A method for producing an ultra-high strength aluminum alloy forging

Abstract

This invention belongs to the field of metal forging technology, specifically relating to a method for preparing ultra-high strength aluminum alloy forgings, comprising the following steps: heating an aluminum alloy billet to 440-460°C, performing multiple upsetting and multi-directional forging to open the billet, controlling the final forging temperature not lower than 380°C, to obtain a forging billet; after cooling, the forging billet is heated to 270-290°C and longitudinally upsetting, controlling the final forging temperature not lower than 200°C; after cooling the upset billet, it is then heated to 465-475°C, held at that temperature, and after cooling, subjected to aging treatment to obtain ultra-high strength aluminum alloy forgings; this invention can improve the mechanical properties of aluminum alloy forgings, especially simultaneously improving strength and elongation.

Description

Technical Field

[0001] This invention belongs to the field of metal forging and forming technology, and specifically relates to a method for preparing ultra-high strength aluminum alloy forgings. Background Technology

[0002] Aluminum alloy forgings have low density, high strength, high reliability, good plasticity, strong corrosion resistance, and are aesthetically pleasing and durable, making them an increasingly important material for components.

[0003] 7075 aluminum alloy, with its high specific strength, fatigue resistance, and corrosion resistance, has become the mainstream material for medical centrifuge rotors. Traditional free forging processes for 7075 aluminum alloy involve high-temperature forging followed by heat treatment, resulting in forgings with relatively low mechanical properties. With the continuous development of medical and biotechnology, medical centrifuges are evolving towards higher speeds and precision, thus placing higher demands on the mechanical properties of rotor materials.

[0004] CN101941039A discloses a method and apparatus for isothermal free forging of high-strength aluminum alloys, comprising the following steps: Step 1: A pre-processed high-strength aluminum alloy billet is placed in a variable-temperature isothermal forging heating and holding furnace and heated to 350℃~450℃, maintaining a constant furnace temperature; Step 2: According to the required microstructure and performance indicators of the billet, the billet is repeatedly upset and drawn within the variable-temperature isothermal forging heating and holding furnace until the designed dimensions of the forging are achieved; Upsetting involves deforming the billet to 1 / 3 to 1 / 2 of its original height; drawing involves deforming the billet to its original height. This method refines the grains and improves material quality by controlling the forging process under isothermal conditions. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for preparing ultra-high strength aluminum alloy forgings, thereby improving the mechanical properties of aluminum alloy forgings, especially by simultaneously improving strength and elongation.

[0006] This invention provides a method for preparing ultra-high strength aluminum alloy forgings, comprising the following steps:

[0007] The aluminum alloy billet is heated to 440-460℃ and then forged by multiple upsetting and multi-directional forging. The final forging temperature is controlled to be no less than 380℃ to obtain the forged billet.

[0008] After cooling, the forging billet is heated to 270-290°C and then uplifted longitudinally, with the final forging temperature controlled to be no less than 200°C.

[0009] After the upsetting billet is cooled, it is heated to 465-475°C, held at that temperature, cooled again, and then subjected to aging treatment to obtain an ultra-high strength aluminum alloy forging.

[0010] Preferably, the aluminum alloy is 7075 aluminum alloy.

[0011] Preferably, the upsetting and drawing process is performed four times. The multi-upsetting and multi-directional forging method involves upsetting and drawing once in each of the three directions of the aluminum alloy billet: longitudinal, transverse and vertical. The upsetting deformation in a single upsetting operation is 50-60%. The fourth upsetting operation is performed in the longitudinal direction, with an upsetting deformation of 30-40%.

[0012] Preferably, when the forging billet is heated to 270-290°C after cooling and then upsetting along the longitudinal direction, the upsetting deformation is 30-40%.

[0013] Preferably, the temperature of the upsetting billet after cooling is room temperature.

[0014] Preferably, the heat preservation time is 90–110 minutes.

[0015] Preferably, the cooling method after heat preservation is water quenching.

[0016] Preferably, the aging treatment temperature is 115–125°C.

[0017] Preferably, the holding time for aging treatment is 650–670 min.

