CN113649532A - Low-cost preparation of Ni-Ni3Method for producing Si eutectic autogenous composite material - Google Patents
Low-cost preparation of Ni-Ni3Method for producing Si eutectic autogenous composite material Download PDFInfo
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D7/00—Casting ingots, e.g. from ferrous metals
- B22D7/005—Casting ingots, e.g. from ferrous metals from non-ferrous metals
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D27/00—Treating the metal in the mould while it is molten or ductile ; Pressure or vacuum casting
- B22D27/04—Influencing the temperature of the metal, e.g. by heating or cooling the mould
- B22D27/045—Directionally solidified castings
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- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B11/00—Single-crystal growth by normal freezing or freezing under temperature gradient, e.g. Bridgman-Stockbarger method
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- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B28/00—Production of homogeneous polycrystalline material with defined structure
- C30B28/04—Production of homogeneous polycrystalline material with defined structure from liquids
- C30B28/06—Production of homogeneous polycrystalline material with defined structure from liquids by normal freezing or freezing under temperature gradient
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- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
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- C30B33/00—After-treatment of single crystals or homogeneous polycrystalline material with defined structure
- C30B33/02—Heat treatment
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Abstract
The invention relates to a method for preparing Ni-Ni with low cost3A process for preparing the eutectic composite Si-eutectic alloy features that the Ni-Si hypereutectic alloy is prepared according to the binary equilibrium phase diagram of Ni-Si, so reducing the content of Ni in alloy and preparing Ni-Si hypereutectic alloy ingot, and the Bridgman directional solidification technique is used to prepare the eutectic composite Ni-Si material with alpha-Ni phase and Ni-Ni phase3Si eutectic phase and Ni31Si12Metastable phase composition. Eliminating metastable phase by proper heat treatment process to obtain Ni-Ni3Eutectic structure of the Si full-lamellar layer. The invention can save the use amount of rare metal Ni and reduce the preparation cost of the material by designing the alloy components, and can improve the comprehensive mechanical property of the material by a heat treatment process to obtain Ni-Ni meeting the service requirement3And a Si full-layer eutectic structure.
Description
Technical Field
The invention belongs to the technical field of metallurgy, relates to reduction of material preparation cost and improvement of comprehensive performance and service performance, and relates to low-cost preparation of Ni-Ni3A method for producing Si eutectic authigenic composite material.
Background
Intermetallic compound Ni3Si has excellent performances of high strength, high temperature resistance, oxidation corrosion resistance, abnormal R effect and the like, and has wide application prospect in the field of high-temperature structural materials. However, Ni3The low ductility, low fracture toughness and poor high temperature creep resistance of Si materials greatly limit the practical application of Si materials as structural materials.
At the same time, Ni-Ni3The Si eutectic authigenic composite material is widely used for manufacturing high-performance heat-end key parts such as discs, blades and the like of aviation, aerospace, ship and tank engines and other power devices due to excellent performances such as corrosion resistance, abrasion resistance, high strength and the like. Ni-Ni prepared by Bridgman directional solidification technology3The eutectic layer spacing of the Si eutectic in-situ composite material is reduced, the structure is refined, but complete equilibrium solidification cannot be ensured in the solidification process, which leads to metastable phase Ni31Si12Increases the hardness and brittleness of the material, the overall properties of the material become unstable, and the price of metallic Ni is expensive, making Ni — Ni expensive3The preparation cost of the Si eutectic authigenic composite material is high.
Disclosure of Invention
To overcome the disadvantages of the prior art, Ni-Ni is reduced3The cost of Si eutectic authigenic composite material preparation, the improvement of solidification structure and the elimination of metastable phase Ni31Si12The invention provides a method for preparing Ni-Ni with low cost, which can obtain full-lamellar eutectic structure and improve the comprehensive performance of the material3A method for producing Si eutectic authigenic composite material. The Ni-Si hypereutectic alloy is prepared by a Ni-Si binary equilibrium phase diagram, the proportion of rare metal Ni in the alloy is reduced, and the Ni-Ni is reduced3Si preparation cost, Ni-Ni preparation by Bridgman directional solidification technology3The Si eutectic authigenic composite material improves the material structure through a proper heat treatment process and eliminates metastable phase Ni31Si12The hardness and brittleness of the material are reduced, and the comprehensive performance of the material is improved.
