A deformation reversible stress and magnetic field bidirectional excitation 4D printing method

Abstract

The present invention relates to a 4D printing method with reversible deformation and bidirectional excitation of stress and magnetic field, belonging to the field of additive manufacturing technology. Based on magnetostrictive materials, firstly, the controllable preset of the internal stress distribution of the sample in different spatial positions is realized by programming process parameters, and then the printed sample is subjected to heat treatment stress release and magnetic field treatment in turn to realize controllable bidirectional excitation deformation, and the sample is changed to the initial form after magnetic field excitation by controlling the internal stress in advance, and finally the reversible switching between the two forms is realized by whether the magnetic field is applied or not, so as to obtain a magnetostrictive 4D printed part with reversible deformation. The present invention realizes 4D printing of magnetostrictive materials by bidirectional excitation of stress and magnetic field, and the part form can be reversibly switched by magnetic field, which can be used to improve the applicability and flexibility of magnetostrictive molded parts, amplify the magnetostrictive effect, and expand the driving mode of 4D printing, so as to improve its variability and application value.

Description

Technical Field

[0001] The present invention belongs to the technical field of additive manufacturing, and in particular relates to a 4D printing method with reversible deformation and bidirectional excitation of stress and magnetic field. Background Art

[0002] Selective laser melting (SLM) 3D printing technology is a rapid prototyping technology that uses a controlled laser to accurately melt the selected powder area according to the geometric information in the part slice CAD, and then add powder layers and repeat this process until the part is manufactured. This technology has the advantages of high dimensional accuracy and smooth surface. It can directly produce nickel-titanium parts with complex structures such as pore structures and internal pipe networks, and can process personalized small-volume complex parts. It is widely used in aerospace, robotics, automation technology and other fields.

[0003] Magnetostrictive materials refer to materials whose length changes under the action of a magnetic field, which can be displaced and do work, or can be repeatedly stretched and shortened under the action of an alternating magnetic field, thereby generating vibrations or sound waves, and realizing the conversion of electromagnetic energy into mechanical energy or sound energy, and vice versa, mechanical energy can also be converted into electromagnetic energy. It is an important functional material for energy and information conversion, and has broad application prospects in high-tech fields such as underwater acoustic transducer technology, electroacoustic transducer technology, ocean exploration and development technology, micro-displacement drive, vibration reduction and vibration prevention, noise reduction and noise prevention system, intelligent wings, robots, automation technology, fuel injection technology, valves, pumps, and wave production. Current magnetostrictive parts are usually manufactured by traditional thermomechanical methods (such as rolling, forging, extrusion, etc.). Due to the disordered phase change inside the material, cracking during plastic deformation is promoted, which will reduce the magnetostrictive performance of the material, making it difficult to achieve the ideal magnetostrictive effect, resulting in poor applicability and flexibility of the parts produced, easy to break, simple structure, poor processing performance, poor performance, etc., making traditional mechanical processing difficult and not easy to process into complex structural parts.

[0004] 4D printing technology is an emerging manufacturing technology based on 3D printing technology and smart materials. It is a targeted evolution of 3D printed structures in terms of shape, properties and functions. It can achieve self-assembly, multifunctionality and self-repair of materials. It is a material preparation technology with predictable functions. 4D printing technology can achieve changes in specific properties of materials, so that they can meet application needs in various fields, including medical, aerospace, robotics and other fields. Today, 4D printing technology usually uses smart materials for additive manufacturing and externally stimulates the printed structure (heat, light, electricity, magnetism, water, etc.) to change its shape, performance and function. However, since the current 4D printing research is still in the phenomenon demonstration stage, the design theory and method system of its smart components is not perfect, and the design of materials, structures and functions is still in the exploratory stage. This makes the deformation, changeability and function of its smart components simple in form and the driving method is single, which limits the promotion and application of 4D printed samples in the actual engineering field.

[0005] Existing magnetostrictive materials have problems such as unsatisfactory magnetostrictive properties, poor flexibility and applicability, and are not easy to be processed using traditional mechanical processing methods; and 4D printing has the problem of simple deformation, change of properties and function, and a single driving method, making it difficult to promote and apply in the actual engineering field. Summary of the invention

[0006] The present invention provides a 4D printing method with stress and magnetic field bidirectional excitation and reversible deformation, so as to solve the problems of poor applicability and flexibility of existing magnetostrictive parts, unsatisfactory magnetostrictive effect, and difficulty in processing by traditional mechanical processing. The selective laser melting technology is adopted to combine the preset stress, heat treatment process and magnetic field to realize the 4D printing of magnetostrictive materials, and the driving mode of 4D printing can be expanded, thereby improving the variability and application value of 4D printing.

