Process for forming Mg-9. 2Gd-3.2 Y-2Zn-0.4 Zr alloy through hammering auxiliary cold metal transition additive manufacturing technology

Abstract

The invention relates to a process for forming an Mg-9. 2Gd-3.2 Y-2Zn-0.4 Zr alloy by utilizing a hammering auxiliary cold metal transition additive manufacturing technology, and belongs to the field of metal material process forming. The process comprises the following steps of substrate preheating, electric arc additive forming and weld bead hammering. According to the process, the Mg-9. 2Gd-3.2 Y-2Zn-0.4 Zr wt% alloy which is fine and uniform in structure and low in residual stress is prepared through CMT electric arc welding equipment, hammering equipment and substrate preheating equipment, and the Mg-9. 2Gd-3.2 Y-2Zn-0.4 Zr wt% alloy is used for improving the mechanical property of a formed part, prolonging the fatigue life of the part, reducing internal defects of the formed part, reducing the residual stress of the formed part and widening the application range of the heavy rare earth magnesium alloy.

Description

Technical Field

[0001] The present invention belongs to the field of metal material process forming, and particularly relates to a process for forming Mg-9.2Gd-3.2Y-2Zn-0.4Zr wt% alloy by using a hammer-assisted cold metal transfer additive manufacturing technology. Background Art

[0002] Mg-9.2Gd-3.2Y-2Zn-0.4Zr wt% alloy is a high-performance magnesium alloy, which is well-known for its low density, high specific strength and excellent corrosion resistance, and is suitable for the aerospace and automotive industries. However, this alloy also has some disadvantages, such as low plasticity, high residual stress in the formed parts and easy fracture, which pose challenges to the processing of this alloy. When the traditional cold metal transfer process is used to form such complex alloys, it may lead to internal defects in the material, such as pores and cracks, as well as the problem of non-uniform microstructure. These defects limit the application of the alloy, especially in the fields with high requirements for material properties. The existing demands focus on improving the mechanical properties and forming quality of the alloy while reducing processing defects. The hammer-assisted cold metal transfer additive manufacturing technology significantly improves the density of the material and the uniformity of the microstructure by applying hammer vibration during the deposition process. This process reduces the formation of pores and cracks and improves the comprehensive properties of the material. The hammer-assisted cold metal transfer additive manufacturing technology not only overcomes the disadvantages of the traditional cold metal transfer process, but also improves the forming ability of the alloy, significantly reduces the residual stress of the formed parts and increases the yield rate of the formed parts. Therefore, the hammer-assisted cold metal transfer additive manufacturing technology shows significant advantages in meeting the processing requirements of high-performance magnesium alloys and promotes its application in high-tech fields. However, due to the low plasticity of Mg-9.2Gd-3.2Y-2Zn-0.4Zr wt% alloy, the weld bead is extremely easy to crack and break during the hammering process, which will directly restrict the application of this technology in the field of Mg-9.2Gd-3.2Y-2Zn-0.4Zr wt% alloy. Summary of the Invention

[0003] The inventors found that when the preheating temperature and process parameters are reasonably controlled, the microstructure of the Mg-9.2Gd-3.2Y-2Zn-0.4Zr wt% alloy can be regulated, the plasticity of the Mg-9.2Gd-3.2Y-2Zn-0.4Zr wt% alloy can be improved to avoid cracking of the formed parts during the hammering process, and at the same time, the part performance can be improved. Therefore, the purpose of the present invention is to provide a process for forming the Mg-9.2Gd-3.2Y-2Zn-0.4Zr wt% alloy by using the hammer-assisted cold metal transfer additive manufacturing technology. This process uses a CMT arc welding device, a hammering device, and a substrate preheating device to prepare the Mg-9.2Gd-3.2Y-2Zn-0.4Zr wt% alloy with fine and uniform microstructure and low residual stress, which is used to improve the mechanical properties of the formed parts, increase the fatigue life of the parts, reduce the internal defects of the formed parts, reduce the residual stress of the formed parts, and expand the application range of the heavy rare earth magnesium alloy.

