Preparation method of heterogeneous high-hardness-difference material EBSD sample

Abstract

The invention belongs to the technical field of EBSD sample preparation, and particularly relates to a preparation method of an EBSD sample of a heterogeneous high-hardness-difference material, grinding and polishing equipment with a vacuum chuck for fixing the sample is used for grinding and polishing the sample to achieve a mirror surface effect, so that the interface of the heterogeneous material has no height difference under the observation of a metallographic microscope; and according to the phase distribution characteristics of the heterogeneous material and the polishing resistance coefficients of the hard phase and the soft phase, corresponding argon ion beam focusing positions and argon ion polishing parameters are selected, and three-ion-beam argon ion polishing equipment is used for polishing according to the selected polishing parameters. According to the EBSD sample preparation method, the preparation quality of the heterogeneous boundary of the heterogeneous high-hardness-difference material is guaranteed, the height difference is smaller than 0.2 micron, the real crystal orientation characteristics of the boundary of the heterogeneous high-hardness-difference material can be well recognized under a metallographic microscope, the calibration rate at the boundary is not lower than 95%, and accurate analysis of the crystal structure at the interface of the heterogeneous material is achieved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of EBSD sample preparation, and particularly relates to a preparation method of an EBSD sample of heterogeneous high-hardness-difference materials. BACKGROUND

[0002] In recent years, heterogeneous high-hardness-difference materials such as heterogeneous welded joints and hard particle reinforced metal matrix composites have become a research hotspot due to their excellent comprehensive performance, and the research and analysis of the interface characteristics such as crystal phase distribution characteristics, element segregation at the interface, interface dislocation, and lattice distortion of the materials are crucial to improving the application performance of the materials. Electron backscatter diffraction (EBSD) uses backscattered electron diffraction to obtain crystal orientation and phase information, and analyze the grain morphology and size, phase distribution and content, internal organization strain, and texture of a sample, and is an effective means for researching the interface organization of heterogeneous high-hardness-difference materials. However, the difficulty in sample preparation at the interface of heterogeneous difference materials hinders researchers from exploring the truth of the interface organization.

[0003] The most commonly used sample preparation methods for EBSD electron microscope samples include electrolytic polishing, vibration polishing, and argon ion polishing. For electrolytic polishing, it is difficult to use electrolytic polishing to prepare EBSD samples of heterogeneous materials because the electrolyte and electrolytic parameters required for different parts of the heterogeneous materials are different. For vibration polishing, the vibration polishing using polishing particles to polish the sample will exacerbate the unevenness at the interface because the heterogeneous high-hardness-difference materials are composed of materials with large hardness differences, and the hardness of the materials at different positions differs greatly. Moreover, the polishing time required for the soft phase and the hard phase is different, and vibration polishing cannot be flexibly adjusted. For argon ion polishing, it has high requirements for the mechanical grinding and polishing of the surface of the electron microscope sample, and the argon ion polishing process of the heterogeneous high-hardness-difference materials is also different, and the following problems are faced:

[0004] 1. Mechanical grinding and polishing can easily cause the heterogeneous high-hardness-difference materials to have a height difference at the junction of the hard phase and the soft phase, which is not conducive to subsequent argon ion polishing treatment.

[0005] Traditional mechanical polishing uses a rigid clamp to fix the sample. When the heterogeneous material is ground, a step-shaped height difference is easily formed at the junction of the hard phase and the soft phase due to the difference in the plastic deformation resistance of each phase. In addition, the existing automatic polishing machine applies a constant pressure (usually ≥0.5 MPa) load, which causes the soft phase to flow plastically under the extrusion of the abrasive particles, further exacerbating the unevenness of the interface.

[0006] 2. Argon ion polishing has high requirements for the flatness of the previous mechanical grinding and polishing, and the suitable parameters are different for different soft phases and hard phases, which can easily cause over-polishing of the soft phase and residual stress of the hard phase, resulting in poor EBSD sample preparation effect.

