Preparation method of ultrahigh-strength aluminum alloy forge piece

Abstract

The invention belongs to the technical field of metal forging forming, and particularly relates to a preparation method of an ultrahigh-strength aluminum alloy forge piece, which comprises the following steps: heating an aluminum alloy blank to 440-460 DEG C, cogging by adopting a multi-time upsetting and multi-directional forging mode, and controlling the finish forging temperature to be not lower than 380 DEG C to obtain a forging stock; the forging stock is heated to 270-290 DEG C after being cooled, upsetting is conducted in the longitudinal direction, and the final forging temperature is controlled to be not lower than 200 DEG C; and after the upset blank is cooled, the blank is heated to 465-475 DEG C, heat preservation is conducted, aging treatment is conducted after cooling, and the ultrahigh-strength aluminum alloy forge piece is obtained. The mechanical property of the aluminum alloy forge piece can be improved, and particularly, the strength and the ductility are improved at the same time.

Description

Technical Field

[0001] The invention belongs to the technical field of metal forging and forming, and in particular relates to a method for preparing an ultra-high-strength aluminum alloy forging. Background Art

[0002] Aluminum alloy forgings have low density, high strength, high reliability, good plasticity, strong corrosion resistance, beautiful appearance and durability, and are increasingly becoming the main material for parts in need.

[0003] 7075 aluminum alloy has the characteristics of high specific strength, fatigue resistance, and corrosion resistance, and has become the mainstream material for medical centrifuge rotors at this stage. The traditional 7075 aluminum alloy free forging process is high temperature forging + heat treatment, and the mechanical properties of the prepared forgings are relatively low. With the continuous development of medical and biotechnology, medical centrifuges are developing in the direction of high speed and high precision, which puts higher requirements on the mechanical properties of rotor materials.

[0004] CN101941039A discloses a high-strength aluminum alloy isothermal variable direction free forging method and device, comprising the following steps: the first step: placing the pre-processed high-strength aluminum alloy billet into a variable direction isothermal forging heating and insulation furnace for heating, the heating temperature is 350°C to 450°C, and the furnace temperature is kept unchanged; the second step: according to the required organizational performance index requirements of the billet, the billet is repeatedly upset and stretched in the variable direction isothermal forging heating and insulation furnace until the forging design size is reached; the upset is to deform the billet to 1 / 3 to 1 / 2 of the original height; the stretch is to deform the billet to the height of the original billet. It is to refine the grains and improve the material by controlling the temperature of the forging process to be in 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 the aluminum alloy forgings, especially improving the strength and elongation at the same time.

[0006] The embodiment of the present invention provides a method for preparing an ultra-high strength aluminum alloy forging, comprising the following steps: The aluminum alloy billet is heated to 440-460°C, and the billet is opened by multiple upsetting and multi-directional forging, and the final forging temperature is controlled to be not less than 380°C to obtain a forged billet; After the forging blank is cooled, it is heated to 270-290° C., roughened in the longitudinal direction, and the final forging temperature is controlled to be not less than 200° C.; The roughened blank is cooled, then heated to 465-475° C., kept warm, and subjected to aging treatment after cooling to obtain an ultra-high strength aluminum alloy forging.

[0007] Preferably, the aluminum alloy is 7075 aluminum alloy.

[0008] Preferably, the number of upsetting is four times, and the method of multiple upsetting and multi-directional forging is to perform upsetting once in the longitudinal, transverse and height directions of the aluminum alloy billet, and the single upsetting deformation is 50-60%. The fourth upsetting is in the longitudinal direction, and the upsetting deformation is 30-40%.

[0009] Preferably, the forging blank is heated to 270-290° C. after cooling, and when being upset in the longitudinal direction, the upset deformation amount is 30-40%.

[0010] Preferably, the temperature of the upsetting blank after cooling is room temperature.

[0011] Preferably, the insulation time is 90 to 110 minutes.

[0012] Preferably, the cooling method after heat preservation is water quenching.

