Metallographic corrosive, preparation method thereof and metallographic display method of zirconium-vanadium-iron alloy

Abstract

The invention provides a metallographic corrosive agent, a preparation method thereof and a metallographic display method of a zirconium-vanadium-iron alloy, and particularly relates to the technical field of metallographic display detection. The metallographic corrosive provided by the invention comprises hydrochloric acid, nitric acid and water, wherein the volume ratio of the hydrochloric acid to the nitric acid is (1-2): (1-3); the volume ratio of hydrochloric acid to water is (1-2): (2-6); the mass concentration of the hydrochloric acid is 36-38 wt%; the mass concentration of the nitric acid is 60-70 wt%. According to the method, hydrochloric acid and nitric acid are mixed and then react with metal ions on the surface of a zirconium-vanadium-iron alloy sample to form a compound and dissolve the compound, so that the microstructure of the metal is displayed, iron and hydrochloric acid react to generate hydrogen and bivalent iron salt, and nitric acid reacts with zirconium to generate zirconium nitrate and dissolve in nitric acid; by controlling the dosage ratio of all the components, the corrosion effect can be better controlled, and the grain boundary and the structure of the zirconium-vanadium-iron alloy are clearly displayed.

Description

Technical Field

[0001] The present invention belongs to the technical field of metallographic display detection preparation, and particularly relates to a metallographic etchant, a preparation method thereof, and a metallographic display method for zirconium-vanadium-iron alloy. Background Art

[0002] Zirconium alloy is an alloy formed based on zirconium by adding other alloying elements. Zirconium alloy has a small fast neutron absorption cross-section, good corrosion resistance to liquid metals such as lithium, sodium, and potassium, good strength, plasticity, and processing performance, can resist radiation embrittlement and radiation swelling, and has good dimensional stability under irradiation, and is an important reactor structural material.

[0003] The metallographic morphology of materials can, to a certain extent, reflect the organizational structure and defects of the material matrix phase, thereby discovering the orientation and state, uniformity, etc. of the microstructure, and these factors often determine the quality of the material itself, and have a significant guiding role in the work of adjusting the material preparation process and detecting the material quality. Therefore, in order to study zirconium-vanadium-iron alloy, it is necessary to conduct a metallographic morphology study on zirconium-vanadium-iron alloy. Currently, commonly used etchants include hydrofluoric acid aqueous (acid) solution, sulfuric acid solution, etc. The corrosion rate and corrosion degree of hydrofluoric acid aqueous (acid) solution are not easy to control; the corrosion effect of sulfuric acid solution is not good. The applicability of these etchants is not strong, resulting in the inability to normally detect the metallography of zirconium alloy. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a metallographic etchant, a preparation method thereof, and a metallographic display method for zirconium-vanadium-iron alloy. The metallographic etchant provided by the present invention can clearly display the grain boundaries and microstructure of zirconium-vanadium-iron alloy.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0006] The present invention provides a metallographic etchant, including hydrochloric acid, nitric acid, and water, and the volume ratio of the hydrochloric acid to the nitric acid is 1-2:1-3;

[0007] The volume ratio of the hydrochloric acid to the water is 1-2:2-6;

[0008] The mass concentration of the hydrochloric acid is 36-38 wt%;

[0009] The mass concentration of the nitric acid is 60-70 wt%.

[0010] Preferably, the volume ratio of the hydrochloric acid to the nitric acid is 1:1-2;

[0011] The volume ratio of the hydrochloric acid to the water is 1:2-4.

[0012] The present invention also provides a method for preparing the metallographic etchant described in the above technical solution, which includes the following steps: adding hydrochloric acid and nitric acid to water and mixing them to obtain the metallographic etchant.

[0013] The present invention also provides a method for metallographic display of a zirconium-vanadium-iron alloy, which includes the following steps: immersing the polished surface of the zirconium-vanadium-iron alloy sample with the metallographic etchant prepared by the preparation method described in the above technical solution for corrosion.

[0014] Preferably, the immersion time is 20 to 70 s.

