A method for preparing high-strength aluminum alloy forgings

Abstract

The present invention provides a method for preparing a high-strength aluminum alloy forging, comprising: subjecting aluminum powder and alloy powder to high-energy ball milling to obtain a mixed powder; subjecting the mixed powder to isostatic pressing to obtain a preform; and subjecting the preform to forging and sintering after preheating to obtain a high-strength aluminum alloy forging. The present invention uses powder forging technology to complete the rapid sintering of ultrafine aluminum alloy powder under pressure and the metal fluid deformation, flow and mold filling process, and simultaneously realizes the powder sintering and sintered body forging deformation, and finally obtains an aluminum alloy forging with high density and high mechanical properties.

Description

Technical Field

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

[0002] As my country's transportation industry develops towards modernization and high speed, the demand for lightweight transportation vehicles is becoming stronger and stronger, and the call for replacing steel with aluminum is getting louder and louder. Especially in the lightweight process of passenger cars and trucks, the use of aluminum forgings in parts such as wheels, chassis components, safety and suspension systems has shown a significant growth trend. Deformed aluminum alloys have high plasticity and low deformation resistance. The blanks will undergo obvious plastic deformation and macroscopic metal flow under pressure, which is very suitable for forging technology. The masterbatch suitable for forging production is generally ingots and extruded rods, that is, "ingots + forging" and "extruded rods + forging". Through the forging process, a large amount of plastic flow can be achieved to eliminate columnar crystals and coarse grains, thereby improving mechanical properties. Commonly used are 2 series, 6 series and 7 series alloys. Due to its low density, high specific strength and specific stiffness, aluminum alloy forgings have become an indispensable material for mechanical parts in various industrial sectors, and its usage is increasing, and its application field is also expanding.

[0003] With the development of material preparation technology and the continuous pursuit of high alloy indicators by modern industry, a new type of high mechanical performance forging production technology has gradually developed - powder forging technology. Powder forging is a process technology that combines powder metallurgy and precision die forging, with powder metallurgy sintered body as the masterbatch, that is, "sintered body + forging". It uses metal powder as raw material, and after cold pressing, sintering, closed die forging and later heat treatment, it can obtain forging products with uniform internal structure, high dimensional accuracy and excellent mechanical properties. The powder forging process has the advantages of both powder metallurgy and forging, and can produce forgings with a density close to the theoretical density, overcoming the disadvantage of low density of ordinary powder metallurgy parts, making the mechanical properties of powder forgings exceed the level of ordinary forgings, while maintaining the advantages of ordinary powder metallurgy with less and no cutting industry. This process is mainly used for the research and production of iron-based parts.

[0004] Since the powder metallurgy process of aluminum alloys will cause severe oxidation, which makes the alloy brittle, there are few studies on the use of powder metallurgy to prepare aluminum alloy products. Therefore, there are also fewer studies on forgings obtained by continuing forging on the basis of powder metallurgy aluminum alloys. Moreover, the "sintered body + forging" powder forging process involves more process steps and a more complicated process flow. Therefore, further optimization on the basis of the powder forging process, simplification of the process flow, and improvement of material properties are of great significance and role in promoting the large-scale application and industrialization of this process in the field of aluminum alloys. Summary of the invention

[0005] In view of this, an object of the present invention is to provide a method for preparing high-strength aluminum alloy forgings. The method provided by the present invention has a simple process and the prepared forgings have good product performance.

[0006] The present invention provides a method for preparing a high-strength aluminum alloy forging, comprising:

[0007] The aluminum powder and the alloy powder are subjected to high-energy ball milling to obtain a mixed powder;

[0008] isostatically pressing the mixed powder to obtain a preform;

[0009] The preform is preheated and then forged and sintered to obtain a high-strength aluminum alloy forging.

[0010] Preferably, the alloy powder comprises one or more of Mg, Cu, Si and Zr.

[0011] Preferably, the ingredients of the mixed powder are:

[0012] 0-3 wt% Mg;

[0013] 0-3wt% Cu;

[0014] 0-0.5wt% Si;

[0015] 0-0.5wt% Zr;

[0016] The balance is Al.

[0017] Preferably, the high-energy ball milling time is 30 to 50 hours.

[0018] Preferably, the ball-to-material ratio of the high-energy ball mill is (8-12):1.

[0019] Preferably, the average grain size of the mixed powder is 180-400 nm.

[0020] Preferably, the isostatic pressing pressure is 200-300 MPa, and the isostatic pressing time is 2-4 min.

[0021] Preferably, the preheating temperature is 580-640° C., and the preheating time is 2-5 minutes.

