Fe-Al-Nb alloy and preparation method thereof

Abstract

The invention belongs to the technical field of metal preparation, and particularly relates to a Fe-Al-Nb alloy and a preparation method thereof. Comprising the following steps: mixing ferric oxide, niobium pentoxide powder and a metal diluent, performing ball milling, and pressing into a green body; and the blank is put into a reaction kettle, then an ignition agent is added, protective gas is inflated, a self-propagating reaction is conducted at the temperature of 260-300 DEG C, and the Fe-Al-Nb alloy is obtained. The Fe-Al-Nb alloy is prepared through the self-propagating reaction, the reaction temperature is reduced, the thermal stress during forming is improved, the temperature of the self-propagating reaction is only 260-300 DEG C, meanwhile, the self-propagating reaction mode is adopted, the alloy is rapidly cooled after reacting, the fine grain strengthening effect is promoted to be more obvious, a microstructure of a Fe3Al matrix phase and a C14 Laves reinforced phase is formed, and the Fe-Al-Nb alloy is obtained. And the distribution of a reinforced phase is more uniform, and the wear resistance of the material is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal preparation, and particularly relates to an Fe-Al-Nb alloy and a preparation method thereof. Background Art

[0002] Mechanical equipment and components face relatively harsh working environments. Prolonged friction and wear may lead to rapid damage of components. Traditional wear-resistant materials such as hardened steel and tungsten alloys provide effective protection to a certain extent, but their costs are high and resources are limited. Therefore, developing a new wear-resistant material to reduce costs and improve durability has become an urgent need in the industrial community.

[0003] Fe-Al-Nb alloys are usually prepared by methods such as electric arc furnace melting, high-frequency induction furnace melting, levitation melting furnace induction melting, and drop casting. Among them, electric arc melting is an electrothermal metallurgy method that uses electric energy to generate an electric arc between electrodes or between an electrode and alloy materials to melt Fe-Al-Nb alloys; high-frequency induction furnace melting works based on the principle of electromagnetic induction. When high-frequency alternating current passes through the inductor, an alternating magnetic field will be generated around it. When the Fe-Al-Nb alloy is placed in this magnetic field, induced current will be generated inside the metal. Since the metal itself has resistance, Joule heat will be generated when eddy currents flow inside the metal, thereby rapidly heating and melting the metal; levitation melting furnace induction melting uses an induction coil to induce eddy currents in a high-frequency magnetic field, and converts the eddy current loss into heat energy to quickly heat the alloy material to the melting temperature; the pure iron drop melting smelting technology, as an advanced heat treatment process, its core lies in converting high-purity metal raw materials into tiny droplets and performing melting and specific gravity separation in a high-temperature environment.

[0004] However, these methods have high requirements for raw materials, high energy consumption, and high costs. Moreover, during forming, due to the slow cooling rate and uneven distribution of reinforcement phases, the wear resistance of Fe-Al-Nb alloy materials is poor. Summary of the Invention

[0005] To solve the above problems, the present invention provides an Fe-Al-Nb alloy and a preparation method thereof. It solves the problems of poor wear resistance and high cost of existing Fe-Al-Nb alloy materials. The prepared Fe-Al-Nb alloy can effectively reduce the friction coefficient, significantly improve the wear resistance of the material, and has a low preparation cost.

[0006] The present invention solves the above technical problems through the following technical solutions.

[0007] The first object of the present invention is to provide a preparation method of an Fe-Al-Nb alloy, comprising the following steps: Mix ferric oxide, niobium pentoxide powder, and a metal diluent, and after ball milling, press them into a green body.

[0008] Put the green body into a reaction kettle, then add an ignition agent and fill it with a protective gas, and carry out a self-propagating reaction at 260 °C to 300 °C. During the self-propagating reaction, redox reactions occur among iron oxide, niobium pentoxide powder and metal diluent, forming a microstructure of Fe3Al matrix phase and C14 Laves strengthening phase, and obtaining an Fe-Al-Nb alloy.

[0009] In the present invention, by using iron oxide, niobium pentoxide powder and metal diluent, the raw material cost can be significantly reduced. At the same time, an Fe-Al-Nb alloy is prepared by means of a self-propagating reaction. During this process, the metal diluent participates in the reaction and undergoes redox reactions with iron oxide and niobium pentoxide powder, reducing the reaction temperature and improving the thermal stress during forming. The temperature of the self-propagating reaction only needs to be 260 °C to 300 °C, greatly reducing the energy consumption. At the same time, by adopting the self-propagating reaction method, the alloy is rapidly cooled after the reaction, promoting a more obvious fine grain strengthening effect, forming a microstructure of Fe3Al matrix phase and C14 Laves strengthening phase, and making the strengthening phase more uniformly distributed. The prepared alloy has a good forming effect and a high density, further improving the wear resistance of the material. The diameter of the prepared Fe-Al-Nb alloy material can reach 150 mm to 200 mm, and the thickness reaches 8 mm to 12 mm.

