CN109468480B - Method for preparing metal-based composite material by vacuum sheath rolling assisted by pulse electric field - Google Patents
Method for preparing metal-based composite material by vacuum sheath rolling assisted by pulse electric field Download PDFInfo
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- CN109468480B CN109468480B CN201811412613.0A CN201811412613A CN109468480B CN 109468480 B CN109468480 B CN 109468480B CN 201811412613 A CN201811412613 A CN 201811412613A CN 109468480 B CN109468480 B CN 109468480B
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C1/00—Making non-ferrous alloys
- C22C1/04—Making non-ferrous alloys by powder metallurgy
- C22C1/05—Mixtures of metal powder with non-metallic powder
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C47/00—Making alloys containing metallic or non-metallic fibres or filaments
- C22C47/14—Making alloys containing metallic or non-metallic fibres or filaments by powder metallurgy, i.e. by processing mixtures of metal powder and fibres or filaments
Abstract
The invention discloses a method for preparing a metal matrix composite material containing a reinforcing phase by sheath rolling assisted by pulse current, which comprises the following steps: firstly, preparing a composite powder blank, performing heat treatment, then overlapping the composite powder blank with a metal shroud plate subjected to surface treatment, and performing vacuum edge welding to exhaust the air inside to form a vacuum sheathed test piece structure; and then putting the sheath test piece into a rolling mill, connecting a pulse power supply with electric brushes at different positions according to the sheath rolling process, applying current to the sheath surface, and synchronously performing green plasma sintering and sheath electro-plastic rolling. Reasonably controlling current parameters, rolling speed and reduction rate, and obtaining the metal-based composite board with larger size through multi-roll rolling and reasonable sintering time. The invention couples the vacuum sheath rolling with the pulse electric field, can sinter and roll the high-performance metal-based composite plate containing the reinforcing phase, which has large macroscopic size, fine microscopic crystal grains and uniform and dispersed distribution of the reinforcing phase, in a short time, and has the characteristics of high efficiency, low consumption, large-scale and intensive production.
Description
Technical Field
The invention belongs to the technical field of jacket rolling under the assistance of an external field, in particular to a technology for jacket rolling forming of a metal-based composite material assisted by pulse current during sintering, and particularly relates to a method for jacket rolling forming during sintering of an aluminum, magnesium, copper, iron and titanium-based composite material for producing ceramic, graphene or carbon fiber particle reinforced phase through jacket rolling based on the assistance of pulse current.
Background
The rapid development of high-end equipment and manufacturing industry cannot be supported by high-performance materials, and more rigorous requirements are particularly put forward on high parameters such as light weight, strong abrasion, high toughness, corrosion resistance, high temperature resistance, function/structure integration and the like of the materials. The metal-based composite material is a heterogeneous composite material consisting of metal and reinforcing phases such as ceramic, fiber or carbon nano tube particles, has ultrahigh strength while reflecting the metal characteristics, and is an important structure and tool material in various fields of the national civilization. However, the composition, structure and performance of the reinforcing phase and the metal matrix are greatly different, which results in low toughness and plasticity of the finished product, difficult machining, and especially complex synthesis process, and the finished product not only needs to be synthesized at high temperature under vacuum or protective atmosphere, but also is difficult to be made into large or complex-shaped components, thereby seriously stopping the elbow in the application of the relevant fields. The existing preparation method of the metal matrix composite mainly comprises the methods of high-temperature vacuum sintering, spark plasma sintering, self-propagating high-temperature synthesis, hot isostatic pressing forming and the like. Related research and application are greatly advanced, but the methods cannot prepare large-volume components, and have the problems of high equipment requirement, high cost, low efficiency, difficulty in realizing large-scale production and the like. In view of the above, a new method for producing a metal matrix composite material with a large size in a low-cost, large-scale and high-efficiency manner under a vacuum or protective atmosphere condition is urgently needed to be developed, so as to meet a great amount of demands of various industries on the metal matrix composite material.
The powder sheath rolling technology can ensure that the rolling powder is formed under vacuum and near-high temperature state, thereby effectively avoiding the loss, oxidation and grain growth of powder material, and being easy to realize integration and near-net forming. However, the application of the composite material in the preparation of metal-based composite materials is only reported, and the main reasons are that the reinforced phases such as ceramic particles and metal matrixes have large physical-chemical differences, are difficult to wet, and need high-temperature sintering and continuous heat preservation, but even if the reinforced phases are sheathed and rolled at high temperature, the temperature and the heat preservation time of the reinforced phases cannot reach the sintering standard easily.