[0007] On the one hand, the argon ion polishing depth is shallow, and the flatness requirement of mechanical polishing is higher; on the other hand, the argon ion polishing parameters of different parts of the heterogeneous material are different, and the etching pits of the soft material are deeper if the argon ion polishing parameters of the hard material are used for polishing, which affects the resolution; if the argon ion polishing parameters of the soft material are used for polishing, it is difficult to completely remove the residual stress of the hard material, which reduces the diffraction spectrum resolution, and the Kikuchi line is blurred and distorted, resulting in poor or failed sample preparation effect. SUMMARY

[0008] In view of the problem that the existing polishing means is difficult to be applied to the EBSD sample preparation of heterogeneous high hardness difference material, the present application proposes a preparation method of EBSD sample of heterogeneous high hardness difference material, which uses a vacuum chuck to fix the sample during mechanical polishing to ensure that the lower surface of the sample is always parallel to the polishing disc during polishing, thereby reducing the height difference between heterogeneous phases caused by the difference in plastic deformation resistance of each phase in the sample; then based on the phase distribution characteristics and polishing resistance coefficient of the heterogeneous high hardness difference material, appropriate argon ion polishing parameters are determined for argon ion polishing, and finally the resolution of the prepared EBSD sample at the interface region of the heterogeneous phase is not less than 95%, and the crystal phase characteristics at the interface are perfectly resolved.

[0009] To achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0010] A preparation method of EBSD sample of heterogeneous high hardness difference material, comprising the following steps:

[0011] (1) using a polishing equipment with a vacuum chuck to fix the sample, polishing the heterogeneous high hardness difference material sample to a mirror effect, and the roughness of the sample surface is less than or equal to 0.2 μm;

[0012] (2) polishing the polished sample by argon ion polishing, determining the argon ion beam focusing position and argon ion polishing parameters based on the phase distribution characteristics of the hard phase and the soft phase of the heterogeneous high hardness difference material and the polishing resistance coefficient of the hard phase and the soft phase;

[0013] (3) using a three-ion beam argon ion polishing equipment to polish the sample by argon ion polishing to prepare an EBSD sample according to the argon ion polishing parameters determined in step (2).

[0014] Preferably, the mechanical polishing comprises the following steps:

[0015] The sample is vacuum adsorbed and fixed on the sample holder, so that the lower surface of the sample is always parallel to the polishing disc, and the sample is polished by using diamond sandpaper with a mesh size of 400, 800, 1200, 2000 and 5000 in turn, and then polished by using 1 μm diamond polishing liquid and 0.1 μm silicon dioxide polishing liquid in turn, until the roughness of the sample surface is less than or equal to 0.2 μm.

[0016] Preferably, the ion beam focus position is determined based on the phase distribution characteristics of the hard phase and soft phase of the heterogeneous high hardness difference material, specifically as follows:

[0017] ① When the phase distribution of the heterogeneous high hardness difference material is adjacent distribution of the hard phase and the soft phase, the ion beam focus position of argon ion polishing is selected to be 0.5-2 mm offset from the boundary of the hard phase and the soft phase to the hard phase;

[0018] ② When the phase distribution of the heterogeneous high hardness difference material is dispersed distribution of the hard phase and the soft phase, the ion beam focus position of argon ion polishing can be on the sample surface, without specific position limitation. For convenience, the sample center is usually selected as the ion beam focus position.

[0019] Preferably, for the sample with adjacent distribution of the hard phase and the soft phase, the argon ion beam focus position is further determined based on the difference of the polishing resistance coefficients of the hard phase and the soft phase, specifically as follows:

[0020] A. When the difference of the polishing resistance coefficients of the two phases is ≤0.1, the ion beam focus position is at a position 0.5 mm offset from the boundary of the hard phase and the soft phase to the hard phase;

[0021] B. When 0.1<the difference of the polishing resistance coefficients of the two phases is ≤0.25, the ion beam focus position is at a position 1 mm offset from the boundary of the hard phase and the soft phase to the hard phase;

[0022] C. When 0.25<the difference of the polishing resistance coefficients of the two phases is ≤0.4, the ion beam focus position is at a position 1.5 mm offset from the boundary of the hard phase and the soft phase to the hard phase;

[0023] D. When 0.4<the difference of the polishing resistance coefficients of the two phases is ≤0.6, the ion beam focus position is at a position 2 mm offset from the boundary of the hard phase and the soft phase to the hard phase.

[0024] Preferably, the polishing resistance coefficient of the hard phase or the soft phase is calculated by the following formula:

[0025] Polishing resistance coefficient=0.3×(hardness / 3430)+0.5×(sputtering yield reciprocal / 2.5)+0.2×(thermal conductivity / 401);

[0026] The polishing resistance coefficient of the sample is the average of the polishing resistance coefficients of the hard phase and the soft phase, represented by the following formula:

[0027] Polishing resistance coefficient of the sample=(polishing resistance coefficient of the hard phase+polishing resistance coefficient of the soft phase)÷2.

