Microalloying materials, heat treatment technology and application of cast Al-Cu alloy for engine

Abstract

The present invention discloses a microalloying material, a heat treatment process and an application of a cast Al-Cu alloy for an engine, and belongs to the technical field of aluminum alloys. The microalloying material comprises the following components: Cu: 3-6wt%, Mn: 0.4-0.8wt%, Ti: 0.1-0.5wt%, La: 0.1-0.5wt%, Zr: 0.1-0.3wt%, Sc: 0.1-0.3wt%, Er: 0.1-0.3wt%, Fe≤0.10wt%, and the balance is Al. The microalloying material of the present invention has a hardness greater than 159HV at room temperature, a yield strength greater than 359MPa, and a tensile strength greater than 469MPa. At a temperature of 400°C, the yield strength is greater than 109MPa, the tensile strength is greater than 128.6MPa, and the heat resistance is greatly improved, which solves the technical defects of poor mechanical properties and poor heat resistance of traditional Al-Cu alloy materials.

Description

Technical Field

[0001] The invention relates to a microalloying material of a cast Al-Cu alloy for an engine, a heat treatment process and an application thereof, and belongs to the technical field of aluminum alloys. Background Art

[0002] Aluminum is the most abundant metal element in the earth's crust, and it has the advantages of low density and high specific strength. Aluminum alloys formed by alloying have good toughness, fatigue resistance, and corrosion resistance, and are widely used in the automotive and aerospace fields. With the increase in the requirements for high power density and fuel economy of engines, the upper temperature limit of heat-resistant aluminum alloys has been increased from the traditional 300°C to above 400°C. Therefore, the development of high-temperature heat-resistant aluminum alloys has become one of the hot spots in aluminum alloy research and development. On the other hand, due to the complexity of the structural design of engine components, the forming process mostly requires casting, so the development of cast heat-resistant aluminum alloys has become an important aspect, but its low high-temperature strength has largely limited its further application in the fields of engine manufacturing. Therefore, synergistically improving the high-temperature strength and toughness of cast Al-Cu alloys is a key issue in the development of lightweight engines.

[0003] Al-Cu heat-resistant alloys have a long history of research and development and are widely used in the aerospace field, but their shortcomings are poor heat resistance and corrosion resistance [Fu Junwei, Cui Kai, Wang Jiangchun. Research progress of Al-Cu heat-resistant aluminum alloys [J]. The Chinese Journal of Nonferrous Metals, 2021, 31(07): 1827-1841.].

[0004] With the advancement of science and technology and the continuous improvement of people's living standards, the number of cars has increased year by year, leading to increasingly severe energy and environmental problems. Promoting the development of lightweight cars has become an important trend in the development of the current automotive industry. Aluminum alloys for automobile engines have the problem of difficulty in matching strength and high-temperature heat resistance. How to improve the strength and toughness of aluminum alloys is the key to the development of high-performance aluminum alloys for automobile engines, and it is also a key means to promote lightweight cars. Summary of the invention

[0005] The technical problem to be solved by the present invention is that the present invention provides a micro-alloyed material of cast Al-Cu alloy for engine, which solves the problem that the strength and high temperature heat resistance of Al-Cu alloy for automobile engine are difficult to improve synergistically through micro-alloying of cast Al-Cu alloy.

[0006] At the same time, the present invention provides a heat treatment process for a microalloyed material of a cast Al-Cu alloy for an engine, which improves the comprehensive performance of the Al-Cu alloy, synergistically improves the strength and toughness of the Al-Cu alloy, and solves the technical defect of poor mechanical properties of traditional Al-Cu alloy materials.

[0007] At the same time, the present invention provides an application of a micro-alloyed material of a cast Al-Cu alloy for an engine as a lightweight material for an automobile engine in the automobile field.

[0008] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0009] The microalloying material of cast Al-Cu alloy for engine includes the following components: Cu: 3-6wt%, Mn: 0.4-0.8wt%, Ti: 0.1-0.5wt%, La: 0.1-0.5wt%, Zr: 0.1-0.3wt%, Sc: 0.1-0.3wt%, Er: 0.1-0.3wt%, Fe≤0.10wt%, and the balance is Al.

[0010] Preferably, the ratio of Sc to Zr is (1-1.25):1.

[0011] Preferably, the microalloyed material has a hardness greater than 159 HV, a yield strength greater than 359 MPa, and a tensile strength greater than 469 MPa at room temperature; the microalloyed material has a yield strength greater than 109 MPa and a tensile strength greater than 128.6 MPa at 400°C.

[0012] The heat treatment process of the microalloyed material of the cast Al-Cu alloy for engine comprises the following steps:

[0013] S1, firstly, the Al-Cu alloy is placed in an air furnace at 530-550°C for a first-stage solid solution treatment for 4-6 hours; then, the alloy is placed in an air furnace at 580-600°C for a second-stage solid solution treatment for 2-4 hours to obtain a solid solution treated Al-Cu alloy;

[0014] S2, quenching: the solution treated Al-Cu alloy is quickly taken out from the air furnace and placed in water for cooling. The quenching medium is 55-65°C water.

