A heat treatment method capable of reducing the yield strength ratio of aluminum-lithium alloy

Abstract

The present application belongs to the technical field of metal material processing and heat treatment, and particularly relates to a heat treatment method capable of reducing the yield strength ratio of an aluminum-lithium alloy, comprising the following steps: a) heating and holding the aluminum-lithium alloy at 510-530 DEG C for 1-2 hours, and then water quenching to obtain a supersaturated solid solution; b) aging treating the supersaturated solid solution at 70-90 DEG C for 18-28 hours, and then aging treating at 170-190 DEG C for 2-4 hours; c) deforming the material treated in step b) at a temperature of 140-190 DEG C, and the deformation amount is controlled at 0.5-1.5%; and d) aging treating the material treated in step c) at 140-150 DEG C for 8-16 hours. The present application ingeniously utilizes the synergistic effect of multi-stage aging and micro-temperature deformation, and effectively solves the technical contradiction that the high strength and low yield strength ratio of the aluminum-lithium alloy are difficult to be considered simultaneously.

Description

Technical Field

[0001] This invention belongs to the field of metal material processing and heat treatment technology, and particularly relates to a heat treatment method that can reduce the yield strength ratio of aluminum-lithium alloys. Background Technology

[0002] Aluminum-lithium alloys are important lightweight structural materials in the aerospace field, but their application is limited by the difficulty of balancing strength and plasticity. Traditional T8 heat treatment (deformation aging) mainly introduces high-density dislocations through cold deformation. During aging, the T phase precipitates on the dislocations, which can improve strength, but the yield strength ratio is high (usually >90%), resulting in difficulties in subsequent forming and low service reliability.

[0003] While existing technologies, such as patent CN115433888B, have improved alloy properties through asynchronous rolling and annealing, they still fall short in controlling the yield strength ratio, failing to meet the requirements for low yield strength ratios in high-reliability components. Therefore, developing a deformation heat treatment method that can effectively reduce the yield strength ratio of aluminum-lithium alloys and improve their formability and service reliability is of great significance. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a heat treatment method that can reduce the yield strength ratio of aluminum-lithium alloys, which can significantly reduce the yield strength ratio of aluminum-lithium alloys while maintaining their high strength.

[0005] This invention provides a heat treatment method for reducing the yield strength ratio of aluminum-lithium alloys, comprising the following steps:

[0006] a) Heat the aluminum-lithium alloy at 510~530℃ and hold for 1~2 hours, then quench it with water to obtain a supersaturated solid solution;

[0007] b) The supersaturated solid solution is aged at 70-90°C for 18-28 hours, followed by aging at 170-190°C for 2-4 hours;

[0008] c) The material treated in step b) is subjected to deformation heat treatment in a temperature range of 140~190℃, with the deformation amount controlled at 0.5~1.5%;

[0009] d) The material treated in step c) is aged at 140~150℃ for 8~16h.

[0010] Preferably, in step a), the heating and heat preservation temperature is 515~520℃.

[0011] Preferably, in step b), the temperature of the first aging treatment is 80~86℃.

[0012] Preferably, in step b), the time for the first stage of aging treatment is 20~24h.

[0013] Preferably, in step b), the temperature of the second aging treatment is 175~180℃.

[0014] Preferably, in step b), the time for the second aging process is 2.5 to 3 hours.

[0015] Preferably, in step c), the temperature range of the deformation heat treatment is 155~180℃.

[0016] Preferably, in step c), the deformation amount of the deformation heat treatment is 1~1.2%.

[0017] Preferably, in step d), the aging treatment temperature is 145~150℃.

[0018] Preferably, in step d), the aging process takes 12 to 15 hours.

[0019] Compared with existing technologies, this invention provides a heat treatment method for reducing the yield strength ratio of aluminum-lithium alloys, comprising the following steps: a) heating the aluminum-lithium alloy at 510~530℃ and holding for 1~2 hours, followed by water quenching to obtain a supersaturated solid solution; b) aging the supersaturated solid solution at 70~90℃ for 18~28 hours, followed by aging at 170~190℃ for 2~4 hours; c) subjecting the material treated in step b) to deformation heat treatment in a temperature range of 140~190℃, with the deformation amount controlled at 0.5~1.5%; d) aging the material treated in step c) at 140~150℃ for 8~16 hours. This invention cleverly utilizes the synergistic effect of multi-stage aging and micro-temperature deformation, effectively solving the technical contradiction of balancing high strength and low yield strength ratio in aluminum-lithium alloys. More specifically, it has at least the following advantages:

[0020] (1) The yield strength ratio is significantly reduced: The present invention successfully reduced the yield strength ratio from more than 90% in the traditional T8 state to less than 86%, which means that the material still has sufficient plastic deformation capacity after yielding, fundamentally solving the problem of cold forming cracking caused by high yield strength ratio;

[0021] (2) Maintained high strength level: While the yield strength ratio is greatly reduced, the tensile strength of the material treated by the method of the present invention can still be maintained at a high level of more than 580MPa, achieving the best match between strength and yield strength ratio, which is impossible to achieve by traditional T8 and T6 processes;

[0022] (3) Improved service reliability and safety: A lower yield ratio means that if the component yields locally during service, its stress will be redistributed, with higher overload tolerance and safety margin, which significantly improves the reliability of the final component.

[0023] (4) Strong process controllability: The amount of deformation of micro-temperature deformation is extremely small (0.5~1.5%), which is much smaller than that of traditional cold deformation (3~8%). It is easier to control precisely, the process stability is high, the product performance consistency is better, and it is conducive to industrial production application. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0025] Figure 1 This is a stress-strain curve of the aluminum-lithium alloy after treatment by the method of Example 1 provided by the present invention;

[0026] Figure 2 This is a stress-strain curve of the aluminum-lithium alloy after treatment by the method of Example 2 provided by the present invention;

[0027] Figure 3 This is a stress-strain curve of the aluminum-lithium alloy after being treated by the method of Comparative Example 1, provided by the present invention.

[0028] Figure 4 This is a stress-strain curve of the aluminum-lithium alloy after being treated by the method of Comparative Example 2, provided by the present invention.

[0029] Figure 5 This is a stress-strain curve of the aluminum-lithium alloy after being treated by the method of Comparative Example 3, provided by the present invention.

[0030] Figure 6 This is a stress-strain curve of the aluminum-lithium alloy after being treated by the method in Comparative Example 4, provided by the present invention. Detailed Implementation

[0031] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] This invention provides a heat treatment method for reducing the yield strength ratio of aluminum-lithium alloys, comprising the following steps:

[0033] a) Heat the aluminum-lithium alloy at 510~530℃ and hold for 1~2 hours, then quench it with water to obtain a supersaturated solid solution;

[0034] b) The supersaturated solid solution is aged at 70-90°C for 18-28 hours, followed by aging at 170-190°C for 2-4 hours;

[0035] c) The material treated in step b) is subjected to deformation heat treatment in a temperature range of 140~190℃, with the deformation amount controlled at 0.5~1.5%;

[0036] d) The material treated in step c) is aged at 140~150℃ for 8~16h.

[0037] In the heat treatment method provided by the present invention, in step a), the composition of the aluminum-lithium alloy preferably includes Cu, Li, Mg, Ag, Zr and Al; wherein, the content of Cu is preferably 3~4.5wt%, specifically 3.9wt%; the content of Li is preferably 0.5~2wt%, specifically 1wt%; the content of Mg is preferably 0.4~0.7wt%, specifically 0.55wt%; the content of Ag is preferably 0.2~0.5wt%, specifically 0.35wt%; the content of Zr is preferably 0.07~0.15wt%, specifically 0.11wt%; and the content of Al is preferably the balance.

[0038] In the heat treatment method provided by this invention, the purpose of heating and holding in step a) is to fully dissolve the strengthening phase in the alloy. In step a), the preferred heating and holding temperature is 515~520℃; the preferred heating and holding time is 2 hours.

[0039] In the heat treatment method provided by the present invention, in step a), the aluminum-lithium alloy is rapidly water quenched after heating and heat preservation; wherein, the water quenching temperature is preferably 10~40℃, more preferably 25℃ (room temperature); the time for transferring the aluminum-lithium alloy after heating and heat preservation to water quenching is preferably controlled within 15s.

[0040] In the heat treatment method provided by this invention, the purpose of the first aging treatment in step b) is to form a high-density GP region (pre-dissolved atomic segregation region) in the alloy matrix. In step b), the temperature of the first aging treatment is preferably 80~86℃; the duration of the first aging treatment is preferably 20~24h.

[0041] In the heat treatment method provided by this invention, the purpose of the second aging treatment in step b) is to transform some of the GP regions in the alloy matrix into fine and uniform δ phases. In step b), the preferred temperature for the second aging treatment is 175~180℃; the preferred time for the second aging treatment is 2.5~3 hours.