[0015] Preferably, the preparation of the zirconium-vanadium-iron alloy sample includes: successively embedding, grinding, and polishing the zirconium-vanadium-iron alloy to obtain the zirconium-vanadium-iron alloy sample.

[0016] Preferably, after the corrosion, it further includes washing and drying the corroded zirconium-vanadium-iron alloy sample.

[0017] Preferably, after the drying, it further includes microscopically observing the obtained dried metallographic sample.

[0018] Preferably, the grinding includes: successively performing first grinding, second grinding, and third grinding on the embedded zirconium-vanadium-iron alloy;

[0019] The mesh number of the sandpaper used for the first grinding is 160 to 200 mesh;

[0020] The mesh number of the sandpaper used for the second grinding is 380 to 420 mesh;

[0021] The mesh number of the sandpaper used for the third grinding is 1100 to 1300 mesh;

[0022] When successively grinding the zirconium-vanadium-iron alloy, the angle between the directions of different grindings is 90°.

[0023] Preferably, the polishing includes: successively performing first polishing, second polishing, and third polishing on the ground zirconium-vanadium-iron alloy;

[0024] The particle size of the polishing cloth and polishing agent used for the first polishing is 7 to 10 μm;

[0025] The particle size of the polishing cloth and polishing agent used for the second polishing is 2 to 4 μm;

[0026] The particle size of the polishing cloth and polishing agent used for the third polishing is 0.02 to 0.1 μm.

[0027] The present invention provides a metallographic etchant, which includes hydrochloric acid, nitric acid and water. The volume ratio of hydrochloric acid to nitric acid is 1-2:1-3; the volume ratio of hydrochloric acid to water is 1-2:2-6; the mass concentration of hydrochloric acid is 36-38 wt%; the mass concentration of nitric acid is 60-70 wt%. The present invention utilizes the reaction of hydrochloric acid and nitric acid with metal ions on the surface of the zirconium-vanadium-iron alloy sample to form compounds and dissolve them, thereby revealing the microstructure of the metal. Among them, the reaction of iron with hydrochloric acid produces hydrogen and ferrous salts, and nitric acid reacts with zirconium to produce zirconium nitrate, which is soluble in nitric acid; by controlling the dosage ratio between the components, the etching effect can be better controlled, and the grain boundaries and structures of the zirconium-vanadium-iron alloy can be clearly shown. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required to be used in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0029] Figure 1 Metallographic diagrams of the zirconium-vanadium-iron alloy prepared in Example 1 at different magnifications, where a) 200 times, b) 500 times, c) 1000 times;

[0030] Figure 2 Metallographic diagram of the zirconium-vanadium-iron alloy prepared in Example 2 at 200 times;

[0031] Figure 3 Metallographic diagram of the zirconium-vanadium-iron alloy prepared in Example 3 at 200 times;

[0032] Figure 4 Metallographic diagram of the zirconium-vanadium-iron alloy prepared in Comparative Example 1 at 200 times;

[0033] Figure 5 Metallographic diagram of the zirconium-vanadium-iron alloy prepared in Comparative Example 2 at 200 times;

[0034] Figure 6 Metallographic diagram of the zirconium-vanadium-iron alloy prepared in Comparative Example 3 at 200 times. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0035] The present invention provides a metallographic etchant, which includes hydrochloric acid, nitric acid and water. The volume ratio of hydrochloric acid to nitric acid is 1-2:1-3;

[0036] The volume ratio of hydrochloric acid to water is 1-2:2-6;

[0037] The mass concentration of hydrochloric acid is 36-38 wt%;

[0038] The mass concentration of the nitric acid is 60-70 wt%.

[0039] In the present invention, the volume ratio of the hydrochloric acid to the nitric acid is 1-2:1-3, preferably 1:1-2. In the specific embodiments, the volume ratio of the hydrochloric acid to the nitric acid can be 1:1, 1:1.5, 1:2, 1:2.5, 1:3 or 2:1.

[0040] In the present invention, the mass concentration of the hydrochloric acid is 36-38 wt%. In the specific embodiments, the mass concentration of the hydrochloric acid can be 36 wt%, 37 wt% or 38 wt%.

