A method for improving the heat resistance of a thin sheet of an Al-Cu-Mn-Si alloy
By employing a process of water-cooled copper mold rapid casting followed by specific annealing and rolling treatments, the contradiction between dispersed and precipitated phases in aluminum alloys was resolved, resulting in alloy thin plates with excellent heat resistance and plasticity.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CHANGZHOU UNIV
- Filing Date
- 2026-03-30
- Publication Date
- 2026-06-19
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of aluminum alloy processing technology, and in particular provides a method for preparing thin plates that improve the heat resistance of Al-Cu-Mn-Si alloys. Background Technology
[0002] Al-Cu-Mn-Si alloys, with α-AlMnSi dispersed phases and Al2Cu precipitates as the main strengthening phases, belong to a novel low-cost heat-resistant aluminum alloy. The α-AlMnSi dispersed phase originates from the precipitation of supersaturated Mn and Si solute atoms in the non-equilibrium solidified ingot alloy during homogenization annealing, while the Al2Cu precipitate is formed by the precipitation of supersaturated Cu solute atoms during solution treatment and quenching, followed by aging. To maximize the strengthening effect of the age-precipitated Al2Cu phase, the ingot alloy typically requires high-temperature, long-term homogenization annealing to fully dissolve the coarse-sized non-equilibrium Al2Cu crystals. This lays the foundation for obtaining a high concentration of supersaturated Cu solute atoms through solution treatment and quenching, ultimately leading to the age-precipitated Al2Cu phase.
[0003] To facilitate aluminum alloy profile processing, Al-Cu-Mn-Si alloys must possess good plastic deformation capabilities. Typically, homogenization annealing can eliminate coarse Al2Cu crystalline phases, thereby improving the alloy's plastic deformation capabilities and benefiting profile processing. However, high-temperature, long-duration homogenization annealing can lead to coarsening and a reduction in the number of α-AlMnSi dispersed phase particles, which is detrimental to improving the heat resistance of Al-Cu-Mn-Si alloys. Therefore, conventional high-temperature, long-duration homogenization annealing treatment cannot resolve the contradiction between the small size and large quantity of α-AlMnSi dispersed phases and good plastic deformation capabilities. Summary of the Invention
[0004] In order to obtain both small-sized and abundant α-AlMnSi dispersed phases and Al2Cu precipitates to improve the heat resistance of the alloy, and good plastic deformation ability to meet the requirements of alloy thin plate forming, this invention provides a thin plate preparation process for improving the heat resistance of Al-Cu-Mn-Si alloy. The process mainly includes melting the alloy and then sequentially performing water-cooled copper mold rapid casting to form an ingot, low-temperature annealing, hot rolling deformation, intermediate annealing, cold rolling deformation, solution treatment, and slight over-aging.
[0005] Further, the alloy is composed of the following components by mass percentage: Cu: 4.8-5.1, Mn: 1.2-1.5, Si: 0.9.0-1.2, Zr: 0.1-0.25, Fe: ≤0.5, with the balance being Al. A small amount of Zr is added to refine the grain structure of the as-cast alloy.
[0006] Furthermore, the low-temperature annealing is: placing the ingot obtained by rapid cooling casting of water-cooled copper mold at 200-250 ℃ for 12-24 h.
[0007] Furthermore, the hot rolling deformation is as follows: the ingot obtained by low-temperature annealing is heated to 350-400 ℃, and hot rolled to a certain thickness through multiple passes. Subsequently, the hot-rolled plate is air-cooled to room temperature; the total thickness reduction rate of hot rolling is not less than 30%.
[0008] Furthermore, the intermediate annealing is performed by placing the hot-rolled and deformed sheet at 350-400 ℃ for 2-4 hours.
[0009] Furthermore, the total cold-rolled thickness reduction rate of the cold-rolled deformation is not less than 70%.
[0010] Furthermore, the solution treatment is performed by holding at 520-540 ℃ for 0.5-1 h, followed by immediate water quenching.
[0011] Furthermore, the slight over-aging process is defined as: maintaining a temperature of 200-220 ℃ for 6-12 hours.
