CN113403518B - FeCoNiB containing eutectic structure x Multi-principal-element alloy and preparation method thereof - Google Patents
FeCoNiB containing eutectic structure x Multi-principal-element alloy and preparation method thereof Download PDFInfo
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Abstract
The invention relates toFeCoNiB containing eutectic structure x The multi-principal element alloy and the preparation method thereof, the atomic ratio contents of the alloy constituent elements Fe, Co, Ni and B are respectively 1: 1: 1: x (x ═ 0.2, 0.4, 0.6, 0.65, 0.8, 1), i.e. the addition of the B element, the alloy system presents a microstructure transformation from hypoeutectic to perfect eutectic to hypereutectic. The system is very suitable for researching the tissue evolution rule and the formation mechanism of the eutectic medium-high entropy alloy system in the supercooling non-equilibrium rapid solidification process. Compared with FeCoNiB film materials which have similar alloy elements but have distinct alloy components in the existing documents, the block alloy disclosed by the invention has the advantages that the component design is more reasonable, the organizational structure is clearer, the preparation process is simpler, the combination of a soft phase and a hard phase of a two-phase alloy is better realized, the hardness is improved by about 4 times to the maximum extent, and the obtained multi-principal-element block eutectic alloy has good fluidity and is beneficial to industrial production and application.
Description
Technical Field
The invention belongs to the technical field of multi-principal-element eutectic alloy and preparation, and relates to FeCoNiB containing an eutectic structure x Multi-principal element alloy and a preparation method thereof.
Background
The high-entropy alloy becomes one of new hot spots for scientific development of materials due to higher strength, hardness, wear resistance, corrosion resistance, irradiation resistance and the like. The components and process design are necessary ways to obtain the alloy with excellent obdurability and advanced high strength, the high-entropy alloy is formed by designing various alloy elements, and in order to realize different performance requirements, people can adjust the components and the process of the alloy, thereby greatly expanding the research range of the alloy.
In recent years, high-entropy alloys are developed from initial equal-atomic-ratio single-phase high-entropy alloys to non-equal-atomic-ratio multi-phase high-entropy alloys, and most typically, eutectic high-entropy alloys with the common advantages of eutectic alloys and high-entropy alloysAnd (5) developing and designing gold. The development of the eutectic high-entropy alloy well balances the relation between the yield strength and the plasticity of the material, and is an important way for developing the super high-entropy alloy with excellent strength and plasticity. However, due to different preparation techniques and processes, the eutectic compositions of high-entropy eutectic alloys in the same alloy system may have large differences, for example, Nb is found in CoCrFeNiNb alloy 0.45 、Nb 0.5 And Nb 0.65 Three eutectic compositions were reported in sequence. So far, the design of multi-element eutectic high-entropy alloy is not developed and perfected, and related quaternary eutectic medium-entropy alloy systems are rarely reported.
Disclosure of Invention
Technical problem to be solved
In order to avoid the defects of the prior art, the invention provides FeCoNiB containing eutectic structures x Multi-principal element alloy and a preparation method thereof.
Technical scheme
FeCoNiB containing eutectic structure x The multi-principal element alloy is characterized in that the atomic ratio contents of the alloy constituent elements Fe, Co, Ni and B are respectively 1: x, wherein x is 0.2, 0.4, 0.6, 0.65, 0.8 and 1.
The atomic ratio content of B determines the microstructure transformation of the alloy system from hypoeutectic to perfect eutectic to hypereutectic, and is a hypoeutectic system when x is 0.2, 0.4, 0.6, a eutectic system when x is 0.65, and a hypereutectic system when x is 0.8, 1.0.
The spacing between the eutectic alloy layers is stabilized below 800 nm.
The common cast structure of the medium-entropy alloy containing the eutectic structure contains element B, and the enthalpy of mixing of the element B with Fe, Co and Ni is respectively as follows: -26, -24, -24 kJ/mol.
The as-cast perfect eutectic alloy has a hardness of 773 HV.
