In-situ testing method for microstructure evolution of metal 3D printing sample

Abstract

The present application relates to a kind of in-situ testing methods of metal 3D printing sample microstructure evolution, comprising: cutting two test samples from the sample to be tested;Two test samples are respectively processed into tensile specimen and embedded clamp;The tensile specimen and embedded clamp are placed in the corresponding position of in-situ mechanical testing equipment, and tensile test is carried out;The change of the microstructure of the tensile specimen in the tensile process and the creep process is observed.In the present application, the tensile specimen and embedded clamp are prepared from the sample to be tested, and the tensile specimen is clamped by the embedded clamp due to the small size of the tensile specimen, which can ensure the clamping stability and constraint reliability of the tensile specimen, avoid the clamping of the standard clamp on the tensile specimen, and avoid the clamping of the standard clamp on the tensile specimen, and avoid the clamping of the standard clamp on the tensile specimen, and avoid the clamping of the standard clamp on the tensile specimen, and avoid the clamping of the standard clamp on the tensile specimen, and avoid the clamping of the standard clamp on the tensile specimen, and avoid the clamping of the standard clamp on the tensile specimen, and avoid the clamping of the standard clamp on the tensile specimen, and avoid the clamping of the standard clamp on the tensile specimen, and avoid the clamping of the standard clamp on the tensile specimen, and avoid the clamping of the standard clamp on the tensile specimen, and avoid the clamping of the standard clamp on the tensile specimen, and avoid the clamping of the standard clamp on the tensile specimen, and avoid the clamping of the standard clamp on the tensile specimen, and avoid the clamping of the standard clamp on the tensile specimen, and avoid the clamping of the standard clamp on the tensile specimen, and avoid the clamping of the standard clamp on the tensile specimen, and avoid the clamping of the standard clamp on the tensile specimen, and avoid the clamping of the standard clamp on the tensile specimen, and avoid the clamping of the standard clamp on the tensile specimen, and avoid the clamping of the standard clamp on the tensile specimen, and avoid the clamping of the standard clamp on the tensile specimen, and avoid the clamping of the standard clamp on the tensile specimen, and avoid the clamping of the standard clamp on the tensile specimen, and avoid the

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of additive manufacturing, and particularly relates to an in-situ testing method for microstructure evolution of a metal 3D printing sample. BACKGROUND

[0002] Selective laser melting (SLM) is an important development direction of metal 3D printing technology, but due to the characteristics of the SLM process, it is still difficult to manufacture a sample with 100% density in the actual printing process. Under the condition of long time and high temperature load, the microstructure of the SLM sample will produce creep damage and creep cracks. Creep deformation is closely related to temperature, and when the temperature T is greater than or equal to 0.3-0.5Tm (Tm is the melting point, unit: K), the creep deformation is more significant. At present, due to the lack of in-situ creep experiments at the microscale, the grain boundary dynamics, dislocation dynamics and micro-damage mechanism of the SLM sample during high-temperature creep are still unclear. SUMMARY

[0003] The present application relates to an in-situ testing method for microstructure evolution of a metal 3D printing sample, which can at least solve some defects of the prior art.

[0004] The present application relates to an in-situ testing method for microstructure evolution of a metal 3D printing sample, which can at least solve some defects of the prior art.

[0005] S1, cutting two test samples from a sample to be tested;

[0006] S2, machining the two test samples into a tensile sample and an embedded clamp, respectively;

[0007] S3, placing the tensile sample and the embedded clamp at corresponding positions of an in-situ mechanical testing device to perform a tensile test;

[0008] S4, observing the change of the microstructure of the tensile sample during the tensile process and the creep process. As one of the embodiments, the in-situ mechanical testing device is an in-situ TEM testing device, wherein the tensile sample and the embedded clamp are respectively arranged at two ends of an in-situ mechanical measuring rod.

[0009] As one of the embodiments, S2 includes:

[0010] S21, preparing the two test samples into needle-shaped samples, respectively;

[0011] S22, performing patterned etching processing on the two needle-shaped samples, respectively, to obtain the tensile sample and the embedded clamp.

[0012] As one of the embodiments, S21 specifically includes:

[0013] removing the cutting deformation layer of the test sample;

[0014] The test sample is prepared into a needle-shaped sample by step-by-step etching processing.

[0015] As one of the embodiments, the cutting deformation layer is removed by electrolytic polishing, wherein an acid electrolyte is used.

