A method for characterizing the longitudinal section structure of an ultra-thin and ultra-narrow tungsten-rhenium alloy strip

Abstract

The application discloses a kind of ultra-thin ultra-narrow tungsten-rhenium alloy strip longitudinal section organization characterization method, comprising the following steps: cleaning strip;Select dovetail clamp as fixed clamp, after removing tail handle, coat double-sided adhesive on back flat section, and multiple strip is fixed to the bottom of dovetail clamp in the way of longitudinal section horizontal downward and is bonded;Hot inlay;Gradient grinding and polishing;Corrosive agent prepared by CuSO4 5H2O, H2O and mass fraction 25-28% NH3 H2O is used to wipe the surface of corrosion sample;Observe longitudinal section microstructure under metallurgical microscope and collect image.The application realizes the accurate orientation and stable support of longitudinal section by dovetail clamp fixing method, and complete, flat and clear organization cross section can be obtained by combining special corrosive agent, which is simple, safe and environmentally friendly.

Description

Technical Field

[0001] This invention belongs to the field of microstructure analysis technology, specifically relating to a method for characterizing the longitudinal section structure of ultrathin and ultranarrow tungsten-rhenium alloy strips. Background Technology

[0002] Tungsten-rhenium alloy is a solid solution alloy composed of tungsten and rhenium, possessing high melting point, high strength, high hardness, good high-temperature creep resistance, and excellent thermal shock resistance. The addition of rhenium significantly improves the low-temperature brittleness of tungsten, increasing the material's recrystallization temperature and high-temperature strength. Tungsten-rhenium alloy strips, as key functional materials, are widely used in aerospace, nuclear energy, electronic devices, and high-end medical equipment, such as rocket engine nozzles, nuclear reactor structural components, X-ray targets, and high-temperature thermocouple protective sheaths. With the development of high-end equipment towards miniaturization and precision, the demand for ultra-thin and ultra-narrow tungsten-rhenium alloy strips with a thickness of less than 0.1 mm and a width of no more than 0.2 mm is increasingly urgent. The uniformity and consistency of their microstructure directly determine the product's service reliability and service life.

[0003] Microstructure analysis, especially longitudinal section microstructure analysis, is a crucial method for evaluating the rationality of tungsten-rhenium alloy strip processing technology and the stability of product quality. Due to size effects, ultra-thin and ultra-narrow tungsten-rhenium alloy strips are prone to problems such as uneven grain refinement, edge stress concentration, and thickness-direction microstructure delamination during fabrication. These microscopic defects are difficult to detect through macroscopic inspection and can only be accurately identified through longitudinal section microstructure observation. Furthermore, high-end applications such as semiconductors and aerospace have extremely stringent requirements for the uniformity and density of the strip's microstructure. Longitudinal section microstructure analysis can provide direct microscopic evidence for optimizing the strip fabrication process. In addition, the microstructure characteristics of the longitudinal section are closely related to the strip's mechanical properties, thermal shock resistance, and service life. Therefore, establishing a longitudinal section microstructure characterization method suitable for ultra-thin and ultra-narrow tungsten-rhenium alloy strips is of great significance.

[0004] However, the preparation of metallographic samples for longitudinal section microstructure analysis of ultrathin and ultra-narrow tungsten-rhenium alloy strips is extremely difficult. Tungsten-rhenium alloy strips are inherently hard and brittle, and their extremely thin and narrow dimensions result in insufficient rigidity, making precise positioning during sample mounting difficult. This leads to tilting and collapse, hindering stable sample fixation and precise orientation control of the longitudinal section. During grinding and polishing, the strip is prone to problems such as skewed grinding, uneven grinding, detachment, edge curling, and excessive chamfering, causing the longitudinal section observation area to deviate significantly from the target position, making it difficult to obtain a complete and flat observation section. During etching, due to the strong corrosion resistance of tungsten-rhenium alloys, traditional etchants are ineffective in etching out their microstructure. While a potassium ferrocyanide-containing metallographic etching method has been reported in the prior art, which can reveal the microstructure of tungsten materials to some extent, it has significant shortcomings in terms of safety and environmental friendliness, process stability, and adaptability to the longitudinal sections of ultrathin and ultra-narrow strips. Therefore, there is an urgent need to develop a characterization method that is safe, environmentally friendly, process-controllable, and applicable to the longitudinal section microstructure analysis of ultrathin and ultranarrow tungsten-rhenium alloy strips. Summary of the Invention

[0005] The purpose of this invention is to provide a method for characterizing the microstructure of ultrathin and ultranarrow tungsten-rhenium alloy strips in longitudinal sections, so as to solve the technical problems in the prior art where it is difficult to stably prepare metallographic samples of ultrathin and ultranarrow tungsten-rhenium alloy strips in longitudinal sections, and where there is a lack of safe and environmentally friendly special etchants to clearly show their microstructure.

