A heat treatment method for improving the performance of additive manufacturing Fe-Ga alloy, product and application

Abstract

This invention belongs to the field of metal additive manufacturing heat treatment technology, and discloses a heat treatment method, product, and application for improving the performance of additively manufactured Fe-Ga alloys. The method includes: solution treatment, holding the laser-additively manufactured Fe-Ga alloy at 700–850℃ for 0.5–3 hours under argon protection; brine cooling, directly immersing the solution-treated Fe-Ga alloy in room-temperature brine to cool to room temperature; aging treatment, holding the brine-cooled Fe-Ga alloy at 280–320℃ for 1–12 hours; and water cooling treatment, water cooling the aged Fe-Ga alloy to room temperature. <100> The area of ​​BD texture should account for no less than 75%; this method retains strong texture. <100> Simultaneously with texturing, precipitation was suppressed by brine cooling, and combined with aging treatment to obtain a size of 5–10 nm and a number density ≥3.0 × 10⁻⁶. 10 mm ‑2 The L60 precipitate phase reduces the alloy's saturation magnetostriction coefficient λ. s The concentration reaches 290 ppm or higher. This application also provides Fe-Ga alloy products obtained by this method and their applications in magnetostrictive sensors or microactuators.

Description

Technical Field

[0001] This invention relates to the field of heat treatment technology for metal additive manufacturing, and in particular to a heat treatment method, product, and application for improving the performance of Fe-Ga alloys in additive manufacturing. Background Technology

[0002] Fe-Ga alloys, as a novel magnetostrictive material, show great promise for applications in sensors, actuators, and other fields. Research indicates that the magnetostrictive properties of Fe-Ga alloys mainly depend on two microstructural factors: along the easy magnetization direction... <100> The strong crystallographic texture and nanoscale L60 precipitates are key to achieving high magnetostrictive properties. The L60 phase, a metastable face-centered tetragonal structure, significantly enhances magnetoelastic coupling by inducing localized tetragonal distortion within the A2 matrix, thus being crucial for high magnetostrictive performance. However, the formation of the L60 phase is a diffusion-controlled kinetic process, and its size, quantity, and distribution are extremely sensitive to thermal history: slow cooling or inappropriate aging temperatures can easily lead to coarsening or transformation into the harmful DO3 phase or even the equilibrium L12 phase, resulting in a sharp decline in magnetostrictive properties. Therefore, to obtain high magnetostrictive performance, it is essential to retain the strong crystallographic texture and nanoscale L60 precipitates. <100> Under the premise of texture, the L60 phase is adjusted to an ideal state of fine, high density and uniform distribution.

[0003] Laser Powder Bed Fusion (LPBF) technology, utilizing high temperature gradients and rapid solidification, can produce strong powder powder in a single step. <100> Fe-Ga alloy components with textured structure and in-situ precipitation of L60 phase were produced. However, the microstructure exhibits high dislocation density, large residual stress, and uneven distribution of the L60 phase, requiring further control through subsequent heat treatment. Existing heat treatment methods present a significant contradiction: while high-temperature annealing can eliminate stress, it can induce recrystallization, leading to… <100> The textural degradation leads to the solidification of the L60 phase; however, the conventional cooling rate after solidification is insufficient, resulting in uncontrollable pre-precipitation of L60 and DO3 during cooling, which consumes matrix solutes and vacancies, thus reducing the driving force for subsequent aging nucleation and making it impossible to obtain a high-density, uniformly distributed L60 phase. Therefore, a method that can simultaneously address these issues is urgently needed. <100> A heat treatment method that preserves texture, releases residual stress, and precisely controls the L60 phase. Summary of the Invention

[0004] The present invention aims to provide a heat treatment method, product and application for improving the performance of Fe-Ga alloys in additive manufacturing, in order to solve the problem that existing heat treatment technologies cannot simultaneously achieve residual stress release, favorable texture retention and precise control of L60 nanometer precipitates in Fe-Ga alloys formed by LPBF.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A heat treatment method for improving the properties of additively manufactured Fe-Ga alloys includes the following steps:

[0007] S1: Solution treatment, the laser additive Fe-Ga alloy is held at 700-850℃ for 0.5-3h, and the process is protected by argon gas;

[0008] S2: Salt water cooling, the Fe-Ga alloy after solution treatment is placed directly in salt water at room temperature to cool to room temperature;

[0009] S3: Aging treatment, the Fe-Ga alloy cooled by brine is held at 280-320℃ for 1-12 hours;

[0010] S4: Water cooling treatment, the aged Fe-Ga alloy is water cooled to room temperature;

[0011] Among them, the Fe-Ga alloy manufactured by laser additive manufacturing <100> The area of ​​BD texture shall account for no less than 75%.

[0012] Furthermore, the solution treatment temperature is 750℃ and the holding time is 2h; the aging treatment temperature is 300℃ and the holding time is 6h.

[0013] Furthermore, the brine is a 10% NaCl aqueous solution at room temperature.

[0014] Furthermore, the composition of the Fe-Ga alloy is Fe 81 Ga 19 .

[0015] Furthermore, the Fe-Ga alloy manufactured by laser additive manufacturing is prepared using a layer-by-layer remelting process, in which each layer is laser-scanned twice.

[0016] Furthermore, after solution treatment and brine cooling, the Fe-Ga alloy does not recrystallize. <100> The area of ​​the BD texture remains no less than 75%, and it is a single A2 phase with the L60 phase completely dissolved. After aging and water cooling, the size of the L60 precipitate in the Fe-Ga alloy is 5–10 nm, and the number density is 3.0 × 10⁻⁶. 10 mm -2 above.

[0017] Furthermore, after heat treatment, the parallel-direction saturation magnetostrictive strain λ of the Fe-Ga alloy... ∥ The saturation magnetostriction coefficient λ is above 250 ppm. s It is above 290 ppm.

[0018] The present invention also provides an Fe-Ga alloy product, which is obtained by heat treatment using any of the above-mentioned methods.

[0019] The present invention also provides the application of the above-mentioned Fe-Ga alloy product as a magnetostrictive element in the preparation of magnetostrictive sensors or microactuators.

[0020] The principles and beneficial effects of the technical solution are as follows:

[0021] 1. By precisely controlling the solution treatment temperature at 700–850℃ (especially 750℃), the alloy undergoes only a recovery process without recrystallization. This effectively releases some of the residual stress accumulated during LPBF forming, providing an ideal matrix for the uniform precipitation of the L60 phase and the enhancement of magnetic domain wall mobility. It also perfectly preserves the strong [structure / structure] formed during LPBF forming. <100> The texture avoids the problem of texture weakening caused by traditional high-temperature annealing;

[0022] 2. An innovative brine cooling step was introduced after solution treatment. The high cooling rate of brine effectively suppressed the uncontrollable pre-precipitation of L60 and DO3 phases, which are very easy to occur during conventional cooling. After brine cooling, the alloy microstructure is a single, highly supersaturated A2 solid solution with complete L60 phase dissolution. Compared with conventional water cooling or furnace cooling, this technique ensures that the matrix has the maximum solute atom supersaturation and the highest nucleation driving force before aging treatment, laying a key initial microstructure foundation for the subsequent high-density and uniform precipitation of L60 phase.

[0023] 3. By controlling the aging temperature (280–320℃) and time (1–12 h), especially under the condition of aging at 300℃ for 6 h, the high concentration of vacancies retained in the matrix after brine cooling were used as rapid diffusion channels to promote uniform nucleation of the L60 phase. The resulting L60 precipitates were small in size (5–10 nm), uniformly distributed, and had a number density as high as 3.0 × 10⁻⁶. 10 mm -2 The above measures effectively inhibited the formation of harmful DO3 and L12 phases; this precipitation state and retention strength <100> The synergistic effect of texture ultimately enhances the saturation magnetostrictive properties λ of the alloy. s The concentration was increased to 299 ppm, an improvement of over 130% compared to before treatment;