[0015] S3, regression and re-aging: the Al-Cu alloy after water quenching is placed in an air furnace for insulation at 340-360°C for 6-10 hours, and then subjected to regression treatment, the alloy is placed in an air furnace for insulation at 530-550°C for 20-50 minutes, and finally subjected to re-aging treatment, the Al-Cu alloy after regression treatment is quenched, the Al-Cu alloy after regression treatment is quickly taken out from the air furnace, and placed in water for cooling, the quenching medium is 55-65°C water, and the Al-Cu alloy after water quenching is placed in an air furnace for insulation at 340-360°C for 6-12 hours.

[0016] Preferably, in S1, a two-stage solution treatment is adopted, and the air contact time during the two air furnace transfer processes is less than 1 minute.

[0017] Preferably, in S1, after the air furnace is heated to 530-550°C, it is kept warm for 5-10 minutes until the furnace temperature stabilizes, and then the Al-Cu alloy is put in for the first-level solid solution treatment; after the air furnace is heated to 580-600°C, it is kept warm for 5-10 minutes until the furnace temperature stabilizes, and then the Al-Cu alloy that has undergone the first-level solid solution treatment is put in for the second-level solid solution treatment.

[0018] Preferably, in S2, the transfer time of the solution treated Al-Cu alloy from the air furnace to the water is less than 10 seconds, and the quenching time is 1 to 3 minutes.

[0019] Preferably, in S3, the time for removing water stains from the Al-Cu alloy after quenching and transferring it to the air furnace should be controlled within 1 to 3 minutes to avoid natural aging.

[0020] Preferably, in S3, after the aging treatment is completed, the product is placed in air to cool to room temperature.

[0021] Preferably, in S3, the air furnace needs to be heated to the target starting temperature in advance and kept warm for 5 to 10 minutes until the furnace temperature stabilizes, thereby reducing the waiting time for the quenched alloy to be transferred to the furnace.

[0022] Microalloyed materials of cast Al-Cu alloys for engines are used as lightweight materials for engines in the automotive field.

[0023] The micro-alloyed material of cast Al-Cu alloy for engine has a hardness greater than 159HV at room temperature, and can reach a maximum of 167.1HV; the yield strength is greater than 359MPa, and can reach a maximum of 371.5MPa; the tensile strength is greater than 469.3MPa, and can reach a maximum of 482.1MPa; and the elongation can reach more than 8%. Compared with the Al-Cu alloy without micro-alloying and regression treatment, the hardness and yield strength can be increased by 14.4% and 20% respectively; and the yield strength at 400°C is greater than 109.7MPa, the tensile strength is greater than 128.6MPa, and the heat resistance is greatly improved.

[0024] The present invention can improve the high temperature performance of the cast Al-Cu alloy by microalloying the cast Al-Cu alloy. Aluminum-based intermetallic compounds (forming new dispersion strengthening phases) can be obtained by adding a certain amount of transition metals and rare earth elements into the aluminum alloy, which can effectively promote grain refinement and improve the organizational structure of the alloy, thereby increasing the high temperature strength.

[0025] Al-Cu-Mn alloys are highly strong and lightweight, so they are widely used in the automotive and aircraft industries. Al-Cu alloys with the addition of Mn elements can form a strengthening phase T (Al 12 CuMn 12) can improve the heat resistance of the material and the casting performance of the material. Since Fe element acts as an impurity in the production process, it will reduce the mechanical properties of the alloy. Mn and Fe form (FeMn)3SiAl 12 It has almost no effect on the toughness of the alloy and can eliminate the influence of Fe on the mechanical properties of the alloy.

[0026] Adding Ti element can greatly improve the fatigue resistance and mechanical properties of the alloy.

[0027] The grain refinement phenomenon is more obvious after adding La element.

[0028] Adding Zr, Zr and Al form Al3Zr compounds, which can refine the cast grains of the alloy on the one hand; on the other hand, it can inhibit the recrystallization effect during hot working and increase the recrystallization temperature, thereby improving the mechanical properties, heat resistance, weldability and weld plasticity of the alloy.

[0029] Adding trace amounts of Sc to aluminum-copper alloys promotes the precipitation of coherent Al3Sc phase in Al-based alloys, which can strongly pin dislocations and grain boundaries, stabilize the substructure of the alloy, significantly refine the grains, improve the alloy's strength, plasticity, corrosion resistance, weldability, and reduce thermal crack sensitivity.

[0030] The present invention comprehensively adds Mn, Ti, La, Zr, Sc, and Er elements to form a strengthening phase T (Al 12 CuMn 12 ) and θ′-Al2Cu jointly improve the strength of the alloy. θ′-Al2Cu is easy to coarsen at 300℃, but the combined addition of Zr and Sc will delay the decomposition of the supersaturated solid solution and slow down the coarsening of the hardened particles. Since Sc in the Al3Sc phase is partially replaced by Zr, Al3(Sc, Zr) phase or composite particles with Al3Sc core and Zr-rich shell are formed. The diffusion coefficients of Er and Sc are similar. It can be expected that a core-shell Al3(Er, Zr) phase similar to the Al3(Sc, Zr) phase will be formed during the aging treatment. The shell of the slowly diffusing Zr acts as a barrier to the atomic transport required for particle growth, slowing down the coarsening process, thereby ensuring that the peak hardness of the alloy is maintained for a certain period of time.

