A high-calibration EBSD sample preparation method for 7-series aluminum alloy materials

Abstract

A method for preparing an EBSD sample with a high calibration rate for 7-series aluminum alloy materials relates to a method for preparing an EBSD sample with a high calibration rate for aluminum alloy materials. The present invention aims to solve the technical problem that there is no universal electrolytic polishing process in the preparation process of existing 7-series aluminum alloy EBSD samples, and corrosion pits are easily generated on the sample surface, which seriously affects the generation of diffraction patterns. The present invention further adopts SiO2 sol polishing on the basis of mechanical polishing, which can remove the stress layer generated on the sample surface during the mechanical polishing process, which is conducive to the generation of strong Kikuchi patterns during EBSD testing; SiO2 sol can polish tissues and precipitated phases of different hardness, thereby making the sample surface smoother, alleviating the extrusion deformation effect of the hard second phase on the aluminum substrate during the mechanical polishing process, further improving the imaging quality of EBSD, and facilitating the study and analysis of the microstructure and texture of 7-series aluminum alloys during the preparation, processing and heat treatment process.

Description

Technical Field

[0001] The invention relates to an EBSD sample preparation method with a high calibration rate for aluminum alloy materials. Background Art

[0002] The 7 series aluminum alloy has attracted much attention for its excellent comprehensive mechanical properties, especially its extremely high specific strength, good corrosion resistance and outstanding high-temperature impact resistance, which makes it have great potential in load-bearing components with strict lightweight requirements, especially in the aerospace field. In the context of current scientific and technological progress, further improving the comprehensive performance of the 7 series aluminum alloy has become an important research topic. In order to achieve this goal, heat treatment of 7 series aluminum alloy is considered to be one of the most effective methods. During the heat treatment process, researchers focus on exploring how the microstructure of the material affects its mechanical properties. This research direction is crucial for optimizing the performance of the alloy, especially in improving its strength, corrosion resistance and toughness.

[0003] In order to effectively explore the evolution of interfaces and textures in 7-series aluminum alloys during heat treatment, EBSD analysis of the materials is required. EBSD technology can take into account both the crystal structure and orientation information of the material, and its role in the fields of metals, semiconductors, minerals, and ceramics is becoming increasingly important, gradually becoming a very important characterization method in material organization and texture analysis. The traditional EBSD sample preparation method for 7-series aluminum alloys is completed in two steps: mechanical polishing and electrolytic polishing. During the electrolytic polishing process, the cathode material is usually a platinum sheet, and the electrolyte is a mixed solution of HClO4 and CH3CH2OH, with a volume ratio of generally 1:9. Conventional electropolishing methods for EBSD specimen preparation can produce qualified EBSD specimens under appropriate process parameters. However, due to the diverse heat treatment states of 7-series aluminum alloys, different electropolishing process parameters are required for each heat treatment state. Currently, there is no universal electropolishing process that can achieve a surface with a high calibration rate (the calibration rate is the ratio of the number of Kikuchi pattern points accurately calibrated by a computer to the total number of points collected). This is especially true when the material contains a large number of precipitated phases or has a large amount of deformation, which often requires a considerable amount of process exploration. Furthermore, when preparing EBSD samples using electropolishing methods, corrosion pits are prone to form on the sample surface due to unstable process parameters, which can seriously affect the generation of diffraction patterns. These problems can cause significant inconvenience for researchers. Therefore, there is an urgent need to develop a simple, easy-to-use polishing method for 7-series aluminum alloys with a high calibration rate. Summary of the Invention

[0004] The present invention aims to solve the technical problems that there is no universal electrolytic polishing process in the preparation process of existing 7 series aluminum alloy EBSD samples, and corrosion pits are easily formed on the sample surface, which seriously affects the generation of diffraction patterns. The present invention provides an EBSD sample preparation method with a high calibration rate for 7 series aluminum alloy materials.

