SPHERICAL IRON ALLOY POWDER MATERIAL PREPARATION METHOD THEREFOR, AND USE THEREOF

Abstract

The invention relates to a spherical iron alloy powder material, its preparation method, and its uses. By selecting a dominated FeLa based alloy system and adding special alloy elements for spheroidization precipitation and corrosion resistant, the invention achieves the dispersion of spherical Fe-rich particles containing spheroidization precipitation elements in a La-rich matrix phase during the alloy solidification process. By removing the La-rich matrix phase, spherical iron alloy powder materials with particle sizes ranging from the nanoscale to tens of micrometers are obtained. This method is simple and can produce spherical iron alloy powders with various morphologies, including nanoscale, submicron, and micron sizes. It has excellent application prospects in fields such as powder metallurgy, metal injection molding (MIM), 3D printing, magnetic materials, heat-resistant materials, high-temperature alloys, coatings, electrical heating materials, wave-absorbing materials, and magnetic fluids.

Claims

1. A method for preparing spherical iron alloy powder material, comprising the following steps: Step 1: select the initial alloy raw materials, melt the initial alloy raw materials according to the initial alloy composition ratio to obtain a uniform initial alloy melt; the main components of the initial alloy melt are La.sub.xFe.sub.yT.sub.zM.sub.aD.sub.b, where T includes at least one of Cr or V, M includes at least one of Al, Ni, Co, or Si, and D includes at least one of Mo, W, or Ti; x, y, z, a, and b represent the atomic percentage content of the corresponding element respectively, and 18%x95.8%, 4%y81.8%, 0.1%z35%, 0a40%, and 0b15%; Step 2: solidify the initial alloy melt into an initial alloy solid using rapid solidification technology; the solidified structure of the initial alloy solid includes a matrix phase and a dispersed particle phase; the melting point of the matrix phase is lower than that of the dispersed particle phase, and the dispersed particle phase is encapsulated within the matrix phase; the volume percentage of the matrix phase in the solidified structure is not less than 40%; the average composition of the matrix phase mainly consists of La.sub.x1M.sub.a1; the composition of the dispersed particle phase mainly consists of Fe.sub.y2T.sub.z2M.sub.a2D.sub.b2La.sub.x2, where x1, a1, x2, y2, z2, a2, and b2 represent the atomic percentage content of the corresponding constituent elements respectively, and 45%x1100%, 0%a155%, 50%y298%, 0.2%z2<50%, 0%a230%, 0%b235%, and 0<x25%; the dispersed particle phase includes a significant amount of spherical or near-spherical dispersed particles, with some spherical or near-spherical dispersed particles exhibiting certain dendritic features; the particle size of the dispersed particle phase ranges from 5 nm to 50 m; Step 3: remove the matrix phase from the initial alloy solid, retaining mainly the dispersed particle phase to obtain an iron alloy powder material with the main composition of Fe.sub.y2T.sub.z2M.sub.a2D.sub.b2La.sub.x2, where 50%y298%, 0.2%z2<50%, 0%a230%, 0%b235%, and 0<x25%; the iron alloy powder particles include a significant amount of spherical or near-spherical particles, with some spherical or near-spherical iron alloy powder particles exhibiting certain dendritic features; the particle size of the iron alloy powder particles ranges from 5 nm to 50 m.

2. The method for preparing a spherical iron alloy powder material according to claim 1, wherein the shape of the dispersed particle phase is mainly spherical or near-spherical.

3. The method for preparing a spherical iron alloy powder material according to claim 1, wherein the composition of the initial alloy melt in Step 1 also includes non-metallic impurity elements, which include at least one of O, N, H, P, S, CI; the atomic percentage content of these non-metallic impurity elements in the initial alloy melt is greater than 0% and less than 10%; during the formation of the Fe-rich dispersed phases in Step 2, these non-metallic impurity elements are concentrated in the La-rich matrix phase, thereby purifying the Fe-rich dispersed phases; that is, the atomic percentage content of non-metallic impurity elements in the Fe-rich dispersed phases is lower than in the initial alloy melt; and the atomic percentage content of non-metallic impurity elements in the Fe-rich dispersed phases is less than 1.5%; the content of non-metallic impurity elements in the spherical or near-spherical iron alloy powder particles in Step 3 is also lower than the content of these elements in the initial alloy melt.

4. A spherical iron alloy powder material, wherein the spherical iron alloy powder material is prepared by using the method described in claim 1; some characteristics of the spherical iron alloy powder material include: the main component of the spherical iron alloy powder material is Fe.sub.y2T.sub.z2M.sub.a2D.sub.b2La.sub.x2; where 50%y298%, 0.2%z2<50%, 0%a230%, 0%b235%, 0<x25%; the shape of the iron alloy powder particles is mainly spherical or near-spherical, and some spherical or near-spherical iron alloy powder particles contain certain dendritic features; the particle size of the iron alloy powder particles ranges from 5 nm to 50 m; where T includes at least one of Cr or V, M includes at least one of Al, Ni, Co, or Si, and D includes at least one of Mo, W, or Ti; x2, y2, z2, a2, and b2 represent the atomic percentage content of the corresponding element respectively.

5. A spherical iron alloy powder material, wherein the spherical iron alloy powder material is prepared by using the method described in claim 2; some characteristics of the spherical iron alloy powder material include: the main component of the spherical iron alloy powder material is Fe.sub.y2T.sub.z2M.sub.a2D.sub.b2La.sub.x2; where 50%y298%, 0.2%z2<50%, 0%a230%, 0%b235%, 0<x25%; the shape of the iron alloy powder particles is mainly spherical or near-spherical, and some spherical or near-spherical iron alloy powder particles contain certain dendritic features; the particle size of the iron alloy powder particles ranges from 5 nm to 50 m; where T includes at least one of Cr or V, M includes at least one of Al, Ni, Co, or Si, and D includes at least one of Mo, W, or Ti; x2, y2, z2, a2,and b2 represent the atomic percentage content of the corresponding element respectively.

6. A spherical iron alloy powder material, wherein the spherical iron alloy powder material is prepared by using the method described in claim 3; some characteristics of the spherical iron alloy powder material include: the main component of the spherical iron alloy powder material is Fe.sub.y2T.sub.z2M.sub.a2D.sub.b2La.sub.x2; where 50%y298%, 0.2%z2<50%, 0%a230%, 0%b235%, 0<x25%; the shape of the iron alloy powder particles is mainly spherical or near-spherical, and some spherical or near-spherical iron alloy powder particles contain certain dendritic features; the particle size of the iron alloy powder particles ranges from 5 nm to 50 m; where T includes at least one of Cr or V, M includes at least one of Al, Ni, Co, or Si, and D includes at least one of Mo, W, or Ti; x2, y2, z2, a2,and b2 represent the atomic percentage content of the corresponding element respectively.