[0031] The regression treatment process of the present invention ensures the strength and thermal stability of the alloy at high temperatures by re-solidifying the θ′-Al2Cu in the alloy into the matrix during artificial aging, and precipitating high temperature resistant phases such as Al3Sc, Al3(Sc, Zr), and Al3Zr. The high temperature resistant clusters formed in the subsequent regression re-aging process can serve as heterogeneous nucleation points of the θ′ phase. The regression treatment can well prevent the coarsening of the θ′ phase during the aging process, and prepare enough Cu atoms for the subsequent re-aging.

[0032] The present invention has the following beneficial effects:

[0033] 1. Microalloying of Al-Cu alloy is to add transition metals and rare earth metal elements to Al-Cu alloy. By adding transition metals and rare earth metal elements, the precipitation of strengthening phase under high temperature conditions of aluminum alloy can be effectively controlled, thereby improving its high temperature mechanical properties. After adding Mn element to Al-Cu alloy, strengthening phase T (Al 12 CuMn 12 ) can improve the heat resistance of the material, and Mn can form (FeMn)3SiAl with impurity Fe 12 , reducing the influence of harmful impurity Fe on alloy properties. The addition of Ti can form A13Ti as a common strengthening phase in aluminum-based composite materials, which has good high temperature resistance, and the addition of Ti also plays a role in refining grains and hindering grain boundary sliding. Continuing to add La elements in the alloy can form Al 20 Ti2La phase can act as a heterogeneous nucleation site to promote heterogeneous nucleation. Zr, Sc, and Er are also common microalloying elements. While forming Al3Zr and Al3Sc to pin dislocations and stabilize the substructure of the alloy, the combined addition of Zr and Sc will delay the decomposition of the supersaturated solid solution and slow down the coarsening of the hardened particles. Since Sc in the Al3Sc phase is partially replaced by Zr, an Al3(Sc,Zr) phase or a composite particle with an Al3Sc core and a Zr-rich shell is formed, which is a core-shell structured precipitation. Er and Sc have similar diffusion coefficients. It can be expected that a core-shell Al3(Er,Zr) phase similar to the Al3(Sc,Zr) phase will be formed during the aging treatment. The slowly diffusing Zr shell acts as a barrier to the atomic transport required for particle growth, slowing down the coarsening process, thereby ensuring that the peak hardness of the alloy is maintained for a certain period of time. After adding trace amounts of alloys, a strengthening phase with high heat resistance is formed in the alloy. Under the synergistic effect of these elements, the grain size changes significantly. While the grain size is reduced, the high-temperature mechanical properties of the alloy are improved, and the strength, plasticity, corrosion resistance and heat resistance are all improved.

[0034] 2. Accompanied by the two-stage solid solution and regression re-aging process, the coarsening rate of the θ′-Al2Cu phase is synergistically controlled, and more high-temperature resistant phases are precipitated at the same time, so that the heat resistance temperature of the alloy is increased from 200°C to above 400°C.

[0035] 3. Artificial aging process is an aging process that keeps the temperature at a certain temperature for a certain period of time. This heat treatment process controls the temperature and then finely regulates the organization to obtain good comprehensive performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a microstructure diagram of the Al3(Sc,Zr) core-shell structure of the present invention;

[0037] Figure 2 This is the elemental analysis diagram of the Al3(Sc,Zr) core-shell structure precipitate of the present invention. DETAILED DESCRIPTION

[0038] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0039] Comparative Example 1 (the difference from the present invention is that the Al-Cu alloy lacks La, Zr, Sc and Er)

[0040] A heat treatment process for a microalloyed material of a cast Al-Cu alloy for an engine comprises the following steps:

[0041] S1: First, the Al-Cu alloy is placed in an air furnace at 540°C for a first-stage solid solution treatment for 5 hours, and then the alloy is placed in an air furnace at 590°C for a second-stage solid solution treatment for 3 hours. The specific composition of the Al-Cu alloy is: Cu: 4.8wt%, Mn: 0.5wt%, Ti: 0.3wt%, Fe≤0.10wt%, and the balance is Al.

[0042] S2: The solution treated Al-Cu alloy is quickly taken out from the air furnace and placed in 60°C water for cooling. The transfer time of the alloy from the furnace to the water is less than 10s, and the quenching time is 1min.

