CN113500205B - 3D printing method of bimetallic material - Google Patents
3D printing method of bimetallic material Download PDFInfo
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- CN113500205B CN113500205B CN202110782257.7A CN202110782257A CN113500205B CN 113500205 B CN113500205 B CN 113500205B CN 202110782257 A CN202110782257 A CN 202110782257A CN 113500205 B CN113500205 B CN 113500205B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F10/00—Additive manufacturing of workpieces or articles from metallic powder
- B22F10/10—Formation of a green body
- B22F10/16—Formation of a green body by embedding the binder within the powder bed
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F10/00—Additive manufacturing of workpieces or articles from metallic powder
- B22F10/30—Process control
- B22F10/38—Process control to achieve specific product aspects, e.g. surface smoothness, density, porosity or hollow structures
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F10/00—Additive manufacturing of workpieces or articles from metallic powder
- B22F10/60—Treatment of workpieces or articles after build-up
- B22F10/64—Treatment of workpieces or articles after build-up by thermal means
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B33—ADDITIVE MANUFACTURING TECHNOLOGY
- B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
- B33Y10/00—Processes of additive manufacturing
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B33—ADDITIVE MANUFACTURING TECHNOLOGY
- B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
- B33Y40/00—Auxiliary operations or equipment, e.g. for material handling
- B33Y40/20—Post-treatment, e.g. curing, coating or polishing
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B33—ADDITIVE MANUFACTURING TECHNOLOGY
- B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
- B33Y70/00—Materials specially adapted for additive manufacturing
- B33Y70/10—Composites of different types of material, e.g. mixtures of ceramics and polymers or mixtures of metals and biomaterials
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B33—ADDITIVE MANUFACTURING TECHNOLOGY
- B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
- B33Y80/00—Products made by additive manufacturing
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/25—Process efficiency
Abstract
The invention relates to a 3D printing method of a bimetallic material, and belongs to the field of additive manufacturing. Including copper thick liquids and iron thick liquids preparation, give copper thick liquids, iron thick liquids syringe pressure during printing, reciprocating motion successive layer shaping, final shaping bimetallic material three-dimensional part carries out vacuum high temperature thermal treatment and includes: vacuumizing, pyrolyzing the binder, sintering the metal particles and cooling. The advantages are that: the binder proportion of the iron and copper metal slurry is adjusted, so that the iron and copper metal slurry can be smoothly extruded and molded, and the iron and copper metal slurry can keep consistent shrinkage in sintering. In the heat treatment forming process, factors such as sintering temperature, vacuum degree, sintering duration and the like are comprehensively adjusted according to the properties of iron and copper metal materials, so that the iron and copper metal materials can be sintered and formed at high temperature under the same sintering parameters, and have the same shrinkage rate, and the problems of no oxidation, deformation, cracks, low strength and the like, thereby having excellent performance and being applied to practical production and application.
Description
Technical Field
The invention belongs to the field of additive manufacturing, and particularly relates to a 3D printing method for a bimetallic material, which can be used for processing a three-dimensional structure of the bimetallic material, which is customized, small in batch, difficult to realize by a traditional manufacturing process, complex in geometric shape and excellent in performance.
Background
The bimetal material part has important application in the fields of aerospace, batteries, automobiles and the like. For example, in the field of aerospace, a copper valve on an aircraft engine needs to be made of a high-temperature-resistant copper material inside, and needs to be made of a high-strength stainless steel material outside; in the field of batteries, electrodes and solid electrolytes need to be integrated from two different metal materials; in the automotive field, the car body is often formed by integrating a titanium alloy material with reduced density and other metal materials, so that the performance of the car body is met, the quality of the car body is reduced, and the energy consumption is reduced. In order to realize application value, the bimetallic material part needs to meet the following characteristics: (1) The precise manufacturing of different materials in the design area has no element pollution. (2) High shape accuracy (3) and high bonding strength between different materials. And (4) complex geometric shapes.
The traditional manufacturing technology such as cold pressing, casting, welding and the like is difficult to manufacture the bimetal part with excellent performance. The 3D printing technology has the advantages of customizing complex geometric shapes, wide materials, short design period, high product quality and the like, and particularly can customize the bimetal part with excellent performance.
