High-strength and high-plasticity heterogeneous grain structure Al-Cu alloy material and preparation method thereof

Abstract

The invention discloses a preparation method of a high-strength and high-plasticity Al-Cu alloy with a heterogeneous grain structure, and particularly relates to the field of aluminum alloys. Comprising the following steps: respectively weighing raw materials according to dosage; cu, Mn, Sc, Ti, Al and Mg are smelted, and an Al-Cu series alloy cast ingot is obtained; the alloy ingot is subjected to multi-pass hot rolling deformation and multi-pass cold rolling deformation, and a cold-rolled plate is obtained; and the cold-rolled plate is sequentially subjected to annealing, solid solution treatment and aging treatment, and the Al-Cu alloy is obtained. By regulating and controlling technological parameters of rolling deformation and heat treatment, a plurality of strengthening mechanisms including heterogeneous deformation induction strengthening are introduced, so that the strength and plasticity of the alloy are greatly improved.

Description

Technical Field

[0001] The present application relates to the field of aluminum alloy materials, and in particular to a high-strength and plastic heterogeneous grain structure Al-Cu alloy material and a preparation method thereof. Background Art

[0002] Aluminum alloys are widely used in aerospace, weapons and equipment, transportation and other fields due to their excellent properties such as light weight and high strength. Among them, Al-Cu alloys, as typical 2-series heat-treatable and strengthened aluminum alloys, have become the main choice for high-strength and lightweight structural components due to their excellent mechanical properties and corrosion resistance. However, the increasingly harsh service environment and complex design requirements have put forward higher performance requirements for Al-Cu alloys. Existing commercial Al-Cu alloys still face technical challenges in improving the synergy between strength and plasticity. Traditional strengthening methods, such as plastic deformation treatment and heat treatment, can significantly improve the strength of the alloy, but are usually accompanied by a decrease in plasticity. In addition, grain homogenization treatment methods have limited effect in further improving material properties, especially fatigue strength and fracture toughness under complex working conditions.

[0003] In recent years, heterogeneous grain structures have shown great potential in achieving a balance between strength and plasticity. Heterogeneous grain structures refer to a composite structure in which grains of different sizes coexist within a material. This structure can effectively hinder dislocation movement, enhance strength, and maintain good plasticity. Its core mechanism lies in the synergistic effect of different microstructural features within the material, including the coupling of microscopic behaviors such as dislocation slip, twinning, phase transformation, and multi-scale precipitation. This design idea provides a way to break through the limitations of traditional fine grain strengthening methods.

[0004] At present, the preparation of heterogeneous grain structures mainly relies on severe plastic deformation technologies, such as powder metallurgy, high-pressure torsion, cumulative roll-to-roll welding, and equal channel angular extrusion. However, the molding process of these technologies is complex and difficult to compete with traditional technologies, which limits the feasibility of their large-scale application. Especially for Al-Cu alloys, due to their high stacking fault energy (166mJ / m²) and sensitivity to deformation temperature and strain, it is difficult to control the heterogeneous grain structure. Al-Cu prepared by the above plastic deformation technology has the problem of low strength and plasticity. Summary of the invention

[0005] The main purpose of the present application is to provide a method for preparing a high-strength and plastic heterogeneous grain structure Al-Cu alloy, aiming to solve the problems of low strength and plasticity of existing Al-Cu alloys.

[0006] To achieve the above objectives, the present application provides a high-strength and ductile heterogeneous grain structure Al-Cu alloy, wherein the raw materials of the alloy include the following components by mass fraction: 5.0-6.5% Cu, 0.5-0.7% Mn, 0.4-0.6% Mg, 0.1-0.3% Sc, 0.15-0.35% Ti, and the balance is Al.

