Method and device for determining grain orientation
By measuring the second phase angle on the surface of metallographic samples and performing geometric calculations, combined with image recognition software, the grain orientation can be quickly determined, solving the problems of expensive EBSD equipment and complex sample preparation, and realizing efficient grain orientation characterization and part optimization.
Patent Information
- Application Number
- CN202410630191.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-05-20
- Publication Date
- 2025-11-21
Smart Images
Figure CN120992603A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of materials characterization, and specifically relates to a method and apparatus for determining grain orientation. Background Technology
[0002] To further improve the performance, reduce energy consumption, and increase the thrust-to-weight ratio of aero-engines, advanced manufacturing processes, including laser direct deposition (LDD), are increasingly being adopted in aero-engine manufacturing. During the manufacturing of parts using LDD, the material microstructure undergoes a complex thermal history under high temperature gradients, involving multiple cycles, variable cycles, and rapid heating and cooling. The non-equilibrium metallurgical and thermophysical processes involved are highly complex, resulting in a strong dependence of the final material's microstructure and properties on process conditions. In the manufacturing of key components such as integral bladed disks, casings, load-bearing frames, pressurization drums, or mounting sections using novel metallic materials like titanium alloys and high-temperature alloys, LDD tends to form oriented grain distributions within the material microstructure. This leads to a certain orientation in the material's macroscopic mechanical or chemical properties. When this orientation does not match the part's design requirements, it can negatively impact the overall performance of the part. Therefore, characterizing the grain orientation in the material microstructure is of significant guiding importance for optimizing part structural design and forming process parameters.
[0003] However, the current common method for characterizing grain orientation is backscattered electron diffraction (EBSD). EBSD equipment is complex and expensive, resulting in high operating costs. Furthermore, EBSD requires high sample surface quality, which conventional polishing often fails to meet, necessitating complex polishing techniques such as electrolytic polishing or vibratory polishing, leading to difficult sample preparation and long processing times. Therefore, characterizing grain orientation using EBSD alone cannot fully meet the needs of practical production. Thus, providing a rapid method for determining grain orientation is of high practical value for improving the efficiency of material characterization. Summary of the Invention
[0004] The object of this invention is to provide a method for determining grain orientation, which can determine grain orientation without the aid of EBSD. This invention also provides an apparatus for determining grain orientation.
[0005] According to an embodiment of the present invention, a method for determining grain orientation is provided: providing an image of a metallographic sample, the metallographic sample being configured as a non-deformable alloy, the microstructure of the metallographic sample comprising a matrix and a second phase, the second phase having a habitual plane along the {111} plane direction of the matrix, the second phase being in a strip-like or disk-like structure;
[0006] The method includes the following steps:
[0007] Measure the included angle between the second phases on the surface of the metallographic sample.
[0008] A virtual regular tetrahedron is constructed based on the matrix {111} plane, and the angular relationship between the surface of the metallographic sample and the matrix {111} plane is calculated based on the included angle between the second phases.
[0009] This method utilizes the characteristic that the second phase in a partial alloy matrix is generated along the habit plane. By measuring the angular relationship of the second phase on the metallographic surface, the relative angle between the metallographic surface and the habit plane is determined by geometric calculation, thereby determining the grain orientation.
[0010] Furthermore, in some embodiments, the substrate is a bcc or fcc structure.
[0011] Furthermore, in some embodiments, the method for calculating the angular relationship between the metallographic sample surface and the matrix {111} plane based on the included angle between the second phases is as follows:
[0012] When the second phase has a first direction and a second direction, and the first direction and the second direction are perpendicular to each other, the angle between the surface of the metallographic sample and the plane of the matrix {111} is .