[0043] S3: After water quenching, the Al-Cu alloy is heat treated by artificial aging (350℃*6h), and then the alloy is placed in an air furnace at 540℃ for regression treatment for 30min; the Al-Cu alloy after regression treatment is quenched, and the Al-Cu alloy after regression treatment is quickly taken out from the air furnace and placed in 60℃ water for cooling. The transfer time of the alloy from the furnace to the water is less than 10s, and the quenching time is 1min. Finally, regression re-aging (350℃*8h) is performed. After aging, it is placed in air to cool to room temperature.

[0044] Comparative Example 2 (the only difference from the present invention is that the Al-Cu alloy lacks Zr, Sc and Er)

[0045] A heat treatment process for a microalloyed material of a cast Al-Cu alloy for an engine comprises the following steps:

[0046] S1: First, the Al-Cu alloy is placed in an air furnace at 540°C for a first-stage solid solution treatment for 5 hours, and then the alloy is placed in an air furnace at 590°C for a second-stage solid solution treatment for 3 hours. The specific composition of the Al-Cu alloy is: Cu: 5wt%, Mn: 0.6wt%, Ti: 0.3wt%, La: 0.38wt%, Fe≤0.10wt%, and the balance is Al.

[0047] S2: The solution treated Al-Cu alloy is quickly taken out from the air furnace and placed in 60°C water for cooling. The transfer time of the alloy from the furnace to the water is less than 10s, and the quenching time is 1min.

[0048] S3: After water quenching, the Al-Cu alloy is heat treated by artificial aging (350℃*6h), and then the alloy is placed in an air furnace at 540℃ for regression treatment for 30min; the Al-Cu alloy after regression treatment is quenched, and the Al-Cu alloy after regression treatment is quickly taken out from the air furnace and placed in 60℃ water for cooling. The transfer time of the alloy from the furnace to the water is less than 10s, and the quenching time is 1min. Finally, regression re-aging (350℃*8h) is performed. After aging, it is placed in air to cool to room temperature.

[0049] Comparative Example 3 (the only difference from the present invention is that the Al-Cu alloy lacks Sc and Er)

[0050] A heat treatment process for a microalloyed material of a cast Al-Cu alloy for an engine comprises the following steps:

[0051] S1: First, the Al-Cu alloy is placed in an air furnace at 540°C for a first-stage solid solution treatment for 5 hours, and then the alloy is placed in an air furnace at 590°C for a second-stage solid solution treatment for 3 hours. The specific composition of the Al-Cu alloy is: Cu: 4.8wt%, Mn: 0.6wt%, Ti: 0.3wt%, La: 0.3wt%, Zr: 0.2wt%, Fe≤0.10wt%, and the balance is Al.

[0052] S2: The solution treated Al-Cu alloy is quickly taken out from the air furnace and placed in 60°C water for cooling. The transfer time of the alloy from the furnace to the water is less than 10s, and the quenching time is 1min.

[0053] S3: After water quenching, the Al-Cu alloy is heat treated by artificial aging (350℃*6h), and then the alloy is placed in an air furnace at 540℃ for regression treatment for 30min; the Al-Cu alloy after regression treatment is quenched, and the Al-Cu alloy after regression treatment is quickly taken out from the air furnace and placed in 60℃ water for cooling. The transfer time of the alloy from the furnace to the water is less than 10s, and the quenching time is 1min. Finally, regression re-aging (350℃*8h) is performed. After aging, it is placed in air to cool to room temperature.

[0054] Comparative Example 4 (the difference from the present invention is that the Al-Cu alloy lacks Er, and the ratio of Sc to Zr is 0.67:1)

[0055] A heat treatment process for a microalloyed material of a cast Al-Cu alloy for an engine comprises the following steps:

[0056] S1: First, the Al-Cu alloy is placed in an air furnace at 540°C for a first-stage solid solution treatment for 5 hours, and then the alloy is placed in an air furnace at 590°C for a second-stage solid solution treatment for 3 hours. The specific composition of the Al-Cu alloy is: Cu: 5wt%, Mn: 0.7wt%, Ti: 0.3wt%, La: 0.3wt%, Zr: 0.3wt%, Sc: 0.2wt%, Fe≤0.10wt%, and the balance is Al.

[0057] S2: The solution treated Al-Cu alloy is quickly taken out from the air furnace and placed in 60°C water for cooling. The transfer time of the alloy from the furnace to the water is less than 10s, and the quenching time is 1min.

[0058] S3: After water quenching, the Al-Cu alloy is heat treated by artificial aging (350℃*6h), and then the alloy is placed in an air furnace at 540℃ for regression treatment for 30min; the Al-Cu alloy after regression treatment is quenched, and the Al-Cu alloy after regression treatment is quickly taken out from the air furnace and placed in 60℃ water for cooling. The transfer time of the alloy from the furnace to the water is less than 10s, and the quenching time is 1min. Finally, regression re-aging (350℃*8h) is performed. After aging, it is placed in air to cool to room temperature.