In order to achieve the purpose, the invention adopts the technical scheme that:
low-cost preparation of Ni-Ni3A method of Si eutectic authigenic composite materials, comprising:
wherein, the Ni-Si binary hypereutectic alloy uses bulk Si with the purity of 99.999 percent and Ni particles with the purity of 99.99 percent as raw materials. In the prepared Ni-Si binary hypereutectic alloy, the content of Ni is less than or equal to 88 percent, and the content of Si is more than or equal to 12 percent.
specifically, the Ni-Si binary hypereutectic alloy is smelted in a vacuum induction smelting furnace with high-purity Ar atmosphere at the temperature of 1143 ℃ to prepare a Ni-Si hypereutectic alloy ingot.
wherein the Bridgman directional solidification is carried out under the condition of high temperature gradient, the temperature gradient is 150-200K/cm, the directional solidification rate is adjustable within the range of 0.1-900 mu m/s, and the vacuum degree is 4.0 multiplied by 10-2Pa, and the precision of lifting data is +/-2 mu m/m. The solidification rate is 6-40 mu m/s during Bridgman directional solidification, and as the solidification rate increases, metastable phase Ni in the material tissue31Si12The content of (c) increases.
Step 4, heat treatment is carried out on the Ni-Si hypereutectic in-situ composite material to lead Ni31Si12Metastable phase elimination to obtain Ni-Ni3Full lamellar eutectic structure of Si, i.e. Ni-Ni3The Si eutectic authigenic composite material.
Wherein, the heat treatment is carried out in a high-temperature vacuum tube furnace, the temperature range is 950 ℃ to 1050 ℃, the heat preservation is carried out, and then the furnace cooling is carried out to the room temperature.
The Rockwell hardness of the Ni-Si hypereutectic in-situ composite material obtained by the invention is 58.53-64.33 HRC, the Vickers hardness is 678.86-825.46 HV, and the metastable phase Ni of the Ni-Si hypereutectic in-situ composite material obtained by selecting the Bridgman directional solidification rate of 40 mu m/s is eliminated by heat treatment31Si12Then, Ni-Ni3The Rockwell hardness of the Si eutectic authigenic composite material is 46.5HRC, and the Vickers hardness is 428 HV.
Compared with the prior art, the invention obtains the Ni-Ni of the full eutectic structure with good high-temperature mechanical properties such as excellent high-temperature creep resistance, excellent fracture resistance, excellent room-temperature plasticity and the like through a proper heat treatment process3The invention not only reduces Ni-Ni but also provides a Si eutectic authigenic composite material3Preparation cost of Si eutectic authigenic composite material, and for Ni-Ni3The practical application of the Si eutectic authigenic composite material is importantThe theoretical value of (A).
Drawings
FIG. 1 is a Ni-Si binary equilibrium phase diagram.
FIG. 2 is a structural morphology diagram of a vacuum induction melting Ni-Si binary hypereutectic alloy.
FIG. 3 shows Bridgman directional solidification of Ni-Ni3And (5) a Si eutectic structure morphology graph.
FIG. 4 is a cross-sectional morphology of a microstructure of Bridgman directionally solidified Ni-Si hypereutectic in-situ composite material, wherein the solidification rate of (a) is 6 μm/s; (b) the solidification rate of (2) is 9 μm/s; (c) the coagulation rate of (2) is 25 μm/s; (d) the solidification rate of (2) was 40 μm/s.
FIG. 5 is a longitudinal sectional morphology of a Bridgman directionally solidified Ni-Si hypereutectic in-situ composite material structure, wherein the solidification rate of (a) is 6 μm/s; (b) the solidification rate of (2) is 9 μm/s; (c) the coagulation rate of (2) is 25 μm/s; (d) the solidification rate of (2) was 40 μm/s.
FIG. 6 is a structural diagram of a Bridgman directional solidification apparatus.
FIG. 7 is a schematic view of the principle of directional solidification.
