5-series aluminum alloy and strengthening method thereof
By using room temperature cyclic plastic deformation treatment and low-cycle fatigue loading, Mg solute clusters are formed, which solves the problems of insufficient strength and corrosion resistance of 5-series aluminum alloys, and achieves a synergistic improvement in strength and corrosion resistance, making it suitable for rail transportation, shipbuilding and marine engineering.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CHONGQING UNIV
- Filing Date
- 2026-04-15
- Publication Date
- 2026-05-12
AI Technical Summary
While maintaining excellent corrosion resistance, existing 5-series aluminum alloys have difficulty simultaneously improving strength and achieving synergistic optimization of mechanical properties and corrosion resistance. Traditional strengthening methods suffer from high costs, reduced plasticity, and the creation of corrosion initiation sites.
The process employs room temperature cyclic plastic deformation treatment, which introduces high-density supersaturated vacancies into the matrix to form Mg solute clusters, consuming free Mg atoms in the matrix and suppressing the precipitation of continuous network β phase at grain boundaries. This is combined with low-cycle fatigue loading for strengthening.
It significantly improves the resistance of 5-series aluminum alloys to intergranular corrosion and stress corrosion cracking, reduces energy consumption and process costs, avoids the negative effects of multi-element alloying and severe plastic deformation, and achieves a synergistic improvement in strength and corrosion resistance.
Smart Images
Figure CN122013003A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of aluminum alloy technology, specifically to a 5-series aluminum alloy and its strengthening method. Background Technology
[0002] In fields such as rail transportation, shipbuilding, and marine engineering, 5-series aluminum alloys are widely used due to their excellent specific strength, good corrosion resistance, and outstanding processing performance. The strengthening of these alloys mainly relies on solid solution strengthening, which involves dissolving Mg atoms into the aluminum matrix. However, this strengthening method presents a significant performance balance challenge: when the Mg content is higher than 3.5 wt.%, although 5-series aluminum alloys can achieve high strength, during long-term service at medium temperatures (50~200℃), a continuous network of β phase (Al3Mg2) easily forms at the grain boundaries, leading to solute depletion near the grain boundaries and inducing severe intergranular corrosion and stress corrosion cracking susceptibility, posing a serious threat to service safety under complex operating conditions. Conversely, if the Mg content is reduced to below 3.5 wt.%, although sensitization behavior can be effectively suppressed and excellent intergranular corrosion resistance can be obtained, the solid solution strengthening effect will be significantly weakened, resulting in insufficient material strength, making it difficult to meet the high strength requirements of lightweight structural components.
[0003] To address these challenges, existing research primarily follows two technical paths. The first is the microalloying route (e.g., adding Zn, Cu, Sc, Zr, etc.), aiming to provide additional strengthening by forming precipitated or dispersed phases and suppressing grain boundary precipitation. However, this method typically introduces complex alloy composition design, significantly increasing material costs, and multi-element alloying hinders alloy recycling, negatively impacting economic and environmental sustainability throughout its lifecycle. The second is drastic plastic deformation techniques, such as equal-channel angle extrusion and cumulative rolling, attempting to improve strength through grain refinement and the introduction of high-density dislocations. However, these methods often lead to a significant decrease in plasticity, and the refined grain boundaries and high-density dislocations may become new sites for corrosion initiation, making it difficult to simultaneously improve strength and corrosion resistance. More importantly, neither of these strategies fundamentally solves the problem of Mg atom segregation along grain boundaries, nor can they prevent the rapid formation of a continuous network β phase during subsequent sensitization. Therefore, they have consistently failed to overcome the bottleneck between corrosion resistance and mechanical properties in 5-series aluminum alloys.
[0004] In conclusion, how to further improve the strength of 5-series aluminum alloys while maintaining their excellent corrosion resistance, and achieve synergistic optimization of mechanical properties and corrosion resistance, has become a key technical challenge that urgently needs to be solved. Summary of the Invention
[0005] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a 5-series aluminum alloy and its strengthening method, so as to solve the problem that the 5-series aluminum alloy cannot well balance mechanical properties and corrosion resistance in the existing technology.
[0006] To achieve the above objectives, the present invention adopts the following technical solution:
[0007] A 5-series aluminum alloy, by mass fraction, comprises: 2.4-8.6% Mg, with the balance being Al and unavoidable impurities.
[0008] This invention also provides a method for strengthening 5-series aluminum alloys, comprising the following steps:
[0009] S1. The 5-series aluminum alloy is processed to obtain an alloy sample;
[0010] S2. After solution treatment, the alloy sample obtained in S1 is quenched at room temperature;
[0011] S3. After cyclic plasticizing treatment of the alloy sample quenched in S2, a strengthened 5-series aluminum alloy is obtained.