However, the conventional metal additive manufacturing techniques such as Electrochemical additive manufacturing (ECAM), powder Bed Fusion (PBF), and Direct Energy Deposition (DED) cannot manufacture a bi-material component having the above characteristics. Electrochemical additive manufacturing (ECAM) is a relatively new form of metallic AM that uses localized electrochemical deposition of metal ions in an electrolyte to create metallic structures. The technique has the advantage of strong bonding force between metal materials. However, since the deposition rate of metal ions is very slow and the deposition interval cannot be controlled, the technique has the following disadvantages: the additive manufacturing of parts with complex geometric shapes cannot be realized; additive manufacturing of large-size parts cannot be realized; due to factors such as electric field diffusion and the like, a metal ion deposition area is not fixed, accurate deposition of different materials in a set area cannot be realized, the manufacturing precision is low, the surface of a part is rough, and the number of defects is large.
Powder Bed Fusion (PBF) and Direct Energy Deposition (DED). The Powder Bed Fusion (PBF) technique first requires spreading metal powder on a processing table, then scanning the powder with a high-energy laser beam to melt the powder and solidify it, and this process is repeated layer by layer until the target part is processed. The Direct Energy Deposition (DED) technology is characterized in that metal powder and protective gas are conveyed to the position right below a laser through a powder feeding device, the laser emits high-energy laser beams to heat and melt the metal powder, and the laser beams and the powder synchronously run until parts are machined. Both the two methods have the advantages of being capable of processing parts with high density, forming in one step and the like. However, since both of these techniques require a powder spreading system to spread powder and then melt and mold the metal material by laser, they have the following disadvantages:
1) The laser processing system has high manufacturing cost, high cost and potential safety hazard, and the processed active metal is easy to explode;
2) The rapid temperature rise and fall of the processed area can increase the heat effect of metal, thereby reducing the mechanical property of a workpiece, and enabling dissimilar metal materials to be incapable of being combined.
3) The powder material cannot be replaced in the printing process or a plurality of kinds of powder exist after the replacement, so that the precise deposition of the specific material in the set area cannot be realized.
4) Low printing precision, large part size, rough surface, easy warping and deformation, and the like.
In addition, the metal paste direct writing technology prepares metal paste by mixing metal powder with a binder (polymer), then loads the metal paste into an injector, extrudes filaments under pressure to form a complex three-dimensional structure, then carries out vacuum high-temperature heat treatment on the complex three-dimensional structure, removes the binder (polymer), and melts, solidifies and forms the metal powder, thereby obtaining a high-performance processed part. The technology has the advantages of low processing cost, high processing precision, capability of realizing accurate deposition in a design area, low metal heat effect during vacuum high-temperature heat treatment, good mechanical property and the like. However, the technology for preparing the bimetallic material part is not realized at present, and one main difficulty is that: because the physical properties of different metal materials, such as melting point, vapor pressure, thermal expansion coefficient, activity and the like, are too different, the sintering degree and the oxidation degree of different metal materials are different in the vacuum high-temperature heat treatment process under the same heat treatment condition, so that the shrinkage rates of different metal materials are different, and finally, the shrinkage rates of different metal materials in finished parts are different, so that the defects of deformation, cracks and the like are caused. The specific influencing factors and processes are as follows:
(1) The metal slurry formula comprises: the metal slurry is formed by mixing metal powder and a binder according to a certain proportion, if the binder proportion is too large, the slurry is thin and cannot be formed, and if the binder proportion is too small, the slurry blocks a spray head; therefore, it is necessary to develop a proper metal paste formulation to ensure smooth printing, however, since different metal materials have different flowability, the ratio of the binder to the metal powder in the proper paste formulation is different corresponding to the different metal materials. In addition, the thickness of the extruded lines of the metal pastes under different binder proportions is different, so that the suitable printing parameters are different, however, in the printing process of the bimetallic material, the printing parameters are unique, so that the thickness of the extruded lines of the two metal pastes is different, and the bimetallic sample piece is defective in the printing process, so that the properties of the two metals need to be comprehensively considered, and the lines can be smoothly extruded and have consistent thickness when the suitable binder proportions are developed. More importantly, in the subsequent vacuum high-temperature heat treatment process, the binder can be thermally decomposed, only metal powder is left, so that the volume of the part can be reduced according to the volume of the removed binder, and different shrinkage rates of the formed metal are directly caused by different binder proportions. Therefore, developing a metal paste with a proper binder ratio corresponding to different metal material combinations is an important difficulty of the direct writing technology of the bimetallic material paste.
