An optimized method for the solid solution treatment process and preparation method of cerium-containing aluminum alloys.

Abstract

This invention discloses an optimized solution treatment process and preparation method for cerium-containing aluminum alloys, belonging to the technical field of aluminum alloy heat treatment processes. The cerium-containing aluminum alloy, by mass percentage, comprises Cu 6%–9%, ​​Ce 0.75%–1.5%, Mn 0.5%–1.2%, Sc 0.05%–0.17%, Zr 0%–0.34%, with the balance being Al and unavoidable impurities. This invention optimizes the solution treatment process by altering the hardness of the aluminum alloy, thereby improving its high-temperature mechanical properties. Its tensile strength can reach 202 MPa, significantly enhancing the long-term service capability of cast heat-resistant aluminum alloys at high temperatures.

Description

Technical Field

[0001] This invention relates to the field of metallurgical heat treatment technology, specifically to an optimized method and preparation method for a solution treatment process of cerium-containing aluminum alloys. Background Technology

[0002] Aluminum alloys are widely used in the aerospace industry due to their excellent mechanical properties, such as high strength-to-weight ratio, specific stiffness, corrosion resistance, recyclability, high strength and toughness, high corrosion resistance, and good machinability. The performance of aluminum alloy materials directly determines the service performance of these aircraft components. With the development of technology, higher requirements have been placed on aluminum alloys to serve at higher temperatures, making the development of new heat-resistant and high-strength aluminum alloys an urgent matter.

[0003] The coarsening of heat-resistant phases such as Al2Cu and the weakening of traditional strengthening mechanisms in existing heat-resistant aluminum alloys at 350℃ and above mean that the high-temperature strength of cast aluminum alloys is essentially reaching its limit. The instantaneous high-temperature tensile strength (tensile strength) at 350℃ does not show a rapid and significant increase after reaching 100 MPa, indicating a technological bottleneck and significant challenges in high-temperature research. Current research often employs alloying / microalloying to form complex intermetallic compounds with high thermal stability, which can improve the high-temperature strength of alloys to some extent. However, these compounds often form during solidification, and as their quantity increases, their shapes become more complex. Being intermetallic compounds themselves, their inherent brittleness and structural brittleness severely limit the improvement of high-temperature strength.

[0004] Cheng Jianing et al. improved the heat resistance of aluminum alloys through microalloying, thus developing the ZL206 alloy. In the T6 state, its high-temperature tensile strength at 300℃ is 161MPa, while the ZL835 alloy has a high-temperature tensile strength of 186MPa at 300℃. However, the high-temperature strength performance of these aluminum alloys still cannot meet the latest requirements of the current automotive and aerospace fields. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides an optimized method for the solution treatment process and preparation method of cerium-containing aluminum alloys. By changing the solution treatment time, the mechanical properties of cerium-containing aluminum alloys can be effectively enhanced, meeting the current application requirements in the automotive and aerospace fields.

[0006] This invention is achieved through the following technical solution:

[0007] An optimized method for the solid solution treatment process of cerium-containing aluminum alloys includes the following steps:

[0008] Step 1: Perform the first solution treatment on the aluminum alloy ingot at the first solution temperature, establish the hardness change curve of the aluminum alloy ingot over time, obtain the time period corresponding to the peak hardness range of the aluminum alloy ingot based on the curve, and determine the first solution treatment process of the aluminum alloy ingot based on the time period of the peak hardness range.

[0009] Step 2: Perform the first solution treatment on the new aluminum alloy ingot according to the first solution treatment process obtained in Step 1;

[0010] Step 3: Perform a second solution treatment on the aluminum alloy ingot after the first solution treatment at the second solution temperature, and use the method in Step 1 to determine the second solution treatment process for the aluminum alloy ingot.

[0011] Step 4: Perform two solution treatments on the new aluminum alloy ingot according to the first solution treatment process obtained in Step 1 and the second solution treatment process obtained in Step 3.

[0012] Step 5: Perform a third solution treatment on the aluminum alloy ingot after the two solution treatments in Step 4 at the third solution temperature, and use the same method as in Step 1 to determine the third solution treatment process for the aluminum alloy ingot.

[0013] Step 6: Use the three-stage solution treatment process as a multi-stage solution treatment process for cerium-containing aluminum alloys.

[0014] Preferably, in step 1, the hardness of the aluminum alloy ingot is collected at set time intervals, and a hardness change curve is established based on the collection time and the corresponding hardness.