[0006] In this invention, "ultra-thin and ultra-narrow" refers to tungsten-rhenium alloy strip with a thickness ≤ 0.1 mm and a width ≤ 0.2 mm.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A method for characterizing the longitudinal section microstructure of ultrathin and ultranarrow tungsten-rhenium alloy strip includes the following steps: cleaning, placing the tungsten-rhenium alloy strip to be observed in a beaker, ultrasonically cleaning it, and then quickly drying it; fixing, selecting a dovetail clip as a fixing fixture, removing the two tails of the dovetail clip and placing it vertically, so that the bottom triangular area serves as a horizontal support surface, keeping the straight back section vertical, uniformly applying double-sided adhesive to the straight back section, cutting 2 to 5 sections of tungsten-rhenium alloy strip, using tweezers to pick up the strip sample, and adhering it to the bottom of the straight back section of the dovetail clip, so that the longitudinal section of the strip is horizontal and flush with the bottom surface of the dovetail clip. The remaining strip samples were fixed horizontally and at equal intervals in the same manner; inlaying was performed by moving the dovetail clips with the fixed strip samples into the inlay mold for hot inlaying; grinding and polishing were performed by grinding and polishing the inlaid samples in sequence; etching was performed by using a metallographic etchant prepared from CuSO4·5H2O, H2O and NH3·H2O with a mass fraction of 25% to 28%, and the surface of the strip sample was evenly and gently wiped with cotton soaked in the etchant, and the sample surface was dried immediately after etching was completed; image acquisition was performed by observing the microstructure of the longitudinal section of the sample under an optical metallographic microscope and acquiring images.

[0008] Furthermore, the ultrasonic cleaning time is 5s to 20s.

[0009] Furthermore, the pressure for hot mounting does not exceed 100 bar, and the heating temperature does not exceed 200°C.

[0010] Furthermore, grinding involves grinding the inlaid sample sequentially from coarse to fine on silicon carbide wet sandpaper of grades 120#, 500#, 1000#, 2500#, and 4000#. Each time the sandpaper is changed, the sample is rotated 45° to 135° until the scratches of the previous grade are completely removed. Polishing involves polishing the sample with 2.5 μm polycrystalline diamond polishing agent until the grinding marks are completely removed, and then cleaning and drying the sample surface.

[0011] Furthermore, the formulation of the corrosive agent is: (3-6)g CuSO4·5H2O + (15-25)ml H2O + (8-12)ml NH3·H2O with a mass fraction of 25%-28%; the corrosion time is 20s-40s.

[0012] The method for characterizing the longitudinal section microstructure of ultrathin and ultranarrow tungsten-rhenium alloy strips provided by this invention has the following beneficial effects: First, by using a dovetail clip + double-sided adhesive fixing method, double-sided adhesive is applied to the straight section of the back of the dovetail clip and the longitudinal section of the strip is fixed horizontally downwards. This achieves equidistant and horizontal fixing of multiple ultrathin and ultranarrow strip longitudinal section samples, solving the problems of sample curling, tilting, falling off, and difficulty in precise orientation of the longitudinal section in traditional mounting methods, and can stably obtain a complete and flat observation section. Second, a special etchant prepared with CuSO4·5H2O+H2O+NH3·H2O is used, replacing the toxic etchants such as potassium ferricyanide used in the prior art. This method achieves clear display of the microstructure of tungsten-rhenium alloys while being safe and environmentally friendly, significantly reducing operational safety risks and the difficulty of waste liquid treatment. Third, the process integrates cleaning, fixing, embedding, polishing, etching, and image acquisition into a complete characterization process. It is simple to operate, low in cost, has a high success rate, and good repeatability, providing a reliable technical means for the microstructure quality control of ultra-thin and ultra-narrow tungsten-rhenium alloy strips. Attached Figure Description