[0012] Aluminum alloys are smelted using conventional processes and cast into ingots using water-cooled copper molds. Due to the rapid solidification rate of the melt under water-cooled copper mold casting conditions, the concentration of supersaturated Mn, Si, and Cu solutes in the ingot increases, while the concentration of non-equilibrium crystalline phases α-AlMnSi and Al2Cu decreases. The ingot alloy undergoes prolonged low-temperature annealing at a relatively low temperature, resulting in the precipitation of small-sized and abundant α-AlMnSi dispersed phases from supersaturated Mn and Si atoms, while coarse Al2Cu phases precipitate from supersaturated Cu atoms. When the low-temperature annealed ingot is heated to a higher temperature, the thermally stable α-AlMnSi dispersed phases remain in a fine-particle state, while the Al2Cu precipitates further coarsen. Under these conditions, even if the ingot still contains a significant amount of crystalline phases, it can achieve high hot-deformation capacity, thus ensuring that the alloy can be hot-rolled to a certain thickness in multiple passes with a relatively small total thickness reduction.
[0013] Reheating and holding the hot-rolled sheet for intermediate annealing eliminates residual work hardening and further promotes the coarsening of the Al2Cu precipitates. This results in a high degree of cold deformation capability, allowing for large deformation and multi-pass cold rolling to the required sheet thickness at room temperature. It also effectively breaks down coarse crystalline phases and grain structures, and introduces numerous dislocations, grain boundaries, and other crystal defects. In this case, solution treatment of the cold-rolled sheet ensures complete dissolution of the Al2Cu phase within a short heating time, forming a high-temperature solid solution, while mitigating the coarsening of the α-AlMnSi dispersed phase and maintaining fine dimensional characteristics. Immediate water quenching after solution treatment yields a supersaturated solid solution, followed by slight over-aging to improve the thermal stability of the Al2Cu precipitates. This synergistic effect with the α-AlMnSi dispersed phase enhances the alloy's heat resistance.
[0014] The beneficial effects of this invention are:
[0015] This invention proposes a thin plate preparation process to improve the heat resistance of Al-Cu-Mn-Si alloy. Its advantage is that the ingot does not require homogenization annealing treatment, and can simultaneously form small-sized and numerous α-AlMnSi dispersed phases and Al2Cu precipitates while ensuring hot rolling and cold rolling of the plate, thereby preparing alloy thin plates with significantly improved heat resistance. Attached Figure Description
[0016] Figure 1 The microstructure characteristics of the as-cast alloy in Example 1;
[0017] Figure 2 The cold-rolled alloy sheet sample from Example 1;
[0018] Figure 3 The microstructure of the solution-treated alloy in Example 1;
[0019] Figure 4 The microstructure characteristics of the heat-exposed alloy in Example 1;
[0020] Figure 5 The microstructure of the solution-treated alloy in Comparative Example 1 is shown.
[0021] Figure 6 The microstructure of the as-cast alloy poured from a preheated iron mold at 200℃ in Comparative Example 2 is shown.
[0022] Figure 7 The microstructure characteristics of the solution-treated alloy in Comparative Example 3 are shown.
[0023] Figure 8 Microstructural characteristics of the heat-exposed alloy in Comparative Example 4;
[0024] Figure 9 The microstructure characteristics of the heat-exposed alloy in Comparative Example 5 are shown. Detailed Implementation
[0025] Example 1
[0026] The alloy was smelted using conventional processes (melting temperature 750-770 ℃, followed by refining and degassing at 710-730 ℃, and a settling time of 20-40 min) and cast into ingots using water-cooled copper molds. The chemical composition was Cu: 5.06, Mn: 1.47, Si: 1.15, Zr: 0.18, Fe: 0.12. The as-cast alloy exhibited a relatively uniform distribution of crystalline phases, dominated by Al2Cu phase, with a small amount of α-AlMnSi crystalline phase resembling Chinese characters (…). Figure 1 (As indicated by the middle arrow). After low-temperature annealing at 220 ℃ / 24 h, the ingot is heated in the furnace to 400 ℃ and hot-rolled in multiple passes to a thickness of 6.5 mm (total thickness reduction rate of 35%). Subsequently, the hot-rolled sheet undergoes intermediate annealing at 350 ℃ / 2 h, air-cools to room temperature, and then cold-rolls in multiple passes using a twin-roll mill to a thickness of 2 mm (total thickness reduction rate of approximately 70%). Figure 2 As shown; after solution treatment at 540 ℃ / 1 h and water quenching, the cold-rolled sheet contains a large number of spherical or short rod-shaped α-AlMnSi dispersed phases with a size of approximately 50-200 nm. Figure 3 After the quenched alloy underwent slight over-aging treatment at 200 ℃ / 10 h, it was then subjected to heat exposure at 300 ℃ / 120 h. In addition to the α-AlMnSi dispersed phase, a relatively large number of needle-like Al2Cu precipitates were also distributed in the alloy. Figure 4 Tensile tests showed that the heat-exposed alloy had a tensile strength of 305 MPa, a yield strength of 192 MPa, and an elongation of 11.1% (Table 1).