FIG. 8 is a view showing the structure of a high-temperature vacuum tube furnace apparatus.
FIG. 9 shows Ni-Ni of the full-thickness microstructure obtained after heat treatment3And (3) a structural morphology graph of the Si eutectic authigenic composite material.
Detailed Description
The embodiments of the present invention will be described in detail below with reference to the drawings and examples.
Low-cost preparation of Ni-Ni3A method of Si eutectic authigenic composite materials, comprising:
Wherein Si is bulk Si with a purity of 99.999% as a raw material, Ni is Ni particles with a purity of 99.99% as a raw material, and the content of Ni is less than or equal to 88%, and the content of Si is more than or equal to 12%
And 2, preparing the prepared Ni and Si into a Ni-Si hypereutectic alloy ingot through vacuum induction melting.
According to the equilibrium phase diagram of the Ni-Si binary alloy, the intermetallic compound Ni with low density, high strength and oxidation resistance is generated when the Ni-Si binary alloy is solidified near the eutectic point3Si, and after the Si and the Ni are compounded to generate eutectic reaction, the fracture toughness and the creep resistance of the material are improved. From the temperature during smelting, the melting point of metal Ni is higher, the melting point of simple substance Si is low, and the temperature at the eutectic point after compounding is 1143 ℃, which is lower than the melting point of metal Ni, thereby being more beneficial to smelting. Comprehensively considering and selecting alloy components near the eutectic point of Ni-Si for smelting. Specifically, the Ni-Si binary alloy is smelted in a vacuum induction smelting furnace with high-purity Ar atmosphere at the temperature of 1143 ℃ to prepare the Ni-Si hypereutectic alloy ingot.
Formation of Ni as described above3Si intermetallics undergo an inclusion reaction and a eutectoid reaction during cooling. Inclusion reaction Ni + alpha → beta-Ni3Si is in the primary phase Ni3Local areas where Si contacts the secondary phase a occur. Eutectoid reaction of Ni3Si→β-Ni3Primary phase Ni of Si + gamma3The growth morphology of Si can be substantially maintained up to room temperature.
Meanwhile, the rare metal Ni is expensive, and the hypereutectic alloy components near the eutectic point of Ni-Si are comprehensively considered and selected for smelting to obtain the intermetallic compound Ni3And the proportion of Ni in the alloy is reduced and the preparation cost of the material is reduced while Si is contained.
Lateral heat dissipation is avoided by the Bridgman directional solidification process, a large temperature gradient is generated in the alloy melt close to the solid-liquid interface, the melt obtains heat flow in a single direction perpendicular to the solid-liquid interface, and a stable crystallization core is not arranged in the alloy melt in the front end direction of crystal growth. The solidification structure of the obtained Ni-Si hypereutectic composite material subjected to Bridgman directional solidification is a lamellar microstructure which is regularly arranged, fine in spacing and uniform.
The Ni-Si hypereutectic authigenic composite material tissue prepared by Bridgman directional solidification generates metastable phase Ni due to non-equilibrium solidification31Si12The hardness and brittleness of the material are increased.
Wherein the Bridgman directional solidification is carried out under the condition of high temperature gradient, the temperature gradient is 150-200K/cm, the directional solidification rate is adjustable within the range of 0.1-900 mu m/s, and the vacuum degree is 4.0 multiplied by 10-2Pa, the precision of lifting data is +/-2 mu m/m, and the precision of lifting data of the Ni-Si hypereutectic alloy sample is +/-2 mu m/s.
In the invention, the Bridgman directional solidification is carried out at a solidification rate of 6-40 μm/s. When the solidification rate is 6-40 mu m/s, the alloy solidification structure is in a regular lamellar shape, the solidification rate is increased, the supercooling degree is increased, and the metastable phase content is increased.
The Ni-Si hypereutectic in-situ composite material prepared by Bridgman directional solidification has the advantages that the unidirectional heat flow of the directional solidification inhibits the formation of transverse grain boundaries, so that the fatigue resistance and high-temperature creep resistance of the material are improved. At the same time, addition of ductile metal Ni makes Ni3The brittleness of the Si intermetallic compound is improved, so that the material has excellent high-temperature comprehensive mechanical properties.
