Preparation method of high-efficiency and low-damage Ni36 precision alloy as-cast transmission electron microscope sample

Abstract

The invention belongs to the technical field of material science and microscopic analysis, and designs an efficient and low-damage chip and a preparation method of a Ni36 precision alloy as-cast transmission electron microscope sample for the aviation field. The method comprises the following steps: cutting and polishing an as-cast metallographic specimen, corroding and thinning the as-cast metallographic specimen, preparing a wafer specimen, preparing an electrolyte, carrying out electrolytic double-spraying on the wafer specimen, and carrying out ion thinning on the electrolytic double-spraying specimen. The double-spray electrolyte is composed of 1000 mL of absolute ethyl alcohol and 25 mL to 30 mL of hydrochloric acid with the concentration of 36.0% to 38.0%. The Ni36 precision alloy as-cast transmission electron microscope sample used in the fields of chips and aviation is successfully prepared, the operation is simple, the sample preparation speed is high, the efficiency is high, and the internal microcosmic fine structure is low in damage.

Description

Technical Field

[0001] The present invention relates to the field of materials science and microanalysis technology, and specifically to a method for preparing Ni36 precision alloy cast transmission electron microscope samples for chips and aviation fields with high efficiency and low damage, especially for preparing high-corrosion-resistant, large-grain cast alloy samples with low damage to the material microstructure and the need for batch and rapid preparation. Background Art

[0002] Ni36 is a unique alloy material based on iron-nickel alloy, renowned for its excellent thermal expansion coefficient stability and high strength. Due to its exceptional physical and mechanical properties, Ni36 is widely used in aerospace, precision instrument manufacturing, electronics, and the military. The chemical composition of Ni36 alloy primarily consists of nickel, iron, and small amounts of carbon, silicon, and other elements. Nickel is the primary component of Ni36 Invar alloy, and its high content imparts excellent corrosion resistance and high-temperature stability. The microstructure of its as-cast structure (such as grains, precipitates, and defects) significantly influences its hot and cold processing. However, characterizing the fine microstructure of this material during research and development presents significant challenges, making the preparation of thin film samples with a good effective thin area for high-resolution transmission electron microscopy a technical challenge.

[0003] In early September 2019, rolling cracking occurred during the hot rolling production of Ni36, a precision alloy used in chips and aviation. The cause was suspected to be the presence of a ferrite film near the grain boundaries, which lowered the material's melting point. Microstructural characterization using a series of metallographic microscopes and scanning electron microscopes failed to reveal any suspicious film structures, necessitating observation using a transmission electron microscope (TEM). Transmission electron microscopy, with its resolution ranging from a few nanometers to subnanometers, is a key tool for studying material microstructures, particularly nanoscale precipitates. Observing the fine details of the as-cast grain boundaries of the precision alloy Ni36 and meeting the production schedule required not only high-quality detailed images but also the rapid and large-scale production of high-quality, low-damage TEM thin film samples.

[0004] Conventional electrolytic double-spray solutions and their electrolytic parameters failed to produce thin zones. Subsequently, ion thinning was employed, which not only resulted in lengthy sample preparation times and poor thinning results, but also introduced significant damage or deformation during the thinning process due to the high hardness and brittleness of the Ni36 cast material, affecting the accuracy of observations and significantly hindering the resolution of the hot-rolled cracking problem in the precision alloy Ni36. A new method was urgently needed to mass-produce large quantities of transmission samples with large thin zones and minimal damage.

[0005] The present invention aims to invent a method for preparing a Ni36 precision alloy as-cast transmission electron microscope specimen with high efficiency and low damage, aiming to solve the problems that the traditional electrolytic twin-jet method cannot prepare a high-quality, large-thin-area nano-scale thin film sample of Ni36 as-cast state, the sample preparation speed is slow, and the internal microscopic fine structure is damaged. This method can not only quickly and batch obtain an effective thin area of the precision alloy Ni36 in the as-cast state up to more than 5 μm, but also retain multiple grain boundaries for observing and studying the details at the grain boundaries. Summary of the Invention

[0006] The object of the present invention is to provide a method for preparing a Ni36 precision alloy as-cast transmission electron microscope specimen with high efficiency and low damage in view of the above problems.

