High-strength high-temperature-resistant Al-Cu-Mg alloy and preparation method thereof

Abstract

This application belongs to the field of high-strength and high-temperature resistant aluminum alloy deformation heat treatment technology, specifically relating to a high-strength and high-temperature resistant Al-Cu-Mg alloy and its preparation method. The preparation method includes the following steps: S1, obtaining an Al-Cu-Mg alloy billet, and performing a first homogenization and a second homogenization on the Al-Cu-Mg alloy billet to obtain a first alloy. By mass percentage, the composition of the Al-Cu-Mg alloy billet is: Cu: 5.5%-6.0%, Mg: 0.10%-0.40%, Mn: 0.20%-0.40%, Ag: 0.20%-0.60%, Sc: 0.05%-0.15%, V: 0.05%-0.25%, with the remainder being Al and unavoidable impurities; S2, performing surface mechanical grinding on the first alloy to obtain a second alloy; S3, performing a first aging and a second aging on the second alloy to obtain the Al-Cu-Mg alloy. This application employs a combination of microalloying, surface mechanical polishing, and high-temperature reaging techniques to design a low-interface-energy grain boundary and precipitate composite structure, thereby synergistically improving the room-temperature mechanical properties and high-temperature properties of the alloy.

Description

Technical Field

[0001] This application relates to the field of high-strength, high-temperature resistant aluminum alloy deformation heat treatment technology, specifically, this application relates to a high-strength, high-temperature resistant Al-Cu-Mg alloy and its preparation method. Background Technology

[0002] Al-Cu-Mg (2xxx series) alloys are ideal materials due to their lightweight, high strength, and heat resistance. In particular, the development of aerospace technology and the innovation of high-end weaponry have created a demand for Al-Cu-Mg alloys with strengths exceeding 100 MPa under operating conditions of 400°C. Therefore, Al-Cu-Mg alloys have attracted increasing attention from scientists. During service, aircraft hulls and internal load-bearing components are frequently exposed to environments exceeding 400°C, leading to grain boundary migration and severe coarsening of precipitates, resulting in rapid softening and failure of the alloy. Therefore, the thermal stability of grain boundaries and precipitates will become a major challenge in the field of aluminum alloys and light alloys.

[0003] Currently, commercially available 2xxx series aluminum alloys are only applicable at 200℃, far below the 400℃ service requirement. To address this, researchers mainly use the following two methods to enhance the high-temperature performance of Al-Cu-Mg alloys: (1) Stabilizing the precipitate interface. Adding trace elements (such as Ce, Ni, Sc, Zr, Mn, etc.) to Al-Cu-Mg alloys promotes interface segregation and improves the thermal stability of the precipitates, with a heat resistance temperature reaching 350℃. However, the alloys prepared by this method can only achieve single-interface structure strengthening, and the precipitates are prone to coarsening when the service temperature exceeds 350℃. (2) Constructing small-angle grain boundary structures. Al-Cu-Mg alloys generate twin boundaries or low-angle grain boundaries through low-temperature large plastic deformation, ultimately obtaining low-energy nanostructures. This structure has low grain boundary migration driving force at 350℃~400℃, thus improving the high-temperature performance of the material. However, the elongation of the alloys prepared by this process is less than 5%, which limits its application range.

[0004] To address the aforementioned challenges, we developed a novel interface structure with low-energy grain boundaries and precipitates by combining numerical calculations and deformation heat treatment design. Compared to the corresponding alloy with single Sc microalloying, this maintains sufficient precipitation and grain boundary strengthening effects. Therefore, this paper proposes a high-strength, high-temperature resistant Al-Cu-Mg alloy and its processing and heat treatment techniques. The low-interface-energy grain boundary and precipitate structure is designed through composite microalloying, synergistically improving room-temperature mechanical properties and high-temperature performance at 400℃. Summary of the Invention

[0005] To solve the above-mentioned technical problems, this application provides a method for preparing a high-strength, high-temperature resistant Al-Cu-Mg alloy, comprising the following steps: S1, obtaining an Al-Cu-Mg alloy billet, and performing a first homogenization and a second homogenization on the Al-Cu-Mg alloy billet to obtain a first alloy. The composition of the Al-Cu-Mg alloy billet, by mass percentage, is: Cu: 5.5%-6.0%, Mg: 0.10%-0.40%, Mn: 0.20%-0.40%, Ag: 0.20%-0.60%, Sc: 0.05%-0.15%, V: 0.05%-0.25%, with the remainder being Al and unavoidable impurities; S2, performing surface mechanical grinding on the first alloy to obtain a second alloy; S3, performing a first aging and a second aging on the second alloy to obtain an Al-Cu-Mg alloy.

[0006] As a preferred embodiment of the preparation method of the high-strength and high-temperature resistant Al-Cu-Mg alloy described in this application, the specific method for obtaining the Al-Cu-Mg alloy billet in step S1 is as follows: according to the composition ratio of the raw materials of the Al-Cu-Mg alloy billet, the raw materials include pure aluminum ingots, pure magnesium ingots, pure silver ingots, aluminum master alloys and rare earth alloys, the raw materials are smelted and cast in a resistance furnace at 720-760℃ to obtain the Al-Cu-Mg alloy billet.

[0007] As a preferred embodiment of the preparation method of a high-strength and high-temperature resistant Al-Cu-Mg alloy described in this application, in step S1, the temperature of the first homogenization is 280-320℃, and the time of the first homogenization is 20-28h.

