Processing method for obtaining submicron equiaxed crystal structure from Al-Cu alloy and Al-Cu alloy

Abstract

The invention belongs to the technical field of material processing, and relates to a processing method for obtaining a submicron equiaxed crystal structure from an Al-Cu alloy and the Al-Cu alloy, the processing method comprises the following steps: (a) forging an Al-Cu alloy ingot into an Al-Cu alloy plate through a forging process; (b) the Al-Cu alloy plate obtained through forging is subjected to homogenizing annealing and solid solution heat treatment; (c) rolling the Al-Cu alloy plate subjected to heat treatment at room temperature to obtain a rolled Al-Cu alloy plate; (d) the rolled-state Al-Cu alloy plate is manufactured into a thin plate through machining; and (e) carrying out high-temperature short-time heat treatment on the thin plate so as to form a uniform submicron equiaxed crystal structure in the thin plate. According to the method, the submicron equiaxed crystal structure is efficiently obtained in the Al-Cu alloy on the basis of the Al-Cu alloy cast ingot in combination with the rolling and heat treatment machining process, and the machining method has important significance in revealing the evolution rule of the microstructure of an aluminum alloy material and optimizing machining process parameters.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of material processing, and relates to a processing method for obtaining a submicron equiaxed crystal structure in an Al-Cu alloy and the Al-Cu alloy. BACKGROUND

[0002] Aluminum alloy, as a key lightweight high-strength structural material, has rapidly expanded its application since it emerged in the aviation industry in the early 20th century and has been widely used in various fields of modern industry. In the field of aerospace, aluminum alloy, with its excellent specific strength and corrosion resistance, has become the ideal choice for key components such as aircraft skin and rocket fuel tank. In the automotive industry, the trend of lightweight has led to a continuous increase in the proportion of aluminum alloy in vehicle body structures and battery packs. The booming development of new energy vehicles has also led to a strong demand for high-strength aluminum alloys. The construction industry makes full use of the durability and recyclability of aluminum alloys and widely applies them to green building systems such as curtain walls and doors and windows. In addition, the demand for aluminum alloys with high thermal conductivity and electromagnetic shielding properties is also increasing in emerging fields such as 5G communication and electronic device heat dissipation components. Among many application scenarios of aluminum alloys, 2XXX series aluminum alloys such as Al-Cu have an irreplaceable position in the fields of aerospace and weapon equipment due to their excellent heat resistance.

[0003] However, as the application scenarios become more complex, the performance bottlenecks of traditional aluminum alloys gradually emerge. Related studies have shown that precise control of microstructure through heat treatment is one of the key technologies to break through the performance limits of materials. Among them, grain size, as a key parameter of microstructure, has a significant impact on material performance. Within a certain temperature range, according to the Hall-Petch relationship, the yield strength of the material will increase as the grain size decreases. Based on this, over the past three decades, researchers have developed numerous metal microstructure control processing techniques to refine the grain size to submicron (100-1000 nm) and nanometer (<100 nm) to achieve grain refinement strengthening effect. These techniques include equal channel angular pressing (ECAP), severe plastic deformation (SPD), high-pressure torsion (HPT), accumulative roll bonding (ARB), and equal liquid extrusion (HE).

[0004] However, these existing methods have obvious shortcomings, such as high processing cost and low efficiency. The high cost limits its large-scale industrial application, and the low efficiency makes it difficult to meet the market demand for rapid iteration and mass production of aluminum alloy materials. Therefore, it is urgent to develop new fine-grained material preparation technologies. In-depth study of the microstructure evolution of aluminum alloy materials under the action of deformation processing and thermal field can provide a solid theoretical basis and clear guidance for the development of new technologies, and help to break through the limitations of existing technologies, further improve the performance of aluminum alloy materials, and meet the expanding and complex application demands. SUMMARY

[0005] Therefore, the present application aims to provide a processing method for obtaining submicron equiaxed crystal structure in Al-Cu alloy.

[0006] To achieve the above-mentioned purpose, the present application provides the following technical solutions.

