Metal surface strain distribution characterization method

Abstract

The invention relates to the technical field of microscopic analysis of metal materials, in particular to a metal surface strain distribution characterization method. The method comprises the following steps of: (1) etching a square grid on the surface of a metal matrix by adopting a standard photoetching process before deformation of the metal matrix, wherein the side length of the grid is 5-40 microns; (2) depositing a Ni layer with the thickness of 60-80nm on the surface of the metal matrix on which the square grid is positioned by adopting an electron beam evaporation system; (3) stripping the Ni layer outside the square mesh from the metal matrix, and leaving a square mesh consisting of Ni on the surface of the metal matrix; and (4) after the metal matrix is deformed, observing the deformation degree of the square grid through a laser scanning confocal microscope to reflect the real strain of the local area of the surface of the metal matrix. The method solves or partially solves the problem that the metal material is difficult to visually reflect the real strain distribution of the surface on the macroscopic level.

Description

Technical Field

[0001] This invention relates to the technical field of microscopic analysis of metallic materials, and in particular to a method for characterizing strain distribution on a metal surface. Background Technology

[0002] The stress-strain relationship directly affects the mechanical properties of metallic materials, and understanding the strain distribution can better guide the control of the material's microstructure. However, current analytical methods for characterizing the true strain distribution of materials are relatively lacking and difficult to achieve a clear and intuitive understanding. Therefore, developing novel methods for characterizing the internal strain distribution of metals is of great importance for improving the mechanical properties of metallic materials. Summary of the Invention

[0003] The purpose of this invention is to provide a method for characterizing strain distribution on metal surfaces, which solves or partially solves the problem that it is difficult to intuitively reflect the true strain distribution on the surface of metal materials at a macroscopic level. By using photolithography to etch a square grid on a metal substrate, the strain distribution during material deformation is intuitively reflected, facilitating the study of strain distribution in experiments. This provides a novel characterization method for guiding the understanding of microscopic deformation mechanisms and developing high-performance metal materials.

[0004] The technical solution of this invention is:

[0005] A method for characterizing strain distribution on a metal surface includes the following steps:

[0006] (1) Before the metal substrate is deformed, a square grid is etched on the surface of the metal substrate using photolithography. The side length of each square grid is 5 to 40 μm.

[0007] (2) An electron beam evaporation system was used to deposit a Ni layer with a thickness of 60-80 nm on the surface of the metal substrate containing the square grid;

[0008] (3) Peel the Ni layer outside the square grid from the metal substrate, leaving a square grid composed of Ni on the surface of the metal substrate;

[0009] (4) After the metal substrate is deformed, the degree of deformation of the square grid is observed by laser scanning confocal microscope to reflect the true strain of the local area on the metal surface.

[0010] The method for characterizing strain distribution on metal surfaces uses an ABM / 6 / 350 / NUV / DCCD / M mask lithography machine and an ULVAC ei-5e-Beam electron beam evaporation system.

[0011] In the metal surface strain distribution characterization method, in step (1), when the square grid is etched by photolithography, the side length of each square grid is preferably 10 to 20 μm.

[0012] In the metal surface strain distribution characterization method, step (2) involves depositing a Ni layer using an electron beam evaporation system to visualize the photolithographic square grid, facilitating intuitive observation of the subsequent strain distribution.

[0013] In the metal surface strain distribution characterization method, in step (4), the displacement of the cross intersection of the square grid is linearly positively correlated with the actual strain. That is, the greater the displacement of the cross intersection in a certain direction, the greater the actual strain in that direction.

[0014] The design concept of this invention is:

[0015] This invention utilizes the idea of ​​transforming the strain distribution, which is difficult to visualize, into the macroscopic deformation degree of a square grid. Under external force, metallic materials undergo elastic deformation, plastic deformation, and fracture. During plastic deformation, dislocation multiplication and slip occur within and on the surface of the material, generating a strain field on the surface. By etching a square grid using photolithography, the grid shape changes after external force is applied, thus reflecting the true strain magnitude in localized areas of the metal surface.

[0016] The advantages and beneficial effects of this invention are:

[0017] 1. This invention provides a method for characterizing the strain distribution on a material surface. By etching a square grid using photolithography, the strain field on the metal surface can be visualized, thereby guiding the control of the material's microstructure and achieving optimized design of its mechanical properties.

[0018] 2. This invention is applicable to strain testing in various mechanical testing situations, providing new ideas and approaches for characterizing material strain distribution. Attached Figure Description

[0019] Figure 1 This is a diagram of the photolithography etching process for the mesh. Among them, (a) shows the cut plate-shaped tensile specimen; (b) shows the photolithographically etched square mesh; and (c) shows the mesh changes observed by CLSM after stretching.

