High strength plastic magnesium alloy component based on additive manufacturing and friction stir and preparation method thereof

Abstract

The application belongs to the field of additive manufacturing, and provides a high-strength plastic magnesium alloy component based on additive manufacturing and friction stirring and a preparation method. The preparation method comprises the following steps: using a magnesium alloy welding wire with a diameter of 0.8-4 mm to perform additive manufacturing on a magnesium alloy substrate, a welding gun is moved in a cyclic spiral swinging mode, the swinging radius is 3-16 mm, the distance between any two adjacent spiral centers in the spiral swinging process is 3-9 mm, the moving speed of the welding gun is 4-20 mm / s, the welding current is 100-170 A, the welding voltage is 15-30 V, and the wire feeding speed is 5-25 m / min; after obtaining 2-10 layers of magnesium alloy components, the surface is milled flat, and then friction stirring is performed on the component along the deposition direction, the diameter of the stirring head is 6-14 mm, the depth is 4-11 mm, the rotating speed is 100-2000 r / min, the advancing speed is 10-400 mm / min, and the pressing amount is 0.2-5 mm. The aforementioned additive manufacturing, milling and friction stirring are repeatedly cycled to finally obtain a 20-100 layer high-strength plastic magnesium alloy component, and the component has high strength and plasticity.

Description

Technical Field

[0001] The present invention belongs to the field of additive manufacturing, and in particular relates to a high-strength plastic magnesium alloy component based on additive manufacturing and stir friction and a preparation method thereof. Background Art

[0002] Magnesium alloys, with their advantages of low density, high specific strength, vibration damping, excellent biocompatibility, and biodegradability, hold great potential for application in aerospace, automotive, biomedical, and other fields. The manufacturing industry is increasingly demanding low energy consumption, high efficiency, and high performance, and component structures are becoming increasingly complex. However, traditional casting methods struggle to produce complex structures, irregular shapes, and large components, necessitating the development of new molding technologies.

[0003] Additive manufacturing (also known as 3D printing) technology has attracted widespread attention from both the industrial and commercial sectors due to its advantages, including mold-free, free-formability, and high forming precision. It also provides a new approach for forming complex components. Cold metal transfer, a type of arc-fuse additive manufacturing, offers advantages such as low heat input, high forming efficiency, and minimal equipment requirements. It is the preferred method for fabricating large components and has been widely used in various metal forming applications. However, the high temperature gradients and complex thermal cycles caused by rapid solidification lead to the formation of coarse columnar crystals, which reduce the effect of grain boundary strengthening. Stress concentration at the grain boundaries can cause premature fracture of the molded component, resulting in lower component performance and anisotropy in the mechanical properties of the molded component, both locally and globally. Therefore, how to transform coarse columnar crystals into fine equiaxed crystals, refine the grain size, enhance grain boundary strengthening, reduce stress concentration, effectively suppress premature fracture and local and global anisotropy in additively manufactured materials, improve component mechanical properties, and simultaneously enhance strength and ductility remains a pressing technical challenge. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention provides a high-strength plastic magnesium alloy component based on additive manufacturing and stir friction, and its preparation method includes the following steps:

[0005] (1) polishing the surface of the magnesium alloy substrate with sandpaper and cleaning it with anhydrous ethanol, and then drying it with a hair dryer to remove stains and an oxide layer on the surface of the magnesium alloy substrate to obtain a magnesium alloy substrate with a clean surface;