[0059] Comparative Example 5 (the only difference from the present invention is that the ratio of Sc to Zr in the composition of the Al-Cu alloy is 1.33:1)

[0060] A heat treatment process for a microalloyed material of a cast Al-Cu alloy for an engine comprises the following steps:

[0061] S1: First, the Al-Cu alloy is placed in an air furnace at 540°C for a first-stage solid solution treatment for 5 hours, and then the alloy is placed in an air furnace at 590°C for a second-stage solid solution treatment for 3 hours. The specific composition of the Al-Cu alloy is: Cu: 5wt%, Mn: 0.7wt%, Ti: 0.3wt%, La: 0.38wt%, Zr: 0.15wt%, Sc: 0.2wt%, Er: 0.1wt%, Fe≤0.10wt%, and the balance is Al.

[0062] S2: The solution treated Al-Cu alloy is quickly taken out from the air furnace and placed in 60°C water for cooling. The transfer time of the alloy from the furnace to the water is less than 10s, and the quenching time is 1min.

[0063] S3: After water quenching, the Al-Cu alloy is heat treated by artificial aging (350℃*6h), and then the alloy is placed in an air furnace at 540℃ for regression treatment for 30min; the Al-Cu alloy after regression treatment is quenched, and the Al-Cu alloy after regression treatment is quickly taken out from the air furnace and placed in 60℃ water for cooling. The transfer time of the alloy from the furnace to the water is less than 10s, and the quenching time is 1min. Finally, regression re-aging (350℃*8h) is performed. After aging, it is placed in air to cool to room temperature.

[0064] Comparative Example 6 (the only difference from the present invention is that no regression treatment and regression re-aging were performed)

[0065] A heat treatment process for a microalloyed material of a cast Al-Cu alloy for an engine comprises the following steps:

[0066] S1: First, the Al-Cu alloy is placed in an air furnace at 540°C for a first-stage solid solution treatment for 5 hours, and then the alloy is placed in an air furnace at 590°C for a second-stage solid solution treatment for 3 hours. The specific composition of the Al-Cu alloy is: Cu: 4.8wt%, Mn: 0.7wt%, Ti: 0.5wt%, La: 0.1wt%, Zr: 0.1wt%, Sc: 0.1wt%, Er: 0.15wt%, Fe≤0.10wt%, and the balance is Al.

[0067] S2: The solution treated Al-Cu alloy is quickly taken out from the air furnace and placed in 60°C water for cooling. The transfer time of the alloy from the furnace to the water is less than 10s, and the quenching time is 1min.

[0068] S3: After water quenching, the Al-Cu alloy is heat treated by artificial aging (350℃*16h). After aging, it is placed in air to cool to room temperature.

[0069] Comparative Example 7 (the only difference from the present invention is that no two-stage solution treatment is performed)

[0070] A heat treatment process for a microalloyed material of a cast Al-Cu alloy for an engine comprises the following steps:

[0071] S1: First, the Al-Cu alloy is placed in an air furnace at 540°C for solution treatment for 8 hours. The specific composition of the Al-Cu alloy is: Cu: 4.5wt%, Mn: 0.6wt%, Ti: 0.2wt%, La: 0.5wt%, Zr: 0.1wt%, Sc: 0.1wt%, Er: 0.18wt%, Fe≤0.10wt%, and the balance is Al.

[0072] S2: The solution treated Al-Cu alloy is quickly taken out from the air furnace and placed in 60°C water for cooling. The transfer time of the alloy from the furnace to the water is less than 10s, and the quenching time is 1min.

[0073] S3: After water quenching, the Al-Cu alloy is heat treated by artificial aging (350℃*6h). Then the alloy is placed in an air furnace at 540℃ for regression treatment for 30min; the Al-Cu alloy after regression treatment is quenched, and the Al-Cu alloy after regression treatment is quickly taken out from the air furnace and placed in 60℃ water for cooling. The transfer time of the alloy from the furnace to the water is less than 10s, and the quenching time is 1min. Finally, regression re-aging (350℃*8h) is performed. After aging, place it in the air to cool to room temperature. After aging, place it in the air to cool to room temperature.

[0074] Example 1

[0075] A heat treatment process for a microalloyed material of a cast Al-Cu alloy for an engine comprises the following steps:

[0076] S1: First, the Al-Cu alloy is placed in an air furnace at 538°C for a first-stage solid solution treatment for 5 hours, and then the alloy is placed in an air furnace at 581°C for a second-stage solid solution treatment for 3 hours. The specific composition of the Al-Cu alloy is: Cu: 5.5wt%, Mn: 0.55wt%, Ti: 0.35wt%, La: 0.2wt%, Zr: 0.1wt%, Sc: 0.1wt%, Er: 0.2wt%, Fe≤0.10wt%, and the balance is Al.

[0077] The ratio of Sc to Zr is 1:1.

[0078] S2: The solution treated Al-Cu alloy is quickly taken out from the air furnace and placed in 59°C water for cooling. The transfer time of the alloy from the furnace to the water is less than 10s, and the quenching time is 1min.