[0022] Preferably, the forging and sintering is carried out in a forging die; the temperature of the forging die during the forging and sintering process is 320-360°C.

[0023] Preferably, the forging and sintering method comprises:

[0024] First, perform one-stage pressurization and then two-stage pressurization;

[0025] The speed of the pressurization stage is 0.5-0.6 mm / s;

[0026] The speed of the second stage pressurization is 10-12 mm / s.

[0027] The present invention adopts a powder forging process to prepare high-strength aluminum alloy forgings. First, ultrafine aluminum alloy powder with a clean surface and high activity is prepared; then the ultrafine aluminum alloy powder is rapidly sintered and forged by powder forging technology. The present invention adopts high-energy ball milling technology, and prepares ultrafine aluminum alloy powder with a clean surface and high activity by regulating the ball milling powder making process and process control agent. Due to the effect of the process control agent, the activity and cleanliness generated on the surface of the ultrafine aluminum alloy powder can be temporarily protected, solving the technical difficulties of preparing, storing and transporting ultrafine and highly active aluminum alloy powder in an air environment, and providing basic conditions for the next step of rapid sintering and forging deformation. The present invention uses powder forging technology to complete the rapid sintering of ultrafine aluminum alloy powder under pressure and the metal fluid deformation, flow and mold filling process, and simultaneously realizes powder sintering and sintered body forging deformation, and finally obtains aluminum alloy forgings with high density and high mechanical properties, while conventional powder forging products must be sintered separately for a long time in advance before subsequent forging. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a process flow chart of forging after sintering powder in the prior art;

[0029] Figure 2 It is a process flow chart of powder forging in the present invention;

[0030] Figure 3 This is the TEM image of the forging product prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0031] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] The present invention provides a method for preparing a high-strength aluminum alloy forging, comprising:

[0033] The aluminum powder and the alloy powder are subjected to high-energy ball milling to obtain a mixed powder;

[0034] isostatically pressing the mixed powder to obtain a preform;

[0035] The preform is preheated and then forged and sintered to obtain a high-strength aluminum alloy forging.

[0036] In the present invention, the alloy powder is preferably composed of one or more of Mg, Cu, Si and Zr.

[0037] In the present invention, the ingredients of the mixed powder are preferably:

[0038] 0-3 wt% Mg;

[0039] 0-3wt% Cu;

[0040] 0-0.5wt% Si;

[0041] 0-0.5wt% Zr;

[0042] The balance is Al.

[0043] In the present invention, the mass content of Mg is preferably 0.5-2.5%, more preferably 1-2.0%, most preferably 1.5%; the mass content of Cu is preferably 0.5-2.5%, more preferably 1-2.0%, most preferably 1.5%; the mass content of Si is preferably 0.1-0.4%, more preferably 0.2-0.3%; the mass content of Zr is preferably 0.1-0.4%, more preferably 0.2-0.3%.

[0044] In the present invention, the high energy ball milling time is preferably 30 to 50 hours, more preferably 35 to 45 hours, and most preferably 40 hours; the ball-to-material ratio of the high energy ball milling is preferably (8 to 12):1, more preferably (9 to 11):1, and most preferably 10:1.

[0045] In the present invention, the amplitude of the steel ball in the high-energy ball milling process is preferably 4-6 mm, more preferably 5 mm; the vibration frequency is preferably 1450-1490 cpm, more preferably 1460-1480 cpm, and most preferably 1470 cpm; a mixture (anti-forging agent) is preferably added during the high-energy ball milling process, and the mixture preferably includes acetone and kerosene, and the kerosene is preferably aviation kerosene; the volume ratio of the acetone to the kerosene is preferably (20-24): (1-4), more preferably (21-23): (2-3), and most preferably 22: 2.5; the dosage ratio of the mixed powder and acetone is preferably 1000 g: (20-24) ml, more preferably 1000 g: (21-23) ml, and most preferably 1000 g: 22 ml.

[0046] In the present invention, the average grain size of the mixed powder is preferably 180 to 400 nm, more preferably 250 to 350 nm, and most preferably 300 nm.

[0047] In the present invention, the isostatic pressing is preferably cold isostatic pressing; the isostatic pressing pressure is preferably 200-300 MPa, more preferably 230-270 MPa, and most preferably 250 MPa; the isostatic pressing time is preferably 2-4 min, more preferably 2.5-3.5 min, and most preferably 3 min.

[0048] In the present invention, the preheating temperature is preferably 580-640°C, more preferably 590-630°C, more preferably 600-620°C, and most preferably 610°C; the preheating time is preferably 2-5 minutes, more preferably 3-4 minutes.