[0006] (2) fixing the magnesium alloy substrate obtained in step (1) on an additive manufacturing workbench, under a protective gas with a flow rate of 12-40 L / min, using a magnesium alloy welding wire with a diameter of 0.8-4 mm to perform additive manufacturing on the magnesium alloy substrate, wherein the additive manufacturing is performed by adjusting the vertical distance between the welding torch and the substrate to 6-22 mm, and the welding torch is moved in a circular spiral swing manner, wherein the swing radius is 3-16 mm, the interval distance between any two adjacent spiral centers in the spiral swing process is 3-9 mm, the moving speed of the welding torch is 4-20 mm / s, the welding current is 100-170 A, the welding voltage is 15-30 V, and the wire feeding speed is 5-25 m / min; after depositing a layer, the magnesium alloy substrate is cooled to 40-100 °C, and the impurity layer is removed by grinding, and then 2-10 layers of magnesium alloy additive components are deposited by the above-mentioned additive manufacturing cycle; and then the magnesium alloy additive components are milled and then subjected to friction stir processing. The friction stir processing is performed by using a friction stir processing device to perform friction stir processing on the magnesium alloy additive components in the middle of the magnesium alloy additive components along the deposition direction, wherein the diameter of the stirring head in the friction stir processing device is 6-14 mm, the depth of the stirring head is 4-11 mm, the rotating speed of the stirring head is 100-2000 rpm, the advancing speed of the stirring head is 10-400 mm / min, and the penetration of the stirring head is 0.2-5 mm, and then the above-mentioned additive manufacturing, milling and friction stir processing are performed. The above-mentioned additive manufacturing, milling and friction stir processing are repeated to obtain 20-100 layers of high strength and plastic magnesium alloy components based on additive manufacturing and friction stir processing.

[0007] Further, the magnesium alloy in step (1) is one of AZ31 magnesium alloy or AZ51 magnesium alloy or ZK61 magnesium alloy. Further, the magnesium alloy welding wire in step (2) is one of AZ31 magnesium alloy welding wire or AZ51 magnesium alloy welding wire or ZK61 magnesium alloy welding wire; the protective gas is argon or a mixture of argon and helium or a mixture of CO2 and argon; the volume ratio of argon and helium is 1-5:5-9; and the volume ratio of CO2 and argon is 1-5:95-99.

[0008] Further, the diameter of the magnesium alloy welding wire used in step (2) is 1-3.6 mm. Further, the diameter of the stirring head in the friction stir processing device in step (2) is 7-12 mm, the depth of the stirring head is 4.5-10.5 mm, the rotating speed of the stirring head is 120-1900 rpm, the advancing speed of the stirring head is 20-390 mm / min, and the penetration of the stirring head is 0.3-4.9 mm. DETAILED DESCRIPTION

[0009] Example 1

[0010] The preparation method of the high strength and plastic magnesium alloy component 1 is as follows:

[0011] AZ31 magnesium alloy substrate is used, and the welding wire is AZ31 magnesium alloy welding wire with a diameter of 1.2mm;

[0012] Step 1: Polish the surface of the AZ31 magnesium alloy substrate with sandpaper and clean it with anhydrous ethanol, and then use a hair dryer to dry it to remove stains and oxide layers on the surface of the AZ31 magnesium alloy substrate to obtain a clean surface of the AZ31 magnesium alloy substrate.

[0013] Step 2: The magnesium alloy substrate obtained in step 1 is fixed on an additive manufacturing workbench. Under argon protection, the protective gas flow rate is 14 L / min, and the magnesium alloy welding wire is additively manufactured on the magnesium alloy substrate. The additive manufacturing process is as follows: the vertical distance between the welding gun and the substrate is adjusted to 10 mm, and the welding gun moves in a cyclic spiral swing mode. The swing mode is as follows: the swing radius is 3 mm, and the spacing between any two adjacent spiral centers during the spiral swing is 4 mm. The travel speed of the welding gun is 5 mm / s, the welding current is 110 A, the welding voltage is 16.6 V, and the wire feeding speed is 6 m / min; after depositing a layer, the material to be deposited is After the layer is cooled to 40°C and polished to remove the impurity layer, a three-layer AZ31 magnesium alloy additive component is obtained after the above-mentioned additive manufacturing cycle treatment; after milling the surface of the component, stir friction treatment is performed: a stir friction device is used to perform stir friction processing in the middle of the milled additive component along the deposition direction, wherein the diameter of the stirring head in the stir friction device is 8 mm, the depth of the stirring head is 5 mm, the rotation speed of the stirring head is 200 rpm, the forward speed of the stirring head is 50 mm / min, and the pressure reduction of the stirring head is 0.3 mm, and then according to the above-mentioned additive manufacturing, milling and stir friction treatment, the cycle is repeated to finally obtain a 36-layer high-strength and plastic AZ31 magnesium alloy component 1.

