Preparation method suitable for synergistically improving strength and plasticity of magnesium alloy pulsed arc DED component

Abstract

The invention provides a preparation method suitable for synergistically improving the strength and plasticity of a magnesium alloy pulsed arc DED component, which comprises the following steps: carrying out additive manufacturing on a magnesium alloy substrate by adopting a pulse composite cold metal transition welding heat source, and carrying out reciprocating deposition by a welding gun at an interlayer stable upward lifting height in a protective atmosphere environment, and finally, the magnesium alloy component is prepared. The pulse peak current is 150-250 A, the base current is 20-60 A, the pulse frequency is 5-15 Hz, and the pulse ratio is 5 / 1-20 / 1; the current of the cold metal transition welding ranges from 100 A to 150 A, the voltage ranges from 8.0 V to 12.0 V, the arc length is corrected to be 1%-10%, and the inductance is corrected to be 0.1%-0.8. According to the preparation method, the microstructure and internal defect distribution of the magnesium alloy can be improved, so that the grain structure of the obtained DED component is obviously refined, and the strength and plasticity in the construction and horizontal directions are obviously improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electric arc additive manufacturing, in particular to a preparation method suitable for improving the strength and plasticity of magnesium alloy pulse electric arc DED components. BACKGROUND

[0002] Wire-arc directed energy deposition (Wire-arc DED) is an emerging part manufacturing technology that can stack complex three-dimensional parts layer by layer from two-dimensional dimensions, providing a feasible solution for the preparation of large-size complex alloy components.

[0003] Magnesium alloy is an economical and efficient alloy material, which has low density, high specific strength, high damping and high thermal conductivity, and has wide application prospects in many fields. At present, in the Wire-arc DED process of magnesium alloy, a cold metal transfer (CMT) with small heat input is often used as a heat source, which can effectively reduce the heat input in the melting and solidification process of the metal, and obtain a complete equiaxed crystal structure. However, due to the poor flowability of magnesium alloy melt, the porosity of the component is often high under the CMT mode. If the heat input under the CMT mode is simply increased (such as increasing the deposition current), the flowability can be increased to some extent, but the temperature gradient of the melt will also increase, resulting in unstable droplet transfer, more spatter and inclusion, etc.

[0004] The magnesium alloy components prepared by the traditional cold metal transfer welding process often have the defects of many porosities and poor mechanical properties, which greatly limits the promotion and application of the arc additive manufacturing magnesium alloy components. The pulse composite CMT process can be realized by adding and adjusting the pulse frequency current in the conventional CMT arc waveform. The CMT welding technology has the characteristics of small heat input and stable melt transition, and the energy of the pulse current is high, so the combination of the two can greatly increase the melt flowability and the adjustment range of the heat input, improve the problem of grain coarsening caused by too large temperature gradient, and finally achieve the purpose of synergistic improvement of the strength and plasticity of the magnesium alloy DED component. However, in the reports about the pulse composite CMT process for preparing magnesium alloy components, the authors often only focus on the influence of the pulse process parameters on the surface quality and forming accuracy of the components, but ignore the influence of the pulse process parameters on the overall strength and plasticity and isotropy of the magnesium alloy components. For example, the Chinese application patent CN202311209648.5 named "Additive manufacturing process of rare earth magnesium alloy component". At the same time, the magnesium alloy components prepared by the existing aluminum and titanium alloy pulse CMT process often cause the volatilization and burning loss of low-melting-point alloy elements due to the excessive pulse current, thereby generating a large amount of oxide inclusions and porosity defects, which seriously reduces the overall mechanical properties of the magnesium alloy components. In order to expand the application of magnesium alloy, obtain good strength and plasticity matching of the magnesium alloy component, and realize the concept of lightweight and sustainable development, it is necessary to develop a preparation method suitable for the synergistic improvement of the strength and plasticity of the magnesium alloy pulse arc DED component. SUMMARY

[0005] The purpose of the present application is to solve the above problems, and to provide a preparation method suitable for the synergistic improvement of the strength and plasticity of the magnesium alloy pulse arc DED component. This method can improve the microstructure and internal defect distribution of the magnesium alloy, thereby significantly refining the grain structure of the DED component, and improving the strength of the AZ and WE magnesium alloy in the building and horizontal directions by 18-37 MPa and the elongation by 13.3-53.9% MPa.

[0006] It should be noted that in the present application, unless otherwise specified, the specific meaning of "including" involved in the composition limitation and description includes both the open "including", "containing" and the like, and the closed "consisting of", "consisting of" and the like.

[0007] To achieve the above purpose, the technical scheme adopted by the present application is as follows: a preparation method suitable for the synergistic improvement of the strength and plasticity of the magnesium alloy pulse arc DED component, comprising the following steps:

[0008] The pulse composite cold metal transfer welding heat source is used for additive manufacturing on the magnesium alloy substrate. In a protective atmosphere environment, the welding gun is reciprocally deposited by stably lifting upward at a certain height, and finally a magnesium alloy (straight wall) component is prepared;

[0009] The pulse peak current is 150-250 A, the base current is 20-60 A, the pulse frequency is 5-15 Hz, and the pulse ratio is 5 / 1-20 / 1; the cold metal transfer welding current is 100-150 A, the voltage is 8.0-12.0 V, the arc length correction is 1-10%, and the inductance correction is 0.1-0.8.