[0041] In the present invention, the mass concentration of the nitric acid is 60-70 wt%. In the specific embodiments, the mass concentration of the nitric acid can be 60 wt%, 65 wt% or 70 wt%.

[0042] In the present invention, the volume ratio of the hydrochloric acid to the water is 1-2:2-6, preferably 1:2-4. In the specific embodiments, the volume ratio of the hydrochloric acid to the water can be 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, 1:5.5 or 1:6.

[0043] The present invention utilizes hydrochloric acid and nitric acid. After the two are mixed, they react with metal ions on the surface of the zirconium-vanadium-iron alloy sample to form compounds and dissolve, thereby revealing the microstructure of the metal. Among them, iron reacts with hydrochloric acid to produce hydrogen and ferrous salts, and nitric acid reacts with zirconium to produce zirconium nitrate and dissolve in nitric acid; by controlling the dosage ratio between the components, the corrosion effect can be better controlled, and the grain boundaries and structures of the zirconium-vanadium-iron alloy can be clearly shown.

[0044] The present invention also provides a preparation method of the metallographic etchant described in the above technical solution, including the following steps: adding hydrochloric acid and nitric acid to water and mixing to obtain the metallographic etchant for the zirconium-vanadium-iron alloy.

[0045] In the present invention, unless otherwise specified, the raw materials and equipment used are all well-known commercially available products in the art.

[0046] In the present invention, adding hydrochloric acid and nitric acid to water and mixing is preferably: adding nitric acid and hydrochloric acid to water in sequence. When preparing the metallographic etchant in the present invention, the acid with a smaller density or higher volatility is mixed first to avoid weakening or invalidating the corrosion effect of the metallographic etchant.

[0047] The present invention has no special requirements for the mixing method, and well-known technical means in the art can be adopted, such as stirring.

[0048] The present invention also provides a metallographic display method for zirconium-vanadium-iron alloy, comprising the following steps: immersing the polished surface of the zirconium-vanadium-iron alloy sample with the metallographic etchant described in the above technical solution for etching.

[0049] In the present invention, the preparation of the zirconium-vanadium-iron alloy sample preferably includes: successively embedding, grinding and polishing the zirconium-vanadium-iron alloy to obtain the zirconium-vanadium-iron alloy sample.

[0050] In the present invention, the embedding preferably includes: placing the zirconium-vanadium-iron alloy in an embedding machine, filling in the embedding material, and heating and curing to obtain the embedded zirconium-vanadium-iron alloy.

[0051] In the present invention, the size of the zirconium-vanadium-iron alloy is preferably 10 mm × 10 mm × 20 mm.

[0052] In the present invention, the embedding material is preferably a metallographic embedding material, which is used to fix or embed sample materials insensitive to temperature.

[0053] In the present invention, the heating temperature for heating and curing is preferably 150-200 °C. At this temperature, it will not cause changes in the tissue structure, crystal shape or physical properties of the sample.

[0054] In the present invention, the grinding preferably includes: successively performing the first grinding, the second grinding and the third grinding on the embedded zirconium-vanadium-iron alloy.

[0055] In the present invention, it is preferably further included to fix sandpapers with different mesh numbers on the grinding machine before grinding.

[0056] In the present invention, the mesh number of the sandpaper used for the first grinding is preferably 160-200 mesh. In specific embodiments, the mesh number of the sandpaper used for the first grinding can be 160 mesh, 180 mesh or 200 mesh.

[0057] In the present invention, the rate of the first grinding is preferably 450-550 r / min. In specific embodiments, the rate of the first grinding can be 450 r / min, 500 r / min or 550 r / min; the time is preferably 25-35 s. In specific embodiments, the time of the first grinding can be 25 s, 30 s or 35 s. In the present invention, the lubricant used for the first grinding is preferably water.

[0058] In the present invention, the mesh number of the sandpaper used for the second grinding is preferably 380-420 mesh. In specific embodiments, the mesh number of the sandpaper used for the second grinding can be 380 mesh, 400 mesh or 420 mesh.