[0004] To achieve the above object, the technical solution adopted by the present invention is as follows: A process for forming the Mg-9.2Gd-3.2Y-2Zn-0.4Zr wt% alloy by using the hammer-assisted cold metal transfer additive manufacturing technology, comprising the following steps: Step 1, substrate preheating (1) Place the cast aluminum adjustable heating plate on the workbench, and place the additive manufacturing substrate above the cast aluminum adjustable heating plate; (2) Connect the temperature control device to the cast aluminum adjustable heating plate, and contact the temperature detection head with the upper surface of the substrate; (3) Set the substrate preheating temperature; (4) When the temperature detection head shows that the temperature reaches a certain temperature, use a wire brush to remove the oxide layer in the welding path area; (5) When the temperature detection head shows that the temperature reaches the set temperature, use a fastening structure to fix the substrate and the heating plate together on the workbench, and finally turn off the cast aluminum adjustable heating plate; Step 2, arc additive forming (1) Use modeling software to establish a three-dimensional model, slice the model and plan the path, and set the welding speed and interlayer cooling time; (2) Use the process parameter package suitable for magnesium alloys and correct the current, voltage, and wire feeding speed during the welding process; (3) Install the Mg-9.2Gd-3.2Y-2Zn-0.4Zr wt% alloy wire with a diameter of 1.2 mm into the wire feeding device; (4) Use argon as the shielding gas and set the gas feeding speed; (5) After each layer of additive forming is completed, return the welding torch to the initial position to avoid collision with the hammer head; Step 3, hammer the weld bead (1)Set the hammering speed, piston stroke, and rivet size; (2)Perform hammering immediately after one layer of additive forming and complete hammering within the interlayer cooling time; (3)After hammering, use a wire brush to clean the oxide and residue on the surface of the weld bead; (4)After forming, cool to room temperature in an air environment.

[0005] Furthermore, in step one, the preheating temperature of the substrate set is 260°C - 350°C.

[0006] Furthermore, in step one, when the temperature detection head shows that the temperature reaches a certain temperature, it is 10 - 20°C lower than the set preheating temperature of the substrate.

[0007] Furthermore, in step two, the welding speed is 10 - 20 mm / s.

[0008] Furthermore, in step two, the interlayer cooling time is 100 - 150 s.

[0009] Furthermore, in step two, the current is 93 - 160 A and the voltage is 11.7 - 13 V.

[0010] Furthermore, in step two, the wire feeding speed is 10 - 14 m / min.

[0011] Furthermore, in step two, the gas feeding speed is 15 - 35 L / min.

[0012] Furthermore, in step three, the hammering speed is 1740 bpm.

[0013] Furthermore, in step three, the piston stroke is 77.8 mm.

[0014] Furthermore, in step three, the rivet size is 4.8 mm.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The forming process of the present invention is simple, the preparation materials are relatively common, the cost is low, the price of the equipment used is low, and the preparation time is short, which can save a large amount of time and cost.

[0016] 2. The present invention adopts hammering-assisted cold metal transfer additive manufacturing, which has high deposition efficiency, stable quality of each part of the part, can form various complex parts, and can be precisely controlled by a computer for the robotic arm.

[0017] 3. By setting appropriate process parameters, the present invention can obtain rare earth magnesium alloy materials with desired low residual stress and few defects. That is, under suitable processes, through hammering-assisted cold metal transfer additive manufacturing, the microcracks and pores of the formed parts can be closed, the mechanical properties of the materials can be improved, and at the same time, the residual stress of the formed parts can be reduced, avoiding cracking caused by residual stress.

[0018] 4. By controlling the preheating temperature of the substrate, the heat input power, and the interlayer cooling time, the present invention reduces the activation conditions of the cylindrical and conical slip systems of the Mg-9.2Gd-3.2Y-2Zn-0.4Zr wt% alloy, promotes the activation of multiple slip systems, improves the plasticity of the formed parts, and avoids cracking of the formed parts during the hammering process. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 SEM micrograph of the micro-porosity distribution of the Mg-9.2Gd-3.2Y-2Zn-0.4Zr wt% alloy formed by CMT arc without using the process of the present invention.

[0020] Figure 2 SEM macro-graph of the macro-porosity distribution of the Mg-9.2Gd-3.2Y-2Zn-0.4Zr wt% alloy formed by CMT arc without using the process of the present invention.

[0021] Figure 3 SEM micrograph of the microstructure distribution of the Mg-9.2Gd-3.2Y-2Zn-0.4Zr wt% alloy formed by CMT arc without using the process of the present invention.

[0022] Figure 4 SEM micrograph and macro-graph of the micro-porosity distribution of the Mg-9.2Gd-3.2Y-2Zn-0.4Zr wt% alloy formed by CMT arc using the process of the present invention in Example 1 of the present invention.

[0023] Figure 5 SEM micrograph of the microstructure distribution of the Mg-9.2Gd-3.2Y-2Zn-0.4Zr wt% alloy formed by CMT arc using the process of the present invention in Example 1 of the present invention.

