CN114624080B - Preparation method of transmission electron microscope test sample for section of hot-dip galvanized steel sheet - Google Patents

Abstract

The invention provides a preparation method of a transmission electron microscope test sample of a hot-dip galvanized steel sheet, which specifically comprises the following steps: cutting the hot-dip galvanized ultrahigh-strength steel plate to obtain a test sample which can be placed in a dual-beam system sample observation chamber; selecting a region to be sampled and depositing metal protection by using dual-beam type focused ion beam equipment; digging a pit around a sample to be sampled by using a focused ion beam, taking out the sample by using a nanometer robot, transferring the sample to a metal support, processing three support columns at the metal support at the bottom of the sample, dividing a region to be cut between every two adjacent support columns, and cutting and removing by using the ion beam; and depositing protective metal on the two surfaces of the sample again, and then respectively carrying out ion thinning on the remaining two sample areas. The method provided by the invention can ensure the continuity and integrity of the transmission samples of the section of the hot-dip galvanized steel plate, and can obtain two comparative transmission samples with an ultra-long observation visual range at one time, thereby improving the preparation efficiency and success rate of the transmission samples.

Description

Preparation method of transmission electron microscope test sample for section of hot-dip galvanized steel sheet

Technical Field

The invention relates to the technical field of material electron microscope testing, in particular to a preparation method of a transmission electron microscope testing sample for a hot-dip galvanized steel sheet section.

Background

Hot dip plating is one of means for effectively protecting steel materials, has a long process history, and various hot dip plating techniques are continuously developed along with the development of science and technology. The hot-dip galvanizing technology is a mature industrial technology in the prior steel material protection technology and is widely applied to the fields of buildings, automobiles and the like. At present, because alloy elements such as Mn, si, al and the like are added to ultrahigh-strength steel materials which are used in a large amount in automobile bodies, certain influence is generated on the adhesive force, the uniformity and the corrosion resistance of a zinc coating. Therefore, the analysis of the microstructure and the structural characteristics of the section of the hot-dip galvanized ultrahigh-strength steel has important significance for researching the influence mechanism of alloy elements on the coating, improving the quality of the coating and the like.

The transmission electron microscope characterization technology is an important microstructure analysis and test means in the field of material research, and to obtain a high-quality transmission image, a transmission sample is often subjected to nanometer-scale ultra-fine thinning processing by using a Focused Ion Beam (FIB) device. However, the hardness difference of the materials between the galvanized layer and the ultrahigh-strength steel substrate is large, so that when a hot-dip galvanized ultrahigh-strength steel section sample is directly thinned by using a focused ion beam, the problems of nonuniform material deformation, void defect and the like at the interface are easily caused, the integrity of the sample is damaged to a certain extent, and the quality and the accuracy of a subsequent transmission test result are further influenced.

Disclosure of Invention

In view of the above, the present invention aims to provide a method for preparing a transmission electron microscopy test sample of a cross section of a galvanized steel sheet. The preparation method provided by the invention can ensure the integrity of a thin area at a zinc coating-matrix, realize the continuity of the upper and lower layer structures of the sample to be tested, improve the yield of the sample to be tested, obtain two samples at one time and improve the test efficiency.

The invention provides a preparation method of a transmission electron microscope test sample of a cross section of a hot-dip galvanized steel plate, which comprises the following steps:

s1, cutting a hot-dip galvanized steel plate to obtain an initial cut sample;

s2, placing the initial cutting sample into a sample chamber of a double-beam type focused ion beam device, and selecting and positioning a region to be sampled on the surface of the initial cutting sample in a secondary electron mode; then, depositing a metal protective layer in the area to be sampled in an ion beam mode;

s3, digging pits on the initial cutting sample along two sides of the length direction of the metal protection layer, forming two pit grooves below the metal protection layer, and taking a sample surrounded between the two pit grooves as a sample to be sampled;

s4, carrying out U-shaped cutting on the to-be-sampled part connected below the metal protective layer, specifically, removing one side and the bottom of the to-be-sampled part, and leaving part of the other side for connection; then cutting off the connection of the part to separate the sample to be sampled from the initial cutting sample, and then taking out the sample;