[0079] S3: After water quenching, the Al-Cu alloy is heat treated by artificial aging (352℃*6h), and then the alloy is placed in an air furnace at 538℃ for regression treatment for 30min; the Al-Cu alloy after regression treatment is quenched, and the Al-Cu alloy after regression treatment is quickly taken out from the air furnace and placed in 59℃ water for cooling. The transfer time of the alloy from the furnace to the water is less than 10s, and the quenching time is 1min. Finally, regression re-aging (352℃*8h) is performed. After aging, it is placed in air to cool to room temperature.

[0080] In S1, after the air furnace is heated to 538°C, it is kept at this temperature for 5 minutes until the furnace temperature stabilizes, and then the Al-Cu alloy is put in for the first-stage solid solution treatment. After the air furnace is heated to 581°C, it is kept at this temperature for 5 minutes until the furnace temperature stabilizes, and then the Al-Cu alloy that has undergone the first-stage solid solution treatment is put in for the second-stage solid solution treatment.

[0081] In S1, a two-stage solution treatment was used, and the air contact time during the two air furnace transfers was less than 1 min.

[0082] In S3, the time for removing water stains from the Al-Cu alloy after quenching and transferring it to the air furnace must be controlled within 1 min to avoid natural aging.

[0083] In S3, the air furnace needs to be heated to the target starting temperature of 538°C in advance and kept warm for 5 min until the furnace temperature stabilizes, thus reducing the waiting time for the quenched alloy to be transferred to the furnace.

[0084] The microalloyed material and heat treatment process of the cast Al-Cu alloy for engine obtained in this embodiment are used as lightweight materials for engines in the automotive field.

[0085] Example 2

[0086] A heat treatment process for a microalloyed material of a cast Al-Cu alloy for an engine comprises the following steps:

[0087] S1: First, the Al-Cu alloy is placed in an air furnace at 530°C for a first-stage solid solution treatment for 4 hours, and then the alloy is placed in an air furnace at 600°C for a second-stage solid solution treatment for 2 hours. The specific composition of the Al-Cu alloy is: Cu: 3wt%, Mn: 0.8wt%, Ti: 0.1wt%, La: 0.1wt%, Zr: 0.16wt%, Sc: 0.2wt%, Er: 0.1wt%, Fe≤0.10wt%, and the balance is Al.

[0088] The ratio of Sc to Zr is 1.25:1.

[0089] S2: The solution treated Al-Cu alloy is quickly taken out from the air furnace and placed in 55°C water for cooling. The transfer time of the alloy from the furnace to the water is less than 10s, and the quenching time is 3min.

[0090] S3: After water quenching, the Al-Cu alloy is heat treated by artificial aging (360℃*8h), and then the alloy is placed in an air furnace at 530℃ for regression treatment for 20min; the Al-Cu alloy after regression treatment is quenched, and the Al-Cu alloy after regression treatment is quickly taken out from the air furnace and placed in 55℃ water for cooling. The transfer time of the alloy from the furnace to the water is less than 10s, and the quenching time is 3min. Finally, regression re-aging (360℃*6h) is performed. After aging, it is placed in air to cool to room temperature.

[0091] In S1, after the air furnace is heated to 530°C, it is kept warm for 10 minutes until the furnace temperature stabilizes, and then the Al-Cu alloy is put in for the first-level solid solution treatment. After the air furnace is heated to 600°C, it is kept warm for 10 minutes until the furnace temperature stabilizes, and then the Al-Cu alloy that has undergone the first-level solid solution treatment is put in for the second-level solid solution treatment.

[0092] In S1, a two-stage solution treatment was used, and the air contact time during the two air furnace transfers was less than 1 min.

[0093] In S3, the time for removing water stains from the Al-Cu alloy after quenching and transferring it to the air furnace must be controlled within 3 min to avoid natural aging.

[0094] In S3, the air furnace needs to be heated to the target starting temperature of 530°C in advance and kept warm for 10 min until the furnace temperature stabilizes, thus reducing the waiting time for the quenched alloy to be transferred to the furnace.

[0095] The microalloyed material and heat treatment process of the cast Al-Cu alloy for engine obtained in this embodiment are used as lightweight materials for engines in the automotive field.

[0096] Example 3

[0097] A heat treatment process for a microalloyed material of a cast Al-Cu alloy for an engine comprises the following steps:

[0098] S1: First, the Al-Cu alloy is placed in an air furnace at 550°C for a first-stage solid solution treatment for 6 hours, and then the alloy is placed in an air furnace at 580°C for a second-stage solid solution treatment for 4 hours. The specific composition of the Al-Cu alloy is: Cu: 6wt%, Mn: 0.4wt%, Ti: 0.5wt%, La: 0.5wt%, Zr: 0.3wt%, Sc: 0.3wt%, Er: 0.3wt%, Fe≤0.10wt%, and the balance is Al.

[0099] The ratio of Sc to Zr is 1:1.

[0100] S2: The solution treated Al-Cu alloy is quickly taken out from the air furnace and placed in 65°C water for cooling. The transfer time of the alloy from the furnace to the water is less than 10s, and the quenching time is 1min.

