Preparation method of transmission electron microscope sample for micro-nano deformation analysis of selected area

Abstract

The invention discloses a preparation method of a transmission electron microscope sample for micro-nano deformation analysis of a selected area, which comprises the following steps: cutting and grinding: cutting a semi-circular piece from an alloy sample, and grinding the semi-circular piece to the thickness of 30 microns; testing micro Vickers hardness: firstly, overlapping and tightly adhering the ground semicircular sheets, carrying out cold inlaying treatment on the tightly adhered multilayer semicircular sheets, grinding and polishing the cold inlaying block, keeping the polished surface as a flat surface of the multilayer semicircular surfaces in the grinding and polishing process, and then carrying out micro hardness test on the polished cold inlaying block; dissolving the cold inlay block: dissolving the cold inlay block and glue, separating and taking out the overlapped and adhered semicircular sheets; and focused ion beam processing: selecting a micro Vickers hardness indentation for each semi-circular sheet, and performing focused ion beam processing to obtain a processed sample, namely the transmission sample. The preparation method disclosed by the invention is suitable for the TiAl alloy, particularly the high Nb-TiAl alloy, and has a wide application prospect for researching the deformation mechanism of the high Nb-TiAl alloy.

Description

Technical Field

[0001] This disclosure generally relates to a material preparation and characterization method, and particularly to a transmission electron microscope (TEM) sample preparation method for micro-nano deformation analysis of selected regions, especially to a TEM sample preparation method for micro-nano deformation analysis of high Nb-TiAl alloys in selected regions. Background Technology

[0002] With the development of high-performance structural materials, traditional macroscopic mechanical property testing methods are no longer sufficient to meet the research needs of materials at the microscale. The study of micro / nano mechanical properties has become a hot topic in recent years, with testing methods including micro-Vickers hardness, micropillar compression, and nanoindentation techniques. Micro / nano mechanical testing techniques can be used to study the mechanical properties and deformation mechanisms of fine precipitates in alloys, such as ω-phase in β-TiAl alloys. o Phase studies are also an important direction in the study of micro- and nano-mechanical properties, especially in the study of the micro- and nano-mechanical properties of TiAl alloys.

[0003] β-TiAl alloys are promising lightweight high-temperature structural materials used in low-pressure turbine blades for aero-engines. The β phase in β-TiAl alloys has a disordered body-centered cubic structure at high temperatures. However, during cooling to room temperature, the β phase transforms into an ordered B2-type β phase. o Furthermore, within the service temperature range of 700-900°C, the βo phase, due to its thermodynamic instability, readily precipitates a series of ordered ω phases (including ω′, ω″, and others). o (Mainly). ω o The phase has a relatively complex structure, with space group P63 / mmc, and is an ordered hexagonal structure, generally considered a brittle phase. ω o The influence of relative alloy properties is very complex, and a systematic study of ω is needed. o The mechanical properties and deformation compatibility of the phase are of great significance for improving the mechanical properties of TiAl alloys. However, current understanding of ω... o Research on phase mechanical behavior remains very limited. This is mainly due to ω o The phase is typically dispersed at the nanoscale from β o In a phase matrix, the particles are small and dispersed, making it difficult to directly measure their individual mechanical properties.

[0004] Micrometer-level ω o The mechanical properties of the phase can be measured using nanoindentation, micro-Vickers hardness, and micropillar compression techniques. Due to ω... o from β o There are four variants during phase precipitation, each with a different orientation, therefore for ω o The study of phase elastic-plastic anisotropic response relies heavily on micro-nano mechanical testing techniques. Meanwhile, the study of ω... oCharacterizing phase plastic deformation is crucial. Traditional transmission sample preparation techniques struggle to capture the effects of phase plastic deformation through ω. o The microstructure characteristics after deformation using micro / nano technology. However, the method for processing transmission samples using focused ion beam technology is time-consuming and expensive. Therefore, in the preparation of transmission samples, there is a need to invent a low-cost processing method that can characterize ω. o Methods for preparing phase deformation characteristics.