[0005] The EBSD sample preparation method for 7 series aluminum alloy materials with high calibration rate of the present invention is carried out according to the following steps:

[0006] 1. Sample preparation:

[0007] Cut the 7 series aluminum alloy material into small rectangular pieces. If the sample size is small, it can be inlaid to obtain the original sample for electron backscatter diffraction analysis of 7 series aluminum alloy;

[0008] 2. Sample coarse grinding:

[0009] Use different types of metallographic sandpaper to perform preliminary grinding on the sample prepared in step 1. During the grinding process, the grinding direction should be constantly changed to ensure that the force in each direction is uniform until the surface of the sample is flat after rough grinding and the scratch direction is consistent;

[0010] 3. Anhydrous ethanol cleaning:

[0011] The rough-ground sample was ultrasonically cleaned in anhydrous ethanol for 5 to 10 minutes to prevent the debris generated during the grinding process from affecting the subsequent polishing;

[0012] 4. Mechanical polishing:

[0013] After cleaning, blow dry the sample and then mechanically polish it with diamond spray polishing agent. During the polishing process, the sample needs to be rotated 90 degrees horizontally every 3 to 5 minutes. The total polishing time is 10 to 15 minutes. After polishing, the surface of the sample needs to be bright and free of scratches.

[0014] 5. Anhydrous ethanol cleaning:

[0015] After mechanical polishing, the sample was ultrasonically cleaned with anhydrous ethanol for 5 to 10 minutes to remove the residual diamond polishing agent on the sample surface;

[0016] 6. SiO2 sol polishing:

[0017] The sample cleaned in step 5 is subjected to final polishing on a rubber polishing disc using SiO2 sol. During the polishing process, anhydrous ethanol is sprayed for lubrication. During the polishing process, the sample is rotated horizontally by 90° every 3 to 5 minutes. The total polishing time is 10 to 20 minutes, and a sample with a bright surface and no scratches is finally obtained.

[0018] 7. Anhydrous ethanol cleaning: Place the polished sample in anhydrous ethanol and ultrasonically clean it for 5 minutes to 10 minutes, then blow dry and store it;

[0019] In steps 2, 4, and 6, the same surface of the sample is polished.

[0020] The beneficial effects of the present invention are:

[0021] 1) The present invention further utilizes SiO2 sol polishing in addition to mechanical polishing, which can remove the stress layer generated on the sample surface during the mechanical polishing process, thereby facilitating the generation of strong diffraction patterns during EBSD testing. Furthermore, SiO2 sol can simultaneously polish structures and precipitated phases of varying hardness, thereby smoothing the sample surface and alleviating the extrusion deformation of the hard second phase on the aluminum substrate during mechanical polishing, thereby further improving EBSD imaging quality and facilitating the study and analysis of the microstructure and texture of 7-series aluminum alloys during preparation, processing, and heat treatment.

[0022] 2) The method of the present invention is simple to operate, easy to control, and has good effects. It is suitable for the preparation of EBSD specimens of 7-series aluminum alloys of various types or heat treatment processes. In particular, for 7-series aluminum alloy materials with more precipitated phases, a large amount of second phases, and large deformation, its effect is significantly better than electrolytic polishing. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The grain morphology orientation map and inverse pole figure obtained by EBSD analysis of the sample prepared in Experiment 1;

[0024] Figure 2 The grain morphology orientation map and inverse pole figure obtained by EBSD analysis of the sample prepared in Experiment 2;

[0025] Figure 3 The grain morphology orientation map and inverse pole figure obtained by EBSD analysis of the same aluminum alloy sample prepared by conventional electrolytic polishing as in Experiment 2;

[0026] Figure 4 Grain morphology orientation map and inverse pole figure of the sample prepared for experiment three. DETAILED DESCRIPTION

[0027] Specific embodiment 1: This embodiment is a method for preparing EBSD samples with high calibration rate for 7 series aluminum alloy materials, which is specifically carried out in the following steps:

[0028] 1. Sample preparation:

[0029] The 7 series aluminum alloy material was cut into small rectangular pieces to obtain the original sample for electron backscatter diffraction analysis of the 7 series aluminum alloy;

[0030] 2. Sample coarse grinding:

[0031] Use different types of metallographic sandpaper to perform preliminary grinding on the sample prepared in step 1. During the grinding process, the grinding direction should be constantly changed to ensure that the force in each direction is uniform until the surface of the sample is flat after rough grinding and the scratch direction is consistent;