Preparing the FeCoNiB containing eutectic structures x The method for the multi-principal-element alloy is characterized by comprising the following steps:
step 1: grinding and polishing raw materials Fe, Co, Ni and B to remove surface oxide skin, and weighing according to the proportion after cleaning by ultrasonic waves;
and 2, step: placing the block element B at the bottom of a crucible of a smelting furnace, completely covering the block element B with Fe, Co and Ni metals, repeating the high vacuum pumping process twice and filling protective gas;
and step 3: adopting a titanium ingot arc striking mode, striking an arc by virtue of a titanium ingot which is placed in a titanium ingot crucible in advance and smelting for 3-5 minutes, and smelting twice in sequence to eliminate residual oxygen in the furnace chamber; then transferring the electric arc gun after the titanium ingot is ignited to a raw material crucible for placing alloy, melting the alloy raw material by using electric arc to obtain alloy liquid, wherein the melting current of the alloy liquid is 110-150A, and the melting time is 3-5 min; after the primary smelting is finished, the heating power supply is turned off, and the alloy ingot casting is turned over by using a tool shovel after the melt is naturally cooled to be completely hardened;
and 4, step 4: immediately carrying out secondary smelting on the overturned alloy ingot, and adding magnetic stirring in the processes of third and fourth repeated overturning smelting, wherein the smelting time is 3-5min each time, and the current is 110-150A; the alloy turnover smelting process needs to be repeated for more than 3 minutes each time; cooling to obtain FeCoNiB x Eutectic medium entropy alloy ingot casting.
The purity of each element is higher than 99.9%.
The alloy turnover smelting process of the step 4 needs to be repeated at least five times.
The protective gas in the alloy smelting process is high-purity argon.
Advantageous effects
The invention provides FeCoNiB containing eutectic structures x The multi-principal-element alloy and the preparation method thereof are suitable for researching the tissue evolution rule and the formation mechanism of the eutectic medium-high entropy alloy system in the supercooling non-equilibrium rapid solidification process. Compared with FeCoNiB film materials which have similar alloy elements but have complete alloy components in the prior document, the block alloy disclosed by the invention has the advantages that the component design is more reasonable, the organizational structure is clearer, the preparation process is simpler, the combination of a soft phase and a hard phase of two-phase alloy is better realized, the hardness is improved by about 4 times to the maximum extent, and the obtained multi-principal-element block eutectic alloy fittingHas good fluidity and is beneficial to industrial production and application.
The invention designs the quaternary FeCoNiB containing eutectic structures by utilizing the electric arc melting technology x The medium-entropy alloy system is used for representing the performance of the medium-entropy alloy in different structural states, and researching the influence rule of the element B on the mechanical property of the medium-entropy alloy containing the eutectic structure. Compared with FeCoNiB film materials which have similar alloy elements and distinct alloy components and appear in the prior literature, the bulk eutectic high-entropy alloy designed by the invention has differences in preparation method, alloy components, alloy properties, alloy structure, application field and the like. The addition of the B element can greatly improve the strength of the alloy by about 4 times. In addition, the invention is helpful for enriching an entropy alloy system library in the eutectic, better understanding scientific problems such as tissue formation and interaction among elements in the solidification process of the entropy alloy, and the like, provides effective experiment and theoretical support for the design of the components of the entropy alloy in the eutectic containing B elements, and is also an ideal material for the deep undercooling rapid solidification alloy.
FeCoNiB containing eutectic structure x The medium-entropy alloy system has the following characteristics: in the experimental example, as the content of the element B is increased, the microstructure evolution of the medium-entropy alloy as-cast microstructure from hypoeutectic to complete eutectic to hypereutectic occurs. In addition, the addition of the B element can effectively improve the strength of the bulk alloy from the initial 280HV to 1123 HV. The purpose of the patent is to provide FeCoNiB containing a complete eutectic structure x The preparation method is never applied to the alloy system in the prior report. It should be noted that this system is a eutectic medium entropy alloy system well suited for super-cooled rapid solidification, which has not been reported in previous studies.