[0007] The technical solution adopted by the present invention comprises the following steps:

[0008] Step 1, selecting magnetostrictive alloy powder as the printing raw material, and using the selective laser melting (SLM) 3D printing method;

[0009] Step 2: Use 3D modeling software to complete the macro and micro structure modeling of the molded parts according to stress requirements;

[0010] Step 3: Input the 3D model file of the part into the selective laser melting 3D printing manufacturing system in STL format;

[0011] Step 4, start the selective laser melting 3D printing manufacturing system, program the changes of printing process parameters in the system in an orderly manner, realize the controllable preset of internal stress of different spatial positions of the sample, and provide a basis for the subsequent bidirectional excitation of stress and magnetic field. The changes of the designed printing process parameters are controlled within a certain range: laser power is controlled at 50-450W, scanning speed is controlled at 200-1600mm / s, scanning spacing is controlled at 0.3-0.7μm, printing layer thickness is controlled at 20-40μm, molding substrate temperature is controlled at 40-60℃, molding chamber temperature is controlled at 70-80℃, and printing angle is controlled at 0-90°;

[0012] Step 5. Use the selective laser melting 3D printing manufacturing system to form the magnetostrictive material parts. According to the layer profile information of the slicing process of the 3D model, the forming cylinder moves in the Z direction, the laser moves in the XY direction, and the powder scraper moves back and forth. After one layer of powder is formed, the forming cylinder drops a layer thickness and then forms the next layer of powder. The forming is superimposed in this way until the 3D model of the part is finally formed. During the printing process, the sample will be affected by different parameters and different preset stresses will be generated in various parts of it.

[0013] Step 6: After the sample is printed, it is placed in a tube furnace for annealing treatment. The atmosphere in the furnace is Ar-4% H2, the working pressure is 0.4Pa, and it is heated from room temperature to 820°C at a rate of 200°C / h. When cooling, it uses a cooling rate of 100°C / h until it reaches 500°C. Then the sample is allowed to cool to room temperature in the furnace. After the heat treatment, the preset stress generated by the different distribution of printing parameters will be released, so that the printed sample will undergo a controllable deformation;

[0014] Step 7: Place the heat-treated sample into a pre-set magnetic field for treatment to magnetize the material. Due to the magnetostrictive properties of the sample material, it will produce lateral and longitudinal deformation effects after being affected by the magnetic field, causing the sample to undergo a secondary deformation after the primary deformation and return to its original form by controlling the internal stress distribution in advance. Finally, the reversible switching between the two forms can be achieved by whether the magnetic field is applied or not. The deformation of the sample in the magnetic field can be expressed as:

[0015]

[0016] In the formula, is the deformation caused by magnetostriction, e is the deformation at magnetization saturation, is the angle between the observation direction or test direction and the direction of magnetization intensity;

[0017] Where e can be expressed as the magnetostriction coefficient λ of the available material:

[0018]

[0019] Step 8. By combining the primary deformation stimulated by stress release and the secondary deformation stimulated by magnetic field, a 4D printed part of a magnetostrictive material with a reversible switching shape can be obtained, thereby realizing 4D printing of magnetostrictive materials with reversible deformation and bidirectional excitation of stress and magnetic field.

[0020] Furthermore, the 3D printing method used in step 1 is one of powder bonding printing in selective laser melting printing, selective laser sintering printing, fused deposition printing, and electron beam melting printing.

[0021] Furthermore, the magnetostrictive alloy powder used in step 1 is one of the magnetostrictive materials selected from TbFe2, SmFe2, Tb(CoFe)2, TbFe3, and DyFe2.

[0022] Furthermore, the macro-microstructure modeling in step 2 is modeled using CATIA, SolidWorks, Pro / E or UG three-dimensional modeling software.

[0023] Furthermore, the inert gas filled in the tube furnace in step 6 is xenon, nitrogen or argon.

[0024] Furthermore, the magnetic field in step 7 is one of the magnetic fields generated by bar magnets and horseshoe magnets, the magnetic fields generated by straight currents, the magnetic fields generated by energized solenoids, and the magnetic fields generated by circular currents.