7. A method for preparing spherical iron-chromium-silicon powder materials with high-silicon-content, wherein the spherical iron alloy powder material prepared in steps 1 to 3 of claim 1, with FeCr or low Si content FeCrSi as the main components, undergoes silicon infiltration treatment to obtain a high-Si-content spherical powder material with FeCrSi as the main component.

8. A high-silicon-content spherical iron-chromium-silicon powder material, wherein the high-silicon-content spherical iron-chromium-silicon powder material is prepared using the method described in claim 7.

9. A method for preparing a high-nickel-content iron-chromium-nickel powder metallurgy product, comprising the following steps: Step 1: prepare the initial alloy solid described in step 2 of claim 1 according to steps 1 and 2 of claim 1, where T includes Cr, M includes Ni, and 0<a40%; the average composition of the matrix phase is mainly La.sub.x1Ni.sub.a1; and the composition of the dispersed particle phase is mainly low-Ni-content Fe.sub.y2Cr.sub.z2Ni.sub.a2D.sub.b2La.sub.x2; in the La.sub.x1Ni.sub.a1 matrix phase, Ni combines with La through intermetallic compounds, and 0<a212%; Step 2: remove the La from the La.sub.x1Ni.sub.a1 matrix phase of the initial alloy solid using a dealloying reaction with a dilute acid solution, while ensuring that most of the Ni in the original La.sub.x1Ni.sub.a1 matrix phase remains, resulting in a composite powder of nanoporous Ni and low-Ni-content Fe.sub.y2Cr.sub.z2Ni.sub.a2D.sub.b2La.sub.x2 particles; Step 3: press and sinter the composite powder of nanoporous Ni and low-Ni-content Fe.sub.y2Cr.sub.z2Ni.sub.a2D.sub.b2La.sub.x2 particles to obtain a high-Ni-content iron-chromium-nickel powder metallurgy product with a main component of Fe.sub.y3Cr.sub.z3Ni.sub.a3D.sub.b3La.sub.x3; x3, y3, z3, a3, b3 represent the atomic percentage content of the corresponding elements respectively, and 0<y3 y2, 0<z3<z2, 0<a2<a3, 0b3b2, 0<x3<x2.

10. A high-nickel-content iron-chromium-nickel powder metallurgy product, wherein the high-nickel-content iron-chromium-nickel powder metallurgy product is prepared using the method described in claim 9.

11. A composite powder of nanoporous Ni and low-Ni-content iron-chromium-nickel particles, wherein the composite powder of nanoporous Ni and low-Ni-content iron-chromium-nickel particles is prepared using steps 1 and 2 of the method described in claim 9.

12. The application of the spherical iron alloy powder material described in claim 4 in any of the following fields: general powder metallurgy, metal injection molding (MIM), 3D printing, magnetic materials, heat-resistant materials, high-temperature alloys, coatings, and wave-absorbing materials.

13. The application of the spherical iron alloy powder material described in claim 4 in the field of electric heating materials, where the main components of the spherical iron alloy powder material include FeCrAl.

14. The application of the high-silicon-content spherical iron-chromium-silicon powder material according to claim 7 in magnetic materials.

15. The application of the high-nickel content iron-chromium-nickel powder metallurgy product according to claim 10 in high-temperature alloys.

16. An alloy solid, wherein the alloy solid is prepared through the preparation method of the initial alloy solid described in steps 1 and 2 of claim 1; its specific features include the following preparation steps: select the initial alloy raw materials, melt the initial alloy raw materials according to the initial alloy composition ratio to obtain a uniform initial alloy melt; the main components of the initial alloy melt are La.sub.xFe.sub.yT.sub.zM.sub.aD.sub.b, where T includes at least one of Cr or V, M includes at least one of Al, Ni, Co, or Si, and D includes at least one of Mo, W, or Ti; x, y, z, a, and b represent atomic percentage contents of the corresponding element respectively, and 18%x95.8%, 4%y81.8%, 0.1%z35%, 0a40%, and 0b15%; solidify the initial alloy melt into an initial alloy solid using rapid solidification technology; the solidified structure of the initial alloy solid includes a matrix phase and a dispersed particle phase; the melting point of the matrix phase is lower than that of the dispersed particle phase, and the dispersed particle phase is encapsulated within the matrix phase; the volume percentage of the matrix phase in the solidified structure is not less than 40%; the average composition of the matrix phase mainly consists of La.sub.x1M.sub.a1; the composition of the dispersed particle phase mainly consists of Fe.sub.y2T.sub.z2M.sub.a2D.sub.b2La.sub.x2, where x1, al, x2, y2, z2, a2, and b2 represent the atomic percentage content of the corresponding constituent elements respectively, and 45%x1100%, 0%a155%, 50%y298%, 0.2%z2<50%, 0%a230%, 0%b235%, and 0<x25%; the dispersed particle phase includes a significant amount of spherical or near-spherical dispersed particles, with some spherical or near-spherical dispersed particles exhibiting certain dendritic features; the particle size of the dispersed particle phase ranges from 5 nm to 50 m.

17. The application of the spherical iron alloy powder material according to claim 4 in the field of magnetorheological fluids.

18. The application of the spherical iron alloy powder material in the field of magnetorheological fluids according to claim 17, including the following steps: mixing the spherical iron alloy powder with a carrier fluid and a surfactant to obtain a magnetorheological fluid; some characteristics of the spherical iron alloy powder material include: the main component of the spherical iron alloy powder material is Fe.sub.y2T.sub.z2M.sub.a2D.sub.b2La.sub.x2; where 50%y298%, 0.2%z2<50%, 0%a230%, 0%b235%, 0<x25%; 1%z2+b2<50%; the shape of the iron alloy powder particles is mainly spherical or near-spherical, with some spherical or near-spherical iron alloy powder particles exhibiting certain dendritic characteristics; the particle size of the iron alloy powder particles ranges from 5 nm to 100 nm; T includes at least one of Cr, V; M includes at least one of Al, Ni, Co, Si; D includes at least one of Mo, W, Ti; x2, y2, z2, a2, b2 represent the atomic percentage content of the corresponding constituent elements respectively.