[0008] As a preferred embodiment of the preparation method of a high-strength and high-temperature resistant Al-Cu-Mg alloy described in this application, in step S1, the temperature of the second homogenization is 480-520℃, and the time of the second homogenization is 44-52h.

[0009] As a preferred embodiment of the preparation method of the high-strength, high-temperature resistant Al-Cu-Mg alloy described in this application, in step S2, the surface mechanical polishing temperature is -60 to 25°C, and the surface mechanical polishing strain rate is 10. 2 -10 4 s -1 The strain of the surface mechanical polishing is 10%-35%.

[0010] As a preferred embodiment of the preparation method of a high-strength and high-temperature resistant Al-Cu-Mg alloy described in this application, in step S3, the temperature of the first aging is 150-190℃, the time of the first aging is 12-18h, and the cooling method of the first aging is water cooling.

[0011] As a preferred embodiment of the preparation method of a high-strength and high-temperature resistant Al-Cu-Mg alloy described in this application, in step S3, the temperature of the second aging is 380-420℃, the time of the second aging is 8-12h, and the cooling method of the second aging is water cooling.

[0012] This application also provides a high-strength, high-temperature resistant Al-Cu-Mg alloy, which is prepared using the above-described method for preparing high-strength, high-temperature resistant Al-Cu-Mg alloys.

[0013] As a preferred embodiment of the high-strength, high-temperature resistant Al-Cu-Mg alloy described in this application, the Al-Cu-Mg alloy has a tensile strength ≥490MPa at room temperature and an elongation ≥7.0% at room temperature.

[0014] As a preferred embodiment of the high-strength and high-temperature resistant Al-Cu-Mg alloy described in this application, the Al-Cu-Mg alloy has a tensile strength ≥90MPa at 400℃ and an elongation ≥16.0% at 400℃.

[0015] The beneficial effects of this application are as follows:

[0016] This application proposes a method for preparing a high-strength, high-temperature resistant Al-Cu-Mg alloy. The aim is to find a microstructure design method for multi-component aluminum-copper alloys that can maximize the effects of multiple microalloying while overcoming the limitations of low high-temperature performance and machinability. Composite Sc and V microalloying was performed in the Al-Cu-Mg alloy, assembling θ′-Al2Cu and AlCuSc(V) co-precipitates. Furthermore, the interaction between composite microalloying and surface mechanical polishing was used to maximize the positive effect of creating a dual low-energy interface of grain boundaries and precipitates, synergistically improving the room-temperature and high-temperature mechanical properties of the Al-Cu-Mg alloy. First, under low-temperature conditions, the alloy was surface mechanically polished to prepare a gradient structure. The outer layer consists of low-angle grain boundaries with a depth span of 10–50 micrometers, while the inner layer contains ordinary grains. The introduction of trace amounts of Sc and V elements into the alloy increases the diffusion rate of Sc and V elements during the high-temperature reaging stage, promoting the segregation of some atoms towards the θ′ / Al matrix interface and others towards the low-angle grain boundaries. Al-Cu-Mg alloys were re-aged to obtain grain boundaries and precipitates with low interfacial energy, thereby creating a dual-stable microstructure.

[0017] This application overcomes the traditional concept that unstable grain boundaries and precipitates degrade the high-temperature mechanical properties of aluminum alloys by implementing an effective and executable processing system and Sc / V composite microalloying. It also overcomes the bottleneck problem of insufficient strength in traditional heat-treated strengthened aluminum alloys during service at 400℃. The Al-Cu-Mg alloy described in this application, characterized by Sc / V composite microalloying and surface mechanical polishing, achieves a low-interface-energy structure at the precipitate interface through high-temperature re-aging diffusion segregation, while simultaneously diffusing towards low-angle grain boundaries to form low-energy grain boundaries, resulting in a low-interface-energy grain boundary and precipitate composite structure.

[0018] This application employs a combination of microalloying, surface mechanical polishing, and high-temperature re-aging techniques to design a low-interface-energy grain boundary and precipitate composite microstructure, synergistically improving the room-temperature and high-temperature mechanical properties of the alloy. Since large plastic deformation at low temperatures can create low-angle grain boundaries, a gradient structure is first prepared by surface mechanical polishing at different strain rates under low-temperature conditions. Then, holding at 150-190℃ for 12-18h promotes the formation of the θ′ phase. Peak-aged alloys are then held at 380-420℃ for 8-12h to promote the full diffusion of Sc and V atoms into the θ′ phase, forming a low-energy interface. Simultaneously, this accelerates the diffusion of Sc and V atoms into the grain boundaries, forming an even lower-energy interface. Furthermore, a certain amount of dislocations is introduced to provide numerous nucleation sites for the θ′ phase during the aging process.

[0019] This application utilizes surface mechanical polishing to create a gradient structure and small-angle grain boundaries, followed by high-temperature re-aging to promote the segregation of Sc and V atoms at the θ′ / Al interface. Furthermore, large plastic deformation provides vacancies and dislocations, offering pathways for the diffusion of Sc and V atoms and encouraging their segregation towards the precipitate / matrix interface and grain boundaries.