Disclosure of Invention
In order to obtain a metal matrix composite material component with fine crystal grains and large size and containing a reinforcing phase by adopting an efficient, low-cost and scalable rolling process, the invention aims to provide a method for applying pulse power to obtain a metal matrix composite material componentThe method is applied to a multi-roller mill to sinter the metal matrix composite powder and simultaneously form a sintered part. The method is suitable for different ceramic, graphene or carbon fiber reinforced phases combined with aluminum, magnesium, copper, iron or titanium elementary (alloy) powder, such as B4C ceramic particles and pure aluminum powder.
The invention is realized by adopting the following technical scheme:
a method for preparing a metal matrix composite material by vacuum sheath rolling assisted by a pulse electric field comprises the following steps:
(1) preparation of raw materials
Ceramic, graphene or carbon fiber reinforced phase and simple substance (alloy) powder of aluminum, magnesium, copper, iron or titanium are subjected to mechanical ball milling mixing, and the atomic fraction of the reinforced phase is 3-30%.
(2) Heat treatment and high temperature degassing
And placing the mixed powder of the reinforcing phase and the metal simple substance or the alloy in vacuum or inert gas, heating to 50-90% of the melting point of the metal simple substance or the alloy, keeping the temperature for 60min, and then cooling.
(3) Surface treatment of the plate
According to the simple substance (alloy) of the base metal, a sheath material with the strength close to the strength and high-temperature plasticity and low thermal conductivity is selected, and a metal plate with the thickness of 0.5-3 mm is selected to be cut to be used as a sheath covering plate, so that the length of the plate is 600-1200 mm, and the width of the plate is 100-300 mm.
Selecting water solutions of sulfuric acid, nitric acid, hydrochloric acid, hydrofluoric acid and the like with different proportions according to the composition of an oxide layer to corrode and clean the surface to be contacted of the metal plate and the powder green body, then performing mechanical and sand paper polishing to completely remove the surface oxide layer and expose fresh metal on the surface, ensuring that the surface roughness is 40-110 mu m, repeatedly cleaning with alcohol and acetone solution to remove surface oil stains, and coating water glass and glass lubricant on the surface to be contacted for later use after drying.
(4) Preparing a green powder compact
And (3) feeding the mixed powder obtained in the step (2) into a roller for powder rolling, wherein the rolling environment temperature is 20-80 ℃, the powder does not need to be heated, the green blank size is 597-1197 mm in length, 97-297 mm in width and 1-15 mm in thickness.
(5) Vacuum sheath test piece assembly
Stacking the upper covering plate/powder green body/lower covering plate in sequence, arranging sealing plates at the periphery, wherein the sealing plates at two sides are provided with vacuum holes, placing the packaging test piece in a vacuum chamber before packaging and welding, heating to remove gas at 300 ℃, keeping the temperature for 60min, then cooling to perform vacuum edge part welding to form a packaged test piece, and vacuumizing the interior of the packaged test piece to vacuum degree of 5 × 10 through the vacuum holes, wherein the vacuum degree is low vacuum-1Pa, high vacuum pumping to 1 × 10-2And Pa, after the test piece is cooled, carrying out vacuum seal welding on the vacuum hole.
(6) Rolling and sintering
The method comprises the following steps of putting a sheath test piece into a rolling mill connected with pulse current, wherein the rolling mill at least comprises 3 groups of rollers, the length of the sheath test piece is slightly larger than the axial distance between a first roller and a last roller, electric brushes capable of contacting the surface of the sheath test piece are arranged on two sides of an upper layer of the rollers, sintering of the metal matrix composite material is conducted by using resistance heat and plasma discharge heat generated by the pulse current among powder particles, a positive direct current pulse current generator generates current, a high-voltage output end and a grounding end form a current loop through the electric brushes arranged on the surface of the sheath test piece, the connection and disconnection between a port of the current generator and the electric brushes depend on the rolling stroke of the sheath, and the basic principle is that the most possible region of the sheath and. The feeding process is as follows: the number of the rollers of the rolling mill is 3-5, each group of electric brushes can be connected with the output end and the grounding end of the pulse current generator through electrode leads, and are in contact with the upper surface or the lower surface of the sheath test piece, and the electric brushes are distributed in front of the first group of rollers, behind the last group of rollers and among the groups of rollers, namely electric brushes 1, electric brushes 2, … … and electric brushes n (n is more than or equal to 4 and less than or equal to 6), and are distributed in sequence from the first group of rollers to the last group of rollers; the front end of the sheath test piece firstly enters a rolling mill and contacts with a first group of rollers, then rolling is started, after the front end contacts with a second electric brush 2, the electric brush 1 and the electric brush 2 are respectively connected to an output end and a grounding end, and at the moment, powder green blanks in the sheath between the electric brush 1 and the electric brush 2 are sintered; with the feeding of the sheath, when the front end starts to contact a certain electric brush m (m is more than or equal to 2 and less than or equal to n), the electric brush m-1 is switched off, and the electric brush m and the grounding end are switched on until the electric brush 1 and the electric brush n are respectively connected to the output end and the grounding end, and the maximum sintering area is formed at the moment; and continuing to feed, enabling the rear end of the sheath to leave the electric brush 1, disconnecting the electric brush 1, and connecting the electric brush 2 with an output end, sintering the powder green compact in the sheath between the electric brush 2 and the electric brush n, and connecting the electric brush k +1 to the output end while disconnecting the electric brush k along with the separation of the rear end and a certain electric brush k (k is less than or equal to n-2), wherein the connection method can ensure that as many powder green compacts in the sheath test piece as possible are in a sintered state. To reduce current loss, each set of rolls is made of an insulating material, such as Sialon ceramic rolls.