As-cast FeCoNiB designed by the invention x The alloy, the increase of B element can effectively improve the hardness and the strength of the alloy, and the hardness of the alloy is improved from the initial 280HV to 1123 HV. In addition, the alloy system has microstructure transformation from hypoeutectic to complete eutectic to hypereutectic, which is designed for understanding the entropy in eutectic and the structure transformation of high entropy alloyThe alloy with excellent strength and plasticity has reference function. It should be noted that the components of the completely eutectic alloy designed by the invention are not simple and can be determined, the system can be used for a supercooling rapid solidification experiment, the maximum supercooling degree obtained by the pre-experiment exceeds 300K, and the method is very suitable for researching the tissue evolution law and the formation mechanism of the supercooling rapid solidification of the high-entropy alloy system in the eutectic.
Drawings
FIG. 1 shows eutectic medium entropy alloy FeCoNiB provided by the invention x (x ═ 0.2, 0.4, 0.6, 0.65, 0.8, 1) XRD pattern;
FIG. 2 is an as-cast FeCoNiB prepared in example 1 of the present invention 0.4 And (4) an alloy scanning electron microscope microstructure image.
FIG. 3 is an as-cast FeCoNiB prepared according to example 2 of the present invention 0.6 And (4) an alloy scanning electron microscope microstructure image.
FIG. 4 is an as-cast FeCoNiB prepared in example 3 of the present invention 0.65 And (4) an alloy scanning electron microscope microstructure image.
FIG. 5 is an as-cast FeCoNiB prepared according to example 4 of the present invention 0.8 Alloy scanning electron microscope microstructure image.
FIG. 6 is an as-cast FeCoNiB prepared according to example 3 of the present invention 0.65 The alloy transmission electron mirror is scanned into a component map.
FIG. 7 shows an as-cast FeCoNiB provided by the present invention x (x is 0.2, 0.4, 0.6, 0.65, 0.8, 1) alloy hardness change at 500gf, 5 s.
Detailed Description
The invention will now be further described with reference to the following examples and drawings:
one of the objects of the present invention is to provide a FeCoNiB containing eutectic structure x The content of the constituent elements Fe, Co, Ni and B of the medium entropy alloy is 1: 1: 1: x (x is 0.2 to 1), and is a hypo-eutectic system when x is 0.2, 0.4, 0.6, a perfect eutectic system when x is 0.65, or a hyper-eutectic system when x is 0.8, 1.0. The eutectic lamellar microstructure of the alloy consists of an FCC phase and an orthorhombic structural phase.
The second purpose of the invention is to provide FeCoNiB x Entropy of eutecticThe preparation method of the alloy mainly comprises the following steps:
step 2, weighing Fe, Co, Ni and B elementary substance raw materials according to the mass ratio;
step 3, putting the sample into a crucible in the furnace body, and repeating the vacuumizing and inflating operation twice;
step 4, smelting to prepare FeCoNiB x Alloy ingot casting;
preferably, in the step 1, the purity of the selected Fe block, Co block, Ni block and B block is not lower than 99.95 wt.%, the surface of the raw material is polished by sand paper to remove oxide skin on the surface of the raw material, and then the raw material is placed in a beaker with alcohol and cleaned by ultrasonic for 10 minutes.
Preferably, in the step 2, the atomic ratio of 1: 1: 1: and x is converted into a corresponding mass ratio, the materials are weighed on an electronic balance with the precision of 1mg according to the mass ratio, the weighed materials are cleaned once by alcohol again by virtue of an ultrasonic cleaner, and the prepared alloy materials are filled into a sample bag and marked after drying.