Step 4, metastable phase Ni31Si12The presence of (2) gives the material high hardness and brittleness to Ni-Ni3The Si eutectic autogenous composite is disadvantageous, inter alia, owing to suitable heatTreatment of Ni in metastable phase31Si12Eliminating to obtain Ni-Ni with even lamellar microstructure and good comprehensive performance3Eutectic structure of fully lamellar Si, i.e. Ni-Ni3The Si eutectic authigenic composite material.
Because, when the Bridgman directional solidification rate is increased, the Bridgman directional solidification Ni-Si hypereutectic authigenic composite material structure metastable phase Ni31Si12The content of the Ni-Si eutectic in-situ composite material is increased, so that the Ni-Si hypereutectic in-situ composite material with the Bridgman directional solidification rate of 40 mu m/s is selected for heat treatment to ensure that the metastable phase Ni31Si12Is eliminated to obtain Ni-Ni3Full lamellar eutectic structure of Si, i.e. Ni-Ni3The Si eutectic authigenic composite material has guiding significance for the heat treatment process of the material and the elimination of metastable phase at low solidification rate. Wherein the heat treatment process is carried out in a high-temperature vacuum tube furnace, the temperature range of the heat treatment process is 950-1050 ℃, the heat preservation is carried out, and then the furnace is cooled to the room temperature.
The microstructure of the metal material determines the mechanical property of the metal material, and as the full lamellar microstructure can generate larger crack tip strain, different crystal orientations and crystal structures at two sides of a lamellar phase interface can also prevent cleavage cracks from crossing the phase interface, thereby increasing the crack propagation resistance, the lamellar eutectic structure has better high-temperature mechanical properties such as high-temperature creep resistance, fracture resistance, room-temperature plasticity and the like. In the invention, the Rockwell hardness of the Ni-Si hypereutectic in-situ composite material is 58.53-64.33 HRC, the Vickers hardness is 678.86-825.46 HV, and the metastable phase Ni is eliminated by heat treatment31Si12Then, the Bridgman directional solidification and solidification rate is 40 mu m/s Ni-Ni3The Rockwell hardness of the Si eutectic authigenic composite material is 46.5HRC, and the Vickers hardness is 428 HV. (variable range values), see, Ni-Ni3After proper heat treatment, the hardness of the Si hypereutectic authigenic composite material is obviously reduced, and the comprehensive performance is obviously improved.
The principle of the invention comprises: in the case of Bridgman-oriented solidification, since solidification is carried out under non-equilibrium conditions, non-equilibrium solidification is carried out at a constant temperatureNi which is a stable phase with Gibbs free energy ratio in the presence of pressure, components and the like3Higher Si phase Ni31Si12Then, there must be a driving force to make the atom reach the activated state in the structure transformation process, once the atom reaches the activation energy barrier, the atom must reach the final state with lower energy, at this moment, metastable phase Ni31Si12Transformation into stable Ni3A Si phase. Therefore, the metastable phase Ni can be obtained by heat treatment of the directionally solidified Ni-Si hypereutectic in-situ composite material31Si12Transformation into stable phase Ni3And (3) Si. The metastable phase Ni can be completely eliminated by a proper heat treatment process31Si12Obtaining Ni-Ni of full lamellar eutectic structure3The Si eutectic authigenic composite material meets the actual use requirement. The selection of alloy components has great influence on the compound components and crystal forms of the final solidification structure, and the Ni-Si alloy has various compound forms at room temperature, and can generate an intermetallic compound Ni with low density, high strength and oxidation resistance when being solidified near a eutectic point3Si, according to the equilibrium phase diagram of the Ni-Si binary alloy, the component composition range is enlarged, the Ni proportion is reduced, and the Ni-Si hypereutectic alloy is prepared, so that the material preparation cost is reduced.