[0032] 3. Anhydrous ethanol cleaning:

[0033] The rough-ground sample was ultrasonically cleaned in anhydrous ethanol for 5 to 10 minutes to prevent the debris generated during the grinding process from affecting the subsequent polishing;

[0034] 4. Mechanical polishing:

[0035] After cleaning, blow dry the sample and then mechanically polish it with diamond spray polishing agent. During the polishing process, the sample needs to be rotated 90 degrees horizontally every 3 to 5 minutes. The total polishing time is 10 to 15 minutes. After polishing, the surface of the sample needs to be bright and free of scratches.

[0036] 5. Anhydrous ethanol cleaning:

[0037] After mechanical polishing, the sample was ultrasonically cleaned with anhydrous ethanol for 5 to 10 minutes to remove the residual diamond polishing agent on the sample surface;

[0038] 6. SiO2 sol polishing:

[0039] The sample cleaned in step 5 is subjected to final polishing on a rubber polishing disc using SiO2 sol. During the polishing process, anhydrous ethanol is sprayed for lubrication. During the polishing process, the sample is rotated horizontally by 90° every 3 to 5 minutes. The total polishing time is 10 to 20 minutes, and a sample with a bright surface and no scratches is finally obtained.

[0040] 7. Anhydrous ethanol cleaning: Place the polished sample in anhydrous ethanol and ultrasonically clean it for 5 minutes to 10 minutes, then blow dry and store it;

[0041] In steps 2, 4, and 6, the same surface of the sample is polished.

[0042] Specific embodiment 2: This embodiment differs from specific embodiment 1 in that in step 2, the sample prepared in step 1 is preliminarily polished using 600#, 800#, 1000#, 1500#, 2000#, and 3000# metallographic sandpaper in sequence. Other steps are the same as specific embodiment 1.

[0043] Specific embodiment 3: This embodiment differs from specific embodiment 1 or 2 in that: in step 3, the coarsely ground sample is ultrasonically cleaned in anhydrous ethanol for 5 minutes. Other aspects are the same as specific embodiment 1 or 2.

[0044] Specific embodiment 4: This embodiment differs from specific embodiments 1 to 3 in that the diamond spray polishing agent in step 4 is W0.5 diamond spray polishing agent. Other aspects are the same as specific embodiments 1 to 3.

[0045] Specific embodiment 5: This embodiment differs from specific embodiment 4 in that in step 4, the sample needs to be rotated horizontally by 90° every 3 minutes during the polishing process. Other aspects are the same as specific embodiment 4.

[0046] Specific embodiment 6: This embodiment differs from specific embodiment 5 in that the total polishing time in step 4 is 12 minutes. Other aspects are the same as specific embodiment 5.

[0047] Specific embodiment 7: This embodiment differs from specific embodiment 6 in that the sample after mechanical polishing in step 5 is ultrasonically cleaned with anhydrous ethanol for 5 minutes. Other aspects are the same as specific embodiment 6.

[0048] Specific embodiment eight: This embodiment differs from specific embodiment seven in that the particle size of the SiO2 sol in step six is 30 nm to 50 nm. Other aspects are the same as specific embodiment seven.

[0049] Specific embodiment 9: This embodiment differs from specific embodiment 8 in that: in step 6, the sample is rotated horizontally by 90° every 3 minutes during the polishing process, and the total polishing time is 15 minutes. Other aspects are the same as specific embodiment 8.

[0050] Specific embodiment 10: This embodiment differs from specific embodiment 9 in that the rotation speed of the polishing disc during polishing in step 6 is 200 rpm to 300 rpm, and the rubber polishing disc in step 6 is a porous neoprene rubber polishing disc. Other aspects are the same as specific embodiment 9.