[0025] The present invention is based on magnetostrictive materials and adopts a bidirectional excitation method of heat treatment stress release and magnetic field treatment to deform the printed sample, wherein the deformation is controllable through precise control of the internal stress of the sample, so that the sample can be restored to its original shape after magnetic field excitation, and finally reversible switching between the two shapes can be achieved by whether the magnetic field is applied or not, thereby obtaining a magnetostrictive 4D printed part with reversible deformation.

[0026] The beneficial effects of the present invention are as follows: by adopting the selective laser melting 3D printing method, parts can be directly formed in a net shape, so as to solve the problem that the existing magnetostrictive alloy materials are difficult to process by traditional processing methods; by orderly programming the printing process parameters, the internal stress distribution of the sample at different spatial positions can be preset, so as to realize the programming control of the orderly change of the internal stress of the sample during the printing process, and achieve the effect of shape control and property control; by adopting the bidirectional excitation method of stress and magnetic field, the reversible switching of the two forms of the sample can be realized by adding or not adding the magnetic field, so as to obtain a magnetostrictive 4D printed molded part with a reversible switching form. This can improve the applicability and flexibility of magnetostrictive molded parts, amplify the magnetostrictive effect of the material, realize the reversible form switching of magnetostrictive 3D printed molded parts, and expand the driving method of 4D printing, so as to improve its variability and application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a flow chart of the present invention;

[0028] Figure 2 It is a schematic diagram of the present invention;

[0029] Figure 3 It is the selective laser melting device and principle diagram of the present invention;

[0030] Figure 4 It is a schematic diagram of the superposition of the selective laser melting device of the present invention;

[0031] Figure 5 It is a schematic diagram of the present invention placing a sample into a pre-set linear current magnetic field for processing;

[0032] Figure 6 It is a schematic diagram of the magnetostrictive characteristic principle of the present invention. DETAILED DESCRIPTION

[0033] The ideal magnetostrictive material should have significant magnetostrictive properties, and its molded parts should have high applicability and flexibility; at the same time, 4D printing should have a wide range of driving modes and complex variable capabilities. In view of the above points, the present invention adopts selective laser melting technology to combine preset stress, process and magnetic field to realize 4D printing of magnetostrictive materials. Through the orderly programming of printing process parameters, the controllable preset of the internal stress distribution of the sample at different spatial positions can be realized during the printing process, achieving the effect of controlling the shape and property. The printed magnetostrictive sample is 4D printed by bidirectional excitation of stress and magnetic field, and the part shape can be reversibly switched by magnetic field, which can be used to improve the applicability and flexibility of magnetostrictive molded parts, amplify the magnetostrictive effect, and expand the driving mode of 4D printing, and improve its variability and application value. A magnetostrictive 4D printed molded part with reversible deformation is obtained.

[0034] The present invention is based on magnetostrictive materials and adopts a bidirectional excitation method of heat treatment stress release and magnetic field treatment to make the printed sample deform. The deformation is controllable through precise control of the stress inside the sample, so that the sample can return to its original shape after magnetic field excitation. Finally, reversible switching between the two forms can be achieved by whether the magnetic field is applied or not.

[0035] like Figure 1 , 2 As shown, the following steps are included:

[0036] Step 1: Select TbFe2 magnetostrictive alloy powder as the printing raw material. The magnetostriction value of the material is 2000ppm, and the selected laser melting (SLM) 3D printing method is used for molding. The principle of this method is as follows: Figure 3As shown: the powder spreading device first pushes the metal powder flat onto the substrate of the forming cylinder, and the laser beam then follows the filling scan line of the current layer to selectively melt the powder on the substrate to process the current layer, then the forming cylinder descends a layer thickness, and the powder cylinder rises a certain thickness, and the powder spreading device spreads the metal powder on the processed current layer, and the equipment calls in the data of the next layer contour for processing, and the processing is repeated layer by layer until the entire part is processed; the magnetostrictive alloy powder used here can also be one of other magnetostrictive materials such as SmFe2, Tb(CoFe)2, TbFe3, DyFe2, etc.; in addition, the 3D printing method used here can also be one of other powder bonding printing such as selective laser sintering printing, fused deposition printing, electron beam melting printing, etc.;

[0037] Step 2: Use CATIA software to establish the molded part structure, and complete the macro-microstructure modeling of the molded part according to the stress requirements. Here, the macro-microstructure modeling can also be done with other 3D modeling software such as Solidworks, Pro / E and UG;