[0013] Figure 1 This is a microstructure image of a longitudinal section of the tungsten-rhenium alloy strip obtained in Example 1 of the present invention; Figure 2 This is a microstructure image of a longitudinal section of the tungsten-rhenium alloy strip obtained in Example 2 of the present invention; Figure 3 This is a microstructure image of the longitudinal section of the tungsten-rhenium alloy strip obtained in Example 3 of the present invention; Figure 4 The image shows a microscopic image of the sample obtained in Comparative Example 1 of this invention. Figure 5 The image shows a microscopic image of the sample obtained in Comparative Example 2 of this invention. Figure 6 The image shows a microscopic image of the sample obtained in Comparative Example 3 of this invention. Figure 7 This is a microscopic image of the sample obtained in Comparative Example 4 of this invention. Detailed Implementation

[0014] To make the technical problems, technical solutions and advantages of the present invention clearer, the following will describe them in detail with reference to the accompanying drawings, specific embodiments and comparative examples.

[0015] Example 1 The tungsten-rhenium alloy strip to be observed was placed in a beaker, ultrasonically cleaned for 5 seconds, and then quickly dried. A dovetail clamp was selected as the fixing fixture. The two tails of the dovetail clamp were removed, leaving the triangular area at its bottom as a horizontal support surface, while the straight section on the back remained vertical. Double-sided adhesive was evenly applied to the straight section on the back, and then three sections of tungsten-rhenium alloy strip were cut using pliers. The first strip sample was picked up with tweezers, ensuring its longitudinal section to be observed was horizontally downwards, and fixed to the bottom of the dovetail clamp, ensuring that the longitudinal section and the bottom surface of the dovetail clamp were at the same level. The remaining strip samples were then fixed horizontally and at equal intervals. The dovetail clamp with the fixed strip samples was moved into the mounting mold, and the mounting pressure was adjusted to 100 bar, and the heating temperature was set to 100℃. The mounted specimens were sequentially ground from coarse to fine on silicon carbide wet sandpaper of grades 120#, 500#, 1000#, 2500#, and 4000#, rotating the specimen 45° each time the sandpaper was changed, until the scratches from the previous grade were completely removed. The specimens were then polished with 2.5 μm polycrystalline diamond polishing compound until all scratches were removed. A cotton swab was used to etch the specimens with an etching solution prepared from 6 g CuSO4·5H2O + 25 ml H2O + 12 ml NH3·H2O (25%–28% by mass), for 20 seconds. After etching, the entire longitudinal section of the specimen was observed and images were acquired under an optical metallographic microscope. The resulting microstructure images are shown below. Figure 1 As shown. By Figure 1 It can be seen that the longitudinal section of the tungsten-rhenium alloy strip has a distinct fibrous or elongated structure along the processing direction, with the grains being significantly elongated and roughly parallel to the axial direction. No obvious metallurgical defects such as cracks or pores are observed in the longitudinal section.

[0016] Example 2 The tungsten-rhenium alloy strip to be observed was placed in a beaker, ultrasonically cleaned for 20 seconds, and then quickly dried. A dovetail clamp was selected as the fixing fixture. The two tails of the dovetail clamp were removed, leaving the triangular area at its bottom as a horizontal support surface, while the straight section on the back remained vertical. Double-sided adhesive was evenly applied to the straight section on the back, and then two sections of tungsten-rhenium alloy strip were cut using pliers. The first strip sample was picked up with tweezers, ensuring its longitudinal section to be observed was horizontally downwards, and fixed to the bottom of the dovetail clamp, ensuring that the longitudinal section and the bottom surface of the dovetail clamp were at the same level. The remaining strip samples were then fixed horizontally and at equal intervals. The dovetail clamp with the fixed strip samples was moved into the mounting mold, and the mounting pressure was adjusted to 50 bar, and the heating temperature was set to 200℃. The mounted specimens were sequentially ground on silicon carbide wet sandpaper of grades 120#, 500#, 1000#, 2500#, and 4000#, from coarse to fine. Each time the sandpaper was changed, the specimen was rotated 135° until the scratches from the previous grade were completely removed. The specimens were then polished with 2.5 μm polycrystalline diamond polishing agent until all scratches were removed. A cotton swab was used to apply an etching solution prepared with 3 g CuSO4·5H2O + 15 ml H2O + 8 ml NH3·H2O (25%–28% by mass) for 40 seconds. After etching, the entire longitudinal section of the specimen was observed and images were acquired under an optical metallographic microscope. The resulting microstructure images are shown below. Figure 2 As shown. By Figure 2 It can be seen that the longitudinal section of the tungsten-rhenium alloy strip has a distinct fibrous or elongated structure along the processing direction, with the grains being significantly elongated and roughly parallel to the axial direction. The left edge of the strip shows obvious layering, while the right side shows a white, elongated, non-uniform structure that runs through the entire field of view.