[0028] Preferably, the argon ion polishing voltage is determined based on the polishing resistance coefficient of the sample, specifically as follows:

[0029] a. When 0.5 < the average value of the sample resistance to polishing coefficient ≤ 0.75, the argon ion polishing voltage is set to 6kV;

[0030] b. When 0.3 < the average value of the sample resistance to polishing coefficient ≤ 0.5, the argon ion polishing voltage is set to 5kV;

[0031] c. When 0.2 < the average value of the sample resistance to polishing coefficient ≤ 0.3, the argon ion polishing voltage is set to 4kV.

[0032] Preferably, the angle and polishing time of argon ion polishing are determined based on the phase distribution characteristics of the heterogeneous high hardness difference material, and specifically as follows:

[0033] I. When the hard phase and the soft phase in the sample are adjacent distribution, the polishing angle is 4.5°-7.5°, and the polishing time is 1.5-2.5h;

[0034] II. When the hard phase and the soft phase in the sample are dispersed distribution, the polishing angle is 7.5°-10.5°, and the polishing time is 1-2h.

[0035] Preferably, the main components of the heterogeneous high hardness difference material are at least two of tungsten carbide, tungsten, molybdenum, aluminum oxide, silicon, titanium, copper, magnesium, aluminum, gold.

[0036] The heterogeneous high hardness difference material of the application includes but is not limited to tungsten-copper alloy and other materials with large hardness difference, and also includes molybdenum-copper alloy and other materials with small hardness difference. The EBSD sample preparation method of the application is not only suitable for EBSD sample preparation of heterogeneous high hardness difference material, but also has better EBSD sample preparation effect for materials with small hardness difference.

[0037] Compared with the prior art, the application has the following beneficial effects:

[0038] (1) In the mechanical polishing process, the sample is fixed by a vacuum chuck, so that the lower surface of the sample is always parallel to the polishing disc, the height difference between the heterogeneous phases caused by the difference in plastic deformation resistance of the heterogeneous phases is reduced, the step height difference at the junction of the hard phase and the soft phase is avoided, and the sample surface is smooth after polishing, which is helpful for subsequent argon ion polishing treatment.

[0039] (2) The present application determines the key factors for successful sample preparation according to a large number of EBSD sample preparation experiences of heterogeneous high-hardness-difference materials, and the key factors are the phase distribution of the heterogeneous high-hardness-difference materials and the polishing resistance of each phase. Further analysis determines the key factors for the polishing resistance of each phase as the Vickers hardness, sputtering yield and thermal conductivity of the material, so as to construct the polishing resistance coefficient of each phase. Based on the phase distribution characteristics of the heterogeneous high-hardness-difference materials and the polishing resistance coefficient of the two phases, the appropriate argon ion beam focusing position and argon ion polishing parameters are determined, and the EBSD sample is prepared by using a three-ion beam argon ion polishing equipment. The calibration rate of the EBSD sample prepared by the method of the present application in the heterogeneous phase interface region is not less than 95%, and the crystal characteristics at the two-phase interface are perfectly analyzed.

[0040] (3) The EBSD sample preparation method of the present application is not only suitable for heterogeneous materials with large hardness difference, such as tungsten-copper alloy, but also suitable for heterogeneous materials with small hardness difference, such as molybdenum-copper alloy, and the EBSD sample preparation rate is as high as 98%. BRIEF DESCRIPTION OF DRAWINGS

[0041] Figure 1 It is a structural diagram of a traditional polishing equipment without vacuum chuck;

[0042] Figure 2 It is a structural diagram of a traditional sample holder without vacuum chuck;

[0043] Figure 3 It is a structural diagram of a polishing equipment with vacuum chuck in Example 1;

[0044] Figure 4 It is a front view, sectional view and local enlarged view of a sample holder in Example 1;

[0045] Figure 5 It is a three-dimensional structural diagram of a sample holder in Example 1;

[0046] Figure 6 It is a bottom surface structural diagram of a sample holder in Example 1;

[0047] Figure 7 It is a use state diagram of a polishing equipment in Example 1;

[0048] In the figure: 1, sample holder; 2, polishing disc; 3, sample groove; 4, sample; 5, air hole; 6, vacuum pipe; 7, embedded hole; 8, vacuum pump;

[0049] Figure 8 It is a Kikuchi band contrast diagram and phase distribution diagram of a sample in Example 2;

[0050] Figure 9 It is a Kikuchi band contrast diagram and phase distribution diagram of a sample in Comparative Example 1;

[0051] Figure 10 It is a Kikuchi band contrast diagram and phase distribution diagram of a sample in Example 3. DETAILED DESCRIPTION

[0052] In order to better illustrate the purposes, technical solutions and advantages of the present application, the present application will be further described below in combination with specific embodiments. It should be understood by those skilled in the art that the specific embodiments described herein are only used to explain the present application and do not limit the present application.