[0010] In the present invention, for the prepared Fe-Al-Nb alloy, during the wear process, the matrix phase is worn first, and then micro-protrusions with surface texture characteristics are formed between the strengthening phase and the matrix. The surface texture-like micro-protrusions can disperse the contact pressure to multiple contact points, avoiding the high friction force generated by a single large-area contact. During the friction process, the contact pressure is distributed on multiple micro-protrusions, reducing the local friction and wear, and thus reducing the overall friction coefficient. In some friction contacts, especially under dry friction conditions, adhesion may occur on the material surface. The micro-protrusions can effectively reduce the adhesion phenomenon by changing the contact surface shape and contact mode, thereby reducing the friction coefficient.

[0011] It should be noted that the ball milling method is dry milling for 6 h at a rotational speed of 170 r / min, and the ball-to-powder ratio is 1:2. The purpose of ball milling is to uniformly refine and mix iron oxide, niobium pentoxide powder and metal diluent, increase the specific surface area of the reactants, and the uniformly refined mixed powder can quickly reach the reaction temperature, accelerate the propagation of the combustion wave, and reduce the local unreacted area caused by too large particles.

[0012] It should be noted that the preparation method of the green body is to divide the mixed powder formed by iron oxide, niobium pentoxide powder and metal diluent into 8 portions and sequentially put them into a mold with a diameter of 78 mm, and apply a pressure of 50 MPa to obtain the green body.

[0013] In a specific embodiment, the dosage of the metal diluent is 4.8 wt.% to 5.5 wt.% of the total mass of the green body. The metal diluent is a mixture of aluminum powder and iron powder, and the mass ratio of iron powder to aluminum powder is 6 to 6.5:1. It should be noted that in the present invention, the aluminum powder undergoes a redox reaction with iron oxide and niobium oxide to form aluminum oxide, Fe3Al, and Nb. At high temperatures, trace amounts of Nb dissolve into Fe3Al, and the remaining Nb precipitates in situ to form the second phase C14 Laves Nb(Fe,Al)2, releasing a large amount of heat. The Fe3Al matrix phase formed by the reaction of iron powder and aluminum powder absorbs heat, reducing the reaction temperature and improving the thermal stress during molding, thereby obtaining a good molding effect and a high density, and further improving the wear resistance of the material. Moreover, the Fe3Al matrix phase formed by the redox reaction of aluminum powder and iron oxide, and the ratio of Fe3Al formed by the reaction of iron powder and aluminum powder to Fe3Al formed by the redox reaction of aluminum powder and iron oxide is 1:9. When the content of the diluent is too low, the improvement effect is not obvious and the alloy molding is not dense. When the content of the diluent is too high, it will lead to incomplete reaction or the reaction cannot start. Therefore, the dosage of the metal diluent used in the present invention aims to reduce the temperature during the reaction, improve the thermal stress during molding, reduce the temperature during the reaction, so that the alloy has a good molding effect and a high density, and further improves the wear resistance of the material.

[0014] In a specific embodiment, the mass ratio of iron(III) oxide, niobium pentoxide powder, and aluminum powder is 14.72 to 4.4:1 to 2.85:7.15 to 2.37. It should be noted that in the present invention, the purpose is to form an alloy with Fe3Al as the matrix and C14 Laves Nb(Fe,Al)2 as the reinforcement during the preparation of the Fe-Al-Nb alloy. Therefore, the ratio of iron(III) oxide, niobium pentoxide powder, and aluminum powder has a great influence on the phase structure formed by the alloy. When the aluminum content increases, FeAl phase and / or Al2Nb phase may be formed. When the amount of iron(III) oxide or niobium pentoxide increases, the reaction is incomplete, which affects the uniform distribution of the reinforcement phase and reduces the density.

[0015] In a specific embodiment, the dosage of the ignition agent is 0.1 wt.% to 0.2 wt.% of the total mass of the green body. It should be noted that in the present invention, the aluminum in the metal diluent requires a relatively high starting temperature to activate the thermal reaction. The ignition agent helps the reaction enter a self-sustaining high-temperature state by providing sufficient heat in the initial stage. Therefore, the ignition agent can be an alloy ignition agent commonly selected by those skilled in the art. In a preferred embodiment, the ignition agent is composed of potassium nitrate, sulfur, manganese dioxide, and aluminum powder in a mass ratio of 8:5:6:4. A small amount of the ignition agent can help reduce the starting temperature of the thermite reaction, enabling the reaction to start at a relatively low temperature, thereby reducing the required external energy input. When the content of the ignition agent increases, more impurity elements such as S, K, N, and Mn will be introduced into the material, which will reduce the performance of the alloy.