[0017] Example 3 The tungsten-rhenium alloy strip to be observed was placed in a beaker, ultrasonically cleaned for 10 seconds, and then quickly dried. A dovetail clamp was selected as the fixing fixture. The two tails of the dovetail clamp were removed, leaving the triangular area at its bottom as a horizontal support surface, while the straight section on the back remained vertical. Double-sided adhesive was evenly applied to the straight section on the back, and then five sections of tungsten-rhenium alloy strip were cut using pliers. The first strip sample was picked up with tweezers, ensuring its longitudinal section to be observed was horizontally downwards, and fixed to the bottom of the dovetail clamp, ensuring that the longitudinal section and the bottom surface of the dovetail clamp were at the same level. The remaining strip samples were then fixed horizontally and at equal intervals. The dovetail clamp with the fixed strip samples was moved into the mounting mold, and the mounting pressure was adjusted to 80 bar, and the heating temperature to 150℃. The mounted samples were sequentially ground from coarse to fine on silicon carbide wet sandpaper of grades 120#, 500#, 1000#, 2500#, and 4000#. Each time the sandpaper was changed, the sample was rotated 90° until the scratches from the previous grade were completely removed. The samples were then polished with a 2.5 μm polycrystalline diamond polishing agent until all scratches were removed. A cotton swab was used to apply an etching solution prepared with 5 g CuSO4·5H2O + 20 ml H2O + 10 ml NH3·H2O (25%–28% by mass) for 30 seconds. After etching, the entire longitudinal section of the sample was observed and images were acquired under an optical metallographic microscope. The resulting microstructure was consistent with that of Examples 1 and 2. The longitudinal section microstructure was fibrous or elongated along the processing direction, with significantly elongated grains that were roughly parallel to the axial direction. All five strip segments were intact and without detachment, and the microstructure was clearly discernible.

[0018] Comparative Example 1 All other experimental conditions remained consistent with Example 1. Tungsten-rhenium alloy strips were directly heat-set without using the method of applying double-sided adhesive to the straight section of the back of the dovetail clip. After grinding, polishing, and etching, images were collected as follows: Figure 4 As shown. Analysis Figure 4 It is known that under direct hot mounting conditions, the contact area between the ultra-thin and ultra-narrow tungsten-rhenium alloy strip and the mounting material is small, resulting in insufficient bonding strength. Therefore, during the subsequent grinding and polishing process, the strip is subjected to continuous grinding and rolling action by the abrasive particles, eventually causing it to detach from the mounting sample.

[0019] Comparative Example 2 All other experimental conditions remained the same as in Example 1. The fixing method was changed from coating the straight section of the dovetail clip with double-sided adhesive to a standard metallographic sample clamp, used to hold the ultra-thin, ultra-narrow tungsten-rhenium alloy strip. The strip was then subjected to hot mounting, polishing, and etching. Images were collected as follows: Figure 5 As shown. By Figure 5It is evident that when using ordinary metallographic sample holders, the bottom edge of the strip warps up during the mounting process, and its entire longitudinal section fails to fully adhere to and be coplanar with the bottom of the mounting material. This results in the inability to obtain a complete and flat observation section after grinding and polishing. This indicates that for ultra-thin and ultra-narrow tungsten-rhenium alloy strips, it is difficult to achieve stable sample fixation and precise orientation control of the longitudinal section using only ordinary metallographic sample holders.

