Aluminum alloy semi-solid blank preparation device and method based on combined extrusion process

Abstract

The invention discloses an aluminum alloy semi-solid blank preparation device and method based on a combined extrusion process. The device comprises a bottom plate, the bottom plate is matched with the bottom of a female die sleeve, a female die is embedded in the female die sleeve and composed of two symmetrical semi-circular truncated cones, four circular channels exist in the female die, and a first channel is coaxially communicated with a third channel through a second channel; the third channel and the fourth channel are communicated and distributed in a right-angle mode. The upper end inlet of the first channel is matched with the lower end of the pressure head; the method comprises the following steps: processing a blank to a corresponding size, heating a mold and putting the blank; then the blank is pushed through the pressing head to pass through the four channels to complete one-pass combined extrusion, and the blank is quenched after extrusion; and finally, remelting treatment is carried out in the semi-solid temperature interval. According to the method, efficient and uniform strain induction on the aluminum alloy blank is achieved, and an ideal initial structure is provided for subsequent semi-solid remelting while the production efficiency is improved.

Description

Technical Field

[0001] This invention belongs to the field of semi-solid metal processing technology, specifically relating to an apparatus and method for preparing semi-solid aluminum alloy billets based on a composite extrusion process. Background Technology Semi-solid metal processing technology is a near-net-shape forming technology that utilizes the thixotropic properties of metal materials in a solid-liquid coexistence state. Currently, the most widely used application of semi-solid thixotropic forging technology in aluminum alloys is semi-solid thixotropic forging technology, and the preparation of high-quality semi-solid billets is the key step in this technology.

[0002] Existing methods for preparing semi-solid billets mainly include mechanical stirring, electromagnetic stirring, strain-induced melting activation (SIMA) and recrystallization remelting. Among them, the SIMA method based on pre-deformation ([1] Xu Y, Jia JB, Chen C, Liu WC, Luo SY, Yang Y, et al. Thixoforming of semi-solid AZ91D alloy with high solid fraction prepared by the RUE-based SIMA process. Int J Adv ManufTech. 2017;93(9-12):4317-28; [2] Wang Y, Hu ML, Xu HY, Ji ZS, Wen XF, Liu XD. Effect of isothermal process parameters on semi-solid microstructure of chip-based Al-Cu-Mn-Ti alloy prepared by SIMA method. Mod Phys Lett B. 2020;34(33);[3] Jiang JF, Wang Y, Xiao GF, Nie X. Comparison of microstructuralevolution of 7075 aluminum alloy fabricated by SIMA and RAP. J Mater ProcessTech. (2016;238:361-72) This method has attracted widespread attention due to its simple operation and the fact that it does not require handling molten metal. Typically, the billet is first pre-deformed to store strain energy, and then remelted at a semi-solid temperature to transform it into spherical grains, accompanied by the appearance of a liquid phase. To ensure the stored strain energy, upsetting, positive extrusion, and equal channel angle extrusion often require multiple passes, which complicates the process and reduces production efficiency. Radial forging and other techniques require specialized radial forging equipment, which is costly and also requires multiple passes to achieve a higher section reduction rate. Therefore, there is a need to develop an efficient device and method that can complete large deformation in one pass, achieve uniform and refined microstructure, and is suitable for preparing large-sized semi-solid billets. Summary of the Invention

