CN115247238B - Al-Ti intermetallic compound porous material based on synergistic pore-forming mechanism and preparation method thereof - Google Patents
Al-Ti intermetallic compound porous material based on synergistic pore-forming mechanism and preparation method thereof Download PDFInfo
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- CN115247238B CN115247238B CN202111507625.3A CN202111507625A CN115247238B CN 115247238 B CN115247238 B CN 115247238B CN 202111507625 A CN202111507625 A CN 202111507625A CN 115247238 B CN115247238 B CN 115247238B
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C21/00—Alloys based on aluminium
- C22C21/003—Alloys based on aluminium containing at least 2.6% of one or more of the elements: tin, lead, antimony, bismuth, cadmium, and titanium
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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
- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/10—Sintering only
- B22F3/1003—Use of special medium during sintering, e.g. sintering aid
- B22F3/1007—Atmosphere
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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
- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/10—Sintering only
- B22F3/11—Making porous workpieces or articles
- B22F3/1121—Making porous workpieces or articles by using decomposable, meltable or sublimatable fillers
- B22F3/1134—Inorganic fillers
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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
- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/12—Both compacting and sintering
- B22F3/14—Both compacting and sintering simultaneously
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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
- B22F9/00—Making metallic powder or suspensions thereof
- B22F9/02—Making metallic powder or suspensions thereof using physical processes
- B22F9/04—Making metallic powder or suspensions thereof using physical processes starting from solid material, e.g. by crushing, grinding or milling
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C14/00—Alloys based on titanium
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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
- B22F9/00—Making metallic powder or suspensions thereof
- B22F9/02—Making metallic powder or suspensions thereof using physical processes
- B22F9/04—Making metallic powder or suspensions thereof using physical processes starting from solid material, e.g. by crushing, grinding or milling
- B22F2009/043—Making metallic powder or suspensions thereof using physical processes starting from solid material, e.g. by crushing, grinding or milling by ball milling
Abstract
The invention provides an Al-Ti intermetallic compound porous material based on a cooperative pore-forming mechanism and a preparation method thereof, zinc powder is used as a pore-forming agent, the characteristics of easy evaporation of the zinc metal and obvious difference of diffusion coefficients between Al and Ti atoms are utilized for cooperative pore-forming, the porosity of the porous material is greatly improved, and meanwhile, the bonding strength between powders is improved by adopting low-temperature hot-pressing sintering before evaporation, so that the volume expansion in the pore-forming process is reduced; the porous material prepared by the invention mainly comprises Kirkendall pores formed by the difference of diffusion coefficients among macropores, al and Ti atoms left after metal zinc is evaporated, and the two mechanisms cooperate with a network communication structure formed by pore formation, so that the total open porosity is improved, the heat dissipation is facilitated, and the volume expansion can be effectively reduced; the Al-Ti intermetallic compound porous material prepared by the invention has uniform pore structure, and no flaking and crack generation on the surface; the process has the advantages of low sintering temperature, simple flow, environmental protection, realization of industrial production and suitability for popularization.
Description
Technical Field
The invention relates to the technical field of preparation of intermetallic compound porous materials, in particular to an Al-Ti intermetallic compound porous material based on a synergistic pore-forming mechanism and a preparation method thereof.
Background
The Al-Ti intermetallic compound has high room temperature, high temperature specific strength and excellent high temperature oxidation resistance, vulcanization resistance, molten salt resistance and anti-carbonization performance, the highest corrosion resistance temperature can reach 1200 ℃, and in addition, the Al-Ti intermetallic compound has excellent catalytic thermalization resistance, wear resistance and better processability, and meets the requirements of the modern industry on high Wen Lvcai. The porous Al-Ti-based intermetallic compound is used as a filtering and throttling material, can well meet the performance requirements of medium-high temperature environment filtering and separating materials, and is suitable for working in a severe environment.