[0010] Further, the pulse peak current is 150-250 A, the base current is 20-60 A, the pulse frequency is 5-15 Hz, and the pulse ratio is 5 / 1-20 / 1; the cold metal transfer welding current is 100-150 A, the voltage is 8.0-12.0 V, the arc length correction is 1-10%, and the inductance correction is 0.1-0.8. Preferably, the pulse peak current is 200-210 A, the base current is 40-50 A, the pulse frequency is 8-12 Hz, the pulse ratio is 8 / 1-12 / 1, the cold metal transfer welding current is 120-140 A, the voltage is 9-11 V, the arc length correction is 4-6%, and the inductance correction is 0.3-0.5.

[0011] Further, before additive manufacturing, the magnesium alloy substrate is pretreated, then fixed on the workbench (DED workbench), and connected with a heater to ensure the temperature stability of the magnesium alloy substrate; the magnesium alloy wire is installed in the wire feeder and elongated to the welding gun of the robot arm.

[0012] Further, the pretreatment of the magnesium alloy substrate includes but is not limited to polishing and ultrasonic cleaning.

[0013] Further, the magnesium alloy substrate is one of AZ31B, AZ91D and WE43 alloy plates.

[0014] Further, the temperature of the magnesium alloy substrate is 150-250℃.

[0015] Further, the magnesium alloy wire is one of AZ31B, AZ91D and WE43 magnesium alloy wires, and the diameter of the magnesium alloy wire is 0.8-1.6 mm.

[0016] Further, the reciprocating deposition speed is 6-12 mm / s, and the wire feeding speed is 8.0-12.0 m / min.

[0017] Further, the interlayer temperature of the magnesium alloy component is strictly controlled during the entire additive process, and the interlayer temperature of the magnesium alloy component is 90-110℃.

[0018] Further, the welding gun is stably lifted upward by 1-4 mm and the dry elongation is 10-20 mm during the reciprocating deposition process.

[0019] Further, the protective atmosphere is high-purity argon, and the gas flow rate is 18-25 L / min.

[0020] Another object of the present application also discloses a magnesium alloy pulse arc DED component prepared by the above method. The tensile strength in the building direction is 252-285 MPa, the elongation is 13.5-25.4%, the tensile strength in the horizontal direction is 257-288 MPa, and the elongation is 14.8-25.6%,

[0021] The present application is suitable for the preparation method of the magnesium alloy pulse arc DED component with synergistic improvement of strength and plasticity, and has the following advantages compared with the prior art.

[0022] (1) The present application is suitable for the preparation method of the magnesium alloy pulse arc DED component with synergistic improvement of strength and plasticity. A pulse composite cold metal transfer welding heat source is used to connect the high-energy pulse period after the cold metal transfer welding CMT period (CMT and pulse are not synchronized, 5-10 high-energy short-time pulse periods are connected after one CMT time period, then one CMT time period and 5-10 high-energy short-time pulse periods are connected, and so on, so it is called pulse composite CMT, also called CMT+P process), which ensures stable droplet transfer and improves the controllability of additive heat input. Compared with the traditional arc DED magnesium alloy additive process, the pulse arc DED process increases the melt heat input while having higher additive efficiency and material utilization rate.

[0023] (2) The present application is suitable for the preparation method of the magnesium alloy pulse arc DED component with synergistic improvement of strength and plasticity. Specific pulse conditions (pulse current, pulse frequency and pulse ratio parameter range) and cold metal transfer welding conditions (current, voltage, arc length correction and inductance correction) are formulated according to the characteristics of low melting point and poor flowability of magnesium alloy. It is found that if the parameters are lower than the range, the heat input of the additive process will not be enough, resulting in thicker interlayer and more porosity defects. If the parameters are higher than the range, the magnesium alloy will be excessively burned, the oxidation inclusions will be too much, and the grain structure will be coarse due to excessive heat input. In summary, the use of these parameters can effectively increase the flowability of the magnesium alloy melt and the forming quality of the component, control the internal defects of the melt and achieve good interlayer fusion, and the alloy grain structure is obviously refined.