[0007] To achieve the above-mentioned purpose, the present application also provides a preparation method of the high-strength and ductile heterogeneous grain structure Al-Cu alloy as mentioned above, comprising: weighing the raw materials of Cu, Mn, Sc, Ti, Al, and Mg according to the amount; smelting the raw materials of Cu, Mn, Sc, Ti, Al, and Mg to obtain an Al-Cu alloy ingot; performing multiple hot rolling deformation on the alloy ingot to obtain a hot-rolled plate, wherein the hot rolling temperature is 450-490°C, and the total reduction of the multiple hot rolling deformations is 65-73%; performing multiple cold rolling deformation on the hot-rolled plate to obtain a cold-rolled plate, wherein the total reduction in the multiple cold rolling deformations is 17-25%; and sequentially performing annealing, solid solution treatment, and aging treatment on the cold-rolled plate to obtain an Al-Cu alloy.

[0008] Optionally, before the alloy ingot is subjected to multiple hot rolling deformations, the alloy ingot is placed at a hot rolling temperature for heat preservation.

[0009] Optionally, after each hot rolling deformation, the obtained sample is annealed and cooled, and the reduction in each pass is greater than or equal to 5%.

[0010] Optionally, during the annealing process, the annealing temperature is 400-450°C, and the holding time is 10-20h; during the solution process, the solution temperature is 510-540°C, and the holding time is 0.5-2h; during the aging process, the aging temperature is 165-185°C, and the holding time is 4-12h.

[0011] Optionally, the preparation process of the Al-Cu alloy ingot includes: mixing raw materials of Cu, Mn, Sc, Ti and Al, heating and melting them at 710-750°C, adding raw materials of Mg and melting them when the temperature is reduced to 680-700°C, continuing to heat up to 710-750°C, refining for 15-30 minutes, and adding a slag-forming agent to obtain a molten liquid; cooling the molten liquid to 700-720°C, and pouring the molten liquid into a mold to obtain an Al-Cu alloy ingot.

[0012] Optionally, the raw materials of each component are simple substances or intermediate alloys.

[0013] Optionally, the raw material of Cu is Al-50Cu master alloy, the raw material of Mn is Al-10Mn master alloy, the raw material of Sc is Al-2Sc master alloy, the raw material of Al is Al ingot, the raw material of Ti is Al-5Ti-B refiner, and the raw material of Mg is Mg ingot.

[0014] Optionally, the content of the slag-forming agent is 0.15-0.3% of the total mass of the raw materials.

[0015] Optionally, before mixing the raw materials of Cu, Mn, Sc, Ti and Al, the raw materials of each component are cleaned and dried, the drying temperature is 150-200° C., and the drying time is 1-3 hours.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The high-strength and plastic heterogeneous grain structure Al-Cu alloy of the present invention has a heterogeneous grain structure composed of grains of different sizes, which effectively improves the back stress strengthening effect of the alloy; at the same time, the Al in the alloy 20 The precipitation of Cu2Mn3 phase, Al2Cu phase and Al2CuMg phase significantly enhances the yield strength and tensile strength of the material, making the alloy have higher strength while maintaining excellent plasticity. The preparation method of the high-strength and plastic heterogeneous grain structure Al-Cu alloy of the present invention introduces a variety of strengthening mechanisms including heterogeneous deformation induced strengthening by regulating rolling deformation and heat treatment process parameters, thereby achieving a significant improvement in alloy strength and plasticity. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a schematic flow chart of a method for preparing the above-mentioned high-strength and ductile heterogeneous grain structure Al-Cu alloy of the present application; Figure 2 This is a microstructure image (SEM) of the cold-rolled sheet prepared in Example 1 of the present application; Figure 3 The microstructure diagram (EBSD) of the heterogeneous grain structure Al-Cu alloy of Example 1 of the present application; Figure 4 The engineering stress-strain curve of the heterogeneous grain structure Al-Cu alloy of Example 1 of the present application; Figure 5 This is a microstructure image (SEM) of the cold-rolled sheet prepared in Example 2 of the present application; Figure 6 This is the microstructure diagram (EBSD) of the Al-Cu alloy prepared in Comparative Example 1 of the present application.