At present, naCl is generally used as a pore-forming agent to prepare an Al-Ti porous material, and the pore is formed by dissolution and replication of NaCl. The method has the following technical problems: (1) The dissolution of NaCl is not thoroughly left in the sintering body, so that holes are easy to be blocked, the porosity and the shape of the holes are influenced, and the framework and the crucible of a sintered blank are corroded in the sintering process; (2) The surface scraps of the sample prepared by the method are seriously peeled, the sample is difficult to maintain in a good shape, the strength is low, and the volume expansion is obvious.
Disclosure of Invention
In order to solve the problems, the invention adopts high saturated vapor pressure metallic element zinc as a pore-forming agent, and utilizes the higher diffusion capacity of aluminum to promote the in-situ reaction between the aluminum and titanium element to generate an Al-Ti intermetallic compound, so as to form Kirkendall pores; meanwhile, in an Al-Ti-Zn ternary system, zn is easier to evaporate and remove compared with Al and Ti, evaporation and removal holes are formed, and the porosity of the porous material can be obviously improved. In addition, the low-temperature hot-pressing sintering before evaporation improves the bonding strength among the powders, and effectively reduces the volume expansion rate of the porous material.
The invention aims to provide a method for efficiently preparing an Al-Ti porous material, and the prepared porous material has the characteristics of high porosity, small volume expansion and uniform pore structure.
In order to achieve the technical purpose, the invention discloses the following technical scheme:
a preparation method of an Al-Ti intermetallic compound porous material based on a cooperative pore-forming mechanism comprises the following steps:
s1: placing aluminum powder and titanium powder into a ball mill for ball milling, adding the ball-milled mixed material and zinc powder into a mortar for uniform grinding, and placing the ground metal mixed material into a drying oven for drying for later use;
s2: taking a die, wherein the die is divided into an upper die and a lower die, wrapping graphite paper on the top of the lower die, placing an aluminum ring on the graphite paper of the lower die, enclosing the aluminum ring into equal-height thin-wall aluminum materials, fully filling the dried metal mixed material obtained in the step S1 into the aluminum ring, sealing the upper part of the aluminum ring by using the graphite paper, vertically placing the upper die above the aluminum ring, placing the die and the aluminum ring filled with the metal mixed material together in a hearth of a hot-pressing furnace, controlling a stable heating rate to enable the temperature of the hearth to reach sintering temperature, keeping the temperature, applying stable pressure to the die in the heating and heat-preserving processes, performing low-temperature hot-pressing sintering, and removing the graphite paper after cooling to obtain a sintered body;
s3: and (3) placing the sintered body obtained in the step (S2) in a magnetic boat, placing in a furnace tube of a vacuum tube furnace, controlling the stable vacuum degree in the whole process, heating to a preset temperature at a stable heating rate, preserving heat, and cooling with the furnace to obtain the porous material.
Further, the mol ratio of the aluminum powder to the titanium powder in the S1 is 1-3:1, and the volume of the zinc powder accounts for 10% -40% of the mixed material.
Further, the ball mass ratio in the ball milling process in the step S1 is 3-6:1, the ball milling time is 2-6 h, and the ball milling rotating speed is 300-450 r/min.
Further, the sintering temperature in S2 is 550 ℃, the heating rate is 8 ℃/min, the heat preservation time is 0.5h, and the pressure is kept at 5-15 Mpa in the low-temperature hot-pressing sintering process.
Further, the vacuum degree in S3 is not higher than 1Pa.
Further, the preset temperature in S3 is 550-800 ℃, the heating rate is 5 ℃/min, and the heat preservation time is 0.5-10 h.
The invention also provides the Al-Ti intermetallic compound porous material prepared by the method, wherein the framework of the Al-Ti intermetallic compound porous material is provided with continuously distributed Kirkendall pores and macropores among frameworks formed by zinc powder evaporation, and the Kirkendall pores and macropores among frameworks are staggered to form mutually communicated pore channels.