[0042] In the heat treatment method provided by this invention, the purpose of the deformation heat treatment in step c) is mainly twofold: 1) Since the material has undergone pre-precipitation treatment (i.e., step b), its strength is improved, and cold deformation would lead to material damage; 2) To perform micro-deformation, introduce dislocations, and provide conditions to promote the precipitation of the T phase in the alloy matrix. In step c), the temperature range of the deformation heat treatment is preferably 155~180℃, more preferably 155~175℃ or 160~180℃; the deformation amount of the deformation heat treatment is preferably 1~1.2%. In this invention, the deformation amount refers to the ratio of the change in size before and after deformation to the size before deformation; the calculation formula is: |size before deformation - size after deformation| / size before deformation × 100%.

[0043] In the heat treatment method provided by this invention, the purpose of step d) is to promote the uniform and dispersed nucleation and precipitation of the T phase in the alloy matrix at the dislocations modified by the deformation heat treatment. In step d), the preferred temperature for the aging treatment is 145~150℃; the preferred aging time is 12~15h.

[0044] The heat treatment method provided by this invention ingeniously utilizes the synergistic effect of multi-stage aging and micro-temperature deformation, effectively solving the technical contradiction of balancing high strength and low yield strength ratio in aluminum-lithium alloys. More specifically, it has at least the following advantages:

[0045] (1) The yield strength ratio is significantly reduced: The present invention successfully reduced the yield strength ratio from more than 90% in the traditional T8 state to less than 86%, which means that the material still has sufficient plastic deformation capacity after yielding, fundamentally solving the problem of cold forming cracking caused by high yield strength ratio;

[0046] (2) Maintained high strength level: While the yield strength ratio is greatly reduced, the tensile strength of the material treated by the method of the present invention can still be maintained at a high level of more than 580MPa, achieving the best match between strength and yield strength ratio, which is impossible to achieve by traditional T8 and T6 processes;

[0047] (3) Improved service reliability and safety: A lower yield ratio means that if the component yields locally during service, its stress will be redistributed, with higher overload tolerance and safety margin, which significantly improves the reliability of the final component.

[0048] (4) Strong process controllability: The amount of deformation of micro-temperature deformation is extremely small (0.5~1.5%), which is much smaller than that of traditional cold deformation (3~8%). It is easier to control precisely, the process stability is high, the product performance consistency is better, and it is conducive to industrial production application.

[0049] For clarity, the following examples and comparative models will be used to provide a detailed description.

[0050] In the following embodiments and comparative examples of the present invention, the alloy composition of the 2195 aluminum-lithium alloy used is: 3.9 wt% Cu, 1 wt% Li, 0.55 wt% Mg, 0.35 wt% Ag, 0.11 wt% Zr, with the balance being aluminum.

[0051] Example 1

[0052] A heat treatment method for 2195 aluminum-lithium alloy includes the following steps:

[0053] S1: Heat the aluminum-lithium alloy at 515℃ for 2 hours to fully dissolve the reinforcing phase. After the holding time is completed, transfer it to the water quenching process within 15 seconds and quickly quench it to room temperature to obtain a supersaturated solid solution.

[0054] S2: Aging treatment at 80℃ for 24 hours;

[0055] S3: Aging treatment at 180℃ for 3 hours;

[0056] S4: The treated material is subjected to deformation heat treatment in a temperature range of 160~180℃, with the deformation amount controlled within 1%;

[0057] S5: Final aging treatment at 145℃ for 15 hours.

[0058] Example 2

[0059] A heat treatment method for 2195 aluminum-lithium alloy includes the following steps:

[0060] S1: Heat the aluminum-lithium alloy at 520℃ for 2 hours to fully dissolve the reinforcing phase. After the holding time is completed, transfer it to the water quenching process within 15 seconds and quickly quench it to room temperature to obtain a supersaturated solid solution.

[0061] S2: Aging treatment at 86℃ for 20 hours;

[0062] S3: Aging treatment at 175℃ for 2.5 hours;

[0063] S4: The treated material is subjected to deformation heat treatment in the temperature range of 155~175℃, and the deformation is controlled within 1.2%;

[0064] S5: Final aging treatment at 150℃ for 12 hours.

[0065] Comparative Example 1

[0066] A heat treatment method for 2195 aluminum-lithium alloy includes the following steps:

[0067] S1: Heat the aluminum-lithium alloy at 515℃ for 2 hours to fully dissolve the reinforcing phase. After the holding time is completed, transfer it to the water quenching process within 15 seconds and quickly quench it to room temperature to obtain a supersaturated solid solution.

[0068] S2: Aging treatment at 120℃ for 24 hours;

[0069] S3: Aging treatment at 180℃ for 3 hours;

[0070] S4: The treated material is subjected to deformation heat treatment in the temperature range of 160~180℃, and the deformation is controlled within 1%.

