High-strength heat-resistant Al-Cu alloy based on interface stabilization strategy and preparation method thereof

Abstract

The invention relates to the technical field of high-performance aluminum alloy materials, in particular to a high-strength heat-resistant A < l >-Cu alloy based on an interface stabilization strategy and a preparation method thereof.The high-strength heat-resistant A < l >-Cu alloy comprises, by mass, 5.03% of Cu, 0.29% of Sc, 0.22% of Zr, 0.31% of Mn, smaller than or equal to 0.05% of single impurity elements, smaller than or equal to 0.15% of total impurity elements and the balance A < l >; after 1000 hours of thermal exposure at the temperature of 300 DEG C, the tensile strength is still larger than or equal to 300 MPa and is far superior to that of a traditional Al-Cu alloy, back-to-back synergistic segregation of Sc and Mn elements is achieved for the first time, theta '-phase coherent and semi-coherent interfaces are synchronously stabilized, the coarsening path is comprehensively blocked, the utilization rate of the Sc element is increased through the pre-aging technology, premature consumption of the Sc element is avoided, and the actual use cost of the expensive Sc element is reduced.

Description

Technical Field

[0001] This invention relates to the field of high-performance aluminum alloy materials technology, specifically to a high-strength, heat-resistant Al-Cu alloy based on an interface stabilization strategy and its preparation method. Background Technology

[0002] Al-Cu alloys are widely used in aerospace, machinery manufacturing and other fields due to their high strength and good machinability. However, traditional Al-Cu alloys have shortcomings in high-temperature performance: the GP zone and θ″ phase precipitated at low temperatures or the θ′ phase precipitated at higher temperatures are prone to coarsening, dissolution or transformation into coarse equilibrium θ phase (Al2Cu) at temperatures of 250℃ and above, resulting in a sharp decrease in strength and failing to meet the requirements for long-term high-temperature service.

[0003] To improve heat resistance, existing technologies attempt to add elements such as Sc, Zr, and Mn for microalloying, but there are obvious drawbacks: Sc is expensive and can only stabilize the θ′ phase coherent interface, and is ineffective for the semi-coherent interface of the main coarsening channel; Zr has an extremely slow diffusion rate, making it difficult to quickly exert an interface stabilizing effect in industrial applications; the interface segregation mechanism of Mn has not been fully explored, and its high-temperature strengthening effect is limited when added alone.

[0004] I. Existing Technology 1: Traditional Age-Strengthened Al-Cu Binary Alloys

[0005] Technical Description: These alloys are primarily strengthened by precipitating high-density GP zones or θ″ phases through low-temperature aging (180℃), or by precipitating θ′ phases through higher-temperature aging (250℃). Their high-temperature performance depends on the thermal stability of these metastable precipitates.

[0006] Main disadvantages:

[0007] 1. Poor heat resistance: The metastable GP zone, θ″ phase and θ′ phase will rapidly coarsen, dissolve or transform into coarse, incoherent equilibrium θ phase (Al2Cu) at temperatures of 250℃ and above, resulting in a sharp loss of strengthening effect and severe softening of alloy properties, which cannot meet the requirements for long-term high-temperature service.

[0008] 2. Limited selection of strengthening phase: The strengthening phase (mainly θ″ or θ′) obtained by traditional heat treatment processes (solution + artificial aging) is inherently unstable at high temperatures and lacks an effective mechanism to inhibit its coarsening and transformation.

[0009] II. Existing Technology 2: Microalloyed Al-Cu Alloys with Added Sc and Zr Elements

[0010] Technical Description: In order to improve the heat resistance of traditional Al-Cu alloys, researchers have added slow-diffusion elements such as Sc and Zr to the alloys. These elements form thermally stable L12 structure Al3(Sc,Zr) nanoparticles in the alloy or agglomerate at the precipitate interface, thereby improving recrystallization resistance and inhibiting precipitate coarsening.