Compared with the prior art, the invention has the beneficial effects that:
(1) The porous material is prepared by using zinc powder as a pore-forming agent, and the bonding strength between the powders is improved by adopting low-temperature hot-pressing sintering before evaporation, so that the prepared porous material has the characteristics of high porosity, small volume expansion and high strength, avoids the residual hazard of the traditional water-soluble pore-forming agent, and is a green and environment-friendly preparation process.
(2) When the diffusion coefficients between two atoms have obvious difference, one side of a diffusion pair can carry out static substance delivery to the other side, so that a small number of Kirkendall pores are formed in the original position of one diffusion side. Its presence not only increases the overall open porosity of the sintered compact but also promotes the interconnection of macropores, and the interconnected pore structure helps to enhance the application of the porous material in filtration and sound absorption.
(3) The pore-forming agent is easy to remove, the sintering temperature is low, and the process flow is simple; in addition, the evaporated metal zinc can be recycled, so that the method is green and environment-friendly and saves resources.
Drawings
FIG. 1 shows XRD patterns of Al-Ti porous materials prepared in example 1 and comparative example.
FIG. 2 is a graph (100 x) of the fracture microstructure of the Al-Ti porous material prepared in example 1.
FIG. 3 is a graph (500 x) of the fracture microstructure of the Al-Ti porous material prepared in example 1.
FIG. 4 is a graph (2.00 kx) of the fracture microstructure of the Al-Ti porous material prepared in example 1.
Detailed Description
In order that the manner in which the above-recited features and advantages of the present invention are obtained, a more particular description of the invention will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings, in which, as a result, all embodiments of the invention are illustrated in the appended drawings.
All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The Al-Ti intermetallic compound porous material based on the cooperative pore-forming mechanism and the preparation method thereof are further described below with reference to the accompanying drawings and specific embodiments.
Example 1
A preparation method of an Al-Ti intermetallic compound porous material based on a cooperative pore-forming mechanism comprises the following steps: taking 12.6g of aluminum powder and 7.4g of titanium powder, and ball-milling in a ball mill (the molar ratio of aluminum to titanium is 3:1), wherein the ball mass ratio is 6:1 in the ball-milling process, the ball-milling time is 6h, and the ball-milling rotating speed is 450r/min. 10.59g of zinc powder (20 vol.%) was ground with 20g of aluminium titanium powder in a mortar for 10min and dried. Filling 2.5g of the mixed powder intoThe two sides of the aluminum ring are sealed by circular graphite paper. The sample is placed in the middle of a hearth of a hot pressing furnace, the sample is extruded up and down by a die in the process, the temperature is raised from room temperature to 550 ℃ at a heating rate of 8 ℃/min, the temperature is kept for 30min, and the whole process keeps the pressure of 10MPa. Taking out the sample, removing graphite paper on the surface of the sintered body, and evaporating zinc powder in a vacuum tube furnace. The evaporation temperature is set to 650 ℃, the heating rate is set to 5 ℃/min, the evaporation time is set to 6h, the vacuum degree is kept at 1Pa, the Al-Ti porous material is obtained by cooling along with a furnace, and sampling measurement XRD and SEM are carried out. XRD results are shown in FIG. 1, and microstructures are shown in FIG. 2, FIG. 3 and FIG. 4.
Examples 2 to 4
The difference from example 1 is that the amount of zinc powder used was varied, and the other conditions were the same, and the data of the Al-Ti porous materials are shown in Table 1.
TABLE 1 Effect of Zinc powder amount on Al-Ti porous materials
As can be seen from Table 1, the porosity of the porous material increases significantly with the amount of zinc powder used as the pore-forming agent, and the increase in porosity allows more channels to dissipate heat, and the volume expansion rate decreases with the increase in pore-forming agent.
Examples 5 to 7
The difference from example 1 is that the pressure during hot pressing was different, and the other conditions were the same, and the data of the al—ti porous material are shown in table 2.