[0007] The object of the present invention is achieved as follows: A method for preparing a Ni36 precision alloy as-cast transmission electron microscope specimen with high efficiency and low damage includes the following steps: Step 1: Cut a metallographic specimen from the Ni36 precision alloy ingot blank and perform manual grinding; Step 2: Cut a sheet specimen from the metallographic specimen after manual grinding, clean the surface oil stain and immerse it in aqua regia for corrosion thinning; Step 3: Manually grind the sample after corrosion thinning to prepare a Φ3mm round sample; Step 4: Place the round sample into an electrolytic twin-jet thinning instrument filled with electrolyte for electrolytic twin-jet thinning; Step 5: Place the round sample after electrolytic twin-jet thinning into a precision argon ion thinning instrument for further ion thinning to obtain a Ni36 precision alloy as-cast transmission electron microscope specimen.

[0008] In the said Step 1, a metallographic specimen with a size of (5~20)mm×(5~20)mm and a thickness of 10~20mm is taken from the Ni36 ingot blank, and then the cross-section of the specimen is polished on both sides in a circular motion successively with sandpapers of 10~50 meshes, 200~360 meshes and canvas, and the polishing direction each time is perpendicular to the previous one, and it is ensured that the scratches of the previous time cannot be seen on the cross-section each time. Finally, it is polished with a diamond polishing agent with a particle size of 4~6μm until the surface of the sample is mirror-like and there are no other foreign objects.

[0009] In the said Step 2, a sheet specimen with a thickness of 1.0~1.5mm is cut from both sides by a wire cutting machine, then the sheet specimen is immersed in clean anhydrous ethanol for ultrasonic cleaning for 30~50s. After cleaning the surface oil stain of the specimen, it is placed into a beaker filled with aqua regia and left static for 12~18min, taken out with tweezers, and immersed in clean anhydrous ethanol for cleaning 3~5 times, each time for 3~50s and then dried. Measure its thickness to reach the range of 100~150μm.

[0010] In Step 3, press the corroded and thinned sample with a rubber, gently press and rotate it on 2000 - 3500 - mesh sandpaper to double - side polish off the surface floating powder until the sample thickness is 65 - 90 μm. Use a circular punch to punch the 65 - 90 - μm - thick sample to obtain a Φ3 - mm circular sample.

[0011] In Step 4, place the circular sample into an electrolytic twin - jet thinning instrument filled with electrolyte for thinning for 50 - 70 s.

[0012] The electrolyte in Step 4 is a mixed solution prepared from 1000 mL of absolute ethanol and 25 - 30 mL of hydrochloric acid with a concentration of 36.0% - 38.0%.

[0013] The thinning process parameters in Step 4: the electrolytic voltage is 20 - 25 V, the electrolytic current is 50 - 60 mA during the twin - jet thinning process, and the working temperature of the electrolyte is - 12°C to - 18°C.

[0014] In Step 4, the sample after electrolytic twin - jet thinning for 50 - 70 s needs to be immersed in clean absolute ethanol, shaken for 10 - 15 s and then taken out and dried.

[0015] In Step 5, the dried electrolytic twin - jet thinned circular sample is further ion - thinned using a precision argon ion thinning instrument, and the ion - thinned sample is placed in a sample box for standby.

[0016] The particle thinning process parameters in Step 5: the left and right ion guns are inclined 5 - 7° relative to the horizontal line, the voltage is 4 - 5 keV, and the thinning time is 35 - 55 min.

[0017] The beneficial effects of the present invention are as follows: The present invention provides a method for preparing Ni36 precision alloy as - cast transmission electron microscope specimens for the chip and aviation fields, which is efficient and low - damage. It solves the problems that traditional electrolytic twin - jet methods cannot prepare high - quality, large - thin - area, slow - sample - preparation - speed, and nano - scale thin - film samples with damaged internal microscopic fine structures of Ni36 as - cast. It can prepare transmission electron microscope samples quickly and in large quantities, is efficient and low - damage, shortens the detection cycle, characterizes the details at the grain boundaries of the precision alloy Ni36 as - cast, meets the rhythm of the production site, and provides accurate basic experimental data for product research and development and process route improvement. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The present invention will be further described below with reference to the drawings.