[0024] (3) The present application is suitable for the preparation method of the magnesium alloy pulse arc DED component with synergistic improvement of strength and plasticity. By optimizing and matching the welding machine parameters such as deposition current, deposition speed and wire feeding speed of the cold metal transfer welding CMT period, the melt flowability and stability of the deposited component are effectively promoted, and the interlayer porosity is effectively discharged in time. The magnesium alloy DED component obtained has the advantages of small grain size, few defects and high precision, and the strength and plasticity are synergistically improved. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 schematic diagram of current periodic change for CMT process and CMT+P process;

[0026] Figure 2 physical diagram of AZ31B magnesium alloy DED component obtained from example 1 and comparative example 1;

[0027] Figure 3 metallographic diagram of AZ31B magnesium alloy DED component obtained from example 1;

[0028] Figure 4 metallographic diagram of AZ31B magnesium alloy DED component obtained from comparative example 1;

[0029] Figure 5 schematic diagram of sampling in different directions of magnesium alloy DED components obtained from example and comparative example. DETAILED DESCRIPTION

[0030] The description of the technical features described below is based on representative embodiments, specific examples of the present application, but the present application is not limited to these embodiments, specific examples. It should be noted that:

[0031] Unless otherwise specified, the units used in the specification are international standard units, and the values, value ranges appearing in the present application should be understood as including systematic errors that are inevitable in industrial production.

[0032] In the specification, the numerical range represented by "numerical value A ~ numerical value B" means a range including the end point values A and B.

[0033] In the specification, the numerical range represented by "above" or "below" means a numerical range including the number.

[0034] In the specification, the meaning represented by "may" includes both the meaning of performing a certain process and the meaning of not performing a certain process.

[0035] In the specification, "optional" or "optionally" means that certain substances, components, execution steps, applied conditions, etc. are used or not used.

[0036] In the specification, when "normal temperature" or "room temperature" is used, the temperature can be 15-25℃.

[0037] In the specification, the reagents or instruments not marked with the manufacturer are all conventional products that can be obtained by purchase.

[0038] The present application discloses a preparation method suitable for the synergistic improvement of strength and plasticity of magnesium alloy pulse arc DED components, comprising the following steps:

[0039] (1) draw the model of the metal structure, slice the structure, and generate a motion trajectory, and then import the motion program into the DED control system of the robot arm.

[0040] (2) After pretreatment, the magnesium alloy substrate is fixed on the DED workbench and connected to the heater to ensure the temperature stability of the substrate. The magnesium alloy wire is installed in the wire feeder and elongated to the welding gun of the robot arm.

[0041] (3) A pulse composite cold metal transfer welding heat source is used to set the welding machine process parameters, and the welding gun executes the additive instructions according to the preset program, and the interlayer is stably lifted to a fixed height, and finally a magnesium alloy straight wall structure is obtained through reciprocating deposition. The whole additive process is carried out in a protective atmosphere, and the interlayer temperature of the structure is strictly controlled.

[0042] The magnesium alloy substrate in step (2) is one of AZ31B, AZ91D and WE43 alloy plates.

[0043] The temperature of the substrate in step (2) is 150-250℃.

[0044] The magnesium alloy wire in step (2) is one of AZ31B, AZ91D and WE43 magnesium alloy wires, and the diameter of the magnesium alloy wire is 0.8-1.6mm.

[0045] In step (3), the pulse peak current is 150-250A, the base current is 20-60A, the pulse frequency is 5-15Hz, the pulse ratio is 5 / 1-20 / 1, the cold metal transfer welding current is 100-150A, the voltage is 8.0-12.0V, the arc length correction is 1-10%, and the inductance correction is 0.1-0.8.

[0046] In step (3), the reciprocating deposition speed is 6-12mm / s, and the wire feeding speed is 8.0-12.0m / min.

[0047] In step (3), the interlayer temperature of the structure is 90-110℃.

[0048] In step (3), the welding gun is stably lifted 1-4mm upward between layers during the reciprocating deposition process, and the dry extension is 10-20mm.

[0049] In step (3), the protective atmosphere is high-purity argon, and the gas flow is 18-25L / min.

[0050] The application takes AZ series and WE43 magnesium alloy wires as raw materials, and based on the pulse arc directional energy deposition process, reciprocating deposition is carried out according to the preset trajectory of the layered slice, and finally a magnesium alloy additive component with good forming quality is obtained. The pulse composite cold metal transfer welding heat source is used, on the basis of ensuring stable droplet transition, the controllability of welding heat input is enhanced, the magnesium alloy molten pool fluidity and additive manufacturing efficiency are improved, and the grain structure and precipitate distribution are further improved, compared with the magnesium alloy DED component prepared by the conventional process or aluminum alloy, titanium alloy process, the plasticity of the magnesium alloy DED component is obviously improved.

[0051] The application will be further described in combination with examples.

[0052] Example 1

[0053] In this example, AZ31B magnesium alloy wires with a diameter of 1.2 mm (composition: Mg-3.45Al-0.65Zn-0.32Mn) are used for reciprocating deposition of pulse arc DED components. The specific preparation method includes the following steps:

[0054] (1) A three-dimensional model of the additive structure is constructed using modeling software, and the model is imported into the additive processing software to perform layering and slicing, set the arc striking position of the welding torch, and gradually deposit 120 mm after arc collection. Set the welding torch layer lifting height to 2.0 mm, strike the arc along the upper arc collection position, and gradually deposit the same distance. According to the planned path, reciprocating deposition is performed layer by layer for 40 layers, and finally a straight wall component with a preset height of 80 mm is obtained. The preset additive instructions are imported into the DED control system, and the instructions are run.

