In-situ characterization method for metal crystal cutting process

Abstract

The invention discloses an in-situ characterization method for a metal crystal cutting process, which belongs to the field of ultra-precision machining and comprises the following steps: S1, preparing a diamond cutter: preparing a diamond micron slice, cutting a rear cutter surface and a front cutter surface by using current, and polishing the diamond cutter; s2, preparing a workpiece sample: selecting an atomic force microscope probe, preparing a rectangular micron slice by using a focused ion beam micro-nano processing technology, processing a plurality of rectangular slices on the rectangular micron slice by using a focused ion beam, and purging the rectangular slices by using the focused ion beam to complete preparation of the workpiece sample; and S3, cutting experiment: installing the diamond cutter and the workpiece sample on an X-Nano sample rod, cutting the workpiece sample by the diamond cutter, and shooting a bright field image, a dark field image and an electron diffraction pattern of the to-be-detected area by using a transmission electron microscope. According to the invention, the bottleneck that the plastic deformation and fracture behavior of the material in the turning process cannot be dynamically observed in the prior art is broken through.

Description

Technical Field

[0001] The present invention relates to the technical field of ultra-precision machining, and in particular to an in-situ characterization method for a metal crystal cutting process. Background Art

[0002] Turning is a common machining method that is widely used in the dimensional processing of metal materials. It is characterized by high efficiency and strong forming ability. However, due to the higher requirements of the high-end manufacturing field for machining surface quality, geometric accuracy and material microstructure control, traditional turning technology has gradually shown its limitations in these aspects. In order to achieve submicron or even nanometer surface quality, ultra-precision turning technology has come into being. At this characteristic scale, the deformation and fracture of the material will show completely different behaviors from those of the macroscopic scale material. Therefore, the basic theoretical system such as the tool wear law, the workpiece deformation and removal mechanism, and the non-steady-state evolution law of the machining interface needs to be re-established.

[0003] In recent years, with the development of in situ transmission electron microscopy (TEM) experiments, researchers have attempted to dynamically observe the plastic deformation and fracture behavior of materials at the nanoscale. However, achieving this goal requires the development of a micro-cutting system capable of atomic-scale cutting within the TEM chamber. Based on the X-Nano multi-degree-of-freedom in situ transmission electron microscope (TEM) sample holder with sub-nanometer displacement control precision, it is possible to develop a dedicated diamond tool, workpiece sample, and application method that is compatible with it and capable of in situ cutting and deformation characterization in the TEM. This not only helps to reveal the true mechanical behavior of materials at extremely small scales, but also provides new technical means for atomic-scale manufacturing and materials science research.

[0004] Currently, the TEM sample preparation method relies on a focused ion beam (FIB), and the dynamic observation of the plastic deformation and fracture behavior of materials during the turning process remains an insurmountable bottleneck. Summary of the Invention

[0005] The purpose of this invention is to provide an in-situ characterization method for the metal crystal cutting process, using the X-Nano system to achieve in-situ characterization of the tool cutting workpiece, aiming to break through the previous bottleneck of being unable to dynamically observe the plastic deformation and fracture behavior of the material during the turning process.