[0018] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solutions and advantages of this application clearer, the technical solutions in this application will be clearly and completely described below in conjunction with the drawings in this application. Obviously, the described embodiments are part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0020] The first embodiment of the present invention provides a high-strength and ductile Al-Cu alloy with a heterogeneous grain structure. The raw materials of the alloy include the following components by mass fraction: 5.0-6.5% Cu, 0.5-0.7% Mn, 0.4-0.6% Mg, 0.1-0.3% Sc, 0.15-0.35% Ti, and the balance is Al.

[0021] Among them, there may be some inevitable impurities in the Al-Cu alloy, including Fe and Si, and the mass percentage of the two elements is less than 0.1%.

[0022] In the Al-Cu alloy of this embodiment, Cu is the main alloying element. After solution treatment, most of the eutectic phase θ-Al2Cu in the microstructure is dissolved, which produces a solid solution strengthening effect on the alloy. However, once the Cu content exceeds 6.5%, the solidification range of the alloy will continue to widen, which is easy to form casting defects. Mn is a common microalloying element in Al-Cu alloys. In addition to forming T Mn -Al 20 In addition to Cu2Mn3 phase, it can also reduce the harmful effects of impurities Fe and Si. However, when the Mn content is too high, it will cause the primary T phase-Al 20The Cu2Mn3 phase is aggregated in large quantities at the grain boundaries and is difficult to dissolve, which is detrimental to the mechanical properties of the alloy. The solubility of Mg in Al can reach 14.9% (mass percentage), and its atomic radius is larger than that of Al. When Mg atoms are dissolved into the Al matrix, due to the difference in atomic radius, severe lattice distortion occurs. After heat treatment, S-Al2CuMg phase can be formed, which significantly improves the room temperature mechanical properties of the alloy. However, when the Mg content is too high, Al2Cu-Al2CuMg low-melting point eutectic will be formed, which is easy to increase the risk of overburning. Sc, as a common transition element in Al-Cu alloys, can form a Sc-containing precipitation phase, which can serve as a heterogeneous nucleation point for the Al2Cu precipitation phase, promote its large-scale precipitation, and effectively play a precipitation strengthening role. In addition, the Sc element can be segregated at the interface between the precipitation phase and the matrix, inhibiting the growth and coarsening of the precipitation phase, and significantly improving the mechanical properties and thermal stability of the alloy. Adding trace amounts of Ti and B to Al-Cu alloys to form Al3Ti and TiB2 phases can serve as nucleation points for the crystallization of α-Al solid solution and effectively refine the grains, narrow the crystallization temperature range, improve the heat treatment effect, and help improve the mechanical properties and prevent the formation of shrinkage and hot cracking tendencies.

[0023] The second embodiment of the present invention provides a method for preparing the above-mentioned high-strength and ductile heterogeneous grain structure Al-Cu alloy, such as Figure 1 As shown, the specific steps include: Step S1, weighing raw materials of Cu, Mn, Sc, Ti, Al, and Mg according to the amount, washing the raw materials of each component, placing them in an oven, and drying them at 150-200° C. for 1-3 hours; Exemplarily, the raw materials of each component are simple substances or master alloys. For example, the raw material of Cu is Al-50Cu master alloy, the raw material of Mn is Al-10Mn master alloy, the raw material of Sc is Al-2Sc master alloy, the raw material of Al is Al ingot, the raw material of Ti is Al-5Ti-B refiner, and the raw material of Mg is Mg ingot. The purity of the raw materials of the above components is not less than 99.9%, which can ensure the accurate proportion of the raw materials of each component in the alloy and introduce less impurities, thereby improving the quality of the alloy ingot.

[0024] Step S2, adding raw materials of Cu, Mn, Sc, Ti and Al into a crucible preheated to 400-500° C., mixing, and heating and melting at 710-750° C. to obtain a first mixture, wherein the first mixture includes a precipitated phase containing Sc, Al3Ti and TiB2 phases; The crucible is a graphite crucible with a ZnO coating on the surface.