[0014] Example 2

[0015] The preparation method of the high-strength plastic magnesium alloy component 2 is as follows:

[0016] The AZ31 magnesium alloy substrate is used, and the welding wire is AZ31 magnesium alloy welding wire with a diameter of 1.4mm;

[0017] Step 1: Polish the surface of the AZ31 magnesium alloy substrate with sandpaper and clean it with anhydrous ethanol, and then use a hair dryer to dry it to remove stains and oxide layers on the surface of the AZ31 magnesium alloy substrate to obtain an AZ31 magnesium alloy substrate with a clean surface.

[0018] Step 2: Fix the magnesium alloy substrate obtained in step 1 on an additive manufacturing workbench, and under argon protection, the protective gas flow rate is 20L / min, and perform additive manufacturing on the magnesium alloy welding wire on the magnesium alloy substrate. The additive manufacturing process is as follows: the vertical distance between the welding gun and the substrate is adjusted to 12mm, and the welding gun moves in a cyclic spiral swing mode. The swing mode is as follows: the swing radius is 4mm, and the distance between any two adjacent spiral centers during the spiral swing is 4.5mm. The travel speed of the welding gun is 6mm / s, the welding current is 115A, the welding voltage is 17V, and the wire feeding speed is 6.6m / min; after depositing a layer, the material is to be deposited. After the stacked layers were cooled to 45°C and polished to remove the impurity layer, a 4-layer AZ31 magnesium alloy additive component was obtained after the above-mentioned additive manufacturing cycle. After the component surface was milled, a stir friction treatment was performed: a stir friction device was used to perform stir friction processing in the middle of the milled additive component along the deposition direction, wherein the stirring head in the stir friction device had a diameter of 10 mm, a stirring head depth of 7 mm, a rotation speed of 300 rpm, a forward speed of 60 mm / min, and a pressing amount of 0.4 mm. Then, according to the above-mentioned additive manufacturing, milling and stir friction treatment, the cycle was repeated to finally obtain a 32-layer high-strength and plastic AZ31 magnesium alloy component 2.

[0019] Example 3

[0020] The preparation method of the high-strength plastic magnesium alloy component 3 is as follows:

[0021] The AZ31 magnesium alloy substrate is used, and the welding wire is AZ31 magnesium alloy welding wire with a diameter of 1.6 mm;

[0022] Step 1: Polish the surface of the AZ31 magnesium alloy substrate with sandpaper and clean it with anhydrous ethanol, and then use a hair dryer to dry it to remove stains and oxide layers on the surface of the AZ31 magnesium alloy substrate to obtain an AZ31 magnesium alloy substrate with a clean surface.

[0023] Step 2: The magnesium alloy substrate obtained in step 1 is fixed on an additive manufacturing workbench. Under argon protection, the protective gas flow rate is 22 L / min, and the magnesium alloy welding wire is additively manufactured on the magnesium alloy substrate. The additive manufacturing process is as follows: the vertical distance between the welding gun and the substrate is adjusted to 14 mm, and the welding gun moves in a cyclic spiral swing mode. The swing mode is as follows: the swing radius is 5 mm, and the distance between any two adjacent spiral centers during the spiral swing is 5 mm. The travel speed of the welding gun is 7 mm / s, the welding current is 120 A, the welding voltage is 18 V, and the wire feeding speed is 7 m / min; after depositing one layer, the deposited layer is cooled. After being cooled to 50°C and polished to remove the impurity layer, a 5-layer AZ31 magnesium alloy additive component was obtained after the above-mentioned additive manufacturing cycle treatment; after milling the surface of the component, stir friction treatment was performed: a stir friction device was used to perform stir friction processing in the middle of the milled additive component along the deposition direction, wherein the diameter of the stirring head in the stir friction device was 12 mm, the depth of the stirring head was 8.5 mm, the rotation speed of the stirring head was 500 rpm, the forward speed of the stirring head was 80 mm / min, and the pressure of the stirring head was 0.5 mm. Then, according to the above-mentioned additive manufacturing, milling and stir friction treatment, the cycle was repeated to finally obtain a 40-layer high-strength and plastic AZ31 magnesium alloy component 3.