Preferably, the step 3 is to put the block element B into the furnace, put the block element B into the bottom of the crucible of the furnace and completely cover the block element B with Fe, Co and Ni metal, prevent the electric arc from directly striking the surface of the element B during the first smelting, close the furnace after putting titanium ingot into the furnace, and vacuumize the furnace once to 1 × 10 -3 Introducing protective high-purity argon to 5 multiplied by 10 after Pa is lower -2 Washing the furnace with MPa, and vacuumizing for the second time to 1X 10 -3 Introducing high-purity argon to 5 multiplied by 10 after Pa is less -2 MPa。
Preferably, in the step 4, arc striking and smelting are performed for 3 to 5 minutes by means of a titanium ingot which is placed in a titanium ingot crucible in advance, and smelting is performed twice in sequence to eliminate oxygen remaining in the furnace chamber. And then transferring the electric arc gun after the titanium ingot is ignited to a raw material crucible for placing alloy, melting the alloy raw material by using electric arc to obtain alloy liquid, wherein the electric arc is prevented from directly striking on the block element B during melting to prevent the element B from being cracked in a furnace body, the melting current of the alloy liquid is 110-150A, and the melting time is 3-5 min. To be preliminarily smeltedAnd turning the alloy ingot for secondary smelting, adding magnetic stirring in the third and fourth repeated turning smelting processes, and closing the magnetic stirring during the last smelting to avoid element segregation induced by the magnetic field. The alloy turnover smelting process needs to be repeated for at least five times, the smelting current is 110A-150A, and the smelting time is not less than 3 minutes each time. Cooling to obtain button-shaped FeCoNiB x And (5) carrying out eutectic entropy alloy ingot casting.
It should be further noted that when the alloy ingot is turned over in the step 4 for repeated smelting, the alloy ingot must be rapidly turned over to avoid the alloy ingot from being cooled down and then arc-striking smelting, and the arc is struck on the high-temperature ingot to fuse the alloy ingot more easily and not to generate large burning loss and splashing.
Example 1:
as-cast FeCoNiB 0.4 Preparing the eutectic medium entropy alloy, wherein the contents of constituent elements Fe, Co, Ni and B are 1: 1: 1: 0.4, the specific preparation method comprises the following steps:
grinding and polishing the surface of the raw material to remove oxide skin, and performing ultrasonic cleaning by using alcohol to obtain FeCoNiB 0.4 The atomic ratio is calculated and converted into the mass ratio of the alloy, and then the corresponding masses of Fe, Co, Ni and B elements with the purity higher than 99.95 wt.% are respectively weighed by utilizing a balance with the precision of 1 mg.
Putting raw materials into a water-cooled copper mold crucible of a vacuum smelting furnace, firstly putting a block element B into the water-cooled copper mold crucible, putting the block element B into the bottom of the crucible of the smelting furnace, completely covering the block element B with Fe, Co and Ni metal, preventing electric arc from directly striking the surface of the element B during primary smelting, closing the furnace chamber after putting a titanium ingot into the furnace chamber, and vacuumizing the furnace chamber to 1 x 10 at one time -3 Introducing protective high-purity argon to 5 multiplied by 10 after Pa is lower -2 And (2) in MPa, the vacuumizing process needs to be repeated for 2 times to ensure that the air in the furnace cavity is exhausted completely.
Starting arc by using a titanium ingot which is placed in advance and smelting for 3-5 minutes to check the vacuum degree in the furnace chamber, then melting the alloy raw material by using electric arc smelting to obtain alloy liquid, wherein the electric arc is prevented from directly striking on the element B during smelting to prevent the element B from being cracked in the furnace body. Turning the primarily smelted alloy ingot for secondary smelting, and adding the alloy ingot in the third and fourth repeated turning smelting processesMagnetic stirring is carried out, and the magnetic stirring is closed when the smelting is carried out for the last time so as to avoid element segregation induced by a magnetic field. The alloy turnover smelting process needs to be repeated for at least five times, the smelting current is 110A-150A, and the smelting time is not less than 3 minutes each time. Cooling to obtain button-shaped FeCoNiB 0.4 And (5) carrying out eutectic entropy alloy ingot casting.
Taking out the master alloy to measure the burning loss rate, cutting and inlaying the block-shaped cast sample if the burning loss rate is less than three thousandths, sequentially using 600#, 1500#, 2500# and 4000# sandpaper for grinding, and then polishing the sample by using polishing paste with the thickness of 1.5 mu m until no scratch can be seen under a light lens with the magnification of 1000 times.
The phase composition analysis of the alloy is shown in FIG. 1. The X-ray diffraction analysis voltage parameter selects 40KV, the measurement angle is 20-120 degrees, and the scanning time is 25 min. As can be seen from the comparative analysis with the standard PDF card, the as-cast FeCoNiB 0.4 The phase structure of the alloy is mainly FCC phase, and the intensity and the number of the phase peaks of the orthorhombic structure are relatively small.
