Metallographic corrosion method and grain size detection method of chromium-silicon alloy target material

Abstract

The invention provides a metallographic corrosion method and a grain size detection method for a chromium-silicon alloy target material, and the metallographic corrosion method comprises the following steps: sequentially polishing and cleaning the surface of a chromium-silicon alloy target material sample to obtain a pretreated alloy target material; sequentially corroding the pretreated alloy target material by using hydrochloric acid and hydrofluoric acid, wherein the hydrofluoric acid is added on the basis of the hydrochloric acid; and washing and drying the corroded alloy target material to obtain the chromium-silicon alloy target material to be detected. Metallographic corrosion is carried out on the chromium-silicon alloy target material, hydrochloric acid and hydrofluoric acid are sequentially adopted as corrosive liquid, corrosion process parameters, inorganic acid types and the use sequence are selected, the corrosion effect is improved, the internal structure of the chromium-silicon alloy target material is exposed, the grain size is detected in cooperation with detection equipment, and improvement of the sputtering performance of the target material is facilitated. The uniformity of the sputtering film and the consistency of the quality of batch products are improved; the method is simple to operate, high in sample preparation speed, high in detection result accuracy and low in operation cost.

Description

Technical Field

[0001] The invention belongs to the technical field of target material detection, and relates to a metallographic corrosion method and a grain size detection method of a chromium-silicon alloy target material. Background Art

[0002] The internal structure of metal materials is closely related to material properties such as hardness, strength, and ductility, and metallographic observation is an effective method to study the internal structure of metal materials. Taking metal or alloy targets as an example, the size of the grains in the target will directly affect the sputtering rate during target coating. The smaller the grains, the faster the sputtering rate, and the more uniform the grain size, the more uniform the thickness distribution of the deposited film. Because atoms at the grain boundaries are easier to peel off and etch than atoms within the grains during sputtering, and fine grains have more grain boundaries, metal targets with fine grains are beneficial to improving the deposition efficiency of sputtered films. Given that the grain size in the target is usually small, how to detect the target grain size and morphology is a key technical difficulty in the target industry.

[0003] Alloy targets are an important component of existing target materials, and are mostly made of a mixture of two or more metals and metals or metals and non-metals. In order to detect the grain size within the target material, its internal structure needs to be exposed, and it is necessary to use a corrosive solution for corrosion. For targets with strong corrosion resistance, ordinary methods may not be able to etch clear grains, and it is necessary to select a suitable process combination based on the type of target material. Taking chromium-silicon alloy targets as an example, they usually have a variety of different crystal phases such as CrSi, CrSi2, Cr5Si3, and Si. The proportions of these phases are different, and the composition of the alloy target changes accordingly. In order to ensure its excellent performance during sputtering, the target material is required to have a high density, small and uniform grains. Due to its strong corrosion resistance, it is often difficult to achieve the ideal etching effect by directly using a single acid or mixed acid.

[0004] CN114509327A discloses a method for displaying the metallographic structure of a tantalum target. The method comprises: grinding, wherein the surface of the tantalum target is subjected to coarse grinding, fine grinding, and fine grinding using sandpaper of increasing particle size, until the crystal plane can be observed on the ground surface; polishing and cleaning, wherein the ground tantalum target is mechanically polished and cleaned; and etching, wherein the cleaned tantalum target is corroded by immersion or pouring, using a mixed solution of hydrofluoric acid, nitric acid, and sulfuric acid, followed by rinsing with water and anhydrous ethanol, drying, and observing under a metallographic microscope. This method is used to etch pure metal targets, rather than alloy targets containing non-metallic elements. The microstructures of the two are different, and the composition requirements of the etching solution are also different. The more types of mixed acid, the better. Different etching processes need to be selected according to the composition and characteristics of the target.

[0005] CN109211645A discloses a metallographic etchant for a chromium-tantalum-titanium alloy and a method for displaying its metallographic structure. The metallographic etchant is a mixed solution of hydrofluoric acid, sulfuric acid, nitric acid, and hydrochloric acid. The method comprises: providing a chromium-tantalum-titanium alloy sample, performing surface treatment on the alloy sample to form at least one polished surface, and etching the polished surface of the alloy sample using the metallographic etchant. The pure metal alloy sample in this method is a corrosion-resistant polycrystalline alloy. The etchant used is a mixed solution of four inorganic acids, which has high requirements for the acid solution. The crystalline structure of alloys containing non-metallic elements such as silicon is different, and the type of acid solution required for metallographic display is also different. Improper use can cause excessive corrosion of the target material, making it impossible to effectively observe and detect the microscopic morphology.