[0071] S5: Final aging treatment at 145℃ for 15 hours.

[0072] Comparative Example 2

[0073] A heat treatment method for 2195 aluminum-lithium alloy includes the following steps:

[0074] S1: Heat the aluminum-lithium alloy at 515℃ for 2 hours to fully dissolve the reinforcing phase. After the holding time is completed, transfer it to the water quenching process within 15 seconds and quickly quench it to room temperature to obtain a supersaturated solid solution.

[0075] S2: Aging treatment at 80℃ for 24 hours;

[0076] S3: Aging treatment at 180℃ for 3 hours;

[0077] S4: The treated material is cold-deformed at room temperature, with the deformation controlled within 3%;

[0078] S5: Final aging treatment at 145℃ for 15 hours.

[0079] Comparative Example 3

[0080] A heat treatment method for 2195 aluminum-lithium alloy includes the following steps:

[0081] S1: Heat the aluminum-lithium alloy at 515℃ for 2 hours to fully dissolve the reinforcing phase. After the holding time is completed, transfer it to the water quenching process within 15 seconds and quickly quench it to room temperature to obtain a supersaturated solid solution.

[0082] S2: Aging treatment at 160℃ for 24 hours.

[0083] Comparative Example 4

[0084] A heat treatment method for 2195 aluminum-lithium alloy includes the following steps:

[0085] S1: Heat the aluminum-lithium alloy at 515℃ for 2 hours to fully dissolve the reinforcing phase. After the holding time is completed, transfer it to the water quenching process within 15 seconds and quickly quench it to room temperature to obtain a supersaturated solid solution.

[0086] S2: Cold deformation is performed at room temperature, with the deformation amount controlled within 3%;

[0087] S3: Aging treatment at 150℃ for 30 hours.

[0088] Comparative Example 5

[0089] A heat treatment method for 2195 aluminum-lithium alloy includes the following steps:

[0090] S1: Heat the aluminum-lithium alloy at 515℃ for 2 hours to fully dissolve the reinforcing phase. After the holding time is completed, transfer it to the water quenching process within 15 seconds and quickly quench it to room temperature to obtain a supersaturated solid solution.

[0091] Performance Evaluation

[0092] The tensile strength, yield strength, and elongation of the aluminum-lithium alloys treated in Examples 1-2 and Comparative Examples 1-5 were tested, and the yield strength ratio was calculated. The stress-strain curves of the tensile tests in Examples 1-2 and Comparative Examples 1-4 are shown below. Figures 1-6 As shown in Table 1, the tensile strength, yield strength, elongation, and yield ratio of Examples 1-2 and Comparative Examples 1-5 are as follows.

[0093] Table 1 Performance test results of aluminum-lithium alloys treated under different conditions

[0094]

[0095] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A heat treatment method for reducing the yield strength ratio of aluminum-lithium alloys, characterized in that, Includes the following steps: a) Heat 2195 aluminum-lithium alloy at 510~530℃ for 1~2 hours, then quench it with water to obtain a supersaturated solid solution; b) The supersaturated solid solution is aged at 70-90°C for 18-28 hours, followed by aging at 170-190°C for 2-4 hours; c) The material treated in step b) is subjected to deformation heat treatment in a temperature range of 140~190℃, with the deformation amount controlled at 0.5~1.5%; d) The material treated in step c) is aged at 140~150℃ for 8~16h.

2. The heat treatment method according to claim 1, characterized in that, In step a), the heating and heat preservation temperature is 515~520℃.

3. The heat treatment method according to claim 1, characterized in that, In step b), the temperature of the first aging treatment is 80~86℃.

4. The heat treatment method according to claim 1, characterized in that, In step b), the time for the first stage of time-sensitive processing is 20~24h.

5. The heat treatment method according to claim 1, characterized in that, In step b), the temperature for the second aging treatment is 175~180℃.

6. The heat treatment method according to claim 1, characterized in that, In step b), the time for the second stage of aging processing is 2.5 to 3 hours.

7. The heat treatment method according to claim 1, characterized in that, In step c), the temperature range of the deformation heat treatment is 155~180℃.

8. The heat treatment method according to claim 1, characterized in that, In step c), the deformation amount of the deformation heat treatment is 1~1.2%.

9. The heat treatment method according to claim 1, characterized in that, In step d), the aging treatment temperature is 145~150℃.

10. The heat treatment method according to claim 1, characterized in that, In step d), the time for the aging process is 12-15 hours.

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