The current is input to a section to be processed of the sheathed test piece, plasma discharge occurs among particles in the sheath, the temperature is rapidly increased to generate a sintering neck, element diffusion and interface reaction occur, and the green body is rapidly sintered and compact under the synergistic effect of the rolling force; during rolling, multi-pass rolling is carried out by controlling pulse current parameters, rolling reduction and rolling speed, the first-pass reduction is not less than 13%, and the total reduction is 50% -75%; according to different sintering materials, selecting proper rolling pulse current parameters: pulse current density of 200-1000A/mm2The frequency is 300-3000 Hz, and the pulse width is 30-100 mus; in order to ensure enough sintering time, taking a 1000mm sheathed test piece as an example, the rolling speed is 200mm/min, and the rolling speed ensures that the discharge plasma sintering time of more than or equal to 5min is kept at each part of the powder green compact in the sheath. Under the action of high temperature, rolling pressure and current activation, the materials in the sheathed test piece can realize rapid metallurgical bonding among powder particles to form a compact sintered material.
(7) And cooling the sheath material at room temperature, breaking the sheath test piece when the temperature is reduced to be below 100 ℃, and taking out the core block to obtain the ceramic, graphene or carbon fiber reinforced metal matrix composite.
Based on the method, the metal matrix composite material sheath rolling device assisted by the pulse electric field comprises a device for rolling experimental materialsThe device comprises a pulse current power supply for applying pulse current, and a conduction and electric contact device, and is used for a rolling mill for applying multi-pass rolling to experimental materials. The pulse current power supply adopts a pulse current generator, takes IGBT as a digital power module, takes an ultracrystalline soft magnetic alloy material as a transformer iron core, is provided with the functions of voltage and current automatic feedback and system fault diagnosis protection, and has the current peak density of 1000A/mm2The pulse frequency is 100 to 3000 Hz.
Compared with the prior art, the invention has the following advantages and effects:
1. the invention combines an external pulse electric field with a multi-roller mill and is used for preparing the metal matrix composite material containing the reinforcing phase. Because the pulse current passes through the composite material green body, resistance heat and plasma discharge heat are formed at the particle interface and are used as main energy of interface atom diffusion and metallurgical reaction, external radiant heat is not needed, the temperature is rapidly increased only at the particle interface to form a sintering neck, and then element diffusion and interface reaction between particles are caused, the environment temperature is low, the sintering efficiency is greatly improved, and the energy consumption is reduced.
2. The electronic wind caused by the electric pulse can drive elements to diffuse and reduce the apparent activation energy of the interface reaction, and the growth rate of atomic diffusion and the interface reaction is improved. Along with the rapid increase of the temperature of the powder particle interface, when the temperature reaches the melting point of metal or alloy, the material is melted in a contact micro-area to generate a liquid phase, the powder green body is rapidly densified under the synergistic action of a rolling force field to finish sintering, and the grains of a sintered body are refined and the reinforcing phase is dispersed and uniformly distributed through multi-pass rolling. The synergistic effect of the pulse electric field and the rolling force field ensures that the green body is rolled and formed while being sintered, and has better comprehensive performance.
3. The pulse current not only plays a sintering role, but also can cause the electro-plastic effect of the metal plate and the green body, thereby obviously reducing the deformation stress, reducing the rolling force, reducing the energy consumption and simultaneously avoiding the damage of the roller.