19. A coronavirus-shaped spherical iron alloy powder particle, wherein the coronavirus-shaped spherical iron alloy powder particle includes the following features: the main component of the coronavirus-shaped spherical iron alloy powder particle is Fe.sub.y2T.sub.z2M.sub.a2D.sub.b2La.sub.x2, where 50%y298%, 0.2%z2<50%, 0%a230%, 0%b2<35%, 0<x25%; T includes at least one of Cr, V; M includes at least one of Al, Ni, Co, Si; D includes at least one of Mo, W, Ti; La is rare earth element La, and the coronavirus-like spherical iron alloy particle with the main component of Fe.sub.y2T.sub.z2M.sub.a2D.sub.b2La.sub.x2 contains La in a solid solution; x2, y2, z2, a2, b2 represent the atomic percentage content of the corresponding constituent elements respectively; the coronavirus-like spherical iron alloy powder particle include a main body part and a protruding part; the main body part is a spherical or nearly spherical sphere, and the protruding part consists of multiple protrusions grown in situ on the surface of the main body sphere; the spherical iron alloy powder particle has a coronavirus-like shape, where the multiple protrusions of the protruding part correspond to the multiple corona-like protrusions of a coronavirus; the diameter of the main body sphere of the coronavirus-like spherical iron alloy powder particle is 20 nm to 50 m, and the height of the protrusions on the protruding part is less than 0.3 times the diameter of the main body sphere.

20. The coronavirus-shaped spherical iron alloy powder particle according to claim 19, wherein the coronavirus-shaped spherical iron alloy powder particle is prepared by using the method according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0229] FIG. 1: Backscattered SEM morphology of the initial alloy solidification structure in Example 1;

[0230] FIG. 2: SEM morphology of the Fe alloy powder material prepared in Example 1;

[0231] FIG. 3: Backscattered SEM morphology of the initial alloy solidification structure in Example 2;

[0232] FIG. 4: Backscattered high-magnification SEM morphology of the matrix of the initial alloy solidification structure in Example 2;

[0233] FIG. 5: Backscattered SEM morphology of the initial alloy solidification structure in Example 3;

[0234] FIG. 6: Backscattered high-magnification SEM morphology of the matrix of the initial alloy solidification structure in Example 3;

[0235] FIG. 7: Backscattered SEM morphology of the initial alloy solidification structure in Example 4;

[0236] FIG. 8: Backscattered SEM morphology of the initial alloy solidification structure in Example 5;

[0237] FIG. 9: Backscattered SEM morphology of the initial alloy solidification structure in Example 6;

[0238] FIG. 10: Backscattered SEM morphology of the initial alloy solidification structure in Example 7;

[0239] FIG. 11: Backscattered SEM morphology of the initial alloy solidification structure in Example 8;

[0240] FIG. 12: SEM morphology of the Fe alloy powder material in Example 8;

[0241] FIG. 13: Backscattered SEM morphology of the initial alloy solidification structure in Example 10;

[0242] FIG. 14: Backscattered SEM morphology of the initial alloy solidification structure in Example 11;

[0243] FIG. 15: SEM morphology of the Fe alloy powder material in Example 11;

[0244] FIG. 16: Backscattered SEM morphology of the initial alloy solidification structure in Example 12;

[0245] FIG. 17: Backscattered SEM morphology of the initial alloy solidification structure in Example 13;

[0246] FIG. 18: SEM morphology of the Fe alloy powder material in Example 13;

[0247] FIG. 19: Backscattered SEM morphology of the initial alloy solidification structure in Example 14;

[0248] FIG. 20: Backscattered SEM morphology of the initial alloy solidification structure in Example 15;

[0249] FIG. 21: Backscattered SEM morphology of the initial alloy solidification structure in Example 16;

[0250] FIG. 22: SEM morphology of the Fe alloy powder material in Example 16;

[0251] FIG. 23: Backscattered SEM morphology of the initial alloy solidification structure in Comparative Example 1;

[0252] FIG. 24: SEM morphology of Fe-rich dendrites in Comparative Example 1;

[0253] FIG. 25: Backscattered SEM morphology of the initial alloy solidification structure in Comparative Example 2;

[0254] FIG. 26: Backscattered SEM morphology of the initial alloy solidification structure in Comparative Example 3;

[0255] FIG. 27: Backscattered SEM morphology of the initial alloy solidification structure in Comparative Example 4;

[0256] FIG. 28: High-magnification backscattered SEM morphology of the initial alloy solidification structure in Comparative Example 4.

DETAILED DESCRIPTION

[0257] The following examples further describe the invention in detail. It should be noted that the examples are provided to facilitate understanding of the invention and are not intended to limit its scope.

EXAMPLE 1

[0258] Using commercial La, Fe, and Cr materials, an initial alloy melt with a nominal atomic composition of La.sub.50Fe.sub.41Cr.sub.9 was prepared. The melt was solidified at a cooling rate of about 100 K/s into an initial alloy sheet with a thickness of approximately 5 mm. The solidification structure of the initial alloy sheet is shown in FIG. 1 and includes a dispersed particle phase primarily composed of Fe.sub.79Cr.sub.20La.sub.1 and a La-rich matrix phase, where the matrix phase volume fraction exceeds 65%. Both Cr and La are solid-solution in the dispersed particle phase. The dispersed particle phase includes spherical and dendritic particles, with spherical particles comprising more than 50% of the volume fraction. The particle size range of the spherical particles is 15 nm to 60 m.

[0259] The La matrix phase in the initial alloy sheet was removed by reaction with a 0.5 mol/L dilute hydrochloric acid solution, resulting in a dispersed Fe alloy powder material primarily composed of Fe.sub.79Cr.sub.20La.sub.1. This powder includes spherical and dendritic particles, with spherical particles constituting more than 50% of the volume fraction. The particle size range of the spherical particles is 15 nm to 60 m, as shown in FIG. 2. Some spherical or near-spherical particles have certain dendritic features, such as the small dendritic protrusions shown in the inset of FIG. 2. The prepared Fe alloy powder material is suitable for conventional powder metallurgy and metal injection molding (MIM) applications.

EXAMPLE 2

[0260] Using commercial La, Fe, and Cr materials, an initial alloy melt with a nominal atomic composition of La.sub.50Fe.sub.41Cr.sub.9 was prepared. The melt was solidified using a chill roll method at a cooling rate of about 5000 K/s into an initial alloy strip with a thickness of approximately 200 m. The solidification structure of the initial alloy strip is shown in FIG. 3 and includes a dispersed particle phase primarily composed of Fe.sub.77Cr.sub.22La.sub.1 and a La-rich matrix phase, where the matrix phase volume fraction exceeds 65%. The dispersed particle phase is almost entirely composed of spherical particles. Some spherical particles contain certain dendritic features, such as the small dendritic protrusions shown in the inset of FIG. 3. The particle size range of the spherical particles is 15 nm to 10 m. The matrix phase in FIG. 3 was magnified, revealing some nanometer-sized spherical particles, as shown in FIG. 4.

[0261] Using a 0.5 mol/L dilute sulfuric acid solution, the La matrix phase in the initial alloy strip was reacted and removed. This resulted in a dispersed Fe alloy powder material primarily composed of Fe.sub.77Cr.sub.22La.sub.1, which consists almost entirely of spherical particles, with some spherical particles exhibiting certain dendritic features. The particle size range of the spherical particles is 15 nm to 10 m. The prepared powder material is suitable for conventional powder metallurgy and metal injection molding (MIM) applications.