[0051] The present invention is verified by the following test:

[0052] Experiment 1: This experiment is a high-calibration EBSD sample preparation method for 7-series aluminum alloy materials. The specific steps are as follows:

[0053] 1. Sample preparation:

[0054] The O-state 7075 aluminum alloy material with a thickness of 5 mm was cut into rectangular small pieces (length and width were 1 cm) to obtain the original sample of the O-state 7075 aluminum alloy electron backscatter diffraction analysis;

[0055] 2. Sample coarse grinding:

[0056] Use 600#, 800#, 1000#, 1500#, 2000# and 3000# metallographic sandpaper to perform preliminary grinding on the sample prepared in step 1. During the grinding process, the grinding direction should be constantly changed to ensure uniform force in all directions until the surface of the sample is flat and the scratch direction is consistent after rough grinding.

[0057] 3. Anhydrous ethanol cleaning:

[0058] The rough-ground specimens were ultrasonically cleaned in anhydrous ethanol for 5 min to prevent debris generated during the grinding process from affecting subsequent polishing;

[0059] 4. Mechanical polishing:

[0060] After cleaning, the sample was blown dry and then mechanically polished with W0.5 diamond spray polishing agent. During the polishing process, the sample was rotated 90° horizontally every 3 minutes. The total polishing time was 12 minutes. After polishing, the sample surface must be bright and scratch-free.

[0061] 5. Anhydrous ethanol cleaning:

[0062] After mechanical polishing, the sample was ultrasonically cleaned with anhydrous ethanol for 5 min to remove the residual diamond polishing agent on the sample surface;

[0063] 6. SiO2 sol polishing:

[0064] The sample cleaned in step 5 is subjected to final polishing on a porous neoprene polishing disc using SiO2 sol. During the polishing process, SiO2 should not be added too much. Anhydrous ethanol is sprayed appropriately for lubrication during the polishing process. During the polishing process, the sample is rotated horizontally by 90° every 3 minutes. The total polishing time is 15 minutes, and the polishing disc speed is 300 r / min. Finally, a sample with a bright surface and no scratches is obtained. The particle size of the SiO2 sol is 50 nm.

[0065] 7. Anhydrous ethanol cleaning: Place the polished sample in anhydrous ethanol and ultrasonically clean it for 5 minutes, then blow dry and store it;

[0066] In steps 2, 4, and 6, the same surface of the sample is polished.

[0067] Experiment 2: This experiment is a method for preparing EBSD samples with high calibration rate for 7 series aluminum alloy materials. The specific steps are as follows:

[0068] 1. Sample preparation:

[0069] The cold-rolled 7075 aluminum alloy material with a thickness of 6.35 mm was cut into rectangular small pieces (length and width were 1 cm) to obtain the original sample of cold-rolled 7075 aluminum alloy electron backscatter diffraction analysis;

[0070] 2. Sample coarse grinding:

[0071] Use 600#, 800#, 1000#, 1500#, 2000# and 3000# metallographic sandpaper to perform preliminary grinding on the sample prepared in step 1. During the grinding process, the grinding direction should be constantly changed to ensure uniform force in all directions until the surface of the sample is flat and the scratch direction is consistent after rough grinding.

[0072] 3. Anhydrous ethanol cleaning:

[0073] The rough-ground specimens were ultrasonically cleaned in anhydrous ethanol for 5 min to prevent debris generated during the grinding process from affecting subsequent polishing;

[0074] 4. Mechanical polishing:

[0075] After cleaning, the sample was blown dry and then mechanically polished with W0.5 diamond spray polishing agent. During the polishing process, the sample was rotated 90° horizontally every 3 minutes. The total polishing time was 15 minutes. After polishing, the sample surface must be bright and scratch-free.

[0076] 5. Anhydrous ethanol cleaning:

[0077] After mechanical polishing, the sample was ultrasonically cleaned with anhydrous ethanol for 5 min to remove the residual diamond polishing agent on the sample surface;

[0078] 6. SiO2 sol polishing:

[0079] The sample cleaned in step 5 was subjected to final polishing on a porous neoprene polishing disc using SiO2 sol. During the polishing process, SiO2 should not be added too much. Anhydrous ethanol was sprayed appropriately for lubrication. During the polishing process, the sample was rotated horizontally by 90° every 3 minutes. The total polishing time was 21 minutes, and the polishing disc speed was 300 r / min. Finally, a sample with a bright surface and no scratches was obtained. The particle size of the SiO2 sol was 50 nm.