[0025] Step S3, cooling the temperature of the first mixture to 680-700° C., and adding a raw material of Mg to melt the raw material of Mg to form a S-Al2CuMg phase, thereby obtaining a second mixture; In this embodiment, since Mg is easily burned during the high-temperature smelting process, it is added at the end and the temperature is lowered to control the amount of Mg burned.

[0026] Step S4, heating the second mixture to 710-750° C. and keeping the temperature for 15-20 minutes, refining the second mixture in an argon atmosphere for 15-30 minutes, adding a slag-forming agent, stirring the mixture mechanically, standing the mixture for 5 minutes, and removing the scum to obtain a molten liquid; Among them, the content of slag-forming agent is 0.15-0.3% of the total mass of raw materials.

[0027] Step S5, cooling the molten liquid to 700-720° C., standing for 5-15 minutes, and pouring the molten liquid into a metal mold to obtain an Al-Cu alloy ingot after solidification; Step S6, placing the alloy ingot at 450-490°C for 1-2h to eliminate microsegregation and stress, performing multiple hot rolling deformation on the alloy ingot at this temperature, and after each hot rolling deformation, annealing the obtained sample at 450-490°C for 10-20 min, and then water cooling to room temperature, so that the reduction in each pass is greater than or equal to 5%, to obtain a hot-rolled plate, and when multiple hot rolling deformations are performed, the total thickness reduction is 65-73%.

[0028] Step S7, performing multiple cold rolling deformations on the hot-rolled sheet to obtain a cold-rolled sheet; during the multiple cold rolling deformations, the total thickness reduction is 17-25%; Step S8, anneal the cold-rolled sheet at 400-450℃ for 10-20h. Annealing can fully release deformation energy, annihilate or rearrange dislocations, and complete the recovery and recrystallization process. In addition, annealing can precipitate Cu, Mg and Ag-rich precipitates (such as θ' ​​phase, Ω phase, S' phase, etc.) in the matrix. The formation of these phases can effectively improve the strength and stability of the alloy. Then, solution treatment is performed at 510-540℃ for 0.5-2h to increase the concentration of the supersaturated solid solution, improve the grain boundary characteristics, eliminate stress, and enhance the subsequent aging hardening potential. In addition, the T formed in the solution treatment stage Mn -Al 20 Cu2Mn3 phase can promote the precipitation of aging strengthening phase and improve the strength of the alloy. Finally, aging treatment is performed at 165-185℃ for 4-12h to obtain fine dispersed Al2Cu strengthening phase, and finally the preparation of heterogeneous Al-Cu alloy with excellent strength and plasticity is realized.

[0029] In general, under the action of external load, heterogeneous grain structure will cause uneven deformation between large and small grains, thereby generating strain gradient near the grain boundary, thereby forming geometrically necessary dislocations to adapt to the strain gradient, and the continuous accumulation of geometrically necessary dislocations will produce heterogeneous deformation induced strengthening near the grain boundary. In addition, higher stress will also activate more slip systems, promote dislocation accumulation and interaction, and enable the alloy to have stronger work hardening ability and deformation ability. The cast Al-Cu alloy of uniform grains obtained in the above manner presents an inverted relationship between its strength and plasticity, and its yield strength is generally 300-350 MPa, and the elongation is only 7-10%. In this embodiment, by regulating and controlling rolling deformation and heat treatment process parameters, a variety of strengthening mechanisms including heterogeneous deformation induced strengthening are introduced, thereby achieving a substantial increase in alloy strength and plasticity.