TABLE 2 influence of hot pressing pressure on Al-Ti porous materials
| Examples | 1 | 5 | 6 | 7 |
| Al-Ti (molar ratio) | 3:1 | 3:1 | 3:1 | 3:1 |
| Zinc powder amount (volume ratio) | 20％ | 20％ | 20％ | 20％ |
| Ball mass ratio | 6:1 | 6:1 | 6:1 | 6:1 |
| Ball milling time (h) | 6 | 6 | 6 | 6 |
| Ball milling rotating speed (r/min) | 450 | 450 | 450 | 450 |
| Sintering process pressure (MPa) | 10 | 5 | 8 | 15 |
| Sintering temperature (. Degree. C.) | 550 | 550 | 550 | 550 |
| Evaporating temperature (. Degree. C.) | 650 | 650 | 650 | 650 |
| Thermal insulation time of evaporation process (h) | 6 | 6 | 6 | 6 |
| Vacuum degree during evaporation (Pa) | 1 | 1 | 1 | 1 |
| Open porosity (%) | 66.9 | 62.5 | 63.8 | 23.1 |
| Volume expansion ratio (%) | 16.4 | 21.2 | 19.5 | 10.1 |
The hot pressing process is mainly used for improving the bonding strength among the powders, the hot pressing pressure is too high, the bonding property among the powders is good, but the zinc powder is difficult to evaporate; the hot pressing pressure is too low, the bonding property between powders is poor, although zinc powder is easy to evaporate, the strength is not guaranteed, the result is verified in table 2, when the hot pressing pressure is 15MPa (example 7), zinc powder is difficult to evaporate, the porosity is obviously lower than other examples, but the expansion rate is lower; when the hot pressing pressure was 5MPa (example 5), zinc powder was easily evaporated, but the sample surface was slightly peeled off and easily expanded (volume expansion ratio was 21.2%).
Examples 8 to 10
The difference from example 1 is that the evaporation process was carried out for a different period of time, and the remaining conditions were the same, and the data of the Al-Ti porous materials are shown in Table 3.
TABLE 3 influence of incubation time on Al-Ti porous materials
| Examples | 1 | 8 | 9 | 10 |
| Al-Ti (molar ratio) | 3:1 | 3:1 | 3:1 | 3:1 |
| Zinc powder amount (volume ratio) | 20％ | 20％ | 20％ | 20％ |
| Ball mass ratio | 6:1 | 6:1 | 6:1 | 6:1 |
| Ball milling time (h) | 6 | 6 | 6 | 6 |
| Ball milling rotating speed (r/min) | 450 | 450 | 450 | 450 |
| Sintering process pressure (MPa) | 10 | 10 | 10 | 10 |
| Sintering temperature (. Degree. C.) | 550 | 550 | 550 | 550 |
| Evaporating temperature (. Degree. C.) | 650 | 650 | 650 | 650 |
| Thermal insulation time of evaporation process (h) | 6 | 0.5 | 2 | 10 |
| Vacuum degree during evaporation (Pa) | 1 | 1 | 1 | 1 |
| Open porosity (%) | 66.9 | 58.5 | 64.7 | 67.1 |
| Volume expansion ratio (%) | 16.4 | 22.8 | 18.2 | 15.2 |
As can be seen from the analysis in table 3, the porosity increases continuously with the extension of the holding time, but the trend of the increase is not obvious, and the saturated vapor pressure of the metallic zinc is higher, so that the metallic zinc can be rapidly evaporated in a short time, and the influence of the holding time on the porosity is smaller; and the volume expansion rate also tends to decrease with the increase of the porosity.
Examples 11 to 13
The difference from example 1 is that the evaporation temperature was different, and the remaining conditions were the same, and the data of the al—ti porous material are shown in table 4.
TABLE 4 influence of evaporation temperature on Al-Ti porous materials
As shown in table 4, the open porosity is maximum and the volume expansion rate is minimum at the evaporation temperature of 650 ℃, and the experimental result shows that the evaporation temperature is lower, the zinc powder is difficult to evaporate and the open porosity is only 36.6% when the heat preservation time is 550 ℃; when the evaporation temperature is higher than the melting point of aluminum, the metal aluminum melts to fill the formed pores in a small amount, resulting in a decrease in porosity and an increase in volume expansion.
