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

Abstract

The invention belongs to the field of additive manufacturing, and provides a high-strength plastic magnesium alloy component based on additive manufacturing and friction stir and a preparation method. The preparation method comprises the steps that on a magnesium alloy substrate, a magnesium alloy welding wire with the diameter being 0.8-4 mm is adopted for additive manufacturing, a welding gun advances in a circulating spiral swing mode, the swing radius is 3-16 mm, the distance between any two adjacent spiral centers in the spiral swing process is 3-9 mm, the advancing 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 welding gun is welded to a magnesium alloy substrate. The wire feeding speed is 5-25 m / min; after a 2-10-layer magnesium alloy component is obtained, the surface is milled, stirring friction machining is conducted in the middle of the component in the deposition direction, the diameter of a stirring head ranges from 6 mm to 14 mm, the depth ranges from 4 mm to 11 mm, the rotating speed ranges from 100 r / min to 2000 r / min, the advancing speed ranges from 10 mm / min to 400 mm / min, and the rolling reduction ranges from 0.2 mm to 5 mm. According to the repeated circulation of additive manufacturing, milling and friction stir processing, 20-100 layers of high-strength plastic magnesium alloy components are finally obtained, and the components have 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 have great potential for application in aerospace, automotive, biomedical and other fields due to their low density, high specific strength, damping and vibration reduction, good biocompatibility, and in vivo degradability. The development of the manufacturing industry has an increasing demand for low energy consumption, high efficiency and high performance, and the structure of parts is becoming increasingly complex. However, traditional casting methods are difficult to manufacture complex structures, irregular shapes, and large components, so new molding technologies need to be developed.

[0003] Additive manufacturing (also known as 3D printing) technology has the advantages of no need for molds, free forming, and high forming precision. It has attracted widespread attention from the industrial and commercial sectors and also provides a new way to form complex parts. As a type of arc fuse additive manufacturing, cold metal transition has the advantages of low heat input, high forming efficiency, and low equipment requirements. It is the first choice for preparing large parts and has been widely used in various metal forming. However, due to the high temperature gradient and complex thermal cycle caused by rapid solidification, coarse columnar crystals are generated, which will reduce the effect of grain boundary strengthening, and the stress concentration at the grain boundary will cause the molded component to break prematurely, resulting in low performance of the molded component. In addition, the molded component exhibits anisotropy in mechanical properties locally or as a whole. Therefore, how to transform coarse columnar crystals into fine equiaxed crystals, refine grains, improve grain boundary strengthening, reduce stress concentration, effectively inhibit the premature fracture of additive manufacturing materials, local and overall anisotropy, and improve the mechanical properties of components and simultaneously improve strength and plasticity are technical problems that need to be solved urgently. 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 comprises the following steps:

[0005] (1) grinding 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) The magnesium alloy substrate obtained in step (1) is fixed on an additive manufacturing workbench, and under a protective gas, the protective gas flow rate is 12-40L / min, and a magnesium alloy welding wire with a diameter of 0.8-4mm is used to perform additive manufacturing on the magnesium alloy substrate. The additive manufacturing is as follows: the vertical distance between the welding gun and the substrate is adjusted to 6-22mm, and the welding gun moves in a cyclic spiral swinging manner. The swinging manner is as follows: the swing radius is 3-16mm, the spacing distance between any two adjacent spiral centers during the spiral swinging process is 3-9mm, the travel speed of the welding gun is 4-20mm / s, the welding current is 100-170A, the welding voltage is 15-30V, and the wire feeding speed is 5-25m / min; after depositing a layer, the deposited layer is cooled to 40-100℃ and polished to remove the impurity layer, and then 2-10 layers of magnesium alloy additive components are obtained after the above-mentioned additive manufacturing cycle deposition; and then stir friction treatment is performed after milling. The friction stir treatment is: using a friction stir device to perform friction stir processing in the middle of the additive component along the deposition direction, wherein the diameter of the stirring head in the friction stir device is 6-14mm, the depth of the stirring head is 4-11mm, the rotation speed of the stirring head is 100-2000 rpm, the forward speed of the stirring head is 10-400mm / min, and the pressing amount of the stirring head is 0.2-5mm, and then the aforementioned additive manufacturing, milling and friction stir processing are performed. This cycle is repeated to finally obtain 20-100 layers of high-strength plastic magnesium alloy components based on additive manufacturing and friction stir.

[0007] Furthermore, the magnesium alloy in step (1) is one of AZ31 magnesium alloy, AZ51 magnesium alloy or ZK61 magnesium alloy. Furthermore, the magnesium alloy welding wire in step (2) is one of AZ31 magnesium alloy welding wire, AZ51 magnesium alloy welding wire or ZK61 magnesium alloy welding wire; the shielding 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; the volume ratio of CO2 and argon is 1-5:95-99.