FIG. 2 is a vacuum induction melting morphology diagram of a Ni-Si eutectic alloy, FIG. 3 is a Bridgman directional solidification Ni-Si eutectic in-situ composite material structure morphology diagram, and it can be seen from FIG. 2 that the Ni-Si binary eutectic alloy structure without directional solidification is an irregularly arranged dendritic structure and is thick. The heat dissipation of the Ni-Si eutectic alloy solution along all directions is almost the same during vacuum induction melting, crystals grow freely along all directions to present a dendritic crystal structure, and the alloy crystals do not obtain a high temperature gradient during the vacuum melting process, so that the enough growth time of the crystals is given, and the structure is relatively thick. The structure of the directionally solidified Ni-Si eutectic alloy is shown in FIG. 3, and it can be clearly seen that the directionally solidified Ni-Si eutectic alloy sample has lamellar microstructure with regular arrangement, fine and uniform spacing. This is because the directional solidification process avoids lateral heat dissipation, and produces a large temperature gradient in the alloy solution near the solid-liquid interface, so that the solution obtains a heat flow perpendicular to the single direction of the solid-liquid interface, and the alloy solution in the direction of the crystal length front end has no stable crystal core.
According to the invention, the Bridgman directional solidification rate is 6-40 μm/s, and when the solidification rate is 6-40 μm/s, the prepared material tissue has a regular lamellar structure, as shown in (a), (b), (c) and (d) in fig. 4 and fig. 5. The structure consists of alpha-Ni phase and eutectic phase Ni-Ni3Si phase and metastable phase Ni31Si12And (4) forming. alpha-Ni phase and Ni in eutectic structure3The Si layers are alternately grown in a sheet shape. When the eutectic crystallizes, the alpha-Ni phase and Ni3The two phases of Si phase grow side by side, and the growth direction of the two phases and the solid-liquid interface keep a macroscopic flat interface. With lamellar Ni-Ni3Ni-Ni of Si eutectic structure3The Si authigenic composite material has excellent high-temperature creep resistance, fracture resistance and room-temperature plasticity.
The bridgman directional solidification technique was performed according to the bridgman directional solidification apparatus shown in fig. 6, and a Ni — Si hypereutectic in-situ composite material was obtained by bridgman directional solidification. The equipment mainly comprises a PCL control center, a vacuumizing device system, a heating control system, a drawing device and the like, wherein a circulating cooling water pipeline with a water inlet 19 and a water outlet 12 is arranged outside a heating furnace, the heating control system mainly comprises a heat insulation lining 14 and a heating rod 13 which are arranged on a heating furnace wall, the drawing device mainly comprises a drawing rod 17 which extends into the heating furnace from the bottom of the heating furnace, the top end of the drawing rod 17 is connected with a corundum tube for placing a test rod 15, liquid metal 16 is arranged outside the drawing rod 17 and serves as metal cooling liquid, the liquid metal 16 is Ga-1n-Sn alloy, the alloy has low melting point, is liquid at room temperature, has excellent cooling capacity and is free of pollution to a cooling body, and the output of an alternating current motor 18 is connected with the drawing rod 17 to control the drawing action of the drawing device.
In combination with the schematic diagram of the directional solidification principle in FIG. 7, the working process of the device is as follows:
the test bar 15 is Ni-Si binary alloy blank bar, and is loaded into a corundum tube, the corundum tube is fixed on a drawing rod 17 which is 1cm protruded out of the liquid level of liquid metal 16, in order to ensure constant temperature gradient, a cooling zone (liquid metal 16) and a heating zone (heating furnace) are vertically separated by a heat insulation plate 23, wherein the heat insulation plate 23 is made of high-purity alumina baking-free bricks, a high-purity thicker graphite sleeve 21 can be arranged in the heating furnace to be sleeved outside the corundum tube and play a role of heating and heat preservation together with a heat insulation bushing 14, and meanwhile, the graphite sleeve 21 can also reduce the electromagnetic disturbance influence of an external field on the directional growth of alloy melt. Cleaning a furnace body, sealing the furnace body, vacuumizing the furnace body, filling argon when the furnace body is vacuumized to a specified vacuum degree, opening circulating cooling water to ensure the normal operation of experimental equipment, opening a heating power supply, gradually adjusting input power to gradually melt the alloy, adjusting the temperature to 1600 ℃, preserving the temperature for a period of time, setting a drawing speed (6-40 mu m/s) and a stroke in a PCL control system after the alloy is completely melted, and drawing. And when the sample is drawn to a specified stroke, pressing a stop button to stop drawing, closing a heating power supply, opening a furnace door after the sample is cooled to room temperature, and taking out the sample.