And corroding the metallographic specimen by aqua regia (3HCl +1HNO3), detecting the uniformity of the alloy structure by virtue of a scanning electron microscope, and observing the appearance of the microstructure. FIG. 2a shows as-cast FeCoNiB 0.4 The microstructure of the alloy is seen from the microstructure diagram, in which the number of primary phases of the alloy structure is large, and a eutectic structure is clearly present between the primary phases (see fig. 2 b).
The hardness of the ground and polished test piece was analyzed by means of a bench-type micro-hardness tester, and measurement and recording of a hardness test were carried out by using analytical test software (FIG. 7), the applied load at the time of the test was 500gf, the holding time was 5s, the test environment was a room temperature environment, and the alloy hardness measured in example 1 was 476.44 HV.
Example 2:
as-cast FeCoNiB 0.6 Preparing an entropy alloy in the eutectic, wherein the contents of constituent elements Fe, Co, Ni and B are 1: 1: 1: 0.6, the specific preparation method comprises the following steps:
grinding and polishing the surface of the raw material to remove oxide skin, and performing ultrasonic cleaning by using alcohol to obtain FeCoNiB 0.6 Converting into alloy mass ratio by atomic ratio calculation, and refiningAnd weighing corresponding masses of Fe, Co, Ni and B elements with the purity higher than 99.95 wt.% by a balance with the degree of 1 mg.
Putting raw materials into a water-cooled copper mold crucible of a vacuum smelting furnace, firstly putting a block element B into the water-cooled copper mold crucible, putting the block element B into the bottom of the crucible of the smelting furnace, completely covering the block element B with Fe, Co and Ni metal, preventing electric arc from directly striking the surface of the element B during primary smelting, closing the furnace chamber after putting a titanium ingot into the furnace chamber, and vacuumizing the furnace chamber to 1 x 10 at one time -3 Introducing protective high-purity argon to 5 multiplied by 10 after Pa is lower -2 And (5) in MPa, the vacuumizing process needs to be repeated for 2 times to ensure that the air in the furnace cavity is exhausted completely.
And (3) starting arc by using a pre-placed titanium ingot, smelting the titanium ingot for 3-5 minutes to check the vacuum degree in the furnace chamber, and then melting the alloy raw material by using electric arc smelting to obtain alloy liquid, wherein the electric arc is prevented from directly striking on the block element B during smelting to prevent the B element from being cracked in the furnace body. And turning over the primarily smelted alloy ingot for secondary smelting, adding magnetic stirring in the third and fourth repeated turning-over smelting processes, and closing the magnetic stirring during the last smelting to avoid element segregation induced by a magnetic field. The alloy turnover smelting process needs to be repeated for at least five times, the smelting current is 110A-150A, and the smelting time is not less than 3 minutes each time. Cooling to obtain button-shaped FeCoNiB 0.6 And (5) carrying out eutectic entropy alloy ingot casting.
Taking out the master alloy to measure the burning loss rate, cutting and inlaying the block-shaped cast sample if the burning loss rate is less than three thousandths, sequentially using 600#, 1500#, 2500# and 4000# sandpaper for grinding, and then polishing the sample by using polishing paste with the thickness of 1.5 mu m until no scratch can be seen under a light lens with the magnification of 1000 times.
The phase composition analysis of the alloy is shown in FIG. 1. The X-ray diffraction analysis voltage parameter selects 40KV, the measurement angle is 20-120 degrees, and the scanning time is 25 min. Compared with the standard PDF card, the peak intensity and the number of the orthogonal structure phase are obviously increased, and the as-cast FeCoNiB 0.6 The phase structure of the alloy still consists of FCC phase and orthorhombic phase.
The metallographic specimen was etched with aqua regia (3HCl +1HNO3), the homogeneity of the alloy structure was examined by means of a scanning electron microscope and the microstructure was shapedAnd (5) observing the appearance. FIG. 3a shows as-cast FeCoNiB 0.6 The microstructure of the alloy is mainly eutectic microstructure structure as can be seen from the microstructure diagram, and only a small amount of primary phases exist between the eutectic structures (as shown in figure 3 b).
