High-strength aluminum alloy for 3D material increase and preparation method of high-strength aluminum alloy

Abstract

The invention belongs to the field of 3D printing materials, and particularly relates to a high-strength aluminum alloy for 3D additional materials and a preparation method of the high-strength aluminum alloy. Mn: 2 to 2.5%; 1 to 1.5 percent of Cu; fe: 0.05 to 0.08%; si: 0.05 to 0.08%; 0.12% to 0.15% of Sc; and the balance of Al and inevitable impurities. According to the invention, the Sc element is added in the formula, centrifugal casting is used for assisting crystallization, liquid nitrogen rapid cooling is used for controlling the crystallization rate and refining equiaxed grains, and the content of the equiaxed grains in the alloy is increased to the maximum extent, so that the strength of the aluminum alloy is remarkably improved. And equiaxed grains can be uniformly distributed, so that crack formation and expansion are inhibited even in the long-time remelting process of subsequent 3D printing.

Description

Technical Field

[0001] The present invention belongs to the technical field of aluminum alloy preparation, and particularly relates to a high-strength aluminum alloy for 3D additive manufacturing and a preparation method thereof. Background Art

[0002] High-strength aluminum alloys have an irreplaceable position in the aerospace field due to their excellent combination of properties - high strength, low density, excellent machining and welding properties, outstanding corrosion resistance, and good electrical and thermal conductivity. These materials are widely used in key structures such as aircraft fuselages, aircraft wings, and rocket components. At the same time, assisted by 3D printing technology, one-piece forming is more suitable for fields such as aerospace, rail transit, and electronic products.

[0003] The high-strength aluminum alloy materials mainly focus on the optimization and modification of Al-Zn-Mg-Cu series alloys, and then the addition of elements such as Mn, Cr, and Ti significantly improves the relevant properties.

[0004] However, it is found that during the 3D printing process of the above high-strength aluminum alloy materials, for some regions with complex structures, after 3D printing, due to steps such as repeated melting, crystallization, and precipitation in these regions, local grain mutations are likely to occur, resulting in internal microcracks. In severe cases, internal microcracks even expand to form visible cracks. This limits the application of high-strength aluminum alloy materials in 3D printing. To solve these defects, it is usually necessary to improve the 3D printing process and further optimize the heat treatment process of high-strength aluminum alloy materials.

[0005] Based on this, the present invention is proposed. Summary of the Invention

[0006] The purpose of the present invention is to provide a high-strength aluminum alloy for 3D additive manufacturing and a preparation method thereof to solve the above problems.

[0007] In the first aspect, a high-strength aluminum alloy for 3D additive manufacturing includes the following components by weight percentage:

[0008] Zn: 6 - 6.5%; Mn: 2 - 2.5%; Cu: 1 - 1.5%; Fe: 0.05 - 0.08%; Si: 0.05 - 0.08%; Sc: 0.12 - 0.15%; the balance is Al and inevitable impurities.

[0009] In the second aspect, a preparation method of a high-strength aluminum alloy for 3D additive manufacturing includes the following steps:

[0010] Step 1: Weigh the raw materials corresponding to each component according to the ratio.

[0011] Step 2: Put the above raw materials into a melting furnace for melting, add a refining agent for refining, and then degas to obtain a refined melt.

[0012] Step 3: Pour the refined melt into a centrifugal casting machine for centrifugal casting. Liquid nitrogen spot cooling tube groups are arranged at both ends of the centrifugal casting machine. Each group of liquid nitrogen spot cooling tube groups consists of at least six liquid nitrogen spot cooling tubes, and the on-off of each liquid nitrogen spot cooling tube is controlled by a liquid nitrogen solenoid valve. After pouring the refined melt into the centrifugal casting machine, the centrifugal casting machine accelerates to 1500 r / min within 10 s. Then, the liquid nitrogen solenoid valve is opened, and the liquid nitrogen spot cooling tubes spray liquid nitrogen towards both ends of the centrifugal casting machine for rapid cooling. After the rapid cooling ends, the centrifugal casting machine maintains at a rotational speed of 1200 r / min until the centrifugal casting is completed, obtaining a centrifugally cast part.

[0013] Step 4: Perform heat treatment on the centrifugally cast part. After the heat treatment ends, cut off both ends of the centrifugally cast part to obtain the high-strength aluminum alloy for 3D additive manufacturing.

[0014] For further improvement, in Step 2, the melting temperature is 690 - 700 °C.