[0053] Embodiment 1

[0054] For heterogeneous high-hardness-difference materials, it is difficult to use conventional mechanical polishing, electrolytic polishing, vibration polishing and argon ion polishing to prepare samples due to the large hardness difference of heterogeneous phases. Mechanical polishing and vibration polishing can exacerbate the height difference of the heterogeneous phase interface, and the electrolytic polishing and argon ion polishing of heterogeneous materials require different polishing, which can easily cause over-polishing of the soft phase and insufficient polishing of the hard phase, and it is difficult to prepare an EBSD sample with a calibration rate meeting the requirements.

[0055] The present embodiment provides an EBSD sample preparation method specially for heterogeneous high-hardness-difference materials. The EBSD sample preparation is performed by combining mechanical polishing with argon ion polishing. In view of the problem that mechanical polishing can exacerbate the height difference of the heterogeneous phase interface and is not conducive to subsequent polishing, the sample holder for mechanical polishing is improved, the sample is fixed by a vacuum chuck, so that the lower surface of the sample is always parallel to the polishing disc during mechanical polishing, and the height difference between the heterogeneous phases caused by the difference in plastic deformation resistance of the heterogeneous phases is reduced. Then, based on the phase distribution characteristics and polishing resistance coefficient of the heterogeneous high-hardness-difference materials, appropriate argon ion polishing parameters are determined for argon ion polishing, thereby providing an EBSD sample preparation method suitable for heterogeneous high-hardness-difference materials, and the calibration rate at the heterogeneous phase interface after EBSD sample preparation is not less than 95%, and the sample preparation effect is better.

[0056] The relative position relationship between the sample holder 1 and the polishing disc 2 in the existing mechanical polishing process is shown in Figure 1 A sample groove 3 is formed on the sample holder 1 Figure 2 The sample 4 is placed in the sample groove 3, and the lower surface of the sample 4 is in contact with the polishing disc. Since the hardness of each phase of the heterogeneous phase sample is different, the difference in plastic deformation resistance is large. Under the same pressure, polishing causes the soft phase to be polished too much and the hard phase to be polished relatively less with the continuous polishing, and a slope is gradually formed between the soft phase and the hard phase, exacerbating the height difference of the phase interface. Therefore, the existing sample holder 1 is improved in the present application, as shown in Figures 3 to 6 The relative position relationship between the sample holder 1, the sample 4 and the polishing disc 2 is shown in Figure 3 The structure of the improved sample holder 1 is shown in Figure 4 , 5 , and the schematic diagram of sample polishing by using the improved sample holder 1 of the present application is shown in Figure 7As shown, the improved sample holder 1 is provided with air holes 5, buried holes 7 and vacuum tubes 6 connected with the sample groove 3, the vacuum tubes 6 are connected with a vacuum pump 8 for vacuumizing, and the air holes 5 are provided with suction cups at the positions connected with the sample groove 3 for fixing the sample by vacuum adsorption. The number of the air holes 5 in the sample groove 3 is three or four, and they are arranged in a circular array to enhance the stability of the sample adsorption.

[0057] The specific process of mechanical grinding and polishing by using the improved grinding and polishing equipment is as follows:

[0058] The sample is embedded into a sample with a diameter of 30mm and a thickness of 5mm, and then the sample is placed in the sample groove with a diameter of 30mm on the sample holder, the vacuum pump is opened, and the three vacuum suction cups in the sample groove adsorb the upper surface of the sample on the sample holder to ensure that the sample surface is not inclined during the subsequent mechanical grinding and polishing process.

[0059] Then the grinding and polishing disc of the grinding and polishing machine is used to grind and polish the sample, and the sample is polished by using diamond sandpaper with a mesh of 400, 800, 1200, 2000 and 5000 in turn, and attention should be paid to let the sandpaper polish the hard phase part first, and then use 1 micron diamond polishing liquid and 0.1 micron silicon dioxide polishing liquid to polish the sample, and finally the surface roughness Ra of the sample is less than or equal to 0.2 microns, that is, the height difference at the two-phase interface is less than or equal to 0.2 microns, and there is almost no height difference between the interfaces of the heterogeneous materials under the observation of the metallographic microscope.