[0015] Preferably, the first solution temperature is 200℃~300℃, the second solution temperature is 400℃~500℃, and the third solution temperature is 520℃~537℃.

[0016] Preferably, the solution treatment time for the first solution treatment process is 3-5 hours, and the temperature is 200℃-300℃.

[0017] The second solution treatment process takes 1.5-3 hours and is carried out at a temperature of 400℃-500℃.

[0018] The solution treatment time for the third solution treatment process is 0.5h-1.5h, and the temperature is 520℃~537℃.

[0019] A method for preparing an aluminum-copper-cerium-based heat-resistant aluminum alloy includes the following steps:

[0020] Step 1: Prepare aluminum alloy ingots;

[0021] Step 2: According to the optimization method of the solution treatment process according to any one of claims 1-4, determine the three-stage solution treatment process of the aluminum alloy ingot in step 1 and perform solution treatment, and cool the solution-treated aluminum alloy ingot to room temperature to obtain the solution-treated aluminum alloy.

[0022] Step 3: Perform a three-stage aging treatment on the aluminum alloy obtained in Step 2 to obtain a copper-cerium heat-resistant aluminum alloy.

[0023] Preferably, the aluminum-copper-cerium heat-resistant aluminum alloy comprises, by mass percentage, 6%–9% Cu, 0.75%–1.5% Ce, 0.5%–1.2% Mn, 0.05%–0.17% Sc, 0%–0.34% Zr, with the balance being aluminum.

[0024] Preferably, the method for preparing the aluminum alloy ingot is as follows:

[0025] S1. Melt the Al and Al-Mn master alloy in a graphite crucible in a resistance furnace and hold at 720℃-820℃ for 2.5h.

[0026] S2. Add Al-Cu master alloy, Al-Zr master alloy and Al-RE master alloy to the alloy solution obtained in S1 and melt it, and keep it at 720℃-820℃ for 1.5h.

[0027] S3. The alloy solution obtained in S2 is refined and degassed by passing argon gas through it at 700℃-720℃, and then cooled to obtain an aluminum alloy ingot.

[0028] Preferably, the method for the three-level timeliness processing is as follows:

[0029] The first-level aging treatment was carried out at a temperature of 175℃ for 10 hours.

[0030] The secondary aging treatment was carried out at a temperature of 250℃ for 24 hours.

[0031] The third-level aging treatment is carried out at a temperature of 300℃ for 24 hours.

[0032] Compared with the prior art, the present invention has the following beneficial technical effects:

[0033] This invention provides an optimized method for the solution treatment process of cerium-containing aluminum alloys. This method overcomes the shortcomings of traditional methods that determine the optimal solution time through microstructural observation. This is because the microstructure of this alloy is relatively complex, with many precipitated phases. It is impossible to accurately determine the optimal solution time solely based on changes in microstructure. Furthermore, submicron-sized W-(Al,Cu,Sc) ternary phases are formed during the solution treatment process. The appearance of the W phase is often disastrous, mainly because the W phase not only consumes Cu atoms but also consumes a large number of precious Sc atoms. Therefore, finding the optimal solution time through a faster and more accurate method of hardness testing avoids the aforementioned problems. The main reason for this approach is that the hardness begins to increase within a certain period after the initial solution treatment. This is because the second-phase particles distributed in the matrix dissolve back into the matrix, causing lattice distortion and increasing the resistance to dislocation movement between lattice cells, thus increasing the hardness. At this point, solid solution strengthening plays a major role. As the solution treatment time continues to increase, the hardness of the aluminum alloy begins to decrease. This is because, with further extension of the solution treatment time, the second-phase particles are almost entirely dissolved back into the matrix, the solid solution strengthening effect remains unchanged, and the grains coarsen, so solid solution strengthening no longer plays a dominant role, resulting in a decrease in the overall hardness value. The solution treatment process determined in this application significantly improves the high-temperature mechanical properties of the cerium-containing aluminum alloy, with a tensile strength reaching 202 MPa and a yield strength reaching 150 MPa. Attached Figure Description

[0034] Figure 1 This is a hardness diagram of the cerium-containing aluminum alloy at 250℃ solution treatment time.

[0035] Figure 2 This is a hardness diagram of the cerium-containing aluminum alloy of the present invention, obtained by solution treatment at 450℃.

[0036] Figure 3 This is a hardness diagram of the cerium-containing aluminum alloy of the present invention, obtained after solution treatment at 537℃.

[0037] Figure 4 This is a high-temperature tensile test diagram of the cerium-containing aluminum alloy of the present invention at 300°C. Detailed Implementation

[0038] The present invention will now be described in further detail with reference to the accompanying drawings. These descriptions are intended to explain the invention and not to limit it.