[0015] For further improvement, in Step 2, the refining agent is one or more of sodium chloride, potassium chloride, potassium fluosilicate, and potassium fluoroaluminate.

[0016] For further improvement, in Step 2, the refining temperature is 720 - 730 °C.

[0017] For further improvement, in Step 2, ultrasonic degassing is used for degassing.

[0018] For further improvement, after the liquid nitrogen solenoid valve is opened, the total amount of liquid nitrogen sprayed from a single liquid nitrogen spot cooling tube towards both ends of the centrifugal casting machine is 1 - 1.3 L, and the spraying time does not exceed 3 s. Then, the liquid nitrogen solenoid valve is closed, and the residual liquid nitrogen in the liquid nitrogen spot cooling tube is pumped back by a liquid nitrogen pump.

[0019] For further improvement, the distance between the nozzle of the liquid nitrogen spot cooling tube and the end face of the centrifugally cast part is 2 - 3 mm.

[0020] For further improvement, the heat treatment is to first perform solution treatment on the centrifugally cast part at a temperature of 472 ± 1 °C for 24 h, and then perform aging treatment at a temperature of 130 ± 1 °C for 24 h.

[0021] For further improvement, the width of the parts cut off from both ends of the centrifugally cast part is 5 - 10 cm.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] 1. By adding Sc element to the formula of the present invention, and combining with centrifugal casting to assist crystallization, and using liquid nitrogen rapid cooling to control the crystallization rate, the equiaxed grains are refined, and the content of equiaxed grains inside the alloy is maximized, thereby significantly improving the strength of the aluminum alloy (the tensile strength can reach 600 MPa).

[0024] 2. Since the liquid nitrogen rapid cooling is used to control the crystallization rate during centrifugal casting, the equiaxed grains can be evenly distributed, so that even during the long-time remelting process of subsequent 3D printing, the formation and propagation of cracks are inhibited. Specific embodiments

[0025] The present invention will be further described in detail below through specific embodiments.

[0026] Example 1

[0027] Formula 1:

[0028] Zn: 6%; Mn: 2.5%; Cu: 1%; Fe: 0.08%; Si: 0.08%; Sc: 0.12%; the rest are Al and inevitable impurities.

[0029] Step 1: Weigh the raw materials corresponding to each component according to the ratio.

[0030] Step 2: Put the above raw materials into a melting furnace for melting, and the melting temperature is 690 - 695 °C; after adding a refining agent for refining, the refining agent is made of sodium chloride and potassium fluorosilicate according to a mass ratio of 1:1, and the refining temperature is 720 - 725 °C; then use an ultrasonic degassing machine to remove gas to obtain a refined melt.

[0031] Step 3: Pour the refined melt into a centrifugal casting machine for centrifugal casting. Liquid nitrogen spot cooling pipe groups are arranged at both ends of the centrifugal casting machine. Each group of liquid nitrogen spot cooling pipe groups consists of six liquid nitrogen spot cooling pipes, and the on-off of each liquid nitrogen spot cooling pipe is controlled by a liquid nitrogen solenoid valve; after pouring the refined melt into the centrifugal casting machine, the centrifugal casting machine accelerates to 1500 r / min within 10 s, and then the liquid nitrogen solenoid valve is opened, and the liquid nitrogen spot cooling pipes spray liquid nitrogen at both ends of the centrifugal casting machine for rapid cooling; after the rapid cooling ends, the centrifugal casting machine maintains at a rotational speed of 1200 r / min until the centrifugal casting is completed to obtain a centrifugal casting.

[0032] Among them, after the liquid nitrogen solenoid valve is opened, the total amount of liquid nitrogen sprayed by a single liquid nitrogen spot cooling pipe at both ends of the centrifugal casting machine is 1 - 1.3 L, and the spraying time does not exceed 3 s, and then the liquid nitrogen solenoid valve is closed, and the residual liquid nitrogen in the liquid nitrogen spot cooling pipe is pumped back by a liquid nitrogen pump. The distance between the nozzle of the liquid nitrogen spot cooling pipe and the end face of the centrifugal casting is 2 - 3 mm.

[0033] Step 4: Heat-treat the centrifugally cast parts. After the heat treatment is completed, cut off both ends of the centrifugally cast parts to obtain high-strength aluminum alloy. Among them, the heat treatment is to first perform solution treatment on the centrifugally cast parts at a temperature of 472 ± 1 °C for 24 h, and then perform aging treatment at a temperature of 130 ± 1 °C for 24 h. The width of the parts cut off from both ends of the centrifugally cast parts is 10 cm.