[0005] However, there are still few studies specifically on this topic. For example, Chinese patent CN118961271A discloses a method for preparing ultrathin TEM slide samples, but it is aimed at the layered structure of MoO3 nanosheets. As is known to those skilled in the art, the macroscopic properties of MoO3 and the TiAl alloy targeted by this invention are quite different. As the thickness is reduced to the level of microscopic observation, the difference in properties will become more and more significant. Blindly adopting this method will lead to a significant decrease in the success rate of slide preparation and poor observation results. Summary of the Invention

[0006] In view of this, the present invention discloses a transmission electron microscope (TEM) sample preparation method for selected area micro-nano deformation analysis, and in particular a TEM sample preparation method for selected area micro-nano deformation analysis of high Nb-TiAl alloys.

[0007] According to one aspect of this disclosure, a method for preparing a transmission sample for efficiently characterizing the microstructure of the ωo phase after micro / nano processing is provided, comprising the following steps: First, by wire cutting, 10 semi-circular pieces with a diameter of 3 mm and a thickness of 0.3 mm are cut from the heat-treated alloy, and ground to a thickness of 30 μm; then, the 10 pieces are mounted by cold mounting and ground and polished; after grinding and polishing, a micro-Vickers hardness test is performed on the pieces; after the test, the cold mounting block is dissolved with acetone and the pieces are removed; finally, the pieces are processed by focused ion beam processing, in which several regions can be processed on one piece, and the processed piece is the transmission sample.

[0008] According to one aspect of this disclosure, a method for preparing transmission electron microscopy (TEM) samples for micro / nano deformation analysis of selected regions is provided, characterized by comprising the following steps: (1) Cutting and grinding: The heat-treated alloy sample is wire-cut to cut a semi-circular piece and then ground to a thickness of 30 μm. In particular, the force should be even during the grinding process of the semi-circular piece, otherwise the semi-circular piece will break and peel off during the grinding process, affecting the experimental results. (2) Micro Vickers hardness test: First, the ground semicircular pieces are overlapped and glued together with glue. The glued multi-layered semicircular pieces are then cold-mounted. The resulting cold-mounted blocks are then ground and polished. During the grinding and polishing process, the polished surface is kept as a flat surface of the multi-layered semicircular surfaces (i.e., Figure 1(the plane indicated by the arrow in a), and then perform microhardness testing on the polished cold-mounted block. The reason why the semicircular pieces need to be overlapped, bonded, cold-mounted, ground, and polished before the micro-nano mechanical test is mainly because bonding and cold-mounting fix the semicircular pieces; grinding and polishing are for the purpose of facilitating more accurate selection of position during testing. (3) Dissolving the cold inlay block: Dissolve the cold inlay block with glue, separate and remove the overlapping and glued semicircular pieces; (4) Focused ion beam processing: For each semicircular piece, select the micro Vickers hardness indentation area to be characterized and perform focused ion beam processing. The processed sample is the transmission sample.

[0009] According to an embodiment of the present invention, in the transmission electron microscope sample preparation method, in the cutting and grinding step: a total of 10 semi-circular pieces with a diameter of 3 mm and a thickness of 0.3 mm are cut, and the semi-circular pieces are ground to a thickness of 30 μm using 400#, 800#, 1500# and 2000# alumina sandpaper in sequence.

[0010] According to an embodiment of the present invention, in the transmission electron microscopy sample preparation method, in the micro Vickers hardness test step: the adhesive is 502 adhesive, the test position is the area near the middle of the semi-circular straight surface of each layer, 10 ω phase positions are selected in this area for testing, and the test force is selected as 100 g / f.

[0011] According to one embodiment of the present invention, in the transmission electron microscopy sample preparation method, the cold mosaic block is dissolved using acetone as the reagent.

[0012] According to an embodiment of the present invention, the transmission electron microscopy sample preparation method includes focused ion beam processing: for each of the semicircular sections, a suitable micro-Vickers hardness indentation is selected, and focused ion beam processing is performed; the processed sample is the transmission sample.

