A high-strength, high-toughness and high-plasticity aluminum alloy and casting and forging composite preparation method thereof

Abstract

The invention discloses a high-strength, high-toughness and high-plasticity aluminum alloy and a casting and forging composite preparation method thereof, which belongs to the technical field of nonferrous metal alloys and solves the problem that the aluminum alloy forgings in the prior art have uneven structures and cannot have both high strength, toughness and high plasticity. The components of the aluminum alloy include, by mass percentage: Cu 4.2-5.0%, Mg 0.5-1.4%, Mn 0.6-1.0%, Cr 0.1-0.2%, Ti 0.1-0.15%, B 0.01-0.1%, single impurity ≤ 0.05%, total impurity ≤ 0.15%, and the balance is Al. The aluminum alloy has a tensile strength of 450-480 MPa, a yield strength of 340-360 MPa, and an elongation after fracture of 14-16%. The preparation method of the invention includes batching, smelting, extrusion casting, homogenization annealing, forging, and solid solution aging treatment.

Description

Technical Field

[0001] The invention relates to the technical field of nonferrous metal alloys, and in particular to a high-strength, high-toughness and high-plasticity aluminum alloy and a casting and forging composite preparation method thereof. Background Art

[0002] With the rapid development of the transportation industry, the demand for lightweight transportation vehicles is becoming increasingly strong. Due to its excellent properties such as low density, high strength, and corrosion resistance, aluminum alloys are replacing steel at an increasingly rapid pace, especially for important load-bearing components and structural parts such as aircraft, spacecraft, railway vehicles, freight cars, automobiles, ships, artillery tanks, etc. that have high lightweight requirements. For example, almost all aircraft structural parts are made of aluminum alloy die forgings. It has become a trend to replace aluminum alloy castings with aluminum alloy die forgings in application scenarios such as automobile (especially heavy-duty vehicles and large and medium-sized passenger cars) wheels, bumpers, base beams, tank road wheels and turret frames, helicopter dynamic and stationary rings, and train cylinders and piston skirts.

[0003] There are two main types of casting and forging composite forming processes. One is forging when the aluminum alloy is in liquid or semi-solid state during the casting process, and the other is forging after gravity casting to form a forging blank. The characteristics of the first type of process are: 1) It can be formed in one time, which reduces the defects of casting looseness and pores to a certain extent; 2) The forging process is a closed die forging method in the mold, which has the problems of small deformation, most of the metal microstructure is casting structure, and the forging streamline is not obvious. Its performance is between ordinary casting and forging. The advantage of the second type of casting and forging process is that it can increase the forging deformation and greatly reduce defects such as casting looseness and pores. The disadvantages of the second type of process are more prominent: 1) The surface of the gravity casting product is rough and has more impurities. During the forging process, impurities enter the forging and affect the product performance; 2) It is necessary to use machining to remove impurities, which results in long construction period and high cost.

[0004] Therefore, the casting and forging composite preparation process of aluminum alloys needs to be continuously improved to meet the application requirements of high-strength, high-toughness, lightweight, and complex-structured aluminum alloy forgings in fields such as aircraft landing gear, engine casings, disc-shaft assemblies, and cross shafts. Summary of the invention

[0005] In view of the above situation, the present invention aims to provide a high-strength, toughness and high-plasticity aluminum alloy and a casting and forging composite preparation method thereof, which is used to solve the problems of uneven structure, high strength, toughness and high plasticity of aluminum alloy forgings prepared by existing casting and forging technologies.

[0006] The purpose of the present invention is mainly achieved through the following technical solutions:

[0007] On the one hand, the present invention provides an aluminum alloy with high strength, toughness and plasticity, wherein the mass fraction of the chemical components of the aluminum alloy is as follows: Cu 4.2-5.0%, Mg 0.5-1.4%, Mn 0.6-1.0%, Cr 0.1-0.2%, Ti 0.1-0.15%, B 0.01-0.1%, single impurity ≤0.05%, total impurity ≤0.15%, and the balance is Al.

[0008] Furthermore, the aluminum alloy has a tensile strength of 450-480 MPa, a yield strength of 340-360 MPa, and an elongation after fracture of 14-16% at room temperature.

[0009] On the other hand, the present invention also provides a casting and forging composite preparation method of a high-strength, toughness and high-plasticity aluminum alloy, comprising the following steps:

[0010] S1: batching, weighing raw materials according to the mass percentage of each element;

[0011] S2: melting the raw materials three times to obtain aluminum alloy molten liquid;

[0012] S3: squeeze casting;

[0013] S4: homogenization annealing;

[0014] S5: Forging;

[0015] S6: solution aging treatment.