(2) Sintering conditions are as follows: the part molding is mainly based on mutual fusion between metal powders during the printing process and the vacuum high-temperature heat treatment process, and the higher the fusion degree is, the larger the volume shrinkage of the part is. The powder fusion degree of the metal powder in the heat treatment process is determined by sintering temperature, vacuum degree and sintering time, the higher the sintering temperature is, the higher the vacuum degree is, the longer the sintering time is, the higher the fusion degree of the metal powder is, and the larger the metal volume shrinkage is. Under the same heat treatment condition, the lower the melting point of the metal, the greater the powder fusion degree and the greater the metal volume shrinkage; the lower the activity type of the metal, the greater the fusion degree, and the greater the metal volume shrinkage, because the surface of the metal powder with high activity can generate an oxide film to prevent the metal powder from fusing; the higher the saturated vapor pressure of the metal, the more the amount of volatilization and the larger the metal volume shrinkage. The bimetallic parts can only be sintered together, so the sintering conditions are the same, however, due to different properties of the metal materials, the volume shrinkage of different metal material parts is inconsistent, and finally the bimetallic parts have the defects of deformation, cracks and the like. Therefore, the formulation of the metal paste and the vacuum high temperature heat treatment conditions need to be studied.
Therefore, no report of relevant research is seen at present, so that the technology for preparing the bimetallic material part is not realized at present.
Disclosure of Invention
The invention provides a 3D printing method of a bimetallic material, which aims to solve the problems of deformation and cracks caused by different shrinkage rates in the conventional bimetallic material printing process.
The technical scheme adopted by the invention is that the method comprises the following steps:
preparing slurry:
(1) Mixing copper metal particles with the diameter of 0.1-200 microns and a binder in a ball mill for 15-60 minutes, wherein the volume ratio of the copper metal particles to the binder is (4-7): 1, thus obtaining uniformly mixed copper slurry;
(2) Mixing iron metal particles with the diameter of 0.1-200 microns and a binder in a ball mill for 15-60 minutes, wherein the volume ratio of the metal particles to the binder is (1-3): 1, obtaining uniformly mixed iron slurry;
(II) printing process:
(1) Importing a pre-designed model with STL format, wherein the model consists of two parts, each part corresponds to a metal material, and a printing track is automatically produced by software;
(2) When 3D printing starts, the air pump continuously applies pressure to the copper paste injector according to a set program to enable copper paste to be extruded into filaments from the conical nozzle under stable pressure, the copper paste injector moves according to a preset program to enable extruded copper filaments to be formed on the substrate, and after the first layer of program is finished, the copper paste injector is withdrawn;
(3) The air pump continuously applies pressure to the iron slurry injector according to a set program to enable the iron slurry to be extruded into filaments from the conical nozzle under stable pressure, the iron slurry injector moves according to a preset program to enable the extruded filaments to be molded on the substrate, and after the program is finished, the iron slurry injector is withdrawn;
(4) And after the copper slurry injector and the iron slurry injector are alternately moved once, the first layer is formed. Repeating the steps (1) and (2) under the control of a program, and forming layer by layer through reciprocating motion to finally form the bimetallic material three-dimensional part;
(III) carrying out vacuum high-temperature heat treatment on the bimetallic material three-dimensional part, comprising the following steps:
(1) Vacuumizing: putting a bimetal part to be sintered into a sintering furnace, and vacuumizing by using a mechanical pump, wherein the vacuum degree is matched with the properties of two metal slurries, and the vacuum degree is adjusted to 1-100 Pa, so that an oxide film is generated on part of copper metal powder, the fusion degree of copper particles is reduced, and the shrinkage rate of copper is reduced;
(2) Pyrolysis of the binder: heating the vacuum furnace to 300-400 ℃ at the speed of 600 ℃/h, keeping the temperature for 1-2 h, waiting for complete pyrolysis of the binder, wherein the volume of the iron metal part is smaller than that of the copper metal part when the bimetallic material three-dimensional part shrinks for the first time, and the reason is that the shrinkage rate is large because the proportion of the iron metal slurry binder is large;
(3) Sintering of metal particles: after the binder is pyrolyzed, heating the vacuum furnace to 900-1050 ℃ at the speed of 600 ℃/h, closing the mechanical pump, stopping vacuumizing, preventing a large amount of copper powder from volatilizing, keeping the temperature for 3-12 h, sintering metal particles, wherein the bimetallic material three-dimensional part shrinks for the second time, the metal particles start to melt, the melting degree of iron particles is low, the melting degree of copper particles is high, and finally the metal volumes of the two parts tend to be consistent;
(4) And (3) cooling: and after the bimetal part is fully sintered, automatically cooling the sintering furnace, and taking out the sample after introducing inert gas into the sintering furnace to prevent the sample from being oxidized in the air.
The preparation method of the adhesive comprises the following steps: the mass ratio of the polymer to the solvent is 1:3 to 5.
The polymer comprises polylactic acid (PLA), polyvinyl alcohol (PVA) or chitosan.