[0013] According to one embodiment of the present invention, the alloy is a TiAl alloy, with an Al content of 35-45% by atomic percentage (at.%), and the balance being Ti element and unavoidable impurities; preferably, the TiAl is a high Nb-TiAl alloy, that is, with an Al content of 35-45% and an Nb content of 5-20% by atomic percentage, and the balance being Ti element and unavoidable impurities; more preferably, the high Nb-TiAl alloy has an Al content of 35-42% and an Nb content of 10-20% by atomic percentage, and also contains one or more elements selected from the group consisting of B, C, Y, Zr, V, Cr, Mo, and W, each with a content of 0.05-0. The high Nb-TiAl alloy, by atomic percentage, has an Al content of 35-40%, an Nb content of 12-16%, and also contains one or more elements selected from the group consisting of B, C, Y, Zr, V, Cr, Mo, and W, each with a content of 0.05-0.2 at.%, the balance being Ti and unavoidable impurities; even more preferably, the high Nb-TiAl alloy, by atomic percentage, has an Al content of 35-40%, an Nb content of 12-16%, and also contains B, each with a content of 0.05-0.1 at.%, the balance being Ti and unavoidable impurities.

[0014] According to one embodiment of the present invention, the preparation method of the present invention is for Ti-38Al-15Nb-0.1B.

[0015] According to one embodiment of the present invention, microhardness tests can be performed at 10 locations in the middle region of the straight edge of each semicircular piece.

[0016] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows: (1) This invention can prepare a material containing multiple ω by directly performing micro Vickers hardness testing on the straight edge of a 30μm thick semicircular sheet and then processing the appropriate indentation with a focused ion beam. o Transmission samples with phase-deformed thin regions. Currently, the common preparation method involves cutting out the indented area and soldering it to a copper mesh using Pt. Although both methods utilize focused ion beam technology, the common methods are costly and cumbersome. The transmission sample prepared by this invention can contain multiple deformed thin regions in a single sample, significantly improving efficiency.

[0017] (2) The preparation method of the present invention is specifically for TiAl alloys, and is particularly suitable for studying ω in TiAl alloys. oThe ω phase exhibits different orientations within the alloy, demonstrating high specificity and profound significance for the study of deformation mechanisms in the TiAl alloy field. In particular, it is crucial to understand that different orientations in TiAl alloys result in varying deformation mechanisms under the influence of a micro-Vickers indenter, leading to different microstructures. Therefore, the presence of ω phases with different orientations at different locations within the same sample is highly significant. o Phase deformation characteristics are important for studying ω o The phase deformation mechanism is of great help.

[0018] (3) The experimental process of this invention is strictly followed, the prepared transmission sample is easy to preserve, and this invention is relatively simple and easy to apply in actual production. Moreover, this invention is expected to be extended to the characterization study of selected micro-nano deformation regions of other alloys with similar physicochemical properties to TiAl alloy. Attached Figure Description

[0019] The above and other objects, features, and advantages of this disclosure will become more apparent from the more detailed description of the embodiments thereof in conjunction with the accompanying drawings. The drawings are provided to further illustrate the embodiments of this disclosure and form part of the specification. They are used together with the embodiments of this disclosure to explain the disclosure and do not constitute a limitation thereof. In the drawings, the same reference numerals generally represent the same components or steps.

[0020] Figure 1 (a) is a schematic diagram of the TiAl alloy semicircular sheet being ground to a thickness of 30 μm in an embodiment of the present invention; (b) is a schematic diagram of the microhardness test performed after multiple layers of semicircular sheets are overlapped, bonded, and inlaid; (c) is a schematic diagram of the individual semicircular sheet after the inlay block has been dissolved following the microhardness test. Figure 2 This is an optical microscope image of the mounted sample after microhardness testing in an embodiment of the present invention. Figure 3 (a) is a scanning image of the microhardness indentation of a single-layer semi-circular disc in an embodiment of the present invention; (b) is a scanning image of the microhardness indentation after being processed by a focused ion beam. Detailed Implementation

[0021] Hereinafter, exemplary embodiments according to the present disclosure will be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of the present disclosure, and not all embodiments of the present disclosure, and it should be understood that the present disclosure is not limited to the exemplary embodiments described herein. Example