[0019] Figure 1 It is a transmission electron microscope sample diagram of Ni36 as - cast prepared by the traditional process.

[0020] Figure 2 It is a transmission electron microscope sample diagram of Ni36 as - cast prepared in Example 1 of the present invention.

[0021] Figure 3 It is a detailed morphology map of the grain boundary of the as-cast Ni36 sample obtained in Embodiment 1 of the present invention.

[0022] Figure 4 It is a transmission electron microscope sample map of the as-cast Ni36 prepared in Embodiment 2 of the present invention.

[0023] Figure 5 It is a detailed morphology map of the grain boundary of the as-cast Ni36 sample obtained in Embodiment 2 of the present invention. Specific implementation manners

[0024] Based on the objective problems that occur during the thinning process of the transmission electron microscope sample of the precision alloy Ni36 as-cast used in the chip and aviation fields by conventional electrolytic twin-jet thinning, the present invention provides a method for preparing a transmission electron microscope sample of the Ni36 precision alloy as-cast for the chip and aviation fields, which is efficient and has low damage. It solves the problems that the preparation time of the as-cast Ni36 transmission thin film sample is long, the success rate of quantity is low, and the thin area is small, so that the as-cast grain boundary cannot be observed in a large range. The transmission sample prepared by this method can realize the rapid large-scale preparation of Ni36 as-cast transmission electron microscope samples with a large thin area, and realize the statistics and characterization of the analysis of nano-scale defect information at the grain boundary of the as-cast Ni36.

[0025] The present invention designs a method for preparing a transmission electron microscope sample of the Ni36 precision alloy as-cast for the chip and aviation fields, which is efficient and has low damage. It focuses on solving the problems that the traditional electrolytic twin-jet method cannot prepare high-quality, large-thin-area nano-scale thin film samples of Ni36 as-cast, the sample preparation speed is slow, and the internal microscopic fine structure is damaged. The preparation method provided by the present invention innovatively uses aqua regia corrosion thinning for most of the manual sample grinding in the traditional transmission sample preparation process, which is fast and has low damage. Coupled with the ion thinning process in the last short time, a transmission electron microscope sample of the Ni36 precision alloy as-cast for the chip and aviation fields with a large thin area and low damage is successfully obtained quickly and efficiently. It shortens the detection cycle, characterizes the details at the grain boundary of the precision alloy Ni36 as-cast, meets the rhythm of the production site, and provides accurate basic experimental data for product research and development and process route improvement.

[0026] A method for preparing a Ni36 precision alloy as-cast transmission electron microscope specimen with high efficiency and low damage, comprising the following steps: (1) cutting a metallographic specimen from a Ni36 precision alloy casting blank in the chip and aviation fields, and performing manual grinding; (2) cutting a sheet specimen from the metallographic specimen after manual grinding, cleaning the surface oil stain, and immersing it in aqua regia for corrosion thinning; (3) manually grinding the sample after corrosion thinning to prepare a Φ3mm round sample. (4) placing the Φ3mm round sample into an electrolytic twin-jet thinning instrument filled with electrolyte for electrolytic twin-jet thinning; (5) the electrolyte is a mixed solution prepared from 1000 mL of absolute ethanol and 25 mL to 30 mL of hydrochloric acid with a concentration of 36.0% to 38.0%; (6) placing the Φ3mm round sample after electrolytic twin-jet thinning into a precision argon ion thinning instrument for continuous ion thinning to obtain a Ni36 precision alloy as-cast transmission electron microscope specimen in the chip and aviation fields.

[0027] In the step (1), a metallographic specimen with a size of 20mm×20mm×10 - 20mm (thickness) is taken from the Ni36 casting blank, and then the cross-section of the specimen is polished in a circular motion on both sides successively with water-abrasive fine sandpapers of 10 - 50 meshes and 200 - 360 meshes and canvas, and the polishing direction each time is perpendicular to the previous one, and it is ensured that the scratches of the previous time cannot be seen on the cross-section each time. Finally, it is polished with a diamond polishing machine with a particle size of 4 - 6μm until the surface of the sample is mirror-like (roughness Ra≤0.8µm) and there are no other foreign objects.