[0016] In a specific embodiment, the protective atmosphere is argon, and the gas pressure of the protective gas is 4 MPa to 6 MPa. It should be noted that in the present invention, after filling the protective gas for purging, the protective gas is filled again to maintain the pressure at 4 MPa to 6 MPa.

[0017] In a specific embodiment, by mass percentage, the composition of the Fe-Al-Nb alloy is: Fe: 70.4 wt.% to 81.2 wt.%, Al: 7.4 wt.% to 9.2 wt.%, Nb: 5.1 wt.% to 17.1 wt.%, C: 3.7 wt.% to 4.1 wt.%, and O: 0.8 wt.% to 1.0 wt.%, with a total of 100%.

[0018] The second object of the present invention is to provide the Fe-Al-Nb alloy obtained by the above preparation method. The microstructure of the Fe-Al-Nb alloy consists of a Fe3Al matrix phase and a C14 Laves reinforcement phase. The reinforcement phase presents spherical and strip-like structural morphologies at the microscale. The average particle size of the spherical reinforcement phase is 0.5 μm to 2 μm, the length of the strip-like reinforcement phase is 0.5 μm to 20 μm, and the width is 0.2 μm to 3 μm. The reinforcement phase presents a network-like and cluster-like distribution pattern at the macroscale. It should be noted that during the wear process, the matrix phase wears first, and then micro-protrusions with surface texture characteristics are formed between the reinforcement phase and the matrix. This micro-protrusion structure formed by the network-like and cluster-like distributed reinforcement phase can effectively reduce the friction coefficient, thereby significantly improving the wear resistance of the material. Different morphologies of the reinforcement phase have a significant impact on the wear rate. Compared with the randomly distributed reinforcement phase, the network-like and cluster-like reinforcement phase can more effectively reduce the wear rate.

[0019] In a specific embodiment, the hardness of the Fe-Al-Nb alloy is 450 HV to 510 HV.

[0020] The present invention has the following beneficial effects compared with the prior art: The present invention uses iron oxide, niobium pentoxide powder and a metal diluent, which can significantly reduce the raw material cost. At the same time, the Fe-Al-Nb alloy is prepared by self-propagating reaction. During this process, the metal diluent participates in the reaction and undergoes a redox reaction with iron oxide and niobium pentoxide powder, reducing the reaction temperature and improving the thermal stress during forming. The temperature of the self-propagating reaction only needs to be 260 °C to 300 °C, greatly reducing the energy consumption. At the same time, by using the self-propagating reaction method, the alloy is rapidly cooled after the reaction, promoting a more obvious fine grain strengthening effect, forming a microstructure of Fe3Al matrix phase and C14 Laves strengthening phase, and making the strengthening phase more evenly distributed. The prepared alloy has a good forming effect and a high density, further improving the wear resistance of the material.

[0021] The metal diluent used in the present invention, aluminum powder undergoes a redox reaction with iron oxide and niobium oxide to generate aluminum oxide, Fe3Al and Nb. At high temperature, a small amount of Nb is dissolved in Fe3Al in situ, and the remaining Nb precipitates in situ to form the second phase C14 Laves Nb(Fe,Al)2, releasing a large amount of heat. The Fe3Al matrix phase formed by the reaction of iron powder and aluminum powder absorbs heat, reducing the reaction temperature and improving the thermal stress during forming, thereby obtaining a good forming effect and a high density, and further improving the wear resistance of the material.

[0022] The Fe-Al-Nb alloy prepared by the present invention has a microstructure composed of Fe3Al matrix phase and C14 Laves strengthening phase. Among them, the strengthening phase presents spherical and strip-shaped structural forms at the microscale. The average particle size of the spherical strengthening phase is 0.5 μm to 2 μm, the length of the strip-shaped strengthening phase is 0.5 μm to 20 μm, and the width is 0.2 μm to 3 μm. The strengthening phase presents a network and cluster-like distribution pattern at the macroscale. During the wear process, the matrix phase is worn first, and then micro-protrusions with surface texture characteristics are formed between the strengthening phase and the matrix. This micro-protrusion structure formed by the network and cluster-like distributed strengthening phase can effectively reduce the friction coefficient, thereby significantly improving the wear resistance of the material. Different forms of strengthening phases have a significant impact on the wear rate. Compared with the disordered distributed strengthening phase, the network and cluster-like strengthening phase can more effectively reduce the wear rate. Description of the Drawings

[0023] Figure 1 It is the SEM microstructural diagram and EDS element distribution diagram of the Fe-Al-Nb alloy prepared in Example 1 of the present invention. Figure 1 In the figure, Figure a is the SEM microstructural diagram with a size of 20 μm, Figure b is the SEM microstructural diagram with a size of 10 μm, and Figure c is the distribution of each element in the alloy and the EDS diagram.