4. Different from the traditional vacuum sintering furnace for diffusion sintering, the pulse current-assisted sheathing rolling mode is adopted for sintering and molding green bodies, the limitation of narrow and small dies in the sintering furnace is avoided, the dimensions of sheathed test pieces are flexible, the method is suitable for the production of large-size metal matrix composite members, especially large-size plates, the large-scale production of the members can be realized, and the method has remarkable industrial application prospect.
5. The invention integrates the discharge plasma sintering and the cladding rolling process of the metal-based composite material containing the reinforcing phase into a whole, the cladding rolling promotes the sintering, the electro-plasticity effect is beneficial to reducing the rolling stress, the multi-field coupling synergistic effect of the rolling force field, the pulse electric field and the temperature field is formed, and the purpose of preparing large-size metal-based composite material components in a high-efficiency, low-cost, intensive and large-scale manner is realized.
The invention has reasonable design, combines the pulse current rapid sintering technology with the powder sheath rolling technology, and provides a novel method for integrating sintering and rolling molding of the reinforced phase metal matrix composite. The method comprehensively utilizes the effects of resistance heat and plasma discharge heat generated by pulse current on a heterogeneous interface, activated element diffusion and interface reaction promotion, and the effects of sheath rolling on maintaining vacuum, keeping high temperature such as near and the like, refining crystal grains and forming a large-size component, and places the metal-based composite material under the multi-field coupling action of a temperature field, a pressure field and a pulse electric field to realize the rapid and low-cost sintering and rolling integrated preparation of the large-size metal-based composite component.
Drawings
Fig. 1 shows a schematic diagram of an apparatus for producing a metal matrix composite material based on a wrapper rolling assisted by a pulse current according to the present invention, wherein the arrows indicate the rolling feed direction.
FIG. 2 is a schematic diagram showing the structure of a green-sheathed test piece of the metal matrix composite powder according to the present invention.
In the figure: 1-roll stand, 2-first group of rolls, 3-last group of rolls, 4-middle group of rolls, 5-brush I, 6-brush II, 7-brush III, 8-brush IV, 9-pulse current generator, 10-output end, 11-grounding end, 12-upper covering plate, 13-lower covering plate, 14-seal welding plate, 15-powder green body, 16-welding line, 17-vacuum hole, 18-sheathed test piece, a-sheathed test piece rear end and b-sheathed test piece front end.
Detailed Description
The following provides a detailed description of specific embodiments of the present invention.
A method for preparing a metal matrix composite material by powder sheath rolling assisted by a pulse electric field comprises the following steps: firstly, preparing a composite powder blank, performing heat treatment, then overlapping the composite powder blank with a metal clad plate subjected to surface treatment, performing vacuum edge welding to exhaust the air inside, and forming a vacuum sheath structure to prevent sintering and oxidation of the green blank; and then placing the sheath into a rolling mill, connecting a pulse power supply with electric brushes at different positions according to the sheath rolling process, applying current to the surface of the sheath, and synchronously performing green plasma sintering and sheath electro-plastic rolling.
The components used in the method of the invention comprise a powder green compact sheath test piece structure, a multi-roller mill for rolling the sheath structure, and an electric field generating and conducting device for applying pulse current to the sheath structure.
As shown in FIG. 2, the jacket test piece structure is composed of an upper covering plate 12, a lower covering plate 13, a powder green body 15 and a seal welding plate 14 covering and wrapping the powder green body. The green powder 15 being a metal matrix composite material, e.g. B4C particle reinforced aluminum matrix composite. The upper and lower clad plates 12, 13 are made of simple metal or alloy material, and are made of thin plate with thickness of 0.5-3 mm, such as 2A50 aluminum alloy plate, and the deformation stress of the thin plate is close to that of the dense material corresponding to the metal matrix. The seal welding plate 14 is provided with vacuum holes 17 at positions opposite to the contact positions of the green powder 15 and the upper and lower sheathing plates 12, 13, and is welded to the vacuum side portions of the upper and lower sheathing plates 12, 13. In order to reduce the friction and deformation resistance between the powder green body 15 and the sheath cover plate during the rolling deformation process and prevent the green body from being sintered and adhered with the sheath cover plate, the inner sides of the upper and lower cover plates 12 and 13 and the seal welding plate 14 are uniformly coated with water glass and glass lubricant.
As shown in fig. 1, the multi-roll mill is used for rolling a sheathed test piece, and the rolling force applied to the test piece not only generates compressive stress favorable for sintering of a powder green compact, but also forms the green compact into a plate-shaped structure with a specified thickness. The rolling mill comprises a frame 1, a first group of rollers 2, a middle group of rollers 4 and a last group of rollers 3, the length of a sheath test piece is slightly larger than the axial distance between the first and last rollers, and each group of rollers are made of insulating materials, such as Sialon ceramic rollers. And reasonably controlling current parameters, wherein the first reduction rate is not less than 13 percent, the total reduction rate is 50-75 percent, the rolling speed is 150-200 mm/min, and the large-size metal-based composite plate is obtained through multi-roll rolling and sintering time of 5-8 min.