[0024] Figure 6 SEM micrograph and macro-graph of the micro-porosity distribution of the Mg-9.2Gd-3.2Y-2Zn-0.4Zr wt% alloy formed by CMT arc using the process of the present invention in Example 2 of the present invention.

[0025] Figure 7 SEM micrograph of the microstructure distribution of the Mg-9.2Gd-3.2Y-2Zn-0.4Zr wt% alloy formed by CMT arc using the process of the present invention in Example 2 of the present invention. Specific Embodiments

[0026] The technical solutions and effects of the present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but the protection scope of the present invention is not limited thereto.

[0027] Comparative Example 1 The specific steps for forming a Mg-9.2Gd-3.2Y-2Zn-0.4Zr wt% alloy by CMT arc forming without using the process of the present invention in this comparative example are as follows: (1) Use modeling software to establish a three-dimensional model, slice the model and plan the path, and set the welding speed to 10 mm / s and the interlayer cooling time to 100 s; (2) Use a process parameter package suitable for magnesium alloys, with a current of 100 A, a voltage of 12 V, and a wire feeding speed of 10 m / min during the welding process; (3) Install a Mg-9.2Gd-3.2Y-2Zn-0.4Zr wt% alloy wire with a diameter of 1.2 mm into the wire feeding device; (4) Use argon as the shielding gas and set the gas feeding speed to 20 L / min; (5) After each layer of additive forming is completed, return the welding torch to the initial position to avoid collision with the hammer head; The SEM images of the micro-porosity distribution, macro-porosity distribution, and microstructural distribution of the Mg-9.2Gd-3.2Y-2Zn-0.4Zr wt% alloy in this comparative example are as Figures 1 - 3 shown. A large number of micro-porosities with a size of 10 - 20 microns are generated in the formed part, and huge macro-porosities appear inside the molten pool. Using a scanning electron microscope to observe the microstructure at a magnification of 300 times, it is found that the grain size in this comparative example is coarse, with an average grain size of 27 microns, and the amount of the second phase is small. Example 1

[0028] A process for forming a Mg-9.2Gd-3.2Y-2Zn-0.4Zr wt% alloy by using a hammer-assisted cold metal transfer additive manufacturing technique, comprising the following steps: Step 1, Substrate Preheating (1) Place the cast aluminum adjustable heating plate on the workbench, and place the additive substrate above the cast aluminum adjustable heating plate; (2) Connect the temperature control device to the cast aluminum adjustable heating plate, and contact the temperature detection head with the upper surface of the substrate; (3) Set the substrate preheating temperature to 260 °C; (4) When the temperature detection head shows that the temperature reaches 250 °C, use a wire brush to remove the oxide layer in the welding path area; (5) When the temperature detected by the temperature probe reaches the set temperature, use the fastening structure to fix the substrate and the heating plate together on the workbench, and finally close the cast aluminum adjustable heating plate; Step 2, arc additive manufacturing (1) Use modeling software to establish a 3D model, slice the model and perform path planning, set the welding speed to 15 mm / s and the interlayer cooling time to 100 s; (2) Use the process parameter package suitable for magnesium alloy and correct the current of 100 A, voltage of 12 V and wire feeding speed of 10 m / min during the welding process; (3) Install the Mg-9.2Gd-3.2Y-2Zn-0.4Zr wt% alloy wire with a diameter of 1.2 mm into the wire feeding equipment; (4) Use argon as the shielding gas and set the gas feeding speed to 20 L / min; (5) After each layer of additive manufacturing is completed, return the welding torch to the initial position to avoid collision with the hammer head; Step 3, hammer the weld bead (1) Set the hammering speed to 1740 bpm, the piston stroke to 77.8 mm, and the rivet size to 4.8 mm; (2) Hammer immediately after one layer of additive manufacturing is completed and finish hammering within the interlayer cooling time; (3) After hammering, use a wire brush to clean the oxide and residue on the surface of the weld bead; (4) After forming, cool to room temperature in an air environment.