[0028] In the step (2), a sheet specimen with a thickness of 1.0 - 1.5mm is cut on both sides by a wire cutting machine, and then the sheet specimen is immersed in clean absolute ethanol for ultrasonic cleaning for 30 - 50s. After cleaning the surface oil stain of the specimen, it is placed into a beaker filled with aqua regia and left static for 12 - 18min, taken out with polytetrafluoroethylene tweezers, and immersed in clean absolute ethanol for cleaning 3 - 5 times, each time for 30 - 50s, and then dried. The thickness is measured with a micrometer to reach 100 - 150μm.

[0029] In the step (3), the sample after corrosion thinning is pressed with a clean and flat rubber, and gently pressed and polished in a circular motion on both sides on 2500-mesh sandpaper to remove the surface floating powder until the sample thickness is 65 - 90μm. A Φ3mm round sample is punched from the 65 - 90μm thick sample with a round sample puncher.

[0030] In the step (4), the Φ3mm round sample is placed into an electrolytic twin-jet thinning instrument filled with electrolyte for thinning for 50 - 70s.

[0031] The electrolyte is a mixed solution prepared from 1000 mL of absolute ethanol and 25 mL to 30 mL of hydrochloric acid with a concentration of 36.0% to 38.0%.

[0032] In the step (4), the thinning process parameters are as follows: the electrolysis voltage is 20 - 25V, the electrolysis current during double-jet thinning is 50 - 60mA, and the working temperature of the electrolyte is -12°C to -18°C.

[0033] In the step (4), the sample after electrolytic double-jet thinning for 50 - 70s needs to be immersed in clean anhydrous ethanol, and the sample is gently shaken (i.e., shaken by driving the wrist joint) for 10 - 15s and then taken out and dried.

[0034] In the step (6), the dried electrolytic double-jet thinned Φ3mm wafer sample is further ion thinned using a precision argon ion thinner model 691, and the ion-thinned sample is placed in a sample box for standby.

[0035] In the step (6), the particle thinning process parameters are as follows: the left and right ion guns are inclined at 5 - 7° relative to the horizontal line, the voltage is 4 - 5keV, and the thinning time is 35 - 55min. Example 1

[0036] Preparation of Ni36 precision alloy as-cast transmission electron microscope specimens for the chip and aviation fields and detailed morphology at the grain boundaries of Ni36 as-cast specimens under the transmission electron microscope.

[0037] (1) Take 500mm×500mm×200mm Ni36 precision alloy as-cast specimens for the chip and aviation fields from the production site, and cut a metallographic specimen with dimensions of 20mm×20mm×15mm (thickness) from the specimen. Then, the cross-section of the specimen is polished on both sides in a circular motion successively with a 20-mesh grinding wheel, 320-mesh sandpaper, and canvas, and the grinding direction each time is perpendicular to the previous one, and it is ensured that the scratches from the previous time are not visible on the cross-section each time. Then, it is polished with a diamond polisher with a particle size of 5μm until the surface of the sample is mirror-like and there are no other foreign objects.

[0038] (2) On the sample processed in (1), a sheet specimen with a thickness of 1.2mm is cut using a wire cutting machine, and then the sheet specimen is immersed in clean anhydrous ethanol and ultrasonically cleaned for 35s. After cleaning the oil stain on the surface of the specimen, it is placed in a beaker containing aqua regia and left stationary for 15min, taken out with polytetrafluoroethylene forceps, and immersed in clean anhydrous ethanol for cleaning 3 times, each time for 40s, and then dried. The thickness is measured with a micrometer to reach 125μm.

[0039] (3) Press the 125μm-thick sample processed in (2) with a clean and flat rubber, and gently press and polish on both sides of the 2500-mesh sandpaper to remove the surface floating powder until the sample thickness is 80μm, and then punch the sample with a wafer puncher to obtain a Φ3mm wafer sample.

[0040] (4) The Φ3mm wafer sample obtained in (3) is placed in an electrolytic double-jet thinner containing electrolyte for thinning for 61s.

[0041] (5) The electrolyte in step (4) is a mixed solution prepared from 1000 mL of absolute ethanol and 26 mL of hydrochloric acid with a concentration of 36.0% - 38.0%.

