavity of the extrusion casting machine for extrusion casting after field treatment. The pouring temperature is controlled at 720℃, the mold temperature is controlled at 250℃, the speed is controlled at 2.0m / s, and the boost pressure is 120MPa. Finally, the aluminum alloy material A1 is obtained. The aluminum alloy casting is subjected to solid solution at 540℃-2h, and after quenching, it is artificially aged at 180℃-8h to further improve its strength.

[0068] The room temperature mechanical properties of the die-cast aluminum alloy obtained in Example 5 of the present invention were tested using a universal tensile testing machine. The test results are shown in Table 3.

[0069] Comparative Example 1: It is a commercial A356 alloy composition, the purpose of which is to compare the performance of the alloy in the present invention with that of the commercial grade.

[0070] Comparative Example 2: Based on Example 1, the ratio of Cu:Mg was changed to 4:1, and the excess Al 2 The Cu phase easily leads to an increase in room temperature strength and a significant decrease in elongation, which cannot guarantee the toughness requirements of later products. At the same time, the corresponding heat treatment process also needs to be changed, otherwise overburning is likely to occur.

[0071] Comparative Example 3: Based on Example 3, the Cu:Mg ratio was changed to 1:1. The excessive Q phase in the solidification process, although the nano Q phase precipitated after heat treatment has better high temperature performance, it is also easy to cause a significant decrease in room temperature elongation, which is not conducive to improving the toughness of the later product.

[0072] Comparative Example 4: Based on Example 1, the RE content is increased to 0.5%. During the solidification process, the excess Al11RE3 phase is significantly coarsened, and the room temperature elongation is significantly reduced, which is not conducive to improving the toughness of the later product.

[0073] Comparative Example 5: Based on Example 3, Mo:Fe=2:1. During the solidification process, the excess Mo element remains in the matrix to form AlFeMoSi phase and also forms micron-sized Al 12 Mo phase leads to a significant decrease in room temperature elongation.

[0074] The regulation of RE, Mo, and Cu / Mg ratio can change the type and content of nanophases and form high melting point Al 11 RE 3 phase to ensure high temperature strengthening effect; at the same time, the Mo element is introduced to form Al 8 (Fe, Mo)Si phase is used to change the morphology of the impurity iron phase, thereby ensuring the toughness of the material. The strength and toughness of the material are synergistically improved by changing the type of nano-reinforced phase, introducing RE elements and AlFeMoSi phase.

[0075] The ratio of Cu and Mg is to ensure Al 2 The formation of Cu and Q phases, when the Cu content is low, it is easy to cause Mg 2 Si phase is generated. After the Mo and Fe ratio is optimized, it can ensure that the needle-shaped Fe phase is transformed into the blocky AlFeMoSi phase in the figure. The Cu and Mg ratio is to ensure that the nanophase produces good thermal stability and high strength. The Mo and Fe ratio is to increase the elongation, among which the Cu and Mg ratio is important for strength. Mo and Fe increase the elongation and also contribute to the strength to a certain extent, but it is weaker.

[0076] When the RE content is too low, the thermal stability and strengthening effect are weak; when the RE content is high, coarse rare earth phases are easily generated, which split the matrix and reduce the elongation. 11 RE 3 It is an important strengthening phase, and its formation process is normal precipitation during solidification.

[0077] In the present invention, Al 2 The Cu phase has the lowest thermal stability, which is mainly achieved by controlling the ratio of Cu to Mg to form Al 5 Cu 2 Mg 8 Si 6 The Q phase changes the thermal stability by changing the content ratio of the two precipitated phases. 2 The heat resistance temperature of Cu is generally 180-220℃, while the heat resistance temperature of Q phase can be increased to 200-250℃, so there will be a significant improvement in thermal stability.

[0078] Secondly, RE elements do have a high melting point. They have excellent thermal stability during the solidification process and subsequent heat treatment. A small amount of RE elements will affect the aging precipitation of nano-Al 2 The precipitation process of Cu or Q phase inhibits the coarsening of nanophase, thereby improving thermal stability. 8 Cu 4 Ce, Al 11 RE 3Or other micron-sized rare earth phases. Both micron-sized and nano-sized can improve the thermal stability of the alloy. Mo also has the ability to stabilize Al 2 The role of Cu and Q phase.

[0079] For the formation process of several phases, during the solidification of the melt, Al 11 RE 3 and AlFeMoSi, are basically at 560-600℃. Then Al is precipitated at around 500-540℃ 2 Cu or AlCuMgSi eutectic phase. 11 RE 3 Once the AlFeMoSi phase is formed, it cannot be eliminated even in the later solution aging, so the content needs to be controlled and not too much. It belongs to the micron-level strengthening phase.

[0080] For Al 2 The eutectic structure of Cu and Q phase will gradually dissolve back into the matrix during the solution heat treatment process, and precipitate and grow in the later aging process, mainly as a nano-scale strengthening phase.

[0081] Our innovation is these three phases, nanoscale (Al 2 Cu and Q-Al 5 Cu 2 Mg 8 Si 6 phase) and micron-scale (AlFeMoSi and Al 11 RE 3 ) Multi-phase and multi-scale enhanced performance of the two phases.

[0082] For nanoscale Al 2 Cu and Q-Al 5 Cu 2 Mg 8 Si 6 Too much phase content leads to high strength and poor toughness. At the same time, when the Cu content is too high, the cast eutectic Al 2 Under the same heat treatment process, Cu phase is prone to overburning, which reduces the elongation. If there is too little Cu phase, the strength is insufficient; AlFeMoSi phase and Al 11 RE 3 Similarly, when the content of micron-sized reinforcement phase increases, it is easy to coarsen and reduce the elongation. When the content is too small, the reinforcement effects of needle-shaped Fe phase and rare earth phase are relatively weak. Within the composition range of the present invention, a better strength and toughness match can be achieved.