s5, transferring the sample to a metal support, and depositing a metal connecting layer at the joint between the sample and the metal support to weld the sample and the metal support together;

s6, processing the metal support to form three support columns below the metal connecting layer; the three support columns are all connected with the metal connecting layer and are distributed at equal intervals;

s7, carrying out area division and cutting on the sample:

area division:

extending towards the inside of the sample along the standing direction of the three support columns, and forming two extension zones, namely an extension zone 1 and an extension zone 2, in the sample;

dividing the extension area 1 into two areas along the width direction of the sample, wherein a boundary is positioned in a zinc coating layer of the sample or at the junction of the zinc coating layer and a transition layer, the area close to the metal protection layer is marked as a sample 1 area, and the remaining area close to the metal connecting layer is marked as a to-be-cut area 1;

dividing the extension region 2 into two regions along the width direction of the sample, wherein the boundary is positioned in a galvanized layer of the sample, the region close to the metal protection layer is marked as a region 2' to be cut, and the remaining region close to the metal connecting layer is marked as a mixed region 2; extending the area 2' to be cut to the side of the sample end far away from the area of the sample 1 along the length direction of the sample until the area is flush with the side of the sample end, and marking the area as the area 2 to be cut; dividing the mixed area 2 into two areas, wherein a boundary is positioned in a base layer of a sample or at the junction of the base layer and a metal connecting layer, the area below the boundary is marked as an area 3 to be cut, and the rest area is marked as an area of the sample 2;

cutting:

cutting the area to be cut 1, the area to be cut 2 and the area to be cut 3 to form a sample 1 and a sample 2;

s8, depositing a metal protective layer on the upper surface of the sample 2, and then carrying out ion thinning on the sample 1 and the sample 2 to obtain a transmission electron microscope test sample of the hot-dip galvanized steel plate.

Preferably, in step S1, the initial cut sample preferably includes sequentially contacting: a zinc coating, a transition layer, an internal oxidation layer and a base layer.

Preferably, in step S2:

the conditions of the secondary electron mode are: the voltage is 10-30 kV;

the conditions of the ion beam mode are: the voltage is 10-30 kV, and the ion beam current is 0.1-0.3 nA.

Preferably, in the step S2, the metal protection layer is a Pt metal protection layer.

Preferably, in the step S2, the metal protection layer has a length of 23 to 25 μm, a width of 2.5 to 3 μm, and a thickness of 1.5 to 2 μm.

Preferably, in step S4, the method further includes, between the U-line cutting and the cutting: welding a nanometer robot hand and the metal protective layer together;

after the cutting, the nano-robot hand is lifted up, and a sample is extracted.

Preferably, the welding specifically includes: depositing a metal connector between the nanometer robot hand and the metal protective layer by using ion beams to weld the nanometer robot hand and the metal protective layer together;

the metal connector is a Pt metal connector.

Preferably, in the step S3, the length of the excavation is 23 to 25 μm, the width is 12 to 15 μm, and the depth is 12 to 15 μm.

Preferably, in step S6, two support columns located at two ends of the three support columns are respectively flush with end faces at two ends of the metal connecting layer;

the width of the two supporting columns at the two ends is less than that of the middle supporting column.

Preferably, in step S5, the metal connection layer is a Pt metal connection layer;

in the step S7, the width of the zinc coating layer to the width of all the other layers in the sample 2 area is 1: 3.