[0013] When the second phase has a third direction a, a fourth direction b, and a fifth direction c, and the angle between a and b is α, the angle between b and c is β, and the angle between c and a is γ; let the side edges of the virtual tetrahedron be x, y, and z, and the lines of intersection between the metallographic sample surface and the side surface of the virtual tetrahedron be d, e, and f; the angle between x and d is α1, the angle between x and e is α2, the angle between y and e is β1, the angle between y and f is β2, the angle between z and f is γ1, and the angle between z and d is γ2; solve the trigonometric function equation system:
[0014] α1 + γ2 = 120°;
[0015] α² + β² = 120°;
[0016] γ1+β1=120°;
[0017] cos(α1)*cos(γ2)+sin(α1)*sin(γ2)*k-cos(α)=0;
[0018] cos(β1)*cos(α2)+sin(β1)*sin(α2)*k-cos(β)=0;
[0019] cos(γ1)*cos(β2)+sin(γ1)*sin(β2)*k-cos(γ)=0;
[0020] Where k = cos(70°32');
[0021] The values of α1, α2, β1, β2, γ1, and γ2 are obtained, thereby determining the angular relationship between the surface of the metallographic sample and the matrix {111} plane.
[0022] Based on the positional relationship between the plane and the tetrahedron, there are two positional relationships between the plane containing the metallographic sample surface and the virtual tetrahedron of the matrix {111} plane: When the plane containing the metallographic sample surface is parallel to the two non-intersecting edges of the virtual tetrahedron, the intersection line of the plane containing the metallographic sample surface and the surface of the virtual tetrahedron forms a rectangle. In this case, a second phase with two directions that are perpendicular to each other can be observed on the surface of the metallographic sample, and this positional relationship is uniquely determined. When the plane containing the metallographic sample surface does not satisfy the above parallel relationship, the plane containing the metallographic sample surface is translated to construct a triangular plane that intersects with the surface of the virtual tetrahedron, which represents the a, b, and c directions of the second phase. Through the angular relationship of a, b, and c and the tetrahedral angle theorem, the angular relationship between the plane containing the metallographic sample surface and the matrix {111} plane can be calculated by solving a system of six quadratic trigonometric function equations, thereby determining the grain orientation.
[0023] Furthermore, in some embodiments, the metallographic sample includes a titanium alloy, low-carbon steel, or an Al-Cu alloy; wherein the titanium alloy is an α+β type titanium alloy or a near-β type titanium alloy; the second phase in the low-carbon steel is lath martensite; and the second phase in the Al-Cu alloy is an ω phase. The habit planes of these alloys are all close to the {111} plane of the matrix.
[0024] Furthermore, in some embodiments, the titanium alloy includes TC17, TC18, TC19, TC21, TB6, TB7 or TB8 alloys.
[0025] Furthermore, in some embodiments, the images of the metallographic sample include etched metallographic micrographs or scanning electron micrographs.
[0026] According to another aspect of the present invention, an apparatus for determining grain orientation is provided. The apparatus includes a memory and a processor. The memory stores metallographic image recognition software and a calculation program. When the metallographic image recognition software is executed by the processor, it can identify grains in an input metallographic image, as well as the matrix and second phase in the grains. When the calculation program is executed by the processor, it can perform the method for determining grain orientation provided in any of the foregoing embodiments. Attached Figure Description
[0027] Figure 1 This is a schematic diagram of the distribution of the second phase within a matrix grain in one embodiment;
[0028] Figure 2 This is a schematic diagram showing the positional relationship between the virtual tetrahedron established by the {111} plane of the substrate and the surface of the metallographic sample in one embodiment.
[0029] Figure 3 This is a schematic diagram of the second phase distribution within the matrix grains in another embodiment;
[0030] Figure 4 A schematic diagram showing the positional relationship between the virtual tetrahedron established on the substrate {111} plane and the surface of the metallographic sample in another embodiment.
[0031] The purpose of the above-described drawings is to provide a detailed description of the present invention so that those skilled in the art can understand the technical concept of the invention, and not to limit the invention. For the sake of brevity, the above-described drawings only schematically depict the structures related to the technical features of the present invention, and do not depict the complete structure and all details strictly according to actual scale. Detailed Implementation
[0032] The present invention will now be described in further detail with reference to specific embodiments and accompanying drawings.