[0016] Furthermore, in S1, the raw materials used are Al-60Cu master alloy, pure Mg, Al-10Mn master alloy, Al-4Cr master alloy, and Al-5Ti-1B.

[0017] Furthermore, in S2, the smelting process includes: melting pure Al at 750-800°C, adding Al-60Cu master alloy, Al-10Mn master alloy, and Al-4Cr master alloy in sequence, and keeping warm for 30 minutes after all are melted to obtain a primary smelting liquid; cooling the primary smelting liquid to 690-730°C, adding pure Mg and Al-5Ti-1B refiner wrapped in aluminum foil, stirring after all are melted, and keeping warm for 20 minutes to obtain a secondary smelting liquid; adding a slag remover to the secondary smelting liquid and keeping warm for 20 minutes, and introducing argon for refining and degassing, cooling to 690-710°C, standing for 30-60 minutes, and skimming to obtain a tertiary smelting liquid.

[0018] Furthermore, in S3, the process conditions are as follows: the aluminum liquid temperature is 680-700°C, the mold temperature is 230-280°C, the injection speed is 0.04-0.5 m / s, the injection force is 100-150 MPa, and the injection time is 10-15 s.

[0019] Further preferably, in S3, the aluminum liquid temperature is 680° C., the mold temperature is 280° C., the injection speed is 0.2 m / s, and the injection force is 150 MPa.

[0020] Furthermore, in S4, the homogenization annealing process conditions are: keeping at 400°C to 450°C for 6 to 10 hours, then heating to 480 to 520°C for 10 to 24 hours, and cooling with the furnace.

[0021] Further preferably, in S4, the temperature is kept at 450°C for 6 hours, then the temperature is raised to 480-520°C and kept for 20 hours, and then cooled with the furnace.

[0022] Furthermore, in S5, the process conditions are: forging temperature 450-470°C, die temperature 400-450°C, deformation 50-80%, forging speed 10-20 mm / s in the first stage, 1-5 mm / s in the second stage, and holding time 5-10 s.

[0023] Further preferably, in S5, the forging temperature is 450-460°C, the die temperature is 400-450°C, and the deformation amount is 70%.

[0024] Furthermore, in S6, the temperature is kept at 490-520° C. for 1-10 hours to form a supersaturated solution solid, followed by water quenching at room temperature; the temperature is lowered to 150-170° C. and kept at this temperature for 10-24 hours to precipitate a crystal phase, followed by air cooling.

[0025] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0026] a) The present invention improves the recrystallization temperature by optimizing the alloy element content, thereby improving the mechanical properties such as strength limit and yield limit by reducing the coarse grains in the product, and can extend the service life of the product. The room temperature tensile strength of the aluminum alloy prepared by the preparation method of the present invention is 450-480MPa, the yield strength is 340-360MPa, and the elongation after fracture is 14-16%.

[0027] b) The present invention refines the grain structure through the casting pressure during the extrusion casting process, and combines the casting and forging composite process to eliminate the casting defects of the aluminum alloy such as shrinkage, looseness, inclusions, etc., to obtain a good forging structure streamline, and avoid the problem of streamline irregularity, eddy current and through-flow that significantly reduce the plasticity index, fatigue strength and corrosion resistance of the aluminum alloy.

[0028] c) The aluminum alloy prepared by the present invention has good strength and toughness performance while further improving plasticity, and can be used in scenes with complex shapes and high strength and toughness requirements, such as aircraft structural parts, wheels, bumpers, and base beams of heavy-duty vehicles and large and medium-sized buses, road wheels and turret frames of tanks, dynamic and stationary rings of helicopters, cylinders and piston skirts of trains, etc.

[0029] Other features and advantages of the present invention will be set forth in the following description, and in part will be apparent from the description, or may be learned by practicing the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like components throughout the drawings.

[0031] Figure 1 : Schematic diagram of the metallographic structure of the aluminum alloy prepared in Example 1 of the present invention;

[0032] Figure 2 : Schematic diagram of the metallographic structure of the aluminum alloy prepared in Example 2 of the present invention;

[0033] Figure 3 : Schematic diagram of the metallographic structure of the aluminum alloy prepared in Comparative Example 1;

[0034] Figure 4 : Schematic diagram of the metallographic structure of the aluminum alloy prepared in Comparative Example 2;

[0035] Figure 5 : Schematic diagram of the SEM structure of the aluminum alloy gold prepared in Example 2 of the present invention;

[0036] Figure 6 : Schematic diagram of the SEM structure of the aluminum alloy prepared in Comparative Example 2; DETAILED DESCRIPTION

[0037] Preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of the present invention and are used to explain the principles of the present invention together with the embodiments of the present invention.

