CN112853139B - Preparation method of iron-aluminum intermetallic compound porous material - Google Patents

Preparation method of iron-aluminum intermetallic compound porous material Download PDF

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CN112853139B
CN112853139B CN202110063393.0A CN202110063393A CN112853139B CN 112853139 B CN112853139 B CN 112853139B CN 202110063393 A CN202110063393 A CN 202110063393A CN 112853139 B CN112853139 B CN 112853139B
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aluminum
magnesium
powder
iron
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CN112853139A (en
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徐志刚
黄庚强
王传彬
沈强
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Wuhan University of Technology WUT
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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
    • C22C1/047—Making non-ferrous alloys by powder metallurgy comprising intermetallic compounds
    • 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
    • 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
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C33/00—Making ferrous alloys
    • C22C33/02—Making ferrous alloys by powder metallurgy
    • C22C33/0257—Making ferrous alloys by powder metallurgy characterised by the range of the alloying elements
    • C22C33/0278—Making ferrous alloys by powder metallurgy characterised by the range of the alloying elements with at least one alloying element having a minimum content above 5%
    • 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
    • B22F2999/00—Aspects linked to processes or compositions used in powder metallurgy

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Abstract

The invention provides a preparation method of an iron-aluminum intermetallic compound porous material, which is prepared by powder sintering and an in-situ multiple dealloying effect caused by the powder sintering. The method takes iron powder, aluminum-magnesium alloy powder and magnesium powder as raw materials, and prepares the green compact in a high-vacuum environment by carrying out multi-stage heating and heat preservation and synergistically utilizing the following two methods: 1) reacting a low-temperature instantaneous liquid phase formed by the aluminum-magnesium alloy powder in the sintering process with the element iron powder to realize the low-temperature formation of the iron-aluminum intermetallic compound and generate an in-situ liquid phase dealloying pore-forming effect; 2) gas-phase dealloying pore-forming triggered by magnesium component sublimation or volatilization. The dealloying effect generated by the instantaneous liquid phase formed by the aluminum-magnesium alloy powder at low temperature and iron accelerates the formation of the iron-aluminum intermetallic compound, shortens the sintering period, and can avoid the pollution of the traditional pore-forming agent to the components of the iron-aluminum intermetallic compound. The aperture of the prepared porous material is 10-100 mu m, and the porosity and the total porosity can respectively reach more than 50% and 60%.

Description

Preparation method of iron-aluminum intermetallic compound porous material
Technical Field
The invention belongs to the technical field of alloy material preparation, and particularly relates to a preparation method of an iron-aluminum intermetallic compound porous material.
Background
The iron-aluminum intermetallic compound is a special binary compound with a long-range ordered structure, which is formed by iron element and aluminum element with the atomic percentage of 22.5-76.5%. The Fe-Al based intermetallic compounds are mainly classified into Fe according to their crystal structures3Al、Fe2Al5、FeAl、FeAl2And FeAl3And the like. The special structure of the iron-aluminum intermetallic compound can overcome a series of defects brought by the traditional metal and ceramic in the application process. Compared with the traditional metal material, the iron-aluminum intermetallic compound has more excellent high-temperature mechanical strength, high-temperature oxidation resistance and acid-base corrosion resistance. Compared with the traditional inorganic ceramic material, the iron-aluminum intermetallic compound has the advantages of good thermal shock resistance, excellent welding performance and the like. In addition, the abundance of iron and aluminum elements on the earth is high, and the price is low. At present, with the rapid development of national economy, steel, metallurgy,In the production process of important industries related to national economic development, such as coal electricity, thermoelectricity, petrochemical industry, cement, pharmaceutical chemical industry, industrial glass and the like, a large amount of high-temperature dust-containing smoke and waste gas which damage the living environment and health of people can be generated. The porous iron-aluminum intermetallic compound material with the open pore structure for high-temperature filtration and separation is prepared by utilizing the excellent comprehensive properties of the iron-aluminum intermetallic compound, is an important method for solving the problem of high-temperature waste gas treatment, and has great economic value and social benefit for energy conservation, emission reduction and clean production.