[0006] In summary, for the metallographic etching process of chromium-silicon alloy targets, it is necessary to select a suitable etching process according to the composition of the alloy target, so that the internal structure of the target can be clearly revealed, which is convenient for subsequent grain size detection. Summary of the Invention

[0007] In response to the problems existing in the prior art, the purpose of the present invention is to provide a metallographic corrosion method and grain size detection method for a chromium-silicon alloy target. The method uses an inorganic acid to corrode the chromium-silicon alloy target according to its composition. By controlling the corrosion process parameters and the composition of the etching liquid, the internal microstructure is revealed, which facilitates the detection of the grain size and helps to improve the subsequent target sputtering application performance.

[0008] To achieve this object, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides a metallographic etching method for a chromium-silicon alloy target, the metallographic etching method comprising the following steps:

[0010] (1) polishing and cleaning the surface of a chromium-silicon alloy target sample in sequence to obtain a pretreated alloy target;

[0011] (2) etching the alloy target material pretreated in step (1) with hydrochloric acid and hydrofluoric acid in sequence, wherein the hydrofluoric acid is added on the basis of the hydrochloric acid;

[0012] (3) The alloy target material corroded in step (2) is rinsed and dried to obtain the chromium-silicon alloy target material to be tested.

[0013] In the present invention, based on the requirement that the target material needs to have its internal microstructure and grain size characteristics clarified before application, since the proportion of silicon in the chromium-silicon alloy target material is different, there are usually multiple different crystal phases therein, and there is an oxide film on the surface, which has strong corrosion resistance. Therefore, when the target material is subjected to metallographic etching in the present invention, after surface pretreatment such as polishing and cleaning, hydrochloric acid has good corrosion resistance to Cr. At room temperature, Si is only corroded by hydrofluoric acid, but hydrofluoric acid accelerates the formation of an oxide film on Cr, making it less susceptible to corrosion. Therefore, hydrofluoric acid must be added when etching CrSi. However, in order to avoid the oxide film covering the sample surface from thickening and causing corrosion difficulties, hydrochloric acid must be added first to destroy the oxide film and make it disappear. After adding hydrofluoric acid, the newly generated oxide film is difficult to completely cover the sample surface again due to the reaction while it is being generated, so the etching can be completed quickly. Therefore, in the present invention, the two are added sequentially instead of being added together with mixed acid, which helps to improve the corrosion effect and reveal its internal structure. The target material grain size is then detected with the help of detection equipment, which helps to improve the sputtering performance of the target material and improve the uniformity of the sputtered film and the consistency of the quality of batch products. The method is simple to operate, fast in sample preparation, highly accurate in detection results, and low in operating cost.

[0014] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. Through the following technical solutions, the technical objectives and beneficial effects of the present invention can be better achieved and realized.

[0015] As a preferred technical solution of the present invention, the silicon content in the chromium-silicon alloy target in step (1) is 10 to 90 wt%, for example, 10 wt%, 11 wt%, 12 wt%, 15 wt%, 18 wt%, 19 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, 55 wt%, 60 wt%, 70 wt%, 80 wt% or 90 wt%, etc., but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0016] Preferably, the crystalline phase in the chromium-silicon alloy target in step (1) includes any one or a combination of at least two of CrSi, CrSi2, Cr5Si3 or Cr3Si. Typical but non-limiting examples of the combinations include: a combination of CrSi and CrSi2, a combination of CrSi2 and Cr5Si3, a combination of CrSi, CrSi2 and Cr3Si, a combination of CrSi, CrSi2, Cr5Si3 and Cr3Si, etc.

[0017] Preferably, the chromium-silicon alloy target material sample in step (1) is a sample cut from the target material by machining.

[0018] As a preferred technical solution of the present invention, step (1) polishes the test surface of the target sample.

[0019] Preferably, the polishing in step (1) includes polishing with sandpaper, or polishing with a combination of sandpaper and polishing liquid.

[0020] Preferably, the sandpaper polishing includes polishing in the order of 240 mesh, 1000 mesh and 2000 mesh.