[0038] The invention provides an aluminum alloy with high strength, toughness and plasticity. The components of the aluminum alloy are as follows in mass percentage: Cu 4.2-5.0%, Mg 0.5-1.4%, Mn 0.6-1.0%, Cr 0.1-0.2%, Ti 0.1-0.15%, B 0.01-0.1%, single impurity ≤0.05%, total impurity ≤0.15%, and the balance is Al.

[0039] The present invention improves mechanical properties by changing alloy composition to increase recrystallization temperature and refine grains. The increase in recrystallization temperature reduces coarse grain precipitation and has a positive effect on significantly improving yield strength, tensile strength and elongation after fracture.

[0040] The following is a detailed description of the effects and dosage of the components in the present invention:

[0041] Cu: Main alloying element. According to the Al-Cu binary phase diagram, when the content is too high, the excess Cu atoms and Fe atoms form a coarse Al7Cu2Fe brittle precipitation phase, causing a sharp drop in the alloy's fracture toughness and over-solution burning, thereby reducing the mechanical properties and corrosion resistance. It also increases the alloy density, which does not meet the requirements of lightweight. Therefore, the present invention controls Cu to 4.2-5.0%, and improves the fracture toughness while ensuring high strength, corrosion resistance and lightweight performance.

[0042] Mg: When the Cu content is constant, the Mg content determines the type and amount of the precipitated phase, which in turn affects the tensile strength, yield strength and elongation of the alloy after natural aging and artificial aging. When the Cu content is in the range of 1-4%, the tensile strength of the alloy increases when the Mg content increases from 0.5% to 2%, and the strength of the alloy decreases as the Mg content continues to increase. When the Cu content is in the range of 4-5%, the Mg element content changes the amount of Al2CuMg strengthening phase and Al2Cu strengthening phase. When the content exceeds a certain value, only Al2CuMg strengthening phase is formed, and the strength of the alloy decreases. The present invention controls Mg to 0.5-1.4%, thereby achieving the optimal tensile strength without reducing the tensile strength and yield strength.

[0043] Mn: micro alloying element, mainly eliminates the harmful effects of Fe and ensures corrosion resistance. Mn significantly increases the recrystallization temperature and is not easy to recrystallize during hot working. In addition, Al6Mn compound and Fe generate Al6MnxFe1-x compound, further reducing the adverse effects of Fe. The present invention controls Mn 0.6-1.0%, thereby increasing the recrystallization temperature and reducing the precipitation of coarse crystals, thereby increasing the tensile strength and yield strength, and simultaneously eliminating the adverse effects of Fe on corrosion performance.

[0044] Ti and Cr are commonly used refiners, and B is an element introduced by adding Al-5Ti-1B refiner. Ti is easy to form Al3Ti during casting, and the peritectic reaction generates non-spontaneous nucleation cores, which further refines the grains, improves the cast structure, and significantly improves the mechanical properties. Chromium (Cr) forms CrFeAl7 and CrMnAl in aluminum. 12The present invention controls the content of Ti and Cr, realizes the refinement of ingot crystals and equiaxed crystals, effectively reduces casting cracks, and improves the surface quality of castings.

[0045] The present invention also provides a method for preparing an aluminum alloy with high strength, toughness and plasticity. Compared with the extrusion casting and gravity casting and forging composite preparation processes in the prior art, the method of extrusion casting followed by forging is adopted, which fully combines the process advantages of extrusion casting and forging. The material properties of the aluminum alloy prepared by the present invention in terms of tensile strength, yield strength and elongation at room temperature are significantly improved.

[0046] The present invention provides a method for preparing a high-strength, high-toughness and high-plasticity aluminum alloy, comprising:

[0047] S1: batching, weighing raw materials according to the mass percentage of each element in the aluminum alloy;

[0048] S2: melting the raw materials to obtain aluminum alloy molten liquid;

[0049] S3: squeeze casting;

[0050] S4: homogenization annealing;

[0051] S5: Forging;

[0052] S6: solution aging treatment.

[0053] Specifically, in S1, the raw materials used are Al-60Cu master alloy, pure Mg, Al-10Mn master alloy, Al-4Cr master alloy, and Al-5Ti-1B.