[0020] The purpose of adding Sc and V microparticles in this application is to segregate and form low-interface-energy phases at the θ′ / Al matrix interface, thereby stabilizing the θ′ phase. The purpose of surface mechanical polishing is to form small-angle grain boundaries in the outer layer, while Sc and V atoms segregate at these grain boundaries to form low-energy grain boundaries, thus stabilizing the grain boundaries. The purpose of high-temperature re-aging heat treatment is to increase the diffusion rate of Sc and V atoms, thereby forming a dual structure of grain boundaries and low-energy precipitated phase interfaces.

[0021] The advantage of this application lies in combining microalloying techniques with surface mechanical polishing, overturning the traditional view that unstable microstructure is detrimental to the high-temperature mechanical properties of aluminum alloys. By controlling the microstructure of the alloy, its high strength and heat resistance characteristics at room temperature and high temperature are achieved. The microstructure design utilizes the low diffusion coefficients of Sc and V atoms to form a heat-resistant AlCuSc(V) nanophase and low-energy grain boundaries at a low-energy interface, strongly suppressing the coarsening of precipitates and grain boundary migration. Furthermore, the combination of high-temperature re-aging heat treatment and large plastic deformation provides nucleation sites for the θ′ phase formation and channels for atomic diffusion through dislocations and vacancies. High-temperature re-aging increases the diffusion rate of Sc and V atoms, which is beneficial for the segregation of Sc and V towards the θ′ / Al matrix interface and grain boundaries, forming low-interface-energy grain boundaries and precipitates, synergistically improving the alloy's room-temperature and high-temperature properties. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0023] Figure 1 This is a low-angle grain boundary structure diagram of the Al-Cu-Mg alloy prepared in Example 1 of this application;

[0024] Figure 2 The diagram shows the heat-resistant AlCuSc(V) nanophase structure of the Al-Cu-Mg alloy prepared in Example 1 of this application.

[0025] Figure 3 This is a low-energy interface structure diagram of the Al-Cu-Mg alloy prepared in Example 1 of this application.

[0026] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0027] The technical solutions in the embodiments will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0028] This application provides a method for preparing a high-strength, high-temperature resistant Al-Cu-Mg alloy, comprising the following steps:

[0029] S1. Obtain an Al-Cu-Mg alloy billet, and perform a first homogenization and a second homogenization on the Al-Cu-Mg alloy billet to obtain a first alloy. The composition of the Al-Cu-Mg alloy billet by mass percentage is: Cu: 5.5%-6.0%, Mg: 0.10%-0.40%, Mn: 0.20%-0.40%, Ag: 0.20%-0.60%, Sc: 0.05%-0.15%, V: 0.05%-0.25%, with the remainder being Al and unavoidable impurities.

[0030] The specific method for obtaining the Al-Cu-Mg alloy billet is as follows: Based on the composition ratio of the raw materials for the Al-Cu-Mg alloy billet, the raw materials include pure aluminum ingots, pure magnesium ingots, pure silver ingots, aluminum master alloys, and rare earth alloys. These raw materials are melted and cast in a resistance furnace at 720-760℃ to obtain the Al-Cu-Mg alloy billet. The first homogenization temperature is 280-320℃, and the first homogenization time is 20-28 hours. The second homogenization temperature is 480-520℃, and the second homogenization time is 44-52 hours.

[0031] Specifically, the first homogenization temperature is any one or any two of 280℃, 290℃, 300℃, 310℃, and 320℃; the first homogenization time is any one or any two of 20h, 21h, 22h, 23h, 24h, 25h, 26h, 27h, and 28h; the second homogenization temperature is any one or any two of 480℃, 490℃, 500℃, 510℃, and 520℃; and the second homogenization time is any one or any two of 44h, 45h, 46h, 47h, 48h, 49h, 50h, 51h, and 52h.

[0032] S2. The first alloy is mechanically ground to obtain the second alloy;

[0033] The surface mechanical polishing temperature is -60 to 25°C, and the surface mechanical polishing strain rate is 10. 2 -10 4 s -1 The strain of the surface mechanical polishing is 10%-35%;

[0034] Specifically, the surface mechanical polishing temperature is any one or any two of the following: -60℃, -55℃, -50℃, -45℃, -40℃, -35℃, -30℃, -25℃, -20℃, -15℃, -10℃, -5℃, 0℃, 5℃, 10℃, 15℃, 20℃, 25℃; the surface mechanical polishing strain is any one or any two of the following: 10%, 15%, 20%, 25%, 30%, 35%.

[0035] S3. The second alloy is subjected to first aging and second aging to obtain an Al-Cu-Mg alloy;

[0036] The temperature of the first aging process is 150-190℃, the aging time is 12-18h, and the cooling method for the first aging process is water cooling; the temperature of the second aging process is 380-420℃, the aging time is 8-12h, and the cooling method for the second aging process is water cooling.

[0037] Specifically, the temperature for the first aging is any one or any two of 150℃, 155℃, 160℃, 165℃, 170℃, 175℃, 180℃, 185℃, and 190℃; the time for the first aging is any one or any two of 12h, 13h, 14h, 15h, 16h, 17h, and 18h; the temperature for the second aging is any one or any two of 380℃, 385℃, 390℃, 395℃, 400℃, 405℃, 410℃, 415℃, and 420℃; and the time for the second aging is any one or any two of 8h, 9h, 10h, 11h, and 12h.

[0038] This application also provides a high-strength, high-temperature resistant Al-Cu-Mg alloy, which is prepared using the above-described method for preparing high-strength, high-temperature resistant Al-Cu-Mg alloys.