[0038] Step 3: Input the 3D model file of the part into the selective laser melting 3D printing manufacturing system in STL format;

[0039] Step 4, start the selective laser melting 3D printing manufacturing system, program the changes of printing process parameters in the system in an orderly manner, realize the controllable preset of internal stress of different spatial positions of the sample, so as to realize the programming control of the time series change of internal stress of the sample during the printing process, achieve the effect of shape control and property control, and provide a basis for the subsequent bidirectional excitation of stress and magnetic field. The changes of the designed printing process parameters are controlled within a certain range: laser power is controlled at 50-450W, scanning speed is controlled at 200-1600mm / s, scanning spacing is controlled at 0.3-0.7μm, printing layer thickness is controlled at 20-40μm, molding substrate temperature is controlled at 40-60℃, molding chamber temperature is controlled at 70-80℃, and printing angle is controlled at 0-90°;

[0040] Step 5: Use the selective laser melting 3D printing manufacturing system to form the TbFe2 magnetostrictive material parts. According to the layer contour information of the slicing process of the 3D model, the forming cylinder moves in the Z direction, the laser moves in the XY direction, and the powder scraper moves back and forth. After one layer of powder is formed, the forming cylinder drops to a layer thickness and then forms the next layer of powder. The forming is superimposed in this way until the 3D model of the part is finally formed. Figure 4 As shown in the figure, during the printing process, the sample is affected by different parameters and different preset stresses are generated in various parts of the sample.

[0041] Step 6. After the sample is printed, it is placed in a tube furnace (Ar-4% H2 atmosphere) for annealing treatment. The working pressure is 0.4Pa. Here, the inert gas filled in the tube furnace can also be other inert gases such as xenon and nitrogen. When heating, the furnace is heated from room temperature to 820℃ at a rate of 200℃ / h. When cooling, a cooling rate of 100℃ / h is used until it reaches 500℃. Then the sample is allowed to cool to room temperature in the furnace. After heat treatment, the preset stress generated by the different distribution of printing parameters will be released, causing a controllable deformation of the printed sample.

[0042] Step 7: Place the heat-treated sample into a pre-set linear current magnetic field for treatment, such as Figure 5 As shown, the material is magnetized, the magnetic field strength is 70000Oe, the temperature is 600K, and the magnetostriction value of the material is 2000ppm. Here, the magnetic field can also be selected from the magnetic field generated by bar magnets and horseshoe magnets, the magnetic field generated by energized solenoids, the magnetic field generated by circular currents, and other magnetic fields. Due to the magnetostrictive properties of the sample material, it will produce lateral and longitudinal deformation effects after being affected by the magnetic field, causing the sample to undergo a secondary deformation after the primary deformation and to return to its original form by controlling the internal stress distribution in advance. Finally, the reversible switching between the two forms can be achieved by whether the magnetic field is applied or not. The principle of the magnetostrictive properties of the material is as follows Figure 6 As shown: Ferromagnetic materials will undergo spontaneous magnetization below the Curie point, forming a large number of magnetic domains; in each magnetic domain, the lattice is deformed, and the direction of its magnetization intensity is the main axis of spontaneous deformation. When there is no external magnetic field, the magnetization direction of the magnetic domain is randomly oriented and does not show macroscopic deformation. Under the action of an external magnetic field, the magnetization direction of a large number of magnetic domains turns to the direction of the external magnetic field, and the deformation of the lattice causes the material to stretch in the direction of the external field (△L). When it is separated from the magnetic field, the magnetic domain will gradually restore its original orientation, restoring the material to its original form. The deformation of the sample in the magnetic field can be expressed as:

[0043]

[0044] In the formula, is the deformation caused by magnetostriction, e is the deformation at magnetization saturation, is the angle between the observation direction (test direction) and the magnetization intensity direction;

[0045] In the demagnetized state, the direction of the magnetization intensity of the magnetic domain is randomly distributed, and its average deformation is:

[0046]

[0047] At saturation:

[0048]

[0049] The saturation magnetostriction is:

[0050]

[0051] The spontaneous strain in the magnetic domain can be expressed by the magnetostriction coefficient λ of the material:

[0052]

[0053] Step 8. By combining the primary deformation stimulated by stress release and the secondary deformation stimulated by magnetic field, a 4D printed part of a magnetostrictive material with a reversible switching shape can be obtained, thereby realizing 4D printing of magnetostrictive materials with reversible deformation and bidirectional excitation of stress and magnetic field.