[0054] Specifically, in S2, the smelting process includes:

[0055] After pure Al is melted at 750-800°C, Al-60Cu master alloy, Al-10Mn master alloy and Al-4Cr master alloy are added in sequence, all are melted and kept warm for 30-60 minutes, such as 30 minutes, to obtain a primary smelting liquid; then the smelting liquid is cooled to 690-730°C, pure Mg wrapped in aluminum foil and Al-5Ti-1B refiner are added, all are melted and stirred, and kept warm for 20-40 minutes, such as 20 minutes, to obtain a secondary smelting liquid; then a slag remover is added and kept warm for 20-40 minutes, such as 20 minutes, and argon is introduced for refining and degassing, cooled to 690-710°C and allowed to stand for 30-60 minutes, and slag is removed to obtain a tertiary smelting liquid.

[0056] Specifically, in S2, in the secondary smelting process, pure Mg is added later and wrapped with aluminum foil to reduce Mg burnout. In the tertiary smelting process, the slag remover is added before degassing to prevent gas from being introduced during stirring.

[0057] Specifically, in S3, the process conditions are: aluminum liquid temperature is 680-700°C, mold temperature is 230-280°C, injection speed is 0.04-0.5 m / s, injection force is 100-150 MPa, and injection time is 10-15 s.

[0058] Specifically, in S3, further preferably, the aluminum liquid temperature is 680° C., the mold temperature is 280° C., the injection speed is 0.2 m / s, and the injection force is 150 MPa.

[0059] Specifically, in S4, the process conditions are: keeping the temperature at 400°C to 450°C for 6 to 10 hours, then heating to 480 to 520°C and keeping the temperature for 10 to 24 hours, and then cooling with the furnace.

[0060] Specifically, in S4, it is further preferred that the temperature is kept at 450°C for 6 hours, then the temperature is increased to 480-520°C and kept for 20 hours, and then cooled with the furnace.

[0061] Specifically, in S4, a two-stage homogenization annealing is adopted to fully dissolve the second phase in the alloy into the matrix, effectively avoiding overburning of part of the second phase in the alloy, and providing a forging material with uniform structure for S5.

[0062] Specifically, in S5, if the speed of the first stage during forging is too low, the required forging equipment may be too large or the product may be difficult to form due to excessive cooling speed. The speed of the second stage should not be too high to prevent the core temperature from being too high and recrystallizing, which will lead to reduced performance and easy generation of microcracks, affecting the surface quality. The holding time can be controlled to reduce the amount of springback. Therefore, the forging speed of the first stage is controlled to be 10-20 mm / s, the forging speed of the second stage is 1-5 mm / s, and the holding time is 5-10s to achieve uniform internal structure of the alloy and avoid coarse lattice precipitation, thereby ensuring surface performance and low springback, and finally achieving a significant improvement in plasticity.

[0063] Specifically, in S5, if the forging temperature is too high, the material will be overheated and the grains will be coarse. If the temperature is too low, the metal will be hardened when deformed, which will increase the deformation resistance and reduce the plasticity of the metal. In severe cases, it will cause deformation and cracking. Controlling the forging temperature to 450-470°C can improve the plasticity of the material while ensuring the surface properties of the material. The forging temperature is 450-470°C and the die temperature is 400-450°C.

[0064] Specifically, in S5, if the deformation is too small, the performance is low, and if the deformation is too large, the internal microstructure of the forging is uneven. Controlling the deformation to 50-80% can improve the product performance under the condition of relatively uniform internal microstructure.

[0065] Specifically, in S5, further preferably, the forging temperature is 450-460° C., the die temperature is 400-450° C., and the deformation amount is 70%.

[0066] Specifically, in the S6, the temperature is kept at 490-520° C. for 1-10 hours to form a supersaturated solution solid, and then quenched in water at room temperature to form a supersaturated solid solution; the temperature is lowered to 150-170° C. and kept for 10-24 hours to precipitate a strengthening phase for aging, and then air-cooled.

[0067] The following specific examples and comparative examples are used to demonstrate the performance of aluminum alloy products prepared by different forging processes. Examples 1-4 of the present invention are aluminum alloys prepared by the preparation method of the present invention, and comparative examples 1-2 are aluminum alloys prepared by the prior art extrusion casting and gravity casting forging composite processes.