[0006] To achieve the above object, the present invention provides an in-situ characterization method for a metal crystal cutting process, comprising the following steps: Step S1, preparing a diamond tool: Step S11, using diamond as the base material, using focused ion beam micro-nano processing technology, adopting a method of first digging a hole and then U-shaped cutting to prepare diamond micro-thin slices, and using an easylift needle to extract the diamond micro-thin slices; Step S12: Fixing the half copper mesh and rotating the half copper mesh until the half copper mesh and the diamond micron sheet are perpendicular, attaching the diamond micron sheet to the half copper mesh, processing the surface of the diamond micron sheet into a cube, and using electric current to cut the back cutting edge and the front cutting edge of the cube; Step S13, diamond tool polishing; Step S2, preparing a workpiece sample: Step S21, selecting an atomic force microscope (AFM) probe: selecting a gold wire, making it into a loop-shaped platform with a tail, and using conductive silver paste to stick the AFM probe onto the loop-shaped platform of the gold wire; Step S22, using focused ion beam micro-nano processing technology to prepare rectangular micron slices by first digging a hole and then cutting it into a U shape on the workpiece sample, and using an easylift needle to extract the rectangular micron slices; Step S23, adhering the pre-treated atomic force microscope probe and gold wire assembly to one side of the focused ion beam (FIB) sample holder, flattening the top of the free end of the atomic force microscope probe cantilever, and adhering the rectangular micron sheet to the top of the cantilever; Step S24: a thin area is machined on the top of the rectangular micron slice by using a focused ion beam, and the top of the thin area is cut flat, and a plurality of rectangular slices are machined out of the thin area. A low current is used to cut the top and left and right sides of the rectangular slices. Step S25, using the focused ion beam to sweep the rectangular thin sheet while looking down at the rectangular thin sheet, so as to further reduce the thickness at the top of the rectangular thin sheet, thereby completing the preparation of the workpiece sample; Step S3, cutting experiment: Step S31, fixing the half copper mesh with the diamond tool to the movable end of the X-Nano sample holder, and fixing the atomic force microscope probe with the workpiece sample attached and the gold wire assembly to the external frame of the X-Nano sample holder; Step S32, cutting the workpiece sample using a diamond tool controlled by an X-Nano sample holder under a transmission electron microscope; Step S33 , by moving the transmission electron microscope goniometer stage to keep the cutting area at the center of the image, and using the transmission electron microscope to capture the bright field image, dark field image, and electron diffraction pattern of the area to be measured.

[0007] Preferably, in step S12, a plurality of diamond micron sheets are placed on the top of the same half-copper mesh teeth, and the diamond micron sheets are placed on the half-copper mesh teeth for placing samples. A portion of the irradiated layer on the surface of the diamond micron sheet is removed and trimmed, and a cube is processed on the top of the diamond micron sheet. The cube serves as the base of the diamond tool, and a low current is used to bevel the back cutting surface on the top of the cube, and the front cutting surface is trimmed at the cutting edge, and the wedge angle and back angle of the diamond tool are adjusted.

[0008] Preferably, in step S13, the prepared diamond tool is polished using an ion milling apparatus to remove the radiation damaged layer and the amorphous layer on the surface.

[0009] Preferably, in step S21, the free end of the cantilever beam of the atomic force microscope probe faces the tail of the gold wire, and the atomic force microscope probe is perpendicular to the tail of the gold wire.

[0010] Preferably, in step S23, the cantilever beam of the atomic force microscope probe is vertically upward, and when the rectangular micron sheet is attached, the atomic force microscope probe is rotated to be perpendicular to the rectangular micron sheet.

[0011] Preferably, in step S31, the free end of the cantilever beam of the atomic force microscope probe faces the diamond tool on the half copper mesh, and the axial direction of the cantilever beam at the tip of the atomic force microscope probe is perpendicular to the cutting direction of the diamond tool.

[0012] Preferably, in step S32, displacement control is performed by the X-Nano sample rod to adjust the relative position and height between the diamond tool and the workpiece sample so that the diamond tool is highly aligned with the workpiece sample. The contact between the diamond tool and the workpiece sample slice occurs on one side of the workpiece sample. The X-Nano control program is used to control the diamond tool to move along the X-axis to achieve cutting of the workpiece sample by the diamond tool.

[0013] Therefore, the present invention adopts the above-mentioned in-situ characterization method of the metal crystal cutting process, which has the following beneficial effects: The present invention provides a method for preparing TEM samples and workpiece samples with sharp cutting edges using FIB, as well as a means for in-situ characterization of tool-cut workpieces using an X-Nano system. This aims to overcome the previous bottleneck of being unable to dynamically observe the plastic deformation and fracture behavior of materials during turning.