[0024] Figure 2 SEM microstructural diagram and EDS element distribution diagram of the Fe-Al-Nb alloy prepared in Example 2 of the present invention Figure 2 In Figure a, it is the SEM microstructural diagram with a size of 20 μm, in Figure b, it is the SEM microstructural diagram with a size of 10 μm, and in Figure c, it is the distribution of each element in the alloy and the EDS diagram.

[0025] Figure 3 SEM microstructural diagram and EDS element distribution diagram of the Fe-Al-Nb alloy prepared in Example 3 of the present invention Figure 3 In Figure a, it is the SEM microstructural diagram with a size of 20 μm, in Figure b, it is the SEM microstructural diagram with a size of 10 μm, and in Figure c, it is the distribution of each element in the alloy and the EDS diagram.

[0026] Figure 4 X-ray diffraction pattern and phase calibration diagram of the Fe-Al-Nb alloy prepared by the present invention

[0027] Figure 5 Vickers hardness diagram of the Fe-Al-Nb alloy prepared by the present invention

[0028] Figure 6 Friction coefficient diagram of the friction and wear performance test of the Fe-Al-Nb alloy prepared by the present invention Figure 6 In Figure (a), it is the friction and wear performance test diagram under the condition of 5 N, in Figure (b), it is the friction performance test diagram under the condition of 7.5 N, in Figure (c), it is the friction performance test diagram under the condition of 10 N, and in Figure (d), it is the friction performance test diagram under the condition of 12.5 N.

[0029] Figure 7 Second-phase micro-protrusion diagram observed after the Fe-Al-Nb alloy prepared in Example 2 of the present invention was worn for two minutes

[0030] Figure 8 Wear rate diagram of the Fe-Al-Nb alloy prepared by the present invention Detailed implementation manners

[0031] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0032] It should be noted that the professional terms used in the present invention are only for the purpose of describing specific embodiments and are not intended to limit the protection scope of the present invention. Unless otherwise specifically stated, various raw materials, reagents, instruments, and equipment used in the following embodiments of the present invention can be obtained through market purchases or prepared by existing methods.

[0033] The following is a further illustration through specific embodiments.

[0034] Example 1 This example provides an Fe-Al-Nb alloy. By mass percentage, the components of the Fe-Al-Nb alloy are: Fe: 81.2 wt.%, Al: 9.2 wt.%, Nb: 5.1 wt.%, C: 3.7 wt.%, and O: 0.8 wt.%, with a total of 100%.

[0035] The preparation method of the above Fe-Al-Nb alloy includes the following steps: S1. According to the mass ratio of ferric oxide powder, aluminum powder, and niobium oxide powder being 14.72:7.15:1, and according to the fact that the iron powder and aluminum powder of the metal diluent account for 5.5 wt% of the total mass of the green body, where the mass ratio of the iron powder and aluminum powder in the metal diluent is 6.22:1; weigh ferric oxide powder, aluminum powder, niobium oxide powder, and iron powder for mixing to form a mixed powder, and place 1.5 kg of the mixed powder in a high-energy ball mill. According to the ball-to-material ratio of 1:2, dry mill for 6 h under the condition that the rotational speed of the high-energy ball mill is 170 r / min. After the ball milling is completed, divide the ball-milled material into 8 portions and sequentially place them in a mold with a diameter of 78 mm, and apply a pressure of 50 MPa to obtain a green body.

[0036] S2. Place the green body in a 27-mm-thick copper crucible of a SHS reactor, that is, a self-propagating high-temperature synthesis reactor, and then add an ignition agent. The ignition agent is obtained by mixing potassium nitrate, sulfur, manganese dioxide, and aluminum powder in a mass ratio of 8:5:6:4, and the ignition agent accounts for 0.1 wt% of the total mass of the green body. After purging the reaction vessel with argon to discharge the air in the vessel and then filling it with 4.5 MPa of argon, when the temperature is raised to 300 °C, the ignition agent reacts to release a large amount of heat, thereby initiating the reaction between the reaction materials. The reaction is completed within dozens of seconds to obtain the Fe-Al-Nb alloy.