[0020] Figure 2 To observe the damage morphology evolution of plate tensile specimens during tensile deformation using CLSM. Among them, (a) is the surface mesh morphology of the plate tensile specimen when the displacement (D) of the tensile machine chuck is 0.8 mm; (b) is the surface mesh morphology of the plate tensile specimen when D is 2.5 mm; (c) is the surface mesh morphology of the plate tensile specimen when D is 5 mm.

[0021] Figure 3 The strain results of the core and surface of the gradient grain structure TWIP steel plate tensile specimens measured by the present invention are shown in the examples. Detailed Implementation

[0022] In practical implementation, this invention provides a method for characterizing strain distribution on a metal surface. For example... Figure 1 As shown, the method includes the following steps: (1) Before the metal substrate is deformed, a square grid is etched on the surface of the metal substrate by coating photoresist with standard photolithography process, with a grid side length of 5 to 40 μm; (2) Ni layer with a thickness of 60 to 80 nm is deposited on the surface of the metal substrate where the square grid is located by electron beam evaporation system; (3) Ni layer outside the square grid is stripped from the metal substrate, leaving a square grid composed of Ni on the surface of the metal substrate; (4) The metal substrate is loaded and measured. After the metal substrate is stretched and deformed, the degree of deformation of the square grid is observed by laser scanning confocal microscope (CLSM) to reflect the true strain of the local area on the surface of the metal substrate.

[0023] The technical solution of the present invention will now be described and explained in detail with reference to the accompanying drawings.

[0024] Example

[0025] This embodiment provides a method for characterizing the strain distribution on the surface of metallic materials, the specific process of which is as follows:

[0026] (1) Select a typical TWIP steel as the base material. Its chemical composition by mass percentage is: Mn 18%, C 0.6%, and the remainder is Fe.

[0027] (2) A plate-shaped tensile specimen was cut from the gradient grain structure TWIP steel base material. Before the specimen was stretched, a standard photolithography process was used. ABM / 6 / 350 / NUV / DCCD / M mask photolithography machine from ABM Corporation of the United States was used to coat the surface of the plate-shaped tensile specimen with photoresist and etch a square grid with a side length of 20μm for each square grid.

[0028] (3) A Ni layer with a thickness of 70 nm was deposited on the surface of the plate-shaped tensile specimen containing the square grid using the ULVAC ei-5z e-Beam electron beam evaporation system of ULVAC Corporation of Japan.

[0029] (4) Peel the Ni layer outside the square grid from the plate tensile specimen, leaving a square grid composed of Ni on the surface of the plate tensile specimen, see... Figure 1 ;

[0030] (5) Figure 2 As shown, when the displacement (D) of the tensioning machine chuck is 0.8 mm, 2.5 mm, and 5 mm, the evolution of the square grid and the surface damage morphology of the plate tensile specimen during the deformation process is observed. After the plate tensile specimen is deformed, the degree of deformation of the square grid is observed by CLSM technology to reflect the true strain magnitude.

[0031] (6) By measuring the degree of mesh deformation in different observation areas, the strain of the plate tensile specimen at different locations and in different directions can be obtained. For example Figure 3 As shown, this invention can measure the axial and radial strains of the core and surface layers of a gradient grain structure TWIP steel plate tensile specimen during tensile testing.

[0032] The results of the examples show that the present invention provides a way to characterize the strain distribution of materials, which is applicable to TWIP steel, as well as other metals and alloy systems.

[0033] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for characterizing strain distribution on a metal surface, characterized in that, Includes the following steps: (1) Before the metal substrate is deformed, a square grid is etched on the surface of the metal substrate using photolithography. The side length of each square grid is 5 to 40 μm. (2) An electron beam evaporation system was used to deposit a Ni layer with a thickness of 60-80 nm on the surface of the metal substrate containing the square grid; (3) Peel the Ni layer outside the square grid from the metal substrate, leaving a square grid composed of Ni on the surface of the metal substrate; (4) After the metal substrate is deformed, the degree of deformation of the square grid is observed by laser scanning confocal microscope to reflect the true strain of the local area on the metal surface.

2. The method for characterizing strain distribution on a metal surface according to claim 1, characterized in that, Photolithography machines include, but are not limited to, ABM / 6 / 350 / NUV / DCCD / M mask photolithography machines, and electron beam evaporation systems include, but are not limited to, ULVAC ei-5e-Beam electron beam evaporation systems.

3. The method for characterizing strain distribution on a metal surface according to claim 1, characterized in that, In step (1), when etching the square grid using photolithography, the side length of each square grid is preferably 10 to 20 μm.

4. The method for characterizing strain distribution on a metal surface according to claim 1, characterized in that, In step (2), an electron beam evaporation system is used to deposit a Ni layer, making the photolithographic square grid visible and facilitating the intuitive observation of the subsequent strain distribution.

5. The method for characterizing strain distribution on a metal surface according to any one of claims 1 to 4, characterized in that, In step (4), the displacement of the cross intersection of the square grid is linearly positively correlated with the actual strain. That is, the greater the displacement of the cross intersection in a certain direction, the greater the actual strain in that direction.

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