[0012] Preferably, in step S1, the alloy sample includes two coaxially arranged clamping sections and a gauge length section. The gauge length section is fixedly connected between the two clamping sections. The diameter of the gauge length section is 6.0±0.1mm, and the length of the gauge length section is 15±0.1mm. The diameter of each clamping section is 12.0±0.1mm, and the length of each clamping section is 40±0.5mm. The gauge length section is connected to the two clamping sections by an arc surface with a radius of 30.0±0.5mm.
[0013] Preferably, in step S2, before the solution treatment, the surface of the alloy sample needs to be covered with a layer of carbon powder 8-10 mm thick.
[0014] Preferably, in step S2, the solution temperature is 440~460℃, and the solution is kept at that temperature for 3 hours.
[0015] Preferably, in step S2, the quenching method is water quenching, and the quenching transfer time is less than 30s.
[0016] Preferably, in step S3, the specific method of cyclic plastic treatment is as follows: the alloy sample that has been quenched in S2 is placed in a fatigue test system, and under a sinusoidal waveform, a horizontal stress is applied to the alloy sample to perform multiple cycles of symmetrical tensile-compression treatment.
[0017] Preferably, the frequency of the sine wave is 0.15~0.2Hz.
[0018] Preferably, the horizontal stress applied to the alloy sample must satisfy:
[0019]
[0020] Among them, σ0 and σ max These represent the yield strength and tensile strength of the quenched alloy, respectively; N total and N i These represent the total number of cycles during the stretch-compression process and the number of cycles for the i-th cycle, respectively.
[0021] Preferably, the number of cycles is 500 to 800.
[0022] Compared with the prior art, the present invention has the following beneficial effects:
[0023] 1. This invention introduces high-density supersaturated vacancies into the matrix of a non-heat-treated strengthened Al-Mg alloy through room-temperature cyclic plastic deformation treatment, overcoming the kinetic barrier of solute atom diffusion at room temperature, thereby forming high-density, uniformly sized Mg solute clusters. These clusters produce a significant strengthening effect, solving the problem of insufficient strength in traditional 5-series aluminum alloys due to the lack of precipitation strengthening mechanisms. Simultaneously, the formation of these clusters effectively consumes free Mg atoms in the matrix, inhibiting the precipitation of continuous network β phase (Al3Mg2) at grain boundaries during service, thus significantly improving the resistance to intergranular corrosion and stress corrosion cracking of 5-series aluminum alloys, breaking through the long-standing technical bottleneck of balancing mechanical properties and corrosion resistance in 5-series aluminum alloys.
[0024] 2. The key strengthening steps of this invention can be completed at room temperature, eliminating the need for high-temperature heating equipment and complex temperature control systems, thus significantly reducing energy consumption and process costs. Employing a low-cycle fatigue loading method, the operation process is simple, with a single processing cycle typically not exceeding 2 hours, significantly improving processing efficiency. The entire process requires no chemical reagents and produces no harmful emissions, meeting the requirements of green manufacturing and sustainable development.
[0025] 3. This invention does not rely on traditional technical routes such as microalloying (e.g., adding Zn, Cu, Sc, Zr, etc.) or severe plastic deformation. Therefore, it avoids the increased costs and recycling barriers caused by multi-element alloying, and also avoids the problems of decreased plasticity and new corrosion initiation sites caused by severe plastic deformation. This process can be directly implemented on existing fatigue testing platforms, providing an innovative technical route for high-quality 5-series aluminum alloy components that does not change the alloy composition and completes key strengthening steps at room temperature. It has good industrial applicability and promotional value.
[0026] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description
[0027] Figure 1 This is a dimensional diagram of an alloy sample of 5-series aluminum alloy.
[0028] Figure 2 The figures show a comparison of the mechanical properties and corrosion resistance of the strengthened 5-series aluminum alloys in each embodiment and each comparative embodiment.
[0029] Figure 3 The typical microstructure features of the 5-series aluminum alloy strengthened in Example 1 are shown under a transmission electron microscope (TEM). Detailed Implementation
[0030] To make the technical means, creative features, objectives, and effects of this invention clearer and easier to understand, the invention will be further described below in conjunction with the accompanying drawings and specific embodiments:
[0031] Example 1
[0032] The 5-series aluminum alloy used in this embodiment, by mass fraction, includes 8.6% Mg, with the balance being Al and unavoidable impurities. The specific method for strengthening it is as follows:
[0033] S1. The 5-series aluminum alloy was processed according to the GB / T 26077-2021 standard to obtain alloy samples;
[0034] S2. Cover the surface of the alloy sample prepared in S1 with a 10 mm thick layer of carbon powder to reduce its oxidation, and then place it in a solution furnace to solidify at 460 °C and hold for 3 h; then take out the alloy sample that has reached the supersaturated solid solution state, and perform water quenching treatment at room temperature, ensuring that the quenching transfer time is less than 30 s.