The preparation method of the iron-aluminum intermetallic compound porous material mainly comprises reaction sintering pore-forming and pore-forming agent sintering pore-forming. The reaction sintering pore-forming is mainly characterized in that the reaction sintering pore-forming is realized by utilizing the Kenkdael effect generated by the difference of diffusion coefficients between iron element and aluminum element. The pore-forming method is the most important method for preparing the iron-aluminum intermetallic compound at present. A large number of published reports show that the porosity is usually less than 60% when the method is used for pore forming, and the iron-aluminum intermetallic compound porous material with higher porosity is difficult to obtain. Another problem with this method is that the temperature at which the iron and aluminum elements begin to react is relatively high, mostly above 550 ℃. The reaction between iron and aluminum is a solid phase diffusion reaction at a temperature lower than the melting point of aluminum, and the reaction rate is slow, resulting in a long period of pore formation and component homogenization. Generally, the large-scale reaction pore-forming between the element iron powder and the element aluminum powder is required to be above the melting point temperature of aluminum (the liquid phase can accelerate the reaction), and the reaction pore-forming temperature is high. Sintering and pore-forming by a pore-forming agent method, wherein an inorganic or organic pore-forming agent and iron, aluminum and other element powder or iron-aluminum alloy powder are pre-mixed, and the pore-forming agent is removed from a pressed compact by water or an organic solvent before sintering to complete pore-forming; or cracking and removing the pore-forming agent in the sintering process to realize pore-forming. The method has the problems that on one hand, the proportion of the pore-forming agent cannot be too much, and the excessive pore-forming agent can cause the problems of collapse, deformation and the like of the pressed compact after the pore-forming agent is removed. That is, the porosity of the iron-aluminum intermetallic compound porous material prepared using the method is greatly affected because a sufficient pore-forming agent cannot be added. On the other hand, the pore-forming agent used in the method mainly comprises sodium chloride particles, calcium chloride particles, PMMA particles and the like, and the pore-forming agent particles may react with elements such as iron, aluminum and the like or cannot be completely removed from a pressed compact in the removal process, so that the pore-forming agent residues are caused, the iron-aluminum matrix is polluted, and the physical and mechanical properties of the sintered porous material are influenced. Therefore, how to obtain a porous material with high porosity, which has high pore-forming efficiency, short pore-forming period and no pollution to the iron-aluminum intermetallic compound in the pore-forming process is a problem to be solved urgently.
Disclosure of Invention
The invention aims to provide a preparation method of an iron-aluminum intermetallic compound porous material aiming at the defects in the prior art.
In order to solve the technical problems, the invention adopts the following technical scheme:
a preparation method of an iron-aluminum intermetallic compound porous material comprises the steps of mixing iron powder, aluminum-magnesium alloy powder and magnesium powder in vacuum or inert atmosphere to obtain uniformly mixed Fe-Al-Mg ternary mixed powder, and performing vacuum sintering after the ternary mixed powder is pressed and formed.
The invention aims to provide a novel high-efficiency method for preparing an iron-aluminum intermetallic compound porous material by utilizing in-situ multiple dealloying effect of element iron powder, aluminum-magnesium alloy powder and element magnesium powder in a sintering process. The method synergistically utilizes the following two ways to prepare the iron-aluminum intermetallic compound porous material: 1) the low-temperature instantaneous liquid phase formed by the aluminum-magnesium alloy powder in the sintering process is diffused or reacted with the element iron powder, so that the low-temperature formation of an iron-aluminum intermetallic compound is realized, and an in-situ liquid phase dealloying pore-forming effect is generated; 2) Gas-phase dealloying pore-forming caused by magnesium component sublimation or volatilization.
The principle of the invention is that in the ternary Fe-Al-Mg system, aluminum and magnesium two components and iron and aluminum two components can be mutually dissolved and respectively form aluminum-magnesium and iron-aluminum solid solution or intermetallic compound, and the iron and magnesium two components are mutually insoluble at the temperature below the melting point of magnesium. Based on the above, according to an Al-Mg binary phase diagram (figure 2), the aluminum-magnesium alloy powder can form a series of liquid phases at a lower temperature within 437-660 ℃ (melting point of aluminum). Aluminum atoms in the low temperature transient liquid phase formed by the aluminum magnesium alloy powder are soluble in iron, while magnesium atoms are insoluble in iron. Therefore, aluminum atoms in the aluminum-magnesium instantaneous liquid phase continuously diffuse to surrounding solid iron particles, namely, the aluminum atoms in the aluminum-magnesium liquid phase are continuously removed from the liquid phase, so that the aluminum-magnesium liquid phase generates an in-situ dealloying process. Along with the continuous process of dealloying, the aluminum content in the aluminum-magnesium liquid phase is continuously reduced, and the liquid phase is continuously developed to the component with high magnesium content and finally becomes a magnesium-aluminum solid phase rich in magnesium. Compared with the traditional method for forming pores by direct solid-phase reaction of binary element iron powder and element aluminum powder, the method has the advantages that a large amount of aluminum-magnesium low-temperature instantaneous liquid phase is generated, the liquid phase forming temperature is far lower than that of a Fe-Al binary system (figure 1), the diffusion speed of aluminum atoms to an iron matrix is favorably accelerated at low temperature, the generation speed of iron-aluminum intermetallic compounds and pores is obviously improved, the forming temperature of the iron-aluminum intermetallic compounds is reduced, and the sintering efficiency is improved. The preparation of the Fe-Al porous material with high porosity is completed, the energy consumption in the sintering process is saved, and the effects of energy conservation and emission reduction are remarkable. The dealloying method related by the invention is also characterized in that in the liquid phase dealloying process, as aluminum is continuously deallocated from the aluminum-magnesium instantaneous liquid phase, the aluminum-magnesium liquid phase is changed into an aluminum-magnesium solid phase with lower aluminum content due to the reduction of the aluminum content in the liquid phase, the aluminum-magnesium solid phase is changed into the instantaneous liquid phase state again along with the continuous rise of the temperature, and is repeatedly changed into the instantaneous liquid phase state for multiple times along with the rise of the temperature, in the process, the volume of the aluminum-magnesium liquid phase is continuously shrunk in the dealloying process, and pores continuously occupy partial positions occupied by the original instantaneous liquid phase until a solid aluminum-magnesium alloy/intermetallic compound is formed, so that the porosity is further increased.