[0029] Figure 4 This is the SEM image of the macroscopic and microscopic pore distribution of the Mg-9.2Gd-3.2Y-2Zn-0.4Zr wt% alloy formed in Example 1 of the present invention. Compare the microscopic pore distribution Figure 1 and the macroscopic pore distribution Figure 2 By comparison, it can be found that all the macroscopic and microscopic pores of the Mg-9.2Gd-3.2Y-2Zn-0.4Zr wt% alloy formed in Example 1 of the present invention are closed and disappear after hammering forming, and the macroscopic and microscopic defects of the material are significantly reduced. Figure 5 This is the SEM image of the microscopic structure distribution of the Mg-9.2Gd-3.2Y-2Zn-0.4Zr wt% alloy formed in Example 1 of the present invention. Compare the microscopic structure distribution Figure 3, through comparison, it can be found that the microstructure of the formed Mg-9.2Gd-3.2Y-2Zn-0.4Zr wt% alloy in Example 1 of the present invention is finer, and the grain size is significantly reduced to 12.61 microns. The microstructure of the formed Mg-9.2Gd-3.2Y-2Zn-0.4Zr wt% alloy in Example 1 of the present invention undergoes sufficient recrystallization during high-temperature plastic deformation, releasing residual stress on the one hand and significantly refining grains on the other hand, thereby ultimately improving the mechanical properties of the formed material. Example 2

[0030] A process for forming Mg-9.2Gd-3.2Y-2Zn-0.4Zr wt% alloy by using hammer-assisted cold metal transfer additive manufacturing technology, comprising the following steps: Step 1, substrate preheating (1) Place the cast aluminum adjustable heating plate on the workbench, and place the additive manufacturing substrate above the cast aluminum adjustable heating plate; (2) Connect the temperature control device to the cast aluminum adjustable heating plate, and contact the temperature detection head with the upper surface of the substrate; (3) Set the substrate preheating temperature to 280°C; (4) When the temperature detection head shows that the temperature reaches 260°C, use a wire brush to remove the oxide layer in the welding path area; (5) When the temperature detection head shows that the temperature reaches the set temperature, use a fastening structure to fix the substrate and the heating plate together on the workbench, and finally turn off the cast aluminum adjustable heating plate; Step 2, arc additive manufacturing (1) Use modeling software to establish a three-dimensional model, slice the model and plan the path, and set the welding speed to 10 mm / s and the interlayer cooling time to 120 s; (2) Use the process parameter package suitable for magnesium alloy and correct the current of 160 A, voltage of 13 V and wire feeding speed of 14 m / min during the welding process; (3) Install the Mg-9.2Gd-3.2Y-2Zn-0.4Zr wt% alloy wire with a diameter of 1.2 mm into the wire feeding device; (4) Use argon as the shielding gas and set the gas feeding speed to 25 L / min; (5) After each layer of additive manufacturing is completed, return the welding torch to the initial position to avoid collision with the hammer head; Step 3, hammer the weld bead (1) Set the hammering speed to 1740 bpm, the piston stroke to 77.8 mm, and the rivet size to 4.8 mm; (2) Hammer immediately after one layer of additive manufacturing is completed, and complete the hammering within the interlayer cooling time; (3) After hammering, use a wire brush to clean the oxide and residue on the surface of the weld bead; (4) After forming, cool it to room temperature in an air environment.

[0031] Figure 6 This is the SEM image of the macroscopic and microscopic pore distribution of the formed Mg-9.2Gd-3.2Y-2Zn-0.4Zr wt% alloy in Example 2 of the present invention. Compare the microscopic pore distribution without using the process of the present invention Figure 1 and the macroscopic pore distribution Figure 2 By comparison, it can be found that all the macroscopic and microscopic pores of the formed Mg-9.2Gd-3.2Y-2Zn-0.4Zr wt% alloy in Example 2 of the present invention are closed and disappear after hammering forming, and the macroscopic and microscopic defects of the material are significantly reduced. Figure 7 This is the SEM image of the microscopic structure distribution of the formed Mg-9.2Gd-3.2Y-2Zn-0.4Zr wt% alloy in Example 2 of the present invention. Compare the microscopic structure distribution without using the process of the present invention Figure 3 By comparison, it can be found that the microscopic structure of the formed Mg-9.2Gd-3.2Y-2Zn-0.4Zr wt% alloy in Example 2 of the present invention is finer, and the grain size is significantly reduced to 15.13 microns. During the high-temperature plastic deformation process, the microscopic structure of the formed Mg-9.2Gd-3.2Y-2Zn-0.4Zr wt% alloy in Example 2 of the present invention undergoes sufficient recrystallization, which on the one hand releases the residual stress, and on the other hand significantly refines the grains, thus ultimately improving the mechanical properties of the formed material.