[0022] This embodiment uses a TiAl alloy with a nominal composition of Ti-38Al-15Nb-0.1B (atomic percentage); the preparation of the TiAl alloy is achieved through the following steps: Ingredients: Sponge titanium, Nb-Al master alloy, high-purity aluminum and high-purity boron are prepared into a 50-gram sample according to the component ratio of 46.9 at. % Ti, 38 at. % Al, 15 at. % Nb and 0.1 at. % B and mixed evenly. Melting and casting ingots: The sample from step (1) is placed on the crucible of a vacuum non-consumable arc melting furnace and melted into button ingots; Heat treatment: The button ingots are placed in a furnace, heated to 1250℃ and kept at that temperature for 4 hours, then slowly cooled to 800℃ and then air-cooled to room temperature.

[0023] After obtaining the heat-treated sample, the sample preparation method for transmission electron microscopy (TEM) used for micro / nano deformation analysis of selected areas is then introduced, which includes the following steps: (1) Cutting and grinding: The heat-treated alloy sample was wire-cut into 10 semicircular pieces, each 3 mm in diameter and 0.3 mm thick. These semicircular pieces were then successively ground using 400#, 800#, 1500#, and 2000# alumina sandpaper until a thickness of 30 μm was achieved. Figure 1 As shown in (a); (2) Micro Vickers hardness test: First, such as Figure 1 As shown in (b), the ground semicircular pieces were overlapped and bonded together using 502 glue. The bonded multi-layered semicircular pieces were then cold-mounted, and the cold-mounted blocks were ground and polished. During this process, the polished surface was kept flat, representing the surface of the multi-layered semicircles. A microhardness test was then performed on the polished sample. The test location was the area near the center of each layer of the flat semicircle, with 10 ω phase positions selected for testing. A test force of 100g was used. The optical microscope image of the mounted sample after the microhardness test is shown below. Figure 2 As shown.

[0024] (3) Dissolving cold-mounted blocks: Dissolve the cold-mounted blocks with 502 glue using acetone, separate and remove the overlapping and glued semicircular pieces, as shown. Figure 1 As shown in (c).

[0025] (4) Focused ion beam processing: like Figure 3 (a) shows a scanned image of the microhardness indentation region of a single-layer semicircular disc. For each semicircular disc, a suitable microVickers hardness indentation was selected, and focused ion beam processing was performed. The processed sample is the transmission sample. The scanned image of the microhardness indentation region after focused ion beam processing is shown in Figure 1. Figure 3 As shown in (b).

[0026] As described in this embodiment, the present invention can obtain a transmission sample containing multiple deformed thin regions and reduce the average cost of sample preparation. The basic principles of this disclosure have been described above with reference to specific embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in this disclosure are merely examples and not limitations, and should not be considered as essential features of each embodiment of this disclosure. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not limit the scope of this disclosure to the necessity of employing the aforementioned specific details for implementation.

[0027] The block diagrams of devices, apparatuses, devices, and systems disclosed herein are merely illustrative examples and are not intended to require or imply that they must be connected, arranged, or configured in the manner shown in the block diagrams. As those skilled in the art will recognize, these devices, apparatuses, devices, and systems can be connected, arranged, and configured in any manner. Words such as “comprising,” “including,” “having,” etc., are open-ended terms meaning “including but not limited to,” and are used interchangeably with them. The terms “or” and “and” as used herein refer to the terms “and / or,” and are used interchangeably with them unless the context clearly indicates otherwise. The term “such as” as used herein refers to the phrase “such as but not limited to,” and is used interchangeably with it.

[0028] It should also be noted that in the apparatus, devices, and methods of this disclosure, the components or steps can be disassembled and / or recombined. These disassemblies and / or recombinations should be considered as equivalent solutions to this disclosure.

[0029] In this article, modifiers without quantifiers, such as "first" and "second," are intended to distinguish different components / parts / circuits / modules / devices / steps, rather than to emphasize order, positional relationship, importance, or priority. In contrast, modifiers with quantifiers, such as "first" and "second," can be used to emphasize the order, positional relationship, importance, or priority of different components / parts / circuits / modules / devices / steps.