[0021] Preferably, the polishing liquid contains diamonds with a particle size of ≤3 μm, for example, 3 μm, 2.9 μm, 2.7 μm, 2.5 μm, 2.2 μm, 2.0 μm, 1.9 μm, 1.8 μm, 1.7 μm, 1.5 μm or 1.0 μm.

[0022] As a preferred technical solution of the present invention, the cleaning medium used in step (1) includes water and / or alcohol.

[0023] Preferably, the cleaning method in step (1) includes flushing and / or ultrasonic cleaning.

[0024] Preferably, the roughness of the target sample surface after polishing and cleaning in step (1) is 0.05 to 2 μm, for example, 0.05 μm, 0.06 μm, 0.1 μm, 0.2 μm, 0.5 μm, 0.8 μm, 1 μm, 1.2 μm, 1.5 μm, 1.6 μm or 2.0 μm, etc., but is not limited to the listed values, and other unlisted values within this numerical range are also applicable.

[0025] As a preferred technical solution of the present invention, the mass fraction of the hydrochloric acid in step (2) is 20 to 38 wt%, for example, 20 wt%, 22 wt%, 23 wt%, 25 wt%, 28 wt%, 30 wt%, 32 wt%, 35 wt% or 38 wt%, etc., but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0026] Preferably, the mass fraction of the hydrofluoric acid in step (2) is 20 to 48 wt%, for example, 20 wt%, 22 wt%, 23 wt%, 25 wt%, 28 wt%, 29 wt%, 30 wt%, 32 wt%, 33 wt%, 35 wt%, 38 wt%, 40 wt%, 42 wt%, 43 wt%, 45 wt% or 48 wt%, etc., but is not limited to the listed values, and other values not listed within this numerical range are equally applicable.

[0027] Preferably, the hydrochloric acid and hydrofluoric acid in step (2) are added dropwise onto the test surface of the target sample.

[0028] As a preferred technical solution of the present invention, after the hydrochloric acid is added dropwise in step (2), hydrofluoric acid is added dropwise to the hydrochloric acid to continue etching. The total etching time is 10s to 600s, for example, it can be 10s, 20s, 50s, 60s, 100s, 120s, 150s, 200s, 250s, 300s, 400s, 450s, 500s, 550s or 600s, etc.

[0029] In the present invention, the etching time is adjusted and controlled according to factors such as the composition and content of the alloy target and the concentration of the acid. The lower the acid concentration, the longer the etching time required. Taking pure hydrofluoric acid and pure hydrochloric acid as examples, the etching time is between 20 and 60 seconds.

[0030] Preferably, the interval between the dropwise addition of hydrochloric acid and hydrofluoric acid is 5 to 10 seconds, for example, 5 seconds, 6 seconds, 7 seconds, 8 seconds, 9 seconds or 10 seconds.

[0031] Preferably, the volume ratio of hydrochloric acid and hydrofluoric acid in step (2) is 1:(0.3-3), for example, 1:0.3, 1:0.5, 1:0.8, 1:1, 1:1.5, 1:2, 1:2.5 or 1:3, etc., but is not limited to the listed values, and other unlisted values within this numerical range are also applicable.

[0032] In this invention, the volume ratio of hydrochloric acid to hydrofluoric acid is a key factor influencing the corrosion effect. If the hydrochloric acid ratio is too high and the hydrofluoric acid ratio is too low, the corrosion effect will be insufficient, making it difficult to detect and obtain metallographic images. On the other hand, if the hydrochloric acid ratio is too low and the hydrofluoric acid ratio is too high, excessive corrosion will occur, resulting in damage to the metallographic structure. Generally speaking, for Cr-50wt% Si samples, a volume ratio of hydrochloric acid to hydrofluoric acid of 1:1 is sufficient.

[0033] As a preferred technical solution of the present invention, the rinsing in step (3) includes rinsing with deionized water and rinsing with alcohol in sequence.

[0034] As a preferred technical solution of the present invention, the drying method in step (3) includes air drying.

[0035] In another aspect, the present invention provides a method for detecting the grain size of a chromium-silicon alloy target, the method comprising:

[0036] The metallographic structure of the surface of the chromium-silicon alloy target material to be tested is exposed by the metallographic etching method described in the first aspect, and the grain size of the exposed part is tested.

[0037] As a preferred technical solution of the present invention, the equipment used for grain size detection includes a scanning electron microscope or a metallographic microscope.