The solvent of the invention comprises dichloromethane DCM, water or absolute ethyl alcohol solution.
When the copper slurry is prepared in the step (I), the rotating speed of the ball mill is 300-800 r/min.
When the iron slurry is prepared in the step (I), the rotating speed of the ball mill is 300-800 r/min.
In the step (II), the pressure of the copper slurry injector is 0.1-5Mpa.
In the step (II), the pressure of the iron slurry injector is 0.1-5Mpa.
The invention has the advantages that:
the invention prepares the metal slurry by mixing the metal powder and the binder, so the material utilization rate is high, no loss is caused, and expensive equipment such as laser is not needed, so the cost is low and the operation is safe. The whole of the processed part is sintered and molded, and the temperature rise and the temperature decrease are carried out slowly, so the heat effect is low and the mechanical property is good. According to the invention, the metal slurry in the injector is extruded into the filament from the conical nozzle by adopting pneumatic pressure, and the filament is laminated and formed on the upper layer of the substrate. On the other hand, the invention adjusts the binder proportion of the iron and the copper metal slurry, so that the iron and the copper metal slurry can be smoothly extruded and molded without defects, and the iron and the copper metal slurry can keep consistent shrinkage in sintering. Finally, in the heat treatment forming process, factors such as sintering temperature, vacuum degree, sintering time and the like are comprehensively adjusted according to the properties of iron and copper metal materials. The iron and copper metal materials can be sintered and molded at high temperature under the same sintering parameters, and have the same shrinkage rate, so that the molded parts have no problems of oxidation, deformation, cracks, low strength and the like, thereby having excellent performance and being applied to practical production and application. In addition, the iron-copper dual-material combination aimed by the invention has a difference of up to 500 degrees in melting points of the materials, and the difference of the melting points is an important factor influencing the sintering result, which means that the metal combinations with the difference of the melting points less than 500 degrees can be manufactured by the technology of the invention, therefore, the technology is hopeful to be popularized to most metal combinations, including iron and titanium, iron and nickel or nickel and copper, and the like.
Drawings
FIG. 1 is a diagram of an iron-copper bimetallic part object obtained by the printing method of the invention;
FIG. 2 is a pictorial view of an iron-copper bimetallic part with inappropriate binder ratio and sintering parameters;
FIG. 3 is a diagram of an iron-copper bimetallic part with a properly optimized binder ratio and sintering parameters;
FIG. 4 is an SEM image of the surface of the iron-copper bimetal part obtained by the printing method of the invention;
FIG. 5 is an analysis diagram of the internal morphology and the elements of the iron-copper bimetal part obtained by the printing method;
fig. 6 is a diagram of a complex structure of bimetal iron and copper manufactured under the optimal binder ratio and sintering parameters of the invention.
Detailed Description
Example 1
Comprises the following steps:
preparing slurry:
(1) Mixing copper metal particles with the diameter of 0.1 micron and a binder in a ball mill for 15 minutes, wherein the rotating speed of the ball mill is 300r/min, and the volume ratio of the copper metal particles to the binder is 4:1, thus obtaining uniformly mixed copper slurry;
(2) Mixing iron metal particles with the diameter of 0.1 micron and a binder in a ball mill for 15 minutes, wherein the rotating speed of the ball mill is 300r/min, and the volume ratio of the metal particles to the binder is 1:1, obtaining uniformly mixed iron slurry;
the preparation method of the adhesive comprises the following steps: the mass ratio of the polymer to the solvent is 1:3;
the polymer adopts polylactic acid (PLA), and the solvent adopts water;
(II) printing process:
(1) Importing a pre-designed model with STL format, wherein the model consists of two parts, each part corresponds to a metal material, and a printing track is automatically produced by software;
(2) When 3D printing starts, the air pump continuously applies pressure to the copper paste injector according to a set program, the pressure is 0.1Mpa, so that copper paste is extruded into a filament from the conical nozzle under stable pressure, the copper paste injector moves according to a preset program, so that the extruded copper filament is formed on the substrate, and after the first layer program is finished, the copper paste injector is withdrawn;
(3) The air pump continuously applies pressure to the iron slurry injector according to a set program, the pressure is 0.1Mpa, so that the iron slurry is extruded into filaments from the conical nozzle under stable pressure, the iron slurry injector moves according to a preset program, so that the extruded filaments are formed on the substrate, and after the program is finished, the iron slurry injector is withdrawn;
(4) And after the copper slurry injector and the iron slurry injector are alternately moved once, the first layer is formed. Repeating the steps (1) and (2) under the control of a program by using a copper slurry injector and an iron slurry injector, and performing reciprocating motion layer by layer to form the bimetallic material three-dimensional part finally;
(III) carrying out vacuum high-temperature heat treatment on the bimetallic material three-dimensional part, comprising the following steps:
(1) Vacuumizing: placing a bimetal part to be sintered into a sintering furnace, vacuumizing by using a mechanical pump, and adjusting the vacuum degree to be 1Pa so that the copper metal powder partially generates an oxide film, the fusion degree of copper particles is reduced, and the shrinkage rate of copper is reduced, wherein the vacuum degree is matched with the properties of two metal slurries;
(2) Pyrolysis of the binder: heating the vacuum furnace to 300 ℃ at the speed of 600 ℃/h, keeping the temperature for 1h, waiting for the binder to be completely pyrolyzed, and enabling the three-dimensional part of the bimetallic material to shrink for the first time, wherein the volume of the iron metal part is smaller than that of the copper metal part, which is the reason that the shrinkage rate is large because the proportion of the binder of the iron metal slurry is large;
(3) Sintering of metal particles: after the binder is pyrolyzed, heating the vacuum furnace to 900 ℃ at the speed of 600 ℃/h, closing the mechanical pump, stopping vacuumizing, preventing a large amount of copper powder from volatilizing, keeping the temperature for 3h, sintering metal particles, wherein the bimetallic material three-dimensional part shrinks for the second time, the metal particles begin to melt, the melting degree of iron particles is low, the melting degree of copper particles is high, and finally the metal volumes of the two parts tend to be consistent;
(4) And (3) cooling: and after the bimetal part is fully sintered, automatically cooling the sintering furnace, and taking out the sample after introducing inert gas into the sintering furnace to prevent the sample from being oxidized in the air.
Example 2
Comprises the following steps:
preparing slurry:
(1) Mixing copper metal particles with the diameter of 100 microns and a binder in a ball mill for 35 minutes, wherein the rotating speed of the ball mill is 500r/min, and the volume ratio of the copper metal particles to the binder is 6:1, thus obtaining uniformly mixed copper slurry;
(2) Mixing iron metal particles with the diameter of 100 microns and a binder in a ball mill for 35 minutes, wherein the rotating speed of the ball mill is 500r/min, and the volume ratio of the metal particles to the binder is 2:1, obtaining uniformly mixed iron slurry;
the preparation method of the adhesive comprises the following steps: the mass ratio of the polymer to the solvent is 1:4;
the polymer adopts polyvinyl alcohol PVA; the solvent adopts dichloromethane DCM;
(II) printing process:
(1) Importing a pre-designed model with STL format, wherein the model consists of two parts, each part corresponds to a metal material, and a printing track is automatically produced by software;
(2) When 3D printing starts, the air pump continuously applies pressure to the copper paste injector according to a set program, the pressure is 3Mpa, so that copper paste is extruded into filaments from the conical nozzle under stable pressure, the copper paste injector moves according to a preset program, so that the extruded copper filaments are formed on the substrate, and after the first layer of program is finished, the copper paste injector is withdrawn;
(3) The air pump continuously applies pressure to the iron slurry injector according to a set program, the pressure is 3Mpa, so that the iron slurry is extruded into filaments from the conical nozzle under stable pressure, the iron slurry injector moves according to a preset program, so that the extruded filaments are formed on the substrate, and after the program is finished, the iron slurry injector is withdrawn;
(4) And after the copper slurry injector and the iron slurry injector are alternately moved once, the first layer is formed. Repeating the steps (1) and (2) under the control of a program, and forming layer by layer through reciprocating motion to finally form the bimetallic material three-dimensional part;
and (III) carrying out vacuum high-temperature heat treatment on the bimetal three-dimensional part, which comprises the following steps:
(1) Vacuumizing: putting a bimetal part to be sintered into a sintering furnace, and vacuumizing by using a mechanical pump, wherein the vacuum degree is matched with the properties of two metal slurries, and the vacuum degree is adjusted to 50Pa, so that an oxide film is partially generated on copper metal powder, the fusion degree of copper particles is reduced, and the shrinkage rate of copper is reduced;
(2) Pyrolysis of the binder: heating the vacuum furnace to 350 ℃ at the speed of 600 ℃/h, keeping the temperature for 1.5h, waiting for complete pyrolysis of the binder, wherein the volume of the iron metal part is smaller than that of the copper metal part when the bimetallic material three-dimensional part shrinks for the first time, and the reason is that the shrinkage rate is large because the proportion of the binder of the iron metal slurry is large;
(3) Sintering of metal particles: after the binder is pyrolyzed, heating the vacuum furnace to 1000 ℃ at the speed of 600 ℃/h, closing the mechanical pump, stopping vacuumizing, preventing a large amount of copper powder from volatilizing, keeping the temperature for 8h, sintering metal particles, wherein the bimetallic material three-dimensional part shrinks for the second time, the metal particles begin to melt, the melting degree of iron particles is low, the melting degree of copper particles is high, and finally the metal volumes of the two parts tend to be consistent;
(4) And (3) cooling: and after the bimetal part is fully sintered, automatically cooling the sintering furnace, and taking out the sample after introducing inert gas into the sintering furnace to prevent the sample from being oxidized in the air.