[0024] 4. The process path is clear, the operation steps are well-defined, and the equipment requirements are not high. Only a conventional heat treatment furnace and a simple brine quenching medium are needed to achieve efficient processing of complex-shaped LPBF-formed Fe-Ga alloy parts, which has good engineering application value. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the process flow of the present invention;

[0026] Figure 2 Microscopic structure diagram of LPBF formation;

[0027] Figure 3 Magnetostriction curves of LPBF;

[0028] Figure 4 The grain orientation diagram is shown after solid solution treatment at 750℃ followed by cooling with brine.

[0029] Figure 5 Solution treatment at 750℃ followed by cooling with brine. <100> and <110> TEM image with axis;

[0030] Figure 6 Magnetostriction curves after solid solution treatment at 750℃ and cooling with brine;

[0031] Figure 7 Here are the magnetostriction curves under different aging conditions, where:

[0032] A is prepared by solution treatment at 750℃ + brine cooling + aging at 250℃ for 6 hours + water cooling.

[0033] b is prepared by solution treatment at 750℃ + brine cooling + aging at 300℃ for 6 hours + water cooling.

[0034] c is the solution treatment at 750℃ + brine cooling + aging at 300℃ for 12 hours + water cooling.

[0035] d is solution treatment at 750℃ + brine cooling + aging at 350℃ for 6 hours + water cooling;

[0036] Figure 8 For different time-sensitive situations <100> TEM image with axis;

[0037] Figure 9 For different time-sensitive situations <110> TEM image with axis;

[0038] Figure 10 Solution treatment at 750℃ + water cooling + aging at 300℃ for 6 hours + water cooling <100> and <110> TEM image with axis;

[0039] Figure 11 Magnetostriction curves for solution treatment at 750℃ + water cooling + aging at 300℃ for 6 hours + water cooling;

[0040] Figure 12 SEM image of solution treatment at 750℃ followed by furnace cooling;

[0041] Figure 13 Magnetostriction curves at 750℃ solution treatment followed by furnace cooling;

[0042] Figure 14TEM image of solution treatment at 750℃ + brine cooling + aging at 400℃ for 6 h + water cooling;

[0043] Figure 15 Magnetostriction curves for solution treatment at 750℃ + brine cooling + aging at 400℃ for 6 h + water cooling; Detailed Implementation

[0044] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments:

[0045] The LPBF-formed Fe used in the following examples 81 Ga 19 All alloy reference samples were prepared using the same layer-by-layer remelting process to ensure that they had a highly consistent initial microstructure before heat treatment.

[0046] I. Preparation and Initial Characterization of Reference Samples

[0047] Raw materials and equipment

[0048] Fe prepared by gas atomization method 81 Ga 19 Pre-alloyed powder (particle size D50 = 32.28μm) was used as raw material; the forming was carried out using a HANSM100 laser powder bed melting equipment, the substrate preheating temperature was 150℃, and the forming process was carried out under the protection of high-purity argon (oxygen content <100 ppm).

[0049] Preparation process and parameters

[0050] The LPBF layer-by-layer remelting process is adopted, with each layer undergoing two laser scans. The specific parameters are as follows:

[0051] First scan (deposition scan): laser power 120W, scanning speed 1100mm / s, scanning spacing 0.06mm, layer thickness 0.04mm;

[0052] Second scan (remelting scan): laser power 80W, scanning speed 500mm / s, scanning interval 0.04mm.

[0053] A scanning strategy involving a 67° rotation between adjacent forming layers was employed, while the deposition and remelting scan paths within the same layer remained parallel. This resulted in the formation of a cube specimen with dimensions of 10mm × 12mm × 3mm.

[0054] Initial organization and performance

[0055] Crystallographic structure: Electron backscatter diffraction (EBSD) analysis showed that the reference sample... <100> The texture area along the building direction (BD) accounts for 81.7%, the average grain size is 17.13 μm, and the geometrically necessary dislocation density is approximately 11.6 × 10⁻⁶. 13 m -2 .