[0037] Example 2 This example provides an Fe-Al-Nb alloy. By mass percentage, the components of the Fe-Al-Nb alloy are: Fe: 76.1 wt.%, Al: 8.9 wt.%, Nb: 10.0 wt.%, C: 4.1 wt.%, and O: 0.9 wt.%, with a total of 100%.

[0038] The preparation method of the above Fe-Al-Nb alloy comprises the following steps: S1. According to the mass ratio of ferric oxide powder, aluminum powder, and niobium oxide powder being 7.34:3.73:1.9, and according to the fact that the iron powder and aluminum powder of the metal diluent account for 5.2 wt% of the total mass of the green body, wherein the mass ratio of the iron powder and aluminum powder in the metal diluent is 6.22:1; weigh ferric oxide powder, aluminum powder, niobium oxide powder, and iron powder and mix them to form a mixed powder. Then, place 1.5 kg of the mixed powder in a high-energy ball mill. According to the ball-to-material ratio of 1:2, dry mill for 6 h under the condition that the rotational speed of the high-energy ball mill is 170 r / min. After the ball milling is completed, divide the ball-milled material into 8 portions and sequentially place them into a mold with a diameter of 78 mm, and apply a pressure of 50 MPa to obtain a green body.

[0039] S2. Place the green body in a 27-mm-thick copper crucible of an SHS reactor, that is, a self-propagating high-temperature synthesis reactor. Then, add an ignition agent, which is obtained by mixing potassium nitrate, sulfur, manganese dioxide, and aluminum powder according to the mass ratio of 8:5:6:4, and the ignition agent accounts for 0.1 wt% of the total mass of the green body. After purging the reaction vessel with argon to discharge the air in the vessel, fill it with 4.5 MPa of argon. When the temperature is raised to 300 °C, the ignition agent reacts and releases a large amount of heat, thereby triggering the reaction between the reaction materials. The reaction is completed within dozens of seconds to obtain the Fe-Al-Nb alloy.

[0040] Example 3 This example provides an Fe-Al-Nb alloy. By mass percentage, the components of the Fe-Al-Nb alloy are: Fe: 70.4 wt.%, Al: 7.4 wt.%, Nb: 17.1 wt.%, C: 4.1 wt.%, and O: 1.0 wt.%, with a total of 100%.

[0041] The preparation method of the above Fe-Al-Nb alloy comprises the following steps: S1. According to the mass ratio of ferric oxide powder, aluminum powder, and niobium oxide powder being 4.4:2.37:2.85, and according to the fact that the iron powder and aluminum powder of the metal diluent account for 5.5 wt% of the total mass of the green body, wherein the mass ratio of the iron powder and aluminum powder in the metal diluent is 6.22:1; weigh ferric oxide powder, aluminum powder, niobium oxide powder, and iron powder and mix them to form a mixed powder. Then, place 1.5 kg of the mixed powder in a high-energy ball mill. According to the ball-to-material ratio of 1:2, dry mill for 6 h under the condition that the rotational speed of the high-energy ball mill is 170 r / min. After the ball milling is completed, divide the ball-milled material into 8 portions and sequentially place them into a mold with a diameter of 78 mm, and apply a pressure of 50 MPa to obtain a green body.

[0042] S2. Place the green body in a 27-mm-thick copper crucible of the SHS reactor, i.e., the self-propagating high-temperature synthesis reactor, then add the ignition agent. The ignition agent is obtained by mixing potassium nitrate, sulfur, manganese dioxide, and aluminum powder in a mass ratio of 8:5:6:4, and the ignition agent accounts for 0.1 wt% of the total mass of the green body. After purging the reaction vessel with argon to remove the air in the vessel, fill it with argon at 4.5 MPa. When the temperature is raised to 300 °C, the ignition agent reacts and releases a large amount of heat, thus triggering the reaction between the reaction materials. The reaction is completed within dozens of seconds to obtain the Fe-Al-Nb alloy.

[0043] Comparative Example 1 This comparative example provides an Fe-Al alloy. By mass percentage, the components of the Fe-Al alloy are: Fe: 86.15 wt.% and Al: 12.85 wt.%, with a total of 100%.