[0034] Example 2

[0035] Formula 2:

[0036] Zn: 6.5%; Mn: 2%; Cu: 1.5%; Fe: 0.05%; Si: 0.05%; Sc: 0.15%; the balance is Al and unavoidable impurities.

[0037] Step 1: Weigh the raw materials corresponding to each component according to the ratio.

[0038] Step 2: Put the above raw materials into a melting furnace for melting. The melting temperature is 695 - 700 °C; after adding a refining agent, refine. The refining agent is made of sodium chloride and potassium fluosilicate in a mass ratio of 1:1, and the refining temperature is 725 - 730 °C; then use an ultrasonic degassing machine to remove gas to obtain a refined melt.

[0039] Step 3: Pour the refined melt into a centrifugal casting machine for centrifugal casting. Liquid nitrogen spot cooling tube groups are arranged at both ends of the centrifugal casting machine. Each group of liquid nitrogen spot cooling tube groups consists of six liquid nitrogen spot cooling tubes, and the on-off of each liquid nitrogen spot cooling tube is controlled by a liquid nitrogen solenoid valve; after pouring the refined melt into the centrifugal casting machine, the centrifugal casting machine accelerates to 1500 r / min within 10 s, and then the liquid nitrogen solenoid valve is opened, and the liquid nitrogen spot cooling tubes spray liquid nitrogen at both ends of the centrifugal casting machine for rapid cooling; after the rapid cooling is completed, the centrifugal casting machine maintains at a rotational speed of 1200 r / min until the centrifugal casting is completed to obtain a centrifugally cast part.

[0040] Among them, after the liquid nitrogen solenoid valve is opened, the total amount of liquid nitrogen sprayed by a single liquid nitrogen spot cooling tube at both ends of the centrifugal casting machine is 1 - 1.3 L, and the spraying time does not exceed 3 s. Then the liquid nitrogen solenoid valve is closed, and the residual liquid nitrogen in the liquid nitrogen spot cooling tube is pumped back by a liquid nitrogen pump. The distance between the nozzle of the liquid nitrogen spot cooling tube and the end face of the centrifugally cast part is 2 - 3 mm.

[0041] Step 4: Heat-treat the centrifugally cast parts. After the heat treatment is completed, cut off both ends of the centrifugally cast parts to obtain high-strength aluminum alloy. Among them, the heat treatment is to first perform solution treatment on the centrifugally cast parts at a temperature of 472 ± 1 °C for 24 h, and then perform aging treatment at a temperature of 130 ± 1 °C for 24 h. The width of the parts cut off from both ends of the centrifugally cast parts is 5 cm.

[0042] Example 3

[0043] Formula 3:

[0044] Zn: 6.3%; Mn: 2.2%; Cu: 1.2%; Fe: 0.07%; Si: 0.07%; Sc: 0.13%; the balance is Al and unavoidable impurities.

[0045] Step 1: Weigh the raw materials corresponding to each component according to the ratio.

[0046] Step 2: Put the above raw materials into a melting furnace for melting, and the melting temperature is 690 - 695°C; after adding a refining agent for refining, the refining agent is made of sodium chloride and potassium fluorosilicate in a mass ratio of 1:1, and the refining temperature is 725 - 730°C; then use an ultrasonic degassing machine to remove gas to obtain a refined melt.

[0047] Step 3: Pour the refined melt into a centrifugal casting machine for centrifugal casting. There are liquid nitrogen spot cooling tube groups at both ends of the centrifugal casting machine. Each group of liquid nitrogen spot cooling tube groups consists of six liquid nitrogen spot cooling tubes, and the on-off of each liquid nitrogen spot cooling tube is controlled by a liquid nitrogen solenoid valve; after pouring the refined melt into the centrifugal casting machine, the centrifugal casting machine accelerates to 1500 r / min within 10 s, and then the liquid nitrogen solenoid valve is opened, and the liquid nitrogen spot cooling tubes spray liquid nitrogen at both ends of the centrifugal casting machine for rapid cooling; after the rapid cooling ends, the centrifugal casting machine maintains at a rotational speed of 1200 r / min until the centrifugal casting ends to obtain a centrifugally cast part.