Example 3
Comprises the following steps:
preparing slurry:
(1) Mixing copper metal particles with the diameter of 200 microns and a binder in a ball mill for 60 minutes, wherein the rotating speed of the ball mill is 800r/min, and the volume ratio of the copper metal particles to the binder is 7:1, thus obtaining uniformly mixed copper slurry;
(2) Mixing iron metal particles with the diameter of 200 microns and a binder in a ball mill for 60 minutes, wherein the rotating speed of the ball mill is 800r/min, and the volume ratio of the metal particles to the binder is 3:1, obtaining uniformly mixed iron slurry;
the preparation method of the adhesive comprises the following steps: the mass ratio of the polymer to the solvent is 1:5;
the polymer adopts chitosan; the solvent adopts absolute ethyl alcohol solution;
(II) printing process:
(1) Importing a pre-designed model with STL format, wherein the model consists of two parts, each part corresponds to a metal material, and a printing track is automatically produced by software;
(2) When 3D printing starts, continuously applying pressure to a copper paste injector by an air pump according to a set program, wherein the pressure is 5Mpa, so that copper paste is extruded into filaments from a conical nozzle under stable pressure, moving the copper paste injector according to a preset program, forming the extruded copper filaments on a substrate, and withdrawing the copper paste injector after the first layer of program is finished;
(3) The air pump continuously applies pressure to the iron slurry injector according to a set program, the pressure is 5Mpa, so that the iron slurry is extruded into filaments from the conical nozzle under stable pressure, the iron slurry injector moves according to a preset program, so that the extruded filaments are formed on the substrate, and after the program is finished, the iron slurry injector is withdrawn;
(4) And after the copper slurry injector and the iron slurry injector are alternately moved once, the first layer is formed. Repeating the steps (1) and (2) under the control of a program, and forming layer by layer through reciprocating motion to finally form the bimetallic material three-dimensional part;
(III) carrying out vacuum high-temperature heat treatment on the bimetallic material three-dimensional part, comprising the following steps:
(1) Vacuumizing: putting a bimetal part to be sintered into a sintering furnace, and vacuumizing by using a mechanical pump, wherein the vacuum degree is matched with the properties of two metal slurries, and the vacuum degree is adjusted to be 100Pa, so that an oxide film is partially generated on copper metal powder, the fusion degree of copper particles is reduced, and the shrinkage rate of copper is reduced;
(2) Pyrolysis of the binder: heating the vacuum furnace to 400 ℃ at the speed of 600 ℃/h, keeping the temperature for 2h, waiting for the binder to be completely pyrolyzed, and enabling the three-dimensional part of the bimetallic material to shrink for the first time, wherein the volume of the iron metal part is smaller than that of the copper metal part, which is the reason that the shrinkage rate is large because the binder proportion of the iron metal slurry is large;
(3) Sintering of metal particles: after the binder is pyrolyzed, heating the vacuum furnace to 1050 ℃ at the speed of 600 ℃/h, closing the mechanical pump, stopping vacuumizing, preventing a large amount of copper powder from volatilizing, keeping the temperature for 12h, sintering metal particles, wherein the bimetallic material three-dimensional part shrinks for the second time, the metal particles start to melt, the melting degree of iron particles is low, the melting degree of copper particles is high, and finally the metal volumes of the two parts tend to be consistent;
(4) And (3) cooling: and after the bimetal part is fully sintered, automatically cooling the sintering furnace, and taking out the sample after introducing inert gas into the sintering furnace to prevent the sample from being oxidized in the air.