EXAMPLE 3

[0262] Using commercial La, Fe, and V materials, an initial alloy melt with a nominal atomic composition of La.sub.67Fe.sub.30V.sub.3 was prepared. The melt was solidified at a cooling rate of about 1000 K/s into an initial alloy strip with a thickness of approximately 500 m. The solidification structure of the initial alloy strip is shown in FIG. 5 and includes a dispersed particle phase primarily composed of Fe.sub.88.5V.sub.9La.sub.1.5 and a La-rich matrix phase, where the matrix phase volume fraction exceeds 70%. The dispersed particle phase is primarily spherical, with a particle size range of 15 nm to 5 m. Enlarging the matrix phase in FIG. 5 reveals some nanometer-sized spherical particles, as shown in FIG. 6 (with the matrix phase outside the nanometer-sized spherical particles). A small amount of the dispersed particles are dendritic.

[0263] The La matrix phase in the initial alloy strip was removed by reaction with a 0.5 mol/L dilute hydrochloric acid solution. This resulted in a dispersed Fe alloy powder material primarily composed of Fe.sub.88.5V.sub.9La.sub.1.5, with a shape mainly of spherical particles and only a small amount of dendritic particles. The particle size range of the spherical particles is 15 nm to 5 m.

EXAMPLE 4

[0264] Using commercial low-purity La, low-purity Fe, low-purity V, and low-purity Cr materials with high oxygen impurity, an initial alloy melt with a nominal atomic composition of La.sub.67Fe.sub.30Cr.sub.3V.sub.3 was prepared. The initial alloy melt, with a composition approximately La.sub.65Fe.sub.30Cr.sub.3V.sub.3O.sub.2, was solidified at a cooling rate of about 250 K/s into an initial alloy thick strip with a thickness of approximately 3 mm. The solidification structure of the initial alloy thick strip is shown in FIG. 7 and includes a dispersed particle phase primarily composed of Fe.sub.82.3V.sub.8Cr.sub.8La.sub.1.5O.sub.0.2 and a La-rich matrix phase enriched with oxygen impurities, where the matrix phase volume fraction exceeds 70%. The dispersed particle phase is primarily spherical, with a small amount of dendritic particles. The particle size range of the spherical particles is 15 nm to 15 m, and some spherical particles have certain dendritic features.

[0265] The La-rich matrix phase in the initial alloy thick strip was removed by reaction with a 0.2 mol/L dilute nitric acid solution. This resulted in a dispersed Fe alloy powder material primarily composed of Fe.sub.82.3V.sub.8Cr.sub.8La.sub.1.5O.sub.0.2, with a shape mainly of spherical particles and a small amount of dendritic particles. Some spherical particles exhibit certain dendritic features. The particle size range of the spherical particles is 15 nm to 15 m.

EXAMPLE 5

[0266] Using commercial La, Fe, Cr, and Mo materials, an initial alloy melt with a nominal atomic composition of La.sub.50Fe.sub.40Cr.sub.0.5Mo.sub.9.5 was prepared. The initial alloy melt was solidified at a cooling rate of about 250 K/s into an initial alloy thick strip with a thickness of approximately 3 mm. The solidification structure of the initial alloy thick strip is shown in FIG. 8 and includes a dispersed particle phase primarily composed of Fe.sub.78Mo.sub.20Cr.sub.1La.sub.1 and a La-rich matrix phase, where the matrix phase volume fraction exceeds 70%. The dispersed particle phase is primarily spherical, with a particle size range of 15 nm to 15 m, and some spherical particles have certain dendritic features.

[0267] The La matrix phase in the initial alloy thick strip was removed by reaction with a 0.5 mol/L dilute hydrochloric acid solution. This resulted in a dispersed Fe alloy powder material primarily composed of Fe.sub.78Mo.sub.20Cr.sub.1La.sub.1, with a shape mainly of spherical particles, and some spherical particles exhibiting certain dendritic features. The particle size range of the spherical particles is 15 nm to 15 m.

EXAMPLE 6

[0268] Using commercial La, Fe, Cr, and Si materials, an initial alloy melt with a nominal atomic composition of La.sub.34Fe.sub.40Cr.sub.2.5Si.sub.23.5 was prepared. The melt was solidified at a cooling rate of about 100 K/s into an initial alloy thick strip with a thickness of approximately 5 mm. The solidification structure of the initial alloy thick strip is shown in FIG. 9 and includes a black dispersed particle phase primarily composed of Fe.sub.85.2Cr.sub.8Si.sub.6La.sub.0.8, a white matrix phase primarily composed of La.sub.64Si.sub.36, and a gray matrix phase primarily composed of La.sub.34Si.sub.33Fe.sub.33, where the volume fraction of the two matrix phases exceeds 70%. The dispersed particle phase is mainly near-spherical, with a particle size range of 50 nm to 5 m.

[0269] The La.sub.64Si.sub.36 and La.sub.34Si.sub.33Fe.sub.33 matrix phases in the initial alloy thick strip were removed by reaction with a mixed solution of 0.5 mol/L dilute hydrochloric acid and 1 mol/L hydrofluoric acid. This resulted in a dispersed Fe.sub.85.2Cr.sub.8Si.sub.6La.sub.0.8 alloy powder material with a shape primarily of near-spherical particles, and the particle size range is 50 nm to 5 m. The prepared powder material can be used in the field of magnetic materials, such as magnetic powder cores.

EXAMPLE 7

[0270] Using commercial La, Fe, Cr, and Si materials, an initial alloy melt with a nominal atomic composition of La.sub.34Fe.sub.40Cr.sub.2.5Si.sub.23.5 was prepared. The melt was solidified at a cooling rate of about 10.sup.5 K/s into an initial alloy strip with a thickness of approximately 100 m. The solidification structure of the initial alloy strip is shown in FIG. 10 and includes a black dispersed particle phase primarily composed of Fe.sub.82.5Cr.sub.8Si.sub.8La.sub.1.5 and a matrix phase with an average composition of La.sub.60Si.sub.20Fe.sub.20, where the matrix phase volume fraction is greater than 70%. The dispersed particle phase is mainly fine spherical particles, with a particle size range of 15 nm to 2 m.

[0271] The matrix phase with an average composition of La.sub.60Si.sub.20Fe.sub.20 in the initial alloy strip was removed by reaction with a mixed solution of 0.5 mol/L dilute hydrochloric acid and 1 mol/L hydrofluoric acid. This resulted in a dispersed Fe.sub.82.5Cr.sub.8Si.sub.8La.sub.1.5, containing Si alloy powder material with a shape primarily of near-spherical particles, and the particle size range is 15 nm to 2 m. The prepared powder material can be used in the field of magnetic materials, such as magnetic powder cores.