[0049] In the present invention, the forging and sintering is preferably carried out in a forging die; the temperature of the forging die during the forging and sintering process is preferably 320-360°C, more preferably 330-350°C, and most preferably 340°C.

[0050] In the present invention, the forging and sintering preferably includes:

[0051] First perform the first stage of pressurization and then the second stage of pressurization.

[0052] In the present invention, the first stage is the initial forging, the speed of the first stage pressurization is preferably 0.5-0.6 mm / s, more preferably 0.55 mm / s; the pressure of the first stage pressurization is preferably 100-200 T, more preferably 150 T; the forging ratio is preferably (1.8-2.2):1, more preferably 2:1;

[0053] In the present invention, when the height of the forging obtained by the initial forging (one-stage pressurization) reaches 45-56% of the height of the preform, preferably 50%, the process is switched to the second stage, and the second stage is the final forging. The speed of the second stage pressurization is preferably 10-12 mm / s, and more preferably 11 mm / s; the pressure of the second stage pressurization is preferably 400-750T, more preferably 500-700T, and most preferably 600T; the forging ratio of the second stage pressurization is preferably (1.1-1.5):1, and more preferably 1.2:1.

[0054] The present invention adopts a one-step process of "forging and sintering" under pressure to replace the multi-step process in the existing powder forging process, such as Figure 2As shown; compared with the prior art, the present invention utilizes a high-energy dry ball milling process, and under the collision of high-energy grinding ball media, the powders of each component are repeatedly cold welded and fractured to form refined composite particles, and a solid-state diffusion reaction occurs, so that the atoms of trace alloy elements enter the lattice of metal aluminum to obtain fine and uniform aluminum alloy solid solution composite powder, and the gaseous molecules of the added process control agent are wrapped on the surface of the ultrafine and highly active powder in the process, which plays a role in blocking oxygen and protecting surface activity; the powder is then pressurized by isostatic pressing to obtain a uniform blank with a density of about 80%; then the blank is preheated to release the gas wrapped on the surface of the particles and re-expose the ultrafine and highly active surface; finally, the powder particles with a highly active surface in the blank are quickly sintered through a rapid sintering and forging process under pressure, so that effective bonding is achieved between the particles, and finally, a forging with a specific shape is formed through a metal fluid deformation, flow and mold filling process, and the microstructure of the obtained aluminum alloy forging is fine and uniform, thereby achieving an improvement in the strength and hardness of the forging.

[0055] Example 1

[0056] 1000g of mixed powder was put into a ball mill, wherein copper powder accounted for 3wt%, magnesium powder accounted for 3wt%, aluminum powder accounted for 94wt%, and the ball-to-material ratio was 10:1. 20ml of acetone and 4ml of aviation kerosene were added as anti-forging agents. The steel ball had an amplitude of 4mm and a frequency of 1470cpm. After mechanical milling for 50 hours, a high-activity powder was obtained, and the average grain size of the high-activity powder was 180 nanometers.

[0057] The high-activity powder was cold isostatically pressed at a pressure of 200 MPa and a holding time of 4 minutes to obtain a preform;

[0058] The preform is placed in a high temperature furnace for preheating at 630°C for 3 minutes;

[0059] The blank is taken out and placed in a forging die at 330°C, and the preform is subjected to powder forging and sintering. The first stage is initial forging, with a pressurizing speed of 0.5 mm / s, a pressure of 100 tons, and a forging ratio of 2:1. When the height of the forging obtained by the initial forging reaches 50% of the height of the preform, switch to the second stage of the process. The second stage is final forging, with a pressurizing speed of 10 mm / s, a pressure of 400 tons, and a forging ratio of 1.1:1 to obtain a forging product.

[0060] The product prepared in Example 1 of the present invention was sampled, polished, and tested. The tensile test was conducted in accordance with GB / T228.1-2010 "Metallic Material Tensile Test Part 1: Room Temperature Test Method", and the hardness test was conducted in accordance with GB231-84 "Metal Brinell Hardness Test Method". The forging properties obtained by the test are shown in Table 1. The microstructure analysis was conducted on the forging. The alloy forging prepared in Example 1 has a nano-scale microstructure. Figure 3 This is the TEM image of the aluminum alloy forging. It can be seen that the forging has a micro-nano microstructure.

[0061] Example 2

[0062] 1000g of mixed powder was put into a ball mill, wherein magnesium powder accounted for 2wt%, silicon powder accounted for 0.2wt%, zirconium powder accounted for 0.5wt%, aluminum powder accounted for 97.3wt%, and the ball-to-material ratio was 12:1. 22ml of acetone and 2ml of aviation kerosene were added as anti-forging agents. The steel ball had an amplitude of 5mm and a frequency of 1470cpm. After mechanical milling for 30 hours, a high-activity powder was obtained, and the average grain size of the high-activity powder was 400 nanometers.

