Annealing-solution-ageing heat treatment process of high-strength high-toughness corrosion-resistant Al-Zn-Mg-Cu alloy
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHANGZHOU UNIV
- Filing Date
- 2023-09-19
- Publication Date
- 2026-07-21
Smart Images
Figure FT_1 
Figure BDA0004456109670000061 
Figure BDA0004456109670000062
Abstract
Description
Technical Field
[0001] This invention relates to the field of aluminum alloy heat treatment technology, and in particular provides an annealing-solution-aging heat treatment process for a high-strength, high-toughness, and corrosion-resistant Al-Zn-Mg-Cu alloy. Background Technology
[0002] As the most widely used material in the aerospace field, Al-Zn-Mg-Cu aluminum alloys typically require solution treatment and aging to enhance their properties. A typical process is solution treatment followed by T6 aging heat treatment, which precipitates a uniformly dispersed strengthening phase, thereby increasing strength. However, the alloy exhibits poor corrosion resistance, being prone to intergranular corrosion (IGC) and stress corrosion cracking (SCC). The high density of precipitates, along with the fine GP zones and η′ phases within the grain boundaries of the continuous grain boundary precipitates, promotes continuous corrosion pathways along the grain boundary precipitates. The maximum depth of intergranular corrosion is approximately 300 μm, thus hindering their application in critical structural frames or aerospace and land transportation components. To address this, a typical two-stage T73 and T74 overaging process has been developed to improve the material's corrosion resistance. While T7-aged alloys offer good corrosion resistance, their strength typically decreases by 10%–15%. This is because the coarsening process during over-aging involves the precipitation and further growth of particles. The growth and coarsening of these precipitates reduce the strengthening effect, leading to a decrease in hardness. Simultaneously, these grain boundary precipitates become discontinuous, disrupting corrosion pathways and thus improving corrosion resistance. However, neither of these aging methods yields satisfactory results; strength and corrosion resistance are always antagonistic and cannot be simultaneously achieved.
[0003] To balance strength and corrosion resistance, the solution-regression reaging (RRA) process was developed. With the advent of RRA, the corrosion resistance of alloys is improved without loss of strength, allowing the alloy to simultaneously possess the mechanical properties of peak-aged alloys and the corrosion resistance of over-aged alloys. After RRA aging, the intragranular microstructure of the alloy is similar to that of peak-aged alloys, while the grain boundary microstructure is similar to that of over-aged alloys. The mixed precipitate configuration is key to achieving both excellent strength and corrosion resistance. Through the RRA process, the intergranular precipitates are discontinuously distributed, while the GP zone and η′ phase are dispersedly distributed, thus enabling the simultaneous acquisition of precipitates with good corrosion resistance and high strength. Summary of the Invention
[0004] To further improve the plasticity and corrosion resistance of Al-Zn-Mg-Cu aluminum alloy, the present invention aims to provide an annealing-solution-aging heat treatment process for a high-strength, high-toughness, and corrosion-resistant Al-Zn-Mg-Cu alloy.
[0005] The objective of this invention is achieved through the following technical solution:
[0006] An annealing-solution-aging heat treatment process for a high-strength, high-toughness, and corrosion-resistant Al-Zn-Mg-Cu alloy is disclosed, employing annealing treatment + single-stage solution treatment + re-aging treatment. The composition of the high-strength, high-toughness, and corrosion-resistant Al-Zn-Mg-Cu aluminum alloy, by mass percentage, is as follows: Zn 5.10–6.10%, Mg 2.10–2.90%, Cu 1.20–2.00%, Fe 0.00–0.50%, Mn 0.00–0.30%, Cr 0.18–0.28%, Si 0.00–0.40%, with total impurity elements ≤0.15%, and the balance being Al. The specific treatment process is as follows:
[0007] (1) The extruded or rolled Al-Zn-Mg-Cu aluminum alloy is annealed and then air-cooled to room temperature. 。
[0008] Furthermore, the annealing process includes single-stage annealing or two-stage annealing.
[0009] Furthermore, the single-stage annealing process involves placing the extruded or rolled Al-Zn-Mg-Cu aluminum alloy at 280-320℃ for 60-80 hours and then air-cooling it to room temperature.
[0010] Furthermore, the single-stage annealing process involves placing the extruded or rolled Al-Zn-Mg-Cu aluminum alloy at 300°C for 72 hours and then air-cooling it to room temperature.
[0011] Furthermore, the two-stage annealing process is as follows: the extruded or rolled Al-Zn-Mg-Cu aluminum alloy is held at 120-160℃ for 40-60 hours, then held at 280-320℃ for 0.5-2 hours, and then air-cooled to room temperature.
[0012] Furthermore, the two-stage annealing process is as follows: the extruded or rolled Al-Zn-Mg-Cu aluminum alloy is held at 140°C for 48 hours, then held at 300°C for 1 hour, and air-cooled to room temperature.