[0024] Comparative Example 1

[0025] Journal title: Materials Science & Engineering A, Year: 2020, Page number: 138942, Author: Xu Yang et al., Title: “Microstructure and mechanical properties of wire and arc additive manufactured AZ31 magnesium alloy using cold metal transfer process”. Page 138943, “2.1 Materials and equipment”, Paragraph 1: The selected materials are AZ31 magnesium alloy welding wire with a diameter of 1.2 mm, and the substrate is AZ31 rolled plate. Page 138943, “2.2 Cold metal transfer process”, Paragraph 1: The welding gun has a travel speed of 10 mm / s, a welding current of 70 A, a welding voltage of 11 V, a wire feed speed of 2.5 m / min, and a unidirectional stroke to finally obtain a 30-layer additively manufactured component. Page 138949, Table 2: The tensile strength of the additively manufactured component is 151.9 MPa, and the elongation is 7.5%.

[0026] Comparative Example 2

[0027] The preparation method of the magnesium alloy component 4 is as follows:

[0028] The AZ31 magnesium alloy substrate is used, and the welding wire is AZ31 magnesium alloy welding wire with a diameter of 1.4mm;

[0029] Step 1: Polish the surface of the AZ31 magnesium alloy substrate with sandpaper and clean it with anhydrous ethanol, and then use a hair dryer to dry it to remove stains and oxide layers on the surface of the AZ31 magnesium alloy substrate to obtain an AZ31 magnesium alloy substrate with a clean surface.

[0030] Step 2: The magnesium alloy substrate obtained in step 1 is fixed on an additive manufacturing workbench. Under argon protection, the protective gas flow rate is 11 L / min, and the magnesium alloy welding wire is additively manufactured on the magnesium alloy substrate. The additive manufacturing process is as follows: the vertical distance between the welding gun and the substrate is adjusted to 5 mm, and the welding gun moves in a cyclic spiral swing mode. The swing mode is as follows: the swing radius is 2 mm, and the distance between any two adjacent spiral centers during the spiral swing is 2 mm. The travel speed of the welding gun is 3.6 mm / s, the welding current is 95 A, the welding voltage is 14.6 V, and the wire feeding speed is 4.6 m / min; after depositing a layer, the material is to be deposited. After the stacked layers were cooled to 30°C and polished to remove the impurity layer, a three-layer AZ31 magnesium alloy additive component was obtained according to the above-mentioned additive manufacturing cycle; after milling the surface of the component, a stir friction treatment was performed: a stir friction device was used to perform stir friction processing in the middle of the milled additive component along the deposition direction, wherein the diameter of the stirring head in the stir friction device was 5 mm, the depth of the stirring head was 3.5 mm, the rotation speed of the stirring head was 80 rpm, the forward speed of the stirring head was 8 mm / min, and the pressure reduction of the stirring head was 0.1 mm. Then, according to the above-mentioned additive manufacturing, milling and stir friction treatment, the cycle was repeated to finally obtain a 15-layer AZ31 magnesium alloy additive manufacturing component 4.

[0031] Table 1 Mechanical properties of magnesium alloy additively manufactured components obtained in Examples 1-3 and Comparative Examples 1-2

[0032]