As shown in fig. 1, the pulse electric field application system is composed of a pulse electric field generator 9, a positive direct current pulse high voltage output terminal 10 and a grounding terminal 11, the number of the electric brushes connected with the output and grounding terminals depends on the rolling process of the sheathed test piece, and the principle is to make as many sheaths as possible in a pulse current loop to increase the sintering time. Taking a three-roll mill as an example for explanation, the specific feeding process is as follows, the front end b of the sheathed test piece firstly enters the mill and starts to roll after contacting with the first group of rollers 2, when the end b contacts with the electric brush II 6, the electric brush I5 and the electric brush II 6 are respectively connected to the output end 10 and the grounding end 11, and at the moment, the sheathed test piece area between the electric brush I5 and the electric brush II 6 can be sintered; as the sheathed test piece is fed, the electric brush m-1 is switched off and the electric brush m and the grounding terminal 11 are switched on while the front end b is in contact with the electric brush m (m is more than or equal to 2 and less than or equal to 4) until the electric brush IV 8 and the grounding terminal 11 are switched on; and continuing feeding, wherein the rear end a of the sheathed test piece leaves the electric brush I5, the electric brush I5 is disconnected and the electric brush II 6 and the output end 10 are connected, powder green bodies in the sheathed test piece between the electric brush II 6 and the electric brush IV 8 can be sintered, the rear end a and the electric brush are contacted and disconnected one by one along with feeding, when the rear end a and the electric brush k (k is more than or equal to 1 and less than or equal to 2) are separated, the electric brush k is disconnected and the electric brush k +1 is connected to the output end 10 simultaneously until the rear end a and the electric brush II 6 are separated, and the regions between the residual electric brush III 7 and the electric brush IV 8 are sintered, so that the connection method can ensure that the most regions.
The pulse current density of the invention is 200-1000A/mm2The frequency is 300-3000 Hz, the pulse width is 30-100 mu s, and proper pulse current parameters are selected according to different powder green body materials and different sheath sizes, and the basic principle is as follows: the smaller the section size of the plate is, the larger the pulse current frequency is; the higher the material strength is, the higher the corresponding pulse width and current density amplitude need to be; the larger the rolling deformation rate is, the larger the pulse width and the current density amplitude are.
In other embodiments of the present invention where the metal matrix composite is produced by wrapper rolling with the assistance of a pulsed current, each set of rolls is made of an insulating material, which may be yttrium stabilized zirconia ceramic.
In other embodiments of the invention for preparing the metal-matrix composite material by rolling the pulse current auxiliary sheath, the number of the rolling mill roller sets can be 1-5, and the axial distance between the first rolling roller and the last rolling roller is slightly less than the length of the sheath test piece.
In other embodiments of the invention where the metal matrix composite is prepared by rolling the pulse current assisted sheath, the material of the upper and lower sheathing plates should match the deformation stress of the green metal substrate, and may be one of elemental metals or alloys of magnesium, aluminum, titanium, and iron.
In other embodiments of the present invention in which the metal matrix composite is prepared by wrapper rolling assisted by pulsed current, the powder green body material may be one of graphene, carbon fiber, ceramic particle or whisker reinforced magnesium, aluminum, iron, titanium, copper matrix composite.
The method has the following remarkable advantages: the sintering and rolling plastic deformation of the metal matrix composite material are carried out simultaneously, pulse current flows through the powder green body to initiate resistance heat and plasma discharge heat among powder particles, the temperature is rapidly increased to form sintering necks among the particles, element diffusion and interface reaction occur, then the interface is rapidly cooled, and the heat preservation time is short. Under the synergistic effect of the pulse current field effect and the rolling force field, the metal-based composite material with refined grains, high density and uniformly distributed enhanced phases can be prepared in a short time; different from the vacuum sintering of the traditional sintering furnace, by means of the vacuum sheath welding mode, the vacuum sintering environment is ensured, the limitation of narrow and small molds in the vacuum furnace is avoided, and large-size metal matrix composite plates can be prepared and molded.
The method for preparing the metal matrix composite by the pulse current assisted vacuum sheath according to the present invention is further described in detail by the following examples.