[0035] S3. The alloy sample after S2 quenching is placed in the LF5105 fatigue testing system. Under a 0.2Hz sinusoidal waveform, the alloy sample is subjected to 500 cycles of symmetrical tensile-compression treatment with horizontal stress to obtain the strengthened 5-series aluminum alloy.
[0036] Example 2
[0037] The 5-series aluminum alloy used in this embodiment, by mass fraction, includes 5.7% Mg, with the balance being Al and unavoidable impurities. The specific method for strengthening it is as follows:
[0038] S1. The 5-series aluminum alloy was processed according to the GB / T 26077-2021 standard to obtain alloy samples;
[0039] S2. Cover the surface of the alloy sample prepared in S1 with a 9 mm thick layer of carbon powder to reduce its oxidation, and then place it in a solution furnace to solidify at 450 °C and hold for 3 h; then take out the alloy sample that has reached the supersaturated solid solution state, and perform water quenching treatment at room temperature, ensuring that the quenching transfer time is less than 30 s.
[0040] S3. The alloy sample after S2 quenching is placed in the LF5105 fatigue testing system. Under a 0.2Hz sinusoidal waveform, the alloy sample is subjected to 500 cycles of symmetrical tensile-compression treatment with horizontal stress to obtain the strengthened 5-series aluminum alloy.
[0041] Example 3
[0042] The 5-series aluminum alloy used in this embodiment, by mass fraction, includes 4.0% Mg, with the balance being Al and unavoidable impurities. The specific method for strengthening it is as follows:
[0043] S1. The 5-series aluminum alloy was processed according to the GB / T 26077-2021 standard to obtain alloy samples;
[0044] S2. Cover the surface of the alloy sample prepared in S1 with a 9 mm thick layer of carbon powder to reduce its oxidation, and then place it in a solution furnace to solidify at 450 °C and hold for 3 h; then take out the alloy sample that has reached the supersaturated solid solution state, and perform water quenching treatment at room temperature, ensuring that the quenching transfer time is less than 30 s.
[0045] S3. The alloy sample after S2 quenching is placed in the LF5105 fatigue testing system. Under a 0.18Hz sinusoidal waveform, the alloy sample is subjected to 650 cycles of symmetrical tensile-compression treatment with horizontal stress to obtain the strengthened 5-series aluminum alloy.
[0046] Example 4
[0047] The 5-series aluminum alloy used in this embodiment, by mass fraction, includes 2.4% Mg, with the balance being Al and unavoidable impurities. The specific method for strengthening it is as follows:
[0048] S1. The 5-series aluminum alloy was processed according to the GB / T 26077-2021 standard to obtain alloy samples;
[0049] S2. Cover the surface of the alloy sample prepared in S1 with an 8 mm thick layer of carbon powder to reduce its oxidation, and then place it in a solution furnace to solidify at 440℃ and hold for 3 h; then take out the alloy sample that has reached the supersaturated solid solution state, and perform water quenching treatment at room temperature, ensuring that the quenching transfer time is less than 30 s.
[0050] S3. The alloy sample after S2 quenching is placed in the LF5105 fatigue testing system. Under a 0.18Hz sinusoidal waveform, the alloy sample is subjected to 800 cycles of symmetrical tensile-compression treatment with horizontal stress to obtain the strengthened 5-series aluminum alloy.
[0051] Comparative Example 1
[0052] Compared with Example 1, steps 2-3 are omitted, while the rest are the same.
[0053] Comparative Example 2
[0054] Compared with Example 2, steps 2-3 are omitted, while the rest are the same.
[0055] Comparative Example 3
[0056] Compared with Example 3, steps 2-3 are omitted, while the rest are the same.
[0057] Comparative Example 4
[0058] Compared with Example 4, steps 2-3 are omitted, while the rest are the same.
[0059] In the examples 1-4 and comparative examples 1-4, the 5-series aluminum alloys used were initially extruded bars with a diameter of 15-40 mm and an initial microstructure of equiaxed grains with a grain size of 20-60 μm. The alloy samples obtained after subsequent processing included two coaxially arranged clamping sections and a gauge length section. The gauge length section was fixedly connected between the two clamping sections. The diameter of the gauge length section was 6.0 ± 0.1 mm, and the length was 15 ± 0.1 mm. The diameter of each clamping section was 12.0 ± 0.1 mm, and the length was 40 ± 0.5 mm. The gauge length section transitioned to the two clamping sections via an arc surface with a radius of 30.0 ± 0.5 mm.
[0060] Furthermore, the operation interval between steps S2 and S3 in Examples 1-4 is less than 10 minutes to reduce the natural aging of the 5-series aluminum alloy itself.