[0027] Comparative Example 1
[0028] The alloy was smelted using conventional processes and cast into ingots using water-cooled copper molds. The chemical composition was Cu: 5.06, Mn: 1.47, Si: 1.15, Zr: 0.18, Fe: 0.12. After homogenization annealing at 500 ℃ for 24 h, the ingots were cooled to 400 ℃ in the furnace and then hot-rolled multiple times to a thickness of 6.5 mm (total thickness reduction rate of 35%). The hot-rolled sheet was then intermediate annealed at 350 ℃ for 2 h, air-cooled to room temperature, and then cold-rolled multiple times using a twin-roll mill to a thickness of 2 mm (total thickness reduction rate of approximately 70%). The cold-rolled sheet was solution-treated at 540 ℃ for 1 h and then water-quenched. It was then subjected to a slight over-aging treatment at 200 ℃ for 10 h, followed by heat exposure at 300 ℃ for 120 h. Tensile tests showed that the heat-exposed alloy had a tensile strength of 274 MPa, a yield strength of 165 MPa, and an elongation of 12.8% (Table 1).
[0029] As shown in Table 1, the strength of the alloy in Comparative Example 1 is lower than that of the alloy in Example 1. This is because the high-temperature, long-term homogenization annealing treatment resulted in a larger size and a reduced quantity of the α-AlMnSi dispersed phase. Figure 5 This leads to a decrease in dispersion strengthening effect, and consequently a reduction in alloy strength.
[0030] Comparative Example 2
[0031] The alloy was smelted using conventional processes and cast into ingots using a preheated iron mold at 200℃. The chemical composition was Cu: 5.06, Mn: 1.47, Si: 1.15, Zr: 0.18, Fe: 0.12. After pre-annealing at 220℃ for 24 h, the ingots were heated in the furnace to 400℃ and then hot-rolled multiple times to a thickness of 6.5 mm (total thickness reduction of 35%). The hot-rolled sheet was then intermediate-annealed at 350℃ for 2 h, air-cooled to room temperature, and cold-rolled multiple times using a twin-roll mill to a thickness of 2 mm (total thickness reduction of approximately 70%). The cold-rolled sheet was solution-treated at 540℃ for 1 h and water-quenched, then subjected to a slight over-aging treatment at 200℃ for 10 h, followed by heat exposure at 300℃ for 120 h. Tensile tests showed that the heat-exposed alloy had a tensile strength of 266 MPa, a yield strength of 153 MPa, and an elongation of 12.5% (Table 1).
[0032] As shown in Table 1, the strength of alloy in Comparative Example 2 is lower than that of alloy in Example 1. This is because the solidification rate of the preheated iron mold casting decreases, resulting in a higher concentration of α-AlMnSi crystalline phase in the ingot alloy. Figure 6 The concentrations of supersaturated Mn and Si solutes will inevitably decrease, thereby reducing the amount of α-AlMnSi dispersed phase and consequently reducing the alloy strength.
[0033] Comparative Example 3
[0034] The alloy was smelted using conventional processes and cast into ingots using water-cooled copper molds. The chemical composition was Cu: 5.06, Mn: 1.47, Si: 1.15, Zr: 0.18, Fe: 0.12. After pre-annealing at 220 ℃ for 24 h, the ingots were furnace-heated to 400 ℃ and hot-rolled multiple times to a thickness of 6.5 mm (total thickness reduction of 35%). The hot-rolled sheet underwent intermediate annealing at 400 ℃ for 2 h, followed by air cooling to room temperature and cold rolling multiple times using a twin-roll mill to a thickness of 2 mm (total thickness reduction of approximately 70%). The cold-rolled sheet underwent solution treatment at 540 ℃ for 4 h and water quenching, followed by a slight over-aging treatment at 200 ℃ for 10 h, and then heat exposure at 300 ℃ for 120 h. Tensile tests showed that the heat-exposed alloy had a tensile strength of 291 MPa, a yield strength of 175 MPa, and an elongation of 12.9% (Table 1).
[0035] As shown in Table 1, the strength of alloy in Comparative Example 3 is lower than that of alloy in Example 1. This is because the solution treatment time is too long, which further coarsens the α-AlMnSi dispersed phase and reduces its quantity. Figure 7 This leads to a decrease in the strengthening effect of the α-AlMnSi dispersed phase, and consequently a decrease in the alloy strength.