[0032] It should be noted that, comparing the SEM image of the microscopic structure distribution of the formed Mg-9.2Gd-3.2Y-2Zn-0.4Zr wt% alloy in Example 1 of the present invention, since the heat input in Example 2 of the present invention is higher than that in Example 1 of the present invention, the microscopic structure Figure 7 in Example 2 of the present invention Figure 5 is coarser than that in Example 1 of the present invention. The mechanical properties in Example 2 of the present invention are also slightly lower than those in Example 1 of the present invention.

[0033] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A process for forming Mg-9.2Gd-3.2Y-2Zn-0.4Zr alloy by using hammering-assisted cold metal transfer additive manufacturing technology, characterized in that, The process includes the following steps: Step 1, substrate preheating (1) Place the cast aluminum adjustable heating plate on the workbench and place the additive manufacturing substrate above the cast aluminum adjustable heating plate; (2) Connect the temperature control device to the cast aluminum adjustable heating plate and contact the temperature probe with the upper surface of the substrate; (3) Set the substrate preheating temperature; (4) When the temperature probe shows that the temperature reaches a certain temperature, use a wire brush to remove the oxide layer in the welding path area; (5) When the temperature probe shows that the temperature reaches the set temperature, use a fastening structure to fix the substrate and the heating plate together on the workbench, and finally turn off the cast aluminum adjustable heating plate; Step 2, arc additive manufacturing (1) Use modeling software to establish a three-dimensional model, slice the model and plan the path, and set the welding speed and interlayer cooling time; (2) Use the process parameter package suitable for magnesium alloy and correct the current, voltage and wire feeding speed during the welding process; (3) Install the Mg-9.2Gd-3.2Y-2Zn-0.4Zr wt% alloy wire with a diameter of 1.2 mm into the wire feeding device; (4) Use argon as the shielding gas and set the gas feeding speed; (5) After each layer of additive manufacturing is completed, return the welding torch to the initial position to avoid collision with the hammer head; Step 3, hammer the weld bead (1) Set the hammering speed, piston stroke, and rivet size; (2) Hammer immediately after one layer of additive manufacturing is completed and complete the hammering within the interlayer cooling time; (3) After hammering, use a wire brush to clean the oxide and residue on the surface of the weld bead; (4) After forming, cool to room temperature in an air environment.

2. The process for forming Mg-9.2Gd-3.2Y-2Zn-0.4Zr alloy by using the hammering-assisted cold metal transfer additive manufacturing technology according to claim 1, characterized in that, In Step 1, the set substrate preheating temperature is 260°C - 350°C.

3. The process for forming Mg-9.2Gd-3.2Y-2Zn-0.4Zr alloy by using the hammering-assisted cold metal transfer additive manufacturing technology according to claim 1, characterized in that, In Step 1, when the temperature probe shows that the temperature reaches a certain temperature, it is 10 - 20°C lower than the set substrate preheating temperature.

4. The process for forming Mg-9.2Gd-3.2Y-2Zn-0.4Zr alloy by using hammering-assisted cold metal transfer additive manufacturing technology according to claim 1, characterized in that, In Step 2, the welding speed is 10 - 20 mm / s, and the interlayer cooling time is 100 - 150 s.

5. The process for forming Mg-9.2Gd-3.2Y-2Zn-0.4Zr alloy by using hammering-assisted cold metal transfer additive manufacturing technology according to claim 1, characterized in that, In Step 2, the current is 93 - 160 A, and the voltage is 11.7 - 13 V.

6. The process for forming Mg-9.2Gd-3.2Y-2Zn-0.4Zr alloy by using the hammering-assisted cold metal transfer additive manufacturing technology according to claim 1, characterized in that, In Step 2, the wire feeding speed is 10 - 14 m / min.

7. The process for forming the Mg-9.2Gd-3.2Y-2Zn-0.4Zr alloy by using the hammering-assisted cold metal transfer additive manufacturing technology according to claim 1, characterized in that, In Step 2, the gas feeding speed is 15 - 35 L / min.

8. The process for forming Mg-9.2Gd-3.2Y-2Zn-0.4Zr alloy by using hammering-assisted cold metal transfer additive manufacturing technology according to claim 1, characterized in that, In Step 3, the hammering speed is 1740 bpm.

9. The process for forming Mg-9.2Gd-3.2Y-2Zn-0.4Zr alloy by using hammering-assisted cold metal transfer additive manufacturing technology according to claim 1, characterized in that, In Step 3, the piston stroke is 77.8 mm.

10. The process for forming Mg-9.2Gd-3.2Y-2Zn-0.4Zr alloy by using the hammering-assisted cold metal transfer additive manufacturing technology according to claim 1, characterized in that, In Step 3, the rivet size is 4.8 mm.

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