[0056] Precipitated phase: Transmission electron microscopy (TEM) analysis showed that there was a high density of L60 nanoparticle precipitates in the reference sample, with a size of less than 5 nm.

[0057] Magnetostrictive properties: At room temperature, a magnetic field was applied along the build direction, and the saturation magnetostrictive strain λ in the parallel direction was measured. ∥ Approximately 212 ppm, saturation magnetostriction coefficient λ s It is approximately 240 ppm.

[0058] II. Implementation Examples

[0059] Example 1: Solution treatment at 750℃ + brine cooling + aging at 300℃ for 6 hours + water cooling

[0060] This embodiment provides a preferred implementation of the present invention.

[0061] Step S1: Solution treatment, take the Fe formed by the above LPBF 81 Ga 19 Alloy reference samples were placed in quartz tubes, repeatedly evacuated and backfilled with high-purity argon gas (purity ≥99.999%), and finally vacuum sealed. The sealed quartz tubes were placed in a box-type resistance furnace and heated to 750°C at a heating rate of 10°C / min, and held at this temperature for 2 hours.

[0062] Step S2: After the brine cooling and heat preservation is completed, quickly remove the quartz tube and smash it, so that the sample falls directly into the pre-prepared 10 wt.% NaCl aqueous solution at room temperature to cool to room temperature;

[0063] Step S3: Aging treatment. After the sample is cooled by brine, it is taken out and dried. It is then transferred to another vacuum tube furnace, heated to 300°C, and held for 6 hours.

[0064] Step S4: Water cooling treatment. After the aging treatment is completed, the sample is taken out of the furnace and directly water-cooled to room temperature.

[0065] The treated samples were subjected to microstructure and property analysis, and the results are characterized as follows:

[0066] Texture and dislocations: EBSD analysis showed that the treated sample still maintained strong texture. <100> Texture, <100> The area of ​​the BD texture was 75.1%, and no recrystallization occurred. The density of geometrically necessary dislocations decreased to 7.0 × 10⁻⁶. 13 m -2 This indicates that the residual stress has been effectively released.

[0067] Precipitated phase: TEM observation shows that along <100> Clear superlattice diffraction spots appeared in the axial selected area electron diffraction pattern (see [reference]). Figure 8 b1), Fast Fourier Transform (FFT) analysis of high-resolution images (see b1). Figure 8 b2) and its inverse Fourier transform image (see b2) Figure 8 b3) shows a large number of uniform and fine precipitates. Statistical analysis shows that the size of the precipitates is all below 5 nm, with a number density as high as 3.0 × 10⁻⁶. 10 mm -2 ,along <100> Analysis of the belt shaft (see) Figure 9 b1, Figure 9 b3) Further confirmation that these precipitates are L60 phases and no obvious DO3 phase characteristic diffraction spots were detected.

[0068] Magnetostrictive properties: Magnetostrictive property test results show that the parallel direction saturation magnetostriction λ ∥ Up to 250ppm, saturation magnetostriction coefficient λ s 299 ppm (see Figure 7 (b) represents a 41% improvement over the LPBF morphological benchmark sample.

[0069] Example 2: Solution treatment at 750℃ + brine cooling + aging at 300℃ for 12 hours + water cooling

[0070] The only difference between this embodiment and Embodiment 1 is that the processing time in step S3 is extended to 12 hours; the other steps are exactly the same.

[0071] The treated samples were subjected to microstructure and property analysis, and the results are characterized as follows:

[0072] Precipitated phase: TEM analysis showed that the size of the L60 precipitates increased, and some areas showed precipitate confluence, with the number density decreasing to 2.6 × 10⁻⁶. 10 mm -2 (See) Figure 8 c), and at the same time, faint superlattice diffraction spots representing the beginning of the DO3 phase were observed (see c). Figure 9 c3).