[0059] In the present invention, the rate of the second polishing is preferably 120 - 180 r / min. In a specific embodiment, the rate of the second polishing can be 120 r / min, 140 r / min, 160 r / min or 180 r / min; the time is preferably 2 - 4 min. In a specific embodiment, the time of the second polishing can be 2 min, 3 min or 4 min. In the present invention, the lubricant used for the second polishing is preferably water.

[0060] In the present invention, the mesh number of the sandpaper used for the third polishing is preferably 1100 - 1300 meshes. In a specific embodiment, the mesh number of the sandpaper used for the third polishing can be 1100 meshes, 1200 meshes or 1300 meshes.

[0061] In the present invention, the rate of the third polishing is preferably 120 - 180 r / min. In a specific embodiment, the rate of the third polishing can be 120 r / min, 140 r / min, 160 r / min or 180 r / min; the time is preferably 2 - 4 min. In a specific embodiment, the time of the third polishing can be 2 min, 3 min or 4 min. In the present invention, the lubricant used for the third polishing is preferably water.

[0062] In the present invention, when the zirconium-vanadium-iron alloy is polished successively, the angle between the directions of different polishings is preferably 90°. By changing the polishing direction, the present invention eliminates the traces left by the previous sandpaper, obtains a smooth surface, and avoids repeated polishing in the same direction, which may lead to poor quality of the polished surface or even deepen the scratches.

[0063] In the present invention, it is preferably to wash the polished surface before changing the polishing direction.

[0064] In the present invention, the polishing preferably includes: successively performing the first polishing, the second polishing and the third polishing on the polished zirconium-vanadium-iron alloy to obtain the polished zirconium-vanadium-iron alloy.

[0065] In the present invention, the particle size of the polishing cloth and the polishing agent used for the first polishing is preferably 7 - 10 μm. In a specific embodiment, the particle size of the polishing cloth and the polishing agent used for the first polishing can be 7 μm, 8 μm, 9 μm or 10 μm; the polishing agent used for the first polishing is preferably diamond suspension.

[0066] In the present invention, the rate of the first polishing is preferably 120 - 180 r / min. In a specific embodiment, the rate of the first polishing can be 120 r / min, 140 r / min, 160 r / min, or 180 r / min; the time is preferably 4 - 8 min, and in a specific embodiment, the time of the first polishing can be 4 min, 6 min, or 8 min. In the present invention, the lubricant used for the first polishing is preferably MetaDi aqueous suspension. The lubricant can avoid excessive astringency during polishing.

[0067] In the present invention, the particle size of the polishing cloth and polishing agent used for the second polishing is preferably 2 - 4 μm. In a specific embodiment, the particle size of the polishing cloth and polishing agent used for the second polishing can be 2 μm, 3 μm, or 4 μm; the polishing agent used for the second polishing is preferably MetaDi polishing liquid.

[0068] In the present invention, the rate of the second polishing is preferably 120 - 180 r / min. In a specific embodiment, the rate of the second polishing can be 120 r / min, 140 r / min, 160 r / min, or 180 r / min; the time is preferably 2 - 5 min, and in a specific embodiment, the time of the second polishing can be 2 min, 3 min, 4 min, or 5 min. In the present invention, the lubricant used for the second polishing is preferably MetaDi aqueous suspension.

[0069] In the present invention, the particle size of the polishing cloth and polishing agent used for the third polishing is preferably 0.02 - 0.1 μm. In a specific embodiment, the particle size of the polishing cloth and polishing agent used for the third polishing can be 0.02 μm, 0.05 μm, 0.08 μm, or 0.1 μm; the polishing agent used for the third polishing is preferably alumina suspension.

[0070] In the present invention, the rate of the third polishing is preferably 120 - 180 r / min. In a specific embodiment, the rate of the third polishing can be 120 r / min, 140 r / min, 160 r / min, or 180 r / min; the time is preferably 4 - 8 min, and in a specific embodiment, the time of the third polishing can be 4 min, 6 min, or 8 min. In the present invention, the lubricant used for the third polishing is preferably water. Specifically, water is dripped evenly during the polishing process.