In addition, the invention also relates to a gas-phase dealloying pore-forming method which is generated by magnesium sublimation or volatilization in a high vacuum environment and is used for simultaneously realizing the advantages of greatly improving the porosity and removing the magnesium component in the Fe-Al-Mg ternary powder system, thereby obtaining the pure binary iron-aluminum intermetallic compound porous material with high porosity. In the process, magnesium in the magnesium-containing liquid/solid phase is largely sublimated or volatilized, so that pores are largely generated at positions occupied by magnesium atoms, and the porosity is further improved. As the magnesium is continuously sublimed or volatilized, the residual magnesium aluminum liquid/solid phase will continuously transition to a solid phase of high aluminum content until the magnesium is completely sublimed or volatilized from the system. At this time, a large amount of pores and residual elemental aluminum, which are caused by magnesium sublimation or volatilization removal, are generated at the original position of the aluminum-magnesium solid phase. Subsequently, the residual elemental aluminum will react with the iron-aluminum intermetallic compound or solid solution, further enlarging the pore content by the kirkendall effect. And finally, further sintering at high temperature to complete component homogenization and prepare the iron-aluminum intermetallic compound porous material with high porosity.
In order to obtain iron-aluminum intermetallic compounds with different structures, in the aspect of the initial component proportion of a Fe-Al-Mg ternary mixed powder system, preferably, iron powder, aluminum-magnesium alloy powder and magnesium powder in the ternary mixed powder are mixed according to the atomic percent proportion of z (tFe-xAl) -yMg, the value of x is 22.5% -76.5%, and t = 1-x; y is 30-60%, z =1-y, and x, t, y and z are all atomic percent. Wherein (tFe-xAl) represents the chemical formula of the finally prepared iron-aluminum intermetallic compound, and t and x respectively represent the atomic percent of Fe and Al in the iron-aluminum intermetallic compound; y represents the atomic percentage of the sum of magnesium in the aluminum magnesium alloy powder and magnesium in the magnesium powder in the ternary mixed powder. Under the guiding principle of the components, the weighing amount of the element iron powder, the aluminum magnesium alloy powder and the element magnesium powder is mainly determined by the components of the aluminum magnesium alloy powder. Under the premise of determining the components of the aluminum magnesium alloy powder, the required weight of the element iron powder, the aluminum magnesium alloy powder and the element magnesium powder is prepared according to a proportioning formula z (tFe-xAl) -yMg.
Preferably, the atomic ratio of aluminum to magnesium in the aluminum-magnesium alloy powder in the ternary mixed powder is 1: 4-4: 1.
preferably, the particle size of the iron powder in the ternary mixed powder is 0.1-500 μm, the particle size of the aluminum-magnesium alloy powder is 0.1-500 μm, and the particle size of the magnesium powder is 0.1-500 μm.
Preferably, the ternary mixed powder is formed by conventional compression molding or cold isostatic pressing, and the pressure of the compression molding is more than 50 MPa.
Preferably, the vacuum degree of the vacuum sintering should be less than 0.1 Pa.
Preferably, the vacuum sintering is carried out by adopting a multi-stage heating and heat preservation process.