The hardness of the ground and polished test piece was analyzed by a bench-type micro-hardness tester, and measurement and recording of a hardness test were carried out by using analytical test software (fig. 7), wherein the applied load during the test was 500gf, the holding time was 5s, the test environment was a room temperature environment, and the alloy hardness measured in example 2 was 684.56 HV.
Example 3:
as-cast FeCoNiB 0.65 Preparing an entropy alloy in the eutectic, wherein the contents of constituent elements Fe, Co, Ni and B are 1: 1: 1: 0.65, the specific preparation method comprises the following steps:
grinding and polishing the surface of the raw material to remove oxide skin, and performing ultrasonic cleaning by using alcohol to obtain FeCoNiB 0.65 And (3) calculating and converting the atomic ratio into the mass ratio of the alloy, and then weighing corresponding masses of Fe, Co, Ni and B elements with the purity higher than 99.95 wt.% by using a balance with the precision of 1 mg.
Putting raw materials into a water-cooled copper mold crucible of a vacuum smelting furnace, firstly putting a block element B into the water-cooled copper mold crucible, putting the block element B into the bottom of the crucible of the smelting furnace, completely covering the block element B with Fe, Co and Ni metal, preventing electric arc from directly striking the surface of the element B during primary smelting, closing the furnace chamber after putting a titanium ingot into the furnace chamber, and vacuumizing the furnace chamber to 1 x 10 at one time -3 Introducing protective high-purity argon to 5 multiplied by 10 after Pa is lower -2 The furnace is washed in MPa, and the vacuumizing process needs to be repeated for 2 times to ensure that the air in the furnace cavity is exhausted completely.
And (3) starting arc by using a pre-placed titanium ingot, smelting the titanium ingot for 3-5 minutes to check the vacuum degree in the furnace chamber, and then melting the alloy raw material by using electric arc smelting to obtain alloy liquid, wherein the electric arc is prevented from directly striking on the block element B during smelting to prevent the B element from being cracked in the furnace body. And turning over the primarily smelted alloy ingot for secondary smelting, adding magnetic stirring in the third and fourth repeated turning-over smelting processes, and closing the magnetic stirring during the last smelting to avoid element segregation induced by a magnetic field. The alloy turnover smelting process needs to be repeated at least five timesThe smelting current is 110A-150A, and the smelting time is not less than 3 minutes each time. Cooling to obtain button-shaped FeCoNiB 0.65 Eutectic medium entropy alloy ingot casting.
Taking out the master alloy to measure the burning loss rate, cutting and inlaying the block-shaped cast sample if the burning loss rate is less than three per thousand, sequentially using 600#, 1500#, 2500# and 4000# sandpaper for grinding, and then polishing the sample by using 1.5 mu m polishing paste until no scratch can be seen under a light lens with the magnification of 1000 times.
The phase composition analysis experiment result of the alloy is shown in figure 1, the X-ray diffraction analysis voltage parameter selects 40KV, the measurement angle is 20-120 degrees, and the scanning time is 25 min. Compared with the standard PDF card, the phase structure of the complete eutectic alloy consists of an FCC phase and an orthogonal structure phase.
And corroding the metallographic specimen by using aqua regia (3HCl +1HNO3), detecting the uniformity of the alloy structure by using a scanning electron microscope, and observing the microstructure appearance. FIG. 4a shows as-cast FeCoNiB 0.65 The microstructure of the alloy can be seen from the microstructure chart that the alloy structure is a complete eutectic structure (as shown in figure 4b), the lamellar structure of the alloy is basically less than 800nm, and different kinds of lamellar have obvious composition segregation (as shown in figure 6).
The hardness of the polished sample was analyzed by a bench-type microhardness tester, and measurement and recording of a hardness test were carried out by using analytical test software (fig. 7), wherein the applied load during the test was 500gf, the holding time was 5s, the test environment was room temperature, and the alloy hardness measured in example 3 was 773 HV.