EXAMPLE 8

[0272] Using commercial La, Fe, Cr, and Si materials, an initial alloy melt with a nominal atomic composition of La.sub.50Fe.sub.40Cr.sub.5Si.sub.5 was prepared. The melt was solidified at a cooling rate of about 250 K/s into an initial alloy thick strip with a thickness of approximately 3 mm. The solidification structure of the initial alloy thick strip is shown in FIG. 11 and includes a dispersed particle phase primarily composed of Fe.sub.86Cr.sub.12Si.sub.1La.sub.1 and a matrix phase primarily composed of La.sub.92Si.sub.8, where the matrix phase volume fraction exceeds 70%. The dispersed particle phase is mainly spherical, with a small amount of dendritic particles, and some spherical particles have certain dendritic features. The particle size range of the spherical particles is 15 nm to 40 m.

[0273] The LaSi matrix phase in the initial alloy thick strip was removed by reaction with a mixed solution of 0.5 mol/L dilute hydrochloric acid, 0.1 mol/L dilute nitric acid, and 0.5 mol/L hydrofluoric acid (HF can remove Si). This resulted in a dispersed Fe.sub.86Cr.sub.12Si.sub.1La.sub.1 alloy powder material with a shape primarily of spherical particles and a small amount of dendritic particles, with some spherical particles exhibiting certain dendritic features. The particle size range of the spherical particles is 15 nm to 40 m, as shown in FIG. 12.

EXAMPLE 9

[0274] Using commercial La, Fe, Cr, and Si materials, an initial alloy melt with a nominal atomic composition of La.sub.50Fe.sub.41Cr.sub.4Si.sub.5 was prepared. The melt was solidified at a cooling rate of about 1000 K/s into an initial alloy strip with a thickness of approximately 500 m. The solidification structure of the initial alloy strip includes a dispersed particle phase primarily composed of Fe.sub.90.5Cr.sub.8Si.sub.0.5La.sub.1 and a matrix phase primarily composed of La.sub.94Si.sub.6, where the matrix phase volume fraction exceeds 70%. The dispersed particle phase is mainly spherical, with a small amount of dendritic particles, and some spherical particles exhibit certain dendritic features. The particle size range of the spherical particles is 15 nm to 10 m.

[0275] The LaSi matrix phase in the initial alloy strip was removed by reaction with 0.5 mol/L dilute hydrochloric acid, while retaining most of the Si (Si generally does not react with dilute hydrochloric acid), resulting in a composite powder of Fe.sub.90.5Cr.sub.8Si.sub.0.5La.sub.1 alloy and nano-porous Si. The nano-porous Si has a fragmented porous structure, and the iron alloy powder is mainly spherical, with a small amount of dendritic particles, and some spherical particles exhibit certain dendritic features. The particle size range of the spherical particles is 15 nm to 10 m.

[0276] The spherical iron alloy powder and nano-porous Si composite powder were pressed and densified, then solid siliconized in a vacuum at 1000 C. for 4 hours, followed by powder dispersion. This resulted in a high-silicon content iron-chromium-silicon powder with a composition of approximately Fe.sub.82Cr.sub.7Si.sub.10La.sub.1.

[0277] The high-silicon content iron-chromium-silicon powder, after screening, selects particles with a size range of 3 m to 10 m, which can be used in the field of soft magnetic materials, such as magnetic powder cores.

EXAMPLE 10

[0278] Using commercial La, Fe, Cr, and Al materials, an initial alloy melt with a nominal atomic composition of La.sub.45Fe.sub.27.5Cr.sub.7.5Al.sub.20 was prepared. The melt was solidified at a cooling rate of about 250 K/s into an initial alloy thick strip with a thickness of approximately 3 mm. The solidification structure of the initial alloy thick strip is shown in FIG. 13 and includes a dispersed particle phase primarily composed of Fe.sub.72Cr.sub.20Al.sub.7La.sub.1 and a matrix phase primarily composed of La.sub.75Al.sub.25, where the volume fraction of the matrix phase exceeds 70%. The dispersed particle phase is mainly spherical, with a small amount of dendritic particles, and some spherical particles exhibit certain dendritic features. The particle size range of the spherical particles is 15 nm to 10 m.

[0279] The La.sub.75Al.sub.25 matrix phase in the initial alloy thick strip was removed by reaction with 0.5 mol/L dilute hydrochloric acid, resulting in a dispersed Fe.sub.72Cr.sub.20Al.sub.7La.sub.1 alloy powder material. The shape is primarily spherical particles, with a small amount of dendritic particles, and some spherical particles exhibit certain dendritic features. The particle size range is 15 nm to 10 m. The prepared powder material can be used in fields such as electrical heating alloys, heat-resistant alloys, and heat-resistant coatings.

EXAMPLE 11

[0280] Using commercial La, Fe, Cr, and Al materials, an initial alloy melt with a nominal atomic composition of La.sub.45Fe.sub.27.5Cr.sub.7.5Al.sub.20 was prepared. The melt was solidified at a cooling rate of about 10.sup.4 K/s into an initial alloy thin strip with a thickness of approximately 150 m. The solidification structure of the initial alloy thin strip is shown in FIG. 14 and includes a dispersed particle phase primarily composed of Fe.sub.71Cr.sub.21Al.sub.7La.sub.1 and a matrix phase primarily composed of La.sub.75Al.sub.25, where the volume fraction of the matrix phase exceeds 70%. The dispersed particle phase is almost entirely spherical, with some spherical particles exhibiting certain dendritic features. The particle size range of the spherical particles is 5 nm to 5 m.

[0281] The La.sub.75Al.sub.25 matrix phase in the initial alloy thin strip was removed by reaction with 0.5 mol/L dilute hydrochloric acid, resulting in a dispersed Fe.sub.71Cr.sub.21Al.sub.7La.sub.1 alloy powder material. The shape is almost entirely spherical, with some spherical particles exhibiting certain dendritic features, as shown in FIG. 15. The particle size range is 5 nm to 5 m. The prepared powder material can be used in fields such as electrical heating alloys, heat-resistant alloys, and heat-resistant coatings.

EXAMPLE 12

[0282] Using commercial La, Fe, Cr, Al, and Mo materials, an initial alloy melt with a nominal atomic composition of La.sub.38Fe.sub.25Cr.sub.10Al.sub.25Mo.sub.2 was prepared. The melt was solidified at a cooling rate of about 500 K/s into an initial alloy thick strip with a thickness of approximately 1 mm. The solidification structure of the initial alloy thick strip is shown in FIG. 16 and includes a dispersed particle phase primarily composed of Fe.sub.60Cr.sub.25Al.sub.8Mo.sub.6La.sub.1 and matrix phases primarily composed of La.sub.50Al.sub.50 (gray plate-like and fibrous phases) and La.sub.75Al.sub.25 (white phase), where the overall volume fraction of the matrix phases exceeds 70%. The dispersed particle phase is mainly spherical, with a small amount of dendritic particles, and some spherical particles exhibit certain dendritic features. The particle size range of the spherical particles is 15 nm to 40 m.