[0007] A processing method for obtaining submicron equiaxed crystal structure in Al-Cu alloy, comprising the following steps:

[0008] (a) forging Al-Cu alloy ingot into Al-Cu alloy plate through forging process;

[0009] (b) homogenizing annealing and solid solution heat treatment of the Al-Cu alloy plate obtained by forging;

[0010] (c) room temperature rolling of the Al-Cu alloy plate after heat treatment to obtain rolled Al-Cu alloy plate;

[0011] (d) mechanical processing of the rolled Al-Cu alloy plate into thin plate;

[0012] (e) high-temperature short-time heat treatment of the thin plate to form uniform submicron equiaxed crystal structure in the thin plate.

[0013] Further, the Al-Cu alloy plate in step (a) is an aluminum plate with regular shape and uniform thickness.

[0014] Further, the homogenizing annealing in step (b) is at 490℃ for 10 hours. The homogenizing annealing promotes Cu atom diffusion, redistributes solute atoms, eliminates intracrystalline segregation and non-equilibrium phase, reduces residual stress, reduces deformation resistance in subsequent processing, and reduces the risk of cracks.

[0015] Further, the solid solution heat treatment in step (b) is at 505℃ for 1 hour, and the Al-Cu alloy plate is cooled to room temperature by water cooling after the solid solution heat treatment. The solid solution treatment makes the strengthening phase (such as θ phase Al2Cu) fully dissolved into the α-Al matrix, and then rapidly cools to form a supersaturated solid solution, providing a basis for aging strengthening.

[0016] Further, the deformation amount of the room temperature rolling in step (c) is 60%. The dislocation density in the deformation-induced refined structure increases sharply, and the grain boundary energy accumulates, so that the material as a whole has a higher stored energy. In the subsequent heat treatment process, the stored energy is gradually released through dislocation rearrangement and annihilation (such as dislocation climb and slip), and the high stored energy area (such as the grain boundary and the surrounding of the second phase particles) preferentially forms recrystallization nuclei. Therefore, during the rolling process, a sufficient deformation amount is required to provide sufficient driving force for the recovery and recrystallization of the material in the subsequent heat treatment process.

[0017] Further, the thickness of the thin plate obtained by mechanical processing in step (d) is 0.5-1.5mm. Because the volume effect of the sample will cause the cooling rate difference between the surface and the center of the sample and the uneven distribution of the temperature field, so that the recrystallization nucleation driving force of different regions is different, further leading to a wide size distribution range of the recrystallized grains and poor uniformity. Therefore, the thin plate needs to be processed to a suitable thickness.

[0018] Further, the temperature range of the high-temperature short-time heat treatment in step (e) is 385-400℃, and the holding time is 0.5-1 minute. The heating method of the present application is to warm up, and the holding temperature and time need to be within a suitable range. In a lower temperature range, the critical nucleation temperature cannot be reached, or the nucleation energy is low and the rate is slow. Long time holding at a low temperature will lead to the coarsening of precipitated phases, which will have a bad impact on the performance of the material. Higher temperature is easy to cause grain recrystallization and coarsening of the material in a very short time, and abnormal growth of the grains. In addition, higher temperature will cause the melting of the precipitated phase, which will greatly reduce the strengthening effect. Therefore, the appropriate temperature and holding time are very important.

[0019] Further, the Al-Cu alloy ingot is prepared from pure aluminum with a purity of 99.9996% and 4wt.% of oxygen-free high-conductivity copper.

[0020] Further, the grain size of the submicron equiaxed crystal structure obtained after step (e) is 100-1000nm, and the microstructure presents a uniform equiaxed crystal structure.

[0021] An Al-Cu alloy is processed by the processing method.

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

[0023] 1.The present invention aims to obtain a uniform sub-micron equiaxed crystal structure (grain size in 100-1000nm) in Al-Cu alloy ingot through a series of process steps. The main steps include forging, homogenization annealing, solid solution heat treatment, room temperature rolling, machining and high temperature short time heat treatment. These processes work together not only to optimize the microstructure of the alloy but also to significantly improve the performance of the material, providing support for its application in high demand areas.