[0014] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 A flowchart of an embodiment of an in-situ characterization method for a metal crystal cutting process according to the present invention; Figure 2 A side view of a diamond tool with a wedge angle of 75 degrees prepared by a focused ion beam according to an embodiment of the present invention; Figure 3 An oblique side view of a diamond tool with a wedge angle of 75 degrees prepared by a focused ion beam according to an embodiment of the present invention; Figure 4 A side view of a diamond tool with a wedge angle of 60 degrees prepared by a focused ion beam according to an embodiment of the present invention; Figure 5 An oblique side view of a diamond tool with a wedge angle of 60 degrees prepared by a focused ion beam according to an embodiment of the present invention; Figure 6 A side view of a diamond tool with a wedge angle of 45 degrees prepared by a focused ion beam according to an embodiment of the present invention; Figure 7 An oblique side view of a diamond tool with a wedge angle of 45 degrees prepared by a focused ion beam according to an embodiment of the present invention; Figure 8 This is a TEM image of a diamond tool according to an embodiment of the present invention; Figure 9 This is a schematic diagram of a workpiece sample bonded to the top of the AFM probe cantilever beam according to an embodiment of the present invention; Figure 10 Schematic diagram of four rectangular thin slices of workpiece samples for cutting obtained by processing according to an embodiment of the present invention.

[0016] Figure 11 Schematic diagram of the relative positions of the diamond tool and the workpiece sample in the TEM according to an embodiment of the present invention; Figure 12 Figure 1 is a diagram of the cutting process of a workpiece sample by a diamond tool according to an embodiment of the present invention, wherein a is a diagram of the workpiece sample at the start time, b is a diagram of the workpiece sample at 8 seconds of cutting time, c is a diagram of the workpiece sample at 14 seconds of cutting time, d is a diagram of the workpiece sample at 39 seconds of cutting time, e is a diagram of the workpiece sample at 63 seconds of cutting time, and f is a diagram of the workpiece sample at 69 seconds of cutting time; Figure 13 This is a bright field image of a workpiece sample during cutting according to an embodiment of the present invention; Figure 14 These are dark field images of the workpiece sample during the cutting process of an embodiment of the present invention, where a is the dark field image of the workpiece sample cutting at the starting moment, b is the dark field image of the workpiece sample cutting when the cutting time is 91s, and c is the dark field image of the workpiece sample cutting when the cutting time is 121s. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical solutions and advantages disclosed in the embodiments of the present invention clearer, the embodiments of the present invention are further described in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the embodiments of the present invention and are not intended to limit the embodiments of the present invention. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application. Examples of the embodiments are shown in the accompanying drawings, where the same or similar numbers throughout represent the same or similar elements or elements with the same or similar functions.

[0018] It should be noted that the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or server that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or are inherent to these processes, methods, products or devices.

[0019] Like reference numerals and letters denote like items in the following drawings, and thus, once an item is defined in one drawing, it does not require further definition or explanation in subsequent drawings.

[0020] In the description of the present invention, it should be noted that the terms "upper", "lower", "inside", "outside", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, or are the orientations or positional relationships in which the inventive product is usually placed when in use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they should not be understood as limiting the present invention.

[0021] In the description of the present invention, it should also be noted that, unless otherwise expressly specified or limited, the terms "disposed," "installed," and "connected" should be understood broadly. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0022] Example like Figure 1 As shown, the in-situ characterization method of a metal crystal cutting process according to the present invention comprises the following steps: Step S1, preparing a diamond tool: In step S11, using diamond as the substrate, focused ion beam micro-nanofabrication technology is used to prepare multiple diamond micron slices with a height of 5 μm, a width of 3 μm, and a thickness of 3 μm, using a pitting followed by a U-shaped cut. The diamond micron slices are extracted using an EasyLift needle. U-shaped cuts are a method of focused ion beam sample preparation.

[0023] Step S12, fix the half-copper mesh, and rotate the half-copper mesh until the half-copper mesh and the diamond micron sheet are perpendicular, and then stick the diamond micron sheet on the half-copper mesh. Multiple diamond micron sheets can be placed on the top of the same half-copper mesh tooth, keeping a spacing of not less than 10μm. The half-copper mesh tooth is the synapse of the half-copper mesh for placing samples, and the sample is placed on its top. Part of the irradiated layer on the surface of the diamond micron sheet is removed and trimmed, and a cube with a height of 2μm, a width of 2μm, and a thickness of 2μm is machined on the top of the diamond micron sheet as the base of the diamond tool. Use a lower current (voltage of 30kV, current of 40pA~24pA) to bevel the back cutting edge on the top of the cube, and trim the front cutting edge at the cutting edge. As Figure 2-Figure 7 As shown, the wedge angle and back angle of the diamond tool can be adjusted according to the actual tool.