[0061] Furthermore, in step S3 of Examples 1-4, the horizontal stress applied to the alloy sample must satisfy the following:
[0062]
[0063] Among them, σ0 and σ max These represent the yield strength and tensile strength of the quenched alloy, respectively; N total and N i These represent the total number of cycles during the stretch-compression process and the number of cycles for the i-th cycle, respectively.
[0064] Next, the mechanical properties and corrosion resistance of the strengthened 5-series aluminum alloys from Examples 1-4 and Comparative Examples 1-4 were tested. For mechanical property testing, a uniaxial tensile test was conducted, measuring the yield strength, ultimate tensile strength, and elongation of the alloy specimens at 25°C. For corrosion resistance testing, the sensitization sensitivity test using the nitric acid mass loss test in ASTM-G67 was performed, measuring the mass loss of the 5-series aluminum alloys after sensitization at 150°C for 100 hours.
[0065] The specific test structure is shown in Table 1:
[0066]
[0067] Table 1. Test results of mechanical properties and corrosion resistance of alloy samples
[0068] According to the data in the table, the yield strength of all embodiments is better than that of the corresponding comparative examples, indicating that the strengthening method of the present invention can significantly improve the yield strength of 5-series aluminum alloys, and the strengthening effect is greater for 5-series aluminum alloys with low Mg content. As for tensile strength, although the tensile strength of all embodiments is better than that of the corresponding comparative examples, the improvement is small. As for elongation, the elongation of all embodiments is lower than that of the corresponding comparative examples, indicating that 5-series aluminum alloys will sacrifice some plasticity after strengthening treatment, and the higher the Mg content, the more obvious the effect.
[0069] Meanwhile, the data in the table also shows that the corrosion resistance of all embodiments is better than that of the corresponding comparative examples, especially when the Mg content is higher than 3.5 wt.%, the corrosion resistance is more obvious.
[0070] Therefore, the strengthening method provided by the present invention can significantly improve the mechanical properties and corrosion resistance of 5-series aluminum alloys, providing a new approach for 5-series aluminum alloys to balance mechanical properties and corrosion resistance.
[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.
Claims
1. A 5-series aluminum alloy, characterized in that, It contains, by mass fraction: Mg 2.4-8.6%, with the balance being Al and unavoidable impurities.
2. The strengthening method for 5-series aluminum alloys according to claim 1, characterized in that, Includes the following steps: S1. The 5-series aluminum alloy is processed to obtain an alloy sample; S2. After solution treatment, the alloy sample obtained in S1 is quenched at room temperature; S3. After cyclic plasticizing treatment of the alloy sample quenched in S2, a strengthened 5-series aluminum alloy is obtained.
3. The strengthening method for 5-series aluminum alloys according to claim 2, characterized in that, In step S1, the alloy sample includes two coaxially arranged clamping sections and a gauge length section. The gauge length section is fixedly connected between the two clamping sections. The diameter of the gauge length section is 6.0±0.1mm, and the length of the gauge length section is 15±0.1mm. The diameter of each clamping section is 12.0±0.1mm, and the length of each clamping section is 40±0.5mm. The gauge length section is connected to the two clamping sections by an arc surface with a radius of 30.0±0.5mm.
4. The strengthening method for 5-series aluminum alloys according to claim 2, characterized in that, In step S2, before solution treatment, the surface of the alloy sample needs to be covered with a layer of carbon powder 8-10 mm thick.
5. The strengthening method for a 5-series aluminum alloy according to claim 2, characterized in that, In step S2, the solution temperature is 440~460℃, and the solution is kept at that temperature for 3 hours.
6. The strengthening method for a 5-series aluminum alloy according to claim 2, characterized in that, In step S2, the quenching method is water quenching, and the quenching transfer time is less than 30 seconds.
7. A strengthening method for 5-series aluminum alloys according to claim 2, characterized in that, In step S3, the specific method of cyclic plastic treatment is as follows: the alloy sample that has been quenched in S2 is placed in the fatigue test system, and under a sinusoidal waveform, a horizontal stress is applied to the alloy sample to perform multiple cycles of symmetrical tensile-compression treatment.
8. The strengthening method for a 5-series aluminum alloy according to claim 7, characterized in that, The frequency of the sine wave is 0.15~0.2Hz.
9. A strengthening method for 5-series aluminum alloys according to claim 7, characterized in that, The horizontal stress applied to the alloy specimen must meet the following requirements: Among them, σ0 and σ max These represent the yield strength and tensile strength of the quenched alloy, respectively; N total and N i These represent the total number of cycles during the stretch-compression process and the number of cycles for the i-th cycle, respectively.
10. A method for strengthening 5-series aluminum alloys according to claim 7, characterized in that, The cycle count is 500-800 times.