[0030] The above description of the disclosed aspects is provided to enable any person skilled in the art to make or use this disclosure. Various modifications to these aspects will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other aspects without departing from the scope of this disclosure. Therefore, this disclosure is not intended to be limited to the aspects shown herein, but rather to be carried out within the widest scope consistent with the principles and novel features disclosed herein.

[0031] The above description has been given for purposes of illustration and description. Furthermore, this description is not intended to limit the embodiments of this disclosure to the forms disclosed herein. Although numerous exemplary aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, alterations, additions, and sub-combinations therein.

Claims

1. A method for preparing transmission electron microscopy (TEM) samples for micro / nano deformation analysis of selected regions, characterized in that, Includes the following steps (1) Cutting and grinding: The alloy sample is wire cut to cut a semi-circular piece and then ground to a thickness of 30μm; (2) Micro Vickers hardness test: First, the ground semicircular pieces are overlapped and bonded together with glue to form multiple layers. The bonded multi-layer semicircular pieces are then cold-mounted to obtain a cold-mounted block. The obtained cold-mounted block is then ground and polished. During the grinding and polishing process, the polished surface is kept as a straight surface of the semicircular surface of the multi-layer semicircular pieces. Then, the polished cold-mounted block is subjected to a microhardness test. (3) Dissolve the cold inlay block: Dissolve the cold inlay block with the glue, separate and remove the overlapping and glued semicircular pieces. (4) Focused ion beam processing: For each of the semicircular pieces, select the micro Vickers hardness indentation area to be characterized and perform focused ion beam processing. The processed semicircular piece is the transmission sample.

2. The method for preparing a transmission electron microscope sample according to claim 1, characterized in that, In step (1) cutting and grinding: a total of 10 semicircular pieces with a diameter of 3mm and a thickness of 0.3mm were cut, and the semicircular pieces were ground to a thickness of 30μm using 400#, 800#, 1500# and 2000# alumina sandpaper.

3. The method for preparing a transmission electron microscope sample according to claim 1, characterized in that, In step (2) of the micro Vickers hardness test: the adhesive is 502 adhesive, and the test location is the area near the middle of the semi-circular flat surface of each layer, where 10 ω points are selected. o The phase position was tested, and the test force was set to 100 grams.

4. The method for preparing a transmission electron microscope sample according to claim 1, characterized in that, In step (3), the reagent used to dissolve the cold-mounted block is acetone.

5. The method for preparing a transmission electron microscope sample according to claim 1, characterized in that, The preparation method described herein is applicable to TiAl alloys, wherein the Al content is 35-45% by atomic percentage, and the balance is Ti and unavoidable impurities.

6. The method for preparing a transmission electron microscope sample according to claim 5, characterized in that, The TiAl is a high-Nb-TiAl alloy, meaning that, by atomic percentage, the Al content is 35-45%, the Nb content is 5-20%, and the balance is Ti and unavoidable impurities.

7. The method for preparing a transmission electron microscope sample according to claim 6, characterized in that, The high Nb-TiAl alloy, by atomic percentage, has an Al content of 35-42%, an Nb content of 10-20%, and also contains one or more elements selected from the group consisting of B, C, Y, Zr, V, Cr, Mo, and W, with their contents independently ranging from 0.05 to 0.5 at.%, and the balance being Ti and unavoidable impurities.

8. The method for preparing a transmission electron microscope sample according to claim 7, characterized in that, The high Nb-TiAl alloy, by atomic percentage, has an Al content of 35-40%, an Nb content of 12-16%, and also contains one or more elements selected from the group consisting of B, C, Y, Zr, V, Cr, Mo, and W, with their contents being 0.05-0.2 at.% independently of each other, with the balance being Ti and unavoidable impurities.

9. The method for preparing a transmission electron microscope sample according to claim 8, characterized in that, The high Nb-TiAl alloy, by atomic percentage, has an Al content of 35-40%, an Nb content of 12-16%, and also contains B, with a content of 0.05-0.1 at.%, and the balance being Ti and unavoidable impurities. It underwent heat treatment before being prepared as a transmission electron microscopy sample.

10. The method for preparing a transmission electron microscope sample according to claim 9, characterized in that, The high Nb-TiAl alloy is Ti-38Al-15Nb-0.1B.

Images