[0063] The high-activity powder was cold isostatically pressed at a pressure of 300 MPa and a holding time of 2 minutes to obtain a preform;

[0064] The preform is placed in a high temperature furnace for preheating at 640°C for 2 minutes;

[0065] The blank is taken out and placed into a forging die at 320°C, and the preform is subjected to powder forging and sintering. The first stage is initial forging, and the pressurizing speed is 0.6 mm / s; the pressure is 200 tons, and the forging ratio is 1.8:1; when the height of the forging obtained by the initial forging reaches 56% of the height of the preform, switch to the second stage process; the second stage is final forging, and the pressurizing speed is 11 mm / s; the pressure is 550 tons, and the forging ratio is 1.5:1; and the forging product is obtained.

[0066] The product prepared in Example 2 was tested for performance, and the test results are shown in Table 1.

[0067] Example 3

[0068] 1000g of mixed powder was put into a ball mill, wherein copper powder accounted for 2wt%, silicon powder accounted for 0.5wt%, zirconium powder accounted for 0.3wt%, aluminum powder accounted for 97.2wt%, and the ball-to-material ratio was 8:1. 21ml of acetone and 3ml of aviation kerosene were added as anti-forging agents. The steel ball had an amplitude of 6mm and a frequency of 1470cpm. After mechanical milling for 45 hours, a high-activity powder was obtained. The average grain size of the high-activity powder was 200 nanometers.

[0069] The high-activity powder was cold isostatically pressed at a pressure of 230 MPa and a holding time of 3 minutes to obtain a preform;

[0070] The preform is placed in a high temperature furnace for preheating at a temperature of 580°C for 5 minutes;

[0071] The blank is taken out and placed in a forging die at 360°C, and the preform is subjected to powder forging and sintering. The first stage is initial forging, and the pressurizing speed is 0.5 mm / s; the pressure is 180 tons, and the forging ratio is 2.2:1; when the height of the forging obtained by the initial forging reaches 45% of the height of the preform, switch to the second stage process; the second stage is final forging, and the pressurizing speed is 12 mm / s, the pressure is 750 tons, and the forging ratio is 1.2:1; the forging product is obtained.

[0072] The product prepared in Example 3 was subjected to performance testing, and the test results are shown in Table 1.

[0073] Example 4

[0074] 1000g of mixed powder was put into a ball mill, wherein copper powder accounted for 3wt%, magnesium powder accounted for 1wt%, silicon powder accounted for 0.1wt%, zirconium powder accounted for 0.1wt%, and aluminum powder accounted for 97.2wt%. 24ml of acetone and 1ml of aviation kerosene were added as anti-forging agents. The steel ball had an amplitude of 5mm and a frequency of 1470cpm. After mechanical milling for 40 hours, a high-activity powder was obtained, and the average grain size of the high-activity powder was 300 nanometers.

[0075] The high-activity powder is cold isostatically pressed at a pressure of 250 MPa and a holding time of 2 minutes to obtain a preform;

[0076] The preform is placed in a high temperature furnace for preheating at 600°C for 4 minutes;

[0077] The blank is taken out and placed in a forging die at 350°C, and the preform is subjected to powder forging and sintering. The first stage is initial forging, and the pressurizing speed is 0.5 mm / s; the pressure is 180 tons, and the forging ratio is 2:1; when the height of the forging obtained by the initial forging reaches 50% of the height of the preform, switch to the second stage process; the second stage is final forging, and the pressurizing speed is 12 mm / s; the pressure is 600 tons, and the forging ratio is 1.3:1; and the forging product is obtained.

[0078] The product prepared in Example 4 was tested for performance, and the test results are shown in Table 1.

[0079] Example 5

[0080] 1000g of mixed powder was put into a ball mill, wherein copper powder accounted for 2wt%, magnesium powder accounted for 2wt%, zirconium powder accounted for 0.1wt%, aluminum powder accounted for 95.9wt%, and the ball-to-material ratio was 10:1. 23ml of acetone and 1ml of aviation kerosene were added as anti-forging agents. The steel ball had an amplitude of 5mm and a frequency of 1470cpm. After mechanical milling for 42 hours, a high-activity powder was obtained, and the average grain size of the high-activity powder was 280 nanometers.