Examples 14 to 16
The difference from example 1 is that the evaporation process was different in vacuum degree, and the rest conditions were the same, and the data of the al—ti porous material are shown in table 5.
TABLE 5 influence of evaporation vacuum on Al-Ti porous materials
As can be seen from table 5, the open porosity increases with increasing evaporation vacuum, and when the vacuum is low, oxidation of the metal powder occurs easily, and the presence of ZnO is also detected in the XRD result, and the presence of ZnO reduces the amount of pore-forming agent, so that the porosity decreases and the volume expansion increases.
Examples 17 to 19
The difference from example 1 is that the molar ratio of the raw material aluminum powder and titanium powder was different, and the other conditions were the same, and the data of the al—ti porous material are shown in table 6.
TABLE 6 influence of the molar ratio of aluminum powder and titanium powder as raw materials on Al-Ti porous materials
| Examples | 1 | 17 | 18 | 19 |
| Al-Ti (molar ratio) | 3:1 | 1:1 | 1.5:1 | 2:1 |
| Zinc powder amount (volume ratio) | 20％ | 20％ | 20％ | 20％ |
| Ball mass ratio | 6:1 | 6:1 | 6:1 | 6:1 |
| Ball milling time (h) | 6 | 6 | 6 | 6 |
| Ball milling rotating speed (r/min) | 450 | 450 | 450 | 450 |
| Sintering process pressure (MPa) | 10 | 10 | 10 | 10 |
| Sintering temperature (. Degree. C.) | 550 | 550 | 550 | 550 |
| Evaporating temperature (. Degree. C.) | 650 | 650 | 650 | 650 |
| Thermal insulation time of evaporation process (h) | 6 | 6 | 6 | 6 |
| Vacuum degree during evaporation (Pa) | 1 | 1 | 1 | 1 |
| Open porosity (%) | 66.9 | 64.2 | 65.8 | 66.3 |
| Volume expansion ratio (%) | 16.4 | 18.7 | 17.9 | 17.1 |
As can be seen from table 6, the open porosity increases with increasing aluminum content, and the volume expansion rate is exactly opposite to the open porosity. When the Al content is low, the porosity of the Al-Ti alloy porous material is low, and enough pore volume is not communicated; as the aluminum content increases, the porosity increases, and the pores are easily communicated on the originally interconnected particle-bound network, so that more channels are available for energy dissipation and the volume expansion is continuously reduced.
Examples 20 to 22
The difference from example 1 is that the ball milling conditions were different, and the rest conditions were the same, and the data of the al—ti porous material are shown in table 7.
TABLE 7 influence of ball milling conditions on Al-Ti porous materials
| Examples | 1 | 20 | 21 | 22 |
| Al-Ti (molar ratio) | 3:1 | 3:1 | 3:1 | 3:1 |
| Zinc powder amount (volume ratio) | 20％ | 20％ | 20％ | 20％ |
| Ball mass ratio | 6:1 | 6:1 | 3:1 | 6:1 |
| Ball milling time (h) | 6 | 2 | 6 | 6 |
| Ball milling rotating speed (r/min) | 450 | 450 | 450 | 300 |
| Sintering process pressure (MPa) | 10 | 10 | 10 | 10 |
| Sintering temperature (. Degree. C.) | 550 | 550 | 550 | 550 |
| Evaporating temperature (. Degree. C.) | 650 | 650 | 650 | 650 |
| Thermal insulation time of evaporation process (h) | 6 | 6 | 6 | 6 |
| Vacuum degree during evaporation (Pa) | 1 | 1 | 1 | 1 |
| Open porosity (%) | 66.9 | 66.6 | 66.3 | 65.8 |
| Volume expansion ratio (%) | 16.4 | 20.2 | 22.4 | 25.5 |
As can be seen from Table 7, the impact of the ball milling conditions on the open porosity and the volume expansion rate is smaller, and the open porosity is slightly increased and the volume expansion rate is slightly reduced along with the increase of the ball mass ratio, the extension of the ball milling time and the increase of the ball milling rotating speed.