[0018] The beneficial effects of this invention are that it improves the forgeability of the billet and avoids forging cracks by high-temperature multi-directional forging. At the same time, it can improve the inhomogeneity of the ingot structure and eliminate the as-cast structure to obtain the deformed structure.

[0019] This invention employs a low-temperature forging method with final forming, controlling the temperature between 270 and 290°C. High forging penetration of the billet can be achieved through hardening transfer. Simultaneously, a high density of dislocations can be introduced, accumulating a large amount of deformation energy. This provides energy for grain recrystallization during subsequent solid solution treatment, thereby refining the grains and achieving fine-grain strengthening to improve the mechanical properties of the forging. Finally, the high density of dislocations provides heterogeneous nucleation sites for the precipitates, and the deformation energy provides sufficient energy for the heterogeneous nucleation of the precipitates, accelerating the precipitation of the second phase during subsequent aging, thus achieving second-phase strengthening to improve the mechanical properties of the forging.

[0020] The warm forging method of the present invention controls the temperature at around 280°C. Compared with upsetting forging at higher temperatures, it can significantly further refine the grains and improve the degree of recrystallization, thereby improving tensile strength, yield strength and elongation.

[0021] In this invention, the forging temperature is controlled to 450°C during high-temperature forging. Compared with higher forging temperatures, the microstructure distribution is relatively uniform and the grain size is relatively fine, which can significantly improve tensile strength, yield strength and elongation.

[0022] Mechanical property tests were conducted on aluminum alloy forging samples obtained using the method of this invention. The results showed that the tensile strength of the aluminum alloy forgings obtained using this method can reach 620 MPa, the yield strength can reach 520 MPa, and the elongation can reach 16.5%. This invention can significantly improve the mechanical properties of aluminum alloy forgings. Attached Figure Description

[0023] Figure 1 The image shows the microstructure of the aluminum alloy forging from Example 1.

[0024] Figure 2 The image shows the microstructure of the aluminum alloy forging in Comparative Example 1.

[0025] Figure 3 The image shows the microstructure of the aluminum alloy forging in Comparative Example 2.

[0026] Figure 4 The image shows the microstructure of the aluminum alloy forging in Comparative Example 3. Detailed Implementation Example 1

[0027] A method for preparing ultra-high strength aluminum alloy forgings includes the following steps:

[0028] Step 1: Heat the 7075 aluminum alloy billet to 450±5℃ and use a 4-drawing and 4-upsetting multi-directional forging process to open the billet. Upset and draw once in each of the longitudinal, transverse and vertical directions of the corresponding billet, with a single upsetting deformation of 50% to 60%. The fourth upsetting is in the longitudinal direction, with an upsetting deformation of 30% to 40%. The final forging temperature is ≥380℃.

[0029] Step 2: Cool the forged billet after the blanking process to room temperature, then heat it to 280±5℃ for low-temperature forging, upsetting along the longitudinal direction, with an upsetting deformation of 30% to 40%, and a final forging temperature of ≥200℃;

[0030] Step 3: Cool the forged billet to room temperature, then heat it to 470±3℃ and hold it for 100±5 min, then quench it in water, and then perform an aging treatment at 120±3℃ for 660±5 min.

[0031] After heat treatment, the mechanical properties of the sample were tested. The tensile strength was 620 MPa, the yield strength was 520 MPa, and the elongation was 16.5%. Comparative Example 1

[0032] A method for preparing an aluminum alloy forging includes the following steps:

[0033] Step 1: Heat the 7075 aluminum alloy billet to 470±5℃ and use a 4-drawing and 4-upsetting multi-directional forging process to open the billet. Upset and draw once in each of the longitudinal, transverse and vertical directions of the corresponding billet, with a single upsetting deformation of 50% to 60%. The fourth upsetting is in the longitudinal direction, with an upsetting deformation of 50% to 60%. The final forging temperature is ≥380℃.

[0034] Step 2: Cool the high-temperature deformed billet to room temperature, then heat it to 470±3℃ and hold it for 100±5 min, then quench it in water, and then perform an aging treatment at a temperature of 120±3℃ for 660±5 min.