The invention provides a preparation method of a transmission electron microscope test sample of a hot-dip galvanized steel plate, in particular to a preparation method of an ultra-thin sample containing coatings with different hardness by FIB, which specifically comprises the following steps: cutting the hot-dip galvanized ultrahigh-strength steel plate to obtain a test sample which can be placed in a dual-beam system sample observation chamber; selecting a region to be sampled and depositing metal protection by using dual-beam type focused ion beam equipment; digging a pit around a sample to be sampled by using a focused ion beam, taking out the sample by using a nanometer robot, transferring the sample to a metal support, processing three support columns at the metal support at the bottom of the sample, dividing a region to be cut between every two adjacent support columns, and cutting and removing by using the ion beam; and depositing protective metal on the two surfaces of the sample again, and then respectively carrying out ion thinning on the remaining two sample areas. The invention utilizes a double-beam type focused ion beam system to cut and prepare a hot-dip galvanized ultrahigh-strength steel section transmission sample without adding extra instruments and equipment, and utilizes focused ion beams to divide, cut and remove and respectively reduce ions of a hot-dip galvanized ultrahigh-strength steel section sample area, thereby ensuring the continuity and integrity of the hot-dip galvanized ultrahigh-strength steel section transmission sample and obtaining a complete and continuous hot-dip galvanized ultrahigh-strength steel coating/substrate section transmission sample which cannot be obtained by the traditional means. And the method can obtain ultrathin FIB slices containing dissimilar metals with large hardness difference in a visible area, can obtain two comparative transmission samples with an overlong observation visual distance at one time, and a same support column is shared between the two transmission samples, and meanwhile, the operation flow is simple, so that the efficiency and the success rate of the preparation of the transmission samples of the hot-dip galvanized ultrahigh-strength steel section are improved.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.

FIG. 1 is a perspective view of the initial cut sample obtained in step S1;

FIG. 2 is a cross-sectional view of the initial cut sample obtained in step S1;

FIG. 3 is a schematic diagram of the initial cut sample after a metal protection layer is deposited on the surface thereof in step S2;

FIG. 4 is a schematic diagram of digging a pit on the outer periphery of the metal passivation layer in step S3;

fig. 5 is a schematic diagram illustrating the pit wall inclination angle of the pit in step S3;

FIG. 6 is a schematic diagram of the cut-away area of the U-shaped cutting band and the cut-away area in step S4;

FIG. 7 is a schematic diagram of the connection of the nanomachiner hand to the sample in step S4;

FIG. 8 is a schematic view of the sample taken in step S4;

FIG. 9 is a schematic view of the sample and the metal holder being welded together in step S5;

FIG. 10 is a schematic illustration of the separation of the nanomachinery hand from the sample;

FIG. 11 is a schematic view of a design support post;

FIG. 12 is a schematic view of the support post processed in step S6;

FIG. 13 is a schematic view of the internal extension of the sample in step S7;

FIG. 14 is a schematic diagram of the area division of the sample in step S7;

FIG. 15 is a schematic diagram of the sample after cutting in step S7;

fig. 16 is a schematic diagram illustrating a metal layer deposited on the surface of sample 2 in step S8;

FIG. 17 is a schematic view of the thinned region in step S8;

FIG. 18 is a schematic diagram of the sample thinned in step S8;

FIG. 19 is a schematic view showing the distribution of regions in the final product;

FIG. 20 is an SEM photograph of a sample obtained in example 1.

Detailed Description

The invention provides a preparation method of a transmission electron microscope test sample of a hot-dip galvanized steel sheet, which comprises the following steps:

s1, cutting a hot-dip galvanized steel plate to obtain an initial cut sample;

s2, placing the initial cutting sample into a sample chamber of a double-beam type focused ion beam device, and selecting and positioning a region to be sampled on the surface of the initial cutting sample in a secondary electron mode; then, depositing a metal protective layer on the area to be sampled in an ion beam mode;

s3, digging pits on the initial cutting sample along two sides of the length direction of the metal protection layer, forming two pit grooves below the metal protection layer, and taking a sample surrounded between the two pit grooves as a sample to be sampled;

s4, carrying out U-shaped cutting on the to-be-sampled part connected below the metal protective layer, specifically, removing one side and the bottom of the to-be-sampled part, and leaving part of the other side for connection; then cutting off the connection of the part to separate the sample to be sampled from the initial cutting sample, and then taking out the sample;

s5, transferring the sample to a metal support, and depositing a metal connecting layer at the joint between the sample and the metal support to weld the sample and the metal support together;

s6, processing the metal support to form three support columns below the metal connecting layer; the three supporting columns are all connected with the metal connecting layer and are distributed at equal intervals;

s7, carrying out area division and cutting on the sample:

area division:

extending towards the inside of the sample along the standing direction of the three support columns, and forming two extension zones, namely an extension zone 1 and an extension zone 2, in the sample;

dividing the extension area 1 into two areas along the width direction of the sample, wherein a boundary is positioned in a zinc coating layer of the sample or at the junction of the zinc coating layer and a transition layer, the area close to the metal protection layer is marked as a sample 1 area, and the remaining area close to the metal connecting layer is marked as a to-be-cut area 1;

dividing the extension region 2 into two regions along the width direction of the sample, wherein the boundary is positioned in a galvanized layer of the sample, the region close to the metal protection layer is marked as a region 2' to be cut, and the remaining region close to the metal connecting layer is marked as a mixed region 2; extending the area 2' to be cut to the side of the sample end far away from the area of the sample 1 along the length direction of the sample until the area is flush with the side of the sample end, and marking the area as the area 2 to be cut; dividing the mixed area 2 into two areas, wherein a boundary is positioned in a base layer of a sample or at the junction of the base layer and a metal connecting layer, the area below the boundary is marked as an area 3 to be cut, and the rest area is marked as an area of the sample 2;

cutting:

cutting the area to be cut 1, the area to be cut 2 and the area to be cut 3 to form a sample 1 and a sample 2;

s8, depositing a metal protective layer on the upper surface of the sample 2, and then carrying out ion thinning on the sample 1 and the sample 2 to obtain a transmission electron microscope test sample of the hot-dip galvanized steel plate.

[ with respect to step S1]:

and cutting the hot-dip galvanized steel plate to obtain an initial cut sample.

In the invention, the cutting is preferably linear cutting, and an initial cutting sample with a certain size and capable of being placed in a sample chamber of a double-beam Focused Ion Beam (FIB) device is obtained by linear cutting. The obtained initial cut sample is shown in fig. 1, and fig. 1 is a perspective view of the initial cut sample obtained in step S1. In some embodiments of the invention, the initial cut has a length of 15mm and a width of 15mm.

In the present invention, the initial cut sample preferably comprises sequentially contacting: a zinc coating, a transition layer, an internal oxidation layer and a base layer. Referring to fig. 2, fig. 2 is a cross-sectional view of the initial cut sample obtained in step S1, in which a 1-zinc-plated layer, a 2-transition layer (which may contain reduced iron and an outer oxide layer), a 3-inner oxide layer, and a 4-base layer. The surface of the galvanized layer 1 is generally referred to as the upper surface of the initial cut pattern.

In the present invention, the thickness of the zinc plating layer 1 is about 5 μm, and in FIG. 2, the thickness direction is from the top to the bottom (or from the bottom to the top). In the invention, the hot-dip galvanized steel sheet is a hot-dip galvanized ultrahigh-strength steel sheet, in particular to a hot-dip galvanized steel sheet with the ultimate tensile strength of more than or equal to 780 MPa. In one embodiment of the present invention, the hot-dip galvanized steel sheet is a hot-dip galvanized ultra-high strength steel sheet, and the chemical composition of the base layer 4 is 0.2C-1.8Si-2.6Mn-Fe (wt%).

[ regarding step S2]:

placing the initial cut sample into a sample chamber of a dual-beam type focused ion beam device, and selecting and positioning a region to be sampled on the surface of the initial cut sample in a secondary electron mode; then, a metal protection layer is deposited on the area to be sampled by using an ion beam mode.

In the invention, the initial cutting sample obtained in the step S1 is firstly placed in a sample chamber of a double-beam type focused ion beam device, and a secondary electron mode is adopted to select and position a region to be sampled on the surface of the initial cutting sample. Wherein the surface of the initial cutting sample is the surface of a galvanized layer. The selection of the region to be sampled by the present invention is not particularly limited, and a region of interest such as a defect site, a grain boundary site, or the like may be selected. In the present invention, it is preferable that the area to be sampled is selected and positioned in the secondary electron mode under the electron beam window under the set voltage of 10 to 30 kV.