[0016] As one of the embodiments, the two needle-shaped samples are subjected to patterned etching processing by using a focused ion beam.

[0017] As one of the embodiments, the ion source of the focused ion beam is gallium ions, and in the step of patterned etching processing, the ion beam energy is 20-40 keV, the beam current density is 3-5 A / cm 2 , and the etching speed is 0.1-5 μm / h.

[0018] As one of the embodiments, the tensile sample comprises a sample body, one end of the sample body is enlarged to form a bell head, and the inner embedding clamp is matched to have a clamping cavity for accommodating the bell head and a giving passage for the sample body to pass through.

[0019] As one of the embodiments, multiple tensile experiments are performed, and the microstructure change of the tensile sample in each tensile experiment is observed.

[0020] In each tensile experiment, the tensile sample is heated to a set temperature, kept for a period of time, and then kept for a set time under a set stress.

[0021] As one of the embodiments, the test sample is a sheet-shaped metal thin sample.

[0022] The present application has at least the following beneficial effects:

[0023] In the present application, the tensile sample and the inner embedding clamp are prepared from the test sample, and since the tensile sample is small in size, the tensile sample is clamped by the inner embedding clamp, so that the clamping stability and the constraint reliability of the tensile sample can be ensured, and the problems of unfirm clamping, force holding, deformation and even torsional fracture of the tensile sample caused by clamping the tensile sample by a standard clamp can be avoided, so that the in-situ test of the microstructure evolution of the metal 3D printing sample can be facilitated, and the accuracy of the test result can be improved. BRIEF DESCRIPTION OF DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the drawings needed in the following embodiment or prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0025] Figure 1 A flowchart of an in-situ testing method provided by an embodiment of the present application is shown in FIG. 1.

[0026] Figure 2 A schematic diagram of the cooperation of a tensile specimen and an embedded specimen is shown in FIG. 2.

[0027] Figure 3 A structural image of the tensile specimen and the embedded specimen is shown in FIG. 3.

[0028] Figure 4 A structural image of the needle-shaped specimen is shown in FIG. 4. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0030] As Figure 1 , the present application provides an in-situ testing method for the microstructure evolution of a metal 3D printing specimen, which comprises the following steps:

[0031] S1. cutting two test specimens from a specimen to be tested;

[0032] S2. processing the two test specimens into a tensile specimen 1 and an embedded clamp 2, respectively;

[0033] S3. placing the tensile specimen 1 and the embedded clamp 2 at corresponding positions of an in-situ mechanical testing device to perform a tensile experiment;

[0034] S4. observing the changes in the microstructure of the tensile specimen 1 during the tensile process and the creep process.

[0035] In one of the embodiments, the specimen to be tested is an SLM specimen, i.e., a 3D printing specimen made based on an SLM process.

[0036] Optionally, a diamond wire saw or other equipment is used to cut the test specimens from the specimen to be tested.

[0037] The test specimen includes but is not limited to a sheet-shaped metal thin specimen. Optionally, the length of the test specimen is in the range of 10-40 mm, the width of the test specimen is in the range of 0.3-1 mm, and the thickness of the test specimen is in the range of 0.3-1 mm; in one specific embodiment, the size of the test specimen is 20 mm x 0.5 mm x 0.5 mm.

[0038] In one of the embodiments, the in-situ mechanical testing device is an in-situ TEM (Transmission Electron Microscope) testing device, which can reliably and accurately observe the microstructure evolution process of the 3D printed sample to understand the grain boundary dynamics, dislocation dynamics and micro-damage mechanism of the 3D printed sample.

[0039] In the in-situ mechanical testing device, the tensile sample 1 and the embedded clamp 2 are respectively arranged at two ends of an in-situ mechanical testing rod.

[0040] In one of the embodiments, S2 comprises:

[0041] S21, two test samples are respectively prepared into needle-shaped samples 100;

[0042] S22, the two needle-shaped samples 100 are respectively subjected to graphic etching processing to obtain the tensile sample 1 and the embedded clamp 2.

[0043] Preferably, S21 specifically comprises:

[0044] The cutting deformation layer of the test sample is removed;

[0045] The test sample is prepared into a needle-shaped sample 100 through step-by-step etching processing.