Wherein, the molten alloy liquid 26 in the corundum tube enters into the liquid metal 16 to start crystallization when moving downwards, and the crystals grow gradually along the opposite direction of heat flow along with the descending of the corundum tube to realize directional solidification. Wherein 24 is the directionally solidified Ni-Si hypereutectic composite material, 25 is the unmelted as-cast alloy 22 is an induction coil, and is used as heating equipment for melting the Ni-Si as-cast alloy in the corundum tube. When an alternating current with a certain frequency passes through the induction coil 22, an alternating magnetic field with the same frequency as the current change frequency is generated inside and outside the induction coil, and a metal workpiece is placed in the induction coil, so that an induced current with the same frequency and the opposite direction as the induction coil is generated in the workpiece under the action of the magnetic field. The eddy current, commonly referred to as eddy current, converts electrical energy into thermal energy due to the induced current forming a closed loop along the surface of the workpiece, rapidly heating and melting the workpiece.
The process parameters for Bridgman directional solidification by using the equipment are as follows:
the smelting temperature is 1580-1680 ℃, the temperature gradient is 150-200K/cm, the directional solidification rate can be adjusted within the range of 0.1-900 mu m/s, and the maximum vacuum degree is 6.2 multiplied by 10-4Pa～4.0×10-2Pa, and the lifting data precision of the sample is +/-2 mu m/m.
The following is an example of the operation of Bridgman directional solidification to prepare a Ni-Si hypereutectic in-situ composite material with lamellar structure:
the corundum tube is fixed on the pull rod, and then a test rod for linear cutting is placed in the corundum tube, so that the corundum tube and the test rod are located at the center of the graphite sleeve. The mechanical pump and the molecular pump are sequentially turned on to vacuumize until the vacuum degree is 4.0 × 10-2And (3) regulating the heating power to be 2.5Kw, 5Kw and 7Kw step by step when Pa, closing the molecular pump and the mechanical pump when the composite vacuum count value is reduced to 0 during heating, and drawing according to the set drawing speed and drawing stroke (the drawing speed is the speed of the sample moving downwards into the cooling liquid, for example, the drawing stroke of 6 mu m/s refers to the distance of the downward movement) after heating for 20 min. And (3) after drawing is finished at the drawing speed of 6-40 mu m/s, turning off the heating power supply, cooling circulating water along with the furnace after 30min, completely cooling the directional solidification sample after 90min, and taking out the directional solidification sample from the furnace.
As shown in FIGS. 4 and 5 (a), (b), (c) and (d), the cross-sectional and longitudinal sectional profiles of the structure of the Ni-Si hypereutectic in-situ composite material are shown when the solidification is performed by Bridgman directional solidification at solidification rates of 6 μm/s, 9 μm/s, 25 μm/s and 40 μm/s, respectively, and it can be seen from the profiles that the solidification structure is composed of an alpha-Ni phase and Ni-Ni phase3Si eutectic phase, metastable phase Ni31Si12Phase composition.
Metastable phase Ni31Si12The material is a complex hexagonal structure, the brittleness of the material is increased due to the existence of the metastable phase, the use performance of the material is seriously influenced, the Ni-Si hypereutectic in-situ composite material with the directional solidification rate of 40 mu m/s is subjected to heat treatment in a high-temperature tubular heating furnace at the temperature range of 950-1050 ℃, and the heat is preserved for a proper time, so that the metastable phase Ni can be subjected to heat treatment31Si12Completely eliminated.