[0030] Example 1 Al-Cu alloys include, by mass percentage: Cu 6.5%, Mn 0.7%, Mg 0.5%, Sc 0.3%, Ti0.2%, and the balance is Al; Step S1, weighing pure Al ingot, Al-50Cu master alloy, Al-10Mn master alloy, Al-2Sc master alloy, pure Mg ingot and Al-5Ti-B grain refiner according to the above proportions, washing the above raw materials, placing them in an oven, and drying them at 150° C. for 1 hour; Step S2, adding pure Al ingot, Al-50Cu master alloy, Al-10Mn master alloy, Al-2Sc master alloy and Al-5Ti-B grain refiner into a crucible preheated to 400° C., mixing, heating to 750° C. for melting, and stirring continuously to make the components uniform, to obtain a first mixture; Step S3, cooling the temperature of the first mixture to 690° C., adding a raw material of Mg to melt the raw material of Mg, and obtaining a second mixture; Step S4, heating the second mixture to 730°C, introducing argon gas for refining, rotating and blowing for 15 minutes, adding 0.2% of a slag-forming agent, stirring continuously to make the melt slag as much as possible, then keeping the temperature for 10 minutes, and then removing the scum on the surface of the melt to obtain a molten liquid; Step S5, cooling the molten liquid to 710° C., standing for 10 minutes, and pouring the molten liquid into a metal mold preheated to 230° C., and cooling in air to obtain an Al-Cu alloy ingot; Step S6, placing the alloy ingot at 490°C for 2 hours, and performing multiple hot rolling deformations on the alloy ingot at this temperature; after each hot rolling deformation, annealing the obtained sample at 490°C for 10 minutes, and then water cooling to room temperature, with a total reduction of 65%, to obtain a hot-rolled plate; Step S7, subjecting the hot-rolled sheet to multiple cold-rolling deformations, with a total reduction of 20%, to obtain a cold-rolled sheet; Step S8, first annealing the cold-rolled sheet at 415°C for 20 hours, and water cooling to room temperature; then solution treating at 520°C for 0.5 hours, and water cooling to room temperature; finally aging treating at 185°C for 6 hours, and air cooling to room temperature, thereby obtaining an Al-Cu alloy with a heterogeneous structure.

[0031] The cold-rolled sheet obtained in step S7 of this embodiment is tested, and its microstructure is as follows: Figure 2 , Figure 2 The electron backscatter diffraction image of the alloy in the cold-rolled state shows that there is still a small amount of micron-sized eutectic phase on the grain boundary, which can serve as nucleation points for recrystallization and promote the formation of small grains. The Al-Cu alloy obtained in this embodiment was tested, and its microstructure is shown in FIG. Figure 3 As shown, Figure 3 The EBSD image clearly reflects that the preparation process of Example 1 can be used to control the uneven grain structure. According to GB / T228.1-2010 standard, the alloy is subjected to room temperature tensile test, and the corresponding engineering stress-strain curve is as follows: Figure 4 Observation Figure 4 It can be found that the alloy has outstanding room temperature mechanical properties, with yield strength, tensile strength and elongation of 470 MPa, 531 MPa and 12%, respectively.

[0032] Example 2 Al-Cu alloys include, by mass percentage: Cu 5%, Mn 0.6%, Mg 0.6%, Sc 0.1%, Ti 0.3%, and the balance is Al; Step S1, weighing pure Al ingot, Al-50Cu master alloy, Al-10Mn master alloy, Al-2Sc master alloy, pure Mg ingot and Al-5Ti-B grain refiner according to the above proportions, washing the above raw materials, placing them in an oven, and drying them at 170° C. for 1 hour; Step S2, adding pure Al ingot, Al-50Cu master alloy, Al-10Mn master alloy, Al-2Sc master alloy and Al-5Ti-B grain refiner into a crucible preheated to 440° C., mixing, heating to 750° C. for melting, and stirring continuously to make the components uniform, to obtain a first mixture; Step S3, cooling the temperature of the first mixture to 690° C., adding a raw material of Mg to melt the raw material of Mg, and obtaining a second mixture; Step S4, heating the second mixture to 710°C, introducing argon gas for refining, rotating and blowing for 30 minutes, adding 0.3% of a slag-forming agent, stirring continuously to make the melt slag as much as possible, then keeping the temperature for 30 minutes, and then removing the scum on the surface of the melt to obtain a molten liquid; Step S5, cooling the molten liquid to 720° C., standing for 10 minutes, and pouring the molten liquid into a metal mold preheated to 250° C., and cooling in air to obtain an Al-Cu alloy ingot; Step S6, placing the alloy ingot at a preset temperature for 2 hours, performing multiple hot rolling deformations on the alloy ingot at 490°C, and after each hot rolling deformation, annealing the obtained sample at 490°C for 10 minutes, and then water cooling to room temperature, with a total reduction of 70%, to obtain a hot-rolled plate; Step S7, subjecting the hot-rolled sheet to multiple cold-rolling deformations, with a total reduction of 17%, to obtain a cold-rolled sheet; Step S8, first annealing the cold-rolled sheet at 430°C for 10 hours, and water cooling to room temperature; then solution treating at 530°C for 0.5 hours, and water cooling to room temperature; finally aging treating at 185°C for 6 hours, and air cooling to room temperature, thereby obtaining an Al-Cu alloy with a heterogeneous grain structure and uneven grain size.