[0036] Comparative Example 4
[0037] The alloy was smelted using conventional processes and cast into ingots using water-cooled copper molds. The chemical composition was Cu: 5.06, Mn: 1.47, Si: 1.15, Zr: 0.18, Fe: 0.12. After pre-annealing at 220 ℃ for 24 h, the ingots were furnace-heated to 400 ℃ and hot-rolled multiple times to a thickness of 6.5 mm (total thickness reduction of 35%). The hot-rolled sheet was reheated to 400 ℃, held for 2 h, and then intermediate-annealed. After air-cooling to room temperature, it was cold-rolled multiple times using a twin-roll mill to a thickness of 2 mm (total thickness reduction of approximately 70%). The cold-rolled sheet underwent solution treatment at 510 ℃ for 1 h and water quenching, followed by a slight over-aging treatment at 200 ℃ for 10 h, and then heat exposure at 300 ℃ for 120 h. Tensile tests showed that the heat-exposed alloy had a tensile strength of 258 MPa, a yield strength of 162 MPa, and an elongation of 9.4% (Table 1).
[0038] As shown in Table 1, the strength of the alloy in Comparative Example 4 is lower than that of the alloy in Example 1. This is because the solution treatment temperature is too low, resulting in insufficient dissolution of the Cu-containing soluble phase, which ultimately leads to a reduction in the Al2Cu phase precipitated during aging.
[0039] Comparative Example 5
[0040] The alloy was smelted using conventional processes and cast into ingots using water-cooled copper molds. The chemical composition was Cu: 5.06, Mn: 1.47, Si: 1.15, Zr: 0.18, Fe: 0.12. After pre-annealing at 220 ℃ for 24 h, the ingots were furnace-heated to 400 ℃ and hot-rolled multiple times to a thickness of 6.5 mm (total thickness reduction of 35%). The hot-rolled sheet was then reheated to 350 ℃, held for 2 h, and intermediate-annealed. After air-cooling to room temperature, it was cold-rolled multiple times using a twin-roll mill to a thickness of 2 mm (total thickness reduction of approximately 70%). The cold-rolled sheet underwent solution treatment at 540 ℃ for 1 h and water quenching, followed by peak aging treatment at 200 ℃ for 2 h, and then heat exposure at 300 ℃ for 120 h. Tensile tests showed that the heat-exposed tensile strength was 287 MPa, the yield strength was 167 MPa, and the elongation was 12.1% (Table 1).
[0041] As shown in Table 1, the strength of the alloy in Comparative Example 5 is lower than that of the alloy in Example 1. This is because the Al2Cu phase precipitated during peak aging is smaller in size and has lower thermal stability. Its size differs greatly from that of the adjacent coarse α-AlMnSi dispersed phase, and it is easy to coarsen and reduce in number during thermal exposure, thereby reducing the strength of the alloy.
[0042] Example 2
[0043] The alloy was smelted using conventional processes and cast into ingots using water-cooled copper molds. The chemical composition was Cu: 4.82, Mn: 1.23, Si: 0.95, Zr: 0.11, Fe: 0.36. After low-temperature annealing at 200 ℃ / 12 h, the ingots were furnace-heated to 350 ℃ and hot-rolled multiple times to a thickness of 7 mm (total thickness reduction of 30%). The hot-rolled sheet was then intermediate-annealed at 400 ℃ / 2 h, air-cooled to room temperature, and cold-rolled multiple times using a twin-roll mill to a thickness of 2 mm (total thickness reduction of approximately 71%). The cold-rolled sheet underwent solution treatment at 540 ℃ / 0.5 h and water quenching, followed by a slight over-aging treatment at 220 ℃ / 12 h, and then heat exposure at 300 ℃ / 120 h. Tensile tests showed that the heat-exposed alloy had a tensile strength of 297 MPa, a yield strength of 184 MPa, and an elongation of 12.3% (Table 1).
[0044] Example 3
[0045] The alloy composition was Cu: 4.98, Mn: 1.37, Si: 1.08, Zr: 0.21, Fe: 0.21, using conventional smelting processes and water-cooled copper mold casting. After pre-annealing at 200 ℃ for 24 h, the ingots were furnace-heated to 370 ℃ and hot-rolled multiple times to a thickness of 5.0 mm (total thickness reduction of 50%). The hot-rolled sheet underwent intermediate annealing at 380 ℃ for 1 h, followed by air cooling to room temperature, and then cold-rolled multiple times using a twin-roll mill to a thickness of 1.5 mm (total thickness reduction of approximately 70%). The cold-rolled sheet underwent solution treatment at 530 ℃ for 0.5 h and water quenching, followed by slight over-aging treatment at 210 ℃ for 6 h, and then heat exposure at 300 ℃ for 120 h. Tensile tests showed that the heat-exposed alloy had a tensile strength of 299 MPa, a yield strength of 195 MPa, and an elongation of 10.7% (Table 1).