[0055] (2) The AZ31B magnesium alloy plate is used as the DED substrate, polished and ultrasonically cleaned, fixed on the workbench, and connected to the heater for constant temperature heating, with a temperature setting of 200℃. The magnesium alloy wire is dried and installed in the wire feeder, and the wire is stretched to the welding torch of the robot arm, and the welding torch angle is adjusted to be perpendicular to the workbench.

[0056] (3) A pulse composite cold metal transfer welding heat source is used, and the mechanical arm welding torch executes the additive instructions according to the preset program, and the parameters of the additive process are set as follows: pulse peak current 205A, base current 45A, pulse frequency 10Hz, pulse ratio 10:1, cold metal transfer welding current 120A, voltage 9.5V, arc length correction 5%, inductance correction 0.4, deposition speed 10.0mm / s, wire feeding speed 9.0m / min, and welding torch dry extension 15mm.

[0057] (4) The reciprocating deposition finally obtains a DED magnesium alloy straight wall component with a preset height, and the entire additive process is carried out under the protection of high-purity argon gas with a flow rate of 20L / min, and the interlayer temperature of the component is controlled at 100℃.

[0058] The AZ series magnesium alloy component prepared in the embodiment has good formability, good melt pool laminar flow, no obvious porosity defects between layers, stable droplet transfer during DED process, and high overall quality of the component.

[0059] Example 2

[0060] In the embodiment, AZ31B magnesium alloy wire with a diameter of 1.2 mm (composition: Mg-3.45Al-0.65Zn-0.32Mn) is used for reciprocating deposition of pulsed arc DED components. The specific preparation method includes the following steps:

[0061] (1) A three-dimensional model of the additive structure is constructed using modeling software, and the model is imported into the additive processing software to perform layer slicing, set the welding gun arc starting position, and gradually deposit 120 mm and then stop the arc. The welding gun interlayer lifting height is set to 2.0 mm, the arc is started along the upper arc stopping position, and the same distance is gradually deposited. According to the planned path, 40 layers are deposited reciprocally, and finally a straight wall component with a preset height of 80 mm is obtained. The preset additive instructions are imported into the DED control system, and the instructions are run.

[0062] (2) The AZ31B magnesium alloy plate is used as the DED substrate, polished and ultrasonically cleaned, fixed on the workbench, and connected to the heater for constant temperature heating, with a temperature setting of 200°C. The magnesium alloy wire is dried and installed in the wire feeder, and the wire is elongated to the welding gun below the robot arm, and the welding gun angle is adjusted to be perpendicular to the workbench.

[0063] (3) The pulsed composite cold metal transfer welding heat source is used, and the mechanical arm welding gun executes the additive instructions according to the preset program. The parameter settings of the additive process are as follows: pulse peak current 205 A, base current 45 A, pulse frequency 10 Hz, pulse ratio 10:1, cold metal transfer welding current 140 A, voltage 10.5 V, arc length correction 5%, inductance correction 0.4, deposition speed 10.0 mm / s, wire feeding speed 10.6 m / min, and welding gun dry extension 15 mm.

[0064] (4) The DED magnesium alloy straight wall component with a preset height is finally obtained through reciprocating deposition. The entire additive process is carried out under high-purity argon protection, with a gas flow rate of 20 L / min, and the interlayer temperature of the component is controlled at 100°C.

[0065] The AZ series magnesium alloy component prepared in the embodiment has good formability, good melt pool laminar flow, no obvious porosity defects between layers, stable droplet transfer during DED process, and high overall quality of the component.

[0066] Example 3

[0067] This embodiment uses AZ91D magnesium alloy wire with a diameter of 1.2 mm (composition: Mg-8.65Al-0.58Zn-0.36Mn) to reciprocating deposit the pulsed arc DED component, the specific preparation method includes the following steps:

[0068] (1) Use modeling software to build a three-dimensional model of the additive structure, import the model into the additive processing software, set the welding gun arc starting position, and gradually deposit 120 mm after arc collection. Set the welding gun layer lifting height to 2.0 mm, arc along the upper arc collection position, and gradually deposit the same distance. According to the planned path, reciprocating deposit 40 layers, and finally obtain a straight wall component with a preset height of 80 mm. Import the preset additive instructions into the DED control system, and wait for the instructions to run.

[0069] (2) AZ91D magnesium alloy plate is used as the DED substrate, which is polished and ultrasonically cleaned and then fixed on the workbench and connected to the heater for constant temperature heating, with a temperature setting of 200°C. The magnesium alloy wire is dried and installed in the wire feeder, and the wire is elongated to the welding gun below the robot arm, and the welding gun angle is adjusted to be perpendicular to the workbench.

[0070] (3) Use pulsed composite cold metal transfer welding heat source, and the mechanical arm welding gun executes the additive instructions according to the preset program, and the parameter settings of the additive process are as follows: pulse peak current 205A, base current 45A, pulse frequency 10Hz, pulse ratio 10:1, cold metal transfer welding current 120A, voltage 9.5V, arc length correction 5%, inductance correction 0.4, deposition speed 10.0mm / s, wire feeding speed 9.0m / min, and welding gun dry elongation 15mm.