[0013] Preferably, the temperature of the aging treatment is 115-125°C.

[0014] Preferably, the holding time of the aging treatment is 650 to 670 minutes.

[0015] The beneficial effect of the present invention is that the present invention improves the forgeability of the blank and avoids forging cracking through high-temperature multi-directional forging, and at the same time can improve the unevenness of the ingot structure, eliminate the cast structure and obtain the deformed structure.

[0016] The present invention adopts a low-temperature forging method for final forming, controls the temperature at 270-290°C, and can achieve high forging permeability of the blank through hardening transfer; at the same time, a high-density dislocation can be introduced to accumulate a large amount of deformation energy storage, which provides energy for the recrystallization of grains in the subsequent solid solution process, thereby refining the grains, achieving fine grain strengthening and improving the mechanical properties of the forging; finally, the high-density dislocation provides heterogeneous nucleation points for the precipitation phase, and the deformation energy storage provides sufficient energy for the heterogeneous nucleation of the precipitation phase, which accelerates the precipitation of the second phase in the subsequent aging process, thereby achieving the second phase strengthening and improving the mechanical properties of the forging.

[0017] The warm forging method of the present invention controls the temperature at about 280° C., which can significantly further refine the grains and improve the degree of recrystallization, thereby improving the tensile strength, yield strength and elongation, compared with upsetting forging at a higher temperature.

[0018] During high-temperature forging, the present invention controls the forging temperature to 450° C. Compared with a higher forging temperature, the structure distribution is relatively uniform and the grain size is relatively fine, which can significantly improve the tensile strength, yield strength and elongation.

[0019] The mechanical properties of aluminum alloy forgings obtained by the method of the present invention were tested, and it was found that the tensile strength of the aluminum alloy forgings obtained by the method of the present invention could reach 620 MaP, the yield strength could reach 520 MPa, and the elongation could reach 16.5%. The present invention can significantly improve the mechanical properties of aluminum alloy forgings. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a microstructure picture of the aluminum alloy forging in Example 1.

[0021] Figure 2 This is the microstructure picture of the aluminum alloy forging of Comparative Example 1.

[0022] Figure 3 This is the microstructure picture of the aluminum alloy forging of Comparative Example 2.

[0023] Figure 4 This is the microstructure picture of the aluminum alloy forging of comparative example 3. DETAILED DESCRIPTION Example 1

[0024] A method for preparing an ultra-high strength aluminum alloy forging comprises the following steps: Step 1: Heat the 7075 aluminum alloy billet to 450±5℃, open the billet by 4-drawing and 4-upsetting multi-directional forging process, perform upsetting in the longitudinal, transverse and height directions of the corresponding billet, and perform upsetting once, 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%, and the final forging temperature is ≥380℃; Step 2: Cool the forging billet to room temperature after the billet is opened, and then heat it to 280±5℃ for low-temperature forging, upset it longitudinally, and the upset deformation is 30% to 40%, and the final forging temperature is ≥200℃; Step 3: Cool the forged billet to room temperature, then heat it to 470±3℃, keep it warm for 100±5min, then water quench it, and then perform aging treatment at 120±3℃ and 660±5min.

[0025] After heat treatment, the mechanical properties of the samples were tested, with tensile strength of 620MaP, yield strength of 520MPa, and elongation of 16.5%. Comparative Example 1

[0026] A method for preparing an aluminum alloy forging comprises the following steps: Step 1: Heat the 7075 aluminum alloy billet to 470±5℃, open the billet by 4-drawing and 4-upsetting multi-directional forging process, perform upsetting in the longitudinal, transverse and height directions of the corresponding billet, and perform upsetting once, 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%, and the final forging temperature is ≥380℃; Step 2: Cool the billet after high temperature deformation to room temperature, then heat it to 470±3℃, keep it warm for 100±5min, then water quench it, and then perform aging treatment. The aging temperature is 120±3℃ and the holding time is 660±5min.