[0024] 2.The present invention forges the ingot into an aluminum plate with uniform thickness through forging treatment, ensuring consistency in subsequent processing and reducing defects caused by uneven material. Through homogenization annealing at high temperature for a long time (such as 490℃ for 10 hours), Cu atom diffusion is promoted, eliminating intracrystalline segregation and non-equilibrium phases, reducing residual stress and making subsequent processing smoother with significantly reduced crack risk. Through solid solution heat treatment at 505℃ for 1 hour, the strengthening phase is dissolved into the α-Al matrix, forming a supersaturated solid solution and laying the foundation for subsequent strength improvement. By introducing high-density dislocations through 60% deformation, driving force is provided for recrystallization, promoting grain refinement. The rolled aluminum plate is machined into a 0.5-1.5mm thin plate to reduce the influence of volume effect on grain uniformity and ensure organizational stability. Through high temperature short time heat treatment at 385-400℃ for 0.5-1 minute, recrystallization is precisely controlled, the grain is kept sub-micron, the precipitation phase is prevented from coarsening, and the strengthening effect is maintained.

[0025] 3.Through the optimized combination of the above steps, the present invention successfully forms a uniform sub-micron equiaxed crystal structure in Al-Cu alloy, significantly improving the strength and toughness of the material while retaining excellent processing performance. Compared with traditional processes, this method is low in cost, high in efficiency and easy to operate, providing an innovative path for the fine-grain strengthening of aluminum alloys, especially suitable for aerospace, automotive and other fields, promoting the widespread application of high-performance aluminum alloys, and having important significance for revealing the evolution law of aluminum alloy microstructure and optimizing processing parameters.

[0026] Other advantages, objects, and features of the present invention will be in part apparent and in part pointed out hereinafter. Those skilled in the art will appreciate the teachings and variations thereof upon the study of the following specification and the associated drawings. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to make the purpose, technical scheme and advantages of the present invention clearer, the preferred detailed description of the present invention will be made below in combination with the drawings, in which:

[0028] Figure 1A flow chart of a processing method for obtaining sub-micron equiaxed crystal structure in Al-Cu alloy provided by an embodiment of the present application is shown in the figure;

[0029] Figure 2 A schematic diagram of the specification and rolling deformation of the Al-Cu alloy ingot after forging treatment in an embodiment of the present application is shown in the figure;

[0030] Figure 3 A TEM characterization diagram of the microstructure of the Al-Cu alloy sample after rolling treatment in an embodiment of the present application is shown in the figure;

[0031] Figure 4 A TEM characterization diagram of the microstructure of the Al-Cu alloy sample after heat treatment with different parameters in an embodiment of the present application is shown in the figure. DETAILED DESCRIPTION

[0032] The advantages and effects of the present application can be easily understood by those skilled in the art from the description of the embodiments of the present application. The present application can also be implemented or applied in different specific embodiments, and the details in the description can be modified or changed based on different views and applications without departing from the spirit of the present application. It should be noted that the diagrams provided in the following embodiments only illustrate the basic concept of the present application in a schematic manner, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0033] The figures are only used for illustrative explanation, and the representation is only a schematic diagram, not a physical diagram, and should not be understood as a limitation of the present application. In order to better illustrate the embodiments of the present application, some components in the figures may be omitted, enlarged or reduced, and do not represent the actual size of the product. It is understandable for those skilled in the art that some well-known structures and their descriptions in the figures may be omitted.

[0034] The same or similar reference numerals in the figures of the embodiments of the present application correspond to the same or similar components; in the description of the present application, it should be understood that the orientation or position relationship indicated by the terms "upper", "lower", "left", "right", "front", "back" and the like is based on the orientation or position relationship shown in the figures, and is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, therefore the terms describing the position relationship in the figures are only used for illustrative explanation, and should not be understood as a limitation of the present application. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0035] Embodiment 1

[0036] As Figure 1As shown, the present embodiment provides a processing method for obtaining a sub-micron equiaxed crystal structure in an Al-Cu alloy, the specific steps are as follows:

[0037] 1. Raw material preparation

[0038] Select Al-4% Cu alloy ingot as raw material. The ingot is prepared by smelting ultra-high purity aluminum with a purity of 99.9996% and 4wt.% oxygen-free high-conductivity copper.