Claims

1. A deformation reversible stress and magnetic field bidirectional excitation 4D printing method, characterized in that: The following steps are involved: Step 1, selecting magnetostrictive alloy powder as the printing raw material, and using the selective laser melting (SLM) 3D printing method; Step 2: Use 3D modeling software to complete the macro and micro structure modeling of the molded parts according to stress requirements; Step 3: Input the 3D model file of the part into the selective laser melting 3D printing manufacturing system in STL format; Step 4, start the selective laser melting 3D printing manufacturing system, program the changes of printing process parameters in the system in an orderly manner, realize the controllable preset of internal stress of different spatial positions of the sample, and provide a basis for the subsequent bidirectional excitation of stress and magnetic field. The changes of the designed printing process parameters are controlled within a certain range: laser power is controlled at 50-450W, scanning speed is controlled at 200-1600mm / s, scanning spacing is controlled at 0.3-0.7μm, printing layer thickness is controlled at 20-40μm, molding substrate temperature is controlled at 40-60℃, molding chamber temperature is controlled at 70-80℃, and printing angle is controlled at 0-90°; Step 5. Use the selective laser melting 3D printing manufacturing system to form the magnetostrictive material parts. According to the layer profile information of the slicing process of the 3D model, the forming cylinder moves in the Z direction, the laser moves in the XY direction, and the powder scraper moves back and forth. After one layer of powder is formed, the forming cylinder drops a layer thickness and then forms the next layer of powder. The forming is superimposed in this way until the 3D model of the part is finally formed. During the printing process, the sample will be affected by different parameters and different preset stresses will be generated in various parts of it. Step 6: After the sample is printed, it is placed in a tube furnace for annealing treatment. The atmosphere in the furnace is Ar-4% H2, the working pressure is 0.4Pa, and it is heated from room temperature to 820°C at a rate of 200°C / h. When cooling, it uses a cooling rate of 100°C / h until it reaches 500°C. Then the sample is allowed to cool to room temperature in the furnace. After the heat treatment, the preset stress generated by the different distribution of printing parameters will be released, so that the printed sample will undergo a controllable deformation; Step 7: Place the heat-treated sample into a pre-set magnetic field for treatment to magnetize the material. Due to the magnetostrictive properties of the sample material, it will produce lateral and longitudinal deformation effects after being affected by the magnetic field, causing the sample to undergo a secondary deformation after the primary deformation and return to its original form by controlling the internal stress distribution in advance. Finally, the reversible switching between the two forms can be achieved by whether the magnetic field is applied or not. The deformation of the sample in the magnetic field can be expressed as: In the formula, is the deformation caused by magnetostriction, e is the deformation at magnetization saturation, is the angle between the observation direction or test direction and the magnetization intensity direction; Where e can be expressed as the magnetostriction coefficient λ of the available material: Step 8. By combining the primary deformation stimulated by stress release and the secondary deformation stimulated by magnetic field, a 4D printed part of a magnetostrictive material with a reversible switching shape can be obtained, thereby realizing 4D printing of magnetostrictive materials with reversible deformation and bidirectional excitation of stress and magnetic field.

2. The method of 4D printing with stress and magnetic field bidirectional excitation and reversible deformation according to claim 1, characterized in that: The 3D printing method used in step 1 is one of the powder bonding printing in selective laser melting printing, selective laser sintering printing, fused deposition printing, and electron beam melting printing.

3. The method of 4D printing with stress and magnetic field bidirectional excitation and reversible deformation according to claim 1, characterized in that: The magnetostrictive alloy powder used in step 1 is one of TbFe2, SmFe2, Tb(CoFe)2, TbFe3, and DyFe2 magnetostrictive materials.

4. The method of 4D printing with stress and magnetic field bidirectional excitation and reversible deformation according to claim 1, characterized in that: The macro-microstructure modeling in step 2 is modeled using CATIA, SolidWorks, Pro / E or UG three-dimensional modeling software.

5. The method of 4D printing with stress and magnetic field bidirectional excitation and reversible deformation according to claim 1, characterized in that: The inert gas filled in the tube furnace in step 6 is xenon, nitrogen or argon.

6. The deformation reversible stress and magnetic field bidirectional excitation 4D printing method according to claim 1, characterized in that: The magnetic field in step 7 is one of the magnetic fields generated by bar magnets and horseshoe magnets, the magnetic fields generated by straight currents, the magnetic fields generated by energized solenoids, and the magnetic fields generated by circular currents.

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