[0008] Further, the step (2) uses a magnesium alloy welding wire with a diameter of 1-3.6 mm to perform additive manufacturing on a magnesium alloy substrate. Further, the stirring head diameter in the friction stirring device in step (2) is 7-12 mm, the stirring head depth is 4.5-10.5 mm, the rotation speed of the stirring head is 120-1900 rpm, the forward speed of the stirring head is 20-390 mm / min, and the pressing amount 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] The AZ31 magnesium alloy substrate is used, and the welding wire is AZ31 magnesium alloy welding wire with a diameter of 1.2 mm;

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

[0013] 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 14L / 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 10mm, and the welding gun moves in a cyclic spiral swing mode. The swing mode is as follows: the swing radius is 3mm, and the interval between any two adjacent spiral centers during the spiral swing process is 4mm. The travel speed of the welding gun is 5mm / s, the welding current is 110A, the welding voltage is 16.6V, and the wire feeding speed is 6m / 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 3-layer AZ31 magnesium alloy additive component is obtained according to the above-mentioned additive manufacturing cycle; 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 of the stirring head is 0.3 mm, and then according to the above-mentioned additive manufacturing, milling and stir friction treatment, this 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 and 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 1.4 mm;

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

[0018] Step 2: The magnesium alloy substrate obtained in step 1 is fixed on an additive manufacturing workbench, and under argon protection, the protective gas flow rate is 20L / min, and the magnesium alloy welding wire is subjected to additive manufacturing 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 spacing between any two adjacent spiral centers during the spiral swing process 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 deposition is 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 treatment; 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 10 mm, the depth of the stirring head was 7 mm, the rotation speed of the stirring head was 300 rpm, the forward speed of the stirring head was 60 mm / min, and the pressure of the stirring head was 0.4 mm, and then the above-mentioned additive manufacturing, milling and stir friction treatment were repeated, and finally a 32-layer high-strength and plastic AZ31 magnesium alloy component 2 was obtained.

[0019] Example 3

[0020] The preparation method of the high-strength and 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: Grind the surface of the AZ31 magnesium alloy substrate with sandpaper and clean it with anhydrous ethanol, and then dry it with a hair dryer to remove stains and an oxide layer 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, and under argon protection, the protective gas flow rate is 22L / min, and the magnesium alloy welding wire is subjected to additive manufacturing 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 14mm, and the welding gun moves in a cyclic spiral swing mode. The swing mode is as follows: the swing radius is 5mm, and the interval between any two adjacent spiral centers during the spiral swing process is 5mm. The travel speed of the welding gun is 7mm / s, the welding current is 120A, the welding voltage is 18V, and the wire feeding speed is 7m / 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 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 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, and then the above-mentioned additive manufacturing, milling and stir friction treatment were repeated, and finally a 40-layer high-strength and plastic AZ31 magnesium alloy component 3 was obtained.

[0024] Comparative Example 1

[0025] Journal name: Materials Science & Engineering A, year: 2020, page number: 138942, paper 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 material is 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 travel speed of the welding gun is 10 mm / s, the welding current is 70 A, the welding voltage is 11 V, the wire feeding speed is 2.5 m / min, and a unidirectional stroke is used 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 1.4 mm;

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

[0030] 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 11L / 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 5mm, and the welding gun moves in a cyclic spiral swing mode. The swing mode is as follows: the swing radius is 2mm, and the interval between any two adjacent spiral centers during the spiral swing process is 2mm. The travel speed of the welding gun is 3.6mm / s, the welding current is 95A, the welding voltage is 14.6V, and the wire feeding speed is 4.6m / min; after depositing a layer, the deposition is 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 of the stirring head was 0.1 mm, and then the above-mentioned additive manufacturing, milling and stir friction treatment were repeated, and finally a 15-layer AZ31 magnesium alloy additive manufacturing component 4 was obtained.