[0038] Preferably, the grain size of the chromium-silicon alloy target is 3 to 50 μm or less, for example, 50 μm, 45 μm, 40 μm, 35 μm, 30 μm, 25 μm, 20 μm, 15 μm, 10 μm, 8 μm or 5 μm, etc., but is not limited to the listed values, and other unlisted values within this numerical range are also applicable.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] (1) The method of the present invention performs metallographic etching on a chromium-silicon alloy target material, using hydrochloric acid and hydrofluoric acid as etching solutions in sequence. By selecting etching process parameters, types of inorganic acids, and the order of use, the etching effect is improved, and the internal structure is revealed without damaging the metallographic structure. The target material grain size is then detected in conjunction with a detection device, which helps improve the target material sputtering performance, improve the uniformity of the sputtered film, and improve the consistency of the quality of batch products.

[0041] (2) The method of the present invention is simple to operate, has a fast sample preparation speed, high accuracy of detection results, and low operating cost. DETAILED DESCRIPTION

[0042] To better illustrate the present invention and facilitate understanding of the technical solution of the present invention, the present invention is further described in detail below. However, the following embodiments are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0043] The specific embodiment of the present invention provides a metallographic etching method for a chromium-silicon alloy target, which comprises the following steps:

[0044] (1) polishing and cleaning the surface of a chromium-silicon alloy target sample in sequence to obtain a pretreated alloy target;

[0045] (2) etching the alloy target material pretreated in step (1) with hydrochloric acid and hydrofluoric acid in sequence, wherein the hydrofluoric acid is added on the basis of the hydrochloric acid;

[0046] (3) The alloy target material corroded in step (2) is rinsed and dried to obtain the chromium-silicon alloy target material to be tested.

[0047] The following are typical but non-limiting examples of the present invention:

[0048] Example 1

[0049] This embodiment provides a metallographic etching method and a grain size detection method for a chromium-silicon alloy target. The metallographic etching method includes the following steps:

[0050] (1) polishing and cleaning the surface of a chromium-silicon alloy target sample in sequence, wherein the silicon content in the chromium-silicon alloy target is 80 wt %, and the chromium-silicon alloy target sample is a sample cut from the target by machining, and polishing the test surface of the target sample using sandpaper as a polishing medium, wherein the sandpaper polishing includes grinding and polishing in the order of 240 mesh, 1000 mesh, and 2000 mesh to obtain a pretreated alloy target, and at this time, the surface roughness Ra of the target sample is 1.5 μm;

[0051] (2) first, dripping 25 wt% hydrochloric acid onto the test surface of the target sample after the alloy target pretreated in step (1), and then dripping 35 wt% hydrofluoric acid onto the test surface of the target sample after an interval of 6 seconds, and continuing the etching for 550 seconds, wherein the volume ratio of the hydrochloric acid to the hydrofluoric acid is 1:2);

[0052] (3) The alloy target material corroded in step (2) is rinsed with deionized water and alcohol in sequence, and then air-dried to obtain a chromium-silicon alloy target material to be tested, wherein the metallographic structure is exposed on the surface of the chromium-silicon alloy target material to be tested, and the grain size of the exposed part is detected using a scanning electron microscope.

[0053] The metallographic etching method provided in this embodiment provides a clear metallographic structure during subsequent testing, clearly showing the presence of CrSi phase, CrSi2 phase, Cr5Si3 phase, and Cr3Si phase, and the grain size is also very clear. This demonstrates that the metallographic etching method provided in this embodiment can clearly and accurately display the metallographic structure and grain size.

[0054] Example 2

[0055] This embodiment provides a metallographic etching method and a grain size detection method for a chromium-silicon alloy target. The metallographic etching method includes the following steps:

[0056] (1) polishing and cleaning the surface of a chromium-silicon alloy target sample in sequence, wherein the silicon content in the chromium-silicon alloy target is 10 wt %, and the chromium-silicon alloy target sample is a sample cut from the target by machining, and polishing the test surface of the target sample using sandpaper as a polishing medium, wherein the sandpaper polishing includes grinding and polishing in the order of 240 mesh, 1000 mesh, and 2000 mesh to obtain a pretreated alloy target, and at this time, the surface roughness Ra of the target sample is 2 μm;

[0057] (2) first, dripping 38 wt% hydrochloric acid onto the test surface of the target sample after the alloy target pretreated in step (1), and then dripping 48 wt% hydrofluoric acid onto the test surface of the target sample after a 5-second interval, and continuing to etch for 10 seconds, wherein the volume ratio of hydrochloric acid to hydrofluoric acid is 1:1;

[0058] (3) The alloy target material corroded in step (2) is rinsed with deionized water and alcohol in sequence, and then air-dried to obtain a chromium-silicon alloy target material to be tested, wherein the metallographic structure is exposed on the surface of the chromium-silicon alloy target material to be tested, and the grain size of the exposed part is detected using a scanning electron microscope.