[0101] S3: After water quenching, the Al-Cu alloy is heat treated by artificial aging (340℃*10h), and then the alloy is placed in an air furnace at 550℃ for regression treatment for 50min; the Al-Cu alloy after regression treatment is quenched, and the Al-Cu alloy after regression treatment is quickly taken out from the air furnace and placed in 65℃ water for cooling. The transfer time of the alloy from the furnace to the water is less than 10s, and the quenching time is 2min. Finally, regression re-aging (340℃*12h) is performed. After aging, it is placed in air to cool to room temperature.

[0102] In S1, after the air furnace is heated to 550°C, it is kept at this temperature for 7 minutes until the furnace temperature stabilizes, and then the Al-Cu alloy is put in for the first-stage solid solution treatment. After the air furnace is heated to 580°C, it is kept at this temperature for 8 minutes until the furnace temperature stabilizes, and then the Al-Cu alloy that has undergone the first-stage solid solution treatment is put in for the second-stage solid solution treatment.

[0103] In S1, a two-stage solution treatment was used, and the air contact time during the two air furnace transfers was less than 1 min.

[0104] In S3, the time for removing water stains from the Al-Cu alloy after quenching and transferring it to the air furnace should be controlled within 2 min to avoid natural aging.

[0105] In S3, the air furnace needs to be heated to the target starting temperature of 550°C in advance and kept warm for 8 min until the furnace temperature stabilizes, thus reducing the waiting time for the quenched alloy to be transferred to the furnace.

[0106] The microalloyed material and heat treatment process of the cast Al-Cu alloy for engine obtained in this embodiment are used as lightweight materials for engines in the automotive field.

[0107] Performance Testing:

[0108] The alloy samples obtained by different aging processes of the Al-Cu alloys of Comparative Examples 1 to 7 and Examples 1 to 3 were subjected to room temperature hardness performance test, room temperature tensile performance test and 400° C. tensile performance test.

[0109] The test method for room temperature hardness performance is as follows:

[0110] The hardness test was performed using a DHV-1000Z hardness tester with a load of 4.9N and a holding time of 15s. No less than 10 points were taken from the entire surface of each sample to ensure data accuracy, with an error of no more than ±3%.

[0111] The tensile properties test method is as follows:

[0112] The Zwick / Roll Z030TH electronic universal material tensile testing machine was used, and the tensile rate was 1 mm / min. Before the experiment, the workbench of the Zwick / Roll Z030TH electronic universal material tensile testing machine needs to be raised by about 10 mm to eliminate the influence of the deadweight of the workbench system. Each group of experiments is equipped with three parallel samples for comparison to reduce experimental errors. The hardness, room temperature tensile properties and 400°C tensile properties test results of the alloys of Comparative Examples 1 to 7 and Examples 1 to 3 are shown in Table 1.

[0113] Table 1 Hardness, room temperature tensile properties and 400℃ tensile properties test table of alloy

[0114]

[0115]

[0116] It can be seen from the test results in Table 1 that the microalloying treatment has a great influence on the Al-Cu alloy. The heat treatment process provided by the present invention can greatly improve the hardness and strength of the Al-Cu alloy.

[0117] As shown in Table 1, the hardness of the microalloyed Al-Cu alloy at room temperature is greater than 159HV, the yield strength is greater than 359.1MPa, and the tensile strength is greater than 469.3MPa. Compared with the alloy without microalloying treatment and regression and aging treatment, the hardness and yield strength are increased by 14.4% and 20% respectively. At 400℃, the yield strength is greater than 109.7MPa and the tensile strength is greater than 128.6MPa.

[0118] In summary, the present invention improves the performance of the engine casting Al-Cu alloy by microalloying treatment. Therefore, the present invention selects the best microalloying material to make the Al-Cu alloy obtain the highest strength and hardness.

[0119] In summary, the regression and aging heat treatment process can significantly improve the mechanical properties of aluminum alloys. Based on research, microalloying of Al-Cu alloys can promote the precipitation of the strengthening phase of the alloy. By adding a certain amount of transition metals and rare earth elements to synergistically refine the grains and improve the heat resistance of the precipitated phase, the mechanical properties of the alloy are improved. Through the regression and aging process, the coarsening of the θ′-Al2Cu phase is effectively prevented, and some high-temperature resistant phases are precipitated, which greatly improves the mechanical properties and heat resistance of the alloy.

[0120] A microalloying material, a heat treatment process and an application of a cast Al-Cu alloy for an engine are provided to solve the problem that the strength and high temperature heat resistance of the lightweight cast Al-Cu alloy for an engine are difficult to match.

[0121] The addition of Zr and Sc elements, i.e., controlling the specific mass ratio of the two elements, enables the present invention to form Al3Zr and Al3Sc to play the role of pinning dislocations to stabilize the alloy substructure, while the combined addition of Zr and Sc will delay the decomposition of the supersaturated solid solution and slow down the coarsening of the hardened particles. Since Sc in the Al3Sc phase is partially replaced by Zr, an Al3(Sc,Zr) phase or a composite particle having an Al3Sc core and a Zr-rich shell is formed, which is a core-shell structured precipitation, specifically as follows Figure 1 Its elemental analysis diagram is shown in Figure 2 shown.