Example 4:
as-cast FeCoNiB 0.8 Preparing an entropy alloy in the eutectic, wherein the contents of constituent elements Fe, Co, Ni and B are 1: 1: 1: 0.8, the specific preparation method comprises the following steps:
grinding and polishing the surface of the raw material to remove oxide skin, and performing ultrasonic cleaning by using alcohol to obtain FeCoNiB 0.8 And (3) calculating and converting the atomic ratio into the mass ratio of the alloy, and then weighing corresponding masses of Fe, Co, Ni and B elements with the purity higher than 99.95 wt.% by using a balance with the precision of 1 mg.
Putting the raw materials intoPutting a block element B into a water-cooled copper mold crucible of a vacuum smelting furnace, putting the block element B at the bottom of the crucible of the smelting furnace, completely covering the block element B with Fe, Co and Ni metal, preventing electric arc from directly striking the surface of the element B during primary smelting, closing the furnace after putting a titanium ingot into the furnace, and vacuumizing the furnace once to 1 multiplied by 10 -3 Introducing protective high-purity argon to 5 multiplied by 10 after Pa is lower -2 The furnace is washed in MPa, and the vacuumizing process needs to be repeated for 2 times to ensure that the air in the furnace cavity is exhausted completely.
The method comprises the steps of starting arc by means of a titanium ingot placed in advance and smelting the titanium ingot for 3-5 minutes to check the vacuum degree in a furnace cavity, then utilizing electric arc smelting to melt alloy raw materials and obtain alloy liquid, and avoiding the electric arc from directly striking on the bulk element B during smelting to prevent the B element from being broken in the furnace body. And turning over the primarily smelted alloy ingot to perform secondary smelting, adding magnetic stirring in the third and fourth repeated turning-over smelting processes, and closing the magnetic stirring during the last smelting to avoid element segregation induced by a magnetic field. The alloy turnover smelting process needs to be repeated for at least five times, the smelting current is 110A-150A, and the smelting time is not less than 3 minutes each time. Cooling to obtain button-shaped FeCoNiB 0.8 And (5) carrying out eutectic entropy alloy ingot casting.
Taking out the master alloy to measure the burning loss rate, cutting and inlaying the block-shaped cast sample if the burning loss rate is less than three per thousand, sequentially using 600#, 1500#, 2500# and 4000# sandpaper for grinding, and then polishing the sample by using 1.5 mu m polishing paste until no scratch can be seen under a light lens with the magnification of 1000 times.
The phase composition analysis experiment result of the alloy is shown in figure 1, the X-ray diffraction analysis voltage parameter selects 40KV, the measurement angle is 20-120 degrees, the scanning time is 25min, and the cast FeCoNiB 0.8 The phase structure of the alloy consists of an FCC phase and an orthorhombic phase, and the orthorhombic peak is already dominant in the phase peak composition.
The metallographic specimen was also corroded with aqua regia (3HCl +1HNO3), and the homogeneity of the alloy structure was examined by means of a scanning electron microscope and microstructure morphology was observed. FIG. 5a shows as-cast FeCoNiB 0.8 The microstructure of the alloy can be seen from the structure diagram that the alloy structure is hypereutectic structure, and the structure consists of eutectic laminas and primary phasesThe composition, the primary phase structure of the alloy has been completely transformed (see fig. 5 b).
The hardness of the ground and polished test piece was analyzed by means of a bench-type micro-hardness tester, and measurement and recording of a hardness test were carried out by using analytical test software (FIG. 7), the applied load at the time of the test was 500gf, the holding time was 5s, the test environment was a room temperature environment, and the alloy hardness measured in example 4 was 913.96 HV.
As can be seen from the change in hardness, the hardness of the alloy increases greatly with increasing content of B element, from the initial 280HV to the highest 1123 HV. The invention provides a preparation method of a quaternary eutectic medium-entropy alloy containing an element B, and an alloy system is never prepared by using the method. The invention improves the preparation process, the element B is completely coated in the alloy liquid in the smelting process, and the alloy ingot is smelted under the condition that the ingot is not completely cooled in the process of overturning and smelting, so that the burning loss of the alloy ingot can be effectively avoided.
