Method for detecting grain size of ultrathin steel strip by using transmission electron microscope

Abstract

The invention discloses a method for detecting the grain size of an ultrathin steel strip by using a transmission electron microscope, and belongs to the technical field of microscopic detection of metal materials. The method comprises the following steps: step a, taking three Fe-Ni ultrathin steel strip samples with the diameter of 3mm; b, preparing a 10% perchloric acid alcohol solution as an electrolyte; c, setting proper voltage, current and photosensitive stop values on an electrolytic double-spraying instrument, and performing electrolytic double-spraying thinning sample preparation on the sample at a certain cooling temperature; and step d, putting the thinned sample into a transmission electron microscope, and observing, collecting and measuring in an STEM mode. The invention aims to provide the method for detecting the grain size of the ultrathin steel strip by using the transmission electron microscope, and the method can clearly display the microstructure morphology and is simple to operate.

Description

Technical Field

[0001] The invention belongs to the technical field of microscopic detection of metal materials, and in particular relates to a method for detecting the grain size of an ultra-thin steel strip by using a transmission electron microscope. Background Art

[0002] Fe-Ni ultra-thin steel strip is an ultra-thin (0.01mm-0.1mm) alloy material with iron (Fe) and nickel (Ni) as the main components. It has many excellent properties such as corrosion resistance, high chemical stability, and high temperature resistance. It is widely used in aerospace, military industry, high-end electronics, new energy and other fields.

[0003] In some special applications, such as aerospace and energy, the grain size of Fe-Ni ultra-thin steel strips needs to be strictly controlled to meet specific performance requirements. However, due to the special nature of the material and its ultra-thin nature, when preparing the sample, the sample is glued to the sample holder with hot melt adhesive and then mechanically ground and polished using traditional metallographic sample preparation methods. The disadvantage of this method is that the sample will warp and become uneven during the grinding process. In addition, the steel is corrosion-resistant and conventional metallographic etchants cannot be used to etch out the microstructure, which makes subsequent metallographic microscopic observation difficult. The present invention addresses the problems of Fe-Ni ultra-thin steel strip sample preparation and corrosion difficulties and invents an effective microscopic detection method. The method can be well applied to the sample preparation and grain size display and measurement of Fe-Ni ultra-thin steel strips, and is simple and accurate. Summary of the Invention

[0004] Aiming at the problems of sample preparation and corrosion difficulty of Fe-Ni ultra-thin steel strip samples, the present invention aims to provide a method for detecting the grain size of ultra-thin steel strip using a transmission electron microscope, which can clearly display the microstructure morphology and is simple to operate.

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

[0006] The present invention provides a method for detecting the grain size of an ultra-thin steel strip using a transmission electron microscope, comprising:

[0007] Step a: Take three Φ3mm Fe-Ni ultra-thin steel strip samples;

[0008] Step b, preparing a 10% perchloric acid alcohol solution as an electrolyte;

[0009] Step c, setting appropriate voltage, current, and photosensitivity stop value on the electrolytic double-spray instrument, and performing electrolytic double-spray thinning on the sample at a certain cooling temperature;

[0010] Step d: Place the thinned sample into a transmission electron microscope and use the STEM mode for observation, collection, and measurement.

[0011] Furthermore, three Φ3 mm samples were punched out from the Fe-Ni ultra-thin steel strip using a disc punch.

[0012] Furthermore, liquid nitrogen is poured into the cooling tank of the electrolytic double-spray instrument to below the safe liquid level, and 10% perchloric acid alcohol solution is poured into the electrolytic tank to the safe liquid level.

[0013] Furthermore, set appropriate voltage, current, and temperature parameters: voltage is set between 20-30V, current is between 15-25mA, photosensitivity stop value is 500, and operating temperature is -19℃.

[0014] Furthermore, the electrolytic double-spray instrument is started, and the electrolyte is sprayed toward the sample from both sides to start the thinning process. When a transmission thin area appears in the center of the sample, the electrolytic double-spray is stopped.

[0015] Furthermore, the sample was taken out of the electrolyte, quickly rinsed with anhydrous ethanol, and dried to remove the residual electrolyte on the surface.

[0016] Furthermore, the electrolytic double-spray sample preparation time is 23s. The sample is thin in the middle and thick at the edge, and has a dimple shape as a whole, which is observed under a transmission electron microscope.

[0017] Compared with the prior art, the present invention has the following beneficial technical effects:

[0018] 1. By utilizing the ultra-thin characteristics of the ultra-thin steel strip, the metal sample preparation process of mechanical grinding and thinning in the early stage during the transmission electron microscope sample preparation process is eliminated, saving time;

[0019] 2. Since the sample does not need to be mechanically polished, the problem of sample warping and unevenness caused by human factors is avoided;

[0020] 3. The electrolytic double-spray parameters suitable for Fe-Ni ultra-thin steel strips were invented. Using this parameter for operation, the sample preparation effect is good, the sample micromorphology is clear, easy to observe, good to measure, and the operation is relatively simple. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The present invention will be further described below with reference to the accompanying drawings.