[0122] Embodiments 1 to 3 of the present invention all obtain high temperature resistant phase precipitation of Al3 (Sc, Zr) core-shell structure, thereby improving the mechanical properties and heat resistance of the alloy; while comparative examples 1 to 7 do not obtain Al3 (Sc, Zr) core-shell structure, so the comparative examples cannot improve the mechanical properties and heat resistance of the alloy.

[0123] It should be understood that in order to streamline the present disclosure and aid in understanding one or more of the various inventive aspects, in the above description of exemplary embodiments of the present invention, various features of the present invention are sometimes grouped together into a single embodiment, figure, or description thereof. However, this disclosed method should not be interpreted as reflecting the intention that the claimed invention requires more features than those expressly recited in each claim. Rather, as reflected in the claims, inventive aspects lie in less than all of the features of the previously disclosed embodiments. Therefore, the claims that follow the detailed description are hereby expressly incorporated into the detailed description, with each claim itself serving as a separate embodiment of the present invention.

[0124] Although the present invention has been described according to a limited number of embodiments, it will be apparent to those skilled in the art, with the benefit of the above description, that other embodiments may be envisioned within the scope of the invention thus described. In addition, it should be noted that the language used in this specification is selected primarily for readability and teaching purposes, rather than for explaining or defining the subject matter of the present invention. Therefore, many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the appended claims. The disclosure of the present invention is illustrative, not restrictive, with respect to the scope of the present invention, which is defined by the appended claims.

[0125] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A heat treatment process for a microalloyed material of a cast Al-Cu alloy for an engine, characterized in that: The composition includes: Cu: 3-6wt%, Mn: 0.4-0.8wt%, Ti: 0.1-0.5wt%, La: 0.1-0.5wt%, Zr: 0.1-0.3wt%, Sc: 0.1-0.3wt%, Er: 0.1-0.3wt%, Fe≤0.10wt%, and the balance is Al; The heat treatment process includes the following steps: S1, firstly, the Al-Cu alloy is placed in an air furnace at 530-550°C for a first-stage solid solution treatment for 4-6 hours; then, the alloy is placed in an air furnace at 580-600°C for a second-stage solid solution treatment for 2-4 hours to obtain a solid solution treated Al-Cu alloy; S2, quenching: the solution treated Al-Cu alloy is quickly taken out from the air furnace and placed in water for cooling. The quenching medium is 55-65℃ water. S3, regression and re-aging: the Al-Cu alloy after water quenching is placed in an air furnace for insulation at 340~360℃ for 6~10h, and then subjected to regression treatment, the alloy is placed in an air furnace for insulation at 530~550℃ for 20~50min, and finally subjected to re-aging treatment, the Al-Cu alloy after regression treatment is quenched, the Al-Cu alloy after regression treatment is quickly taken out from the air furnace, and placed in water for cooling, the quenching medium is 55~65℃ water, and the Al-Cu alloy after water quenching is placed in an air furnace for insulation at 340~360℃ for 6~12h.

2. The heat treatment process of the microalloyed material of the cast Al-Cu alloy for engine according to claim 1, characterized in that: The ratio of Sc to Zr is (1~1.25):

1.

3. The heat treatment process of the microalloyed material of the cast Al-Cu alloy for engine according to claim 1, characterized in that: The hardness of the microalloyed material at room temperature is greater than 159HV, the yield strength is greater than 359MPa, and the tensile strength is greater than 469MPa. The yield strength of the microalloyed material at 400°C is greater than 109MPa, and the tensile strength is greater than 128.6MPa.

4. The heat treatment process according to claim 1, characterized in that: In S1, a two-stage solution treatment was used, and the air contact time during the two air furnace transfers was less than 1 min.

5. The heat treatment process according to claim 1, characterized in that: In S1, after the air furnace is heated to 530~550℃, it is kept warm for 5~10min until the furnace temperature stabilizes, and then the Al-Cu alloy is put in for the first-level solid solution treatment; after the air furnace is heated to 580~600℃, it is kept warm for 5~10min until the furnace temperature stabilizes, and then the Al-Cu alloy that has undergone the first-level solid solution treatment is put in for the second-level solid solution treatment.

6. The heat treatment process according to claim 1, characterized in that: In S2, the transfer time of the solution treated Al-Cu alloy from the air furnace to the water is less than 10 s, and the quenching time is 1 to 3 min.

7. The heat treatment process according to claim 1, characterized in that: In S3, the time for removing water stains from the Al-Cu alloy after quenching and transferring it to the air furnace should be controlled within 1 to 3 minutes to avoid natural aging.

8. The heat treatment process according to claim 1, characterized in that: In S3, after the aging treatment is completed, the mixture is placed in air and cooled to room temperature.

9. Use of a microalloyed material of a cast Al-Cu alloy for an engine obtained by the heat treatment process according to any one of claims 1 to 8 as a lightweight material for an engine in the automotive field.

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