[0035] After heat treatment, the mechanical properties of the sample were tested. The tensile strength was 505 MPa, the yield strength was 425 MPa, and the elongation was 10.1%. Comparative Example 2

[0036] A method for preparing an aluminum alloy forging includes the following steps:

[0037] Step 1: Heat the 7075 aluminum alloy billet to 450±5℃, and use a 4-drawing and 4-upsetting multi-directional forging process to open the billet. Upset and draw once in each of the longitudinal, transverse and height directions of the corresponding billet, with a single upsetting deformation of 50% to 60%. The fourth upsetting is in the longitudinal direction, with an upsetting deformation of 50% to 60%. The final forging temperature is ≥380℃.

[0038] Step 2: Cool the high-temperature deformed billet to room temperature, then heat it to 470±3℃ and hold it for 100±5 min, then quench it in water, and then perform an aging treatment at a temperature of 120±3℃ for 660±5 min.

[0039] After heat treatment, the mechanical properties of the sample were tested. The tensile strength was 530 MPa, the yield strength was 452 MPa, and the elongation was 11.9%. Comparative Example 3

[0040] A method for preparing an aluminum alloy forging includes the following steps:

[0041] Step 1: Heat the 7075 aluminum alloy billet to 450±5℃ and use a 4-drawing and 4-upsetting multi-directional forging process to open the billet. Upset and draw once in each of the longitudinal, transverse and vertical directions of the corresponding billet, with a single upsetting deformation of 50% to 60%. The fourth upsetting is in the longitudinal direction, with an upsetting deformation of 30% to 40%. The final forging temperature is ≥380℃.

[0042] Step 2: Cool the forged billet to room temperature after opening, and then heat it to 320±5℃ for low-temperature forging, upsetting along the longitudinal direction, with an upsetting deformation of 30% to 40%, and a final forging temperature of ≥200℃;

[0043] Step 3: Cool the forged billet to room temperature, then heat it to 470±3℃ and hold it for 100±5 min, then quench it in water, and then perform an aging treatment at 120±3℃ for 660±5 min.

[0044] After heat treatment, the mechanical properties of the sample were tested. The tensile strength was 575 MPa, the yield strength was 482 MPa, and the elongation was 14.2%.

[0045] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of protection of this application is limited to these examples; under the concept of this application, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of different aspects of one or more embodiments of this application as described above, which are not provided in detail for the sake of brevity.

[0046] One or more embodiments in this application are intended to cover all such substitutions, modifications, and variations that fall within the broad scope of this application. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of one or more embodiments in this application should be included within the protection scope of this application.

Claims

1. A method for preparing ultra-high strength aluminum alloy forgings, characterized in that, Includes the following steps: The aluminum alloy billet is heated to 440-460℃ and then forged by multiple upsetting and multi-directional forging. The final forging temperature is controlled to be no less than 380℃ to obtain the forged billet. After cooling, the forging billet is heated to 270-290°C and upset longitudinally. The upsetting deformation is 30-40%, and the final forging temperature is controlled to be no less than 200°C. After the upsetting billet is cooled to room temperature, it is then heated to 465-475°C, held at that temperature, cooled, and then subjected to aging treatment to obtain an ultra-high strength aluminum alloy forging; the cooling method after holding is water quenching. The aluminum alloy is 7075 aluminum alloy; The upsetting and drawing process is carried out four times. The multi-upsetting and multi-directional forging method involves upsetting and drawing once in each of the three directions of the aluminum alloy billet: longitudinal, transverse and vertical. The upsetting deformation in a single upsetting is 50-60%. The fourth upsetting is carried out in the longitudinal direction, and the upsetting deformation is 30-40%.

2. The preparation method according to claim 1, characterized in that, The heat preservation time is 90-110 minutes.

3. The preparation method according to claim 1 or 2, characterized in that, The aging treatment temperature is 115–125℃.

4. The preparation method according to claim 3, characterized in that, The holding time for aging treatment is 650–670 min.

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