[0011] Main disadvantages:

[0012] 1. Limited Effect and High Cost of Sc: While Sc can improve the thermal stability of the θ′ phase, its effect is limited. After prolonged exposure to high temperatures, the θ′ phase still undergoes significant coarsening and dissolution. Moreover, Sc is an extremely expensive rare metal, and its limited synergistic effect is disproportionate to its high cost, resulting in low economic benefits.

[0013] 2. Slow diffusion kinetics of Zr: The diffusion rate of Zr in the Al matrix is ​​extremely slow (the diffusion coefficient is extremely low at 300℃). It is difficult to effectively segregate to the interface and play a role within the normal high temperature exposure time (such as hundreds of hours). It requires an extremely long heat treatment time (such as more than 2000 hours) to observe its effect, which is not feasible in practical industrial applications.

[0014] 3. Inadequate interface stabilization mechanism: Sc elements typically only cluster at the coherent interface of the θ′ phase, lacking effective stabilization measures for semi-coherent interfaces with higher interface energy, which are the main channels for radial coarsening of the θ′ phase. Therefore, the singular clustering of Sc cannot comprehensively suppress all coarsening paths of the θ′ phase.

[0015] III. Existing Technology 3: Al-Cu Alloy with Added Mn

[0016] Technical Description: Mn is commonly used in Al-Cu alloys to form dispersions and increase recrystallization temperature. Previous studies have indicated that Mn can segregate at the θ′ phase interface.

[0017] Main disadvantages:

[0018] 1. Unclear mechanism of action and limited effectiveness: Existing technologies only recognize the interfacial segregation behavior of Mn elements, but lack in-depth understanding and effective utilization of the specific location of segregation, whether it can form a new phase, and how it synergizes with other elements. There are no reports of Mn elements and Sc elements synergistically forming a "back-to-back" interfacial segregation structure and ultimately forming a stable T phase to encapsulate the θ′ phase.

[0019] Adding it alone is not effective: Without the synergistic effect of Sc, Mn does not significantly improve the high-temperature creep strength of Al-Cu alloys.

[0020] The core challenge of existing technologies lies in the inability to construct a multi-level, multi-mechanism synergistic high-temperature stable system through efficient and economical methods. To address this, a high-strength heat-resistant Al-Cu alloy based on an interface stabilization strategy and its preparation method are proposed. Summary of the Invention

[0021] In view of this, the present invention provides a high-strength heat-resistant Al-Cu alloy based on an interface stabilization strategy and its preparation method, so as to solve or alleviate the technical problems existing in the prior art, and at least provide a beneficial option.

[0022] The technical solution of the present invention is implemented as follows: a high-strength heat-resistant Al-Cu alloy based on an interface stabilization strategy, the composition by mass percentage is: Cu 5.03%, Sc 0.29%, Zr 0.22%, Mn 0.31%, impurity elements ≤0.05% individually and ≤0.15% in total, with the balance being Al.

[0023] Further preferred microstructures exhibit a multiphase synergistic stability: the θ′ phase serves as the core reinforcing phase, the coherent interface is encapsulated by the Al3Sc phase, and the semi-coherent interface is encapsulated by the T phase (Al3Sc). 20 With Cu2Mn3) coating and further preferred dispersion in the matrix, after 1000 hours of heat exposure at 300℃, the tensile strength is ≥300MPa, the elongation is ≥7.3%, and the microhardness is ≥77.9HV.

[0024] A method for preparing a high-strength, heat-resistant Al-Cu alloy based on an interface stabilization strategy includes the following steps:

[0025] Step 1, Alloy Melting and Casting: Select pure Al, Al-50%Cu, Al-2%Sc, Al-10%Zr, and Al-10%Mn master alloys as raw materials according to the composition ratio, melt them in a vacuum induction furnace under argon protection, and then cast them into ingots after ultrasonic-assisted stirring.

[0026] Step 2, Homogenization heat treatment: The ingot is held at 480℃ for 24 hours, followed by water quenching;

[0027] Step 3, hot deformation processing: The homogenized ingot is held at 450℃ for 1 hour and then hot rolled to 12mm; then annealed at 450℃ for 1 hour and continuously cold rolled to 2mm.