[0027] After heat treatment, the mechanical properties of the samples were tested, with tensile strength of 505MaP, yield strength of 425MPa, and elongation of 10.1%. Comparative Example 2

[0028] A method for preparing an aluminum alloy forging comprises the following steps: Step 1: Heat the 7075 aluminum alloy billet to 450±5℃, open the billet by 4-drawing and 4-upsetting multi-directional forging process, perform upsetting in the longitudinal, transverse and height directions of the corresponding billet, and perform upsetting once, 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%, and the final forging temperature is ≥380℃; Step 2: Cool the billet after high temperature deformation to room temperature, then heat it to 470±3℃, keep it warm for 100±5min, then water quench it, and then perform aging treatment. The aging temperature is 120±3℃ and the holding time is 660±5min.

[0029] After heat treatment, the mechanical properties of the samples were tested, with tensile strength of 530 MaP, yield strength of 452 MPa, and elongation of 11.9%. Comparative Example 3

[0030] A method for preparing an aluminum alloy forging comprises the following steps: Step 1: Heat the 7075 aluminum alloy billet to 450±5℃, open the billet by 4-drawing and 4-upsetting multi-directional forging process, perform upsetting in the longitudinal, transverse and height directions of the corresponding billet, and perform upsetting once, 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%, and the final forging temperature is ≥380℃; Step 2: Cool the forging billet to room temperature, then heat it to 320±5℃ for low temperature forging, upset it longitudinally, and the upset deformation is 30% to 40%, and the final forging temperature is ≥200℃; Step 3: Cool the forged billet to room temperature, then heat it to 470±3℃, keep it warm for 100±5min, then water quench it, and then perform aging treatment at 120±3℃ and 660±5min.

[0031] After heat treatment, the mechanical properties of the samples were tested, with tensile strength of 575 MaP, yield strength of 482 MPa, and elongation of 14.2%.

[0032] A person skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of protection of the present application is limited to these examples. In line with the concept of the present application, the technical features in the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of different aspects of one or more embodiments of the present application as described above, which are not provided in detail for the sake of simplicity.

[0033] One or more embodiments of the present application are intended to cover all such substitutions, modifications and variations that fall within the broad scope of the present application. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of one or more embodiments of the present application should be included in the protection scope of the present application.

Claims

1. A method for preparing an ultra-high strength aluminum alloy forging, characterized in that: The steps include: The aluminum alloy billet is heated to 440-460°C, and the billet is opened by multiple upsetting and multi-directional forging, and the final forging temperature is controlled to be not less than 380°C to obtain a forged billet; After the forging blank is cooled, it is heated to 270-290° C., roughened in the longitudinal direction, and the final forging temperature is controlled to be not less than 200° C.; The roughened blank is cooled, then heated to 465-475° C., kept warm, and subjected to aging treatment after cooling to obtain an ultra-high strength aluminum alloy forging.

2. The preparation method according to claim 1, characterized in that: The aluminum alloy is 7075 aluminum alloy.

3. The preparation method according to claim 1, characterized in that: The upsetting is performed four times. The method of multiple upsetting and multi-directional forging is to perform upsetting once in the longitudinal, transverse and height directions of the aluminum alloy billet, and the single upsetting deformation is 50-60%. The fourth upsetting is in the longitudinal direction, and the upsetting deformation is 30-40%.

4. The preparation method according to claim 1, characterized in that: The forging blank is cooled and heated to 270-290° C., and when it is upset in the longitudinal direction, the upset deformation amount is 30-40%.

5. The preparation method according to claim 1, characterized in that: The temperature of the upset blank after cooling is room temperature.

6. The preparation method according to claim 1, characterized in that: The insulation time is 90 to 110 minutes.

7. The preparation method according to claim 1, characterized in that: The cooling method after insulation is water quenching.

8. The preparation method according to any one of claims 1 to 7, characterized in that: The temperature of aging treatment is 115-125°C.

9. The preparation method according to claim 8, characterized in that: The holding time for aging treatment is 650-670 minutes.

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