[0042] (6) The electrolytic twin-jet parameters in step (4) are: electrolytic voltage of 22 V, electrolytic current of 58 mA during the twin-jet thinning process, and an electrolyte working temperature of -15 °C.

[0043] (7) Immerse the sample after 62 s of electrolytic twin-jet thinning in clean absolute ethanol, gently shake the sample for 13 s, then take it out and dry it.

[0044] (8) Further ion thin the sample obtained in (7) using a precision argon ion thinner model 691. The ion thinning parameters are: the left and right ion guns are inclined 6° relative to the horizontal line, voltage of 5 keV, and thinning time of 45 min. Put the ion-thinned sample into a sample box for later use. Example 2

[0045] Preparation of as-cast transmission electron microscopy specimens of Ni36 precision alloy for chip and aviation fields and detailed morphology at the grain boundaries of Ni36 as-cast specimens under transmission electron microscopy.

[0046] (1) Take 500 mm × 500 mm × 200 mm as-cast specimens of Ni36 precision alloy for chip and aviation fields from the production site, and cut a metallographic specimen with a thickness of 15 mm × 15 mm × 15 mm (thick) from this specimen. Then, successively polish the cross-section of the specimen with a 20-mesh grinding wheel, 320-mesh sandpaper, and canvas in a circular motion on both sides. Each time the polishing direction is perpendicular to the previous one, and ensure that the scratches from the previous time are not visible on the cross-section each time. Then, polish with a diamond polisher with a particle size of 6 μm until the sample surface is mirror-like and free of other foreign objects.

[0047] (2) On the sample processed in (1), use a wire cutting machine to cut a sheet specimen with a thickness of 1.0 mm. Then, immerse the sheet specimen in clean absolute ethanol for ultrasonic cleaning for 40 s. After cleaning the oil stain on the specimen surface, put it into a beaker containing aqua regia and let it stand for 13 min. Use polytetrafluoroethylene forceps to take it out, immerse it in clean absolute ethanol for cleaning 5 times, 30 s each time, then dry it. Measure its thickness with a micrometer to reach 120 μm.

[0048] (3) Press the 120-μm-thick sample processed in (2) with a clean and flat rubber, gently press and polish it in a circular motion on both sides on 3000-mesh sandpaper to remove the surface floating powder until the sample thickness is 70 μm. Use a round punch to punch the sample to obtain a Φ3-mm round sample.

[0049] (4) The Φ3 mm disc sample obtained in (3) was placed in an electrolytic double-spray thinning instrument containing electrolyte and thinned for 55 seconds.

[0050] (5) The electrolyte in step (4) is a mixed solution prepared by 1000 mL of anhydrous ethanol and 30 mL of hydrochloric acid with a concentration of 36.0% to 38.0%.

[0051] (6) The electrolysis double-spray parameters in step (4) are as follows: electrolysis voltage of 20 V, electrolysis current of 55 mA during double-spray thinning, and electrolyte working temperature of -17°C.

[0052] (7) Immerse the sample after electrolytic double-spray thinning for 56 seconds in clean anhydrous ethanol, shake the sample for 10 seconds while moving the wrist joint, then take it out and blow dry.

[0053] (8) The sample obtained in (7) was further ion thinned using a precision argon ion thinning instrument model 691. The ion thinning parameters were: the left and right ion guns were tilted 5° relative to the horizontal line, the voltage was 5 keV, and the thinning time was 40 min. The sample after ion thinning was placed in a sample box for use.

[0054] The above description is only a specific embodiment of the present invention, but the structural features protected by the present invention are not limited thereto. Any changes or modifications made by any technician in this field within the scope of the present invention are included in the patent scope of the present invention.