[0039] The Al-Cu-Mg alloy has a tensile strength ≥490MPa at room temperature and an elongation ≥7.0% at room temperature; the Al-Cu-Mg alloy has a tensile strength ≥90MPa at 400℃ and an elongation ≥16.0% at 400℃.

[0040] The technical solution of this application will be further described below with reference to specific embodiments.

[0041] The composition of the Al-Cu-Mg alloy ingots in the following embodiments, by mass percentage, is as follows: Cu: 5.9%, Mg: 0.33%, Mn: 0.35%, Ag: 0.28%, Sc: 0.14%, V: 0.15%, with the remainder being Al and unavoidable impurities. The specific method for obtaining the Al-Cu-Mg alloy ingots in the following embodiments is as follows: according to the composition ratio of the Al-Cu-Mg alloy ingots, the raw materials are selected as pure Al, Mg, Ag ingots, Al-50Cu, Al-10Mn, Al-3Sc, and Al-5V intermediate alloys. The raw materials are smelted and cast in a resistance furnace at 740°C to obtain the Al-Cu-Mg alloy ingots.

[0042] Example 1

[0043] This application provides a method for preparing a high-strength, high-temperature resistant Al-Cu-Mg alloy, comprising the following steps:

[0044] S1. Obtain an Al-Cu-Mg alloy billet, and perform a first homogenization and a second homogenization on the Al-Cu-Mg alloy billet to obtain a first alloy;

[0045] The first homogenization temperature was 300℃ and the time was 24h; the second homogenization temperature was 500℃ and the time was 48h.

[0046] S2. The first alloy is mechanically ground to obtain the second alloy;

[0047] The surface mechanical grinding temperature was -60℃, and the strain rate was 10. 3 s -1 The dependent variable is 20%;

[0048] S3. The second alloy is subjected to first aging and second aging to obtain an Al-Cu-Mg alloy;

[0049] The first aging process involves a temperature of 170℃ and a duration of 15 hours, with water cooling as the cooling method. The second aging process involves a temperature of 400℃ and a duration of 10 hours, with water cooling as the cooling method.

[0050] The Al-Cu-Mg alloy prepared in Example 1 was subjected to room temperature and 400℃ high-temperature mechanical property tests and structural characterization. The results are shown in [reference needed]. Figure 1 , Figure 2 and Figure 3 , Figure 1 This is a low-angle grain boundary structure diagram of the Al-Cu-Mg alloy prepared in Example 1 of this application; Figure 2 The diagram shows the heat-resistant AlCuSc(V) nanophase structure of the Al-Cu-Mg alloy prepared in Example 1 of this application. Figure 3This is a low-energy interface structure diagram of the Al-Cu-Mg alloy prepared in Example 1 of this application;

[0051] Figure 1 This refers to low-angle grain boundaries obtained after large plastic deformation. Figure 2 This refers to the heat-resistant AlCuSc(V) nanophase obtained after reaging at 400℃. Figure 3 The low-energy interface is represented by the heat-resistant AlCuSc(V) nanophase. The microstructure is characterized by the formation of low-angle grain boundaries (low grain boundary energy) during large plastic deformation, followed by the diffusion of intragranular Sc and V elements during reaging, which segregate at the precipitate interface to form the heat-resistant AlCuSc(V) nanophase. The Al-Cu-Mg alloy exhibits a tensile strength of 490.5 MPa and an elongation of 8.2% at room temperature; at 400℃, the Al-Cu-Mg alloy demonstrates a tensile strength of 91.3 MPa and an elongation of 17.8%.

[0052] Example 2

[0053] This application provides a method for preparing a high-strength, high-temperature resistant Al-Cu-Mg alloy, comprising the following steps:

[0054] S1. Obtain an Al-Cu-Mg alloy billet, and perform a first homogenization and a second homogenization on the Al-Cu-Mg alloy billet to obtain a first alloy;

[0055] The first homogenization temperature was 300℃ and the time was 24h; the second homogenization temperature was 500℃ and the time was 48h.

[0056] S2. The first alloy is mechanically ground to obtain the second alloy;

[0057] The surface mechanical grinding temperature was -60℃, and the strain rate was 10. 2 s -1 The dependent variable is 10%;

[0058] S3. The second alloy is subjected to first aging and second aging to obtain an Al-Cu-Mg alloy;

[0059] The first aging process involves a temperature of 170℃ and a duration of 15 hours, with water cooling as the cooling method. The second aging process involves a temperature of 400℃ and a duration of 10 hours, with water cooling as the cooling method.

[0060] The Al-Cu-Mg alloy prepared in Example 2 was subjected to mechanical property tests at room temperature and 400℃. The tensile strength of the Al-Cu-Mg alloy at room temperature was 492.8 MPa and the elongation at room temperature was 7.9%. The tensile strength of the Al-Cu-Mg alloy at 400℃ was 94.2 MPa and the elongation at 400℃ was 16.3%.

[0061] Example 3

[0062] This application provides a method for preparing a high-strength, high-temperature resistant Al-Cu-Mg alloy, comprising the following steps:

[0063] S1. Obtain an Al-Cu-Mg alloy billet, and perform a first homogenization and a second homogenization on the Al-Cu-Mg alloy billet to obtain a first alloy;

[0064] The first homogenization temperature was 300℃ and the time was 24h; the second homogenization temperature was 500℃ and the time was 48h.