[0039] 2. Forging treatment

[0040] The prepared Al-Cu alloy ingot is placed in a forging device and forged into an aluminum plate (Al-Cu alloy plate) with regular shape and uniform thickness at a suitable temperature. The size of the aluminum plate after forging is 300mm (long) x 200mm (wide) x 50mm (thick).

[0041] 3. Homogenization annealing

[0042] The aluminum plate after forging is placed in a box-type resistance furnace for homogenization annealing treatment. The annealing temperature is set to 490℃, and the holding time is 10 hours. This step aims to promote the uniform diffusion of Cu atoms in the aluminum matrix, eliminate intragranular segregation and non-equilibrium phases, and reduce the residual stress in the ingot.

[0043] 4. Solution heat treatment

[0044] After homogenization annealing is completed, the aluminum plate is transferred to another heat treatment furnace (the current box-type resistance furnace) for solution heat treatment. The solution temperature is set to 505℃, and the holding time is 1 hour, so that the strengthening phase is fully dissolved into the α-Al matrix to form a supersaturated solid solution. After the heat treatment is completed, the aluminum plate is immediately taken out and placed in room temperature water for rapid cooling to room temperature.

[0045] 5. Room temperature rolling

[0046] The aluminum plate after solution heat treatment is placed in a rolling mill for room temperature rolling processing under room temperature conditions, and the rolling deformation amount is controlled to be 60%, to obtain a rolled Al-Cu alloy plate. This step introduces high-density dislocations to provide driving force for the subsequent recrystallization process;

[0047] As shown in Figure 2 The size of the Al-Cu alloy ingot after forging treatment and the rolling deformation amount are shown in the figure. The initial size of the aluminum plate after forging is 300mm (long) x 200mm (wide) x 50mm (thick), the rolling deformation amount is 60%, and the size of the rolled Al-Cu alloy plate after rolling is 300mm (long) x 300mm (wide) x 20mm (thick).

[0048] 6. Mechanical processing

[0049] The rolled aluminum plate was cut into thin plates with a size of 10 mm (length) x 10 mm (width) x 1 mm (thickness) using a wire cutting device to reduce the volume effect on the subsequent grain uniformity.

[0050] 7High-temperature short-time heat treatment

[0051] The processed thin plate was placed in a heat treatment furnace for high-temperature short-time heat treatment, with a heat treatment temperature of 385°C and a holding time of 1 minute. This step controls the recrystallization process to maintain the grain size at a sub-micron level while avoiding the coarsening of precipitates. After heat treatment, the thin plate was immediately removed and placed in room temperature water for rapid cooling, resulting in an Al-Cu alloy with a sub-micron equiaxed crystal structure.

[0052] The rolled Al-Cu alloy sample and the heat-treated Al-Cu thin plate sample were characterized using a transmission electron microscope (TEM), as shown in Figure 3 It can be seen that the internal microstructure of the as-rolled sample is a lamellar structure, with grains elongated along the rolling direction, consistent with the microstructure characteristics of plastic deformation of aluminum alloys. Figure 4 The TEM image of the thin plate sample held at 385°C for 1 minute is shown on the left. It can be seen that the microstructure is equiaxed, with an average grain size of 521 nm measured using the intercept method.

[0053] Results: Microstructure characterization of the heat-treated thin plate by transmission electron microscopy (TEM) showed that the grains of the thin plate were equiaxed, with an average grain size of 521 nm, successfully obtaining a sub-micron equiaxed crystal structure.