According to the high-temperature vacuum tube furnace equipment shown in fig. 8, the heat treatment process is executed, the equipment comprises a furnace body 1, a furnace tube 2 is arranged in the furnace body 1, two ends of the furnace tube 2 extend out of a flip-type furnace body 1, a sample storage plate is arranged in the furnace tube 2, crucible placing holes are formed in the sample storage plate, fire blocking bricks 7 are placed at openings at two ends of the furnace tube, resistance wires 3 are arranged in the flip-type furnace body 1 and at positions corresponding to the outer wall of the furnace tube 2, one end of the furnace tube 2 is connected with an air inlet metal tube 9, the other end of the furnace tube 2 is connected with an air outlet metal tube 10, a pneumatic regulating valve 11 is arranged on the air inlet metal tube 9, and the air inlet metal tube 9 and the air outlet metal tube 10 are connected with the furnace tube 2 through a flange 14 and a flange 15 respectively.
With reference to the schematic diagram of the high-temperature vacuum tube furnace in FIG. 8, the operation process of the device is as follows:
designing a lifting temperature curve, wherein the heating rate is not more than 10 ℃/min, and the cooling rate is less than 15 ℃/min. Cleaning the environment, checking that the oil line of the mechanical pump is above the marked line, removing the two end covers of the furnace tube 2, and cleaning the interior of the furnace tube 2 by using a dust collector. Placing the sample in a crucible on a sample storage plate in the furnace tube 2, pushing the sample storage plate to the middle part of the furnace tube 2, installing two end covers of the furnace tube 2, and confirming that the sealing gasket falls into the groove. And (3) connecting an Ar gas path, connecting the gas outlet end 10 of the tube furnace, opening the gas inlet valve of the tube furnace, closing the power supply of the vacuum pump, opening the gas outlet valve, and evacuating the furnace tube 2 and the gas pipeline. When the pointer of the vacuum gauge reaches the end, the air outlet valve is closed, and the air inlet valve is closed. The main valve of the gas cylinder is opened by rotating the knob anticlockwise, the pressure reducing valve of the outlet is opened slowly by rotating the knob clockwise, and the gas pressure of the outlet is kept at 2 small grids. And turning the knob anticlockwise, slowly opening the air inlet valve of the tube furnace, and paying close attention to the pressure meter of the tube furnace to confirm that the air pressure is below. When the air pressure of the tube furnace gas pressure gauge is stable, the air inlet valve of the tube furnace is closed, the air outlet valve is opened, the vacuum is pumped, and the air outlet valve of the tube furnace is closed. Repeating the steps 4 and 5 twice, turning off the mechanical pump, and opening the air inlet valve of the tube furnace. The method comprises the steps of turning on a main power supply of the tube furnace, turning on a panel power supply, starting a panel to enable the instrument to be in an initial state, setting heating temperature and heat preservation time, starting the heating power supply, and observing an ammeter and a voltmeter. The pressure gauge is observed and if the pressure is too high, the outlet valve needs to be opened for air bleeding. After the program operation is finished, the main heating power supply automatically stops, and the instrument is in an initial state. When closed, the main relay is turned off. And when the temperature is reduced to be below 100 ℃, closing the Lock cut-off panel to control the power supply. Turning the knob to close the gas cylinder main valve clockwise, turning the knob to close the gas cylinder outlet pressure reducing valve anticlockwise, turning the gas inlet valve of the tube-closing furnace clockwise, closing the gas outlet valve of the tube-closing furnace and closing the main power supply of the tube-closing furnace. And opening the end cover of the tubular furnace, taking out the two heat-insulating furnace plugs 7, and taking out the sample storage plate.
After the above heat treatment process, Ni-Ni having a structure completely in the form of uniform sheet as shown in FIG. 9 was obtained3The Si eutectic authigenic composite material has excellent high-temperature creep resistance, fracture resistance and better room-temperature plasticity.
Low-cost preparation of Ni-Ni3The method for preparing the Si eutectic in-situ composite material saves the using amount of rare metal Ni and reduces the preparation cost of the material by designing alloy components, adopts Bridgman directional solidification technology to prepare the Ni-Si hypereutectic in-situ composite material, obtains the Ni-Ni capable of meeting the service requirement and having full lamellar structure by proper heat treatment process3A Si autogenous composite.
The above is only one material embodiment of the present invention, not all or only one embodiment, and any equivalent changes to the present invention by those skilled in the art from reading the present specification are covered by the claims of the present invention.