[0024] Step S13, using an ion thinning instrument, polishing the prepared diamond tool at a voltage of 0.9kV for about one hour to remove the radiation damage layer and amorphous layer on the surface. Figure 8 shown.

[0025] Step S2, preparing a workpiece sample: In step S21, select an AFM probe (model SD-T10L100). A 0.25mm diameter gold wire is chosen and fabricated into a loop-shaped platform with a tail. Using conductive silver paste, the AFM probe is affixed to the loop-shaped platform. The free end of the cantilever beam should face the tail of the loop-shaped platform, ensuring that the AFM probe is perpendicular to the tail of the wire.

[0026] Step S22: Using focused ion beam micro-nano processing technology, the workpiece sample is first dug and then U-cut to prepare a rectangular micron slice with a height of 5 μm, a width of 20 μm, and a thickness of 2 μm. The rectangular micron slice is extracted using an easylift needle.

[0027] Step S23: Glue the pre-treated AFM probe-gold wire assembly to one side of the FIB sample holder, ensuring that the cantilever of the AFM probe is vertically upward. Rotate the AFM probe to be perpendicular to the rectangular micron sheet. Flatten the top of the free end of the cantilever and glue the rectangular micron sheet to the top of the cantilever, as shown in the following figure: Figure 9 shown.

[0028] Step S24: The voltage of the focused ion beam is 30 kV, and the current is 0.79 nA to 80 pA. A thin area with a height of 1 μm, a width of 20 μm, and a thickness of 0.3 μm is machined on the top of the rectangular micron sheet, and the top is cut flat. Figure 10As shown in the figure, four rectangular slices with a width of 2.5μm were trimmed from the thin area, with a spacing of at least 2μm between them. A lower current (voltage 30kV, current 7.7pA) can be used to cut the top and left and right sides of the rectangular slice to obtain a better test sample shape.

[0029] In step S25, with the focused ion beam looking down at the rectangular slice, a voltage of 5 kV and a current of 15 pA are used to blow the rectangular slice with the focused ion beam to further reduce the thickness at the top, and finally to 150 μm, thereby completing the preparation of the workpiece sample.

[0030] Step S3, cutting experiment steps: Step S31: Mount the workpiece sample on the X-Nano sample holder. The X-Nano sample holder is a conventional structure. A half-copper mesh with a diamond cutter is affixed to the movable end of the X-Nano sample holder. Subsequently, the AFM probe and gold wire assembly, with the workpiece sample attached, is affixed to the outer frame of the X-Nano sample holder, ensuring that the free end of the cantilever beam faces the diamond cutter on the half-copper mesh and that the cantilever axis at the AFM probe tip is perpendicular to the cutting direction of the diamond cutter.

[0031] Step S32, under TEM, as Figure 11 As shown in the figure, the relative position and height between the diamond tool and the sample being cut are precisely adjusted by controlling the displacement of the X-Nano sample holder, so that the tool and the workpiece sample are aligned at the same height and the contact between the diamond tool and the workpiece sample slice occurs on one side of the workpiece sample. Figure 12 As shown, the X-Nano control program is used to precisely control the movement of the diamond tool along the X-axis to achieve cutting of the workpiece sample by the diamond tool.

[0032] Step S33, by moving the TEM goniometer to keep the cutting area in the center of the image, and using TEM to take bright field images, dark field images, electron diffraction patterns, etc. of the area to be measured. Figure 13 As shown in Figure 2, dislocation nucleation and slip phenomena can be observed inside the workpiece sample. Figure 14 As shown, it can be observed that the tool cuts through the grains inside the sample.