[0071] In the present invention, it is preferred to spray the polishing agent once per minute during polishing.

[0072] Through polishing in the present invention, the polished surface becomes smoother, showing a mirror-like effect, which is convenient for observing the metallographic structure by corrosion.

[0073] In the present invention, after polishing, it preferably further includes cleaning and drying the polished surface to obtain a zirconium-vanadium-iron alloy sample.

[0074] In the present invention, the cleaning preferably includes water washing and alcohol wiping.

[0075] The present invention has no special requirements for the method of drying, and well-known technical means in the art can be adopted.

[0076] After obtaining the zirconium-vanadium-iron alloy sample, the present invention immerses the polished surface of the zirconium-vanadium-iron alloy sample with the metallographic etchant for etching.

[0077] In the present invention, the immersion time is preferably 20 - 70 s. In specific embodiments, the immersion time can be 20 s, 30 s, 40 s, 50 s, 60 s or 70 s.

[0078] In the present invention, the immersion method is preferably: dropping the metallographic etchant onto the polished surface of the zirconium-vanadium-iron alloy sample until the polished surface is completely immersed.

[0079] In the present invention, corrosion occurs by immersing the polished surface of the zirconium-vanadium-iron alloy sample with the metallographic etchant. Specifically, hydrochloric acid and nitric acid in the metallographic etchant react with metal ions on the surface of the zirconium-vanadium-iron alloy specimen to form compounds and dissolve, thereby revealing the microstructure of the metal. Among them, iron reacts with hydrochloric acid to produce hydrogen and ferrous salts, and nitric acid reacts with zirconium to produce zirconium nitrate, which dissolves in nitric acid.

[0080] After completing the etching, the present invention preferably further includes water washing and drying the etched zirconium-vanadium-iron alloy sample.

[0081] In the present invention, the water washing is preferably carried out by rinsing with running water, and the water washing time is preferably 1 - 2 min.

[0082] In the present invention, the drying is preferably carried out by blowing dry with compressed air.

[0083] In the present invention, after drying, it is preferably further included to microscopically observe the obtained dried metallographic sample.

[0084] The present invention has no special requirements for the method of microscopic observation, and well-known technical means in the art can be adopted.

[0085] The metallographic display method of the zirconium-vanadium-iron alloy provided by the present invention forms a well-etched metallographic sample by successively grinding, polishing, and immersing the zirconium-vanadium-iron alloy. By combining a specific metallographic etchant with other specific processes, good overall interaction is achieved, and the grain boundaries and microstructure of the zirconium-vanadium-iron alloy can be clearly shown, thereby more accurately determining the grain size and reflecting the characteristics of the material itself.

[0086] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions of the present invention in conjunction with specific embodiments. The described embodiments are only a part of the embodiments of the present invention, rather than all of them. Any modifications, equivalent replacements, improvements, etc. made to the embodiments of the present invention without creative efforts based on the technical essence and general principles of the present invention shall fall within the protection scope of the present invention.

[0087] Example 1

[0088] 70 wt% concentrated nitric acid and 38 wt% concentrated hydrochloric acid were successively added to pure water and mixed evenly to obtain a metallographic etching solution. The volume ratio of concentrated hydrochloric acid, concentrated nitric acid, and water was 1:1:2.

[0089] The zirconium-vanadium-iron alloy was cut into square specimens with dimensions of 10 mm × 10 mm × 20 mm. The specimens were placed in an embedding machine and filled with an embedding material (a metallographic embedding material, Jia, the main component being resin powder), and heated and cured.

[0090] Using water as a wetting agent, with the 10 mm × 20 mm surface of the specimen as the grinding surface, it was ground on 180-mesh sandpaper at 500 r / min for 30 s, the specimen was cleaned with water, and the grinding direction of the specimen was rotated by 90°. Then it was ground on 400-mesh sandpaper at 150 r / min for 3 min, the specimen was cleaned with water, and the grinding direction of the specimen was rotated by 90°. It was ground on 150-mesh sandpaper at 150 r / min for 3 min to obtain the ground specimen.