[0283] The La.sub.50Al.sub.50 and La.sub.75Al.sub.25 matrix phases in the initial alloy thick strip were removed by reaction with 1 mol/L dilute hydrochloric acid, resulting in a dispersed Fe.sub.60Cr.sub.25Al.sub.8Mo.sub.6La.sub.1 alloy powder material. The shape is primarily spherical particles, with a small amount of dendritic particles, and some spherical particles exhibit certain dendritic features. The particle size range is 15 nm to 40 m. The prepared powder material can be used in fields such as electrical heating alloys, heat-resistant alloys, and heat-resistant coatings. Due to the presence of Mo, the powder material has higher temperature resistance and corrosion resistance.

EXAMPLE 13

[0284] Using commercial La, Fe, Cr, and Co materials, an initial alloy melt with a nominal atomic composition of La.sub.27.5Fe.sub.37.5Cr.sub.10Co.sub.25 was prepared. The melt was solidified at a cooling rate of about 250 K/s into an initial alloy thick strip with a thickness of approximately 3 mm. The solidification structure of the initial alloy thick strip is shown in FIG. 17 and includes a dispersed particle phase primarily composed of Fe.sub.63Cr.sub.19Co.sub.17La.sub.1 and a matrix phase primarily composed of La.sub.60Co.sub.40, where the overall volume fraction of the matrix phase exceeds 50%. The dispersed particle phase is almost entirely spherical, with only a small amount of dendritic particles, and some spherical particles exhibit certain dendritic features. The particle size range of the spherical particles is 15 nm to 6 m.

[0285] The La.sub.60Co.sub.40 matrix phase in the initial alloy thick strip was removed by reaction with 1 mol/L dilute hydrochloric acid, resulting in a dispersed Fe.sub.63Cr.sub.19Co.sub.17La.sub.1 alloy powder material, as shown in FIG. 18. The shape is primarily spherical particles, with a small amount of dendritic particles, and some spherical particles exhibit certain dendritic features. The particle size range is 15 nm to 6 m. The prepared powder material can be used in the field of magnetic materials.

EXAMPLE 14

[0286] Using commercial La, Fe, Cr, and Ni materials, an initial alloy melt with a nominal atomic composition of La.sub.27.5Fe.sub.37.5Cr.sub.10Ni.sub.25 was prepared. The melt was solidified at a cooling rate of about 250 K/s into an initial alloy thick strip with a thickness of approximately 3 mm. The solidification structure of the initial alloy thick strip is shown in FIG. 19 and includes a dispersed particle phase primarily composed of Fe.sub.70Cr.sub.20Ni.sub.9La.sub.1 and matrix phases primarily composed of La.sub.50Ni.sub.50 and La.sub.75Ni.sub.25, where the overall volume fraction of the matrix phases exceeds 50%. The dispersed particle phase is mainly spherical, with a small amount of dendritic particles, and some spherical particles exhibit certain dendritic features. The particle size range of the spherical particles is 15 nm to 50 m.

[0287] The La.sub.50Ni.sub.50 and La.sub.75Ni.sub.25 matrix phases in the initial alloy thick strip were removed by reaction with 1 mol/L dilute hydrochloric acid, resulting in a dispersed Fe.sub.70Cr.sub.20Ni.sub.9La.sub.1 alloy powder material. The shape is primarily spherical particles, with a small amount of dendritic particles, and some spherical particles exhibit certain dendritic features. The particle size range is 15 nm to 50 m.

EXAMPLE 15

[0288] Using commercial La, Fe, Cr, Ni, Mo, and Ti materials, an initial alloy melt with a nominal atomic composition of La.sub.35Fe.sub.36Cr.sub.10Ni.sub.15Mo.sub.1Ti.sub.2 was prepared. The melt was solidified at a cooling rate of about 50 K/s into a button ingot with a thickness of 6 mm and a diameter of 12 mm. The solidification structure of the initial alloy button ingot is shown in FIG. 20 and includes a dispersed particle phase primarily composed of Fe.sub.70Cr.sub.20Ni.sub.3Mo.sub.2Ti.sub.4La.sub.1 and matrix phases primarily composed of La.sub.81Ni.sub.19 (including La and La.sub.3Ni phases), where the overall volume fraction of the matrix phases exceeds 70%. The dispersed particle phase is almost entirely spherical, with only a small amount of dendritic particles, and some spherical particles exhibit certain dendritic features. The particle size range of the spherical particles is 15 nm to 50 m.

[0289] The La.sub.81Ni.sub.19 matrix phase in the initial alloy button ingot was removed by reaction with 1 mol/L hydrochloric acid, while retaining the corrosion-resistant dispersed particle phase, resulting in a dispersed Fe.sub.70Cr.sub.20Ni.sub.3Mo.sub.2Ti.sub.4La.sub.1 spherical iron alloy powder material. The iron alloy powder material is primarily spherical particles, with a small amount of dendritic particles, and some spherical particles exhibit certain dendritic features. The particle size range is 15 nm to 50 m.

EXAMPLE 16

[0290] Using commercial La, Fe, Cr, and Ni materials, an initial alloy melt with a nominal atomic composition of La.sub.27.5Fe.sub.37.5Cr.sub.10Ni.sub.25 was prepared. The melt was solidified at a cooling rate of about 5000 K/s into an initial alloy strip with a thickness of approximately 200 m. The solidification structure of the initial alloy strip is shown in FIG. 21 and includes a dispersed particle phase primarily composed of Fe.sub.70Cr.sub.20Ni.sub.9La.sub.1 and a matrix phase primarily composed of La.sub.60Ni.sub.40, where the overall volume fraction of the matrix phase exceeds 50%. The dispersed particle phase is almost entirely spherical, with only a small amount of dendritic particles, and some spherical particles exhibit certain dendritic features. The particle size range of the spherical particles is 15 nm to 6 m.

[0291] By using 0.2 mol/L dilute hydrochloric acid to remove La from the matrix phase of the initial alloy strip through a de-alloying reaction, while retaining some nanoporous Ni, a composite powder consisting of spherical Fe.sub.70Cr.sub.20Ni.sub.9La.sub.1 alloy powder and nanoporous Ni is obtained, as shown in FIG. 22. The fluffy material on the surface of the spherical particles is nanoporous Ni. The iron alloy powder is primarily spherical particles, with a small amount of dendritic particles, and some spherical particles exhibit certain dendritic features. The particle size range of the spherical particles is 15 nm to 6 m.