[0033] The term "embodiment" as used herein means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment herein. The phrase appearing in various places in the specification does not necessarily refer to the same embodiment, nor is it limited to mutually exclusive, independent, or alternative embodiments. Those skilled in the art will understand that the embodiments herein can be combined with other embodiments without structural conflict. In the description herein, "a plurality of" means at least two.
[0034] The design and manufacturing requirements for components in new aero-engines are becoming increasingly stringent. New forming processes such as laser direct deposition (LDD) are replacing some traditional processing methods like casting and forging, and are being applied to the manufacture of key components such as integral bladed disks, casings, load-bearing frames, pressurization drums, and mounting sections. The microstructure evolution of components manufactured using these new technologies differs significantly from that of components manufactured using traditional processes. For example, in LDD, a high-energy laser beam melts synchronously fed metal powder and part of the matrix, forming a moving, unsteady molten metal pool. This pool rapidly solidifies under extremely high temperature gradients, depositing point by point, scanning line by line, and layer by layer to ultimately form a solid part. The non-equilibrium physical metallurgy and thermophysical processes involved in this technology are highly complex. The deposited material undergoes a short thermal history of multiple cycles, variable cycles, and intense heating and cooling, resulting in a unique microstructure that exhibits a strong dependence on process conditions. The directionality of the forming process also imparts a certain orientation to the grains within the part. For materials such as titanium alloys and aluminum alloys, this grain orientation leads to a certain orientation in their macroscopic properties. For example, different grain orientations can lead to significant anisotropy in the strength, elastic modulus, and corrosion resistance of materials. If the weak points caused by grain orientation coincide with the main load-bearing direction of a part, it will negatively impact the part's lifespan and reliability. Therefore, characterizing the grain orientation of part materials is of great significance for guiding the optimization of part manufacturing processes and structural design.
[0035] Grain orientation is typically characterized using backscattered electron diffraction (EBSD). However, EBSD requires expensive specialized equipment and demands high sample quality. Conventional polishing processes cannot meet the sample quality requirements of EBSD, necessitating more complex polishing methods such as electrolytic polishing and vibratory polishing. This results in a long detection cycle and high cost for EBSD.
[0036] To address the aforementioned problems, embodiments of the present invention provide a method for determining grain orientation, which can utilize the geometric features of the material's microstructure and ordinary metallographic sample images to characterize the grain orientation of materials with specific microstructure characteristics.
[0037] This invention, verified through extensive experimental testing and metallographic sampling, combined with theoretical calculations, provides a method for determining grain orientation that can characterize the grain orientation of non-deformable alloys having a matrix and a second phase, wherein the second phase has a habit plane along the {111} crystal plane of the matrix, and the second phase is strip-shaped or disk-shaped. Specifically, the habit plane of the second phase along the {111} crystal plane of the matrix refers to an angular deviation between the habit plane of the second phase and the {111} crystal plane of the matrix not exceeding 10°. In a preferred embodiment, the matrix has a bcc or fcc structure, which yields more accurate characterization results. α+β type titanium alloys such as TC17, TC18, TC19, and TC21, near-β type titanium alloys such as TB6, TB7, and TB8, as well as low-carbon steel with lath martensite or Al-Cu alloys with the ω phase as the second phase, all satisfy this angular relationship of the habit plane.
[0038] In one embodiment, a certain grade of cast titanium alloy is used as a sample, and its grain orientation is characterized. The method includes the following steps:
[0039] First, the metallographic sample was ground and polished, and the surface was etched. The surface microstructure was then photographed under a metallographic microscope. The microstructure within one grain is shown below. Figure 1 As shown, the material matrix 1 is the β phase, and the second phase 2α precipitates in a lamellar shape. Measurements of the included angle between the two phases 2 indicate that the second phase 2 is distributed along mutually perpendicular directions 3 and 4. Here, RD and TD are two calibration directions on the plane containing the metallographic sample surface.