Comparative example
12.6g of aluminum powder and 7.4g of titanium powder are taken, ball milling is carried out in a ball mill (molar ratio of aluminum to titanium is 3:1), 3.21g of NaCl crystal (20 vol%) is taken, and is ground with 20g of aluminum-titanium powder in a mortar for 10min, dried, and then a few drops of ethanol are dripped into the mixture. After being uniformly mixed, ti-3 Al/NaCl powder is placed in a mould to be cold-pressed into a cylindrical and shaped blank body, and the cylindrical and shaped blank body is placed in deionized water at 70 ℃ to be dissolved for 3-4 hours. Then sintering at 650 deg.C and 10 deg.C in vacuum tube furnace -3 Pa, heating rate is 5 ℃/min, heat preservation time is 6h, and then furnace cooling is carried out to obtain the Al-Ti porous material. The porous material obtained had an open cell rate of 35.8% and a volume expansion rate of 73.3%, and XRD results are shown in FIG. 1.
According to XRD result analysis, al-Ti intermetallic compound is indeed generated in the sintering process, naCl diffraction peak exists in XRD result of comparative example, but the technical scheme of the invention only can observe existence of Al-Ti intermetallic compound and Ti diffraction peak, and by combining data analysis, residual split porosity of pore-forming agent produces obvious influence, under the same experimental condition, the maximum open porosity of the technical scheme of the invention can reach 66.9%, the volume expansion rate of the technical scheme of the invention is only 35.8%, the volume expansion rate of the technical scheme of the invention is about 20%, the volume expansion rate of the comparative example is as high as 73.3%, and the high volume expansion rate can hardly keep good shape and strength, so that the technical scheme of the invention has obvious advantages.
Fig. 2 shows the macro fracture morphology of the prepared porous material, and pores uniformly distributed on a substrate can be obviously observed, and as the density of zinc powder raw materials is greatly different from that of aluminum and titanium metal powder, the aluminum and titanium mixed materials are uniformly ball-milled and then mixed with the zinc powder in a grinding mode, so that the zinc powder is more uniformly distributed in the mixed materials, and the pores obtained by evaporation are also more uniform.
As can be seen from FIG. 3, the fracture pores of the sample are obvious, the pore diameters of the individual pores are distributed between 20 and 100 mu m, the pores are connected by particle frameworks, the whole system mainly comprises an Al-Ti intermetallic compound framework, macropores among the frameworks (average size is 45.86 mu m) and Kirkendall pores on the frameworks (average size is 25.51 mu m), and the hierarchical pore structure can be widely applied to the fields of liquid-gas separation, filtration and the like. Before the furnace temperature reaches the melting point of aluminum, namely between 550 and 650 ℃, the inside of the sintered body can undergo diffusion reaction, and as the diffusion rate of aluminum element is obviously higher than that of titanium element, aluminum particles can undergo solid phase reaction with titanium to generate Al-Ti intermetallic compounds, so that a certain amount of vacancies remain in the original aluminum positions, and Kirkendall pores are formed on the framework. Due to the deformability of the Al particles, the continuous distribution of Al on the periphery of the Ti particles can be realized, and Kirkendall pores formed on the basis of the continuously distributed Al particles provide structural conditions for further realizing the integral communication in the blank. When the evaporation temperature is sufficient to cause the zinc powder to evaporate, the zinc powder continuously evaporates leaving macropores between the frameworks. The connectivity between the large pores marked with white double-headed arrows and the small pores marked with white double-headed arrows is more obvious, and the large pores and the small pores are staggered to form mutually communicated pore channels, as shown by white curves in fig. 3. As shown in FIG. 4, the size of the particles and the pore structure of the product can be further obviously observed to be more 2000 times, the particles of the product are mainly in square or near square shapes, as shown in the white rectangle in FIG. 4, the particles are combined with each other through metallurgy to form a porous skeleton structure, no phenomena such as slag falling, pulverization and the like occur, the sintering quality is better, the white circle part in FIG. 4 is in a pit shape, small pores are distributed at the bottom of the pit, as shown in the black circle in FIG. 4, the pits represent large pores left by the evaporation of zinc powder, and the small pores are distributed at the bottom of the large pores to realize the communication among the pores.
