A method of heat treating an extrusion of a high strength aluminum alloy

Abstract

This invention discloses a method for heat-treated extrusion molding of high-strength aluminum alloy, comprising: S1: annealing the high-strength aluminum alloy raw material; S2: heating the annealed aluminum alloy raw material to 450-500℃ for solution treatment, followed by water quenching; S3: storing the high-strength aluminum alloy raw material at -18℃ for 30-360 days; S4: restoring the temperature of the high-strength aluminum alloy raw material to 10-30℃, followed by cold working or cold extrusion molding; S5: artificially aging the high-strength aluminum alloy raw material within 24 hours after cold working or cold extrusion. By first annealing the high-strength aluminum alloy raw material, the crystal structure is fully optimized, significantly improving the uniformity and stability of the material structure; then performing solution treatment and water quenching, followed by refrigerating the material in a -18℃ low-temperature environment, the natural aging of the quenched metastable structure at room temperature is effectively suppressed, allowing the solution-treated material to be stored at low temperatures for a long time, with its physicochemical properties remaining basically stable within one year. After the temperature is restored to 10-30℃, cold working or cold extrusion molding is performed. At this time, the material still retains good plasticity and the cold working capacity is greatly improved. The cold deformation amount of high-strength aluminum alloys such as 7075 can be increased from 5%-10% in the traditional process to more than 20%.

Description

Technical Field

[0001] This invention relates to the field of heat treatment technology for high-strength aluminum alloys, and in particular to a heat treatment extrusion molding method for high-strength aluminum alloys. Background Technology

[0002] High-strength aluminum alloys belong to the Al-Zn-Mg-Cu system of heat-treatable aluminum alloys. They have high strength, high specific strength, and good fatigue properties, and are widely used in aerospace, rail transportation, automotive lightweighting, and military equipment.

[0003] Currently, the following problems exist in the actual manufacturing process of 7-series high-strength aluminum alloys: (1) Insufficient cold working deformation capacity Due to the high strength and poor plasticity of aluminum alloys, the allowable deformation during cold working under normal conditions is typically only 5% to 10%. Exceeding this range can easily lead to problems such as: 1. cracking; 2. stress concentration; 3. grain damage; 4. dimensional instability; and 5. severe work hardening. Traditional processes are difficult to achieve large deformation cold extrusion processing.

[0004] (2) Hot working can easily cause changes in microstructure. Aluminum alloys are highly sensitive to temperature and are prone to the following during hot working: 1. precipitate phase changes; 2. grain coarsening; 3. microstructure inhomogeneity; 4. failure of strengthening phases. These factors can negatively impact the strength and stability of the final product.

[0005] (3) It is easy to age naturally after solution treatment. High-strength aluminum alloys are in a metastable state after solution cooling and water quenching, and undergo natural aging at room temperature. Over time, GP zones and precipitates gradually form within the material, reducing its plasticity and deteriorating its processing performance, thus increasing the difficulty of subsequent cold working. Therefore, existing technologies struggle to simultaneously achieve: 1. large deformation cold working capability; 2. high strength performance; 3. microstructure stability; and 4. process controllability.

[0006] The existing high-strength aluminum alloy processing technology has the following main defects: Therefore, a high-strength aluminum alloy heat treatment extrusion molding method is still needed to solve the above problems. Summary of the Invention

[0007] This invention provides a high-strength aluminum alloy heat treatment extrusion molding method to solve the above problems.

[0008] The objective of this invention is achieved through the following technical solution: A method for heat-treated extrusion forming of high-strength aluminum alloy, comprising: S1: Annealing high-strength aluminum alloy raw materials; S2: The annealed aluminum alloy raw material is heated to 450-500℃ for solution treatment, and then water-quenched. S3: Store the high-strength aluminum alloy raw material at -18°C for 30-360 days; S4: Restore the temperature of the high-strength aluminum alloy raw material to 10-30℃, and then cold work or cold extrusion molding; S5: Artificial aging is performed within 24 hours after the high-strength aluminum alloy raw material is cold-worked or cold-extruded.

[0009] In one embodiment, the annealing treatment of the high-strength aluminum alloy raw material includes: The high-strength aluminum alloy raw material is heated to 350-400℃, annealed, and held at that temperature for 1-6 hours.

[0010] In one embodiment, the total deformation of the cold working or cold extrusion molding is 20-30%.

[0011] In one embodiment, the temperature for artificial aging is 200-250°C, and the holding time is 6-10 hours.