[0091] Using MetaDi water-based suspension as a lubricant, 9-μm polishing agent ( Jia, 9-μm diamond suspension) was added to a 9-μm polishing cloth, and polished at 150 r / min for 6 min, spraying the polishing agent once per minute; using MetaDi water-based suspension as a lubricant, 3-μm polishing agent (MetaDi polishing solution) was added to a 3-μm polishing cloth, and polished at 150 r / min for 4 min, spraying the polishing agent once per minute; 0.05-μm polishing agent (MasterPrep alumina suspension) was added to a 0.05-μm polishing cloth and water droplets were evenly dripped, and polished at 150 r / min for 6 min, spraying the polishing agent once per minute. The specimen was cleaned with water to obtain the polished specimen, and the surface of the specimen showed an obvious mirror surface and no scratches.

[0092] The polished specimen was wiped with alcohol and dried. The metallographic etching solution was dropped onto the polished surface of the polished specimen until the polished surface was completely immersed, immersed for 1 min, washed with water for 1 min, and dried with compressed air to obtain the metallograph.

[0093] For the metallograph obtained in Example 1 at 200 magnifications ( Figure 1in a)), 500 times ( Figure 1 in b)) and 1000 times ( Figure 1 Observation under a metallographic microscope in c)) gave Figure 1 . Clear corresponding metallographic structure and grain boundaries can be observed from the figure.

[0094] Example 2

[0095] 70 wt% concentrated nitric acid and 38 wt% concentrated hydrochloric acid were successively added to pure water and mixed evenly to obtain a metallographic etching solution, and the volume ratio of concentrated hydrochloric acid, concentrated nitric acid and water was 1:2:4.

[0096] The metallographic etching solution was dropped onto the polished surface of the polished sample until the polished surface was completely immersed, and it was immersed for 0.5 min. Other conditions were the same as those in Example 1.

[0097] The metallographic sample obtained in Example 2 was observed under a metallographic microscope at 200 times magnification, and Figure 2 . Clear corresponding metallographic structure and grain boundaries can be observed from the figure.

[0098] Example 3

[0099] 70 wt% concentrated nitric acid and 38 wt% concentrated hydrochloric acid were successively added to pure water and mixed evenly to obtain a metallographic etching solution, and the volume ratio of concentrated hydrochloric acid, concentrated nitric acid and water was 2:3:6.

[0100] The metallographic etching solution was dropped onto the polished surface of the polished sample until the polished surface was completely immersed, and it was immersed for 0.5 min. Other conditions were the same as those in Example 1.

[0101] The metallographic sample obtained in Example 3 was observed under a metallographic microscope at 200 times magnification, and Figure 3 . Clear corresponding metallographic structure and grain boundaries can be observed from the figure.

[0102] Comparative Example 1

[0103] 38 wt% concentrated hydrochloric acid and 40 wt% hydrofluoric acid were added to pure water and mixed evenly to obtain a metallographic etching solution, and the volume ratio of concentrated hydrochloric acid, hydrofluoric acid and water was 1:1:2.

[0104] The metallographic etching solution was dropped onto the polished surface of the polished sample until the polished surface was completely immersed, and it was immersed for 0.5 min. Other conditions were the same as those in Example 1.

[0105] The metallographic sample obtained in Comparative Example 1 was observed under a metallographic microscope at 200 times magnification, and Figure 4 . It can be seen from the figure that the etching solution used in Comparative Example 1 has too fast an etching rate, the surface of the sample has been etched black, the etching degree is not easy to control, and the surface grain boundaries and structure of the zirconium-vanadium-iron alloy cannot be etched out.

[0106] Comparative Example 2

[0107] 38 wt% concentrated hydrochloric acid and 98 wt% concentrated sulfuric acid were added to pure water and mixed evenly to obtain a metallographic etching solution, and the volume ratio of concentrated hydrochloric acid, concentrated sulfuric acid and water was 1:1:2.