[0071] (4) After reciprocating deposition, a DED magnesium alloy straight wall component with a preset height is obtained, and the entire additive process is carried out under high-purity argon protection with a gas flow of 20L / min, and the interlayer temperature of the component is controlled at 100°C.

[0072] The AZ series magnesium alloy component prepared in this embodiment has good formability, good molten pool laminar flow, and no obvious porosity defects between layers, stable droplet transfer during DED process, and high overall quality of the component.

[0073] Example 4

[0074] This embodiment uses AZ91D magnesium alloy wire with a diameter of 1.2 mm (composition: Mg-8.65Al-0.58Zn-0.36Mn) to reciprocating deposit the pulsed arc DED component, the specific preparation method includes the following steps:

[0075] (1) The three-dimensional model of the additive structure is constructed by modeling software, the model is imported into the additive processing software for slicing, the arc striking position of the welding torch is set, and the arc is collected after 120 mm is gradually deposited. The layer lifting height of the welding torch is set to 2.0 mm, the arc is struck along the arc collection position of the upper layer, and the same distance is gradually deposited. According to the planned path, 40 layers are deposited layer by layer, and finally a straight wall component with a preset height of 80 mm is obtained. The preset additive instruction is imported into the DED control system, and the instruction is run.

[0076] (2) The AZ91D magnesium alloy plate is polished and ultrasonically cleaned, then fixed on the workbench and connected to the heater for constant temperature heating, and the temperature is set to 200℃. The magnesium alloy wire is dried and installed in the wire feeder, and the wire is stretched to the welding torch of the robot arm, and the welding torch angle is adjusted to be perpendicular to the workbench.

[0077] (3) The pulse composite cold metal transfer welding heat source is used, the mechanical arm welding torch executes the additive instruction according to the preset program, and the parameter settings of the additive process are as follows: pulse peak current 205A, base current 45A, pulse frequency 10Hz, pulse ratio 10:1, cold metal transfer welding current 140A, voltage 10.5V, arc length correction 5%, inductance correction 0.4, deposition speed 10.0mm / s, wire feeding speed 10.6m / min, and welding torch dry extension 15mm.

[0078] (4) The DED magnesium alloy straight wall component with a preset height is finally obtained by reciprocating deposition, the whole additive process is carried out under the protection of high-purity argon gas with a flow rate of 20L / min, and the interlayer temperature of the component is controlled to 100℃.

[0079] The AZ series magnesium alloy component prepared in this embodiment has good formability, good molten pool laminar flow and no obvious porosity defects between layers, the droplet transfer is stable during the DED process, and the overall quality of the component is high.

[0080] Example 5

[0081] In this embodiment, a WE43 magnesium alloy wire with a diameter of 1.2mm (composition: Mg-4.05Y-2.15Nd-0.7Gd-0.46Zr) is used for the reciprocating deposition of pulse arc DED components, and the specific preparation method includes the following steps:

[0082] (1) The three-dimensional model of the additive structure is constructed by modeling software, the model is imported into the additive processing software for slicing, the arc striking position of the welding torch is set, and the arc is collected after 120 mm is gradually deposited. The layer lifting height of the welding torch is set to 2.0 mm, the arc is struck along the arc collection position of the upper layer, and the same distance is gradually deposited. According to the planned path, 40 layers are deposited layer by layer, and finally a straight wall component with a preset height of 80 mm is obtained. The preset additive instruction is imported into the DED control system, and the instruction is run.

[0083] (2) WE43 magnesium alloy plate as DED substrate, after polishing and ultrasonic cleaning, fixed on the workbench, and connected to the heater for constant temperature heating, the temperature was set to 200°C. The magnesium alloy wire was dried and installed in the wire feeder, and the wire was extended to the welding gun below the robot arm, and the welding gun angle was adjusted vertically to the workbench.

[0084] (3) The pulsed composite cold metal transfer welding heat source was used, and the mechanical arm welding gun executed the additive instructions according to the preset program, and the parameters of the additive process were set as follows: pulse peak current 205A, base current 45A, pulse frequency 10Hz, pulse ratio 10:1, cold metal transfer welding current 120A, voltage 9.5V, arc length correction 5%, inductance correction 0.4, deposition speed 10.0mm / s, wire feeding speed 9.0m / min, and welding gun dry extension 15mm.

[0085] (4) The DED magnesium alloy straight wall structure with a preset height was finally obtained by reciprocating deposition, and the whole additive process was carried out under the protection of high-purity argon gas with a flow rate of 20L / min, and the interlayer temperature of the structure was controlled at 100°C.