[0048] Among them, after the liquid nitrogen solenoid valve is opened, the total amount of liquid nitrogen sprayed by a single liquid nitrogen spot cooling tube at both ends of the centrifugal casting machine is 1 - 1.3 L, and the spraying time does not exceed 3 s. Then the liquid nitrogen solenoid valve is closed, and the residual liquid nitrogen in the liquid nitrogen spot cooling tube is pumped back by a liquid nitrogen pump. The distance between the nozzle of the liquid nitrogen spot cooling tube and the end face of the centrifugally cast part is 2 - 3 mm.

[0049] Step 4: Perform heat treatment on the centrifugally cast part. After the heat treatment ends, cut off both ends of the centrifugally cast part to obtain a high-strength aluminum alloy. Among them, the heat treatment is to first perform solution treatment on the centrifugally cast part at a temperature of 472 ± 1°C for 24 h, and then perform aging treatment at a temperature of 130 ± 1°C for 24 h. The width of the cut-off parts at both ends of the centrifugally cast part is 7 cm.

[0050] Comparative Example 1

[0051] The difference between this example and Example 1 is only that in step 3 of this example, the existing die-casting process is used instead of centrifugal casting. The existing die-casting process is as follows:

[0052] Press the refined melt into the preheated mold cavity after heating to 650°C. Among them, the initial casting pressure is 50 MPa, and after the filling rate exceeds 50%, the casting pressure is 65 MPa until the die-casting ends; the other steps are the same.

[0053] Comparative Example 2

[0054] The difference between this example and Example 1 is only that in step 3 of this example, only centrifugal casting is carried out, and the liquid nitrogen spot cooling tube group is not used for rapid cooling. Specifically:

[0055] Pour the refined molten liquid into a centrifugal casting machine for centrifugal casting. The centrifugal casting machine accelerates to 1500 r / min within 10 s, and then, the centrifugal casting machine maintains at a rotational speed of 1200 r / min until the centrifugal casting is completed, obtaining a centrifugal casting; the remaining steps are the same.

[0056] Comparative Example 3

[0057] The difference between this example and Example 1 is only that the liquid nitrogen in step 3 of this example is replaced by liquid carbon dioxide, and the remaining steps are the same.

[0058] Comparative Example 4

[0059] The difference between this example and Example 1 is only that step 3 of this example is as follows:

[0060] Pour the refined molten liquid into a centrifugal casting machine for centrifugal casting. Liquid nitrogen spot cooling tube groups are arranged at both ends of the centrifugal casting machine. Each group of liquid nitrogen spot cooling tube groups consists of six liquid nitrogen spot cooling tubes, and the on-off of each liquid nitrogen spot cooling tube is controlled by a liquid nitrogen solenoid valve; after pouring the refined molten liquid into the centrifugal casting machine, the centrifugal casting machine accelerates to 1500 r / min within 10 s, and then, the liquid nitrogen solenoid valve is opened, and the liquid nitrogen spot cooling tubes spray liquid nitrogen towards both ends of the centrifugal casting machine for rapid cooling; then, the centrifugal casting machine maintains at a rotational speed of 1200 r / min until the centrifugal casting is completed, and the liquid nitrogen rapid cooling also continues until the centrifugal casting is completed, finally obtaining a centrifugal casting; the remaining steps are the same.

[0061] Comparative Example 5

[0062] The difference between this example and Example 1 is only in Formula 1:

[0063] Zn: 6%; Mn: 2.5%; Cu: 1%; Fe: 0.08%; Si: 0.08%; the rest are Al and unavoidable impurities.

[0064] For the high-strength aluminum alloys obtained in Examples 1 to 3 and Comparative Examples 1 to 5, their properties are shown in Table 1:

[0065] Table 1

[0066] Yield strength / MPa Tensile strength / MPa Number of microcracks Example 1 520.6 598.3 0 Example 2 519.5 600.1 0 Example 3 518.7 597.8 0 Comparative example 1 190.9 235.1 6 Comparative example 2 507.4 588.2 17 Comparative example 3 511.8 593.1 13 Comparative example 4 432.7 509.9 31 Comparative example 5 263.8 310.5 /

[0067] Among them, the following method is adopted for testing the number of microcracks:

[0068] Use a 3D printer to face 3.14 cm 2After the printing of the area is completed, laser heating, cooling and solidification, and reheating are repeated for 10 minutes, so that the aluminum alloy melt in this area undergoes steps such as repeated melting, crystallization, and precipitation. After the aluminum alloy in this area is cooled to room temperature, X-rays are used to detect whether cracks are generated inside.