[0065] S2. The first alloy is mechanically ground to obtain the second alloy;

[0066] The surface mechanical grinding temperature was -25℃, and the strain rate was 10. 4 s -1 The dependent variable is 25%;

[0067] S3. The second alloy is subjected to first aging and second aging to obtain an Al-Cu-Mg alloy;

[0068] The first aging process involves a temperature of 170℃ and a duration of 15 hours, with water cooling as the cooling method. The second aging process involves a temperature of 400℃ and a duration of 10 hours, with water cooling as the cooling method.

[0069] The Al-Cu-Mg alloy prepared in Example 3 was subjected to mechanical property tests at room temperature and 400℃. The tensile strength of the Al-Cu-Mg alloy at room temperature was 508.9 MPa and the elongation at room temperature was 7.8%. The tensile strength of the Al-Cu-Mg alloy at 400℃ was 110.3 MPa and the elongation at 400℃ was 16.1%.

[0070] Example 4

[0071] This application provides a method for preparing a high-strength, high-temperature resistant Al-Cu-Mg alloy, comprising the following steps:

[0072] S1. Obtain an Al-Cu-Mg alloy billet, and perform a first homogenization and a second homogenization on the Al-Cu-Mg alloy billet to obtain a first alloy;

[0073] The first homogenization temperature was 300℃ and the time was 24h; the second homogenization temperature was 500℃ and the time was 48h.

[0074] S2. The first alloy is mechanically ground to obtain the second alloy;

[0075] The surface mechanical grinding temperature was -25℃, and the strain rate was 10. 2 s -1 The dependent variable is 15%;

[0076] S3. The second alloy is subjected to first aging and second aging to obtain an Al-Cu-Mg alloy;

[0077] The first aging process involves a temperature of 170℃ and a duration of 15 hours, with water cooling as the cooling method. The second aging process involves a temperature of 400℃ and a duration of 10 hours, with water cooling as the cooling method.

[0078] The Al-Cu-Mg alloy prepared in Example 4 was subjected to mechanical property tests at room temperature and 400℃. The tensile strength of the Al-Cu-Mg alloy at room temperature was 501.2 MPa and the elongation at room temperature was 7.3%. The tensile strength of the Al-Cu-Mg alloy at 400℃ was 100.1 MPa and the elongation at 400℃ was 17.2%.

[0079] Example 5

[0080] This application provides a method for preparing a high-strength, high-temperature resistant Al-Cu-Mg alloy, comprising the following steps:

[0081] S1. Obtain an Al-Cu-Mg alloy billet, and perform a first homogenization and a second homogenization on the Al-Cu-Mg alloy billet to obtain a first alloy;

[0082] The first homogenization temperature was 300℃ and the time was 24h; the second homogenization temperature was 500℃ and the time was 48h.

[0083] S2. The first alloy is mechanically ground to obtain the second alloy;

[0084] The surface mechanical grinding temperature was 25℃, and the strain rate was 10. 4 s -1 The dependent variable is 35%;

[0085] S3. The second alloy is subjected to first aging and second aging to obtain an Al-Cu-Mg alloy;

[0086] The first aging process involves a temperature of 170℃ and a duration of 15 hours, with water cooling as the cooling method. The second aging process involves a temperature of 400℃ and a duration of 10 hours, with water cooling as the cooling method.

[0087] The Al-Cu-Mg alloy prepared in Example 5 was subjected to mechanical property tests at room temperature and 400℃. The tensile strength of the Al-Cu-Mg alloy at room temperature was 491.3 MPa and the elongation at room temperature was 7.5%. The tensile strength of the Al-Cu-Mg alloy at 400℃ was 96.3 MPa and the elongation at 400℃ was 16.3%.

[0088] Example 6

[0089] This application provides a method for preparing a high-strength, high-temperature resistant Al-Cu-Mg alloy, comprising the following steps:

[0090] S1. Obtain an Al-Cu-Mg alloy billet, and perform a first homogenization and a second homogenization on the Al-Cu-Mg alloy billet to obtain a first alloy;

[0091] The first homogenization temperature was 300℃ and the time was 24h; the second homogenization temperature was 500℃ and the time was 48h.

[0092] S2. The first alloy is mechanically ground to obtain the second alloy;

[0093] The surface mechanical grinding temperature was 25℃, and the strain rate was 10. 3 s -1 The dependent variable is 30%;

[0094] S3. The second alloy is subjected to first aging and second aging to obtain an Al-Cu-Mg alloy;

[0095] The first aging process involves a temperature of 170℃ and a duration of 15 hours, with water cooling as the cooling method. The second aging process involves a temperature of 400℃ and a duration of 10 hours, with water cooling as the cooling method.

[0096] The Al-Cu-Mg alloy prepared in Example 6 was subjected to mechanical property tests at room temperature and 400℃. The tensile strength of the Al-Cu-Mg alloy at room temperature was 497.3 MPa and the elongation at room temperature was 7.3%. The tensile strength of the Al-Cu-Mg alloy at 400℃ was 98.5 MPa and the elongation at 400℃ was 18.3%.

[0097] Comparative Example 1

[0098] This application provides a method for preparing a high-strength, high-temperature resistant Al-Cu-Mg alloy, comprising the following steps:

[0099] S1. Obtain an Al-Cu-Mg alloy billet and homogenize the Al-Cu-Mg alloy billet to obtain the first alloy.