[0086] Comparative Example 1

[0087] This comparative example uses AZ31B magnesium alloy wire with a diameter of 1.2mm (composition: Mg-3.45Al-0.65Zn-0.32Mn) for arc DED structure reciprocating deposition, and the specific preparation method includes the following steps:

[0088] (1) A three-dimensional model of the additive structure was constructed using modeling software, and the model was imported into the additive processing software to slice it, set the welding gun arc starting position, and gradually deposit 120mm and then stop the arc. The welding gun interlayer lifting height was set to 3.0mm, the arc was started along the upper arc stopping position, and the same distance was gradually deposited. According to the planned path, 26 layers were reciprocally deposited layer by layer, and finally a straight wall structure with a preset height of 78mm was obtained. The preset additive instructions were imported into the DED control system, and the instructions were run.

[0089] (2) AZ31B magnesium alloy plate as DED substrate, after polishing and ultrasonic cleaning, fixed on the workbench, and connected to the heater for constant temperature heating, the temperature was set to 200°C. The magnesium alloy wire was dried and installed in the wire feeder, and the wire was extended to the welding gun below the robot arm, and the welding gun angle was adjusted vertically to the workbench.

[0090] (3) The cold metal transfer welding heat source was used, and the mechanical arm welding gun executed the additive instructions according to the preset program, and the parameters of the additive process were set as follows: cold metal transfer welding current 120A, voltage 11.5V, deposition speed 10.0mm / s, arc length correction 5%, inductance correction 0.4, wire feeding speed 9.4m / min, and welding gun dry extension 15mm.

[0091] (4) After reciprocating deposition, a DED magnesium alloy straight wall component with a preset height is obtained. The entire additive process is carried out under the protection of high-purity argon gas with a gas flow of 20 L / min, and the interlayer temperature of the component is controlled at 135°C.

[0092] Comparative Example 2

[0093] This comparative example uses AZ91D magnesium alloy wire with a diameter of 1.2 mm (composition: Mg-3.45Al-0.65Zn-0.32Mn) for reciprocating deposition of arc DED components. The specific preparation method includes the following steps:

[0094] (1) A three-dimensional model of the additive structure is constructed using modeling software, and the model is imported into the additive processing software to slice it, set the welding gun arc starting position, and gradually deposit 120 mm after arc collection. Set the welding gun interlayer lifting height to 3.0 mm, arc along the upper arc collection position, and gradually deposit the same distance. According to the planned path, 26 layers are reciprocally deposited layer by layer, and finally a straight wall component with a preset height of 78 mm is obtained. The preset additive instructions are imported into the DED control system, and the instructions are run.

[0095] (2) The AZ91D magnesium alloy plate is used as the DED substrate, which is polished and ultrasonically cleaned and then fixed on the workbench and connected to the heater for constant temperature heating, with a temperature setting of 200°C. The magnesium alloy wire is dried and installed in the wire feeder, and the wire is stretched to the robot arm welding gun below, and the welding gun angle is adjusted to be perpendicular to the workbench.

[0096] (3) A cold metal transfer welding heat source is used, and the mechanical arm welding gun executes the additive instructions according to the preset program, and the additive process parameters are set as follows: cold metal transfer welding current 120 A, voltage 11.5 V, arc length correction 5%, inductance correction 0.4, deposition speed 10.0 mm / s, wire feeding speed 9.4 m / min, and welding gun dry extension 15 mm.

[0097] (4) After reciprocating deposition, a DED magnesium alloy straight wall component with a preset height is obtained. The entire additive process is carried out under the protection of high-purity argon gas with a gas flow of 20 L / min, and the interlayer temperature of the component is controlled at 135°C.

[0098] Comparative Example 3

[0099] This example uses WE43 magnesium alloy wire with a diameter of 1.2 mm (composition: Mg-4.05Y-2.15Nd-0.7Gd-0.46Zr) for reciprocating deposition of pulsed arc DED components. The specific preparation method includes the following steps:

[0100] (1) The three-dimensional model of the additive structure is constructed by modeling software, and the model is imported into the additive processing software for layer slicing, the arc striking position of the welding gun is set, and the arc is collected after 120 mm is gradually deposited. The layer lifting height of the welding gun is set to 3.0 mm, the arc is struck along the arc collection position of the upper layer, and the same distance is gradually deposited. According to the planned path, 26 layers are deposited layer by layer, and finally a straight wall wall component with a preset height of 78 mm is obtained. The preset additive instruction is imported into the DED control system, and the instruction is run.

[0101] (2) The WE43 magnesium alloy plate is used as the DED substrate, is polished and ultrasonically cleaned, is fixed on the workbench, and is connected with the heater for constant temperature heating, and the temperature is set to 200℃. The magnesium alloy wire is dried, is installed in the wire feeder, is elongated to the welding gun below the robot arm, and the welding gun angle is adjusted to be perpendicular to the workbench.

[0102] (3) The cold metal transfer welding heat source is used, the mechanical arm welding gun executes the additive instruction according to the preset program, and the parameter settings of the additive process are as follows: cold metal transfer welding current 120A, voltage 9.5V, arc length correction 5%, inductance correction 0.4, deposition speed 10.0mm / s, wire feeding speed 9.0m / min, and welding gun dry elongation 15mm.