[0292] The spherical Fe.sub.70Cr.sub.20Ni.sub.9La.sub.1 alloy powder and nanoporous Ni composite powder are pressed into billets at 100 MPa, followed by heat treatment at 1300 C. for 4 hours in a protective atmosphere, resulting in a high-nickel iron-chromium-nickel high-temperature alloy product with a composition of approximately Fe.sub.52Cr.sub.15Ni.sub.33La.sub.1.

EXAMPLE 17

[0293] Using commercial La, Fe, and Cr materials, an initial alloy melt with a nominal atomic composition of La.sub.45Fe.sub.40Cr.sub.15 was prepared. The melt was solidified at a cooling rate of about 10.sup.6 to 10.sup.7 K/s into an initial alloy strip with a thickness of approximately 20 m. The solidification structure of the initial alloy strip includes a Fe-rich dispersed nanoparticle phase (too small for direct composition detection) and a matrix phase primarily composed of La, with the matrix phase having a volume percentage content exceeding 60%. The dispersed particle phase is almost entirely nanospherical, with some spherical particles exhibiting dendritic features. The particle size range of the spherical particles is 5 nm to 200 nm.

[0294] The La matrix phase in the initial alloy strip was removed by reaction with 0.5 mol/L dilute hydrochloric acid, resulting in a dispersed nano iron alloy powder material with a primary composition of Fe.sub.71Cr.sub.27La.sub.2 (due to the presence of Cr, making the Fe.sub.71Cr.sub.27La.sub.2 nanoparticles less susceptible to acid dissolution). The material is almost entirely spherical particles, with some spherical particles exhibiting dendritic features. The particle size range of the nano iron alloy powder is 5 nm to 200 nm.

EXAMPLE 18

[0295] Using commercial La, Fe, and Cr materials, an initial alloy melt with a nominal atomic composition of La.sub.50Fe.sub.46Cr.sub.4 was prepared. The melt was solidified at a cooling rate of about 10.sup.4 K/s into an initial alloy strip with a thickness of approximately 150 m. The solidification structure of the initial alloy strip includes a dispersed particle phase primarily composed of Fe.sub.91Cr.sub.8La.sub.1 and a matrix phase primarily composed of La. Cr and La are solid-solutioned in the Fe-rich dispersed particles. The Fe-rich dispersed particles are mainly spherical, with a small amount of dendritic particles, and some spherical particles exhibit dendritic features. The particle size range of the Fe-rich spherical particles is 15 nm to 10 m.

[0296] The La matrix phase in the initial alloy strip was removed by reaction with 0.5 mol/L dilute hydrochloric acid, resulting in a dispersed iron alloy powder material with a primary composition of Fe.sub.91Cr.sub.8La.sub.1. The powder includes spherical and dendritic particles, with a predominance of spherical particles, and some spherical particles exhibit dendritic features. The particle size range of the spherical particles is 15 nm to 10 m.

[0297] The obtained iron alloy powder material was subjected to silicon infiltration treatment in a gas mixture of silicon chloride (SiCl.sub.4, or Si.sub.2Cl.sub.6, or a mixture of SiCl.sub.4 and Si.sub.2Cl.sub.6) and hydrogen, at a treatment temperature of 400 C. to 1000 C. This resulted in a high-silicon-content spherical iron alloy powder material with a composition of approximately Fe.sub.81.5Cr.sub.7Si.sub.10.5La.sub.1. The shape remains largely unchanged from before silicon infiltration, including spherical and dendritic particles, with a predominance of spherical particles and some spherical particles exhibiting dendritic features. The particle size range of the spherical particles is 15 nm to 10 m.

[0298] After screening, Fe.sub.81.5Cr.sub.7Si.sub.10.5La.sub.1 powders with particle sizes ranging from 1 m to 10 m are selected for insulation coating, and then magnetic powder cores are prepared.

EXAMPLE 19

[0299] Using commercial La, Fe, and Cr materials, an initial alloy melt with a nominal atomic composition of La.sub.35Fe.sub.50Cr.sub.15 was prepared. By using atomization powder technology, the melt was atomized at a cooling rate of approximately 10.sup.3 to 10.sup.6 K/s into initial alloy powders with sizes ranging from 5 m to 300 m. The solidification structure of the initial alloy powder includes a dispersed particle phase primarily composed of Fe.sub.75.5Cr.sub.23La.sub.1.5 and a matrix phase primarily composed of La, with the matrix phase having a volume percentage content exceeding 50%. The dispersed particle phase is almost entirely spherical, with some spherical particles exhibiting dendritic features. The particle size range of the spherical particles is 5 nm to 10 m.

[0300] The La matrix phase in the initial alloy powder was removed by reaction with 0.5 mol/L dilute hydrochloric acid, resulting in a finer iron alloy powder material with a primary composition of Fe.sub.75.5Cr.sub.23La.sub.1.5. The material is almost entirely spherical particles, with some spherical particles exhibiting dendritic features. The particle size range of the spherical particles is 5 nm to 10 m. The prepared powder material can be used in conventional powder metallurgy and metal injection molding (MIM) applications.

EXAMPLE 20

[0301] Using commercial La, Fe, Mo, and Cr materials, an initial alloy melt with a nominal atomic composition of La.sub.50Fe.sub.49Cr.sub.0.5Mo.sub.0.5 was prepared. The melt was solidified at a cooling rate of about 10.sup.7 to 10.sup.8 K/s into an initial alloy strip with a thickness of approximately 15 m to 20 m. The solidification structure of the initial alloy strip includes a Fe-rich dispersed nanoparticle phase and a matrix phase primarily composed of La, with the matrix phase having a volume percentage content exceeding 65%. The dispersed particle phase is almost entirely nanospherical, with some spherical particles exhibiting certain dendritic features. The particle size range of the spherical particles is 5 nm to 100 nm.

[0302] The La matrix phase in the initial alloy strip was removed by reaction with 0.25 mol/L dilute hydrochloric acid, resulting in a dispersed nano iron alloy powder material with a primary composition of Fe.sub.97Cr.sub.1Mo.sub.1La.sub.1 (due to the presence of Cr and Mo, making the Fe.sub.97Cr.sub.1Mo.sub.1La.sub.1 nano iron alloy powder particles less susceptible to dissolution by 0.25 mol/L dilute hydrochloric acid). The material is almost entirely spherical particles, with some spherical particles exhibiting dendritic features. The particle size range of the nano Fe.sub.97Cr.sub.1Mo.sub.1La.sub.1 iron alloy powder particles is 5 nm to 100 nm.

[0303] The obtained nano Fe.sub.97Cr.sub.1Mo.sub.1La.sub.1 iron alloy powder particles were used as magnetic solid particles, and a magnetic fluid was prepared using sodium dodecyl sulfate (SDS) and oleic acid as surfactants, with ethanol as the carrier liquid.