In addition, it needs to be further explained that the components of the completely eutectic alloy designed by the invention are not simple and can be determined, the system is very suitable for carrying out supercooling rapid solidification experiments, and the experiments carried out in advance prove that the alloy can realize the large supercooling degree of 300K, so that the completely eutectic alloy is an ideal material for researching the tissue evolution law and the formation mechanism of the eutectic high-entropy alloy system in the nonequilibrium rapid solidification process. The block eutectic medium-entropy alloy system is reasonable in design, clear in organization structure and simple in preparation process, the combination of a soft phase and a hard phase of a two-phase alloy is well realized, the hardness is improved by about 4 times, and the obtained multi-principal-element eutectic alloy has good fluidity and is very suitable for industrial production.
When numerical values are included in the claims of the present invention, it should be noted that numerical values between each numerical value can be selected, and since the steps and methods adopted are the same as those of the embodiments, the present invention describes preferred embodiments and effects thereof in order to prevent redundancy. Additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all such alterations and modifications as fall within the scope of the invention.
Claims (7)
1. FeCoNiB containing eutectic structure x The multi-principal element alloy is characterized in that the atomic ratio contents of the alloy constituent elements such as Fe, Co, Ni and B are respectively 1: x, wherein x is 0.2, 0.4, 0.6, 0.65, 0.8 and 1;
the FeCoNiB containing eutectic structures x The method of the multi-principal element alloy comprises the following steps:
step 1: grinding and polishing raw materials Fe, Co, Ni and B to remove surface oxide skin, and weighing according to the proportion after cleaning by ultrasonic waves;
step 2: placing the block element B at the bottom of a crucible of a smelting furnace, completely covering the block element B with Fe, Co and Ni metals, repeating the high vacuum pumping process twice and filling protective gas;
and step 3: adopting a titanium ingot arc striking mode, striking an arc by virtue of a titanium ingot which is placed in a titanium ingot crucible in advance and smelting for 3-5 minutes, and smelting twice in sequence to eliminate residual oxygen in the furnace chamber; then transferring the electric arc gun after the titanium ingot is ignited to a raw material crucible for placing alloy, melting the alloy raw material by using electric arc to obtain alloy liquid, wherein the melting current of the alloy liquid is 110-150A, and the melting time is 3-5 min; after the primary smelting is finished, the heating power supply is turned off, and the alloy ingot casting is turned over by using a tool shovel after the melt is naturally cooled to be completely hardened;
and 4, step 4: immediately carrying out secondary smelting on the overturned alloy ingot, and adding magnetic stirring in the processes of carrying out third and fourth repeated overturning smelting, wherein the smelting time is 3-5min each time, and the current is 110-150A; the alloy turnover smelting process needs to be repeated for more than 3 minutes each time; cooling to obtain FeCoNiB x And (5) carrying out eutectic entropy alloy ingot casting.
2. FeCoNiB containing eutectic structure according to claim 1 x The multi-principal-element alloy is characterized in that: the spacing between the eutectic tissue layers is stabilized below 800 nm.
3. The composition of claim 1, comprisingFeCoNiB with crystal structure x The multi-principal-element alloy is characterized in that: the common cast structure of the multi-principal element alloy containing the eutectic structure contains element B, and the mixed enthalpy of the element B and Fe, Co and Ni is respectively as follows: 26kJ/mol, -24kJ/mol, -24 kJ/mol.
4. FeCoNiB containing eutectic structure according to claim 1 x The multi-principal-element alloy is characterized in that: when x is 0.65, the alloy is eutectic, and the hardness of the alloy is 773 HV.
5. FeCoNiB containing eutectic structure according to claim 1 x The multi-principal-element alloy is characterized in that: the purity of each element is higher than 99.9%.
6. FeCoNiB containing eutectic structure according to claim 1 x The multi-principal-element alloy is characterized in that: the alloy turnover smelting process of the step 4 needs to be repeated at least five times.
7. FeCoNiB containing eutectic structure according to claim 1 x The multi-principal-element alloy is characterized in that: the protective gas in the alloy smelting process is high-purity argon.
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