[0044] The preparation method of the above Fe-Al-Nb alloy includes the following steps: S1. According to the mass ratio of iron oxide powder to aluminum powder being 2.16:1, and according to the total mass of the metal diluent iron powder and aluminum powder being 5.7 wt.%, wherein the mass ratio of the iron powder to the aluminum powder in the metal diluent is 6.22:1; weigh iron oxide powder, aluminum powder, and iron powder and mix them to form a mixed powder. Place 1.5 kg of the mixed powder in a high-energy ball mill, and dry mill it for 6 h at a ball-to-material ratio of 1:2 and a high-energy ball mill rotation speed of 170 r / min. After the ball milling is completed, divide the ball-milled material into 8 portions and sequentially place them in a mold with a diameter of 78 mm, and apply a pressure of 50 MPa to obtain the green body.

[0045] S2. Place the green body in a 27-mm-thick copper crucible of the SHS reactor, i.e., the self-propagating high-temperature synthesis reactor, then add the ignition agent. The ignition agent is obtained by mixing potassium nitrate, sulfur, manganese dioxide, and aluminum powder in a mass ratio of 8:5:6:4, and the ignition agent accounts for 0.1 wt% of the total mass of the green body. After purging the reaction vessel with argon to remove the air in the vessel, fill it with argon at 4.5 MPa. When the temperature is raised to 300 °C, the ignition agent reacts and releases a large amount of heat, thus triggering the reaction between the reaction materials. The reaction is completed within dozens of seconds to obtain the Fe-Al alloy.

[0046] Test the structures and properties of the Fe-Al-Nb alloys prepared in Examples 1 to 3 and Comparative Example 1, and the results are as follows: Figure 1 This is the SEM micrograph and EDS element distribution map of the Fe-Al-Nb alloy prepared in Example 1 of the present invention. Figure 1Figure a in [X] is the SEM micrograph with a size of 20 μm, Figure b is the SEM micrograph with a size of 10 μm, and Figure c is the EDS diagram of the distribution of each element in the alloy.

[0047] Figure 2 It is the SEM micrograph of the Fe-Al-Nb alloy prepared in Example 2 of the present invention and the EDS element distribution diagram. Figure 2 Figure a in [X] is the SEM micrograph with a size of 20 μm, Figure b is the SEM micrograph with a size of 10 μm, and Figure c is the EDS diagram of the distribution of each element in the alloy.

[0048] Figure 3 It is the SEM micrograph of the Fe-Al-Nb alloy prepared in Example 3 of the present invention and the EDS element distribution diagram. Figure 3 Figure a in [X] is the SEM micrograph with a size of 20 μm, Figure b is the SEM micrograph with a size of 10 μm, and Figure c is the EDS diagram of the distribution of each element in the alloy.

[0049] As Figures 1 to 3 shown, in the microstructures of the Fe-Al-Nb alloys prepared in Examples 1 to 3, the reinforcing phases present spherical and strip-like structural morphologies at the microscale. Among them, the average particle size of the spherical reinforcing phase is 0.5 μm to 2 μm, the length of the strip-like reinforcing phase is 0.5 μm to 20 μm, and the width is 0.2 μm to 3 μm. The reinforcing phases present a network and cluster-like distribution pattern at the macroscale. Figure 1 The distribution of each element in the alloy in Figure c in [X] is shown in Table 1. Figure 2 The distribution of each element in the alloy in Figure c in [X] is shown in Table 2. Figure 3 The distribution of each element in the alloy in Figure c in [X] is shown in Table 3. According to the results in Tables 1 to 3, by mass percentage, the components of the Fe-Al-Nb alloy are: Fe: 70.4 wt.% to 81.2 wt.%, Al: 7.4 wt.% to 9.2 wt.%, Nb: 5.1 wt.% to 17.1 wt.%, C: 3.7 wt.% to 4.1 wt.%, and O: 0.8 wt.% to 1.0 wt.%, with a total of 100%.

[0050] Table 1 Figure 1 The distribution of each element in the alloy in Figure c in [X] Table 2 Figure 2 The distribution of each element in the alloy in Figure c in [X] Table 3 Figure 3 The distribution of each element in the alloy in Figure c in [X] Figure 4 The X-ray diffraction pattern and phase calibration diagram of the Fe-Al-Nb alloy prepared for this invention are as follows. As Figure 4 shown, the Fe-Al-Nb alloys prepared in Examples 1 to 3 have a disordered body-centered cubic structure of Fe3Al and a strengthening phase of C14 Laves Nb(Fe,Al)2 phase.

[0051] The Fe-Al-Nb alloys prepared in Examples 1 to 3 and Comparative Example 1 were subjected to Vickers hardness and friction performance tests. The hardness test conditions were: load 198 g, dwell time 15 s.