[0068] Example 1

[0069] A casting and forging composite preparation method of an aluminum alloy, wherein the aluminum alloy has the following chemical composition and mass percentage: Cu 4.6%, Mg 0.9%, Mn 0.7%, Cr 0.20%, Ti 0.1%, B 0.075%, a single impurity ≤ 0.05%, a total impurity ≤ 0.15%, and the balance is Al. The preparation steps are as follows:

[0070] S1: Ingredients: weigh pure Al, Al-60Cu master alloy, pure Mg, Al-10Mn master alloy, Al-4Cr master alloy, and Al-5Ti-1B as raw materials according to the mass percentage of each element;

[0071] S2: Smelt the raw materials to obtain aluminum alloy molten liquid. Specifically, the smelting process is to melt pure Al at 780°C, then add Al-60Cu master alloy, Al-10Mn master alloy, Al-4Cr master alloy in sequence, and keep them warm for 30 minutes after all are melted to obtain a primary molten liquid, then cool the molten liquid to 700°C, add pure Mg wrapped in aluminum foil and Al-5Ti-1B refiner, stir after all are melted, and keep warm for 20 minutes to obtain a secondary molten liquid, then add a slag remover and stir, keep warm for 20 minutes, and pass argon gas for refining and degassing, cool to 690°C and stand for 60 minutes ， The slag is removed to obtain the tertiary smelting liquid.

[0072] S3: Squeeze casting: aluminum liquid temperature is 690℃, mold temperature is 260℃, injection speed is 0.1m / s, injection force is 120MPa, and injection time is 15s;

[0073] S4: Homogenization annealing: 450℃×6h+500℃×20h, furnace cooling;

[0074] S5: Forging: forging temperature 460℃, die temperature 450℃, deformation 70%, forging speed 15mm / s in the first stage, 1mm / s in the second stage, holding time 10s.

[0075] S6: Solution aging treatment: The obtained cast rod is heated to 500°C for solution treatment, kept at this temperature for 2 hours, and then water-cooled after being taken out of the furnace. Subsequently, the water-cooled ingot is heated to 160°C for aging treatment, kept at this temperature for 12 hours, and the aluminum alloy is obtained.

[0076] Example 2

[0077] A casting and forging composite preparation method of an aluminum alloy, wherein the chemical composition of the aluminum alloy is, by mass percentage, Cu 4.3%, Mg 0.6%, Mn 0.6%, Cr 0.10%, Ti 0.1%, B 0.075%, a single impurity ≤ 0.05%, a total impurity ≤ 0.15%, and the balance is Al.

[0078] The preparation steps and conditions are consistent with those in Example 1.

[0079] Example 3

[0080] A casting and forging composite preparation method of an aluminum alloy, wherein the chemical composition of the aluminum alloy is consistent with that of Example 1. In the preparation S3, the extrusion casting conditions are: aluminum liquid temperature is 680°C, mold temperature is 280°C, injection speed is 0.2m / s, injection force is 150MPa, and injection time is 10s. The other steps are consistent with those of Example 1.

[0081] Example 4

[0082] A casting and forging composite preparation method of an aluminum alloy, wherein the chemical composition of the aluminum alloy is consistent with that of Example 1. In the preparation S5, the forging temperature is 450°C, the die temperature is 450°C, the deformation is 80%, the forging speed is 10 mm / s in the first stage, 5 mm / s in the second stage, and the holding time is 10 s. The other steps are consistent with those of Example 1.

[0083] Example 5

[0084] A casting and forging composite preparation method of an aluminum alloy, wherein the chemical composition of the aluminum alloy is consistent with that of Example 1. In the preparation S5, the forging temperature is 450°C, the die temperature is 450°C, the deformation is 40%, the forging speed is 10 mm / s in the first stage, 10 mm / s in the second stage, and the holding time is 10 s. The other steps are consistent with those of Example 1.

[0085] Comparative Example 1

[0086] A method for preparing an aluminum alloy by extrusion casting, wherein the chemical composition content of the aluminum alloy is consistent with that of Example 1. The preparation steps are as follows:

[0087] The conditions of S1-S2 are consistent with those of Example 1.

[0088] S3 extrusion casting: aluminum liquid temperature is 690℃, mold temperature is 260℃, injection speed is 0.1m / s, injection force is 120MPa, and injection time is 15s.

[0089] S4 homogenization annealing: 450℃×6h+500℃×20h, furnace cooling;

[0090] S5 solution aging treatment: the obtained cast rod is heated to 500°C, solution treated, kept at temperature for 2 hours, and then water-cooled. Subsequently, the water-cooled ingot is heated to 160°C, aging treated, kept at temperature for 12 hours, and the aluminum alloy is obtained.