[0080] 7. Anhydrous ethanol cleaning: Place the polished sample in anhydrous ethanol and ultrasonically clean it for 5 minutes, then blow dry and store it;

[0081] In steps 2, 4, and 6, the same surface of the sample is polished.

[0082] Experiment 3: This experiment is a high-calibration EBSD sample preparation method for 7-series aluminum alloy materials. The specific steps are as follows:

[0083] 1. Sample preparation:

[0084] The T6 aged 7075 aluminum alloy material with a thickness of 4.75 mm was cut into rectangular small pieces (length and width were 1 cm) to obtain the original sample of T6 aged 7075 aluminum alloy electron backscatter diffraction analysis;

[0085] 2. Sample coarse grinding:

[0086] Use 600#, 800#, 1000#, 1500#, 2000# and 3000# metallographic sandpaper to perform preliminary grinding on the sample prepared in step 1. During the grinding process, the grinding direction should be constantly changed to ensure uniform force in all directions until the surface of the sample is flat and the scratch direction is consistent after rough grinding.

[0087] 3. Anhydrous ethanol cleaning:

[0088] The rough-ground specimens were ultrasonically cleaned in anhydrous ethanol for 5 min to prevent debris generated during the grinding process from affecting subsequent polishing;

[0089] 4. Mechanical polishing:

[0090] After cleaning, the sample was blown dry and then mechanically polished with W0.5 diamond spray polishing agent. During the polishing process, the sample was rotated 90° horizontally every 3 minutes. The total polishing time was 12 minutes. After polishing, the sample surface must be bright and scratch-free.

[0091] 5. Anhydrous ethanol cleaning:

[0092] After mechanical polishing, the sample was ultrasonically cleaned with anhydrous ethanol for 5 min to remove the residual diamond polishing agent on the sample surface;

[0093] 6. SiO2 sol polishing:

[0094] The sample cleaned in step 5 is subjected to final polishing on a porous neoprene polishing disc using SiO2 sol. During the polishing process, SiO2 should not be added too much. Anhydrous ethanol is sprayed appropriately for lubrication. During the polishing process, the sample is rotated horizontally by 90° every 3 minutes. The total polishing time is 12 minutes, and the polishing disc speed is 200 r / min. Finally, a sample with a bright surface and no scratches is obtained. The particle size of the SiO2 sol is 50 nm.

[0095] 7. Anhydrous ethanol cleaning: Place the polished sample in anhydrous ethanol and ultrasonically clean it for 5 minutes, then blow dry and store it;

[0096] In steps 2, 4, and 6, the same surface of the sample is polished.

[0097] Figure 1 The grain morphology orientation map and inverse pole figure (IPF, Figure 1 (Figure in the upper right corner), 7075 aluminum alloy was treated in the O state. It can be seen from the figure that a large amount of second phases were precipitated in its structure, indicating that the method of the present invention can be applied to the preparation of EBSD samples of 7 series aluminum alloy materials containing a large amount of precipitated phases.

[0098] Figure 2 The grain morphology orientation map and inverse pole figure (IPF, Figure 2 (top right corner of the picture), Figure 3 The grain morphology orientation map and inverse pole figure obtained by EBSD analysis of the same aluminum alloy sample prepared by traditional electrolytic polishing and test 2, the cold rolled 7075 aluminum alloy contains not only a large amount of MgZn2 second phase ( Figure 2 and Figure 3 The black area in the figure), and the deformation of the grains is also large. The large deformation and the presence of the second phase will have a serious impact on the preparation of aluminum alloy EBSD samples. The comparison of the images obtained by the two different preparation methods shows that the traditional electrolytic polishing preparation method cannot obtain a high-calibration grain morphology orientation map when dealing with such materials. This also proves the superiority of the method of the present invention in the preparation of EBSD samples of 7 series aluminum alloy materials containing a large amount of second phases and large deformation.

[0099] Figure 4 The grain morphology orientation diagram and inverse pole figure of the sample prepared for experiment three are intended to confirm that the method of the present invention can also obtain high-quality EBSD samples when applied to 7 series aluminum alloy materials with a low second phase content, indicating that the present invention has wide applicability.