[0046] Example 4
[0047] The alloy was smelted using conventional processes and cast into ingots using water-cooled copper molds. The chemical composition was Cu: 5.08, Mn: 1.41, Si: 1.13, Zr: 0.24, Fe: 0.12. After pre-annealing at 250 ℃ for 12 h, the ingots were furnace-heated to 390 ℃ and hot-rolled multiple times to a thickness of 4.5 mm (total thickness reduction of 55%). The hot-rolled sheet underwent intermediate annealing at 350 ℃ for 1 h, followed by air cooling to room temperature and cold rolling multiple times using a twin-roll mill to a thickness of 1 mm (total thickness reduction of approximately 78%). The cold-rolled sheet underwent solution treatment at 520 ℃ for 1 h and water quenching, followed by a slight over-aging treatment at 200 ℃ for 8 h, and then heat exposure at 300 ℃ for 120 h. Tensile tests showed that the heat-exposed alloy had a tensile strength of 312 MPa, a yield strength of 198 MPa, and an elongation of 10.6% (Table 1).
[0048] Example 5
[0049] The alloy was smelted using conventional processes and cast into ingots using water-cooled copper molds. The chemical composition was Cu: 4.88, Mn: 1.36, Si: 1.14, Zr: 0.18, Fe: 0.18. After pre-annealing at 230 ℃ for 12 h, the ingots were furnace-heated to 350 ℃ and hot-rolled multiple times to a thickness of 6.5 mm (total thickness reduction of 35%). The hot-rolled sheet underwent intermediate annealing at 400 ℃ for 2 h, followed by air cooling to room temperature and cold rolling multiple times using a twin-roll mill to a thickness of 2 mm (total thickness reduction of approximately 70%). The cold-rolled sheet underwent solution treatment at 520 ℃ for 0.5 h and water quenching, followed by a slight over-aging treatment at 200 ℃ for 10 h, and then heat exposure at 300 ℃ for 120 h. Tensile tests showed that the heat-exposed alloy had a tensile strength of 304 MPa, a yield strength of 187 MPa, and an elongation of 12.7% (Table 1).
[0050] Table 1 Tensile properties of alloys exposed to heat at 300 ℃ / 120 h
[0051]
[0052] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.
Claims
1. A process for preparing thin plates to improve the heat resistance of Al-Cu-Mn-Si alloys, characterized in that, After the alloy is melted, it is sequentially subjected to water-cooled copper mold rapid casting to form ingots, low-temperature annealing, hot rolling deformation, intermediate annealing, cold rolling deformation, solution treatment, and slight over-aging.
2. The thin plate preparation process for improving the heat resistance of Al-Cu-Mn-Si alloy according to claim 1, characterized in that, The alloy consists of the following components by mass percentage: Composition: Cu: 4.8-5.1, Mn: 1.2-1.5, Si: 0.9-1.2, Zr: 0.1-0.25, Fe: ≤0.5, balance Al.
3. The thin plate preparation process for improving the heat resistance of Al-Cu-Mn-Si alloy according to claim 1, characterized in that, The low-temperature annealing process involves placing the ingot obtained from rapid cooling casting using a water-cooled copper mold at 200-250℃ for 12-24 hours.
4. The thin plate preparation process for improving the heat resistance of Al-Cu-Mn-Si alloy according to claim 1, characterized in that, The hot rolling deformation is as follows: the ingot obtained by low-temperature annealing is heated to 350-400 ℃, and hot rolled to a certain thickness through multiple passes. Subsequently, the hot-rolled plate is air-cooled to room temperature; the total thickness reduction rate of hot rolling is not less than 30%.
5. The thin plate preparation process for improving the heat resistance of Al-Cu-Mn-Si alloy according to claim 1, characterized in that, The intermediate annealing process involves placing the hot-rolled and deformed sheet at 350-400 ℃ for 2-4 hours.
6. The thin plate preparation process for improving the heat resistance of Al-Cu-Mn-Si alloy according to claim 1, characterized in that, The solution treatment is performed by holding the solution at 520-540 ℃ for 0.5-1 h, followed by immediate water quenching.
7. The thin plate preparation process for improving the heat resistance of Al-Cu-Mn-Si alloy according to claim 1, characterized in that, The term "slight over-aging" refers to holding the product at 200-220 ℃ for 6-12 hours.