[0003] In order to overcome the shortcomings of the prior art, the present invention aims to provide an apparatus and method for preparing semi-solid aluminum alloy billets based on a composite extrusion process. This method combines the large deformation capacity of conventional extrusion with the intense shear deformation capacity of equal channel angle extrusion in one pass, thereby achieving efficient and uniform strain induction of aluminum alloy billets. This improves production efficiency while providing an ideal initial microstructure for subsequent semi-solid remelting.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A semi-solid aluminum alloy billet preparation device based on a composite extrusion process includes a base plate 3. A cylindrical groove in the base plate 3 engages with a cylindrical protrusion at the bottom of a die sleeve 2. An ejection hole 2-1 is opened at the bottom of the die sleeve 2. A die 1 is nested inside the die sleeve 2. The die 1 is composed of two symmetrical semi-circular truncated cones. There are four circular channels inside the die 1, which are, from the inlet to the outlet, the first channel 1-1, the second channel 1-2, the third channel 1-3, and the fourth channel 1-4. The first channel 1-1 is coaxially connected to the second channel 1-2 and the third channel 1-3. The third channel 1-3 is connected to the fourth channel 1-4 and is distributed at right angles. A circular through hole is opened on the wall of the die sleeve 2, and its diameter is the same as that of the fourth channel 1-4. After assembly, the through hole is concentric with the fourth channel 1-4. The upper inlet of the first channel 1-1 engages with the lower end of the pressure head 5. The upper end of the pressure head 5 contacts the bottom surface of the upper die 4. The upper die 4 presses down to control the downward movement of the pressure head 5.

[0005] The slope of the inner wall of the die sleeve 2 is consistent with the slope of the outer wall of the die 1.

[0006] The first channel 1-1, the third channel 1-3, and the fourth channel 1-4 are equal diameter channels, while the second channel 1-2 is a variable diameter channel, wherein the diameter at the outlet of the second channel 1-2 is half the diameter at the inlet, and the angle between its inner wall and the channel axis is 30°.

[0007] The diameters of the third channel 1-3 and the fourth channel 1-4 are kept consistent. The process from the third channel 1-3 to the fourth channel 1-4 is an equal diameter angular extrusion process, and the inner and outer angular radii are adjusted according to the size of the bar stock.

[0008] The diameter of the pressure head 5 is slightly smaller than the diameter of the first channel 1-1.

[0009] A method for preparing semi-solid aluminum alloy billets using a composite extrusion process includes the following steps: Step 1: Process the raw bar stock into blanks of the corresponding diameter and length; Step 2: First, tightly fit the ceramic heating ring onto the outside of the concave mold sleeve 2. Use a PID temperature control box to perform closed-loop control of the heating process. Use a K-type thermocouple inserted into the core of the concave mold 1 to monitor the internal temperature fluctuation in real time. In addition, cover the upper surface of the concave mold 1 with an asbestos insulation layer. When the temperature stabilizes at 300℃, transfer the blank to the first channel 1-1 of the concave mold 1 for heating. Step 3: The upper die 4 controls the pressure head 5 to move downwards, controlling the billet to move from the first channel 1-1 to the fourth channel 1-4, completing the compound extrusion forming; after the extrusion process is completed, the billet remains in the die 1, and after the die is opened, the billet is placed in cold water for quenching. Step 4: Set the furnace temperature to 540℃-610℃. After the temperature stabilizes, place the quenched billet in the furnace and hold it for 5-20 minutes. Then, remove the billet to obtain a semi-solid aluminum alloy billet.

[0010] The blank used in step one is 2A12 aluminum alloy blank, and the heating temperature in step four is 580℃-610℃.

[0011] The blank used in step one is 2A14 aluminum alloy blank, and the heating temperature in step four is 540℃-580℃.

[0012] Compared with existing semi-solid billet preparation methods, the present invention has the following advantages: I. Simplified process flow and improved production efficiency. Unlike multi-pass upsetting, rolling and extrusion, this invention combines the large deformation capacity of conventional extrusion with the intense shear deformation capacity of equal channel angle extrusion in a single pass. Although the aluminum alloy billet consumes some energy during recovery and recrystallization in conventional extrusion and equal channel angle extrusion, a large amount of strain energy is still accumulated inside. Furthermore, the subsequent equal channel angle extrusion process makes the internal strain of the billet more uniform. Finally, after semi-solid isothermal treatment, a semi-solid microstructure with an average grain size in the range of 70-100μm and uniform distribution is obtained.

[0013] Second, the produced blanks have relatively regular shapes and do not require secondary processing.