[0060] After the mechanical grinding and polishing of the sample, the sample is further polished by argon ion polishing, and due to the different argon ion polishing processes of heterogeneous materials, the etching pit of the soft material will be deeper if the hard material is polished with the argon ion polishing parameters, which will affect the resolution rate, and it will be difficult to completely remove the stress residue of the hard material if the soft material is polished with the argon ion polishing parameters, so that the EBSD sample with qualified calibration rate cannot be prepared, therefore, based on the phase distribution characteristics and polishing resistance coefficient of the heterogeneous high-hardness-difference material, appropriate argon ion polishing parameters are selected for polishing and sample preparation, and the specific method is as follows:

[0061] Firstly, the phase distribution characteristics of the heterogeneous high-hardness-difference material are determined, and the phase distribution of the heterogeneous high-hardness-difference material mainly includes the following two situations: 1. The hard phase and the soft phase are adjacent distribution, that is, the hard phase and the soft phase are separate large blocks, and there is only one adjacent interface; 2. The hard phase and the soft phase are dispersed distribution.

[0062] Secondly, the polishing resistance coefficient of each phase of the heterogeneous high-hardness-difference material is determined, and then the polishing resistance coefficient of the whole material is determined based on the polishing resistance coefficient of each phase.

[0063] The inventors of the present application screened three key parameters closely related to the resistance coefficient in a large number of experiments: the Vickers hardness (HV) of the material, the sputter yield and the thermal conductivity. Among them, the Vickers hardness (HV) as a basic parameter, directly affects the anti-mechanical sputtering ability with tungsten as the standard, the higher the hardness, the stronger the resistance. The sputter yield (Sputter Yield) is a key indicator, reflecting the material removal efficiency under unit ion bombardment, with tungsten carbide as the standard, the lower the sputter yield, the higher the resistance. The thermal conductivity reflects the heat dissipation capacity of the material, which affects the local temperature rise effect, with copper as the standard, the higher the thermal conductivity, the better the resistance.

[0064] Based on the above three key parameters, the resistance coefficient calculation formula of the material itself is obtained through a large number of experiments as follows:

[0065] Resistance coefficient = 0.3 × (hardness / 3430) + 0.5 × (sputter yield reciprocal / 2.5) + 0.2 × (thermal conductivity / copper thermal conductivity 401).

[0066] Based on the above calculation formula, the resistance coefficients of various materials are shown in the following table.

[0067]

[0068] Finally, based on the phase distribution characteristics and resistance coefficient of heterogeneous high hardness difference materials, the ion beam focusing position, argon ion polishing voltage, polishing angle and polishing time are determined, so as to carry out argon ion polishing sample preparation, as follows:

[0069] (1) Selection of ion beam focusing position and determination of polishing angle and polishing time

[0070] When the phase distribution of the heterogeneous high hardness difference material is adjacent distribution of hard phase and soft phase, the ion beam focusing position is at the position of 0.5-2mm offset from the boundary of hard phase and soft phase to hard phase, the polishing angle is 4.5°-7.5°, and the equipment is adjusted according to 1.5°, so the polishing angle can be selected as 4.5°, 6° or 7.5°, and the polishing time is 1.5-2.5h.

[0071] The distance of the ion beam focusing position offset to the hard phase is determined by the difference of the resistance coefficients of the two phases of the heterogeneous high hardness difference material, as follows:

[0072] A. When the difference of the resistance coefficients of the two phases is ≤0.1, the ion beam focusing position is at the position of 0.5mm offset from the boundary of hard phase and soft phase to hard phase;

[0073] B. When 0.1<the difference of the resistance coefficients of the two phases≤0.25, the ion beam focusing position is at the position of 1mm offset from the boundary of hard phase and soft phase to hard phase;

[0074] C. When 0.25 < the difference between the two-phase polishing resistance coefficients ≤ 0.4, the ion beam focusing position is at a position 1.5 mm offset from the boundary of the hard phase and the soft phase to the hard phase;

[0075] D. When 0.4 < the difference between the two-phase polishing resistance coefficients ≤ 0.6, the ion beam focusing position is at a position 2 mm offset from the boundary of the hard phase and the soft phase to the hard phase.

[0076] When the phase distribution of the heterogeneous high-hardness-difference material is a dispersed distribution of the hard phase and the soft phase, the ion beam focusing position is not specially limited, and the sample center position can be generally selected, the polishing angle is 7.5°-10.5°, and the polishing angle can be selected to be 7.5°, 9° or 10.5°; the polishing time is 1-2 h.

[0077] (2) Determination of polishing voltage

[0078] The polishing resistance coefficient of the heterogeneous high-hardness-difference material is calculated based on the polishing resistance coefficients of the hard phase and the soft phase, and then the argon ion polishing voltage and the polishing time are determined.