[0100] The homogenization temperature was 500℃ and the time was 48h.

[0101] S2. The first alloy is mechanically ground to obtain the second alloy;

[0102] The surface mechanical grinding temperature was -60℃, and the strain rate was 10. 3 s -1 The dependent variable is 20%;

[0103] S3. The second alloy is subjected to first aging and second aging to obtain an Al-Cu-Mg alloy;

[0104] The first aging process involves a temperature of 170℃ and a duration of 15 hours, with water cooling as the cooling method. The second aging process involves a temperature of 400℃ and a duration of 10 hours, with water cooling as the cooling method.

[0105] The mechanical properties of the Al-Cu-Mg alloy prepared in Comparative Example 1 were tested at room temperature and at 400℃. The tensile strength of the Al-Cu-Mg alloy at room temperature was 475.1 MPa and the elongation at room temperature was 6.3%. The tensile strength of the Al-Cu-Mg alloy at 400℃ was 85.2 MPa and the elongation at 400℃ was 15.9%.

[0106] Comparative Example 2

[0107] This application provides a method for preparing a high-strength, high-temperature resistant Al-Cu-Mg alloy, comprising the following steps:

[0108] S1. Obtain an Al-Cu-Mg alloy billet and homogenize the Al-Cu-Mg alloy billet to obtain the first alloy.

[0109] The first homogenization temperature was 300℃ and the time was 24h; the second homogenization temperature was 500℃ and the time was 48h.

[0110] S2. The first alloy is mechanically ground to obtain the second alloy;

[0111] The surface mechanical grinding temperature was -60℃, and the strain rate was 10. 2 s -1 The dependent variable is 10%;

[0112] S3. The second alloy is subjected to first aging and second aging to obtain an Al-Cu-Mg alloy;

[0113] The first aging process involves a temperature of 170℃ and a duration of 15 hours, with water cooling as the cooling method. The second aging process involves a temperature of 350℃ and a duration of 10 hours, with water cooling as the cooling method.

[0114] The mechanical properties of the Al-Cu-Mg alloy prepared in Comparative Example 2 were tested at room temperature and at 400℃. The tensile strength of the Al-Cu-Mg alloy at room temperature was 466.2 MPa and the elongation at room temperature was 6.8%. The tensile strength of the Al-Cu-Mg alloy at 400℃ was 89.7 MPa and the elongation at 400℃ was 15.6%.

[0115] Comparative Example 3

[0116] This application provides a method for preparing a high-strength, high-temperature resistant Al-Cu-Mg alloy, comprising the following steps:

[0117] S1. Obtain an Al-Cu-Mg alloy billet and homogenize the Al-Cu-Mg alloy billet to obtain the first alloy.

[0118] The first homogenization temperature was 300℃ and the time was 24h; the second homogenization temperature was 500℃ and the time was 48h.

[0119] S2. The first alloy is subjected to deep cryogenic rolling deformation to obtain the second alloy;

[0120] Among them, the cryogenic rolling deformation temperature is -25℃, and the strain is 25%;

[0121] S3. The second alloy is subjected to first aging and second aging to obtain an Al-Cu-Mg alloy;

[0122] The first aging process involves a temperature of 170℃ and a duration of 15 hours, with water cooling as the cooling method. The second aging process involves a temperature of 400℃ and a duration of 10 hours, with water cooling as the cooling method.

[0123] The mechanical properties of the Al-Cu-Mg alloy prepared in Comparative Example 3 were tested at room temperature and at 400℃. The tensile strength of the Al-Cu-Mg alloy at room temperature was 487.2 MPa and the elongation at room temperature was 6.4%. The tensile strength of the Al-Cu-Mg alloy at 400℃ was 87.3 MPa and the elongation at 400℃ was 15.0%.

[0124] Comparative Example 4

[0125] This application provides a method for preparing a high-strength, high-temperature resistant Al-Cu-Mg alloy, comprising the following steps:

[0126] S1. Obtain an Al-Cu-Mg alloy billet and homogenize the Al-Cu-Mg alloy billet to obtain the first alloy.

[0127] The first homogenization temperature was 300℃ and the time was 24h; the second homogenization temperature was 500℃ and the time was 48h.

[0128] S2. The first alloy is mechanically ground to obtain the second alloy;

[0129] The surface mechanical grinding temperature was -25℃, and the strain rate was 10. 2 s -1 The dependent variable is 15%;

[0130] S3. The second alloy is subjected to a first aging process to obtain an Al-Cu-Mg alloy;

[0131] The first aging process was carried out at a temperature of 170℃ for 15 hours, and the cooling method was water cooling.

[0132] The mechanical properties of the Al-Cu-Mg alloy prepared in Comparative Example 4 were tested at room temperature and at 400℃. The tensile strength of the Al-Cu-Mg alloy at room temperature was 478.3 MPa and the elongation at room temperature was 6.9%. The tensile strength of the Al-Cu-Mg alloy at 400℃ was 85.0 MPa and the elongation at 400℃ was 15.5%.

[0133] Comparative Example 5

[0134] This application provides a method for preparing a high-strength, high-temperature resistant Al-Cu-Mg alloy, comprising the following steps:

[0135] S1. Obtain an Al-Cu-Mg alloy billet. Homogenize the Al-Cu-Mg alloy billet to obtain the first alloy. By mass percentage, the composition of the Al-Cu-Mg alloy billet is: Cu: 5.9%, Mg: 0.33%, Mn: 0.35%, Ag: 0.28%, V: 0.15%, with the remainder being Al and unavoidable impurities.