Example 1
Preparation B based on spark plasma sintering and vacuum sheath rolling4The method for C particle reinforced aluminum matrix composite material comprises the following steps:
1. preparation of the sheath
a. Will contain 15vol% of B4Adding aluminum-based powder of C ceramic particles (10-70 mu m) into a heating furnace filled with inert gas, heating to 500 ℃, drying, degassing at high temperature for 2h, carrying out vacuum ball milling at the rotating speed of 300rpm for 1h, and rolling the powder into a powder green compact with the thickness of 997 × 60 × 1.5.5 mm;
b. cutting a 2A50 aluminum alloy plate into plates of 1000 multiplied by 63 multiplied by 2mm, corroding and cleaning the surface of the metal plate to be contacted with powder by using a 10% sulfuric acid water solution, then performing mechanical and sand paper polishing to completely remove a surface oxide layer and expose fresh metal on the surface, ensuring that the surface roughness is 40-110 mu m, then cleaning and removing oil stains on the surface for multiple times by using alcohol and an acetone solution, and smearing water glass and a glass lubricant on the surface to be contacted for later use after drying;
c. and aligning and stacking the treated green bodies and the metal plates according to the sequence of aluminum alloy/green bodies/aluminum alloy to form a composite layer assembly, welding the side surface of the composite layer with a sealing plate through argon arc welding, forming two vacuum holes at the position of the sealing plate, which is right opposite to the contact surface of the aluminum alloy clad plate/green bodies, extracting interlayer air, forming a vacuum environment in the sheath, and sealing and welding the vacuum holes in a vacuum manner.
2. Pulse current and cluster mill model selection
The maximum current peak density which can be generated by the pulse generator is 1000A/mm2The pulse frequency is 100-3000 Hz; in this embodiment, a 3-roll mill is adopted, the rolls are all Sialon ceramic rolls, and the axial distance between the first roll and the last roll is slightly less than the sheath length of 1000 mm.
3. Pulse current assisted jacket rolling
Putting the sheath composite layer into a rolling mill connected with pulse current, connecting a pulse generator 9 into 220V alternating current, and setting the working parameters as the current density of 700A/mm2The pulse frequency is 900Hz, the pulse width is 80 μm, the pulse power supply is switched on to transmit pulse current to the segment to be sintered and rolled through the electric brush, and the electric brush is switched on sequentially as described above. The reduction rate of each roller is respectively 18 percent, 34 percent and 50 percent, the total reduction rate is 50 percent, the rolling speed is 150mm/min, and the discharge plasma sintering time of more than or equal to 6min can be ensured at each part of the powder green compact in the sheath.
4. Composite material post-treatment
Cooling the sheath at room temperature, breaking the metal plate when the temperature is reduced to below 100 deg.C, and taking out the core block to obtain compact core B4And C, removing a local diffusion layer of the clad plate by further mechanically polishing the surface of the C ceramic particle reinforced aluminum matrix composite sintered plate.
Example 2
The method for preparing the carbon nanotube fiber reinforced magnesium-based composite material based on spark plasma sintering and vacuum sheath rolling comprises the following steps:
1. preparation of the sheath
a. Adding Al powder containing 2wt% of carbon nano tubes into a heating furnace filled with inert gas, heating to 500 ℃, drying, degassing at high temperature for 2h, carrying out vacuum ball milling at the rotating speed of 300rpm for 2h, and rolling the powder into a powder green compact with the size of 997 multiplied by 60 multiplied by 1.5 mm;
b. cutting a 2A50 aluminum alloy plate into plates of 1000 multiplied by 63 multiplied by 2mm, corroding and cleaning the surface of the metal plate to be contacted with powder by using a 10% sulfuric acid water solution, then performing mechanical and sand paper polishing to completely remove a surface oxide layer and expose fresh metal on the surface, ensuring that the surface roughness is 40-110 mu m, then cleaning and removing oil stains on the surface for multiple times by using alcohol and an acetone solution, and smearing water glass and a glass lubricant on the surface to be contacted for later use after drying;
c. and aligning and stacking the treated green bodies and the metal plates according to the sequence of aluminum alloy/green bodies/aluminum alloy to form a composite layer assembly, welding the side surface of the composite layer with a sealing plate through argon arc welding, forming two vacuum holes at the position of the sealing plate, which is right opposite to the contact surface of the aluminum alloy clad plate/green bodies, extracting interlayer air, forming a vacuum environment in the sheath, and sealing and welding the vacuum holes in a vacuum manner.
2. Pulse current and cluster mill model selection
The maximum current peak density which can be generated by the pulse generator is 1000A/mm2The pulse frequency is 100-3000 Hz; in this embodiment, a 3-roll mill is adopted, each group of rolls adopts yttrium-stabilized zirconia ceramic rolls, and the axial distance between the first roll axis and the last roll axis is slightly less than the sheath length of 1000 mm.