Claims

1. A method for preparing a cast transmission electron microscope specimen of Ni36 precision alloy with high efficiency and low damage, characterized in that: It includes the following steps: Step 1: Cut a metallographic specimen from a Ni36 precision alloy casting blank and polish it by hand. Step 2: Cut a sheet specimen from the metallographic specimen after hand polishing. After cleaning the oil stain on the surface, immerse it in aqua regia for corrosion and thinning. Step 3: Manually polish the sample after corrosion and thinning to prepare a circular sample with a diameter of Φ3mm. Step 4: Place the circular sample into an electrolytic twin-jet thinning instrument filled with electrolyte for electrolytic twin-jet thinning. Step 5: Place the circular sample after electrolytic twin-jet thinning into a precision argon ion thinning instrument for further ion thinning to obtain a Ni36 precision alloy as-cast transmission electron microscopy specimen.

2. The method for preparing a Ni36 precision alloy as-cast transmission electron microscope specimen with high efficiency and low damage according to claim 1, characterized in that: In the said Step 1, a metallographic specimen with a size of (5~20)mm×(5~20)mm and a thickness of 10~20mm is taken from the Ni36 casting blank. Then, the cross-section of the specimen is polished on both sides in a circular motion successively with sandpapers of 10~50 meshes, 200~360 meshes and canvas, and the polishing direction each time is perpendicular to the previous one. Ensure that the scratches of the previous time cannot be seen on the cross-section each time. Finally, polish it with diamond polishing agent with a particle size of 4~6μm until the surface of the sample is mirror-like and there are no other foreign matters.

3. The method for preparing a Ni36 precision alloy as-cast transmission electron microscope specimen with high efficiency and low damage according to claim 1, characterized in that: In the said Step 2, use a wire cutting machine to cut sheet specimens with a thickness of 1.0~1.5mm on both sides respectively. Then immerse the sheet specimens in clean absolute ethanol for ultrasonic cleaning for 30~50s. After cleaning the oil stain on the surface of the specimens, put them into a beaker filled with aqua regia and let them stand for 12~18min. Take them out with tweezers, immerse them in clean absolute ethanol for cleaning 3~5 times, 30~50s each time, and then dry them. Measure the thickness to reach 100~150μm.

4. The method for preparing a Ni36 precision alloy as-cast transmission electron microscope sample with high efficiency and low damage according to claim 1, characterized in that: In the said Step 3, press the sample after corrosion and thinning with a rubber, gently press and polish it in a circular motion on 2000~3500 mesh sandpaper to remove the floating powder on the surface until the thickness of the sample is 65~90μm. Use a circular sample puncher to punch the 65~90μm thick sample to obtain a circular sample with a diameter of Φ3mm.

5. The method for preparing a cast transmission electron microscope specimen of Ni36 precision alloy with high efficiency and low damage according to claim 1, wherein: In the said Step 4, place the circular sample into an electrolytic twin-jet thinning instrument filled with electrolyte for thinning for 50~70s.

6. The method for preparing a Ni36 precision alloy as-cast transmission electron microscope specimen with high efficiency and low damage according to claim 1, wherein: The electrolyte in the said Step 4 is a mixed solution prepared from 1000mL absolute ethanol and 25mL~30mL hydrochloric acid with a concentration of 36.0%~38.0%.

7. The method for preparing a Ni36 precision alloy as-cast transmission electron microscope specimen with high efficiency and low damage according to claim 1, characterized in that: The thinning process parameters in the said Step 4: the electrolytic voltage is 20~25V, the electrolytic current during the twin-jet thinning process is 50~60mA, and the working temperature of the electrolyte is -12℃~-18℃.

8. The method for preparing a Ni36 precision alloy as-cast transmission electron microscope specimen with high efficiency and low damage according to claim 5, characterized in that: In the said Step 4, the sample after electrolytic twin-jet thinning for 50~70s needs to be immersed in clean absolute ethanol, shaken for 10~15s and then taken out and dried.

9. The method for preparing a Ni36 precision alloy as-cast transmission electron microscope specimen with high efficiency and low damage according to claim 1, wherein: In the said Step 5, use a precision argon ion thinning instrument to further ion thin the dried electrolytic twin-jet thinned circular sample, and put the ion-thinned sample into a sample box for standby.

10. The method for preparing a Ni36 precision alloy as-cast transmission electron microscope specimen with high efficiency and low damage according to claim 1, wherein: The particle thinning process parameters in the said Step 5: the left and right ion guns are inclined 5~7° relative to the horizontal line, the voltage is 4~5keV, and the thinning time is 35~55min.

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