[0136] The first homogenization temperature was 300℃ and the time was 24h; the second homogenization temperature was 500℃ and the time was 48h.

[0137] S2. The first alloy is mechanically ground to obtain the second alloy;

[0138] The surface mechanical grinding temperature was 25℃, and the strain rate was 10. 4 s -1 The dependent variable is 35%;

[0139] S3. The second alloy is subjected to first aging and second aging to obtain an Al-Cu-Mg alloy;

[0140] The first aging process involves a temperature of 170℃ and a duration of 15 hours, with water cooling as the cooling method. The second aging process involves a temperature of 400℃ and a duration of 10 hours, with water cooling as the cooling method.

[0141] The mechanical properties of the Al-Cu-Mg alloy prepared in Comparative Example 5 were tested at room temperature and at 400℃. The tensile strength of the Al-Cu-Mg alloy at room temperature was 480.6 MPa and the elongation at room temperature was 6.2%. The tensile strength of the Al-Cu-Mg alloy at 400℃ was 86.6 MPa and the elongation at 400℃ was 14.5%.

[0142] The performance of the Al-Cu-Mg alloys obtained in the examples and comparative examples was tested. The melting point of the alloy was determined by differential scanning calorimetry (DSC). The tensile strength and elongation of the Al-Cu-Mg alloys were tested according to the method of GB / T228.1-2010. The results are shown in Table 1, which is a comparison table of the alloy properties of Examples 1-6 and Comparative Examples 1-5.

[0143] Table 1

[0144]

[0145] As can be seen from the above examples and comparative examples: Example 1, combined with Comparative Example 1, shows that bi-stage homogenization forms Al3Sc particles at 300℃. This precipitated phase not only enhances room temperature performance but is also less prone to coarsening at 400℃. Example 2, combined with Comparative Example 2, shows that a reaging temperature of 400℃ more easily accelerates the diffusion of Sc and V atoms to form a low-energy interface for the precipitated phase. Example 3, combined with Comparative Example 3, shows that low-temperature large plastic deformation yields lower low-angle grain boundary energy. Example 4, combined with Comparative Example 4, shows that reaging at 400℃ can increase the diffusion rate of Sc and V atoms, thereby diffusing them to the precipitated phase interface and forming a heat-resistant AlCuSc(V) nanophase. Example 5, combined with Comparative Example 5, shows that the increase of Sc element can precipitate an Al3Sc strengthening phase and is also conducive to the formation of a heat-resistant AlCuSc(V) nanophase with a high heat resistance temperature. Examples 1-6, combined with Comparative Examples 1-5, show that low-energy, small-angle grain boundaries are formed through low-temperature large plastic deformation, resulting in low grain boundary migration driving force during high-temperature service. The 400℃ re-aging process increases the diffusion rate of Sc and V atoms, which is beneficial for the formation of heat-resistant AlCuSc(V) nanophases.

[0146] This application proposes a method for preparing a high-strength, high-temperature resistant Al-Cu-Mg alloy. The aim is to find a microstructure design method for multi-component aluminum-copper alloys that can maximize the effects of multiple microalloying while overcoming the limitations of low high-temperature performance and machinability. Composite Sc and V microalloying was performed in the Al-Cu-Mg alloy, assembling θ′-Al2Cu and AlCuSc(V) co-precipitates. Furthermore, the interaction between composite microalloying and surface mechanical polishing was used to maximize the positive effect of creating a dual low-energy interface of grain boundaries and precipitates, synergistically improving the room-temperature and high-temperature mechanical properties of the Al-Cu-Mg alloy. First, under low-temperature conditions, the alloy was surface mechanically polished to prepare a gradient structure. The outer layer consists of low-angle grain boundaries with a depth span of 10–50 micrometers, while the inner layer contains ordinary grains. The introduction of trace amounts of Sc and V elements into the alloy increases the diffusion rate of Sc and V elements during the high-temperature reaging stage, promoting the segregation of some atoms towards the θ′ / Al matrix interface and others towards the low-angle grain boundaries. Al-Cu-Mg alloys were re-aged to obtain grain boundaries and precipitates with low interfacial energy, thereby creating a dual-stable microstructure.

[0147] This application overcomes the traditional concept that unstable grain boundaries and precipitates degrade the high-temperature mechanical properties of aluminum alloys by implementing an effective and executable processing system and Sc / V composite microalloying. It also overcomes the bottleneck problem of insufficient strength in traditional heat-treated strengthened aluminum alloys during service at 400℃. The Al-Cu-Mg alloy described in this application, characterized by Sc / V composite microalloying and surface mechanical polishing, achieves a low-interface-energy structure at the precipitate interface through high-temperature re-aging diffusion segregation, while simultaneously diffusing towards low-angle grain boundaries to form low-energy grain boundaries, resulting in a low-interface-energy grain boundary and precipitate composite structure.