[0028] Step 4, Solution treatment: Hold the deformed alloy at 550-580℃ for 1-3 hours, then quickly water quench to form a supersaturated solid solution;

[0029] Step 5, Pre-aging treatment: Hold the solution-quenched alloy at 230-270℃ for 5-20 hours to precipitate strengthening phases, mainly θ′ phase;

[0030] Step 6, High-Temperature Heat Exposure / Service: The pre-aged alloy is subjected to long-term heat exposure at 300-350℃ or direct high-temperature service to form a stable composite microstructure.

[0031] More preferably, in step one, the ultrasonic-assisted stirring power is 2kW, the stirring time is 20 minutes, and the ingot size after casting is Φ80mm.

[0032] More preferably, in step five, the pre-aging treatment parameters are 250°C for 11 hours followed by air cooling.

[0033] More preferably, in step six, the high-temperature thermal exposure temperature is 300℃, and the exposure time is not less than 200 hours; during the thermal exposure process, Sc elements segregate at the θ′ phase coherent interface to form the Al3Sc phase, and Mn elements segregate at the θ′ phase semi-coherent interface to form the T phase (Al3Sc). 20 Cu2Mn3) and Al3(Sc,Zr) nanoparticles are simultaneously precipitated in the matrix.

[0034] The embodiments of the present invention have the following advantages due to the adoption of the above technical solutions:

[0035] I. After being exposed to heat at 300℃ for 1000 hours, the tensile strength of this invention is still ≥300MPa, which is far superior to that of traditional Al-Cu alloys. For the first time, it achieves the "back-to-back" synergistic segregation of Sc and Mn elements, simultaneously stabilizing the coherent and semi-coherent interfaces of the θ′ phase, completely blocking the coarsening path, and improving the utilization rate of Sc element through the pre-aging process to avoid its premature consumption and reduce the actual use cost of expensive Sc element.

[0036] Second, all the smelting, processing and heat treatment processes of this invention can be realized in existing aluminum alloy industrial production lines without the need for new special equipment. It has good industrialization prospects and can meet the long-term service requirements of high temperature environment of 250-350℃. It is suitable for high temperature structural parts in aerospace, high-end equipment and other fields.

[0037] The above overview is for illustrative purposes only and is not intended to be limiting in any way. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features of the invention will become readily apparent from the accompanying drawings and the following detailed description. Attached Figure Description

[0038] 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 these drawings without creative effort.

[0039] Figure 1 This is a flowchart of the method of the present invention;

[0040] Figure 2 The hardness curves of the three alloys of this invention at different temperatures are shown.

[0041] Figure 3 This is a flowchart of the method for tensile properties of different pre-aged alloys according to the present invention;

[0042] Figure 4 The images shown are transmission electron microscope (TEM) images and energy dispersive spectroscopy (EDS) spectra of the aged alloy of this invention after being exposed to heat at 300°C for 1000 hours. Detailed Implementation

[0043] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0044] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0045] like Figure 1 As shown, this embodiment of the invention provides a high-strength heat-resistant Al-Cu alloy based on an interface stabilization strategy. The composition by mass percentage is: Cu 5.03%, Sc 0.29%, Zr 0.22%, Mn 0.31%, with individual impurity elements ≤0.05% and total impurity elements ≤0.15%, and the balance being Al.

[0046] In one embodiment, the microstructure is a multiphase co-stabilized structure: the θ′ phase is the core reinforcing phase, the coherent interface is covered by the Al3Sc phase, and the semi-coherent interface is covered by the T phase (Al3Sc). 20 In one embodiment, the Cu2Mn3) coating and the dispersed components in the matrix exhibit a tensile strength ≥300MPa, an elongation ≥7.3%, and a microhardness ≥77.9HV after being exposed to heat at 300°C for 1000 hours.