Iron and copper are two widely used metal materials, such as in the fields of aerospace, electronic devices, medical devices, and the like. However, the bimetallic combination of iron and copper is particularly difficult to manufacture due to several factors, for example, copper is easy to volatilize at high temperature, which makes copper more prone to volume shrinkage, while iron has higher activity, is easy to oxidize at high temperature, and has the problem of volume enlargement. The specific exploration method is as follows: first, since copper has a lower melting point and a higher saturated vapor pressure than iron, the shrinkage of copper is higher than that of iron under the same vacuum high-temperature heat treatment conditions, and thus it is necessary to adjust the binder ratio of copper slurry as small as possible and the binder ratio of iron slurry as large as possible. Secondly, during vacuum high-temperature heat treatment, the proper sintering temperature, the sintering time length and the vacuum degree are adjusted, so that the melting of copper powder particles is as small as possible, the volatilization amount is as small as possible, and the melting degree of iron powder particles is as large as possible. Finally, the shrinkage of the two parts of metal materials is consistent, and parts with excellent performance are obtained.
The invention is further described below by printed physical objects.
Fig. 1-3 are material diagrams of iron-copper bimetallic parts of the invention under different binder ratios and sintering parameters, wherein:
FIG. 1 is a diagram of an iron-copper bimetallic part object obtained by the printing method of the invention;
FIG. 2 is a pictorial view of an iron-copper bimetallic part with inappropriate binder ratio and sintering parameters;
FIG. 3 is a diagram of an iron-copper bimetal part obtained by properly optimizing the proportion of the binder and the sintering parameters.
FIG. 4 is an SEM image of the surface of a bimetal part obtained by the printing method of the present invention; in the figure:
(a) The invention is a drawing of the iron-copper bimetal part manufactured by the invention, and the box is a scanning area of an electron microscope of the drawing (b).
(b) Is SEM image obtained by scanning of an electron microscope, and 5 lines in the area are respectively iron, copper and iron;
it can be seen from the figure that the iron lines or the copper lines are formed by mutual fusion of particles, the pores in the lines are caused by the removal of the binder, which explains the shrinkage mechanism of the invention, the volume of the binder removal and the particle fusion degree determine the size of the metal shrinkage, and in addition, no obvious defect is seen from the figure, which proves that the printing method has the advantage of high precision.
FIG. 5 is an analysis diagram of the internal morphology and elements of the bimetal iron-copper part obtained by the printing method; in the figure:
(a) The cross section of the iron-copper bimetal manufactured by the invention is shown, a square frame shows the area researched by the drawing (b), and the cross section is obtained by cutting through a wire cut electrical discharge machine and grinding and polishing through sand paper;
(b) Is SEM image obtained by scanning electron microscope of the section of the graph (a), which shows the appearance of 6 areas of iron, copper, iron and copper in total, and the box is the area studied in the graph (f);
(c) EDS picture of Fe-Cu element in the area shown in picture (b), the first, third and fifth layer elements are iron, the second, fourth and sixth layer elements are copper, the picture is obtained by electron scanning microscope;
(d) Is an EDS chart of Cu element of the region shown in the chart (b) obtained by an electron scanning microscope;
(e) EDS chart of Fe element in the region shown in the chart (b), which is obtained by an electron scanning microscope;
(f) Is SEM image obtained by scanning electron microscope in the box area of the picture (b), which shows the appearance of 2 areas of iron and copper;
(g) EDS chart of Fe-Cu element of the area shown in figure (f), upper element is iron and lower element is copper, obtained by electron scanning microscope;
(h) Is an EDS chart of Cu element of the region shown in the chart (f), which is obtained by an electron scanning microscope;
(i) Is an EDS diagram of Fe element in the region shown in diagram (f), which is obtained by an electron scanning microscope;
the internal appearance of the iron-copper bimetal part obtained by the printing method is shown in the figures (b) and (f), and no obvious crack is seen at the junction of the iron and the copper materials, so that the bimetal part manufactured by the method has the advantage of good interface combination.
The distribution of elements in the regions shown in (b) and (f) is shown in (c) to (e) and (g) to (i), respectively, and it can be seen that the elements in the figure are independently distributed without alternately mixed regions. This demonstrates that the bimetallic part made by the present invention is free of elemental contamination and has the advantage of being able to deposit specific materials in specific areas.
FIG. 6 is a diagram of a complex iron-copper bimetallic structure manufactured with the optimum binder ratio and sintering parameters of the present invention, in which:
(a) The model is a human vertebra model, the interior of the model is iron metal, the exterior of the model is copper metal, and the model can be applied to the medical field;
(b) The house model is a house model, the left half is made of iron metal, and the right half is made of copper metal, so that the house model can be applied to the field of mold design;
(c) The automobile model is characterized in that the lower part of the automobile model is made of iron metal, and the upper part of the automobile model is made of copper metal, so that the automobile model can be applied to the field of automobile body design.