[0040] Next, establish such Figure 2 The virtual tetrahedron ABCD (i.e., an imaginary tetrahedron formed by four crystal faces in the {111} family, such as the tetrahedron formed by (111), (1-1-1), (-11-1), and (-1-11) crystal faces) is shown in the diagram. The {111} crystal face is the habitual plane for the formation of the α phase. Directions 3 and 4 reflect two crystal faces with different directions in the {111} family. It can be seen that only when the plane EFGH on the surface of the metallographic sample is parallel to the two opposite edges AB and CD of the virtual tetrahedron ABCD, the intersection lines EF and GH are perpendicular to EH and FG respectively, which can lead to the second phase 2 being perpendicular to each other. At this time, the angle between the plane EFGH on the surface of the metallographic sample and the plane ACD of the (111) β phase matrix is equal to the angle between edge AB and plane ACD. Through geometric calculation, it can be known that its angle is... Therefore, the angular relationship between the grain and the surface of the metallographic sample can be determined.
[0041] In another grain of this sample, the microstructure is as follows: Figure 3 As shown. Phase 2 has three different directions: a, b, and c.
[0042] Establish as Figure 4 The virtual tetrahedron ABCD is formed by the {111} mirror group of the β-phase matrix. The {111} crystal planes are habitual planes for the formation of the α phase. Directions a, b, and c reflect two crystal planes with different directions in the {111} crystal plane family. It can be seen that the plane IJK on the surface of the metallographic sample intersects with the three sides of the virtual tetrahedron ABCD to form the extension directions a, b, and c of the second phase 2. Let the angle between a and b be α, the angle between b and c be β, and the angle between a and c be γ. Let the angles between edge AB and a and b of the virtual tetrahedron ABCD be α1 and α2, respectively; the angles between edge AD and b and c be β1 and β2, respectively; and the angles between edge AC and c and a be γ1 and γ2, respectively.
[0043] According to the tetrahedral angle theorem, we have:
[0044] α1 + γ2 = 120°;
[0045] α² + β² = 120°;
[0046] γ1+β1=120°;
[0047] cos(α1)*cos(γ2)+sin(α1)*sin(γ2)*k-cos(α)=0;
[0048] cos(β1)*cos(α2)+sin(β1)*sin(α2)*k-cos(β)=0;
[0049] cos(γ1)*cos(β2)+sin(γ1)*sin(β2)*k-cos(γ)=0;
[0050] Where k = 1 / 3, is the dihedral angle of a regular tetrahedron.
[0051] By using MATLAB or other computational software to solve the above six-element quadratic trigonometric function equations, the angles α1, α2, β1, β2, γ1, and γ2 can be obtained, thereby determining the angular relationship between the β-phase matrix and the surface of the metallographic sample, and further determining the orientation of this grain.
[0052] In other embodiments, the above method is not limited to identifying grain orientation in non-deformed titanium alloys having α and β phases, but can also be used to identify grain orientation in other alloys with {111} habit planes, such as low-carbon steel with lath martensite or Al-Cu alloys with ω phase as the second phase.
[0053] Another embodiment of the present invention provides an apparatus for determining grain orientation. The apparatus includes a memory and a processor. The memory stores metallographic image recognition software and a calculation program. The processor executes the metallographic image recognition software to automatically identify grains and the matrix and second phase within the grains in an input metallographic image. The processor executes the calculation program to measure the included angle of the second phase within the grains according to the method described in the foregoing embodiment, and determines the angular relationship between the matrix grains and the metallographic surface through geometric calculations, thereby determining the orientation of all grains within the metallographic image range. The metallographic image can be a metallographic microscope photograph of an etched metallographic sample or a scanning electron microscope photograph.