[0103] (4) The DED magnesium alloy straight wall wall component with a preset height is finally obtained through reciprocating deposition, the whole additive process is carried out under the protection of high-purity argon gas with a flow rate of 20L / min, and the interlayer temperature of the component is controlled to be 135℃.

[0104] Comparative Example 4

[0105] In this example, AZ31B magnesium alloy wire with a diameter of 1.2mm (composition: Mg-3.45Al-0.65Zn-0.32Mn) is used for reciprocating deposition of pulsed arc DED components, and the specific preparation method comprises the following steps:

[0106] (1) The three-dimensional model of the additive structure is constructed by modeling software, and the model is imported into the additive processing software for layer slicing, the arc striking position of the welding gun is set, and the arc is collected after 120 mm is gradually deposited. The layer lifting height of the welding gun is set to 3.0 mm, the arc is struck along the arc collection position of the upper layer, and the same distance is gradually deposited. According to the planned path, 26 layers are deposited layer by layer, and finally a straight wall wall component with a preset height of 78 mm is obtained. The preset additive instruction is imported into the DED control system, and the instruction is run.

[0107] (2) The WE43 magnesium alloy plate is used as the DED substrate, is polished and ultrasonically cleaned, is fixed on the workbench, and is connected with the heater for constant temperature heating, and the temperature is set to 200℃. The magnesium alloy wire is dried, is installed in the wire feeder, is elongated to the welding gun below the robot arm, and the welding gun angle is adjusted to be perpendicular to the workbench.

[0108] (3) The pulsed composite cold metal transfer welding heat source was used, and the mechanical arm welding torch executed the additive instructions according to the preset program. The parameter settings of the additive process were as follows: pulse peak current 300 A, base current 75 A, pulse frequency 25 Hz, pulse ratio 25:1, cold metal transfer welding current 140 A, voltage 10.5 V, arc length correction 5%, inductance correction 0.4, deposition speed 12.5 mm / s, wire feeding speed 10.6 m / min, and welding torch dry extension 15 mm.

[0109] (4) The DED magnesium alloy straight wall component of the preset height was finally obtained through reciprocating deposition. The entire additive process was carried out under the protection of high-purity argon gas with a gas flow of 20 L / min. The interlayer temperature of the component was controlled at 125 DEG C.

[0110] Comparative Example 5

[0111] In this embodiment, the AZ91D magnesium alloy wire with a diameter of 1.2 mm (composition: Mg-8.65Al-0.58Zn-0.36Mn) was used for the reciprocating deposition of the pulsed arc DED component. The specific preparation method included the following steps:

[0112] (1) The three-dimensional model of the additive structure was constructed using modeling software. The model was imported into the additive processing software to slice it, set the welding torch arc striking position, and gradually deposit 120 mm to collect the arc. The welding torch interlayer lifting height was set to 2.0 mm, the arc was struck along the upper arc collection position, and the same distance was gradually deposited. According to the planned path, 40 layers were reciprocally deposited layer by layer, and finally a straight wall component with a preset height of 80 mm was obtained. The preset additive instructions were imported into the DED control system, and the instructions were run.

[0113] (2) The AZ91D magnesium alloy plate was used as the DED substrate, which was polished and ultrasonically cleaned, then fixed on the workbench and connected to the heater for constant temperature heating, with the temperature set to 200 DEG C. The magnesium alloy wire was dried and installed in the wire feeder, and the wire was extended to the robot arm welding torch. The welding torch angle was adjusted to be perpendicular to the workbench.

[0114] (3) The pulsed composite cold metal transfer welding heat source was used, and the mechanical arm welding torch executed the additive instructions according to the preset program. The parameter settings of the additive process were as follows: pulse peak current 300 A, base current 75 A, pulse frequency 25 Hz, pulse ratio 25:1, cold metal transfer welding current 140 A, voltage 10.5 V, arc length correction 5%, inductance correction 0.4, deposition speed 12.5 mm / s, wire feeding speed 10.6 m / min, and welding torch dry extension 15 mm.

[0115] (4) The DED magnesium alloy straight wall component of a preset height is finally obtained by reciprocating deposition. The whole additive process is carried out under the protection of high-purity argon gas, the gas flow is 20 L / min, and the interlayer temperature of the component is controlled to be 100℃.

[0116] Examples 1, 2, 3, 4 and 5 are pulse arc DED processes, Comparative Examples 1, 2 and 3 are conventional DED processes, and Comparative Examples 4 and 5 are pulse arc DED processes outside the parameter range of the present patent. Figure 1 The schematic diagram of the periodic change of current for the cold metal transfer CMT process and the pulse composite cold metal transfer CMT+P process of the present application. Within a certain frequency and peak current range, the introduction of the pulse arc can increase the oscillation effect of the molten pool, and at the same time, the greater current and heat input can increase the arc force and Marangoni convection suffered by the molten pool, further increasing the flowability of the molten pool and promoting grain structure refinement. As shown in Figure 2 、 3 and 4, the interlayer of the pulse arc DED component is thinner and the formability is better, so the cooling speed during solidification of the molten pool is faster, and the grain structure is more fine compared with the conventional DED process.