[0014] Third, the device of the present invention has a simple structure and strong applicability. The device of the present invention can be operated using only a common press, and the requirements for the equipment are relatively low. Attached Figure Description

[0015] Figure 1 This is a front sectional view of the overall structure of the device according to an embodiment of the present invention.

[0016] Figure 2 This is an image of the semi-solid microstructure of 2A12 aluminum alloy obtained in the embodiment of the present invention.

[0017] Figure 3This is an image of the semi-solid microstructure of 2A14 aluminum alloy obtained in the embodiment of the present invention. Detailed Implementation

[0018] The present invention will now be described in detail with reference to the embodiments and accompanying drawings.

[0019] Reference Figure 1 A device for preparing semi-solid aluminum alloy blanks based on a composite extrusion process includes a die 1, a die sleeve 2, a base plate 3, an upper die 4, and a pressure head 5. A cylindrical groove in the base plate 3 engages with a cylindrical protrusion at the bottom of the die sleeve 2 to fix the position of the die sleeve 2. An ejection hole 2-1 is opened at the bottom of the die sleeve 2 to eject the die 1 from the die sleeve 2. The die 1 is nested inside the die sleeve 2, and the slope of the inner wall of the die sleeve 2 is consistent with the slope of the outer wall of the die 1. The die 1 is composed of two symmetrical semi-circular truncated cones. The die 1 has four circular channels inside, from the inlet to the outlet: a first channel 1-1, a second channel 1-2, a third channel 1-3, and a fourth channel 1-4. The first channel 1-1 is coaxially connected to the second channel 1-2 and the third channel 1-3. The third channel 1-3 is connected to the fourth channel 1-4 and is distributed at right angles. Channels 1-1, 1-3, and 1-4 are equal-diameter channels, while channel 1-2 is a variable-diameter channel. The diameter at the outlet of channel 1-2 is half the diameter at the inlet, and the angle between its inner wall and the channel axis is 30°. The diameters of channels 1-3 and 1-4 are consistent. The process from channel 1-3 to channel 1-4 is an equal-diameter angular extrusion process, with the inner and outer radii adjusted according to the size of the bar stock. A circular through hole with the same diameter as channel 1-4 is opened on the wall of die sleeve 2. After assembly, this through hole is concentric with channel 1-4. The upper inlet of channel 1-1 mates with the lower end of the pressure head 5. The upper end of the pressure head 5 contacts the bottom surface of the upper die 4. The upper die 4 presses down to control the downward movement of the pressure head 5. The diameter of the pressure head 5 is slightly smaller than the diameter of channel 1-1.

[0020] A method for preparing semi-solid aluminum alloy billets using a composite extrusion process includes the following steps: Step 1: Process the raw bar stock into billets with a specific diameter and length; Step 2: First, tightly fit the matching ceramic heating ring onto the outside of the concave mold sleeve 2. Use a PID temperature control box to perform closed-loop control of the heating process. Use a K-type thermocouple inserted into the core of the concave mold 1 to monitor the internal temperature fluctuation in real time. In addition, cover the upper surface of the concave mold 1 with an asbestos insulation layer of a certain thickness. When the temperature stabilizes at 300℃, quickly transfer the billet into the first channel 1-1 of the concave mold 1 for heating. Step 3: The upper die 4 controls the pressure head 5 to move downwards, controlling the billet to move from the first channel 1-1 to the fourth channel 1-4, completing the compound extrusion forming; after the extrusion process is completed, the billet remains in the die 1, and after the die is opened, the billet is placed in cold water for quenching. Step 4: Set the furnace temperature to 540℃-610℃. After the temperature stabilizes, place the quenched billet in the furnace and hold it for 5-20 minutes. Then, remove the billet to obtain a semi-solid aluminum alloy billet.

[0021] The billet used in step one is 2A12 aluminum alloy billet, and the heating temperature in step four is 580℃-610℃. The billet used in step one is 2A14 aluminum alloy billet, and the heating temperature in step four is 540℃-580℃.