3. Pulse current assisted jacket rolling
Putting the sheath composite layer assembly into a rolling mill connected with pulse current, connecting a pulse power supply into 220V alternating current, and setting working parameters to be current density of 600A/mm2Pulse frequency 800Hz and pulse width 60 μm, a pulsed power supply is switched on to deliver a pulsed current through the brushes to the segment to be sintered and rolled, the brush switching-on sequence being as previously described. The reduction rate of each roller is respectively 18 percent, 34 percent and 50 percent, the total reduction rate is 50 percent, the rolling speed is 160mm/min, and the discharge plasma sintering time of more than or equal to 5min can be ensured at each part of the powder green compact in the sheath.
4. Composite material post-treatment
And (3) cooling the sheath at room temperature, breaking the metal plate when the temperature is reduced to be below 100 ℃, taking out the core block to obtain a compact carbon nano tube reinforced aluminum matrix composite material sintered plate, and further mechanically polishing the surface to remove the diffusion part and the oxidation part of the sintered body and the coating plate.
The working principle of preparing the metal matrix composite material by sheath rolling assisted by the pulse electric field is as follows: under the composite action of the temperature field, the current activation and the rolling force field, the discharge plasma sintering and the electro-plastic rolling forming of the metal matrix composite material of the reinforced phase are synchronously completed. Firstly, pulse current generates contact resistance heat and plasma discharge heat through a particle interface, so that an external heat source is replaced, and the temperature between particles of the metal matrix composite material containing the enhanced phase is rapidly increased to a sintering temperature; secondly, the pulse current can obviously reduce element diffusion activation energy and promote the interface reaction rate; and finally, combining a multi-pass rolling force field, so that the powder green compact is rapidly sintered and compact, and meanwhile, the agglomeration of a reinforcing phase and the growth of crystal grains are avoided. The vacuum furnace body is replaced by the vacuum sheath structure, the size of the sintered body is not limited by the volume of the mold any more, the sinterable volume is obviously improved, and rolling forming is realized while sintering.
The invention couples the vacuum sheath rolling with the pulse electric field, can sinter and roll the high-performance metal-based composite plate containing the reinforcing phase, which has large macroscopic size, fine microscopic crystal grains and uniform and dispersed distribution of the reinforcing phase, in a short time, and has the characteristics of high efficiency, low consumption, large-scale and intensive production.
The invention has been described in detail with reference to the drawings and examples, but the above description is only intended to illustrate the invention and not to limit the invention in any way. And the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments, and all other embodiments that can be obtained by one skilled in the art based on the embodiments of the present invention without any inventive work belong to the protection scope of the present invention.
Claims (5)
1. A method for preparing a metal matrix composite material by vacuum sheath rolling assisted by a pulse electric field is characterized by comprising the following steps: the method comprises the following steps:
(1) preparation of raw materials
Mixing a ceramic reinforcing phase and simple substance powder of aluminum, magnesium, copper, iron or titanium or alloy powder of the ceramic reinforcing phase and the aluminum, magnesium, copper, iron or titanium by mechanical ball milling, wherein the reinforcing phase accounts for 15% by volume;
(2) heat treatment and high temperature degassing
Placing the mixed powder of the reinforcing phase and the metal simple substance or the alloy in vacuum or inert gas, heating to 50-90% of the melting point of the metal simple substance or the alloy, keeping the temperature for 60min, and then cooling;
(3) surface treatment of the plate
Selecting a metal plate with the thickness of 0.5-3 mm as a sheathing covering plate, carrying out corrosion cleaning on the surface of the metal plate to be contacted with the powder green body, then carrying out mechanical and sand paper polishing to completely remove a surface oxide layer and expose a fresh metal layer on the surface, ensuring that the surface roughness is 40-110 mu m, carrying out multiple cleaning with alcohol and acetone solution to remove surface oil stains, and smearing water glass and glass lubricant on the surface to be contacted for later use after drying;
(4) preparing a green powder compact
Feeding the mixed powder obtained in the step (2) into a roller for powder rolling, wherein the rolling environment temperature is 20-80 ℃, and the thickness of the green body is 1-15 mm;
(5) vacuum sheath test piece assembly
Stacking the upper/powder green/lower covering plates in sequence, arranging sealing plates around the upper/powder green/lower covering plates, wherein the two sides of the upper/powder green/lower covering plates are provided with sealing platesThe seal welding plates are all provided with vacuum holes, the seal welding plates are placed in a vacuum chamber for heating and degassing before sheath welding, the heating temperature is 300 ℃, the heat preservation time is 60min, then the vacuum edge part welding is carried out while cooling to form a sheath test piece, the interior of the sheath test piece is pumped to vacuum through the vacuum holes, and the vacuum degree is low-vacuum pumping to 5 × 10-1Pa, high vacuum pumping to 1 × 10-2Pa, after the test piece is cooled, carrying out vacuum seal welding on the vacuum hole;