Preferably, the vacuum sintering comprises the steps of:
(1) heating the ternary mixed powder compact of the pressed and formed Fe-Al-Mg to an instantaneous liquid phase temperature region of the aluminum-magnesium alloy powder, and preserving heat for 2-7 hours in the instantaneous liquid phase temperature region; the temperature range of the instantaneous liquid phase temperature zone is 450-650 ℃; specifically, in the step (1), the temperature raising and holding operations at a plurality of temperature points can be performed in the transient liquid phase temperature region according to different element proportions in the Fe-Al-Mg ternary mixed powder. For example, in the preferred embodiment 1 of the present invention, the temperature raising and holding operation at two temperature points is performed in the transient liquid phase temperature region; in the preferred embodiment 2 of the present invention, the temperature raising and holding operations at three temperature points are performed in the instantaneous liquid phase temperature zone; in the preferred embodiment 3 of the present invention, the temperature raising and holding operation is performed at four temperature points in the transient liquid phase temperature region. It should be noted that several temperature points specifically set in the transient liquid phase temperature region need to be determined according to the components of the Fe-Al-Mg ternary mixed powder compact, and are not limited by the selection of the temperature points in the specific embodiment of the present invention, and a plurality of temperature points may be set according to actual conditions to perform corresponding temperature raising and heat preservation operations. For example, the transient liquid phase temperature in step (1) may be divided into the following three temperature zones, and the respective warming and holding operations may be performed at temperature points within the respective temperature zones:
(101) placing the pressed and formed Fe-Al-Mg ternary mixed powder compact into a high vacuum sintering furnace, heating to a first instantaneous liquid phase temperature region of the aluminum-magnesium alloy powder at a heating rate of 1-10 ℃/min, wherein the temperature range of the first instantaneous liquid phase temperature region is generally 450-500 ℃, the specific temperature is determined according to the temperature of the instantaneous liquid phase generated by the aluminum-magnesium alloy powder, and keeping the temperature for 1-3 hours in the first instantaneous liquid phase temperature region; the heating and heat preservation in the stage are mainly used for generating a transient liquid phase of the aluminum-magnesium alloy powder and enabling aluminum atoms in the transient liquid phase to generate a dealloying process of diffusing or reacting to surrounding iron particles. On the one hand, the dealloying action of aluminum from the instantaneous liquid phase of aluminum and magnesium can cause the instantaneous liquid phase of aluminum and magnesium to shrink, and a large number of holes are generated at the position of the original liquid phase. In addition, due to the high saturated vapor pressure of magnesium, magnesium in the Fe-Al-Mg ternary system is sublimated or volatilized, so that a gas-phase dealloying process is performed in an original magnesium-containing region, and pores are promoted to be generated in the magnesium-containing region. Meanwhile, compared with a binary Fe-Al system, the diffusion behavior of aluminum in the aluminum-magnesium instantaneous liquid phase to solid iron particles at low temperature accelerates the formation of iron-aluminum intermetallic compounds.
(102) As the aluminum in the instantaneous liquid phase of aluminum-magnesium continuously diffuses or reacts towards the surrounding iron particles, the composition of the instantaneous liquid phase also continuously changes towards high magnesium content, the instantaneous liquid phase gradually disappears and becomes a solid magnesium-rich aluminum-magnesium alloy with a melting point higher than 500 ℃. Under the condition, continuously heating to a second instantaneous liquid phase temperature area of the aluminum-magnesium alloy at the heating rate of 1-10 ℃/min, wherein the temperature range of the second instantaneous liquid phase temperature area of the aluminum-magnesium alloy is generally 500-600 ℃, and preserving heat for 1-2 hours in the second instantaneous liquid phase temperature area; and continuously changing the solid magnesium-rich aluminum-magnesium alloy into a new instantaneous liquid phase, and repeating the liquid phase dealloying process and the gas phase dealloying process to further improve the pore content in the Fe-Al-Mg system.
(103) Along with the continuous process of dealloying, the components of the aluminum magnesium alloy are continuously changed, and simultaneously, the aluminum magnesium alloy is further changed to high magnesium content and is changed into an aluminum magnesium solid phase with new components again. Under the condition, the temperature is continuously increased to a third instantaneous liquid phase temperature area of the aluminum-magnesium alloy at the temperature increasing rate of 1-10 ℃/min, the temperature range of the third instantaneous liquid phase temperature area of the aluminum-magnesium alloy is generally 600-650 ℃, the temperature is kept in the third instantaneous liquid phase temperature area for 1-2 hours, and the dealloying process of the step (102) is repeated.
(2) Continuously heating to a magnesium melting point temperature zone at a heating rate of 1-10 ℃/min, wherein the temperature range of the magnesium melting point temperature zone is 650-660 ℃ (the temperature is close to the magnesium melting point temperature), and preserving the temperature for 0.5-4 h in the magnesium melting point temperature zone; the magnesium atoms remained in the aluminum-magnesium alloy or the pure magnesium are continuously sublimated or volatilized from the Fe-Al-Mg system, and the remained aluminum-magnesium alloy is continuously converted to the high aluminum direction. When the magnesium component is completely removed from the Fe-Al-Mg, the residual aluminum-magnesium phase is converted into the simple aluminum substance, and finally the blank with the binary Fe-Al component is obtained. The process not only can continue to increase the porosity through magnesium sublimation, but also can avoid the adverse effects of residual magnesium on the mechanical and chemical properties of the iron-aluminum intermetallic compound.