Claims (9)
1. Low-cost preparation of Ni-Ni3A method of Si eutectic authigenic composite materials, comprising:
step 1, selecting Ni-Si hypereutectic component proportion to take Ni and Si according to a Ni-Si binary equilibrium phase diagram so as to reduce the proportion of Ni in the alloy and further reduce the cost;
step 2, preparing a Ni-Si hypereutectic alloy ingot from the Ni and the Si through vacuum induction melting;
step 3, carrying out Bridgman directional solidification on the Ni-Si hypereutectic alloy cast ingot, and carrying out hypereutectic reaction in the liquid-solid phase change process to obtain the Ni-Si hypereutectic in-situ composite material, wherein the structure of the Ni-Si hypereutectic in-situ composite material is composed of an alpha-Ni matrix phase and Ni-Ni3Si eutectic phase, Ni31Si12Metastable phase composition, in which the alpha-Ni matrix phase is a non-facet phase, Ni31Si12Metastable phase and Ni-Ni3The eutectic phase of Si is a facet phase, Ni3The Si phase is Ni-Ni3The reinforcing phase in Si grows in lath shape along the direction of heat flow, while Ni31Si12The metastable phase mainly grows in an irregular polygon shape;
step 4, heat treatment is carried out on the Ni-Si hypereutectic in-situ composite material to lead Ni31Si12Metastable phase elimination to obtain Ni-Ni3Full lamellar eutectic structure of Si, i.e. Ni-Ni3The Si eutectic authigenic composite material.
2. The low-cost production of Ni-Ni according to claim 13The method for producing the Si eutectic authigenic composite material is characterized in that the step 1 takes bulk Si with the purity of 99.999% and Ni particles with the purity of 99.99% as raw materials.
3. The low-cost production of Ni-Ni according to claim 13The method for preparing the Si eutectic crystal authigenic composite material is characterized in that in the Ni and the Si used in the step 1, the content of the Ni is less than or equal to 88 percent, and the content of the Si is more than or equal to 12 percent.
4. The low-cost production of Ni-Ni according to claim 13The method for preparing the Si eutectic authigenic composite material is characterized in that in the step 2, Ni and Si are smelted in a vacuum induction smelting furnace with high-purity Ar atmosphere at the temperature of 1143 ℃ to prepare a Ni-Si hypereutectic alloy ingot.
5. The low-cost production of Ni-Ni according to claim 13The method for preparing the Si eutectic in-situ composite material is characterized in that in the step 3, Bridgman directional solidification is carried out under a high-temperature gradient, the temperature gradient is 150-200K/cm, the directional solidification rate is adjustable within the range of 0.1-900 mu m/s, and the vacuum degree is 4.0 multiplied by 10-2Pa, and the precision of lifting data is +/-2 mu m/m.
6. The low-cost production of Ni-Ni according to claim 53The method for preparing the Si eutectic authigenic composite material is characterized in that the solidification rate is 6-40 mu m/s during Bridgman directional solidification, and metastable phase Ni in the material structure increases along with the solidification rate31Si12The content of (c) increases.
7. The low-cost production of Ni-Ni according to claim 13The method for preparing the Si eutectic crystal authigenic composite material is characterized in that in the step 4, heat treatment is carried out in a high-temperature vacuum tube furnace.
8. Low-cost Ni-Ni production according to claim 1 or 73The method for preparing the Si eutectic crystal authigenic composite material is characterized in that the temperature range of the heat treatment is 950-1050 ℃, the heat preservation is carried out, and then the temperature is cooled to the room temperature along with a furnace.
9. The low-cost production of Ni-Ni according to claim 13The method for preparing the Si eutectic in-situ composite material is characterized in that in the step 3, the Rockwell hardness of the Ni-Si hypereutectic in-situ composite material is 58.53-64.33 HRC, the Vickers hardness is 678.86-825.46 HV, and the metastable phase Ni of the Ni-Si hypereutectic in-situ composite material obtained by selecting the Bridgman directional solidification rate of 40 mu m/s is eliminated through heat treatment31Si12Then, corresponding Ni-Ni3The Rockwell hardness of the Si eutectic authigenic composite material is 46.5HRC, and the Vickers hardness is 428 HV.
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