[0033] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solutions of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for in-situ characterization of a metal crystal cutting process, characterized in that: The following steps are involved: Step S1, preparing a diamond tool: Step S11, using diamond as the base material, using focused ion beam micro-nano processing technology, adopting a method of first digging a hole and then U-shaped cutting to prepare diamond micro-thin slices, and using an easylift needle to extract the diamond micro-thin slices; Step S12: Fixing the half copper mesh and rotating the half copper mesh until the half copper mesh and the diamond micron sheet are perpendicular, attaching the diamond micron sheet to the half copper mesh, processing the surface of the diamond micron sheet into a cube, and using electric current to cut the back cutting edge and the front cutting edge of the cube; Step S13, diamond tool polishing; Step S2, preparing a workpiece sample: Step S21, selecting an atomic force microscope probe: selecting a gold wire, making it into a loop-shaped platform with a tail, and using conductive silver paste to stick the atomic force microscope probe to the loop-shaped platform of the gold wire; Step S22, using focused ion beam micro-nano processing technology to dig a hole in the workpiece sample and then cut it into a U-shape to prepare a rectangular micron slice, and using an easylift needle to extract the rectangular micron slice; Step S23, adhering the pre-treated atomic force microscope probe and gold wire assembly to one side of the focused ion beam micro-nano cutting sample fixture, flattening the top of the free end of the cantilever of the atomic force microscope probe, and adhering the rectangular micron sheet to the top of the cantilever; Step S24: a thin area is machined on the top of the rectangular micron slice by using a focused ion beam, and the top of the thin area is cut flat, and a plurality of rectangular slices are machined out of the thin area. A low current is used to cut the top and left and right sides of the rectangular slices. Step S25, using the focused ion beam to sweep the rectangular thin sheet while looking down at the rectangular thin sheet, so as to further reduce the thickness at the top of the rectangular thin sheet, thereby completing the preparation of the workpiece sample; Step S3, cutting experiment: Step S31, fixing the half copper mesh with the diamond tool to the movable end of the X-Nano sample holder, and fixing the atomic force microscope probe with the workpiece sample attached and the gold wire assembly to the external frame of the X-Nano sample holder; Step S32, cutting the workpiece sample using a diamond tool controlled by an X-Nano sample holder under a transmission electron microscope; Step S33 , by moving the transmission electron microscope goniometer stage to keep the cutting area at the center of the image, and using the transmission electron microscope to capture the bright field image, dark field image, and electron diffraction pattern of the area to be measured.

2. The in-situ characterization method for a metal crystal cutting process according to claim 1, wherein: In step S12, several diamond micron sheets are placed on the top of the same half-copper mesh. The diamond micron sheets are placed on the half-copper mesh teeth on the half-copper mesh for placing samples. Part of the irradiated layer on the surface of the diamond micron sheet is removed and trimmed. A cube is machined on the top of the diamond micron sheet. The cube serves as the base of the diamond tool. A low current is used to bevel the back cutting edge on the top of the cube, and the front cutting edge is trimmed at the cutting edge. The wedge angle and back angle of the diamond tool are adjusted.

3. The in-situ characterization method for a metal crystal cutting process according to claim 1, wherein: In step S13, the prepared diamond tool is polished using an ion milling apparatus to remove the radiation damaged layer and the amorphous layer on the surface.

4. The in-situ characterization method for a metal crystal cutting process according to claim 1, wherein: In step S21 , the free end of the cantilever beam of the atomic force microscope probe faces the tail of the gold wire, and the atomic force microscope probe is perpendicular to the tail of the gold wire.

5. The in-situ characterization method for a metal crystal cutting process according to claim 1, wherein: In step S23 , the cantilever beam of the atomic force microscope probe is vertically upward, and when the rectangular micron sheet is attached, the atomic force microscope probe is rotated to be perpendicular to the rectangular micron sheet.

6. The in-situ characterization method for a metal crystal cutting process according to claim 1, wherein: In step S31 , the free end of the cantilever beam of the atomic force microscope probe faces the diamond tool on the half copper mesh, and the axial direction of the cantilever beam at the tip of the atomic force microscope probe is perpendicular to the cutting direction of the diamond tool.

7. The in-situ characterization method for a metal crystal cutting process according to claim 1, wherein: In step S32, displacement control is performed through the X-Nano sample rod to adjust the relative position and height between the diamond tool and the workpiece sample so that the diamond tool and the workpiece sample are highly aligned. The contact between the diamond tool and the workpiece sample slice occurs on one side of the workpiece sample. The X-Nano control program is used to control the diamond tool to move along the X-axis to achieve cutting of the workpiece sample by the diamond tool.

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