[0108] The metallographic etching solution was dropped onto the polished surface of the polished specimen until the entire polished surface was immersed, and it was immersed for 0.5 min. Other conditions were the same as those in Example 1.

[0109] The metallograph obtained in Comparative Example 2 was observed under a metallographic microscope with a magnification of 200 times, and Figure 5 was obtained. It can be seen from the figure that the crystal plane change of the zirconium-vanadium-iron alloy after corrosion is incomplete, and the metallographic structure and grain boundaries do not appear in some areas.

[0110] Comparative Example 3

[0111] 40 wt% hydrofluoric acid and 70 wt% concentrated nitric acid were added to pure water and mixed evenly to obtain a metallographic etching solution, and the volume ratio of hydrofluoric acid, concentrated nitric acid and water was 1:1:2. Other conditions were the same as those in Example 1.

[0112] The metallograph obtained in Comparative Example 3 was observed under a metallographic microscope with a magnification of 200 times, and Figure 6 was obtained. It can be seen from the figure that the crystal plane change of the zirconium-vanadium-iron alloy after corrosion is not obvious, and the metallographic structure and grain boundaries do not appear.

[0113] The above are only the preferred embodiments of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A metallographic etching agent, characterized in that: It comprises hydrochloric acid, nitric acid and water, wherein the volume ratio of the hydrochloric acid to the nitric acid is 1-2:1-3; The volume ratio of hydrochloric acid to water is 1-2:2-6; The mass concentration of the hydrochloric acid is 36-38wt%; The mass concentration of the nitric acid is 60-70wt%.

2. The metallographic etching agent according to claim 1, characterized in that: The volume ratio of hydrochloric acid to nitric acid is 1:1-2; The volume ratio of the hydrochloric acid to water is 1:2-4.

3. The method for preparing the metallographic etching agent according to any one of claims 1 to 2, characterized in that: The method comprises the following steps: adding hydrochloric acid and nitric acid into water and mixing them to obtain the metallographic etching agent.

4. A metallographic display method of zirconium-vanadium-iron alloy, characterized in that: The method comprises the following steps: immersing the polished surface of the zirconium-vanadium-iron alloy sample with the metallographic etching agent described in any one of claims 1 to 2 or the metallographic etching agent prepared by the preparation method described in claim 3 to perform etching.

5. The metallographic display method according to claim 4, characterized in that: The immersion time is 20 to 70 seconds.

6. The metallographic display method according to claim 4, characterized in that: The preparation of the zirconium-vanadium-iron alloy sample comprises: inlaying, grinding and polishing the zirconium-vanadium-iron alloy in sequence to obtain the zirconium-vanadium-iron alloy sample.

7. The metallographic display method according to claim 4 or 5, characterized in that: The method further comprises washing and drying the corroded zirconium-vanadium-iron alloy sample after the corrosion.

8. The metallographic display method according to claim 7, characterized in that: After the drying, the method further includes subjecting the obtained dried metallographic sample to microscopic observation.

9. The metallographic display method according to claim 6, characterized in that: The grinding comprises: sequentially performing a first grinding, a second grinding and a third grinding on the embedded zirconium-vanadium-iron alloy; The mesh number of the sandpaper used for the first grinding is 160 to 200 meshes; The mesh number of the sandpaper used for the second grinding is 380-420 mesh; The mesh number of the sandpaper used for the third grinding is 1100-1300 mesh; When the zirconium-vanadium-iron alloy is polished sequentially, the angle between different polishing directions is 90 degrees.

10. The metallographic display method according to claim 6, characterized in that: The polishing comprises: sequentially performing a first polishing, a second polishing and a third polishing on the ground zirconium-vanadium-iron alloy; The particle size of the polishing cloth and polishing agent used in the first polishing is 7 to 10 μm; The particle size of the polishing cloth and polishing agent used in the second polishing is 2 to 4 μm; The particle size of the polishing cloth and the polishing agent used in the third polishing is 0.02-0.1 μm.

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