[0148] This application employs a combination of microalloying, surface mechanical polishing, and high-temperature re-aging techniques to design a low-interface-energy grain boundary and precipitate composite microstructure, synergistically improving the room-temperature and high-temperature mechanical properties of the alloy. Since large plastic deformation at low temperatures can create low-angle grain boundaries, a gradient structure is first prepared by surface mechanical polishing at different strain rates under low-temperature conditions. Then, holding at 150-190℃ for 12-18h promotes the formation of the θ′ phase. Peak-aged alloys are then held at 380-420℃ for 8-12h to promote the full diffusion of Sc and V atoms into the θ′ phase, forming a low-energy interface. Simultaneously, this accelerates the diffusion of Sc and V atoms into the grain boundaries, forming an even lower-energy interface. Furthermore, a certain amount of dislocations is introduced to provide numerous nucleation sites for the θ′ phase during the aging process.

[0149] This application utilizes surface mechanical polishing to create a gradient structure and small-angle grain boundaries, followed by high-temperature re-aging to promote the segregation of Sc and V atoms at the θ′ / Al interface. Furthermore, large plastic deformation provides vacancies and dislocations, offering pathways for the diffusion of Sc and V atoms and encouraging their segregation towards the precipitate / matrix interface and grain boundaries.

[0150] The purpose of adding Sc and V microparticles in this application is to segregate and form low-interface-energy phases at the θ′ / Al matrix interface, thereby stabilizing the θ′ phase. The purpose of surface mechanical polishing is to form small-angle grain boundaries in the outer layer, while Sc and V atoms segregate at these grain boundaries to form low-energy grain boundaries, thus stabilizing the grain boundaries. The purpose of high-temperature re-aging heat treatment is to increase the diffusion rate of Sc and V atoms, thereby forming a dual structure of grain boundaries and low-energy precipitated phase interfaces.

[0151] The advantage of this application lies in combining microalloying techniques with surface mechanical polishing, overturning the traditional view that unstable microstructure is detrimental to the high-temperature mechanical properties of aluminum alloys. By controlling the microstructure of the alloy, its high strength and heat resistance characteristics at room temperature and high temperature are achieved. The microstructure design utilizes the low diffusion coefficients of Sc and V atoms to form a heat-resistant AlCuSc(V) nanophase and low-energy grain boundaries at a low-energy interface, strongly suppressing the coarsening of precipitates and grain boundary migration. Furthermore, the combination of high-temperature re-aging heat treatment and large plastic deformation provides nucleation sites for the θ′ phase formation and channels for atomic diffusion through dislocations and vacancies. High-temperature re-aging increases the diffusion rate of Sc and V atoms, which is beneficial for the segregation of Sc and V towards the θ′ / Al matrix interface and grain boundaries, forming low-interface-energy grain boundaries and precipitates, synergistically improving the alloy's room-temperature and high-temperature properties.

[0152] The above description is only a preferred embodiment of this application and does not limit the patent scope of this application. All equivalent structural transformations made under the inventive concept of this application and using the content of this application specification, or direct / indirect applications in other related technical fields, are included within the patent protection scope of this application.

Claims

1. A method for preparing a high-strength, high-temperature resistant Al-Cu-Mg alloy, characterized in that, Includes the following steps: S1. Obtain an Al-Cu-Mg alloy billet, and perform a first homogenization and a second homogenization on the Al-Cu-Mg alloy billet to obtain a first alloy. The composition of the Al-Cu-Mg alloy billet by mass percentage is: Cu: 5.5%-6.0%, Mg: 0.10%-0.40%, Mn: 0.20%-0.40%, Ag: 0.20%-0.60%, Sc: 0.05%-0.15%, V: 0.05%-0.25%, with the remainder being Al and unavoidable impurities. S2. The first alloy is mechanically ground to obtain the second alloy; S3. The second alloy is subjected to first aging and second aging to obtain an Al-Cu-Mg alloy; In step S1, the temperature of the first homogenization is 280-320℃, and the time of the first homogenization is 20-28h; the temperature of the second homogenization is 480-520℃, and the time of the second homogenization is 44-52h. In step S2, the temperature of the surface mechanical polishing is -60~25℃, and the strain rate of the surface mechanical polishing is 10. 2 -10 4 s -1 The strain of the surface mechanical polishing is 10%-35%; In step S3, the temperature of the first aging is 150-190℃, the aging time is 12-18h, and the cooling method of the first aging is water cooling; the temperature of the second aging is 380-420℃, the aging time is 8-12h, and the cooling method of the second aging is water cooling.

2. The method for preparing a high-strength, high-temperature resistant Al-Cu-Mg alloy according to claim 1, characterized in that, In step S1, the specific method for obtaining the Al-Cu-Mg alloy billet is as follows: according to the composition ratio of the raw materials of the Al-Cu-Mg alloy billet, the raw materials include pure aluminum ingots, pure magnesium ingots, pure silver ingots, aluminum master alloys and rare earth alloys, the raw materials are smelted and cast in a resistance furnace at 720-760℃ to obtain the Al-Cu-Mg alloy billet.

3. A high-strength, high-temperature resistant Al-Cu-Mg alloy, characterized in that, The high-strength, high-temperature resistant Al-Cu-Mg alloy was prepared using the preparation method described in any one of claims 1-2.

4. The high-strength, high-temperature resistant Al-Cu-Mg alloy according to claim 3, characterized in that, The Al-Cu-Mg alloy has a tensile strength ≥490MPa at room temperature and an elongation ≥7.0% at room temperature.

5. A high-strength, high-temperature resistant Al-Cu-Mg alloy according to claim 3, characterized in that, The Al-Cu-Mg alloy has a tensile strength ≥90MPa at 400℃ and an elongation ≥16.0% at 400℃.

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