[0022] The beneficial effects of this embodiment are: the aluminum alloys used are 2A12 aluminum alloy and 2A14 aluminum alloy, and the microstructure of the final semi-solid billet is as follows. Figure 2 , Figure 3 As shown, statistical analysis reveals that the average grain size is between 70-100 μm, indicating a high degree of spheroidization. This demonstrates that the method can effectively prepare semi-solid blanks for 2A12 and 2A14 aluminum alloys, and is also applicable to other types of aluminum alloys.

Claims

1. An apparatus for preparing semi-solid aluminum alloy billets based on a composite extrusion process, comprising a base plate (3), characterized in that: The cylindrical groove of the base plate (3) fits with the cylindrical protrusion at the bottom of the die sleeve (2). The bottom of the die sleeve (2) has an ejector hole (2-1). The die sleeve (2) contains a die (1). The die (1) is composed of two symmetrical semi-circular truncated cones. There are four circular channels inside the die (1), which are the first channel (1-1), the second channel (1-2), the third channel (1-3), and the fourth channel (1-4) from the inlet to the outlet. The first channel (1-1) passes through the second channel (1-4). 2) It is coaxially connected with the third channel (1-3); the third channel (1-3) is connected with the fourth channel (1-4) and is distributed at right angles; a circular through hole is opened in the wall of the die sleeve (2), the diameter of which is the same as the diameter of the fourth channel (1-4). After assembly, the through hole is concentric with the fourth channel (1-4); the upper entrance of the first channel (1-1) and the lower end of the pressure head (5) are matched, the upper end of the pressure head (5) is in contact with the bottom surface of the upper die (4), and the upper die (4) presses down to control the pressure head (5) to move downward.

2. The apparatus according to claim 1, characterized in that: The slope of the inner wall of the die sleeve (2) is consistent with the slope of the outer wall of the die (1).

3. The apparatus according to claim 1, characterized in that: The first channel (1-1), the third channel (1-3), and the fourth channel (1-4) are equal diameter channels, and the second channel (1-2) is a variable diameter channel, wherein the diameter at the outlet of the second channel (1-2) is half the diameter at the inlet, and the angle between its inner wall and the channel axis is 30°.

4. The apparatus according to claim 1, characterized in that: The diameters of the third channel (1-3) and the fourth channel (1-4) are kept consistent. The process from the third channel (1-3) to the fourth channel (1-4) is an equal diameter angular extrusion process, and the inner and outer angular radii are adjusted according to the size of the bar stock.

5. The apparatus according to claim 1, characterized in that: The diameter of the pressure head (5) is slightly smaller than the diameter of the first channel (1-1).

6. A method for preparing semi-solid aluminum alloy billets using a composite extrusion process according to any one of claims 1-5, characterized in that, Includes the following steps: Step 1: Process the raw bar stock into blanks of the corresponding diameter and length; Step 2: First, tightly cover the ceramic heating ring on the outside of the concave mold sleeve (2), and use a PID temperature control box to perform closed-loop control of the heating process. Use a K-type thermocouple inserted into the core of the concave mold (1) to monitor the internal temperature fluctuation in real time. In addition, cover the upper surface of the concave mold (1) with an asbestos insulation layer. When the temperature stabilizes at 300℃, transfer the blank to the first channel (1-1) of the concave mold (1) for heating. Step 3: The upper die (4) controls the pressure head (5) to move downward, controlling the billet to move from the first channel (1-1) to the fourth channel (1-4) to complete the compound extrusion forming; after the extrusion process is completed, the billet remains in the die (1), and after the die is opened, the billet is placed in cold water for quenching; Step 4: Set the furnace temperature to 540℃-610℃. After the temperature stabilizes, place the quenched billet in the furnace and hold it for 5-20 minutes. Then, remove the billet to obtain a semi-solid aluminum alloy billet.

7. The method according to claim 6, characterized in that: The blank used in step one is 2A12 aluminum alloy blank, and the heating temperature in step four is 580℃-610℃.

8. The method according to claim 6, characterized in that: The blank used in step one is 2A14 aluminum alloy blank, and the heating temperature in step four is 540℃-580℃.

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