[0059] The metallographic etching method provided in this embodiment provides a clear metallographic structure during subsequent testing, clearly showing the presence of CrSi phase, CrSi2 phase, Cr5Si3 phase, and Cr3Si phase, and the grain size is also very clear. This demonstrates that the metallographic etching method provided in this embodiment can clearly and accurately display the metallographic structure and grain size.

[0060] Example 3

[0061] This embodiment provides a metallographic etching method and a grain size detection method for a chromium-silicon alloy target. The metallographic etching method includes the following steps:

[0062] (1) polishing and cleaning the surface of a chromium-silicon alloy target sample in sequence, wherein the silicon content in the chromium-silicon alloy target is 90 wt %, and the chromium-silicon alloy target sample is a sample cut from the target by machining, and polishing the test surface of the target sample using sandpaper as a polishing medium, wherein the sandpaper polishing includes grinding and polishing in the order of 240 mesh, 1000 mesh, and 2000 mesh, and then polishing with a polishing liquid containing diamond with a particle size of less than 1 μm to obtain a pretreated alloy target, wherein the surface roughness Ra of the target sample is 0.05 μm;

[0063] (2) first, dripping 20 wt% hydrochloric acid onto the test surface of the target sample after the alloy target pretreated in step (1), and then dripping 20 wt% hydrofluoric acid onto the test surface of the target sample after a 10 s interval, and continuing the etching for 600 s, wherein the volume ratio of the hydrochloric acid to the hydrofluoric acid is 1:3;

[0064] (3) The alloy target material corroded in step (2) is rinsed with deionized water and alcohol in sequence, and then air-dried to obtain a chromium-silicon alloy target material to be tested, wherein the metallographic structure is exposed on the surface of the chromium-silicon alloy target material to be tested, and the grain size of the exposed part is detected using a scanning electron microscope.

[0065] The metallographic etching method provided in this embodiment provides a clear metallographic structure during subsequent testing, clearly showing the presence of CrSi phase, CrSi2 phase, Cr5Si3 phase, and Cr3Si phase, and the grain size is also very clear. This demonstrates that the metallographic etching method provided in this embodiment can clearly and accurately display the metallographic structure and grain size.

[0066] Comparative Example 1

[0067] This comparative example provides a metallographic etching method and a grain size detection method for a chromium-silicon alloy target. The metallographic etching method refers to the method in Example 1, with the only difference being that in step (2), hydrochloric acid and hydrofluoric acid are mixed and added together to the test surface of the target sample.

[0068] In this comparative example, since hydrochloric acid and hydrofluoric acid are mixed first and then corroded together, the corrosion rate is slow, the grain boundary is not clear, and the crystal phase interface is not clear during observation and detection.

[0069] Comparative Example 2

[0070] This comparative example provides a metallographic etching method and a grain size detection method for a chromium-silicon alloy target. The metallographic etching method refers to the method in Example 1, with the only difference being that in step (2), hydrofluoric acid is first added dropwise, and then hydrochloric acid is added dropwise.

[0071] In this comparative example, since hydrofluoric acid was added dropwise first, a Cr oxide film was formed on the surface of the target material, thereby inhibiting corrosion, resulting in unclear metallographic structure and unclear crystal phase interface.

[0072] Comparative Example 3

[0073] This comparative example provides a metallographic etching method and a grain size detection method for a chromium-silicon alloy target. The metallographic etching method refers to the method in Example 1, with the only difference being that hydrochloric acid is not added in step (2).

[0074] In this comparative example, since only hydrofluoric acid was added dropwise, a Cr oxide film was formed on the surface of the target material, thereby inhibiting corrosion, resulting in unclear metallographic structure and unclear crystal phase interface.

[0075] Comparative Example 4

[0076] This comparative example provides a metallographic etching method and a grain size detection method for a chromium-silicon alloy target. The metallographic etching method refers to the method in Example 1, with the only difference being that hydrofluoric acid is not added in step (2).