In the invention, after the position is calibrated, a metal protection layer (marked as a metal protection layer A) is deposited in the area to be sampled in an ion beam mode. Referring to fig. 3, fig. 3 is a schematic diagram of the metal protection layer deposited on the surface of the initial cut sample in step S2, wherein 1 is the initial cut sample, and 2 is the metal protection layer a. Among them, the metal cap layer a is preferably a Pt cap layer. In the present invention, the metal protective layer 1 is preferably rectangular parallelepiped, i.e., long. The length of the metal protection layer A is preferably 23-25 μm, and more preferably 23 μm; the width is preferably 2.5 to 3 mu m; the thickness is preferably 1.5 to 2 μm. In the invention, when the metal protective layer A is deposited in an ion beam mode, under an ion beam window, the conditions are set as follows: the ion beam voltage is preferably 10 to 30kV, more preferably 30kV, and the ion beam current is preferably 0.1 to 0.3nA, more preferably 0.3nA.

The invention deposits a metal protective layer A to protect the area to be sampled, and the sample to be sampled which is dug out later is taken out from the sample area covered by the metal protective layer A.

[ regarding step S3]:

and digging pits on the initial cutting sample along two sides of the length direction of the metal protection layer, forming two pit grooves below the metal protection layer, and taking a sample surrounded between the two pit grooves as a sample to be sampled.

In the invention, the periphery of the metal protective layer A has 4 side surfaces, two side surfaces are arranged along the length direction of the metal protective layer A, and two side surfaces are arranged along the width direction of the metal protective layer A. Referring to fig. 4, fig. 4 is a schematic diagram of digging a pit in the initial cut sample at the periphery of the metal protection layer in step S3, wherein the dotted line part represents two pit grooves at both sides of the metal protection layer a in the length direction, and in fig. 4, the left sample shows the planar rendering effect of the two pit grooves on the surface of the initial cut sample (wherein, the distance between the horizontal arrows represents the length of the pit groove, and the distance between the vertical arrows represents the width of the pit groove); the middle sample shows a three-dimensional penetration effect of two pit grooves penetrating from the surface to the inside of the initial cut sample, and the part of a gray block sample surrounded by the two pit grooves is to be sampled; the right sample shows the profile rendering effect of the pit inside the initial cut sample (where the distance between the vertical arrows represents the depth of the pit). Through the digging, two sides to be sampled (namely two sides corresponding to the length direction of the metal protection layer A) are disconnected with the initial cutting sample.

In the present invention, the excavation is preferably performed by ion beam excavation. In the present invention, the ion beam is controlled to be incident obliquely at an angle with respect to the upper surface of the initially cut sample, rather than from a direction perpendicular to the upper surface of the sample, so that the walls of the dug pit are gradually inclined from the top edge of the pit to the bottom of the pit, i.e., the two pits are not vertical pits, but inclined pits, as shown in the middle sample in fig. 4. In the invention, the pit wall inclination angle alpha of the pit groove can be 45-60 degrees; the inclination angle is an angle of the pit wall deviating from the normal direction of the pit, i.e. an included angle between the pit wall and the normal direction of the pit, as shown in fig. 5, and fig. 5 is a schematic diagram of the inclination angle of the pit wall of the pit in step S3.

The length, width and depth of the pit groove dug by the invention are shown in figure 4, and after digging, the part surrounded by the two pit grooves is the part to be sampled (comprising a sample body to be sampled and a metal protective layer A covering the sample body). In the present invention, it is preferable that both ends of one pit are flush with both ends of the other pit, as shown in fig. 4. In the invention, the length of the pit is preferably equal to or more than that of the metal protective layer A, namely, two ends of the metal protective layer A in the length direction are retracted compared with two ends of the pit in the length direction, or two ends of the pit in the length direction are flush; specifically, the length of the pit is preferably 23 to 25 μm. In the present invention, the width of the pit is preferably 12 to 15 μm. In the present invention, the depth of the pit is preferably 12 to 15 μm.

[ regarding step S4]:

carrying out U-shaped cutting on the to-be-sampled part connected below the metal protective layer, specifically removing one side and the bottom of the to-be-sampled part, and leaving part of the other side connected; the connection is then severed to disconnect the sample from the initial cut and the sample is removed.