[0079] The polishing resistance coefficients of the hard phase and the soft phase are shown in the above table, and the polishing resistance coefficient of the heterogeneous high-hardness-difference material is calculated by the following formula:

[0080] The polishing resistance coefficient of the heterogeneous high-hardness-difference material sample = (the polishing resistance coefficient of the hard phase + the polishing resistance coefficient of the soft phase) ÷ 2.

[0081] The argon ion polishing voltage is determined according to the polishing resistance coefficient of the sample as follows:

[0082] a. When 0.5 < the average value of the polishing resistance coefficient of the sample ≤ 0.75, the argon ion polishing voltage is set to 6 kV;

[0083] b. When 0.3 < the average value of the polishing resistance coefficient of the sample ≤ 0.5, the argon ion polishing voltage is set to 5 kV;

[0084] c. When 0.2 < the average value of the polishing resistance coefficient of the sample ≤ 0.3, the argon ion polishing voltage is set to 4 kV.

[0085] (3) Based on the grinding and polishing equipment designed in the present application, the EBSD sample of the heterogeneous high-hardness-difference material with a qualified calibration rate can be prepared by using the above grinding and polishing process and suitable argon ion polishing process parameters, and the calibration rate of the prepared EBSD sample at the heterogeneous phase interface is not less than 95%.

[0086] Example 2

[0087] In this embodiment, the sample formed after explosive welding of tungsten alloy and copper alloy is taken as an example to specifically illustrate the EBSD sample preparation method of the heterogeneous high-hardness-difference material in Example 1, including the following steps:

[0088] (1) The sample is inlaid into a sample with a diameter of 30 mm and a thickness of 5 mm, and then the sample is placed in a sample groove with a diameter of 30 mm on the sample holder. The air pump is opened, so that the 3 vacuum suction cups in the sample groove firmly adsorb the upper surface of the sample on the sample holder, to ensure that the sample surface is not inclined during subsequent polishing, and the lower surface of the sample is always parallel to the polishing disc, reducing the height difference between heterogeneous phases caused by sample inclination during polishing.

[0089] Then the sample is polished using the polishing disc of the polishing machine. The sample is polished in turn using 400, 800, 1200, 2000 and 5000 grit diamond sandpaper. When polishing, pay attention to let the sandpaper polish the tungsten alloy part first. Then use 1 μm diamond polishing liquid and 0.1 μm silica polishing liquid to polish the sample. The final sample surface roughness Ra≤0.2 μm, and there is almost no height difference between the material interfaces under metallographic microscope observation.

[0090] (2) The mechanically polished sample is subjected to argon ion polishing treatment. The argon ion beam focusing position, argon ion polishing angle, polishing voltage and polishing time are determined based on the distribution of the hard phase tungsten alloy and the soft phase copper alloy and the polishing resistance coefficient.

[0091] The phase distribution of the sample in this example is adjacent distribution of hard phase and soft phase, and the polishing resistance coefficients of tungsten and copper are 0.721 and 0.333 respectively, with a difference of 0.388. For this sample, the ion beam focusing position is 1.5 mm offset to the tungsten alloy part from the tungsten-copper boundary; the argon ion polishing angle is 6°.

[0092] The polishing resistance coefficient of the sample in this example is the average of the polishing resistance coefficients of tungsten and copper, which is 0.527. Based on the empirical value in Example 1, the argon ion polishing voltage is selected as 6 kV, and the polishing time is 1.5 h.

[0093] (3) Based on the argon ion polishing process parameters determined in step (2), the EBSD sample is prepared by using a three-ion beam argon ion polishing device according to the set process parameters.

[0094] The phase distribution and BC diagram of the EBSD test results are shown in Figure 8 It can be seen that there is no problem of analysis rate difference caused by height difference at the boundary between tungsten alloy and copper alloy. The EBSD sample preparation effect of the heterogeneous high-hardness difference material formed after explosive welding of tungsten alloy and copper alloy is better by the method of this example. The calibration rate at the tungsten-copper interface (within 20 μm on both sides of the interface) is 98%, and the points at the boundary between tungsten alloy and copper alloy are perfectly resolved.

[0095] Comparative Example 1

[0096] The sample used in this comparative example is a sample formed after explosive welding of tungsten alloy and copper alloy, which is the same as Example 2, and the only difference from Example 2 is that the ion beam focusing position in step (2) is at the tungsten-copper boundary, not offset by 2 mm to the tungsten alloy part as in Example 2. The rest is the same as Example 2.

[0097] The Kikuchi band contrast image and phase distribution of the EBSD sample prepared in this comparative example are shown in Figure 9 As can be clearly seen from the figure, the argon ion polishing of the upper copper alloy part produces deeper etching pits, the BC map contrast becomes black, and the calibration rate decreases.