(6) rolling and sintering
Putting the sheath test piece into a rolling mill connected with pulse current, wherein the rolling mill at least comprises three groups of rollers, and the axial distance between the first roller and the last roller is less than the length of the sheath test piece; electric brushes capable of contacting with the surface of the sheathed test piece are arranged on two sides of the upper layer roller, a pulse current generator generates current, a high-voltage output end and a grounding end form a current loop through the electric brushes arranged on the surface of the sheathed test piece, the current loop is input to a section to be processed of the sheathed test piece, the connection and disconnection of the port of the current generator and the electric brushes depend on the rolling stroke of the sheath, and during rolling, multi-pass rolling is carried out by controlling pulse current parameters, rolling reduction rate and rolling speed, the first pass reduction rate is not less than 13%, and the total reduction rate is 50% -75%; wherein, the setting parameters of the pulse current generator are as follows: pulse current density of 200-1000A/mm2The frequency is 300-3000 Hz, and the pulse width is 30-100 mus; the rolling speed ensures that the discharge plasma sintering time of more than or equal to 5min is kept at each part of the powder green body in the sheathed test piece;
(7) and cooling the sheath material at room temperature, breaking the sheath test piece when the temperature is reduced to be below 100 ℃, and taking out the core block to obtain the ceramic reinforced metal matrix composite.
2. The method for preparing the metal matrix composite material by the vacuum sheath rolling assisted by the pulsed electric field according to claim 1, wherein the method comprises the following steps: each set of rollers of the rolling mill is made of insulating materials.
3. The method for preparing the metal matrix composite material by the vacuum sheath rolling assisted by the pulsed electric field according to claim 1, wherein the method comprises the following steps: the thickness of the sheathed test piece is 0.5-3 mm, the length is 600-1200 mm, and the width is 100-300 mm.
4. The method for preparing the metal matrix composite material by the vacuum sheath rolling assisted by the pulsed electric field according to claim 1, wherein the method comprises the following steps: the number of the rollers of the rolling mill is 3-5, each group of electric brushes is connected with the output end and the grounding end of the pulse current generator through an electrode lead and is in contact with the upper surface or the lower surface of the sheath test piece, the electric brushes are respectively an electric brush 1, an electric brush 2, an electric brush … … and an electric brush n which are distributed before the first group of rollers, after the last group of rollers and among the groups of rollers, wherein n is more than or equal to 4 and less than or equal to 6, and the electric brushes are sequentially distributed from the first group of rollers to the last group of; the front end of the sheathed test piece firstly enters a rolling mill and contacts with a first group of rollers, then rolling is started, after the front end contacts with the electric brush 2, the electric brush 1 and the electric brush 2 are respectively connected to an output end and a grounding end, and at the moment, powder green blanks in the sheath between the electric brush 1 and the electric brush 2 are sintered; with the feeding of the sheath, when the front end starts to contact the electric brush m, wherein m is more than 2 and less than or equal to n, the electric brush m-1 is disconnected, and the electric brush m is connected to the grounding end until the electric brush 1 and the electric brush n are respectively connected to the output end and the grounding end, and the maximum sintering area is formed at the moment; and continuing feeding until the rear end of the sheath leaves the electric brush 1, disconnecting the electric brush 1 and connecting the electric brush 2 to an output end, sintering the powder green bodies in the sheath between the electric brush 2 and the electric brush n, and connecting an electric brush k +1 to the output end while disconnecting the electric brush k along with the separation of the rear end and the electric brush k, wherein k = n-2, so as to ensure that the most powder green bodies in the sheath test piece are in a sintered state.
5. The method for preparing the metal matrix composite material by the vacuum sheath rolling assisted by the pulsed electric field according to claim 4, wherein the method comprises the following steps: the materials of the rollers are Sialon ceramics or yttria-stabilized zirconia ceramics, and the rolling speed is 150-500 mm/min.
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| CN112916740B (en) * | 2021-01-22 | 2022-08-02 | 北京航空航天大学 | Micro-channel pulse current-assisted asynchronous roll forming method for array difficult to deform |
| WO2023014986A1 (en) * | 2021-08-05 | 2023-02-09 | University Of Maryland, College Park | Systems and methods for pipe repair using rapid sintering |
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