[0046] In one of the embodiments, the preparation process of the above needle-shaped sample 100 specifically comprises:

[0047] ① Rough cutting and positioning: a larger FIB beam is selected, and the general outline of the needle-shaped sample 100 to be processed is separated from the test sample through a specific pattern or direct cutting, and the position and orientation of the cone are determined; wherein the depth and range of cutting are controlled to avoid excessive cutting leading to sample damage or loss of the interested area;

[0048] ② Making a cone rough blank: the basic shape of the cone is gradually etched out by the ion beam to form a relatively rough cone blank; wherein the shape of the cone rough blank can be first drawn in the CAD software, and then the CAD file is imported into the control software of the FIB to etch according to the designed shape; during etching, the beam current and scanning speed of the ion beam are controlled to ensure the size and shape accuracy of the cone rough blank;

[0049] ③ Finishing the cone shape: a smaller ion beam current is used to further shape and polish the surface of the cone rough blank to make the size, shape and surface quality of the cone meet the requirements; during the finishing process, the beam current can be gradually reduced to avoid increasing the surface roughness of the sample or causing defects due to too high beam intensity.

[0050] For example, Figure 4As shown, a needle-shaped sample 100 is prepared.

[0051] In the above method, the needle-shaped sample 100 is prepared: ① to help reduce imaging interference caused by uneven thickness when the electron beam penetrates the sample; ② the conical shape helps better adjust the position and angle of the sample in a limited space, so that the electron beam can accurately penetrate the region of interest of the sample, facilitating the preparation of the stretched sample 1 and the embedded clamp 2.

[0052] The cutting deformation layer is formed during the process of cutting the test sample from the test sample in S1. By removing the cutting deformation layer, the accuracy of the in-situ test result can be ensured. The cutting deformation layer can be removed by electrolytic polishing, preferably using an acidic electrolyte, including but not limited to using a phosphoric acid electrolyte, and the concentration is preferably controlled within the range of 0.8-2 mol / L (for example, controlled at about 1 mol / L).

[0053] Preferably, in S22, the two needle-shaped samples 100 are patterned and etched using a focused ion beam. Preferably, the ion source of the focused ion beam is gallium ions, and further preferably, gallium ions under high voltage of 20-40 kV (preferably controlled at about 30 kV). Preferably, in the patterned etching step, the ion beam energy is 20-40 keV, the beam current density is 3-5 A / cm 2 , and the etching speed is 0.1 μm / h-5 μm / h.

[0054] In one embodiment, multiple stretching experiments are performed to observe the microstructure changes of the stretched sample 1 in each stretching experiment. During each stretching experiment, the stretched sample 1 is heated to a set temperature, held for a period of time, and then held for a set time under a set stress. In this way, observing the microstructure changes of the stretched sample 1 at different set temperatures can more accurately grasp the microstructure evolution mechanism of the metal 3D printed sample.

[0055] In one embodiment, in multiple stretching experiments, the set temperature to which the stretched sample 1 is heated is 400℃, 600℃, 800℃, 1000℃ and 1200℃, respectively; and the holding time can be 20 min, 30 min, 40 min, etc.

[0056] As Figure 2 and Figure 3 In one embodiment, the stretched sample 1 includes a sample body 11, one end of which is enlarged to form a bell head 12, and the embedded clamp 2 has a clamping cavity 21 that matches the bell head 12 and a give way passage 22 for the sample body 11 to pass through.

[0057] By matching the bell head 12 with the clamping cavity 21, the bell head 12 can be reliably clamped as a stretching head by the embedded clamp 2, ensuring the accuracy and reliability of the in-situ test results.

[0058] In which, the size of the accommodation channel 22 and the size of the sample body 11 are best to form a clearance fit relationship between them, for example: the sample body 11 is square rod-shaped, and the width of the accommodation channel 22 is slightly larger than the thickness of the sample body 11 in the thickness direction; or the sample body 11 is cylindrical, and the width of the accommodation channel 22 is slightly larger than the diameter of the sample body 11. Based on the above design, the embedded clamp 2 has better constraint on the tensile sample 1, and the accuracy of the test results is improved.

[0059] Optionally, as Figure 2 and Figure 3 , the bell head 12 includes a gradually expanding section 121 and a constant cross-section section 122, the gradually expanding section 121 is connected to the sample body 11 and the constant cross-section section 122 respectively and gradually expands from the sample body 11 to the constant cross-section section 122; the clamping cavity 21 can correspondingly include a gradually expanding area and a constant cross-section area, the gradually expanding area is connected to the accommodation channel 22 and the constant cross-section area respectively and gradually expands from the accommodation channel 22 to the constant cross-section area, and the gradient slope of the gradually expanding area matches the gradient slope of the gradually expanding section 121, so that the outer wall of the gradually expanding section 121 can be attached to the inner wall surface of the gradually expanding area.