[0054] Example 2

[0055] This example provides a variant of the processing method for obtaining a sub-micron equiaxed crystal structure in an Al-Cu alloy, which mainly adjusts the temperature parameters of the high-temperature short-time heat treatment compared to Example 1. The specific steps are as follows:

[0056] The raw material preparation, forging treatment, homogenization annealing, solid solution heat treatment, room temperature rolling and mechanical processing are the same as in Example 1;

[0057] The high-temperature short-time heat treatment is

[0058] The thin plate was placed in a heat treatment furnace for high-temperature short-time heat treatment, with a heat treatment temperature of 400°C and a holding time of 1 minute. The increase in temperature aims to explore the variation of grain size. After heat treatment, the thin plate was immediately removed and placed in room temperature water for rapid cooling, resulting in an Al-Cu alloy with a sub-micron equiaxed crystal structure.

[0059] The heat-treated Al-Cu thin plate sample was characterized using a transmission electron microscope (TEM), as shown inFigure 4 The TEM image of the thin plate sample held at 400℃ for 1min shows equiaxed grains with an average grain size of 899nm, which is in the sub-micron range.

[0060] Results: The microstructure of the heat-treated thin plate was characterized by transmission electron microscopy (TEM), and equiaxed grains were observed with an average grain size of 899nm. Although the grain size increased compared to Example 1, it was still in the sub-micron range, verifying the feasibility and flexibility of the process.

[0061] The above Examples 1 and 2 successfully obtained sub-micron equiaxed grain structure in Al-Cu alloy ingots through forging, homogenization annealing, solid solution heat treatment, room temperature rolling, mechanical processing and high temperature short time heat treatment. By adjusting the temperature of high temperature short time heat treatment (such as 385℃ and 400℃), the grain size can be effectively controlled, and equiaxed grain structures with average grain sizes of 521nm and 899nm respectively are obtained. These examples demonstrate the operability and diversity of the technical solution of the present application, which can meet the needs of different application scenarios.

[0062] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application and are not limiting. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced equivalently without departing from the spirit and scope of the present application, which should be covered by the scope of the claims of the present application.

Claims

1. A processing method for obtaining submicron equiaxed grain structure in Al-Cu alloy, characterized in that: The following steps are involved: (a) Forging an Al-Cu alloy ingot into an Al-Cu alloy plate by a forging process; (b) homogenizing annealing and solution heat treatment of the Al-Cu alloy plate obtained by forging; (c) rolling the heat-treated Al-Cu alloy sheet at room temperature to obtain a rolled Al-Cu alloy sheet; (d) machining the rolled Al-Cu alloy sheet into a thin plate; (e) The thin plate is subjected to a high temperature and short time heat treatment to form a uniform submicron equiaxed grain structure in the thin plate.

2. The processing method according to claim 1, characterized in that: The Al-Cu alloy plate in step (a) is an aluminum plate with regular shape and uniform thickness.

3. The processing method according to claim 1, characterized in that: The homogenization annealing in step (b) is carried out at 490° C. for 10 hours.

4. The processing method according to claim 1, characterized in that: The solution heat treatment in step (b) is carried out at 505° C. for 1 hour, and after the solution heat treatment is completed, the Al-Cu alloy plate is cooled to room temperature by water cooling.

5. The processing method according to claim 1, characterized in that: The room temperature rolling deformation in step (c) is 60%.

6. The processing method according to claim 1, characterized in that: The thickness of the thin plate obtained by mechanical processing in step (d) is 0.5-1.5 mm.

7. The processing method according to claim 1, characterized in that: The temperature range of the high temperature short time heat treatment in step (e) is 385-400° C., and the holding time is 0.5-1 minute.

8. The processing method according to claim 1, characterized in that: The Al-Cu alloy ingot is prepared from pure aluminum with a purity of 99.9996% and 4 wt.% of oxygen-free high-conductivity copper.

9. The processing method according to claim 1, characterized in that: The grain size of the submicron equiaxed crystal structure obtained after step (e) is 100-1000 nm, and the microstructure presents a uniform equiaxed crystal structure.

10. An Al-Cu alloy, characterized in that: The Al-Cu alloy is processed by the processing method described in any one of claims 1 to 9.

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