(3) Continuously heating to an aluminum melting point temperature zone at a heating rate of 1-10 ℃/min, wherein the temperature of the aluminum melting point temperature zone is generally 665-685 ℃ (slightly higher than the melting point temperature of aluminum), and preserving heat for 0.5-1.5 h in the aluminum melting point temperature zone; so that the residual aluminum simple substance continues to react with the peripheral iron-based solid solution or the generated iron-aluminum intermetallic compound in the form of liquid phase.
(4) And continuously heating to 900-1100 ℃ at the heating rate of 1-10 ℃/min (the specific temperature is determined according to the components and the melting point of the iron-aluminum intermetallic compound), and preserving heat for 1-2 h at the temperature to finish the component homogenization and the residual reaction pore-forming process. Through the process, the iron-aluminum intermetallic compound porous material with high porosity and designed components is finally obtained, the pore size range of the obtained porous material is 10-100 mu m, the porosity of the pores can reach more than 50%, and the total porosity can reach more than 60%.
Compared with the prior art, the invention has the beneficial effects that:
(1) the low-melting-point aluminum-magnesium alloy powder can form an instantaneous liquid phase at a lower temperature far lower than the melting point of pure aluminum or pure magnesium, and the generation of the instantaneous liquid phase of aluminum and magnesium can obviously improve the diffusion process of aluminum atoms in the instantaneous liquid phase to surrounding solid iron particles, so that the formation of an iron-aluminum intermetallic compound is accelerated, the sintering period is favorably shortened, and the energy consumption is reduced.
(2) The method reasonably utilizes the characteristics that the iron-magnesium binary systems are mutually insoluble and the iron-aluminum binary systems are mutually soluble in a solid state, when the aluminum-magnesium binary alloy powder generates an instantaneous liquid phase at a low temperature, aluminum atoms in the instantaneous liquid phase can be quickly diffused into surrounding solid iron particles, namely the instantaneous aluminum-magnesium liquid phase generates dealloying action, the instantaneous aluminum-magnesium liquid phase is shrunk in the process, a large number of holes are generated at the position of the original aluminum-magnesium instantaneous liquid phase, and the porosity of the iron-aluminum intermetallic compound porous material is effectively improved.
(3) The invention utilizes the characteristic that magnesium has high saturated vapor pressure, and during the sintering process, magnesium atoms are continuously sublimated or volatilized in an aluminum-magnesium alloy or pure magnesium phase to generate a gas phase dealloying action, thereby obviously improving the porosity of the iron-aluminum porous material.
(4) The sublimation or volatilization effect of the magnesium atoms can completely remove magnesium from the Fe-Al-Mg ternary system in the sintering process, and finally the binary FeAl intermetallic compound porous material with high porosity and no magnesium residue is obtained.
(5) The iron, aluminum and magnesium play an important role in dealloying. The method has the advantages that the necessary inherent component iron in the iron-aluminum intermetallic compound is used as the dealloying agent to remove aluminum in the aluminum-magnesium instantaneous liquid phase, so that the method is beneficial to pore forming, meanwhile, no additional dealloying agent is needed in the in-situ removal process to remove aluminum, the dealloying process is reduced, and the problems of complex post-treatment or potential environmental pollution caused by the additional dealloying agent are avoided.
(6) The liquid phase dealloying process enables the magnesium content in the aluminum magnesium alloy phase to be continuously increased, so that the saturated vapor partial pressure of magnesium can be increased, and the sublimation pore-forming process of magnesium can be accelerated.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
It will be appreciated by those skilled in the art that the objects and advantages that can be achieved with the present invention are not limited to the specific details set forth above, and that these and other objects that can be achieved with the present invention will be more clearly understood from the detailed description that follows.
Drawings
FIG. 1 is a binary phase diagram of Fe-Al;
FIG. 2 is an Al-Mg binary phase diagram;
FIG. 3 is a microscopic morphology (macrostructure) of the FeAl intermetallic compound porous material obtained in example 1;
FIG. 4 shows the microstructure (high-magnification microstructure) of the FeAl intermetallic compound porous material obtained in example 1;
fig. 5 is a microscopic morphology (high magnification microstructure) of the FeAl intermetallic compound porous material obtained in example 1.
Detailed Description
The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention.
It is to be understood that the processing equipment or apparatus not specifically identified in the following examples is conventional in the art.
Furthermore, it is to be understood that one or more method steps mentioned in the present invention does not exclude that other method steps may also be present before or after the combined steps or that other method steps may also be inserted between these explicitly mentioned steps, unless otherwise indicated; moreover, unless otherwise indicated, the numbering of the various method steps is merely a convenient tool for identifying the various method steps, and is not intended to limit the order in which the method steps are arranged or the scope of the invention in which the invention may be practiced, and changes or modifications in the relative relationship may be made without substantially changing the technical content.