[0060] The bell head 12 is defined as the first end of the tensile sample 1, and the second end of the tensile sample 1 needs to be clamped to facilitate the application of load through the second end of the tensile sample 1 and the embedded clamp 2 respectively. As Figure 2 and Figure 3 , the second end is enlarged relative to the sample body 11, including but not limited to making the tensile sample 1 dumbbell-shaped; the size of the second end can be larger than the bell head 12, so that it can be clamped by the standard clamp of the in-situ mechanical testing equipment, and the tensile sample 1 can correspondingly be asymmetric dumbbell-shaped.

[0061] It can be understood that the above-mentioned embedded clamp 2 can be clamped by the standard clamp of the in-situ mechanical testing equipment.

[0062] In this embodiment, the tensile sample 1 is designed to be dumbbell-shaped, which has at least the following advantages:

[0063] ①During the stretching process, the stress of the middle part of the dumbbell-shaped sample can be several times or even dozens of times higher than that of other parts, and this clear stress concentration area facilitates the accurate observation of the microstructure changes of the material under high stress, such as the movement and proliferation of dislocations;

[0064] ②The geometry of the dumbbell-shaped sample conforms to the basic assumptions of many material mechanics theoretical models, which can improve the accuracy of the test results;

[0065] ③The tensile sample 1 can be conveniently fixed in situ on the TEM tensile device; during the tensile process, the tensile sample 1 can maintain a relatively stable position, and the observation error caused by the shaking or position deviation of the sample is reduced.

[0066] The above merely describes the preferred embodiments of the present application and is not used to limit the present application, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for in-situ testing of microstructure evolution of a metal 3D printed specimen, the method comprising: The in-situ testing method comprises: ​ S1, cutting two test samples from a sample to be tested; S2, processing the two test samples into a tensile sample and an embedded clamp, specifically comprising: S21, preparing the two test samples into needle-shaped samples; S22, performing patterned etching processing on the two needle-shaped samples respectively to obtain the tensile sample and the embedded clamp; The tensile sample comprises a sample body, one end of the sample body is enlarged to form a bell head, and the embedded clamp has a clamping cavity matching the bell head and a displacement passage for the sample body to pass through; S3, placing the tensile sample and the embedded clamp at corresponding positions of an in-situ mechanical testing device to perform a tensile experiment; S4, observing the change of the microstructure of the tensile sample in the tensile process and the creep process.

2. The in-situ testing method for microstructure evolution of a metal 3D printing sample according to claim 1, wherein: The in-situ mechanical testing device is an in-situ TEM testing device, wherein the tensile sample and the embedded clamp are arranged at two ends of an in-situ mechanical testing rod respectively.

3. The method for in-situ testing of microstructural evolution of metal 3D printed specimens of claim 1, wherein, S21 specifically comprises: Removing the cutting deformation layer of the test sample; Preparation of the test sample into a needle-shaped sample by step-by-step etching processing.

4. The in-situ testing method for microstructure evolution of a metal 3D printing sample according to claim 3, wherein: The cutting deformation layer is removed by electrolytic polishing, wherein an acidic electrolyte is used.

5. The in-situ testing method for microstructure evolution of a metal 3D printing sample according to claim 1, wherein: Focusing ion beam is used for patterned etching processing of the two needle-shaped samples.

6. The in-situ testing method for microstructure evolution of a metal 3D printing sample according to claim 5, wherein: The ion source of the focusing ion beam is gallium ions, and in the patterned etching processing step, the ion beam energy is 20-40 keV, the beam current density is 3-5 A / cm2, and the etching speed is 0.1-5 μm / h.

7. The in-situ testing method for microstructure evolution of a metal 3D printing sample according to claim 1, wherein: Multiple tensile experiments are performed to observe the microstructure change of the tensile sample in each tensile experiment; In each tensile experiment, the tensile sample is heated to a set temperature, kept for a period of time, and kept for a set time under a set stress.

8. The method for in-situ testing of microstructural evolution of metal 3D printed specimens of claim 1, wherein: The test sample is a sheet-shaped metal thin sample.

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