By printing the real object, the invention can manufacture various complex structures, can realize the deposition of two materials on the same layer, and has multiple potential application values.
Claims (7)
1. A3D printing method of a bimetallic material is characterized by comprising the following steps:
preparing slurry:
(1) Mixing copper metal particles with the diameter of 0.1-200 microns and a binder in a ball mill for 15-60 minutes, wherein the volume ratio of the copper metal particles to the binder is (4~7): 1, thereby obtaining a uniformly mixed copper slurry, the binder being: the mass ratio of the polymer to the solvent is 1:3~5;
(2) Mixing iron metal particles with the diameter of 0.1-200 microns and a binder in a ball mill for 15-60 minutes, wherein the volume ratio of the metal particles to the binder is (1~3): 1, obtaining the uniformly mixed iron slurry, wherein the binder is: the mass ratio of the polymer to the solvent is 1:3~5;
(II) printing process:
(1) Importing a pre-designed model with STL format, wherein the model consists of two parts, each part corresponds to a metal material, and a printing track is automatically produced by software;
(2) When 3D printing starts, the air pump continuously applies pressure to the copper paste injector according to a set program to enable copper paste to be extruded into filaments from the conical nozzle under stable pressure, the copper paste injector moves according to a preset program to enable extruded copper filaments to be formed on the substrate, and after the first layer of program is finished, the copper paste injector is withdrawn;
(3) The air pump continuously applies pressure to the iron slurry injector according to a set program to enable the iron slurry to be extruded into filaments from the conical nozzle under stable pressure, the iron slurry injector moves according to a preset program to enable the extruded filaments to be molded on the substrate, and after the program is finished, the iron slurry injector is withdrawn;
(4) After the copper slurry injector and the iron slurry injector are alternately moved once, the first layer is formed, the copper slurry injector and the iron slurry injector repeat the steps (1) and (2) under the control of a program, and the two steps are formed layer by layer through reciprocating motion, so that the three-dimensional part made of the bimetallic material is finally formed;
(III) carrying out vacuum high-temperature heat treatment on the bimetallic material three-dimensional part, comprising the following steps:
(1) Vacuumizing: placing a bimetal part to be sintered into a sintering furnace, vacuumizing by using a mechanical pump, and adjusting the vacuum degree to be 1-100 Pa so that the copper metal powder partially generates an oxidation film, the fusion degree of copper particles is reduced, and the shrinkage rate of copper is reduced, wherein the vacuum degree is matched with the properties of two metal slurries;
(2) Pyrolysis of the binder: heating the vacuum furnace to 300-400 ℃ at the speed of 600 ℃/h, keeping the temperature for 1-2h, waiting for complete pyrolysis of the binder, wherein the bimetallic material three-dimensional part shrinks for the first time, and the volume of the iron metal part is smaller than that of the copper metal part, which is the reason that the iron metal slurry binder has a large proportion and the shrinkage rate is large;
(3) Sintering of metal particles: after the binder is pyrolyzed, heating the vacuum furnace to 900-1050 ℃ at the speed of 600 ℃/h, closing the mechanical pump, stopping vacuumizing, preventing a large amount of copper powder from volatilizing, keeping the temperature for 3-12h, sintering metal particles, wherein the bimetallic material three-dimensional part shrinks for the second time, the metal particles begin to melt, the melting degree of iron particles is smaller, the melting degree of copper particles is higher, and finally the metal volumes of the two parts tend to be consistent;
(4) And (3) cooling: and after the bimetal part is fully sintered, automatically cooling the sintering furnace, and taking out the sample after introducing inert gas into the sintering furnace to prevent the sample from being oxidized in the air.
2. The 3D printing method of bimetallic material as in claim 1, characterized in that: the polymer comprises polylactic acid (PLA), polyvinyl alcohol (PVA) or chitosan.
3. The method for 3D printing of bimetallic material as in claim 1, wherein: the solvent comprises dichloromethane DCM, water or absolute ethanol solution.
4. The method for 3D printing of bimetallic material as in claim 1, wherein: and (2) when the copper slurry is prepared in the step (I), the rotating speed of the ball mill is 300 to 800r/min.
5. The method for 3D printing of bimetallic material as in claim 1, wherein: and (2) when the iron slurry is prepared in the step (I), the rotating speed of the ball mill is 300 to 800r/min.
6. The 3D printing method of bimetallic material as in claim 1, characterized in that: and (II) the pressure of the copper slurry injector in the step (II) is 0.1-5Mpa.
7. The 3D printing method of bimetallic material as in claim 1, characterized in that: and (II) controlling the pressure of the iron slurry injector to be 0.1-5Mpa.
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