Example 1
Embodiment 1 of the present invention provides a method for preparing an iron-aluminum intermetallic compound porous material, specifically including the following steps:
(1) selecting element iron powder, element magnesium powder and aluminum: the method comprises the following steps of taking three powders of magnesium-aluminum alloy powder with the magnesium atomic percentage of 45% and 55% as raw material powders, and respectively weighing element iron powder, element magnesium powder and aluminum-magnesium alloy powder according to the atomic percentage of magnesium accounting for 60% of Fe-Al-Mg ternary mixed powder and the proportion of iron-aluminum atomic ratio of 1:1 to obtain the intermetallic compound porous material with the designed component of B2-FeAl. The particle sizes of the iron powder, the magnesium powder and the aluminum magnesium alloy powder are all 30 micrometers. And mixing the Fe-Al-Mg ternary powder in an argon atmosphere after weighing is finished. Subsequently, the mixed powder was molded by press molding at a pressing pressure of 300 MPa.
(2) And (4) putting the pressed blank into a high vacuum sintering furnace for sintering and pore-forming. Firstly, the temperature is increased to 480 ℃ at the heating rate of 5 ℃/min, and the blank is kept at the temperature for 1 h. At the stage, the aluminum-magnesium alloy powder can be changed into an instantaneous liquid phase, aluminum atoms in the liquid phase continuously diffuse/react to surrounding iron particles, a pore-forming process of liquid-phase dealloying is carried out, and a FeAl intermetallic compound framework is gradually formed. In the process, the instantaneous liquid phase of the aluminum-magnesium component is continuously converted to a component with high magnesium content due to the continuous removal of aluminum. As a result, the original transient liquid phase of the aluminum-magnesium component becomes a solid phase.
(3) And continuously heating the blank to 550 ℃ at the heating rate of 5 ℃/min, and preserving the heat for 1 h. At this stage, the magnesium-rich al-mg solid phase becomes a liquid phase again, and the liquid phase dealloying pore-forming process in step (2) of this example is repeated, during which the al-mg transient liquid phase becomes an al-mg solid phase with new components again. In addition, during this stage, a pore-forming process of gas-phase dealloying due to magnesium sublimation or volatilization also occurs.
(4) The blank is further raised to 655 ℃ at the heating rate of 10 ℃/min and is kept warm for 3 h. In the stage, the residual magnesium in the ternary Fe-Al-Mg system is continuously reduced through gas phase dealloying until the residual magnesium completely disappears, the porosity of the system is further improved, and the binary Fe-Al system without magnesium residue is obtained. During this process, a small amount of residual elemental aluminum is present due to the disappearance of magnesium.
(5) And continuously heating the blank to 680 ℃ at the heating rate of 5 ℃/min, and preserving the heat for 1 h. The residual aluminum simple substance is changed into liquid phase and reacts with the surrounding FeAl matrix, and the porosity is further expanded.
(6) And continuously heating the blank to 1100 ℃ at the heating rate of 10 ℃/min, preserving the heat for 1 h, increasing the porosity through further diffusion/reaction between iron and aluminum, and simultaneously completing homogenization of Fe-Al components, thereby finally obtaining the B2-FeAl intermetallic compound porous material which has the average pore diameter of 30 mu m, the open porosity of 60 percent and the total porosity of 65 percent and is consistent with the designed components. The microstructure of the B2-FeAl intermetallic compound porous material is shown in figures 3, 4 and 5.
Example 2
Embodiment 2 of the present invention provides a method for preparing an iron-aluminum intermetallic compound porous material, specifically including the following steps:
(1) selecting element iron powder, element magnesium powder and aluminum: taking three powders of aluminum-magnesium alloy powder with the magnesium atom percentage of 65 percent and 35 percent as raw material powder, respectively weighing element iron powder, element magnesium powder and aluminum-magnesium alloy powder according to the atom percentage of magnesium accounting for 40 percent of the Fe-Al-Mg ternary mixed powder and the proportion of the iron-aluminum atom percentage of 1:3 to obtain the FeAl alloy powder with the designed component3The intermetallic compound porous material of (2). The particle sizes of the iron powder, the magnesium powder and the aluminum magnesium alloy powder are all 80 mu m. And mixing the Fe-Al-Mg ternary powder in an argon atmosphere after weighing is finished. Subsequently, the mixed powder was formed by cold isostatic pressing at a pressing pressure of 200 MPa.