[0047] A method for preparing a high-strength, heat-resistant Al-Cu alloy based on an interface stabilization strategy includes the following steps:

[0048] Step 1, Alloy Smelting and Casting: Pure Al, Al-50%Cu, Al-2%Sc, Al-10%Zr, and Al-10%Mn master alloys were selected as raw materials according to the composition ratio and smelted in a vacuum induction furnace under argon protection. After ultrasonic-assisted stirring, they were cast into ingots. The above raw materials were proportioned, smelted, and cast into ingots. The chemical composition of the alloy was determined by inductively coupled plasma atomic emission spectrometry, as shown in Table 1.

[0049] Table 1. Composition of the aluminum alloy used in the experiment (wt.%)

[0050]

[0051] Step 2, Homogenization heat treatment: The ingot is held at 480℃ for 24 hours, followed by water quenching;

[0052] Step 3, hot deformation processing: The homogenized ingot is held at 450℃ for 1 hour and then hot rolled to 12mm; then annealed at 450℃ for 1 hour and continuously cold rolled to 2mm.

[0053] Step 4, Solution treatment: Hold the deformed alloy at 550-580℃ for 1-3 hours, then quickly water quench to form a supersaturated solid solution;

[0054] Step 5, Pre-aging treatment: Hold the solution-quenched alloy at 230-270℃ for 5-20 hours to precipitate strengthening phases, mainly θ′ phase;

[0055] Step 6, High-Temperature Heat Exposure / Service: The pre-aged alloy is subjected to long-term heat exposure at 300-350℃ or direct high-temperature service to form a stable composite microstructure.

[0056] In one embodiment, in step one, the ultrasonic-assisted stirring power is 2kW, the stirring time is 20 minutes, and the ingot size after casting is Φ80mm.

[0057] In one embodiment, in step five, the preferred parameters for the pre-aging treatment are: holding at 250°C for 11 hours followed by air cooling.

[0058] In one embodiment, in step six, the high-temperature thermal exposure temperature is 300°C, and the exposure time is not less than 200 hours; during the thermal exposure process, Sc elements segregate at the θ′ phase coherent interface to form the Al3Sc phase, and Mn elements segregate at the θ′ phase semi-coherent interface to form the T phase (Al3Sc). 20 Cu2Mn3) and Al3(Sc,Zr) nanoparticles are simultaneously precipitated in the matrix.

[0059] Preparation and performance testing of high-strength and heat-resistant Al-Cu alloys

[0060] Batching and Smelting: Weigh pure Al, Al-50% Cu, Al-2% Sc, Al-10% Zr, and Al-10% Mn to prepare an alloy with a nominal composition of Al-5.0Cu-0.3Sc-0.2Zr-0.3Mn (wt%). Smelt in an argon-protected vacuum induction furnace with ultrasonic-assisted stirring (2kW, 20min), and cast into Φ80mm ingots.

[0061] Homogenization treatment: Hold at 480℃ for 24 hours, then water quench;

[0062] Hot working: After holding at 450℃ for 1 hour, hot roll to 12mm; after annealing at 450℃ for 1 hour, 12mm sheet is cold rolled to 2mm.

[0063] Solution treatment: Hold at 550-580℃ for 1-2.5 hours, then water quench;

[0064] Pre-aging treatment: Hold at 250℃ for 11 hours, then air cool;

[0065] High-temperature heat exposure: 300℃ heat exposure for 1000 hours, followed by air cooling;

[0066] Performance testing: Room temperature tensile test showed that the alloy had a tensile strength of 304.2±8.1MPa, an elongation of 7.3±1.5%, and a microhardness of 77.9±2.5HV.

[0067] Comparative verification

[0068] Comparative Example 1 (Traditional Al-Cu Alloy): The Al-Cu binary alloy treated with the same process had a tensile strength of 155.1 ± 5.4 MPa after being exposed to heat at 300°C for 1000 hours, which was significantly lower than that of the alloy of the present invention.