[0020] Comparative Example 3 All other experimental conditions remained the same as in Example 1, except that the etchant was replaced with a 10% nitric acid alcohol solution, and the etching time was 40 seconds. After treatment, the surface of the tungsten-rhenium alloy strip sample was not corroded, the microstructure could not be revealed, and it remained in a bright, polished state, as shown. Figure 6 As shown, using a 10% nitric acid alcohol solution as an etchant cannot achieve the same tissue visualization effect as using CuSO4·5H2O + H2O +NH3·H2O etchant.

[0021] Comparative Example 4 All other experimental conditions remained the same as in Example 1, except that the etchant was replaced with 2 mL hydrofluoric acid + 3 mL hydrochloric acid + 5 mL nitric acid + 190 mL aqueous solution, and the etching time was 40 s. After treatment, the surface of the tungsten-rhenium alloy strip sample was not corroded, the microstructure could not be revealed, and it remained in a bright, polished state. Figure 7 As shown, the method using 2 mL hydrofluoric acid + 3 mL hydrochloric acid + 5 mL nitric acid + 190 mL aqueous solution cannot achieve the same tissue visualization effect as the CuSO4·5H2O + H2O + NH3·H2O etchant.

[0022] The above results demonstrate that the method of this invention is applicable to the preparation and characterization of longitudinal section microstructure samples of ultrathin and ultranarrow tungsten-rhenium alloy strips. Examples 1-3 successfully obtained clear longitudinal section images under different parameter combinations. Simply changing the sample embedding or clamping method, or changing the type of etchant, cannot achieve the same effect. This invention, through the synergistic combination of dovetail clip + double-sided tape fixing method and a dedicated CuSO4·5H2O+H2O+NH3·H2O etchant, successfully achieves stable sample preparation and clear characterization of the longitudinal section microstructure of ultrathin and ultranarrow tungsten-rhenium alloy strips.

Claims

1. A method for characterizing the microstructure of an ultrathin and ultranarrow tungsten-rhenium alloy strip in a longitudinal section, characterized in that, Includes the following steps: S1. Cleaning: Place the tungsten-rhenium alloy strip to be observed into a beaker, clean it ultrasonically, and then quickly dry it. S2. Fixing: Select a dovetail clip as the fixing fixture. After removing the two tail shanks of the dovetail clip, place it vertically so that the bottom triangular area serves as a horizontal support surface and the straight back section remains vertical. Apply double-sided adhesive evenly to the straight back section and cut 2 to 5 sections of tungsten-rhenium alloy strip. Use tweezers to pick up the strip sample and adhere it to the bottom of the straight back section of the dovetail clip, so that the longitudinal section of the strip is horizontal and flush with the bottom surface of the dovetail clip. Fix the remaining strip samples horizontally and at equal intervals in the same manner. S3, Inlay: Move the dovetail clip that has fixed the strip sample into the inlay mold for hot inlay; S4. Grinding and polishing: Grind and polish the inlaid sample in sequence; S5. Corrosion: Use a metallographic etchant prepared from CuSO4·5H2O, H2O and NH3·H2O with a mass fraction of 25% to 28%. Use cotton to apply the etchant evenly and gently to wipe the surface of the strip sample. After corrosion, immediately blow dry the sample surface. S6. Image Acquisition: Observe the microstructure of the longitudinal section of the sample under an optical metallographic microscope and acquire images.

2. The method according to claim 1, characterized in that, In step S1, the ultrasonic cleaning time is 5s to 20s.

3. The method according to claim 1, characterized in that, In step S3, the pressure of the hot embedding does not exceed 100 bar, and the heating temperature does not exceed 200°C.

4. The method according to claim 1, characterized in that, In step S4, the grinding involves grinding the inlaid sample sequentially from coarse to fine on silicon carbide wet sandpaper of grades 120#, 500#, 1000#, 2500#, and 4000#. Each time the sandpaper is changed, the sample is rotated 45°~135° until the scratches of the previous grade are completely removed. The polishing involves polishing the sample with 2.5 μm polycrystalline diamond polishing agent until the grinding marks are completely removed, and then cleaning and drying the sample surface.

5. The method according to claim 1, characterized in that, In step S5, the formulation of the corrosive agent is: (3-6)g CuSO4·5H2O + (15-25)ml H2O + (8-12)ml NH3·H2O with a mass fraction of 25%-28%; the corrosion time is 20s-40s.

Images