[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 Examples 1-2 and the prior art, the number of layers of magnesium alloy components obtained by the coupling preparation method of additive manufacturing and stir friction processing in Examples 1-3 is higher than the number of layers obtained in Comparative Examples 1-2. According to prior art reports, for the same alloy, the higher the number of layers, the lower the performance, because the multilayer material will crack due to thermal stress during the additive preparation process. In addition, due to the existence of cyclic heat, the grains and the second phase grow, which ultimately leads to low performance. However, compared with the comparative example and the prior art, the present invention not only obtains more layers of additive manufacturing components, but also significantly improves the properties of the alloy such as strength and plasticity. Among them, the tensile strength is ≥283.9MPa and the elongation is ≥14.2%, which are both higher than the magnesium alloy with fewer layers in the prior art. At the same time, the preparation method of the present invention effectively solves the problems of cracking, delamination, local and overall mechanical properties, heterogeneity, and difficulty in improving strength and plasticity simultaneously due to the increase in the number of layers in the prior art. Compared with Comparative Example 1, the minimum strength of the magnesium alloy prepared by the present invention is increased by 86.9%, and the minimum plasticity is increased by 89.3%. It can be seen from this that the present invention can simultaneously improve the strength and plasticity of additively manufactured magnesium alloy components. In addition, in all embodiments, the additive manufacturing and stir friction processing process parameters used in each embodiment are different, and the mechanical properties and elongation of the additively manufactured components finally obtained are different. In addition, compared with Comparative Example 2, although Comparative Example 2 uses similar alloy components and preparation processes as the present invention, the process parameters used are not within the scope of protection of the claims of the present invention, and the alloy strength and plasticity are all lower than the minimum value of the embodiments of the present invention. It is thus shown that the most excellent mechanical properties of the components obtained by the present invention are not determined by a certain component, ratio, process or process parameter, but are achieved by the coordinated regulation of components, ratios, processes and process parameters, and only within the scope of protection of the claims of the present invention can the most excellent performance of the material be achieved. The present invention breaks the bottleneck that the strength and plasticity of the alloys in the additive manufacturing of the prior art are difficult to improve simultaneously. In addition, the grains of the magnesium alloy components obtained by the present invention are significantly refined, the larger second phase is also refined, the texture strength of the columnar crystals is reduced, and the situation of the generation of coarse columnar crystals, stress concentration and cracking caused by high cooling rate, high temperature gradient and complex thermal cycle in additive manufacturing is improved, and the grain boundary strengthening effect is improved. Therefore, the preparation method of the present invention effectively suppresses problems such as premature fracture of additive manufacturing materials, insufficient mechanical properties, mechanical anisotropy, uneven local and overall mechanical properties, and difficulty in simultaneously improving strength and plasticity.

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: (1) grinding 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; (2) The magnesium alloy substrate obtained in step (1) is fixed on an additive manufacturing workbench, and under a protective gas, the protective gas flow rate is 12-40 L / min, and additive manufacturing is performed on the magnesium alloy substrate using a magnesium alloy welding wire with a diameter of 0.8-4 mm; the additive manufacturing is as follows: the vertical distance between the welding gun and the substrate is adjusted to 6-22 mm, and the welding gun moves in a cyclic spiral swinging manner; the swinging manner is as follows: the swing radius is 3-16 mm, the spacing distance between any two adjacent spiral centers during the spiral swinging process is 3-9 mm, the welding gun travel speed 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 one layer, wait for the deposited layer to cool to 40-100°C and grind to remove the impurity layer, and then obtain 2-10 layers of magnesium alloy additive components after the above-mentioned additive manufacturing cycle deposition; and then stir friction treatment after milling; the stir friction treatment is: use a stir friction device to stir friction processing in the middle of the additive component along the deposition direction, wherein the stirring head diameter in the stir friction device is 6-14mm, the stirring head depth is 4-11mm, the rotation speed of the stirring head is 100-2000 rpm / min, the forward speed of the stirring head is 10-400mm / min, the pressing amount of the stirring head is 0.2-5mm, and then according to the above-mentioned additive manufacturing, milling and stir friction treatment; repeat the cycle, and finally obtain 20-100 layers of high-strength plastic magnesium alloy components based on additive manufacturing and stir friction.

2. The high-strength plastic magnesium alloy component based on additive manufacturing and stir friction according to claim 1, characterized in that: The magnesium alloy described in step (1) is one of AZ31 magnesium alloy, AZ51 magnesium alloy or ZK61 magnesium alloy.

3. The high-strength plastic magnesium alloy component based on additive manufacturing and stir friction according to claim 1, characterized in that: The magnesium alloy welding wire described in step (2) is one of AZ31 magnesium alloy welding wire, AZ51 magnesium alloy welding wire or ZK61 magnesium alloy welding wire; the shielding 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; the volume ratio of CO2 and argon is 1-5:95-99.

4. The high-strength plastic magnesium alloy component based on additive manufacturing and stir friction according to claim 1, characterized in that: The step (2) is to perform additive manufacturing on a magnesium alloy substrate using a magnesium alloy welding wire having a diameter of 1-3.6 mm.

5. The high-strength plastic magnesium alloy component based on additive manufacturing and stir friction according to claim 1, characterized in that: The diameter of the stirring head in the friction stirring equipment described in step (2) is 7-12 mm, the depth of the stirring head is 4.5-10.5 mm, the rotation speed of the stirring head is 120-1900 rpm, the forward speed of the stirring head is 20-390 mm / min, and the pressing amount of the stirring head is 0.3-4.9 mm.

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