[0013] (2) The Al-Zn-Mg-Cu aluminum alloy after step (1) is subjected to single-stage solid solution treatment.
[0014] Furthermore, the single-stage solution treatment is as follows: after annealing, the Al-Zn-Mg-Cu aluminum alloy is held at 465-475℃ for 0.5-1.5h, and then water-quenched to room temperature, with a quenching transfer time of less than 5s.
[0015] (3) The Al-Zn-Mg-Cu aluminum alloy after step (2) is subjected to re-aging treatment.
[0016] Furthermore, the re-aging treatment is as follows: the solution-treated Al-Zn-Mg-Cu aluminum alloy is held at 110-130℃ for 20-30h, then held at 180-210℃ for 0.25-1h, and finally held at 110-130℃ for 20-30h, and then water-quenched to room temperature, with a quenching transfer time of less than 5s.
[0017] Advantages of this invention:
[0018] This invention employs a suitable temperature to perform single-stage or double-stage annealing on aluminum alloy plates to eliminate residual stress and induce recrystallization. This, combined with a solution-regression-aging heat treatment process, improves the plasticity and corrosion resistance of the aluminum alloy while also meeting the comprehensive performance requirements of high strength and high toughness.
[0019] After annealing-solution-aging heat treatment, the precipitates in the aluminum alloy sheet are more uniformly and finely distributed. The grain boundary precipitates change from a continuous chain distribution to a discontinuous distribution. While maintaining or slightly improving tensile strength and elongation at break, the average corrosion depth can reach as low as 46.2 μm. Attached image description:
[0020] Figure 1 The figures show the maximum corrosion depth of intergranular corrosion experiments in Examples 1-2 and Comparative Examples 1-4 of the present invention, where Figure (ab) represents Examples 1-2 and Figure (cf) represents Comparative Examples 1-4. Detailed Implementation
[0021] The present invention will be further described below with reference to embodiments and comparative examples.
[0022] The examples and comparative examples used Al-Zn-Mg-Cu aluminum alloy cold-rolled sheet, whose composition by mass percentage ranges as follows: Zn 5.10-6.10%, Mg 2.10-2.90%, Cu 1.20-2.00%, Fe 0.00-0.50%, Mn 0.00-0.30%, Cr 0.18-0.28%, Si 0.00-0.40%, with a total impurity element content ≤0.15%, and the balance being Al.
[0023] Example 1
[0024] Al-Zn-Mg-Cu aluminum alloy cold-rolled sheets were subjected to single-stage annealing, i.e., furnace heating to 300℃ and holding for 72 hours, followed by air cooling to room temperature; then single-stage solution treatment, i.e., heating to 470℃ and holding for 1 hour, followed by water quenching to room temperature with a quenching transfer time of less than 5 seconds; finally, regression aging treatment, i.e., heating to 120℃ and holding for 24 hours, then heating to 200℃ and holding for 45 minutes, and finally cooling to 120℃ and holding for 24 hours, followed by water quenching to room temperature with a quenching transfer time of less than 5 seconds, to obtain a high-strength, high-toughness, and corrosion-resistant Al-Zn-Mg-Cu aluminum alloy.
[0025] Example 2
[0026] The Al-Zn-Mg-Cu aluminum alloy cold-rolled sheet was first subjected to a two-stage annealing treatment, namely, heating in the furnace to 140℃ and holding for 48 hours, then raising the temperature to 300℃ and holding for 1 hour, followed by air cooling to room temperature; then a single-stage solution treatment was performed, namely heating to 470℃ and holding for 1 hour, after which the sample was water-quenched to room temperature with a quenching transfer time of less than 5 seconds; finally, a regression aging treatment was performed, namely heating to 120℃ and holding for 24 hours, then raising the temperature to 200℃ and holding for 45 minutes, and finally cooling to 120℃ and holding for 24 hours, after which the sample was water-quenched to room temperature with a quenching transfer time of less than 5 seconds, to obtain a high-strength, high-toughness, and corrosion-resistant Al-Zn-Mg-Cu aluminum alloy.
[0027] Comparative Example 1
[0028] Al-Zn-Mg-Cu aluminum alloy cold-rolled sheet was subjected to single-stage solution treatment, i.e., heated to 470℃ and held for 1 hour, and then water-quenched to room temperature with a quenching transfer time of less than 5 seconds; finally, aging treatment was performed, i.e., heated to 120℃ and held for 24 hours (T6), and then water-quenched to room temperature with a quenching transfer time of less than 5 seconds, to obtain a high-strength, high-toughness and corrosion-resistant Al-Zn-Mg-Cu aluminum alloy.
[0029] Comparative Example 2
[0030] Al-Zn-Mg-Cu aluminum alloy cold-rolled sheet was subjected to single-stage solution treatment, i.e., heated to 470℃ and held for 1 hour, and then water-quenched to room temperature with a quenching transfer time of less than 5 seconds. Finally, a regression aging treatment was performed, i.e., heated to 120℃ and held for 24 hours, then heated to 200℃ and held for 45 minutes, and finally cooled to 120℃ and held for 24 hours. After aging, the sample was water-quenched to room temperature with a quenching transfer time of less than 5 seconds, resulting in a high-strength, high-toughness, and corrosion-resistant Al-Zn-Mg-Cu aluminum alloy.