[0052] Figure 5 The Vickers hardness diagram of the Fe-Al-Nb alloy prepared for this invention is as follows. As Figure 5 shown, the Vickers hardness value of the Fe-Al-Nb alloy prepared in Example 1 is 450 HV, the Vickers hardness value of the Fe-Al-Nb alloy prepared in Example 2 is 505 HV, and the Vickers hardness value of the Fe-Al-Nb alloy prepared in Example 3 is 510 HV. It can be seen that the Vickers hardness value of the Fe-Al-Nb alloy material prepared in this invention is 450 HV to 510 HV.

[0053] The material for the friction and wear test was an alloy block processed into a size of 15 mm × 15 mm × 3 mm, and the surface was polished with SiC sandpaper to 2000 mesh. Before the friction and wear test started, the square specimen was placed on the rotating table. After clamping the specimen block, the friction pair and the loading rod were connected and perpendicularly contacted with the specimen surface. The loading force and rotation speed during the test were controlled by weights and the rotating table respectively. In this invention, the friction and wear experiments of the alloy were carried out with a 6 mm Si3N4 ball under loading forces of 5 N, 7.5 N, 10 N, and 12.5 N at a rotation speed of 500 r / min, a total time of 30 min, and a rotation radius of 6 mm. The results are as Figures 6 to 8 shown.

[0054] Figure 6 The friction coefficient diagram of the friction and wear performance test of the Fe-Al-Nb alloy prepared for this invention is Figure 6 in which Figure (a) is the friction and wear performance test diagram under the condition of 5 N, Figure (b) is the friction and wear performance test diagram under the condition of 7.5 N, Figure (c) is the friction and wear performance test diagram under the condition of 10 N, and Figure (d) is the friction and wear performance test diagram under the condition of 15 N. As Figure 6As shown, in the initial stage of wear, the so-called "running-in" process usually occurs. In this stage, there may be tiny protrusions and unevenness on the contact surface, which are gradually worn smooth through friction. Due to the reduction of surface irregularities, the friction coefficient usually decreases. As the wear process progresses, the contact surface gradually becomes smooth, the wear amount increases, but the surface gradually stabilizes. In this stage, the friction coefficient usually remains at a relatively stable level.

[0055] Figure 7 This is the second-phase micro-protrusion diagram observed after the Fe-Al-Nb alloy prepared in Example 2 of the present invention was worn for two minutes. Among them, Figure 7 The small graph in the upper left corner is the graph of the friction coefficient changing with time. As Figure 7 shown, the surface of the outer circle usually experiences a longer friction path relative to the surface of the inner circle. Therefore, the wear amount per unit time may be relatively high. The contact range of the friction surface of the outer circle is wider, which makes its friction area larger, and may thus lead to a larger wear amount. The friction path of the inner circle is shorter, and the number of friction points may be less, resulting in less wear per unit time. As can be seen from Figure 7 after the wear has proceeded for 2 minutes, traces of lighter wear of the inner circle matrix and the reinforcement phase can be observed, and there are still scars with a certain roughness remaining. In the outer circle part, no scars with obvious roughness can be observed on the matrix. The matrix wears before the reinforcement phase, and there are still some worn scars in the reinforcement phase. Thus, micro-protrusions of a certain reinforcement phase are formed. Such surface texture-like micro-protrusions can disperse the contact pressure to multiple contact points, avoiding the high friction force generated by a single large-area contact. During the friction process, the contact pressure is distributed on multiple micro-protrusions, reducing local friction and wear, and thus reducing the overall friction coefficient. In friction contact, especially under dry friction conditions, adhesion may occur on the material surface. The micro-protrusions can effectively reduce the adhesion phenomenon by changing the contact surface shape and contact mode, thereby reducing the friction coefficient. Thus, a situation of a low friction coefficient under certain conditions as in Figure 6 is formed.

[0056] Figure 8 This is the wear rate diagram of the Fe-Al-Nb alloy prepared by the present invention. As Figure 8 shown, after wear, due to the introduction of the reinforcement phase, the wear rate can be significantly reduced. The micro-protrusions are affected by the morphology of the reinforcement phase and the magnitude of the force. Compared with strip-shaped and cluster-shaped ones, the network structure formed in Example 2 is more likely to form a micro-protrusion structure. Under different force conditions, the friction coefficient is significantly reduced in the initial stage of wear, and the wear rate is significantly reduced after wear.