[0033] The Al-Cu alloy obtained in this embodiment was tested, and the microstructure of the alloy in cold-rolled state is as follows: Figure 5 As shown, it can be found that when the Sc content is low (0.1%), the grain size of the alloy is larger and the heterogeneous grain structure characteristics are not prominent enough.

[0034] Example 3 Al-Cu alloys include, by mass percentage: Cu 5%, Mn 0.5%, Mg 0.4%, Sc 0.3%, Ti 0.3%, and the balance is Al; Step S1, weighing pure Al ingot, Al-50Cu master alloy, Al-10Mn master alloy, Al-2Sc master alloy, pure Mg ingot and Al-5Ti-B grain refiner according to the above proportions, the weight of each part of the raw materials is accurate to 0.01 g, washing the above raw materials, placing them in an oven, and drying them at 200° C. for 1 h; Step S2, adding pure Al ingot, Al-50Cu master alloy, Al-10Mn master alloy, Al-2Sc master alloy and Al-5Ti-B grain refiner into a crucible preheated to 400° C., mixing, heating to 710° C. for melting, and stirring continuously to make the components uniform, to obtain a first mixture; Step S3, cooling the temperature of the first mixture to 690° C., adding a raw material of Mg to melt the raw material of Mg, and obtaining a second mixture; Step S4, heating the second mixture to 750°C, introducing argon gas for refining, rotating and blowing for 30 minutes, adding 0.3% of a slag-forming agent, stirring continuously to make the melt slag as much as possible, then keeping the temperature for 30 minutes, and then removing the scum on the surface of the melt to obtain a molten liquid; Step S5, cooling the molten liquid to 720° C., standing for 10 minutes, and pouring the molten liquid into a metal mold preheated to 210° C., and cooling in air to obtain an Al-Cu alloy ingot; Step S6, placing the alloy ingot at a preset temperature for 2 hours, performing multiple hot rolling deformations on the alloy ingot at 490°C, and after each hot rolling deformation, annealing the obtained sample at 490°C for 10 minutes, and then water cooling to room temperature, with a total reduction of 73%, to obtain a hot-rolled plate; Step S7, subjecting the hot-rolled sheet to multiple cold-rolling deformations, with a total reduction of 25%, to obtain a cold-rolled sheet; Step S8, first annealing the cold-rolled sheet at 450°C for 10 hours, and water cooling to room temperature; then solution treating at 530°C for 1 hour, and water cooling to room temperature; finally aging treating at 185°C for 6 hours, and air cooling to room temperature, thereby obtaining an Al-Cu alloy with a heterogeneous structure.

[0035] Comparative Example 1 The chemical composition of a high-strength and ductile heterogeneous grain structure Al-Cu alloy is Cu 6.5%, Mn 0.7%, Mg 0.5%, Ti 0.2%, and the balance is Al. That is, compared with Example 1, the alloy does not contain Sc element, and the other components and preparation method are the same as those of Example 1. Figure 6 The microstructure of the alloy prepared in this comparative example is shown in FIG. Figure 3 ), the microstructure of the alloy prepared in Comparative Example 1 is mainly composed of uniform fibrous grains, and almost no smaller equiaxed crystals appear, indicating that it is difficult to control the heterogeneous grain structure with uneven size when Sc element is not added to the alloy.