[0098] Comparative Example 2

[0099] The sample used in this comparative example is a sample formed after explosive welding of tungsten alloy and copper alloy, which is the same as Example 2, and the only difference from Example 2 is that the voltage of argon ion polishing in step (2) is 6 kV, and the rest is the same as Example 2. The EBSD sample prepared in this comparative example has deeper etching pits in the copper alloy part, and the low-lying part cannot be calibrated, with a calibration rate of 85%. was 7 kV, higher than in Example 2

[0100] Comparative Example 3

[0101] The sample used in this comparative example is a sample formed after explosive welding of tungsten alloy and copper alloy, which is the same as Example 2, and the only difference from Example 2 is that the voltage of argon ion polishing in step (2) is 6 kV, and the rest is the same as Example 2. The EBSD sample prepared in this comparative example has deeper etching pits in the copper alloy part, and the low-lying part cannot be calibrated, with a calibration rate of 85%. was 4 k , lower than in Example 2 6 kV, and the rest is the same as Example 2. The EBSD sample prepared in this comparative example has better resolution in the copper alloy part, but the resolution rate of the tungsten alloy is insufficient, and there is a more obvious mechanical polishing stress, with a calibration rate of 80%.

[0102] Example 3

[0103] This example takes a copper-based metal composite reinforced with molybdenum particles as an example to illustrate the EBSD sample preparation method for heterogeneous high-hardness difference materials, which includes the following steps:

[0104] (1) Embed the sample into a sample with a diameter of 30 mm and a thickness of 5 mm, then place the sample into a 30 mm sample slot on the sample holder, turn on the air pump, and make sure that the 3 vacuum chucks in the sample slot firmly adsorb the upper surface of the sample on the sample holder, to ensure that the sample surface is not tilted during the subsequent polishing process, and the lower surface of the sample is always parallel to the polishing disc, reducing the height difference between heterogeneous phases caused by sample tilting during polishing.

[0105] ​​Then the sample is polished using a polishing disc of a polishing machine, and the sample is polished using diamond sandpaper with a granularity of 400, 800, 1200, 2000 and 5000 in sequence, and then the sample is polished using 1 μm diamond polishing liquid and 0.1 μm silica polishing liquid, and finally the surface roughness Ra of the sample is less than or equal to 0.2 μm, and there is almost no height difference between the material interfaces under the observation of a metallographic microscope.

[0106] (2) The sample polished by the mechanical polishing is subjected to argon ion polishing treatment, and the focusing position of the ion beam, the polishing angle of the argon ion, the polishing voltage and the polishing time are determined based on the phase distribution characteristics and the polishing resistance coefficient of the sample.

[0107] The phase distribution of the sample used in the embodiment is a dispersed distribution of soft phases and hard phases, and therefore the focusing position of the ion beam is not limited, and for the convenience of operation, the focusing position of the ion beam is selected as the center position of the sample, and the polishing angle of the argon ion is 9°.

[0108] The polishing resistance coefficients of molybdenum and copper of the comparative sample are compared, wherein the polishing resistance coefficient of molybdenum is 0.356, the polishing resistance coefficient of copper is 0.333, and the average value of the polishing resistance coefficients is 0.3445, and based on the empirical value in Embodiment 1, the polishing voltage of the argon ion is set to 5 kV, and the polishing time is 1 h.

[0109] (3) Based on the argon ion polishing process parameters determined in step (2), the EBSD sample is prepared by using a three-ion beam argon ion polishing device according to the set process parameters.

[0110] The phase distribution diagram and the BC diagram of the EBSD test result are shown in Figure 10 It can be seen that the points at the boundaries of the molybdenum alloy and the copper alloy are perfectly resolved, and the resolution rate of the method of the embodiment for the copper-based metal composite material reinforced by molybdenum particles is 98%.

[0111] The above disclosure is only several specific embodiments of the present application, and those skilled in the art can make various modifications and changes to the embodiments of the present application without departing from the spirit and scope of the present application, but the embodiments of the present application are not limited thereto, and any changes that can be thought of by those skilled in the art should fall within the protection scope of the present application.

Claims

1. A method of preparing a heterogeneous high hardness differential material EBSD sample, the method comprising: The method comprises the following steps: ​ (1) using a polishing equipment with a vacuum chuck to fix the sample, polishing the sample with heterogeneous high hardness difference to a mirror effect, and the surface roughness Ra of the sample is less than or equal to 0.2 μm; (2) performing argon ion polishing treatment on the polished sample, determining the argon ion beam focusing position and argon ion polishing parameters based on the phase distribution characteristics of the hard phase and the soft phase of the heterogeneous high hardness difference material and the sputtering resistance coefficients of the hard phase and the soft phase; (3) using a three-ion beam argon ion polishing equipment to polish the sample to prepare an EBSD sample according to the argon ion polishing parameters determined in step (2).