[0117] The magnesium alloy components of Examples 1-5 and Comparative Examples 1-4 are tested respectively, and the test methods and results are as follows:

[0118] As shown in Figure 5The mechanical properties were tested in the building direction (BD) and the horizontal direction (TD) respectively, and the final results are shown in Table 1. Compared with the conventional DED process of Comparative Example 1, the tensile strength of the AZ31B magnesium alloy components of Example 1 and Example 2 in the BD direction was increased by 31 MPa and 23 MPa respectively, and the elongation was increased by 32.6% and 35.8% respectively, and in the TD direction, the tensile strength was increased by 27 MPa and 19 MPa respectively, and the elongation was increased by 29.2% and 31.3% respectively. Compared with the conventional DED process of Comparative Example 2, the tensile strength of the AZ91D magnesium alloy components of Example 3 and Example 4 in the BD direction was increased by 27 MPa and 21 MPa respectively, and the elongation was increased by 17.1% and 13.3% respectively, and in the TD direction, the tensile strength was increased by 33 MPa and 30 MPa respectively, and the elongation was increased by 16.7% and 17.9% respectively. At the same time, compared with the conventional DED process of Comparative Example 3, the tensile strength of the WE43 magnesium alloy component of Example 5 in the BD direction was increased by 23 MPa, and the elongation was increased by 42.1%, and in the TD direction, the tensile strength was increased by 26 MPa, and the elongation was increased by 31%. Compared with the pulse arc DED process outside the parameter range of Comparative Example 4, the tensile strength of the AZ31B magnesium alloy components of Example 1 and Example 2 in the BD direction was increased by 37 MPa and 29 MPa respectively, and the elongation was increased by 50.3% and 53.9% respectively, and in the TD direction, the tensile strength was increased by 36 MPa and 28 MPa respectively, and the elongation was increased by 50% and 52.4% respectively. Compared with the pulse arc DED process outside the parameter range of Comparative Example 5, the tensile strength of the AZ91B magnesium alloy components of Example 3 and Example 4 in the BD direction was increased by 24 MPa and 18 MPa respectively, and the elongation was increased by 19.4% and 15.5% respectively, and in the TD direction, the tensile strength was increased by 28 MPa and 25 MPa respectively, and the elongation was increased by 23.5% and 24.8% respectively.

[0119] In summary, by using the optimized pulse composite cold metal transfer welding process in the DED process of AZ series magnesium alloy and rare earth magnesium alloy, the magnesium alloy component obtained has refined grain structure, and the strength and plasticity are synergistically improved, which is low in cost and simple in process, and can further expand the application of magnesium alloy additive components.

[0120] Table 1 tensile strength and elongation of each example and comparative example in the BD and TD directions

[0121]

[0122] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and are not intended to limit the present application; although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions recorded in the above embodiments can be modified, or some or all of the technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A preparation method suitable for magnesium alloy pulse arc DED component strength and plasticity synergistic improvement, characterized in that, It comprises the following steps: The method comprises the following steps: The pulse peak current is 150-250 A, the base current is 20-60 A, the pulse frequency is 5-15 Hz, and the pulse ratio is 5 / 1-20 / 1; the cold metal transfer welding current is 100-150 A, the voltage is 8.0-12.0 V, the arc length correction is 1-10%, and the inductance correction is 0.1-0.

8.

2. The method according to claim 1, characterized in that, Before the additive manufacturing, the magnesium alloy substrate is pretreated, then fixed on the workbench and connected to the heater to ensure the temperature stability of the magnesium alloy substrate; the magnesium alloy wire is installed in the wire feeder and elongated to the robot arm welding torch.

3. The method according to claim 2, characterized in that, The pretreatment of the magnesium alloy substrate is polishing and ultrasonic cleaning.

4. The method according to claim 1, wherein, The magnesium alloy substrate is one of AZ31B, AZ91D and WE43 alloy plates. The temperature of the magnesium alloy substrate is 150-250 DEG C.

5. The method according to claim 1, wherein, The magnesium alloy wire is one of AZ31B, AZ91D and WE43 magnesium alloy wires. The diameter of the magnesium alloy wire is 0.8-1.6 mm.

6. The method according to claim 1, wherein, The reciprocating deposition speed is 6-12 mm / s, and the wire feeding speed is 8.0-12.0 m / min.

7. The method according to claim 1, wherein the method is characterized by, The interlayer temperature of the magnesium alloy component is 90-110 DEG C.

8. The method according to claim 1, wherein the method is characterized by, During the reciprocating deposition process, the welding torch is stably lifted upward by 1-4 mm, and the dry elongation is 10-20 mm.

9. The method according to claim 1, wherein the method is characterized by, The protective atmosphere is high-purity argon. The gas flow is 18-25 L / min.

10. A magnesium alloy pulsed arc DED component, characterized by, The magnesium alloy component is prepared by the method of any one of claims 1-9.

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