[0036] Comparative Example 2 The chemical composition of a high-strength and ductile heterogeneous grain structure Al-Cu alloy is the same as that of Example 1, except that the preparation process is different. The hot-rolled plate obtained in step S6 is not subjected to cold rolling deformation, but is directly subjected to annealing, solution treatment and aging treatment processes according to step S8 of Example 1, thereby obtaining a structure with larger grains and lower dislocation density.

[0037] Comparative Example 3 The chemical composition of a high-strength and ductile heterogeneous grain structure Al-Cu alloy is the same as that of Example 3.

[0038] S1-S7 are the same as in Example 1.

[0039] S8, subjecting the cold-rolled sheet obtained in step S7 to a conventional T6 heat treatment, specifically in the following manner: First, the alloy was solution treated at 530 °C for 1 h and then water cooled to room temperature. Then, it was aged at 185 °C for 6 h and then air cooled to room temperature.

[0040] According to the examples and comparative examples, a variety of high-strength and plastic heterogeneous grain structure Al-Cu alloys were prepared. According to GB / T228.1-2010 standard, the room temperature tensile mechanical properties of the alloys of Examples 1-3 and Comparative Examples 1-3 were measured, and the results are shown in Table 1.

[0041]

[0042] As can be seen from the above table, the room temperature tensile mechanical properties of Example 1 are the most excellent. The strength of the alloy in Example 2 is slightly lower than that in Example 1, while the elongation is slightly improved. This is because on the one hand, the Sc content is reduced (0.1%), resulting in a decrease in the number of Al3Sc precipitation phases and a decrease in density, which causes the recrystallized grains of the alloy to grow. In addition, the excessive diffusion of trace alloying elements due to the high solid solution temperature causes the grains to grow, thereby slightly reducing the strength; on the other hand, the increase in grain size reduces the sliding resistance of the grain boundaries, and the structure is more uniform after annealing, so that the residual stress of the alloy after rolling is released more fully, and the plasticity is improved. In Example 3, the annealing temperature is increased to 450°C. The higher annealing temperature accelerates the recrystallization process, which may cause the grains to grow further, thereby reducing the grain boundary strengthening effect and reducing the strength of the alloy. Comparative Example 1 does not contain the Sc element, so the Al3Sc strengthening phase is not formed, and multiple effects such as fine grain strengthening and solid solution strengthening fail, resulting in a significant increase in dislocation movement and grain growth, resulting in a sharp decrease in alloy strength and an increase in plasticity. The alloy obtained in Comparative Example 2 without cold rolling has a low dislocation density, reduced deformation energy storage, and insufficient precipitation power of the strengthening phase; on the other hand, the size of the recrystallized grains after hot rolling is large, and it is difficult to effectively refine the grains only through subsequent annealing and solution treatment, so the strength is low. Comparative Example 3 did not anneal the rolled alloy, at this time the residual stress after cold rolling was not released, and the dislocation distribution was uneven, resulting in uneven grain coarsening effect and precipitation phase distribution, reducing the strength and plasticity of the alloy.

[0043] The present invention successfully prepares a high-strength and plastic Al-Cu alloy with a heterogeneous grain structure by optimizing the alloy composition and precisely controlling the preparation process. The heterogeneous grain structure is composed of grains of different sizes, which effectively improves the back stress strengthening effect of the alloy. 20The precipitation of Cu2Mn3 phase, Al2Cu phase and Al2CuMg phase significantly enhances the yield strength and tensile strength of the material, making the alloy have higher strength while maintaining excellent plasticity. The experimental results show that the Al-Cu alloy prepared by the present invention has a wide range of engineering application value, especially in the field of structural materials with both high strength and plasticity.