2. The method of claim 1, wherein the method further comprises: The mechanical polishing comprises the following steps: The sample is vacuum adsorbed and fixed on a sample holder, the lower surface of the sample is always parallel to the polishing disc, and the sample is polished by using diamond sandpaper with a mesh of 400, 800, 1200, 2000 and 5000 in sequence, and then the sample is polished by using 1 μm diamond polishing liquid and 0.1 μm silicon dioxide polishing liquid in sequence until the surface roughness Ra of the sample is less than or equal to 0.2 μm.

3. The method of claim 1, wherein the method further comprises: Based on the phase distribution characteristics of the hard phase and the soft phase of the heterogeneous high hardness difference material, the argon ion beam focusing position is determined, and the specific method is as follows: ① When the phase distribution of the heterogeneous high hardness difference material is adjacent distribution of the hard phase and the soft phase, the ion beam focusing position of the argon ion polishing is selected to be 0.5-2 mm offset from the boundary of the hard phase and the soft phase to the hard phase; ② When the phase distribution of the heterogeneous high hardness difference material is diffuse distribution of the hard phase and the soft phase, the ion beam focusing position of the argon ion polishing can be selected on the sample surface, without specific position limitation.

4. The method of claim 3, wherein the sample is a heterogeneous high hardness differential material EBSD sample. For the sample with adjacent distribution of the hard phase and the soft phase, the argon ion beam focusing position is further determined based on the difference of the sputtering resistance coefficients of the hard phase and the soft phase, and the specific method is as follows: A. When the difference of the sputtering resistance coefficients of the two phases is less than or equal to 0.1, the ion beam focusing position is 0.5 mm offset from the boundary of the hard phase and the soft phase to the hard phase; B. When 0.1 < the difference of the sputtering resistance coefficients of the two phases < 0.25, the ion beam focusing position is 1 mm offset from the boundary of the hard phase and the soft phase to the hard phase; C. When 0.25 < the difference of the sputtering resistance coefficients of the two phases < 0.4, the ion beam focusing position is 1.5 mm offset from the boundary of the hard phase and the soft phase to the hard phase; D. When 0.4 < the difference of the sputtering resistance coefficients of the two phases < 0.6, the ion beam focusing position is 2 mm offset from the boundary of the hard phase and the soft phase to the hard phase.

5. The method of claim 1, wherein the method further comprises: The sputtering resistance coefficient of the hard phase or the soft phase is calculated by the following formula: Sputtering resistance coefficient = 0.3 × (hardness / 3430) + 0.5 × (inverse of sputtering yield / 2.5) + 0.2 × (thermal conductivity / 401); The sputtering resistance coefficient of the sample is the average value of the sputtering resistance coefficients of the hard phase and the soft phase, which is represented by the following formula: Sample sputtering resistance coefficient = (hard phase sputtering resistance coefficient + soft phase sputtering resistance coefficient) ÷ 2.

6. The method of claim 1, wherein the method further comprises: The argon ion polishing voltage is determined based on the sputtering resistance coefficient of the sample, and the specific method is as follows: a. When 0.5 < the average value of the sputtering resistance coefficient of the sample < 0.75, the argon ion polishing voltage is set to 6 kV; b. When 0.3 < the average value of the sputtering resistance coefficient of the sample < 0.5, the argon ion polishing voltage is set to 5 kV; c. When 0.2 < the average value of the sample's polishing resistance coefficient ≤ 0.3, the argon ion polishing voltage is set to 4kV.

7. The method of claim 1, wherein the method further comprises: Based on the phase distribution characteristics of heterogeneous high-hardness-difference materials, the angle and polishing time for argon ion polishing are determined as follows: I. When the hard phase and soft phase are distributed adjacently in the sample, the polishing angle is 4.5° to 7.5° and the polishing time is 1.5 to 2.5 hours; II. When the hard and soft phases in the sample are diffusely distributed, the polishing angle is 7.5° to 10.5° and the polishing time is 1 to 2 hours.

8. The method of claim 1, wherein the method of preparing a heterogeneous high hardness differential material EBSD sample is characterized by, The main components of the heterogeneous high hardness difference material are at least two of tungsten carbide, tungsten, molybdenum, alumina, silicon, titanium, copper, magnesium, aluminum, and gold.

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