In the present invention, in the step S3, the two sides of the periphery of the connection sample under the metal protection layer are dug, and after the digging, the bottom and the remaining two sides (i.e. the two sides corresponding to the width direction of the metal protection layer a) of the sample to be sampled are connected to the initial cut sample. The method comprises the following steps of carrying out U-shaped cutting on a to-be-sampled sample connected below a metal protective layer, specifically removing the remaining side and the bottom of the to-be-sampled sample (specifically removing the connection between the remaining side and an initial cutting sample and removing the connection between the bottom of the to-be-sampled sample and the initial cutting sample to separate the side and the bottom of the to-be-sampled sample from the initial cutting sample), removing a part of the remaining other side (namely removing a part of the connection between the remaining other side and the initial cutting sample and also keeping a part of the connection), and leaving a part of the connection; as shown in fig. 6, fig. 6 is a schematic diagram of the U-shaped cutting zone cut-off region in step S4 and the cut-off sample, wherein the left sample shows the U-shaped cutting region (the dotted line portion represents the portion to be removed), and the right sample shows the effect after the U-shaped cutting; it can be seen that after the U-shaped cut, the side and bottom to be sampled are completely removed, and the other side is mostly removed, leaving only a small portion connected. Then, the connection is cut again (i.e., the other side to be sampled is also disconnected from the initial cut sample), thereby disconnecting the entire sample from the initial cut sample.

Wherein:

the manner of cutting the bottom is not particularly limited, and the cutting may be performed by a conventional cutting method in the art, and preferably by an ion beam cutting method. The cutting means for the side face is not particularly limited, and the cutting means may be any cutting means that is conventional in the art, and preferably ion beam cutting means.

In the present invention, the sizes of the bottom and side cuts are determined according to the length and width to be sampled, which correspond to the depth direction of the pit groove, respectively. In the present invention, the length to be sampled is ≦ the length of the metal protection layer A (i.e., the metal protection layer in step S2), preferably 23 to 25 μm, and in some embodiments of the present invention 23 μm. In the present invention, the width to be sampled (corresponding to the depth of the pit) is preferably 10 to 15 μm, and in some embodiments 12 μm. In the present invention, when the remaining side is cut from the bottom upward, the cutting height is less than the width to be sampled (corresponding to the depth of the pit slot), i.e. after cutting, there is a connection between the top to be sampled and the initially cut sample, which does not allow the sample to be sampled to be completely separated, as shown in fig. 6.

It can be seen that the bottom to be sampled is completely detached from the original sample after the above described cutting off of the bottom and the sides, the sides are mostly detached from the original sample and only slightly connected at the top. At this time, the remaining junction at the top is cut off by the focused ion beam, so that the sample to be sampled is completely disconnected from the initial cut sample.

In the present invention, it is preferable to weld the metal protection layer a to the nanomachiner hand before cutting the remaining connections at the top. Specifically, one end of the nanometer robot hand, which is close to the metal protection layer A, is suspended above the metal protection layer A and is close to and not in contact with the metal protection layer A, and then an ion beam is used for depositing a metal connector between the nanometer robot hand and the metal protection layer A so that the nanometer robot hand and the metal protection layer A are welded together. In the present invention, the metal connector to weld the two together is preferably metal Pt. Referring to fig. 7, fig. 7 is a schematic diagram of the connection between the nanomachine and the sample in step S4, where 1 is the nanomachine and 2 is the metal connector. After the nanometer robot and the metal protection layer A are welded together through the treatment, the residual joint at the top is cut off by utilizing the focused ion beam, so that the sample to be sampled is completely disconnected from the initial cutting sample.

After the above treatment, the nano robot is lifted up to extract the sample, as shown in fig. 8, fig. 8 is a schematic diagram of the sample taken in step S4, wherein the length of the lower bottom edge represents the length to be sampled, and the side edge represents the total width (including the width of the sample body to be sampled and the thickness of the metal protection layer).

[ regarding step S5]:

the sample is transferred to a metal holder and a metal joining layer is deposited at the junction between the sample and the metal holder, so that the sample and the metal holder are welded together.