Claims

1. A method for preparing EBSD samples with high calibration rate for 7 series aluminum alloy materials, characterized in that The EBSD sample preparation method for 7 series aluminum alloy materials with high calibration rate is carried out in the following steps:

1. Sample preparation: The 7 series aluminum alloy material was cut into small rectangular pieces to obtain the original sample for electron backscatter diffraction analysis of the 7 series aluminum alloy; 2. Sample coarse grinding: Use different types of metallographic sandpaper to perform preliminary grinding on the sample prepared in step 1. During the grinding process, the grinding direction should be constantly changed to ensure that the force in each direction is uniform until the surface of the sample is flat after rough grinding and the scratch direction is consistent; 3. Anhydrous ethanol cleaning: The rough-ground sample was ultrasonically cleaned in anhydrous ethanol for 5 to 10 minutes to prevent the debris generated during the grinding process from affecting the subsequent polishing; 4. Mechanical polishing: After cleaning, blow dry the sample and then mechanically polish it with diamond spray polishing agent. During the polishing process, the sample needs to be rotated 90 degrees horizontally every 3 to 5 minutes. The total polishing time is 10 to 15 minutes. After polishing, the surface of the sample needs to be bright and free of scratches.

5. Anhydrous ethanol cleaning: After mechanical polishing, the sample was ultrasonically cleaned with anhydrous ethanol for 5 to 10 minutes to remove the residual diamond polishing agent on the sample surface; 6. SiO2 sol polishing: The sample cleaned in step 5 is subjected to final polishing on a rubber polishing disc using SiO2 sol. During the polishing process, anhydrous ethanol is sprayed for lubrication. During the polishing process, the sample is rotated horizontally by 90° every 3 to 5 minutes. The total polishing time is 10 to 20 minutes, and a sample with a bright surface and no scratches is finally obtained.

7. Anhydrous ethanol cleaning: Place the polished sample in anhydrous ethanol and ultrasonically clean it for 5 minutes to 10 minutes, then blow dry and store it; In steps 2, 4, and 6, the same surface of the sample is polished.

2. The EBSD sample preparation method for 7 series aluminum alloy materials with high calibration rate according to claim 1, characterized in that In step 2, the sample prepared in step 1 was preliminarily polished using 600#, 800#, 1000#, 1500#, 2000# and 3000# metallographic sandpaper in sequence.

3. The EBSD sample preparation method for 7 series aluminum alloy materials with high calibration rate according to claim 1 is characterized in that In step 3, the coarsely ground sample was ultrasonically cleaned in anhydrous ethanol for 5 minutes.

4. The EBSD sample preparation method for 7 series aluminum alloy materials with high calibration rate according to claim 1, characterized in that The diamond spray polishing agent described in step 4 is W0.5 diamond spray polishing agent.

5. The EBSD sample preparation method for 7 series aluminum alloy materials with high calibration rate according to claim 1 is characterized in that In step 4, the sample needs to be rotated horizontally 90° every 3 minutes during the polishing process.

6. The method for preparing an EBSD sample with a high calibration rate for a 7-series aluminum alloy according to claim 5, characterized in that The total polishing time in step 4 is 12 minutes.

7. The method for preparing an EBSD sample with a high calibration rate for a 7-series aluminum alloy according to claim 1, characterized in that After mechanical polishing in step 5, the sample was ultrasonically cleaned with anhydrous ethanol for 5 minutes.

8. The method for preparing an EBSD sample with a high calibration rate for a 7-series aluminum alloy according to claim 1, characterized in that The particle size of the SiO2 sol described in step six is 30nm to 50nm.

9. The method for preparing an EBSD sample with a high calibration rate for a 7-series aluminum alloy according to claim 1, characterized in that During the polishing process in step 6, the sample was rotated horizontally by 90° every 3 minutes, and the total polishing time was 15 minutes.

10. The method for preparing an EBSD sample with a high calibration rate for a 7-series aluminum alloy according to claim 1, characterized in that During polishing in step 6, the rotation speed of the polishing disc is 200 r / min to 300 r / min; the rubber polishing disc described in step 6 is a porous chloroprene rubber polishing disc.

Images