[0039] An optimization method for multi-stage solid solution treatment of cerium-containing aluminum alloys includes the following steps:

[0040] Step 1: Perform the first solution treatment on the aluminum alloy ingot at 200℃~300℃. Collect the hardness of the aluminum alloy ingot at set time intervals to establish a hardness change curve of the aluminum alloy ingot over time. Based on the curve, obtain the time period corresponding to the peak hardness range of the aluminum alloy ingot. Determine the first solution treatment process of the aluminum alloy ingot based on the time period of the peak range.

[0041] During the continuous heat preservation process, the hardness of aluminum alloy ingots will increase with the extension of time. After reaching the peak hardness, the hardness will decrease and fluctuate with the extension of heat preservation time. In this application, the time period corresponding to the peak range in the hardness curve is taken as the optimal solution time, and then combined with the solution temperature to form a solution process.

[0042] In this embodiment, the aluminum alloy ingot is heat-treated at 200℃~300℃, and the hardness is measured every hour or less. A hardness change curve is established based on the time and hardness of each measurement. The steady-state hardness of the aluminum alloy ingot can be quickly determined based on the curve. The time range corresponding to the steady-state hardness of the aluminum alloy ingot is taken as the solution treatment time. Combined with the solution treatment temperature, the first solution treatment process can be obtained.

[0043] Step 2: Perform the first solution treatment on the new aluminum alloy ingot according to the first solution treatment process obtained in Step 1;

[0044] Obtain an aluminum alloy ingot with the same composition as in step 1, and perform a solution treatment on the aluminum alloy ingot according to the first solution treatment process determined in step 1. Use a new aluminum alloy ingot with the same composition for solution treatment and use it as a sample to determine the second solution treatment process. This can effectively ensure the accuracy of the solution treatment process.

[0045] Step 3: Perform a second solution treatment on the aluminum alloy ingot after the first solution treatment at 400℃~500℃, and use the method in Step 1 to determine the second solution treatment process for the aluminum alloy ingot.

[0046] Step 4: Perform two solution treatments on the new aluminum alloy ingot according to the first solution treatment process obtained in Step 1 and the second solution treatment process obtained in Step 3.

[0047] Step 5: Perform a third solution treatment on the aluminum alloy ingot after the two solution treatments in Step 4 at 520℃~537℃, and use the same method as in Step 1 to determine the third solution treatment process for the aluminum alloy ingot.

[0048] Step 6: Use the three-stage solution treatment process as a multi-stage solution treatment process for aluminum alloy ingots.

[0049] Example 1

[0050] An optimization method for multi-stage solid solution treatment of cerium-containing aluminum alloys includes the following steps:

[0051] Step 1: Perform a first solution treatment on the aluminum alloy at 250℃. Test the hardness of the aluminum alloy every 0.5 hours and record the time and temperature. The total heating time is 18 hours. Establish a hardness change curve based on the hardness and time. Figure 1 .

[0052] See Figure 1 Based on the hardness change trend, the hardness shows an upward trend when the heat preservation time is 1h-4h, and reaches a peak within 4h-6h. As the time continues to increase, it always fluctuates around the peak hardness range. Therefore, the solution time of the first solution process is determined to be 3h-5h and the temperature is 200℃~300℃. Preferably, the first solution process is a solution time of 4.5h and a temperature of 250℃.

[0053] Step 2: Collect new aluminum alloy and perform solution treatment according to the first solution treatment process. After the first solution treatment, perform a second solution treatment at 450℃. Test the hardness of the aluminum alloy every 0.5 hours, recording the time and temperature. The total heating time is 6 hours. Establish a hardness change curve based on the hardness and time. Figure 2 .

[0054] See Figure 2 After the first solution treatment, the aluminum alloy ingot undergoes a second solution treatment. The hardness reaches its maximum value after 2.5 hours of holding. If the holding time is extended, the hardness continues to decrease. Therefore, the solution time for the second solution treatment is determined to be 1.5-3 hours and the temperature is 400℃-500℃. Preferably, the solution time for the second solution treatment is 2.5 hours and the temperature is 450℃.

[0055] Step 3: Collect new aluminum alloy and perform two solution treatments sequentially according to the first and second solution treatment processes. Then, perform a third solution treatment at 537℃. Test the hardness of the aluminum alloy every 0.5 hours and record the time and temperature. The total heating time is 10 hours. Establish a hardness change curve based on the hardness and time. Figure 3 .