[0091] Comparative Example 2

[0092] A gravity casting and forging composite preparation method of an aluminum alloy, wherein the chemical composition content of the aluminum alloy is consistent with that of Example 2. The preparation steps are as follows:

[0093] The conditions of S1-2 are consistent with those of Example 1.

[0094] S3 gravity casting: aluminum liquid temperature is 690℃, mold temperature is 260℃;

[0095] S4 homogenization annealing: 450℃×6h+500℃×20h, furnace cooling;

[0096] S5 forging: forging temperature 460℃, die temperature 450℃, deformation 70%, forging speed 15mm / s in the first stage, 1mm / s in the second stage, holding time 10s;

[0097] S6 solution aging treatment: the obtained cast rod is heated to 500°C, solution treated, kept at this temperature for 2 hours, and then water-cooled. Subsequently, the water-cooled ingot is heated to 160°C, aging treated, kept at this temperature for 12 hours, and the aluminum alloy is obtained.

[0098] Table 1 Alloy composition of examples and comparative examples

[0099] serial number Cu Mg Mn Cr Ti B Al Example 1 4.6 0.9 0.7 0.2 0.1 0.075 margin Example 2 4.3 0.6 0.6 0.1 0.1 0.075 margin Example 3 4.6 0.9 0.7 0.2 0.1 0.075 margin Example 4 4.6 0.9 0.7 0.2 0.1 0.075 margin Example 5 4.6 0.9 0.7 0.2 0.1 0.075 margin Comparative Example 1 4.6 0.9 0.7 0.2 0.1 0.075 margin Comparative Example 2 4.3 0.6 0.6 0.1 0.1 0.075 margin

[0100] Table 2 Process conditions of examples and comparative examples

[0101]

[0102]

[0103] Table 3 Performance comparison of examples and comparative examples

[0104] Example Tensile strength(MPa) Yield strength(MPa) Elongation after break (%) Example 1 475 355 16 Example 2 458 349 14.9 Example 3 461 348 14.5 Example 4 465 350 15.2 Example 5 455 332 13.8 Comparative Example 1 386 278 10.4 Comparative Example 2 412 306 12.5

[0105] The alloy components of the embodiments and comparative examples are shown in Table 1, and the process conditions of the preparation method are shown in Table 2.

[0106] The aluminum alloy obtained through the above steps is subjected to room temperature tensile test of metal materials in accordance with the national standard GB / T228.1-2010, and the room temperature mechanical properties of the alloy are shown in Table 3. The mechanical properties comparison results of Examples 1-4 and Comparative Examples 1-2 are as follows:

[0107] Tensile strength: Example 1> Example 4> Example 3> Example 2> Example 5> Comparative Example 2> Comparative Example 1.

[0108] Yield strength: Example 1> Example 4> Example 2> Example 3> Example 5> Comparative Example 2> Comparative Example 1.

[0109] Elongation after break: Example 1> Example 4> Example 2> Example 3> Example 5> Comparative Example 2> Comparative Example 1.

[0110] The examples adopt the preparation method of the present invention, while comparative example 1 adopts an extrusion casting process and comparative example 2 adopts a gravity casting and forging composite process.

[0111] Example 1 and Comparative Example 1 use the same alloy components but different preparation processes. The material properties of the aluminum alloy prepared are compared, and Example 1 is better. It can be concluded that in order to obtain better tensile strength, yield strength and elongation after fracture, the preparation method of the present invention is better than the squeeze casting process.

[0112] Example 2 and Comparative Example 2 use the same alloy components but different preparation processes. The material properties of the aluminum alloy prepared are compared, and Example 2 is better. It can be concluded that in order to obtain better material properties of tensile strength, yield strength and elongation after fracture, the preparation method of the present invention is superior to the gravity casting and forging composite process.

[0113] By comparing Examples 1-5 with Comparative Examples 1-2, it can be seen from the mechanical properties data of the aluminum alloy that the mechanical properties of the embodiments are better than those of the comparative examples as a whole. It can be concluded that in order to obtain better material properties of tensile strength, yield strength and elongation after fracture, the preparation method of the present invention is better than the extrusion casting process and gravity casting and forging composite process of the prior art.