[0022] Figure 1 A sample prepared by the method of the present invention;

[0023] Figure 2 This is a picture of the grain morphology collected by the method of the present invention;

[0024] Figure 3 This is a picture of the grain morphology collected by the method of the present invention;

[0025] Figure 4 This is a picture of the grain morphology collected by the method of the present invention;

[0026] Figure 5 Metallographic images collected for traditional metallographic sample preparation. DETAILED DESCRIPTION

[0027] A method for detecting the grain size of an ultra-thin steel strip using a transmission electron microscope comprises:

[0028] 1. Use a disc punch to punch out three Φ3mm samples from the Fe-Ni ultra-thin steel strip;

[0029] 2. Pour liquid nitrogen into the cooling tank of the electrolytic double-spray instrument to below the safe liquid level, and pour 10% perchloric acid alcohol solution into the electrolytic cell to the safe liquid level;

[0030] 3. Set appropriate voltage, current, and temperature parameters. The voltage should be between 20-30V, the current between 15-25mA, the photosensitivity cutoff value at 500, and the operating temperature at -19°C.

[0031] 4. Fix the sample on the sample stage of the electrolysis double-spray instrument to ensure good contact between the sample and the electrode;

[0032] 5. Turn on the power and start the electrolytic double spray instrument. The electrolyte will be sprayed onto the sample from both sides to start the thinning process. When a thin transmission area appears in the center of the sample, stop the electrolytic double spray.

[0033] 6. Remove the sample from the electrolyte, quickly rinse with anhydrous ethanol, and dry it to remove the residual electrolyte on the surface;

[0034] 7. Place the prepared sample into the transmission electron microscope sample chamber and switch to STEM mode for observation, collection, and measurement.

[0035] Example 1

[0036] The method of the present invention is used to prepare samples of Fe-Ni ultra-thin steel strips. The electrolytic double-spray preparation time is 23 seconds. The sample is thin in the middle and thick at the edge, with a dimple shape as a whole. Under transmission electron microscopy, the thin area of the sample is large and uniform, without obvious defects and contamination. Under STEM mode, the austenite grain morphology can be fully displayed, and the grain boundaries are clear. Figure 1 and Figure 2 .

[0037] Comparative Example 1

[0038] The photosensitivity stop value was set to 500 on the electrolytic double-spray instrument, and then the transmission electron microscopy samples were prepared with other different working voltage and current parameters. The samples and image effects are shown in Figure Group 2.

[0039] Figure 3 The electrolytic double-spray instrument was set to operate at a voltage of 20 V, a current of 30 mA, and a temperature of -15°C. The electrolytic double-spray sample preparation time was 139 seconds. The sample had a residual oxide layer and obvious gaps, making it unusable.

[0040] Figure 4 The electrolytic double-spray instrument was set to operate at a voltage of 30 V, a current of 30 mA, and a temperature of -23°C. The electrolytic double-spray sample preparation time was 67 seconds. The thinning area of the sample was too small and uneven. The electron microscope image was unclear.

[0041] Comparative Example 2

[0042] The sample was not smooth after mechanical grinding and polishing by traditional metallographic sample preparation method. After etching with 4% nitric acid alcohol, the sample was observed under a metallographic microscope. The grains were blurred, the grain boundaries were not obvious, and the image effect was not ideal. Figure 5 .

[0043] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A method for detecting the grain size of an ultra-thin steel strip using a transmission electron microscope, characterized in that: include: Step a: Take three Φ3mm Fe-Ni ultra-thin steel strip samples; Step b, preparing a 10% perchloric acid alcohol solution as an electrolyte; Step c, setting appropriate voltage, current, and photosensitivity stop value on the electrolytic double-spray instrument, and performing electrolytic double-spray thinning on the sample at a certain cooling temperature; Step d: Place the thinned sample into a transmission electron microscope and use the STEM mode for observation, collection, and measurement.

2. The method for detecting the grain size of an ultra-thin steel strip using a transmission electron microscope according to claim 1, wherein: Use a disc punch to punch out three Φ3mm samples from the Fe-Ni ultra-thin steel strip.

3. The method for detecting the grain size of an ultra-thin steel strip using a transmission electron microscope according to claim 1, wherein: Pour liquid nitrogen into the cooling tank of the electrolytic double-spray instrument to below the safe liquid level, and pour 10% perchloric acid alcohol solution into the electrolytic tank to the safe liquid level.

4. The method for detecting the grain size of an ultra-thin steel strip using a transmission electron microscope according to claim 1, wherein: Set appropriate voltage, current, and temperature parameters: voltage is set between 20-30V, current is between 15-25mA, photosensitivity stop value is 500, and operating temperature is -19℃.

5. The method for detecting the grain size of an ultra-thin steel strip using a transmission electron microscope according to claim 1, wherein: Start the electrolytic double-spray instrument, spray the electrolyte onto the sample from both sides, and start the thinning process. When a transmission thin area appears in the center of the sample, stop the electrolytic double-spray.

6. The method for detecting the grain size of an ultra-thin steel strip using a transmission electron microscope according to claim 5, characterized in that: The sample was removed from the electrolyte, quickly rinsed with anhydrous ethanol, and dried to remove the residual electrolyte on the surface.

7. The method for detecting the grain size of an ultra-thin steel strip using a transmission electron microscope according to claim 1, 4 or 5, characterized in that: The electrolytic double-spray sample preparation time is 23s. The sample is thin in the middle and thick at the edge, and has a dimple shape as a whole. It is observed under a transmission electron microscope.

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