In the present invention, after the sample is taken out by the nano robot hand in step S4, the nano robot hand is directly operated to transfer the sample to the metal holder, and specifically, the opposite bottom edge (i.e., the other edge opposite thereto) on which the metal protection layer a is deposited is placed on the metal holder. Referring to fig. 9, fig. 9 is a schematic view of the sample and the metal support welded together in step S5, where 1 is the metal support, and 2 is the metal connection layer (for convenience, the metal connection layer is referred to as the metal connection layer B, which is distinguished from the metal protection layer a described above).

In the present invention, the metal stent is preferably a copper stent. In the present invention, the copper scaffold is preferably rectangular parallelepiped or cubic in shape. In the present invention, it is preferable that the length of the metal holder is > the length of the sample, i.e., the sample can be completely put on the metal holder. In the present invention, the side of the metal holder that contacts the sample is referred to as the top of the metal holder, and the opposite side is referred to as the bottom of the metal holder.

In the present invention, the metal connection layer B deposited between the sample and the metal mesh is preferably metal Pt. In the present invention, the length of the metal connecting layer B is preferably the same as the length of the bottom side from which the sample has been taken. In the present invention, the thickness of the metal connection layer B is preferably 1.5 to 2 μm.

In the present invention, after the above treatment, the following treatment is further performed: the nanomachinery hand is separated from the sample. Referring to fig. 10, fig. 10 is a schematic view of the separation of the nanomachinery hand from the sample.

[ regarding step S6]:

processing the metal bracket, and forming three support columns below the metal connecting layer; the three support columns are all connected with the metal connecting layer and are distributed at equal intervals.

In the invention, the size of each supporting column and the distribution of three supporting columns are designed in advance before the metal support is processed. In the invention, three support columns are distributed at equal intervals from one end to the other end of the metal connecting layer B, wherein two support columns at two ends are preferably respectively flush with the end faces at two ends of the metal connecting layer B (namely the outer side surfaces of the end support columns are flush with the end faces of the metal connecting layer B), namely two end support columns and 1 middle support column are provided, specifically, the end support columns are arranged at two ends, and the middle support column is arranged in the middle. Referring to fig. 11, fig. 11 is a schematic diagram of a design support column, wherein the dotted line represents a pre-designed desired target support column. Of the three support columns, the width of the two end support columns is preferably the same, and the width of the middle support column is preferably > the width of the end support columns. Wherein, the width of the supporting columns at the two ends is preferably 2-3 μm, and more preferably 3 μm; the width of the intermediate support pillars is preferably 3 to 4 μm, more preferably 4 μm. In the invention, the three support columns are preferably the same in length, the length of each support column is less than the thickness of the metal support, and the length of each support column is particularly preferably 8-10 μm.

In the invention, the processing mode of processing the metal support to form the support column is preferably ion beam bombardment, specifically, the metal support between the adjacent support columns is bombarded, so that the metal support between the adjacent support columns is removed, thereby forming the support column. Referring to fig. 12, fig. 12 is a schematic view of the support pillars processed in step S6, wherein 1 and 2 are one of the regions bombarded by the ion beam.

[ regarding step S7]:

and (3) carrying out area division and cutting on the sample:

area division: extending towards the inside of the sample along the standing direction of the three support columns, and forming two extension zones, namely an extension zone 1 and an extension zone 2, in the sample; dividing the extension area 1 into two areas along the width direction of the sample, wherein a boundary is positioned in a zinc coating layer of the sample or at the junction of the zinc coating layer and a transition layer, the area close to the metal protection layer is marked as a sample 1 area, and the remaining area close to the metal connecting layer is marked as a to-be-cut area 1; dividing the extension region 2 into two regions along the width direction of the sample, wherein the boundary is positioned in a galvanized layer of the sample, the region close to the metal protection layer is marked as a region 2' to be cut, and the remaining region close to the metal connecting layer is marked as a mixed region 2; extending the region 2' to be cut to the sample end side away from the region of the sample 1 along the length direction of the sample until the region is flush with the sample end side, and marking the obtained region as the region 2 to be cut; the mixed area 2 is divided into two areas, a boundary is positioned in the base layer of the sample or at the junction of the base layer and the metal connecting layer, the area below the boundary is marked as an area 3 to be cut, and the rest area is marked as an area of the sample 2.