[0033] As can be seen from Table 1, compared with Comparative Example 1-2 and the prior art, the number of layers of the magnesium alloy component obtained by the method of coupling additive manufacturing with friction stir processing in Example 1-3 is higher than that obtained by Comparative Example 1-2. According to the prior art reports, for the same alloy, the higher the number of layers, the lower the performance, because the multi-layer material will crack during additive manufacturing due to thermal stress. In addition, due to the existence of cyclic heat, the grains and second phase grow, which ultimately leads to lower performance. However, compared with the comparative example and the prior art, the present application not only obtains more layers of additive manufacturing components, but also significantly improves the performance of alloy strength and ductility. Among them, the tensile strength is ≥283.9 MPa, and the elongation is ≥14.2%, which are higher than the magnesium alloy with fewer layers in the prior art. At the same time, the preparation method of the present application effectively solves the problems of cracking, delamination, local and overall mechanical property anisotropy, non-uniformity, and difficulty in simultaneous improvement of strength and ductility of the prior art due to the increase in the number of layers. Compared with Comparative Example 1, the minimum strength of the magnesium alloy prepared by the present application is increased by 86.9%, and the minimum plasticity is increased by 89.3%. It can be seen that the present application can simultaneously improve the strength and ductility of the additive manufacturing magnesium alloy component. In addition, in all examples, the additive manufacturing and friction stir processing parameters used in each example are different, and the mechanical properties and elongation of the additive manufacturing components obtained are different. In addition, compared with Comparative Example 2, although Comparative Example 2 and the present application use similar alloy composition and preparation process, the process parameters used are not within the scope of protection of the present application, and the alloy strength and ductility are lower than the minimum value of the examples of the present application. This shows that the optimal mechanical properties of the components obtained by the present application are not determined by a certain component, ratio, process or process parameter, but are achieved by the synergistic control of components, ratios, processes and process parameters, and only within the scope of protection of the present application, the optimal performance of the material can be achieved. The present application breaks the bottleneck of the prior art that the strength and ductility of the additive manufacturing alloy are difficult to be improved simultaneously. In addition, the magnesium alloy component obtained by the present application has a significantly refined grain, and the larger second phase is also refined, the texture strength of the columnar crystal is reduced, which improves the situation of coarse columnar crystal, stress concentration and cracking caused by high cooling rate, high temperature gradient and complex thermal cycle during additive manufacturing, and improves the grain boundary strengthening effect. Therefore, the preparation method of the present application effectively suppresses the problems of premature fracture of additive manufacturing materials, insufficient mechanical properties, mechanical anisotropy, non-uniformity of local and overall mechanical properties, and difficulty in simultaneous improvement of strength and ductility.

Claims

1. A high-strength plastic magnesium alloy component based on additive manufacturing and stir friction, characterized in that: Its preparation method comprises the following steps: The AZ31 magnesium alloy substrate is used, and the welding wire is AZ31 magnesium alloy welding wire with a diameter of 1.2 mm; Step 1: Polish the surface of the AZ31 magnesium alloy substrate with sandpaper and clean it with anhydrous ethanol, and then use a hair dryer to dry it to remove stains and oxide layers on the surface of the AZ31 magnesium alloy substrate to obtain a clean surface of the AZ31 magnesium alloy substrate; Step 2: The magnesium alloy substrate obtained in step 1 is fixed on an additive manufacturing workbench. Under argon protection, the protective gas flow rate is 14 L / min, and the magnesium alloy welding wire is additively manufactured on the magnesium alloy substrate. The additive manufacturing process is as follows: the vertical distance between the welding gun and the substrate is adjusted to 10 mm, and the welding gun moves in a cyclic spiral swing mode. The swing mode is as follows: the swing radius is 3 mm, and the spacing between any two adjacent spiral centers during the spiral swing is 4 mm. The welding gun travels at a speed of 5 mm / s, a welding current of 110 A, a welding voltage of 16.6 V, and a wire feeding speed of 6 m / min. After depositing one layer, the deposited layer is cooled to 40 °C and polished to remove the impurity layer. After the above additive manufacturing cycle treatment, a three-layer AZ31 magnesium alloy additive component is obtained; after milling the surface of the component, stir friction treatment is performed: stir friction processing is performed in the middle of the milled additive component along the deposition direction using a stir friction device, wherein the diameter of the stirring head in the stir friction device is 8 mm, and the depth of the stirring head is 5. mm, the rotation speed of the stirring head is 200 rpm, the forward speed of the stirring head is 50 mm / min, the pressing amount of the stirring head is 0.3 mm, and then the aforementioned additive manufacturing, milling and stir friction treatment are repeated in this way to finally obtain a 36-layer additively manufactured and stir friction high-strength plastic magnesium alloy component.