[0081] The high-activity powder was cold isostatically pressed at a pressure of 230 MPa and a holding time of 3 minutes to obtain a preform;

[0082] The preform is placed in a high temperature furnace for preheating at 620°C for 3 minutes;

[0083] The blank is taken out and placed in a forging die at 340°C, and the preform is subjected to powder forging and sintering. The first stage is initial forging, and the pressurizing speed is 0.5 mm / s; the pressure is 200 tons, and the forging ratio is 2:1; when the height of the forging obtained by the initial forging reaches 50% of the height of the preform, switch to the second stage process; the second stage is final forging, and the pressurizing speed is 10 mm / s; the pressure is 750 tons, and the forging ratio is 1.4:1; and the forging product is obtained.

[0084] The product prepared in Example 5 was tested for performance, and the test results are shown in Table 1.

[0085] Table 1 Mechanical properties of forging products prepared in Example

[0086] Example 1 Example 2 Example 3 Example 4 Example 5 Tensile strength(MPa) 625 580 602 614 610 Yield strength(MPa) 580 535 550 555 557 Elongation(%) 2.5 4.0 3.2 2.8 3.0 Hardness (HB) 162 160 161 160 162

[0087] The preparation method provided by the present invention can simultaneously realize rapid sintering and forging deformation under pressure, and can realize the characteristics of high mechanical properties of forgings without a separate powder metallurgy sintering process, a separate forging process, and subsequent heat treatment processes such as solid solution and aging. Moreover, the entire preparation process of the present invention can be carried out in an air atmosphere; at the same time, it has the advantages of simple process, convenient operation, and few steps, and is suitable for large-scale industrial production of aluminum alloy forgings. The present invention uses a simple technology to achieve simultaneous sintering and forging of aluminum alloy powder metallurgy under pressure to obtain aluminum alloy forging products with ultrafine structure and high mechanical properties. The present invention uses high-energy ball milling technology to achieve the preparation of nano aluminum alloy powder; through in-situ activation sintering and forging technology, high-density aluminum alloy forgings are obtained, and their strength is greatly improved.

[0088] The key to the present invention lies in the preparation method of aluminum alloy forgings. The powder forging sintering technology is used to complete the rapid sintering of ultrafine aluminum alloy powder under pressure and the fluid deformation, flow and mold filling processes, and the powder sintering and sintered body forging deformation are simultaneously realized, and finally high-density, high-mechanical property aluminum alloy forgings are obtained, such as Al-Mg-Cu-Si-Zr forgings with ultrafine structure.

[0089] Although the present invention has been described and illustrated with reference to specific embodiments of the present invention, these descriptions and illustrations do not limit the present invention. It will be clearly understood by those skilled in the art that various changes may be made without departing from the true spirit and scope of the present invention as defined by the appended claims, so that specific circumstances, materials, material compositions, materials, methods or processes are suitable for the goals, spirit and scope of the present application. All such modifications are intended to be within the scope of the appended claims. Although the methods disclosed herein have been described with reference to specific operations performed in a specific order, it should be understood that these operations may be combined, subdivided or reordered to form equivalent methods without departing from the teachings of the present invention. Therefore, unless specifically indicated herein, the order and grouping of operations are not limitations of the present application.

Claims

1. A method for preparing a high-strength aluminum alloy forging, comprising: The aluminum powder and the alloy powder are subjected to high-energy ball milling to obtain a mixed powder; isostatically pressing the mixed powder to obtain a preform; Preheating the preform and then forging and sintering it to obtain a high-strength aluminum alloy forging; The forging and sintering is carried out in a forging die; the temperature of the forging die during the forging and sintering process is 320-360°C; The forging and sintering method comprises: First, perform one-stage pressurization and then two-stage pressurization; The speed of the pressurization stage is 0.5-0.6 mm / s; The speed of the second stage pressurization is 10-12 mm / s.

2. The method according to claim 1, characterized in that: The alloy powder comprises one or more components selected from Mg, Cu, Si and Zr.

3. The method according to claim 1, characterized in that: The ingredients of the mixed powder are: 0-3 wt% Mg; 0-3wt% Cu; 0-0.5wt% Si; 0-0.5wt% Zr; The balance is Al.

4. The method according to claim 1, characterized in that: The high energy ball milling time is 30 to 50 hours.

5. The method according to claim 1, characterized in that The ball-to-material ratio of the high-energy ball mill is (8-12):

1.

6. The method according to claim 1, characterized in that The average grain size of the mixed powder is 180-400 nm.

7. The method according to claim 1, characterized in that The isostatic pressing pressure is 200-300 MPa, and the isostatic pressing time is 2-4 min.

8. The method according to claim 1, characterized in that The preheating temperature is 580-640° C., and the preheating time is 2-5 minutes.

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