EXAMPLE 21

[0304] Using commercial La, Fe, and Cr materials, an initial alloy melt with a nominal atomic composition of La.sub.50Fe.sub.47Cr.sub.3 was prepared. The melt was solidified at a cooling rate of about 10.sup.6 to 10.sup.8 K/s into an initial alloy strip with a thickness of approximately 15 m to 20 m. The solidification structure of the initial alloy strip includes a Fe-rich dispersed nanoparticle phase and a matrix phase primarily composed of La, with the matrix phase having a volume percentage content exceeding 65%. The dispersed particle phase is almost entirely nanospherical, with some spherical particles exhibiting certain dendritic features. The particle size range of the spherical particles is 5 nm to 50 nm.

[0305] The La matrix phase in the initial alloy strip was removed by reaction with 0.5 mol/L dilute hydrochloric acid, resulting in a dispersed nano iron alloy powder material with a primary composition of Fe.sub.93Cr.sub.6La.sub.1 (due to the presence of Cr, making the Fe.sub.93Cr.sub.6La.sub.1 nano iron alloy powder particles less susceptible to dissolution by 0.5 mol/L dilute hydrochloric acid). The material is almost entirely spherical particles, with some spherical particles exhibiting dendritic features. The particle size range of the nano Fe.sub.93Cr.sub.6La.sub.1 iron alloy powder particles is 5 nm to 50 nm.

[0306] The obtained nano Fe.sub.93Cr.sub.6La.sub.1 iron alloy powder particles were used as magnetic solid particles, and a magnetic fluid was prepared using mercury as the carrier liquid.

COMPARATIVE EXAMPLE 1

[0307] Using commercial La and Fe materials, an initial alloy melt with a nominal atomic composition of La.sub.50Fe.sub.50 was prepared. The melt was solidified at a cooling rate of about 250 K/s into an initial alloy strip with a thickness of approximately 3 mm. The solidification structure of the initial alloy strip, as shown in FIG. 23, includes a dispersed dendritic phase primarily composed of Fe.sub.99La.sub.1 and a matrix phase primarily composed of La, with the matrix phase having a volume percentage content exceeding 70%. The dispersed dendritic phase is almost entirely dendritic. The parts that appear to be spherical in FIG. 23 are actually cross-sectional views of dendritic branches, with each row of cross-sectional branches belonging to a larger dendrite.

[0308] The La matrix phase in the initial alloy strip was removed by reaction with 0.5 mol/L dilute hydrochloric acid, resulting in a dispersed iron alloy dendritic powder material with a primary composition of Fe.sub.99La.sub.1. The material is predominantly dendritic, with no spherical particles, as shown in FIG. 24. It also clearly shows that a large dendrite will have rows of secondary dendrites, and the cross-sectional view of these secondary dendrites corresponds to the spheres shown in FIG. 23 (actually rod-shaped cross-sections). Therefore, La.sub.50Fe.sub.50 alloy can only produce large Fe-rich dendritic particles with very well-developed growth at a slow cooling rate and cannot produce Fe-rich spherical particles.

COMPARATIVE EXAMPLE 2

[0309] Using commercial La and Fe materials, an initial alloy melt with a nominal atomic composition of La.sub.50Fe.sub.50 was prepared. The melt was solidified at a cooling rate of about 10.sup.5 K/s into an initial alloy strip with a thickness of approximately 100 m. The solidification structure of the initial alloy strip, as shown in FIG. 25, includes a dispersed dendritic phase primarily composed of Fe.sub.99La.sub.1 and a matrix phase primarily composed of La. The dispersed dendritic phase is almost entirely dendritic. The multiple seemingly short rod-shaped Fe-rich black phases in FIG. 25 actually belong to one or several dendrites, with these dendrites having sizes of about 1-2 m. Due to the nanoscale secondary structure of the dendrites and the susceptibility of Fe.sub.99La.sub.1 to acid corrosion, when acid corrosion is used, the nanoscale Fe-rich dendrites will also be reacted and corroded, making it difficult to obtain the original Fe-rich particles. Therefore, even with a very high cooling rate, when the initial alloy melt does not contain T or D type elements, it is difficult to obtain spherical Fe-rich particle phases and to improve the corrosion resistance of Fe-rich particles, making them prone to acid reaction separation.

COMPARATIVE EXAMPLE 3

[0310] Using commercial La, Fe, and Hf materials, an initial alloy melt with a nominal atomic composition of La.sub.50Fe.sub.40Hf.sub.10 was prepared. The melt was solidified at a cooling rate of about 500 K/s into an initial alloy strip with a thickness of approximately 1 mm. The solidification structure of the initial alloy strip, as shown in FIG. 26, includes a black dispersed dendritic phase with a primary composition of approximately Fe.sub.99La.sub.1, a white dispersed dendritic phase with a primary composition of approximately Fe.sub.64Hf.sub.35La.sub.1, and a matrix phase primarily composed of La. Thus, Hf in the initial alloy melt cannot solidify into the Fe-rich phase during the solidification process and only precipitates as Fe.sub.2Hf intermetallic compounds. The Fe-rich phase is primarily still precipitated as the Fe.sub.99La.sub.1 dispersed dendritic phase. Neither dendritic phase results in spherical particle phases. Therefore, adding Hf to LaFe alloys does not yield spherical Fe-rich particle phases.

COMPARATIVE EXAMPLE 4

[0311] Using commercial La, Fe, and Ta materials, an initial alloy melt with a nominal atomic composition of La.sub.50Fe.sub.40Ta.sub.10 was prepared. The melt was solidified at a cooling rate of about 500 K/s into an initial alloy strip with a thickness of approximately 1 mm. The solidification structure of the initial alloy strip, as shown in FIG. 27, includes a black dispersed dendritic phase with a primary composition of approximately Fe.sub.99La.sub.1, a white flocculent dendritic phase with a primary composition of approximately Fe.sub.69Ta.sub.30La.sub.1 (as indicated by the arrow in FIG. 28, which is Fe.sub.7Ta.sub.3 intermetallic compound), and a matrix phase primarily composed of La. Thus, Ta in the initial alloy melt cannot solidify into the Fe-rich phase during the solidification process and only precipitates as Fe.sub.7Ta.sub.3 intermetallic compounds. The Fe-rich phase is primarily still precipitated as the Fe.sub.99La.sub.1 dispersed dendritic phase. Neither dendritic phase results in spherical particle phases. Therefore, adding Ta to LaFe alloys does not yield spherical Fe-rich particle phases.

[0312] The technical features of the examples described above can be combined in any way. For the sake of simplicity, not all possible combinations of technical features in the above examples have been described, but any combination that does not contradict the technical features should be considered within the scope of this disclosure.

[0313] The examples described above are only a few embodiments of the invention. They are described in detail, but this does not imply a limitation on the scope of the invention. It should be noted that those skilled in the art may make various modifications and improvements without departing from the inventive concept, and these are within the scope of the invention. Therefore. the scope of protection of this patent should be determined by the appended claims.