[0012] Compared with the prior art, the beneficial effects of the present invention include at least the following: This invention first anneales the high-strength aluminum alloy raw material, fully optimizing the crystal structure and significantly improving the uniformity and stability of the material's microstructure. Next, it performs solution treatment and water quenching, followed by refrigeration at -18°C. This effectively suppresses the natural aging of the metastable quenched microstructure at room temperature, allowing the solution-treated material to be stored at low temperatures for extended periods, with its physicochemical properties remaining largely stable for up to one year. After recovering to 10–30°C, cold working or cold extrusion is performed. At this point, the material retains good plasticity, significantly improving its cold working capacity. The cold deformation of high-strength aluminum alloys such as 7075 can be increased from 5%–10% in traditional processes to over 20%. Artificial aging is performed within 24 hours after forming, causing stable strengthening phases to precipitate uniformly in the supersaturated solid solution, thereby effectively improving the product's strength and fatigue performance. Attached Figure Description

[0013] Figure 1 This is a flowchart of a high-strength aluminum alloy heat treatment extrusion molding method according to an embodiment of the present invention. Detailed Implementation

[0014] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the embodiments set forth herein; rather, they are provided to make the invention more comprehensive and complete, and to fully convey the concept of the exemplary embodiments to those skilled in the art. The same reference numerals in the drawings denote the same or similar structures, and therefore repeated descriptions of them will be omitted.

[0015] The terms used to express position and direction in this invention are illustrated with reference to the accompanying drawings, but changes can be made as needed, and all such changes are included within the scope of protection of this invention.

[0016] This invention provides a method for heat-treated extrusion forming of high-strength aluminum alloy, comprising: S1: Annealing treatment of high-strength aluminum alloy raw materials; including: High-strength aluminum alloy raw materials are heated to 350-400℃ for annealing and held at that temperature for 1-6 hours. Full annealing adjusts the crystal structure, eliminates internal residual stress, improves microstructure uniformity, and enhances the stability of subsequent solution treatment. After annealing, the material is cooled naturally or slowly.

[0017] S2: The annealed aluminum alloy raw material is heated to 450-500℃ for solution treatment, followed by water quenching. Through solution treatment, strengthening elements such as Zn, Mg, and Cu are fully dissolved in the aluminum matrix, resulting in a metastable structure. After this step, the allowable deformation during cold working can reach over 20%.

[0018] S3: The high-strength aluminum alloy raw material is stored at -18°C for 30-360 days. Through solution treatment, strengthening elements such as Zn, Mg, and Cu are fully dissolved in the aluminum matrix, resulting in a metastable structure. Low-temperature storage inhibits natural aging and precipitation phase transformation at room temperature. Under low-temperature conditions, the material's physical and chemical properties remain stable for up to one year.

[0019] S4: The temperature of the high-strength aluminum alloy raw material is restored to 10-30℃, followed by cold working or cold extrusion molding. Before processing, the aluminum alloy material stored at low temperature is restored to room temperature. Then, cold working or cold extrusion molding is performed. The total deformation during cold working is 20%–30%. Under these process conditions, the material still exhibits good plasticity and processing stability.

[0020] S5: Artificial aging is performed within 24 hours after the high-strength aluminum alloy raw material is cold-worked or cold-extruded. The holding time is 6-10 hours. During the artificial aging process, a uniform strengthening precipitate is formed, thereby improving the material strength and microstructure stability. The high-strength aluminum alloy raw material is, for example, 7075, 7050, 7085, 7475, etc., with 7075 aluminum alloy being preferred.

[0021] Example 1 7075 aluminum alloy wire was heated to 380℃ for full annealing and held at that temperature for 4 hours before slow cooling in the furnace. The annealed material was then heated to 480℃ for solution heat treatment and held for 2 hours. Immediately after solution treatment, the material was water-cooled and then stored in a -20℃ environment. After 30 days of storage, the material was removed and brought to room temperature. Cold extrusion was then performed, achieving a cold deformation of 20%. Within 8 hours of processing, the product was placed in a 220℃ environment for 8 hours of artificial aging treatment.

[0022] In this embodiment, no obvious cracking occurred during the cold working of the material, the cold deformation capacity was significantly improved, the product structure was uniform, and the finished product had high strength and stability.

[0023] Example 2 The 7075 aluminum alloy wire was fully annealed at 350℃ and held at that temperature for 6 hours before slow cooling. The material was then heated to 450℃ for solution treatment, held for 1.5 hours, and immediately water-cooled after solution treatment. The material was then refrigerated at -18℃. After 90 days of storage, it was brought back to room temperature and cold-stamped, achieving a cold deformation of 18%. Within 24 hours of the cold working, it underwent artificial aging treatment at 200℃ for 10 hours.

[0024] In this embodiment, the material has good plasticity, no edge cracks occurred during the stamping process, and the product has good hardness and dimensional stability, making it suitable for forming complex structural parts.