[0077] In this comparative example, since only hydrochloric acid was added dropwise, Si was difficult to be corroded, and the metallographic structure was not clear and the crystal phase interface was not clear.

[0078] Comparative Example 5

[0079] This comparative example provides a metallographic etching method and a grain size detection method for a chromium-silicon alloy target. The metallographic etching method refers to the method in Example 1, with the only difference being that the polishing in step (1) is not performed.

[0080] In this comparative example, since polishing was not performed, the metallographic structure after subsequent corrosion was still unclear and the crystal phase interface was not clear.

[0081] From the above embodiments and comparative examples, it can be seen that the method of the present invention performs metallographic etching on a chromium-silicon alloy target, successively using hydrochloric acid and hydrofluoric acid as etching solutions. By selecting the etching process parameters, the type of inorganic acid, and the order of use, it is helpful to improve the etching effect and reveal its internal structure. The target material grain size is then detected in conjunction with the detection equipment, which helps to improve the sputtering performance of the target material, improve the uniformity of the sputtered film, and improve the consistency of the quality of batch products. The method is simple to operate, has a fast sample preparation speed, highly accurate detection results, and low operating costs.

[0082] The applicant declares that the present invention uses the above-described embodiments to illustrate the detailed method of the present invention. However, the present invention is not limited to the above-described detailed method, that is, it does not mean that the present invention must rely on the above-described detailed method to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for the present method, addition of auxiliary steps, selection of specific methods, etc., are all within the scope of protection and disclosure of the present invention.

Claims

1. A metallographic etching method for a chromium-silicon alloy target, characterized in that: The metallographic corrosion method comprises the following steps: (1) polishing and cleaning the surface of a chromium-silicon alloy target sample in sequence to obtain a pretreated alloy target; (2) etching the alloy target material pretreated in step (1) with hydrochloric acid and hydrofluoric acid in sequence, wherein the hydrofluoric acid is added to the hydrochloric acid; (3) The alloy target material corroded in step (2) is rinsed and dried to obtain the chromium-silicon alloy target material to be tested.

2. The metallographic etching method according to claim 1, wherein: The silicon content in the chromium-silicon alloy target in step (1) is 10 to 90 wt %; Preferably, the crystalline phase in the chromium-silicon alloy target in step (1) includes any one or a combination of at least two of CrSi, CrSi2, Cr5Si3 or Cr3Si; Preferably, the chromium-silicon alloy target material sample in step (1) is a sample cut from the target material by machining.

3. The metallographic etching method according to claim 1 or 2, characterized in that: Step (1) polishing the test surface of the target sample; Preferably, the polishing in step (1) comprises polishing with sandpaper, or polishing with a combination of sandpaper and polishing liquid; Preferably, the sandpaper polishing includes polishing in the order of 240 mesh, 1000 mesh and 2000 mesh; Preferably, the polishing liquid contains diamonds with a particle size of ≤3 μm.

4. The metallographic etching method according to any one of claims 1 to 3, characterized in that: The cleaning medium in step (1) includes water and / or alcohol; Preferably, the cleaning method in step (1) includes flushing and / or ultrasonic cleaning.

5. The metallographic etching method according to any one of claims 1 to 4, characterized in that: The mass fraction of the hydrochloric acid in step (2) is 20 to 38 wt%; Preferably, the mass fraction of the hydrofluoric acid in step (2) is 20 to 48 wt%; Preferably, the hydrochloric acid and hydrofluoric acid in step (2) are added dropwise onto the test surface of the target sample.

6. The metallographic etching method according to any one of claims 1 to 5, characterized in that: The volume ratio of hydrochloric acid to hydrofluoric acid in step (2) is 1:(0.3-3).

7. The metallographic etching method according to any one of claims 1 to 6, characterized in that: The rinsing in step (3) includes rinsing with deionized water and rinsing with alcohol in sequence.

8. The metallographic etching method according to any one of claims 1 to 7, characterized in that: The drying method in step (3) includes air drying.

9. A method for detecting the grain size of a chromium-silicon alloy target, characterized in that: The detection method comprises: The metallographic structure of the surface of the chromium-silicon alloy target material to be tested is exposed by the metallographic etching method according to any one of claims 1 to 8, and the grain size of the exposed part is detected.

10. The detection method according to claim 9, characterized in that: The equipment used for the grain size detection includes a scanning electron microscope or a metallographic microscope; Preferably, the grain size of the chromium-silicon alloy target is 3 to 50 μm.