[0044] The above are only preferred embodiments of the present application, and are not intended to limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A high-strength and ductile heterogeneous grain structure Al-Cu alloy, characterized in that: The raw materials of the alloy include the following components by mass fraction: 5.0-6.5% Cu, 0.5-0.7% Mn, 0.4-0.6% Mg, 0.1-0.3% Sc, 0.15-0.35% Ti, and the balance is Al.

2. A method for preparing the high-strength and ductile heterogeneous grain structure Al-Cu alloy as claimed in claim 1, characterized in that: include: Weigh the raw materials of Cu, Mn, Sc, Ti, Al and Mg according to the usage; The raw materials of Cu, Mn, Sc, Ti, Al and Mg are smelted to obtain Al-Cu alloy ingots; The alloy ingot is subjected to multiple hot rolling deformations to obtain a hot rolled plate, wherein the hot rolling temperature is 450-490° C. and the total reduction of the multiple hot rolling deformations is 65-73%; The hot-rolled sheet is subjected to multiple cold rolling deformations to obtain a cold-rolled sheet, wherein the total reduction in the multiple cold rolling deformations is 17-25%; The cold-rolled sheet is subjected to annealing, solution treatment and aging treatment in sequence to obtain an Al-Cu alloy.

3. The method for preparing the high-strength and ductile heterogeneous grain structure Al-Cu alloy according to claim 2, characterized in that: Before the alloy ingot is subjected to multiple hot rolling deformations, the alloy ingot is placed at a hot rolling temperature for heat preservation.

4. The method for preparing the high-strength and ductile heterogeneous grain structure Al-Cu alloy according to claim 2, characterized in that: After each hot rolling deformation, the obtained sample is annealed and cooled, and the reduction in each pass is greater than or equal to 5%.

5. The method for preparing the high-strength and ductile heterogeneous grain structure Al-Cu alloy according to claim 2, characterized in that: During the annealing process, the annealing temperature is 400-450°C and the holding time is 10-20h; In the solution process, the solution temperature is 510-540°C and the holding time is 0.5-2h; During the aging process, the aging temperature is 165-185° C. and the insulation time is 4-12 hours.

6. The method for preparing the high-strength and ductile heterogeneous grain structure Al-Cu alloy according to claim 2, characterized in that: The preparation process of the Al-Cu alloy ingot comprises: The raw materials of Cu, Mn, Sc, Ti and Al are mixed and heated to melt at 710-750°C. When the temperature is lowered to 680-700°C, the raw material of Mg is added and melted. The temperature is further raised to 710-750°C, and refined for 15-30 minutes. A slag-forming agent is added to obtain a molten liquid. The molten liquid is cooled to 700-720°C, and the molten liquid is poured into a mold to obtain an Al-Cu alloy ingot.

7. The method for preparing the high-strength and ductile heterogeneous grain structure Al-Cu alloy according to claim 2, characterized in that: The raw materials of each component are simple substances or intermediate alloys.

8. The method for preparing the high-strength and ductile heterogeneous grain structure Al-Cu alloy according to claim 2 or 7, characterized in that: The raw material of Cu is Al-50Cu master alloy, the raw material of Mn is Al-10Mn master alloy, the raw material of Sc is Al-2Sc master alloy, the raw material of Al is Al ingot, the raw material of Ti is Al-5Ti-B refiner, and the raw material of Mg is Mg ingot.

9. The method for preparing the high-strength and ductile heterogeneous grain structure Al-Cu alloy according to claim 2, characterized in that: The content of slag-forming agent is 0.15-0.3% of the total mass of raw materials.

10. The method for preparing the high-strength and ductile heterogeneous grain structure Al-Cu alloy according to claim 2, characterized in that: Before mixing the raw materials of Cu, Mn, Sc, Ti and Al, the raw materials of each component are cleaned and dried at a drying temperature of 150-200° C. and a drying time of 1-3 hours.

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