[0031] Comparative Example 3
[0032] The Al-Zn-Mg-Cu aluminum alloy cold-rolled sheet was first subjected to a single-stage annealing treatment, i.e., furnace heating to 450℃ and holding for 72 hours, followed by air cooling to room temperature; then a single-stage solution treatment was performed, i.e., heating to 470℃ and holding for 1 hour, followed by water quenching to room temperature with a quenching transfer time of less than 5 seconds; finally, a re-aging treatment was performed, i.e., heating to 120℃ and holding for 24 hours, then raising the temperature to 200℃ and holding for 45 minutes, and finally cooling to 120℃ and holding for 24 hours, followed by water quenching to room temperature with a quenching transfer time of less than 5 seconds, to obtain a high-strength, high-toughness, and corrosion-resistant Al-Zn-Mg-Cu aluminum alloy.
[0033] Comparative Example 4
[0034] The Al-Zn-Mg-Cu aluminum alloy cold-rolled sheet was first subjected to a two-stage annealing treatment: the sample was heated in a furnace to 140℃ and held for 48 hours, then heated to 450℃ and held for 1 hour, followed by air cooling to room temperature. Then, a single-stage solution treatment was performed: the sample was heated to 470℃ and held for 1 hour, and then water-quenched to room temperature with a quenching transfer time of less than 5 seconds. Finally, a re-aging treatment was performed: the sample was heated to 120℃ and held for 24 hours, then heated to 200℃ and held for 45 minutes, and finally cooled to 120℃ and held for 24 hours, and then water-quenched to room temperature with a quenching transfer time of less than 5 seconds, resulting in a high-strength, high-toughness, and corrosion-resistant Al-Zn-Mg-Cu aluminum alloy.
[0035] The Al-Zn-Mg-Cu aluminum alloys prepared in the examples and comparative examples were tested according to the methods of tensile testing of metallic materials in GB / T 228.1-2010 and intergranular corrosion test of aluminum alloys in GB / T 7998-2005. Each sample was tested three times to ensure the accuracy of the experimental data. The tensile strength and elongation at break of the Al-Zn-Mg-Cu aluminum alloys in the examples and comparative examples are shown in Table 1, and the test results of intergranular corrosion test are shown in Table 2.
[0036] Table 1. Room temperature mechanical property test results of the embodiments and comparative examples of the present invention.
[0037]
[0038] Table 2. Experimental results of intergranular corrosion in the embodiments and comparative examples of the present invention.
[0039]
[0040] A comparison of the mechanical and corrosion performance test results of Examples 1-2 and Comparative Examples 1-4 shows that the embodiments of the present invention can significantly improve the mechanical properties and corrosion resistance of the alloys compared with the comparative examples. Example 2 is a preferred embodiment of the present invention.
[0041] The above embodiments and comparative examples are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. For those skilled in the art, any improvements and substitutions made based on the technical solutions of the present invention without creative effort shall fall within the protection scope of the present invention.
Claims
1. An annealing-solution-aging heat treatment process for a high-strength, high-toughness, and corrosion-resistant Al-Zn-Mg-Cu alloy, characterized in that: The specific processing technology is as follows: the extruded or rolled Al-Zn-Mg-Cu aluminum alloy is subjected to annealing, single-stage solution treatment, and re-aging treatment in sequence to obtain a high-strength, high-toughness, and corrosion-resistant Al-Zn-Mg-Cu aluminum alloy; the annealing process is a two-stage annealing treatment; the two-stage annealing treatment is as follows: the extruded or rolled Al-Zn-Mg-Cu aluminum alloy is held at 140℃ for 48h, then held at 300℃ for 1h, and then air-cooled to room temperature; The regression re-aging treatment is as follows: the solution-treated Al-Zn-Mg-Cu aluminum alloy is placed at 120℃ for 24 hours, then at 200℃ for 45 minutes, and finally at 120℃ for 24 hours, and then water-cooled to room temperature, with a quenching transfer time of less than 5 seconds. The composition of the high-strength, high-toughness, and corrosion-resistant Al-Zn-Mg-Cu aluminum alloy, by mass percentage, is as follows: Zn 5.10~6.10%, Mg 2.10~2.90%, Cu 1.20~2.00%, Fe 0.00~0.50%, Mn 0.00~0.30%, Cr 0.18~0.28%, Si 0.00~0.40%, total impurity elements ≤0.15%, and the balance being Al; The single-stage solution treatment is as follows: after annealing, the Al-Zn-Mg-Cu aluminum alloy is kept at 465-475℃ for 0.5-1.5h, and then water-quenched to room temperature, with a quenching transfer time of less than 5s.