[0073] Magnetostrictive properties: Magnetostrictive property test results show that λ s Decreased to 249 ppm (see Figure 7 c), lower than Example 1.

[0074] This indicates that excessively long aging times can lead to coarsening of the precipitated phase and promote the formation of harmful DO3 phases, thereby weakening the magnetoelastic coupling effect.

[0075] III. Comparative Example

[0076] Comparative Example 1: Solution treatment at 750℃ + water cooling + aging at 300℃ for 6 hours + water cooling

[0077] The difference between this comparative example and Example 1 is that conventional water cooling (room temperature deionized water) is used instead of brine cooling in step S2, while the rest of the steps are exactly the same as in Example 1.

[0078] The treated samples were subjected to microstructure and property analysis, and the results are characterized as follows:

[0079] Precipitated phase: TEM analysis showed that a mixed phase of L60 and DO3 with relatively large size and uneven distribution precipitated during the cooling process of the water-cooled sample (see [link]). Figure 10 This leads to a decrease in the supersaturation of matrix solute atoms, and after subsequent aging treatment, the number density of precipitated phases is only 8.0 × 10⁻⁶. 9 mm -2 The concentration was much lower than in Example 1, and the distribution was uneven, with a significant increase in the DO3 phase content.

[0080] Magnetostrictive properties: Magnetostrictive property test results show that its λ s Only 237 ppm (see Figure 11 The concentration was reduced by approximately 21% compared to Example 1.

[0081] This comparative example demonstrates the importance of brine cooling as a key step in suppressing pre-precipitation and creating an ideal initial tissue state for subsequent aging.

[0082] Comparative Example 2: Solution treatment at 750℃ + furnace cooling

[0083] The difference between this comparative example and Example 1 is that step S2 involves slow cooling in the furnace and no subsequent aging treatment is performed (i.e., steps S3 and S4 are omitted).

[0084] The treated samples were subjected to microstructure and property analysis, and the results are characterized as follows:

[0085] Precipitated phase: Scanning electron microscopy (SEM) analysis revealed a large number of continuous granular L12 phase particles with a size of 200–500 nm precipitated at the grain boundaries of the furnace-cooled sample (see [link to SEM]). Figure 12 The L12 phase has negative magnetostrictive properties, which can severely degrade the magnetic properties of materials.

[0086] Magnetostrictive properties: Magnetostrictive property test results show that its λ s Decreased to 156 ppm (see Figure 13 ).

[0087] This comparative example shows that slow cooling promotes the precipitation of the equilibrium phase L12, which is a process path that must be avoided.

[0088] Comparative Example 3: Different Aging Temperatures

[0089] To verify the preferred aging temperature window (280-320℃) of the present invention, three test groups were set up. The steps were basically the same as those in Example 1, except that the aging temperature in step S3 was changed to 250℃, 350℃ and 400℃ respectively, and the aging time was 6h for all groups.

[0090] Test group 1 (aging at 250℃):

[0091] The treated samples were subjected to microstructure and property analysis, and the results are characterized as follows:

[0092] Precipitated phase: TEM analysis showed no superlattice spots in either the SAED or high-resolution FFT images (see...). Figure 8 a) indicates that the temperature of 250℃ is too low to provide sufficient kinetic conditions to drive significant solute atom diffusion and L60 phase nucleation, and the structure still maintains a near-A2 single-phase structure.

[0093] Magnetostrictive properties: Magnetostrictive property test results show that its λ s Only 152 ppm (see Figure 8 c), with almost no improvement compared to the unaged brine-cooled state.

[0094] Test group 2 (aging at 350℃):

[0095] The treated samples were subjected to microstructure and property analysis, and the results are characterized as follows:

[0096] Precipitated phase: TEM analysis showed that the precipitated phase was significantly larger and unevenly distributed, with a number density decreasing to 1.8 × 10⁻⁶. 10 mm -2 (See) Figure 8 c), at the same time, strong DO3 phase superlattice diffraction spots appeared (see c). Figure 9 c3) indicates that excessively high aging temperatures promoted the precipitation of a large amount of the stable phase DO3.