(2) And (4) putting the pressed blank into a high vacuum sintering furnace for sintering and pore-forming. Firstly, the temperature is increased to 480 ℃ at the heating rate of 5 ℃/min, and the blank is kept at the temperature for 1 h. At the stage, the aluminum-magnesium alloy powder can be changed into an instantaneous liquid phase, aluminum atoms in the liquid phase continuously diffuse/react to surrounding iron particles, a pore-forming process of liquid-phase dealloying is carried out, and a FeAl intermetallic compound framework is gradually formed. In the process, the instantaneous liquid phase of the aluminum-magnesium component is continuously converted to a component with high magnesium content due to the continuous removal of aluminum. As a result, the original transient liquid phase of the aluminum-magnesium component becomes a solid phase.
(3) And continuously heating the blank to 580 ℃ at the heating rate of 5 ℃/min, and preserving the heat for 1 h. At this stage, the magnesium-rich al-mg solid phase becomes a liquid phase again, and the liquid phase dealloying pore-forming process in step (2) of this example is repeated, during which the al-mg transient liquid phase becomes an al-mg solid phase with new components again. In addition, during this stage, a pore-forming process of gas-phase dealloying due to magnesium sublimation or volatilization also occurs.
(4) And continuously heating the blank to 620 ℃ at the heating rate of 5 ℃/min, and keeping the temperature for 1 h. At this stage, the magnesium-rich solid-phase of Al and Mg is changed to liquid phase again, and the liquid-phase and gas-phase dealloying pore-forming process in step (3) of this example is repeated.
(5) The blank is continuously heated to 655 ℃ at the heating rate of 5 ℃/min and is kept warm for 1 h. In the stage, the residual magnesium in the ternary Fe-Al-Mg system is continuously reduced through gas phase dealloying until the residual magnesium completely disappears, the porosity of the system is further improved, and the binary Fe-Al system without magnesium residue is obtained. During this process, a small amount of residual elemental aluminum is present due to the disappearance of magnesium.
(6) And continuously heating the blank to 680 ℃ at the heating rate of 5 ℃/min, and preserving the heat for 1.5 h. The residual aluminum simple substance is changed into liquid phase and reacts with the FeAl matrix around, the porosity is further expanded, and a binary Fe-Al system without the simple substance aluminum residue is obtained.
(7) Continuously heating the blank to 950 ℃ at the heating rate of 5 ℃/min, preserving the heat for 2 h, increasing the porosity through further diffusion/reaction between iron and aluminum, and simultaneously completing homogenization of the components to finally obtain FeAl with the average pore diameter of 65 mu m, the open porosity of 50 percent and the total porosity of 60 percent, which are consistent with the designed components3An intermetallic porous material.
Example 3
Embodiment 3 of the present invention provides a method for preparing an iron-aluminum intermetallic compound porous material, which specifically includes the following steps:
(1) selecting element iron powder, element magnesium powder and aluminum: the magnesium-aluminum alloy powder with the magnesium atom percentage of 30 percent to 70 percent is taken as raw material powder, and the magnesium accounts for 40 percent of the Fe-Al-Mg ternary mixed powder according to the atom percentage and the iron-aluminum atomRespectively weighing the element iron powder, the element magnesium powder and the aluminum-magnesium alloy powder according to the ratio of 2:5 to obtain the designed component Fe2Al5The intermetallic compound porous material of (2). The particle sizes of the iron powder, the magnesium powder and the aluminum magnesium alloy powder are all 50 μm. And after weighing is finished, mixing the Fe-Al-Mg ternary element powder in an argon atmosphere. Subsequently, the mixed powder was molded by press molding at a pressing pressure of 300 MPa.
(2) And (4) putting the pressed blank into a high vacuum sintering furnace for sintering and pore-forming. The temperature was first raised to 460 ℃ at a rate of 2 ℃/min, at which temperature the blank was held for 1 h. In the stage, a large amount of transient liquid phase is generated, aluminum atoms in the liquid phase continuously diffuse/react to surrounding iron particles, a pore-forming process of liquid phase dealloying is generated, and an iron-aluminum intermetallic compound framework is gradually formed. In the process, the instantaneous liquid phase of the aluminum-magnesium component is continuously converted to a component with high magnesium content due to the continuous removal of aluminum. As a result, the original transient liquid phase of the al-mg component is converted back to the solid phase.
(3) And continuously heating the blank to 520 ℃ at the heating rate of 2 ℃/min, and keeping the temperature for 2 h. At this stage, the magnesium-rich aluminum-magnesium solid phase becomes a liquid phase again, and the liquid phase dealloying process in step (2) is repeated, and meanwhile, the vapor phase dealloying caused by magnesium sublimation or volatilization also occurs in the process.