[0057] In summary, the present invention uses iron oxide, niobium pentoxide powder and a metal diluent, which can significantly reduce the raw material cost. At the same time, the Fe-Al-Nb alloy is prepared by a self-propagating reaction. During this process, aluminum powder reacts with iron oxide and niobium oxide through a redox reaction to form the alloy. The reaction between iron powder and aluminum powder acts as a metal diluent, reducing the reaction temperature and improving the thermal stress during forming. The temperature of the self-propagating reaction is only required to be 260 °C to 300 °C, greatly reducing the energy consumption. At the same time, by using the self-propagating reaction method, the alloy is rapidly cooled after the reaction, promoting a more obvious fine-grain strengthening effect, forming a microstructure of Fe3Al matrix phase and C14 Laves reinforcement phase, and making the distribution of the reinforcement phase more uniform. The prepared alloy has a good forming effect and a high density. The microstructure of the Fe-Al-Nb alloy consists of Fe3Al matrix phase and C14 Laves reinforcement phase. Among them, the reinforcement phase presents spherical and strip-like structural forms at the microscale. The average particle size of the spherical reinforcement phase is 0.5 μm to 2 μm, the length of the strip-like reinforcement phase is 0.5 μm to 20 μm, and the width is 0.2 μm to 3 μm. The reinforcement phase presents a network-like and cluster-like distribution pattern at the macroscale. During the wear process, the matrix phase wears first, and then micro-protrusions with surface texture characteristics are formed between the reinforcement phase and the matrix. This micro-protrusion structure formed by the network-like and cluster-like distributed reinforcement phase can effectively reduce the friction coefficient, thus significantly improving the wear resistance of the material. Different forms of reinforcement phases have a significant impact on the wear rate. Compared with the randomly distributed reinforcement phase, the network-like and cluster-like reinforcement phases can more effectively reduce the wear rate.

[0058] It should be noted that when the present invention involves a numerical range, it should be understood that any value between the two endpoints of each numerical range and either of the two endpoints can be selected. Since the steps and methods adopted are the same as those in the embodiments, in order to avoid repetition, the present invention describes the preferred embodiments. Although the preferred embodiments of the present invention have been described, those skilled in the art can make additional changes and modifications to these embodiments once they know the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present invention.

[0059] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention also intends to include these changes and modifications.

Claims

1. A method for preparing a Fe-Al-Nb alloy, characterized in that: The following steps are involved: The iron oxide, niobium pentoxide powder and metal diluent are mixed, ball-milled and pressed into a green body; The blank is placed in a reactor, and then an igniter is added and a protective gas is filled in. A self-propagating reaction occurs at 260 ℃ ~ 300 ℃. During the self-propagating reaction, iron trioxide, niobium pentoxide powder and metal diluent undergo redox reactions to form a microstructure of Fe3Al matrix phase and C14 Laves reinforcement phase, and a Fe-Al-Nb alloy is obtained.

2. The method for preparing the Fe-Al-Nb alloy according to claim 1, characterized in that: The amount of the metal diluent is 4.8 wt.% to 5.5 wt.% of the total mass of the blank. The metal diluent is a mixture of aluminum powder and iron powder, and the mass ratio of iron powder to aluminum powder is 6 to 6.5:

1.

3. The method for preparing the Fe-Al-Nb alloy according to claim 1, characterized in that: The mass ratio of ferric oxide, niobium pentoxide powder and aluminum powder is 14.72-4.4:1-2.85:7.15-2.

37.

4. The method for preparing the Fe-Al-Nb alloy according to claim 1, characterized in that: The amount of the igniter used is 0.1 wt.% to 0.2 wt.% of the total mass of the green body.

5. The method for preparing the Fe-Al-Nb alloy according to claim 1, characterized in that: The protective atmosphere is argon, and the pressure of the protective gas is 4 MPa to 6 MPa.

6. The method for preparing the Fe-Al-Nb alloy according to claim 1, characterized in that: The components of the Fe-Al-Nb alloy are, by mass percentage, Fe: 70.4 wt.% to 81.2 wt.%, Al: 7.4 wt.% to 9.2 wt.%, Nb: 5.1 wt.% to 17.1 wt.%, C: 3.7 wt.% to 4.1 wt.%, and O: 0.8 wt.% to 1.0 wt.%, which total 100%.

7. A Fe-Al-Nb alloy prepared by the preparation method according to any one of claims 1 to 6, characterized in that: The microstructure of the Fe-Al-Nb alloy consists of a Fe3Al matrix phase and a C14 Laves reinforcement phase, wherein the reinforcement phase presents a spherical and strip-shaped structural morphology on a microscale, wherein the average particle size of the spherical reinforcement phase is 0.5 μm to 2 μm, the length of the strip reinforcement phase is 0.5 μm to 20 μm, and the width is 0.2 μm to 3 μm, and the reinforcement phase presents a network and cluster distribution on a macroscale.

8. The Fe-Al-Nb alloy according to claim 7, characterized in that: The hardness of the Fe-Al-Nb alloy is 450 HV to 510 HV.

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