[0097] Magnetostrictive properties: Magnetostrictive property test results show that its λ s Only 238 ppm (see Figure 7 a).

[0098] Test group 3 (aging at 400℃):

[0099] The treated samples were subjected to microstructure and property analysis, and the results are characterized as follows:

[0100] Precipitated phases: TEM analysis showed a significant decrease in the density of precipitated phases within the grains, while continuous, coarse L12 phase particles appeared at the grain boundaries (see [link to TEM analysis]). Figure 14 ).

[0101] Magnetostrictive properties: Magnetostrictive property test results show that due to the formation of the harmful L12 phase, its λ s It dropped significantly to 111 ppm (see Figure 15 ).

[0102] The three sets of experiments showed that too low an aging temperature (250℃) could not effectively precipitate the L60 phase, while too high an aging temperature (350℃, 400℃) would lead to coarsening of the precipitated phase and the formation of harmful DO3 or L12 phases, neither of which could achieve the ideal magnetostrictive properties. This proved that 300℃ is the optimal temperature window for controlling the precipitation of the L60 phase.

[0103] The above descriptions are merely embodiments of the present invention, and common knowledge regarding specific technical solutions or characteristics is not elaborated upon here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solutions of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A heat treatment method for improving the properties of additively manufactured Fe-Ga alloys, characterized in that: Includes the following steps: S1: Solution treatment, the laser additive Fe-Ga alloy is held at 700-850℃ for 0.5-3h, and the process is protected by argon gas; S2: Salt water cooling, the Fe-Ga alloy after solution treatment is placed directly in salt water at room temperature to cool to room temperature; S3: Aging treatment, the Fe-Ga alloy cooled by brine is held at 280-320℃ for 1-12 hours; S4: Water cooling treatment, the aged Fe-Ga alloy is water cooled to room temperature; Among them, the laser additive manufacturing of Fe-Ga alloy <100> The area of ​​BD texture shall account for no less than 75%.

2. The heat treatment method for improving the properties of additively manufactured Fe-Ga alloys according to claim 1, characterized in that: The solution treatment temperature is 750℃ and the holding time is 2h; the aging treatment temperature is 300℃ and the holding time is 6h.

3. The heat treatment method for improving the properties of additively manufactured Fe-Ga alloys according to claim 1, characterized in that: The brine is a 10% NaCl aqueous solution at room temperature.

4. The heat treatment method for improving the properties of additively manufactured Fe-Ga alloys according to claim 1, characterized in that: The Fe-Ga alloy is composed of Fe 81 Ga 19 .

5. The heat treatment method for improving the properties of additively manufactured Fe-Ga alloys according to claim 1, characterized in that: The Fe-Ga alloy manufactured by laser additive manufacturing is prepared by a layer-by-layer remelting process, wherein each layer is laser-scanned twice.

6. The heat treatment method for improving the properties of additively manufactured Fe-Ga alloys according to claim 1, characterized in that: After solution treatment and brine cooling, the Fe-Ga alloy does not recrystallize. <100> The area ratio of the BD texture is still not less than 75%, and it is a single A2 phase with the L60 phase completely dissolved. After aging treatment and water cooling, the size of the L60 precipitate in the Fe-Ga alloy is 5-10 nm, and the number density is 3.0 × 10⁻⁶. 10 mm -2 above.

7. The heat treatment method for improving the properties of additively manufactured Fe-Ga alloys according to claim 2, characterized in that: After the heat treatment method described above, the parallel-direction saturation magnetostrictive strain λ of the Fe-Ga alloy is... ∥ The saturation magnetostriction coefficient λ is above 250 ppm. s It is above 290 ppm.

8. An Fe-Ga alloy product, characterized in that, It is obtained by heat treatment according to any one of claims 1-7.

9. The application of the Fe-Ga alloy product according to claim 8 as a magnetostrictive element in the preparation of magnetostrictive sensors or microactuators.

Images