[0114] like Figure 1 , Figure 2 As shown, the metallographic structure of the aluminum alloy product of Example 1-2 can be observed to have obvious forging streamlines. Figure 3 As shown, the aluminum alloy metallographic structure prepared by the squeeze casting process of the prior art in Comparative Example 1 is a typical casting structure, and the grain size is 10 to 25 μm. Figure 4 As shown, there are some shrinkage defects in the metallographic structure of the aluminum alloy prepared by the gravity casting and forging composite process in comparative example 2, and the grain size is 60-120 μm. The smaller the lattice size of the aluminum alloy, the better the mechanical properties. It can be concluded that from the perspective of the grain size of the metallographic structure casting streamline, shrinkage defects, etc., the preparation method of the present invention is superior to the squeeze casting process and the gravity casting and forging composite process of the prior art.

[0115] like Figure 5 As shown in the SEM microstructure photo of the aluminum alloy of Example 2, the Al2Cu precipitated phase is distributed at the grain boundary. After forging, the Al2Cu phase is distributed in long strips along the forging streamline. Part of the Al2Cu phase is broken and reduced in size, and the structure becomes more dense. After the solid solution treatment, part of the Al2Cu phase dissolves back into the aluminum matrix to form a supersaturated solid solution, which precipitates as a strengthening phase in the subsequent aging process to improve the mechanical properties of the alloy. Figure 6 As shown in the SEM microstructure photo of the aluminum alloy prepared by the gravity casting and forging process in the prior art of Comparative Example 2, after forging, the Al2Cu phase is distributed in long strips along the forging streamline, and some Al2Cu phases are broken, but gravity casting causes the alloy grain size to be larger, and there are impurities on the alloy surface. It can be concluded that from the perspective of grain size and surface impurities of the SEM microstructure casting streamline, the preparation method of the present invention is superior to the gravity casting and forging composite process of the prior art.

[0116] From the multi-dimensional comparison of the material properties of tensile strength, yield strength and elongation after fracture of the aluminum alloys prepared in the embodiments and comparative examples, the metallographic structure casting and forging streamlines and SEM structure casting and forging streamlines, the consistency of the data comparison results shows that compared with the extrusion casting process and gravity casting and forging composite process of the prior art, the preparation method of the present invention is superior.

[0117] In comparison between Example 1 and Example 2, the aluminum alloy material prepared in Example 1 has better performance under the same preparation conditions despite different aluminum alloy component contents. It can be concluded that in order to obtain better material properties of tensile strength, yield strength and elongation after fracture, Example 1 is superior to Example 2 in terms of alloy component content selection.

[0118] In comparison between Example 1 and Example 3, the aluminum alloy components have the same content but the process conditions of S3 extrusion casting in the preparation method are different. The material properties of the prepared aluminum alloy are compared, and Example 1 is better. It is concluded that in order to obtain better material properties of tensile strength, yield strength and elongation after fracture, the process conditions of extrusion casting are further preferably as follows: aluminum liquid temperature is 690°C, mold temperature is 260°C, injection speed is 0.1m / s, injection force is 120MPa, and injection time is 15s.

[0119] In comparison between Example 1 and Example 4, the aluminum alloy components have the same content but the S4 forging process conditions in the preparation method are different. The material properties of the prepared aluminum alloy are compared, and Example 1 is better. It is concluded that in order to obtain better material properties of tensile strength, yield strength and elongation after fracture, the forging process conditions are further preferably selected, that is, forging temperature 460°C, die temperature 450°C, deformation 70%, first stage forging speed 15mm / s, second stage forging speed 1mm / s, and holding time 10s.

[0120] Compared with Example 1, Example 5 has the same content of aluminum alloy components but different process conditions of S5 forging in the preparation method, and the mechanical properties of the aluminum alloy prepared in Example 5 do not reach the level required by the present invention. Therefore, it can be concluded that the aluminum alloy prepared in Example 5, which is not implemented according to the process conditions of the preparation method of the present invention, does not reach the mechanical properties level required by the present invention.

[0121] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A high-strength, high-toughness and high-plasticity aluminum alloy, characterized in that: The components of the aluminum alloy include, by mass percentage: 4.3%<Cu≤4.6%, Mg 0.9~1.4%, Mn 0.7~1.0%, Cr 0.1~0.2%, Ti 0.1~0.15%, B 0.01~0.1%, impurities≤0.15%, and the balance is Al; The method for preparing the high-strength, high-toughness and high-plasticity aluminum alloy comprises: S1: batching, weighing raw materials according to the mass percentage of each element in the aluminum alloy; S2: melting the raw materials to obtain aluminum alloy molten liquid; S3: Squeeze casting, the process conditions are aluminum liquid temperature of 680-700℃, mold temperature of 230-280℃, injection speed of 0.04-0.5m / s, injection force of 100-150MPa, and injection time of 10-15s; S4: homogenization annealing, the process conditions are 400℃~450℃ for 6~10h, then heating to 480~520℃ for 10~24h, and then cooling with the furnace; S5: Forging, forging temperature 450~470℃, die temperature 400~450℃, control the first stage forging speed 10~20mm / s, the second stage forging speed 1~5mm / s, holding time 5~10s, control the deformation amount 70~80%; S6: Solution aging treatment, 490-520℃ for 1-10h to form a supersaturated solid solution, followed by water quenching at room temperature to form a supersaturated solid solution; cooling to 150-170℃ for 10-24h to precipitate the strengthening phase, followed by air cooling; The aluminum alloy has a tensile strength of 461-480 MPa, a yield strength of 340-360 MPa, and an elongation after fracture of 14-16%.