2. A high-strength plastic magnesium alloy component based on additive manufacturing and stir friction, characterized in that: Its preparation method comprises the following steps: The AZ31 magnesium alloy substrate is used, and the welding wire is AZ31 magnesium alloy welding wire with a diameter of 1.4 mm; Step 1: Polish the surface of the AZ31 magnesium alloy substrate with sandpaper and clean it with anhydrous ethanol, and then use a hair dryer to dry it to remove stains and oxide layers on the surface of the AZ31 magnesium alloy substrate to obtain an AZ31 magnesium alloy substrate with a clean surface; Step 2: The magnesium alloy substrate obtained in step 1 is fixed on an additive manufacturing workbench. Under argon protection, the protective gas flow rate is 20 L / min, and the magnesium alloy welding wire is additively manufactured on the magnesium alloy substrate. The additive manufacturing process is as follows: the vertical distance between the welding gun and the substrate is adjusted to 12 mm, and the welding gun moves in a cyclic spiral swing mode. The swing mode is as follows: the swing radius is 4 mm, and the spacing between any two adjacent spiral centers during the spiral swing process is 4.5 mm. The welding gun travels at a speed of 6 mm / s, a welding current of 115 A, a welding voltage of 17 V, and a wire feeding speed of 6.6 m / min. After depositing a layer, the deposited layer is cooled to 45 °C and polished to remove the impurity layer. After the above-mentioned additive manufacturing cycle treatment, a 4-layer AZ31 magnesium alloy additive component is obtained; after milling the surface of the component, stir friction treatment is performed: stir friction processing is performed in the middle of the milled additive component along the deposition direction using a stir friction device, wherein the diameter of the stirring head in the stir friction device is 10 mm, and the depth of the stirring head is 7 mm, the rotation speed of the stirring head is 300 rpm, the forward speed of the stirring head is 60 mm / min, the pressing amount of the stirring head is 0.4 mm, and then the aforementioned additive manufacturing, milling and stir friction treatment are repeated in this way to finally obtain a 32-layer additively manufactured and stir friction high-strength plastic magnesium alloy component.

3. A high-strength plastic magnesium alloy component based on additive manufacturing and stir friction, characterized in that: Its preparation method comprises the following steps: AZ31 magnesium alloy substrate is used, and the welding wire is AZ31 magnesium alloy welding wire with a diameter of 1.6 mm; Step 1: Polish the surface of the AZ31 magnesium alloy substrate with sandpaper and clean it with anhydrous ethanol, and then use a hair dryer to dry it to remove stains and oxide layers on the surface of the AZ31 magnesium alloy substrate to obtain an AZ31 magnesium alloy substrate with a clean surface; Step 2: The magnesium alloy substrate obtained in step 1 is fixed on an additive manufacturing workbench. Under argon protection, the protective gas flow rate is 22 L / min, and the magnesium alloy welding wire is additively manufactured on the magnesium alloy substrate. The additive manufacturing process is as follows: the vertical distance between the welding gun and the substrate is adjusted to 14 mm, and the welding gun moves in a cyclic spiral swing mode. The swing mode is as follows: the swing radius is 5 mm, and the spacing between any two adjacent spiral centers during the spiral swing process is 5 mm. The welding gun travels at a speed of 7 mm / s, a welding current of 120 A, a welding voltage of 18 V, and a wire feeding speed of 7 m / min; after depositing a layer, the deposited layer is cooled to 50 ° C and polished to remove the impurity layer, and then a 5-layer AZ31 magnesium alloy additive component is obtained according to the above additive manufacturing cycle process; after milling the surface of the component, stir friction treatment is performed: stir friction processing is performed in the middle of the milled additive component along the deposition direction using a stir friction device, wherein the diameter of the stirring head in the stir friction device is 12 mm, and the depth of the stirring head is 8.5 mm, the rotation speed of the stirring head is 500 rpm, the forward speed of the stirring head is 80 mm / min, the pressing amount of the stirring head is 0.5 mm, and then the aforementioned additive manufacturing, milling and stir friction treatment are repeated in this way to finally obtain a 40-layer additively manufactured and stir friction high-strength plastic magnesium alloy component.

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