(4) And continuously heating the blank to 580 ℃ at the heating rate of 2 ℃/min, and preserving the heat for 2 h. At this stage, the magnesium-rich solid phase of aluminum and magnesium is changed into liquid phase again, and the liquid phase and gas phase dealloying process in the step (3) is repeated.
(5) And continuously heating the blank to 630 ℃ at the heating rate of 2 ℃/min, and keeping the temperature for 2 h. At this stage, the magnesium-rich solid phase of aluminum and magnesium is changed into liquid phase again, and the liquid phase and gas phase dealloying process in the step (4) is repeated.
(6) And continuously heating the blank to 658 ℃ at the heating rate of 1 ℃/min, and preserving the temperature for 2 h. At this stage, the residual magnesium in the ternary Fe-Al-Mg system is completely removed through gas-phase dealloying, so that the porosity of the system is further improved, and the binary Fe-Al system without magnesium residue is obtained.
(7) The blank is continuously heated to 675 ℃ at the heating rate of 1 ℃/min and is kept warm for 1.5 h. In the stage, residual simple substance aluminum forms a liquid phase and is diffused or reacted with the formed iron-aluminum intermetallic compound or solid solution, so that the porosity of the system is further improved, and a binary Fe-Al system without the residual simple substance aluminum is obtained.
(8) Continuously heating the blank to 1000 ℃ at the heating rate of 5 ℃/min, preserving the heat for 2 h, completing the homogenization of Fe-Al components, and finally obtaining Fe with the average pore diameter of 45 mu m, the open porosity of 55 percent and the total porosity of 60 percent, which are consistent with the designed components2Al5An intermetallic compound.
The protective scope of the present invention is not limited to the above-described embodiments, and it is apparent that various modifications and variations can be made to the present invention by those skilled in the art without departing from the scope and spirit of the present invention. It is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.

Claims (6)

1. A preparation method of an iron-aluminum intermetallic compound porous material is characterized in that iron powder, aluminum-magnesium alloy powder and magnesium powder are mixed under vacuum or inert atmosphere to obtain uniformly mixed Fe-Al-Mg ternary mixed powder, and the ternary mixed powder is subjected to vacuum sintering after being pressed and formed; the aluminum magnesium alloy powder forms a low-temperature transient liquid phase in the vacuum sintering process; the iron powder, the aluminum magnesium alloy powder and the magnesium powder in the ternary mixed powder are mixed according to the atomic percentage of z (tFe-xAl) -yMg, the value of x is 22.5% -76.5%, and t = 1-x; y is 30% -60%, and z = 1-y; wherein (tFe-xAl) represents the chemical formula of the finally prepared iron-aluminum intermetallic compound, and t and x respectively represent the atomic percent of Fe and Al in the iron-aluminum intermetallic compound; y represents the atomic percentage of the sum of magnesium in the aluminum magnesium alloy powder and magnesium in the magnesium powder in the ternary mixed powder; the atomic ratio of aluminum to magnesium in the aluminum-magnesium alloy powder in the ternary mixed powder is 1: 4-4: 1; the vacuum sintering comprises the following steps:
(1) heating the ternary mixed powder compact of the pressed and formed Fe-Al-Mg to an instantaneous liquid phase temperature region of the aluminum-magnesium alloy powder, and preserving heat for 2-7 hours in the instantaneous liquid phase temperature region; the temperature range of the instantaneous liquid phase temperature zone is 450-650 ℃;
(2) continuously heating to the melting point temperature region of the magnesium and preserving the heat for 0.5-4 h in the melting point temperature region of the magnesium; the temperature range of the melting point temperature area of the magnesium is 650-660 ℃;
(3) continuously heating to the melting point temperature area of the aluminum and preserving heat for 0.5-1.5 h in the melting point temperature area of the aluminum; the temperature range of the melting point temperature zone of the aluminum is 665-685 ℃;
(4) and continuously heating to 900-1100 ℃, and preserving the heat for 1-2 h at the temperature.
2. The method according to claim 1, wherein the ternary mixed powder comprises 0.1 to 500 μm in particle size of iron powder, 0.1 to 500 μm in particle size of aluminum-magnesium alloy powder, and 0.1 to 500 μm in particle size of magnesium powder.
3. The method according to claim 1, wherein the pressure for press forming is greater than 50 MPa.
4. The method according to claim 1, wherein a degree of vacuum of the vacuum sintering is less than 0.1 Pa.
5. The method for preparing an iron-aluminum intermetallic compound porous material according to claim 1, characterized in that the temperature rise rate in the steps (1), (2), (3) and (4) is controlled to be 1 ℃/min to 10 ℃/min.
6. The method for preparing an Fe-Al based intermetallic compound porous material according to claim 5, characterized in that the pore diameter of the prepared porous material is 10 to 100 μm, and the open porosity and the total porosity can respectively reach more than 50% and 60%.
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