2. The casting and forging composite preparation method of a high-strength, toughness and high-plasticity aluminum alloy according to claim 1, characterized in that: The preparation method comprises: S1: ingredients; S2: smelting to obtain aluminum alloy molten liquid; S3: Squeeze casting, the process conditions are aluminum liquid temperature of 680-700℃, mold temperature of 230-280℃, injection speed of 0.04-0.5m / s, injection force of 100-150MPa, and injection time of 10-15s; S4: homogenization annealing, the process conditions are 400℃~450℃ for 6~10h, then heating to 480~520℃ for 10~24h, and then cooling with the furnace; S5: Forging, forging temperature 450~470℃, die temperature 400~450℃, control the first stage forging speed 10~20mm / s, the second stage forging speed 1~5mm / s, holding time 5~10s, control the deformation amount 70~80%; S6: Solution aging treatment, keep at 490-520℃ for 1-10h to form a supersaturated solid solution, then quench in water at room temperature to form a supersaturated solid solution; cool to 150-170℃ for 10-24h to precipitate the strengthening phase, then air cool.

3. The casting and forging composite preparation method of a high-strength, toughness and high-plasticity aluminum alloy according to claim 2, characterized in that S2 comprises: After pure Al is melted at 750-800°C, Al-60Cu master alloy, Al-10Mn master alloy and Al-4Cr master alloy are added in sequence, all of which are melted and kept warm to obtain a primary smelting liquid; The primary smelting liquid is cooled to 690-730°C, pure Mg wrapped in aluminum foil and Al-5Ti-1B refiner are added, all are melted, stirred, and kept warm to obtain a secondary smelting liquid; Add a deslagging agent to the secondary smelting liquid to keep it warm, and introduce argon gas for refining and degassing, cool it to 690-710°C, let it stand for 30-60 minutes, and skim the slag to obtain the tertiary smelting liquid.

4. The casting and forging composite preparation method of a high-strength, toughness and high-plasticity aluminum alloy according to claim 2 is characterized in that, in S3, the process conditions of extrusion casting are: aluminum liquid temperature 680~700°C, mold temperature 230~280°C, injection speed 0.04~0.2m / s, injection force 100~150MPa, and injection time 10~15s.

5. The casting and forging composite preparation method of a high-strength, toughness and high-plasticity aluminum alloy according to claim 4 is characterized in that, in S3, the aluminum liquid temperature is 680°C, the mold temperature is 280°C, the injection speed is 0.2m / s, and the injection force is 150MPa.

6. The casting and forging composite preparation method of a high-strength, toughness and high-plasticity aluminum alloy according to claim 2 is characterized in that, in S4, the process conditions of homogenization annealing are: keeping at 400℃~450℃ for 6~10h, then heating to 480℃~520℃ for 10~20h, and cooling with the furnace.

7. The casting and forging composite preparation method of a high-strength, toughness and high-plasticity aluminum alloy according to claim 2 is characterized in that, in S5, the forging process conditions are: forging temperature 450~470℃, mold temperature 400~450℃, deformation 70~80%, first-stage forging speed 15~20mm / s, second-stage forging speed 1~5mm / s, and holding time 5~10s.

8. The casting and forging composite preparation method of a high-strength, toughness and high-plasticity aluminum alloy according to claim 7, characterized in that, in S5, the forging temperature is 450-460°C, the mold temperature is 400-450°C, and the deformation is 70%.

9. The casting and forging composite preparation method of a high-strength, toughness and high-plasticity aluminum alloy according to claim 2 is characterized in that, in S6, the temperature is kept at 500-520°C for 2-10 hours to form a supersaturated solid solution, followed by water quenching at room temperature; the temperature is lowered to 160-170°C and kept for 12-24 hours to precipitate a crystal phase by aging, followed by air cooling.

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