[0054] The method for determining grain orientation provided in the above embodiments can identify the grain orientation in alloy samples with specific microstructure characteristics without the need for expensive EBSD equipment and complex and precise sample preparation processes. It can effectively improve the characterization efficiency of samples from novel manufacturing processes such as laser direct deposition and optimize the design and manufacturing process of parts.
[0055] The purpose of the above embodiments is to provide a further detailed description of the present invention in conjunction with the accompanying drawings, so that those skilled in the art can understand the technical concept of the present invention. Within the scope of the present invention, optimizations or equivalent substitutions of the methods or steps involved, as well as combinations of implementation methods in different embodiments without causing structural or principle conflicts, all fall within the protection scope of the present invention.
Claims
1. A method for determining grain orientation, characterized in that, Images of metallographic samples are provided, the metallographic samples being configured as non-deformable alloys, the microstructure of the metallographic samples comprising a matrix and a second phase, the second phase having habitual planes along the {111} plane direction of the matrix, the second phase being in the form of strip-shaped or disc-shaped structures; The method includes the following steps: The included angle between the second phases within the same grain on the surface of the metallographic sample was measured. A virtual regular tetrahedron is constructed based on the matrix {111} plane, and the angular relationship between the surface of the metallographic sample and the matrix {111} plane is calculated based on the included angle between the second phases.
2. The method for determining grain orientation according to claim 1, characterized in that, The matrix is a bcc or fcc structure.
3. The method for determining grain orientation according to claim 1 or 2, characterized in that, The method for calculating the angular relationship between the surface of the metallographic sample and the {111} plane of the substrate based on the included angle between the second phases is as follows: When the second phase has a first direction and a second direction, and the first direction and the second direction are perpendicular to each other, the angle between the surface of the metallographic sample and the plane of the matrix {111} is . When the second phase has a third direction a, a fourth direction b, and a fifth direction c, and the angle between a and b is α, the angle between b and c is β, and the angle between c and a is γ; let the side edges of the virtual tetrahedron be x, y, and z, and the lines of intersection between the metallographic sample surface and the side surface of the virtual tetrahedron be d, e, and f; the angle between x and d is α1, the angle between x and e is α2, the angle between y and e is β1, the angle between y and f is β2, the angle between z and f is γ1, and the angle between z and d is γ2; solve the trigonometric function equation system: α1 + γ2 = 120°; α2+β2＝120°； γ1+β1=120°; cos(α1)*cos(γ2)+sin(α1)*sin(γ2)*k-cos(α)=0; cos(β1)*cos(α2)+sin(β1)*sin(α2)*k-cos(β)=0; cos(γ1)*cos(β2)+sin(γ1)*sin(β2)*k-cos(γ)=0; Where k = 1 / 3; The values of α1, α2, β1, β2, γ1, and γ2 are obtained, thereby determining the angular relationship between the surface of the metallographic sample and the matrix {111} plane.
4. The method for determining grain orientation according to claim 1 or 2, characterized in that, The metallographic samples include titanium alloys, low-carbon steel, or Al-Cu alloys; in, The titanium alloy is an α+β type titanium alloy or a near-β type titanium alloy; The second phase in the low-carbon steel is lath martensite; The second phase in the Al-Cu alloy is the ω phase.
5. The method for determining grain orientation according to claim 4, characterized in that, The titanium alloy includes TC17, TC18, TC19, TC21, TB6, TB7 or TB8 alloys.
6. The method for determining grain orientation according to claim 1 or 2, characterized in that, The images of the metallographic samples include etched metallographic micrographs or scanning electron micrographs.
7. An apparatus for determining grain orientation, characterized in that, The device includes a memory and a processor. The memory stores metallographic image recognition software and a calculation program. When the metallographic image recognition software is executed by the processor, it can identify grains in an input metallographic image, as well as the matrix and second phase in the grains. When the calculation program is executed by the processor, it can implement the method for determining grain orientation as described in any one of claims 1 to 6.