[0083] Nano-scale strengthening phases are formed during the aging process after heat treatment. Micron-scale strengthening phases are formed during solidification. Once precipitated and grown, they cannot be dissolved back by heat treatment later. Therefore, we add Mo and RE elements to regulate the needle-shaped Fe phase and form a block-shaped strengthening phase. For nano-scale strengthening phases, RE and Mo elements can affect the nano-Al during heat treatment. 2 The precipitation and growth process of Cu and Q phases is accelerated, thereby significantly improving the thermal stability.

[0084] Table 1 Chemical composition of each example (wt.%)

[0085]

[0086]

[0087] Table 2 Main strengthening phase content design of each embodiment (wt.%)

[0088]

[0089] Table 3 Room temperature mechanical properties test results of die casting aluminum alloys obtained in Examples 1-5 and Comparative Examples

[0090]

[0091]

[0092] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent transformations made using the contents of the present invention's specification and drawings, or directly or indirectly applied in related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A high-strength and tough aluminum alloy, characterized in that: It includes the following elements in mass percentage: Si 6.5-7.5%, Mg 0.2-0.4%, Cu 0.4-0.8%, RE 0.1-0.3%, Fe 0.1-0.4%, Mo 0.05-0.2%, Ti≤0.06%, Sr 0.01-0.04%, the content of each impurity element is less than 0.02%, the total impurity element content is less than 0.10%, and the balance is Al.

2. The high-strength and toughness aluminum alloy according to claim 1, characterized in that: Cu and Mg are added together, wherein the mass ratio of Cu to Mg elements is 2:

1.

3. The high-strength and toughness aluminum alloy according to claim 1, characterized in that: Composite addition of Mo and Fe, wherein the mass ratio of Mo to Fe elements is 1:

2.

4. The high-strength and toughness aluminum alloy according to claim 1, characterized in that: Composite addition of RE elements, including rare earth Al 11 The RE3 phase content is 0.17-0.51%.

5. The high-strength and toughness aluminum alloy according to claim 1, characterized in that: The Al5Cu2Mg8Si6 phase content is 0.65-1.30%, and the Al2Cu phase content is 0.5-1.0%.

6. The high-strength and toughness aluminum alloy according to claim 1, characterized in that: The AlFeMoSi phase content is 0.5-2.0%.

7. A method for preparing a high-strength and tough aluminum alloy by extrusion casting according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1: Drying: drying pure aluminum, pure magnesium, aluminum silicon, aluminum iron, aluminum copper, and aluminum rare earth master alloy; S2: Smelting, first add pure aluminum ingot and aluminum silicon master alloy, heat to 750-800℃ for complete melting; then add aluminum iron, aluminum copper, aluminum rare earth master alloy in sequence, after complete melting, reduce the temperature to 670-690℃, add preheated pure magnesium; after the alloy is completely melted, heat to 740-760℃, add refining agent for refining, then stand at 720-740℃ for 15-20min, skim off scum, and obtain aluminum alloy melt; S3: forming, transferring the aluminum alloy melt prepared in step S2 to the mold of the extrusion casting machine for pressure casting after field treatment, the pouring temperature is controlled at 720-750°C, the mold temperature is controlled at 200-250°C, the speed is controlled at 0.5-2.0m / s, the boost pressure is 80-120MPa, and finally an aluminum alloy casting is obtained; the aluminum alloy casting is subjected to solid solution aging treatment to further improve its strength.

8. A method for preparing a high-strength and tough aluminum alloy by extrusion casting according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1: Drying: drying pure aluminum, pure magnesium, aluminum silicon, aluminum iron, aluminum copper, and aluminum rare earth master alloy; the aluminum rare earth master alloy includes Al-5Ti-B, Al-10Sr, Al-5Mo, and Al-10RE master alloy; S2: Melting, first add pure aluminum ingot and aluminum silicon master alloy, heat to 750-800℃ for complete melting; then add aluminum iron, aluminum copper, Al-5Mo, Al-10RE master alloy in sequence, after complete melting, reduce the temperature to 670-690℃, add preheated pure magnesium; after the alloy is completely melted, heat to 740-760℃, add Al-5Ti-B refiner, keep warm for 10min, then add refining agent for refining, then stand at 720-740℃ for 15-20min, skim off scum, and finally add Al-10Sr master alloy to obtain aluminum alloy melt; S3: forming, transferring the aluminum alloy melt prepared in step S2 to the mold of the extrusion casting machine for pressure casting after field treatment, the pouring temperature is controlled at 720-750°C, the mold temperature is controlled at 200-250°C, the speed is controlled at 0.5-2.0m / s, the boost pressure is 80-120MPa, and finally an aluminum alloy casting is obtained; the aluminum alloy casting is subjected to solid solution aging treatment to further improve its strength.

9. The method for preparing a high-strength and toughness aluminum alloy by extrusion casting according to claim 7 or 8, characterized in that: The external field treatment includes at least one of mechanical stirring, ultrasonic treatment, electromagnetic stirring, external solid or gas disturbance; the solution temperature of step S3 is 520-540°C, the solution time is 2-4h, the artificial aging temperature is 180-200°C, and the artificial aging time is 2-16h.

10. The method for preparing a high-strength and tough aluminum alloy by extrusion casting according to claim 7, characterized in that: The aluminum-silicon master alloy is an Al-20Si master alloy; the aluminum-iron master alloy is an Al-20Fe master alloy; the aluminum-copper master alloy is an Al-50Cu master alloy; the aluminum-rare earth master alloy includes Al-5Ti-B, Al-10Sr, Al-5Mo, and Al-10RE master alloys.

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