[0069] As can be seen from the above, in the present invention, by adding Sc element to the formula and cooperating with centrifugal casting to assist crystallization, the crystallization rate is controlled by rapid cooling with liquid nitrogen, the equiaxed grains are refined, and the content of equiaxed grains inside the alloy is maximally increased, thereby significantly improving the strength of the aluminum alloy. Since the crystallization rate is controlled by rapid cooling with liquid nitrogen during centrifugal casting, the equiaxed grains can be evenly distributed, so that even during the long-time remelting process of subsequent 3D printing, the formation and propagation of cracks are inhibited.

[0070] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A high-strength aluminum alloy for 3D additive manufacturing, characterized in that: It includes the following ingredients by weight percentage: Zn: 6-6.5%; Mn: 2-2.5%; Cu: 1-1.5%; Fe: 0.05-0.08%; Si: 0.05-0.08%; Sc: 0.12-0.15%; the rest are Al and unavoidable impurities.

2. The method for preparing a high-strength aluminum alloy for 3D additive manufacturing according to claim 1, characterized in that: The following steps are involved: Step 1, weigh the raw materials corresponding to each component according to the ratio; Step 2, putting the above raw materials into a smelting furnace for smelting, adding a refining agent and refining, and then degassing to obtain a refined melt; Step 3, pouring the refined molten metal into a centrifugal casting machine for centrifugal casting, and liquid nitrogen spot cooling tube groups are arranged at both ends of the centrifugal casting machine, and each group of liquid nitrogen spot cooling tube groups consists of at least six liquid nitrogen spot cooling tubes, and each liquid nitrogen spot cooling tube is controlled by a liquid nitrogen solenoid valve. After pouring the refined molten metal into the centrifugal casting machine, the centrifugal casting machine is accelerated to 1500r / min within 10s, and then the liquid nitrogen solenoid valve is opened, and the liquid nitrogen spot cooling tube sprays liquid nitrogen to both ends of the centrifugal casting machine for rapid cooling; after the rapid cooling is completed, the centrifugal casting machine is maintained at a speed of 1200r / min until the centrifugal casting is completed to obtain a centrifugal casting; Step 4: heat-treating the centrifugal casting. After the heat treatment, cut off the two ends of the centrifugal casting to obtain the high-strength aluminum alloy for 3D additive manufacturing.

3. The method for preparing a high-strength aluminum alloy for 3D additive manufacturing according to claim 2, characterized in that: In step 2, the smelting temperature is 690-700°C.

4. The method for preparing a high-strength aluminum alloy for 3D additive manufacturing according to claim 2, characterized in that: In step 2, the refining agent is one or more of sodium chloride, potassium chloride, potassium fluorosilicate and potassium fluoroaluminate.

5. The method for preparing a high-strength aluminum alloy for 3D additive manufacturing according to claim 2, characterized in that: In step 2, the refining temperature is 720-730°C.

6. The method for preparing a high-strength aluminum alloy for 3D additive manufacturing according to claim 2, characterized in that: In step 2, degassing is performed using an ultrasonic degasser.

7. The method for preparing a high-strength aluminum alloy for 3D additive manufacturing according to claim 2, characterized in that: After the liquid nitrogen solenoid valve is opened, a single liquid nitrogen spot cooling tube sprays a total of 1 to 1.3 L of liquid nitrogen to both ends of the centrifugal casting machine. The spraying time does not exceed 3 seconds. After that, the liquid nitrogen solenoid valve is closed and the residual liquid nitrogen in the liquid nitrogen spot cooling tube is pumped back by the liquid nitrogen pump.

8. The method for preparing a high-strength aluminum alloy for 3D additive manufacturing according to claim 2, characterized in that: The distance between the pipe opening of the liquid nitrogen spot cooling pipe and the end surface of the centrifugal casting is 2 to 3 mm.

9. The method for preparing a high-strength aluminum alloy for 3D additive manufacturing according to claim 2, characterized in that: The heat treatment is to firstly subject the centrifugal casting to a solution treatment at a temperature of 472±1°C for 24 hours, and then to an aging treatment at a temperature of 130±1°C for 24 hours.

10. The method for preparing a high-strength aluminum alloy for 3D additive manufacturing according to claim 2, characterized in that: The width of the cut-off parts at both ends of the centrifugal casting is 5 to 10 cm.