[0069] Comparative Example 2 (Al-Cu-Sc-Zr alloy): The tensile strength of the Mn-free Al-Cu-Sc-Zr alloy treated with the same process was 232.2±7.4MPa, which was still lower than that of the alloy of the present invention;

[0070] Results analysis: Microstructure observation confirmed that the θ′ phase in the alloy of the present invention is small in size and has a stable interface, while the θ phase in Comparative Example 1 is mainly coarse, and the θ′ phase in Comparative Example 2 shows obvious dissolution, which verifies the strengthening effect of Sc and Mn synergy and process design.

[0071] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various variations or substitutions within the technical scope disclosed in the present invention, and these should all be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A high-strength, heat-resistant Al-Cu alloy based on an interface stabilization strategy, characterized in that: The composition by mass percentage is: Cu 5.03%, Sc 0.29%, Zr 0.22%, Mn 0.31%, with individual impurity elements ≤0.05% and total impurity elements ≤0.15%, and the balance being Al.

2. The high-strength, heat-resistant Al-Cu alloy based on an interface stabilization strategy according to claim 1, characterized in that: The microstructure is a multiphase synergistically stable structure: the θ′ phase is the core reinforcing phase, the coherent interface is covered by the Al3Sc phase, and the semi-coherent interface is covered by the T phase (Al3Sc). 20 Cu2Mn3) coating, with Al3(Sc,Zr) nanoparticles dispersed in the matrix.

3. The high-strength, heat-resistant Al-Cu alloy based on an interface stabilization strategy according to claim 1, characterized in that: After being exposed to heat at 300℃ for 1000 hours, the tensile strength is ≥300MPa, the elongation is ≥7.3%, and the microhardness is ≥77.9HV.

4. A method for preparing a high-strength, heat-resistant Al-Cu alloy based on an interface stabilization strategy, in conjunction with the high-strength, heat-resistant Al-Cu alloy based on an interface stabilization strategy as described in any one of claims 1-3, characterized in that: Includes the following steps: Step 1, Alloy Melting and Casting: Select pure Al, Al-50%Cu, Al-2%Sc, Al-10%Zr, and Al-10%Mn master alloys as raw materials according to the composition ratio, melt them in a vacuum induction furnace under argon protection, and then cast them into ingots after ultrasonic-assisted stirring. Step 2, Homogenization heat treatment: The ingot is held at 480℃ for 24 hours, followed by water quenching; Step 3, hot deformation processing: The homogenized ingot is held at 450℃ for 1 hour and then hot rolled to 12mm; then annealed at 450℃ for 1 hour and continuously cold rolled to 2mm. Step 4, Solution treatment: Hold the deformed alloy at 550-580℃ for 1-3 hours, then quickly water quench to form a supersaturated solid solution; Step 5, Pre-aging treatment: Hold the solution-quenched alloy at 230-270℃ for 5-20 hours to precipitate strengthening phases, mainly θ′ phase; Step 6, High-Temperature Heat Exposure / Service: The pre-aged alloy is subjected to long-term heat exposure at 300-350℃ or direct high-temperature service to form a stable composite microstructure.

5. The method for preparing a high-strength, heat-resistant Al-Cu alloy based on an interface stabilization strategy according to claim 4, characterized in that: In step one, the ultrasonic-assisted stirring power is 2kW, the stirring time is 20 minutes, and the ingot size after casting is Φ80mm.

6. The method for preparing a high-strength, heat-resistant Al-Cu alloy based on an interface stabilization strategy according to claim 4, characterized in that: In step five, the preferred parameters for the pre-aging treatment are 250°C for 11 hours followed by air cooling.

7. The method for preparing a high-strength, heat-resistant Al-Cu alloy based on an interface stabilization strategy according to claim 4, characterized in that: In step six, the high-temperature thermal exposure temperature is 300℃, and the exposure time is no less than 200 hours. During the thermal exposure process, Sc elements segregate at the θ′ phase coherent interface to form the Al3Sc phase, and Mn elements segregate at the θ′ phase semi-coherent interface to form the T phase (Al3Sc). 20 Cu2Mn3) and Al3(Sc,Zr) nanoparticles are simultaneously precipitated in the matrix.

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