[0056] See Figure 3 After two solution treatments, the hardness of the aluminum alloy ingot reaches its maximum after holding at that temperature for 1 hour. Further extending the holding time results in a continuous decrease in hardness.

[0057] Therefore, when the solution time for the third solution treatment is determined to be 0.5h-1.5h, the temperature is 520℃-537℃. Preferably, the solution time for the third solution treatment is 1h, and the temperature is 537℃.

[0058] Step 4: Perform solution treatment on the new aluminum alloy according to the three-stage solution treatment process obtained in Steps 1-3, and then perform quenching treatment to obtain a high-strength creep-resistant aluminum alloy.

[0059] Example 2

[0060] A heat-resistant aluminum alloy based on copper and cerium, comprising, by mass percentage, 6%–9% Cu, 0.75%–1.5% Ce, 0.5%–1.2% Mn, 0.05%–0.17% Sc, 0%–0.34% Zr, with the balance being aluminum.

[0061] The preparation method of this aluminum-copper-cerium-based heat-resistant aluminum alloy includes the following steps:

[0062] Step 1: Melt the Al and Al-Mn master alloy in a graphite crucible in a resistance furnace and hold at 720℃-820℃ for 2.5h;

[0063] Step 2: Add Al-Cu master alloy, Al-Zr master alloy and Al-RE master alloy to the alloy solution obtained in Step 1 and melt them, and keep it at 720℃-820℃ for 1.5h;

[0064] Step 3: The alloy solution obtained in Step 2 is refined and degassed by passing argon gas through it at 700℃-720℃. After standing and removing slag, the aluminum alloy solution is poured into an iron mold to form an aluminum alloy ingot.

[0065] Step 4: Perform a three-stage solution treatment on the aluminum alloy ingot obtained in Step 3. Cool the solution-treated aluminum alloy ingot to room temperature to obtain the solution-treated aluminum alloy.

[0066] The method for three-stage solution treatment is as follows:

[0067] The primary solution treatment was carried out at a temperature of 250℃ for 4.5 hours.

[0068] The secondary solution treatment was carried out at a temperature of 450℃ for 2.5 hours.

[0069] The temperature for the third-stage solution treatment was 537℃, and the time was 1 hour.

[0070] Step 5: Perform a three-stage aging treatment on the aluminum alloy obtained in Step 4 to obtain a copper-cerium heat-resistant aluminum alloy.

[0071] The method for handling Level 3 timeliness is as follows:

[0072] The first-level aging treatment is carried out at a temperature of 175℃ for 10 hours.

[0073] The secondary aging treatment was carried out at a temperature of 250℃ for 24 hours.

[0074] The third-level aging treatment is carried out at a temperature of 300℃ for 24 hours.

[0075] The performance of the aluminum-copper-cerium-based heat-resistant aluminum alloy prepared in this application was compared with that of existing aluminum alloys, and the results are shown in Table 1.

[0076] Table 1

[0077] ZL201A 300℃ T5 137 MPa ZL206 300℃ T6 161 MPa ZL207 300℃ T1 90 MPa Prior copper-cerium heat-resistant aluminum alloy 300℃ T6 186 MPa Copper-cerium heat-resistant aluminum alloy of the present application 300℃ T6 202 MPa

[0078] See Figure 4 The aluminum-copper-cerium-based heat-resistant aluminum alloy prepared using the method described in this application exhibits a tensile strength at 300°C that significantly exceeds that of existing heat-resistant aluminum alloys. This invention improves the high-temperature stability of the reinforcing phase through optimized heat treatment processes, thereby achieving excellent tensile strength; the high-temperature tensile strength at 300°C exceeds 200 MPa.

[0079] In the preparation of this aluminum-copper-cerium-based heat-resistant aluminum alloy, a solution pretreatment at 200℃~300℃ for 4h~6h was used to form high-density RE element solute atom clusters. A further solution pretreatment at 400℃~500℃ for 2h~3h was used, with these high-density RE solute atom clusters serving as heterogeneous nucleation sites to form a high-density Al3Zr nanoprecipitate phase. A solution treatment at 520℃~537℃ was then used to remelt the Al2Cu intermetallic compound. This process involved a competition between the hardness decrease caused by the remelting of the micron-scale eutectic phase and the strengthening effect of the solution atoms, while ensuring that the high-density Al3Zr nanoprecipitate phase did not significantly coarsen. A solution treatment at 150℃ was then employed. The two-stage aging process of ℃~200℃ / 5h~30h+250℃~300℃ / >1h uses Al3Zr nano-precipitate phase as heterogeneous nucleation sites to precipitate θ′-Al2Cu precipitate phase, and promotes the segregation of RE and Zr elements at the interface of θ′-Al2Cu precipitate phase to form a "diffusion barrier layer". This significantly improves the thermal stability of θ′-Al2Cu precipitate phase at 300℃~350℃, and solves the prominent problem that θ′-Al2Cu precipitate phase in copper-containing aluminum alloys is prone to coarsening at 300℃~350℃, and thus gradually loses its strengthening effect, resulting in a limited high-temperature life of the alloy.