[0025] Example 3 The 7075 aluminum alloy wire was fully annealed at 400℃ and held at that temperature for 3 hours before slow cooling. The material was then heated to 500℃ for solution treatment, held for 1 hour, and immediately water-cooled after solution treatment. The material was then refrigerated at -25℃. After 180 days of storage, it was brought back to room temperature and cold-stamped, achieving a cold deformation of 22%. Within 12 hours of the cold working, it underwent artificial aging treatment at 230℃ for 6 hours.

[0026] In this embodiment, the material retains good plasticity, with no obvious cracks during large deformation processing, significantly improved tensile strength, and excellent structural stability after aging.

[0027] Example 4 The 7075 aluminum alloy wire was fully annealed at 370℃ and held at that temperature for 5 hours before slow cooling. The material was then heated to 470℃ for solution treatment, held for 2.5 hours, and immediately water-cooled after solution treatment. The material was then refrigerated at -30℃. After 360 days of storage, it was brought back to room temperature and cold-stamped, achieving a cold deformation of 20%. Within 6 hours of the cold working, it underwent artificial aging treatment at 250℃ for 6 hours.

[0028] In this embodiment, the material's physical and chemical properties change little after long-term storage, and it can still maintain high cold working ability. The product has good strength and fatigue resistance, and high product consistency.

[0029] Comparative Example 1 (Conventional Process) 7075 aluminum alloy wire is selected without full annealing and directly subjected to conventional solution heat treatment. After solution treatment, it is stored at room temperature for 7 days and then cold-worked. After cold working, conventional aging treatment is performed.

[0030] In this comparative example, the material underwent significant natural aging at room temperature, resulting in a marked decrease in plasticity. Cracks were prone to appear after the cold deformation exceeded 10%, the product had poor microstructure uniformity, and the finished product had insufficient strength stability.

[0031] Comparative Example 2 (without cryogenic storage process) 7075 aluminum alloy wire is selected and subjected to full annealing and solution heat treatment. After solution treatment, it is not stored at low temperature, but placed at room temperature for 30 days before cold working, followed by artificial aging treatment.

[0032] In this comparative example, the material undergoes significant natural aging, resulting in decreased cold working plasticity and a cold deformation amount of only about 8%-10%. Microcracks are easily generated during large deformation processing, and the product performance is lower than that of the embodiments of the present invention.

[0033] Comparative Example 3 (without full annealing process) 7075 aluminum alloy wire is selected without full annealing, and is directly subjected to solution treatment and low-temperature storage, followed by cold working and aging treatment.

[0034] In this comparative example, the material has poor internal structure uniformity, local stress concentration during cold working, and is prone to local cracking. The product has poor dimensional stability, and the overall performance of the finished product is lower than that of this invention.

[0035] Experimental verification shows that the embodiment of this invention, through the combined process of full annealing + solution cooling + low-temperature storage + large deformation cold working + artificial aging, achieves the following: 1. Effectively suppresses natural aging of 7075 aluminum alloy. 2. Significantly improves cold working plasticity. 3. Achieves a cold deformation amount of over 20%. 4. Reduces the risk of processing cracks. 5. Improves product strength and microstructure stability. 6. Significantly superior to existing traditional processes.

[0036] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the invention without departing from the principles and spirit of the invention, and all such changes should fall within the protection scope of the claims of the present invention.

Claims

1. A method for heat-treating and extruding high-strength aluminum alloy, characterized in that, include: S1: Annealing high-strength aluminum alloy raw materials; S2: The annealed aluminum alloy raw material is heated to 450-500℃ for solution treatment, and then water-quenched. S3: Store the high-strength aluminum alloy raw material at -18°C for 30-360 days; S4: Restore the temperature of the high-strength aluminum alloy raw material to 10-30℃, and then cold work or cold extrusion molding; S5: Artificial aging is performed within 24 hours after the high-strength aluminum alloy raw material is cold-worked or cold-extruded.

2. The high-strength aluminum alloy heat treatment extrusion forming method according to claim 1, characterized in that, The annealing treatment of the high-strength aluminum alloy raw material includes: The high-strength aluminum alloy raw material is heated to 350-400℃, annealed, and held at that temperature for 1-6 hours.

3. The high-strength aluminum alloy heat treatment extrusion forming method according to claim 1, characterized in that, The total deformation of the cold working or cold extrusion molding is 20-30%.

4. The high-strength aluminum alloy heat treatment extrusion forming method according to claim 1, characterized in that, The temperature for artificial aging is 200-250℃, and the holding time is 6-10 hours.

5. The high-strength aluminum alloy heat treatment extrusion forming method according to claim 1, characterized in that, S1 includes: The high-strength aluminum alloy raw material is annealed at 350-400℃ and held for 1-6 hours.

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