Because Kirkendall pores belong to a microscopic pore-forming mechanism, pores formed by evaporation of a pore-forming agent belong to macroscopic physical pore-forming, the microscopic pores and the macroscopic pores are combined to enable the pores to be staggered and communicated with each other, the communicated pore structure not only improves the total open porosity, but also is beneficial to the transportation of substances and the transfer of energy, the volume expansion can be effectively reduced, the shape of a good sintered body is maintained, and the surface of a sample is free from flaking and cracks.
The above description is only of the preferred embodiments of the present invention and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modifications or equivalent substitutions made within the spirit and principles of the present invention should be included in the scope of the present invention.
Claims (2)
1. The preparation method of the Al-Ti intermetallic compound porous material based on the cooperative pore-forming mechanism is characterized by comprising the following steps of:
s1: placing aluminum powder and titanium powder into a ball mill for ball milling, adding the ball-milled mixed material and zinc powder into a mortar for uniform grinding, and placing the ground metal mixed material into a drying oven for drying for later use;
s2: taking a die, wherein the die is divided into an upper die and a lower die, wrapping graphite paper on the top of the lower die, placing an aluminum ring on the graphite paper of the lower die, enclosing the aluminum ring into equal-height thin-wall aluminum materials, fully filling the dried metal mixed material obtained in the step S1 into the aluminum ring, sealing the upper part of the aluminum ring by using the graphite paper, vertically placing the upper die above the aluminum ring, placing the die and the aluminum ring filled with the metal mixed material together in a hearth of a hot-pressing furnace, controlling a stable heating rate to enable the temperature of the hearth to reach sintering temperature, keeping the temperature, applying stable pressure to the die in the heating and heat-preserving processes, performing low-temperature hot-pressing sintering, and removing the graphite paper after cooling to obtain a sintered body;
s3: placing the sintered body obtained in the step S2 in a magnetic boat, placing in a furnace tube of a vacuum tube furnace, controlling the stable vacuum degree in the whole process, heating to a preset temperature at a stable heating rate, preserving heat, and cooling along with the furnace to obtain a porous material;
the mol ratio of the aluminum powder to the titanium powder in the S1 is 1-3:1, and the volume of the zinc powder accounts for 10% -40% of the mixed material;
in the S1, the ball mass ratio in the ball milling process is 3-6:1, the ball milling time is 2-6 h, and the ball milling rotating speed is 300-450 r/min;
s2, the sintering temperature is 550 ℃, the heating rate is 8 ℃/min, the heat preservation time is 0.5h, and the pressure is kept between 5 and 15MPa in the low-temperature hot-pressing sintering process;
s3, the vacuum degree is not higher than 1Pa;
and S3, the preset temperature is 550-800 ℃, the heating rate is 5 ℃/min, and the heat preservation time is 0.5-10 h.
2. The Al-Ti intermetallic compound porous material prepared by the preparation method of the Al-Ti intermetallic compound porous material based on the cooperative pore-forming mechanism, which is characterized in that the framework of the Al-Ti intermetallic compound porous material is provided with continuously distributed Kirkendall pores and macropores among frameworks formed by zinc powder evaporation, and the Kirkendall pores and macropores among frameworks are staggered to form mutually communicated pore channels.
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| CN202111507625.3A CN115247238B (en) | 2021-12-10 | 2021-12-10 | Al-Ti intermetallic compound porous material based on synergistic pore-forming mechanism and preparation method thereof |
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| CN202111507625.3A CN115247238B (en) | 2021-12-10 | 2021-12-10 | Al-Ti intermetallic compound porous material based on synergistic pore-forming mechanism and preparation method thereof |
Publications (2)
| Publication Number | Publication Date |
|---|---|
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