[0080] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for preparing an aluminum-copper-cerium-based heat-resistant aluminum alloy, characterized in that, Includes the following steps: Step 1: Prepare aluminum alloy ingots, comprising, by mass percentage: Cu 6% ~ 9%, Ce 0.75% ~ 1.5%, Mn 0.5% ~ 1.2%, Sc 0.05% ~ 0.17%, Zr 0% ~ 0.34%, with the balance being aluminum; Step 2: Perform a first solution treatment on the aluminum alloy ingot at a first solution temperature of 200℃~300℃ to form high-density RE element solute atom clusters, establish a hardness curve of the aluminum alloy ingot with time, obtain the time period corresponding to the peak hardness range of the aluminum alloy ingot according to the curve, and determine the first solution treatment process of the aluminum alloy ingot according to the time period of the peak range. The solution treatment time for the first solution treatment process is 3-5 hours. Step 3: Perform the first solution treatment on the new aluminum alloy ingot according to the first solution treatment process obtained in Step 2; Step 4: Perform a second solution treatment on the aluminum alloy ingot after the first solution treatment at a second solution temperature of 400℃~500℃, so as to use the atomic clusters as heterogeneous nucleation points to form a high-density Al3Zr nano precipitate phase, and use the method in Step 2 to determine the second solution process of the aluminum alloy ingot. Step 5: Perform two solution treatments on the new aluminum alloy ingot according to the first solution treatment process obtained in Step 2 and the second solution treatment process obtained in Step 4. The solution treatment time for the second solution treatment process is 1.5h-3h. Step 6: Perform a third solution treatment on the aluminum alloy ingot after the two solution treatments in Step 5 at a third solution temperature of 520℃~537℃, so as to remelt the Al2Cu intermetallic compound while ensuring that the Al3Zr nano precipitate phase does not significantly coarsen. The third solution process of the aluminum alloy ingot is determined by the same method as in Step 2. The solution treatment time for the third solution treatment process is 0.5h-1.5h. Step 7: Use the three-stage solution treatment process as the multi-stage solution treatment process for cerium-containing aluminum alloys. Perform solution treatment on the aluminum alloy ingot according to the multi-stage solution treatment process. Quench and cool the solution-treated aluminum alloy ingot to room temperature to obtain the solution-treated aluminum alloy. Step 8: Perform a three-stage aging treatment on the solution-treated aluminum alloy to obtain a copper-cerium heat-resistant aluminum alloy with a tensile strength of up to 202 MPa and a yield strength of up to 150 MPa at 300℃.

2. The method for preparing an aluminum-copper-cerium-based heat-resistant aluminum alloy according to claim 1, characterized in that, In step 2, the hardness of the aluminum alloy ingot is collected at set time intervals, and a hardness change curve is established based on the collection time and the corresponding hardness.

3. The method for preparing an aluminum-copper-cerium-based heat-resistant aluminum alloy according to claim 1, characterized in that, The method for preparing the aluminum alloy ingot is as follows: S1. Melt the Al and Al-Mn master alloy in a graphite crucible in a resistance furnace and hold at 720℃ - 820℃ for 2.5h. S2. Add Al-Cu master alloy, Al-Zr master alloy and Al-RE master alloy to the alloy solution obtained in S1 and melt it, and keep it at 720℃-820℃ for 1.5h. S3. The alloy solution obtained in S2 is refined and degassed by passing argon gas through it at 700 ℃ - 720 ℃, and then cooled to obtain an aluminum alloy ingot.

4. The method for preparing an aluminum-copper-cerium-based heat-resistant aluminum alloy according to claim 1, characterized in that, The method for the three-level timeliness processing is as follows: The first-level aging treatment was carried out at a temperature of 175℃ for 10 hours. The secondary aging treatment was carried out at a temperature of 250℃ for 24 hours. The third-level aging treatment is carried out at a temperature of 300℃ for 24 hours.

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