In the present invention, the sample (including the sample body and the metal protection layer and the metal connection layer located on the upper and lower surfaces of the sample body) is internally extended (up to the top of the metal protection layer a) along the standing direction of the three support columns, and two extension regions are formed inside the sample, that is, one extension region is formed between the extension lines of every two adjacent support columns, and then two extension regions are formed between the three support columns, which are respectively denoted as extension region 1 and extension region 2. Referring to fig. 13, fig. 13 is a schematic diagram of the internal extension region of the sample in step S7, where a dashed box 1 is an extension region 1 and a dashed box 2 is an extension region 2.

In the present invention, after two extension regions are divided, the extension region 1 is divided into two regions along the width direction of the sample, and the boundary is located in the zinc-plating layer of the sample or at the boundary between the zinc-plating layer and the transition layer, wherein the region near the metal protection layer is denoted as a sample 1 region (i.e., the region above the boundary is the sample 1 region and contains the metal protection layer), and the remaining region near the metal connection layer is denoted as a region to be cut 1 (i.e., the region to be cut 1 below the boundary and contains the metal connection layer), i.e., the region to be cut 1 is located directly below the sample 1 region.

Similarly, the extension region 2 is also divided into two regions along the sample width direction, the boundary is located in the zinc-plated layer of the sample, the region near the metal protective layer is designated as a region to be cut 2 '(i.e., the region to be cut 2' including the metal protective layer is located above the boundary), and the remaining region near the metal connection layer is designated as a mixed 2 region (i.e., the region to be mixed 2 including the metal connection layer is located below the boundary); wherein, along the length direction of the sample, the region 2' to be cut extends to the sample end side far away from the sample 1 region until the region is flush with the sample end side, and the obtained region is marked as the region 2 to be cut; dividing the mixed 2 area into two areas, wherein a boundary is positioned in a base layer of the sample or at the junction of the base layer and the metal connecting layer, an area below the boundary is marked as a to-be-cut area 3, the rest area is marked as a sample 2 area, namely, the to-be-cut area 2 is positioned right above the sample 2 area, and the to-be-cut area 3 is positioned right below the sample 2 area. Referring to fig. 14, fig. 14 is a schematic diagram of dividing the sample into regions in step S7, where 5 dashed boxes represent 5 regions, 1 is a region to be cut 1,2 as a sample 1 region, 3 is a region to be cut 2,4 as a region to be cut 3, 5 is a sample 2 region, and the right-side coordinate is an orientation indicator; the lower bottom edge of the area of sample 1 is shown separated from the top edge of the area to be cut, so as to better represent the two areas, but in the actual dividing, only one dividing line is drawn (i.e. the lower bottom edge and the top edge are combined into a whole), and in the same way, the dividing line of the area to be cut 2-the area of sample 2-the area to be cut 3 is also drawn.

In the present invention, the boundary in the extension region 1 is controlled to be located in the zinc-plating layer of the sample or at the boundary between the zinc-plating layer and the transition layer, i.e., the region of the sample 1 only includes the zinc-plating layer. That is, the width (corresponding to the depth direction of the pit in step S3) of the sample (including the metal cap layer) in the sample 1 region is not more than the total thickness of the zinc coating layer and the metal cap layer in the initial cut sample. In the present invention, it is more preferable that the boundary in the extension region 1 is located within the galvanized layer of the sample, i.e., the width (corresponding to the depth direction of the pit in step S3) of the sample (including the metal cap layer) in the region of the sample 1 is controlled to be < the total thickness of the galvanized layer and the metal cap layer in the initial cut sample, and it is more preferable that it is 6 μm. In the present invention, the length of the sample in the sample 1 region is preferably 8 μm.

In the present invention, the boundary in the control extension region 2 is located within the galvanized layer of the sample, and therefore, the mixed region 2 below the boundary includes a part of the galvanized layer + the transition layer + the internal oxide layer + the base layer + the metal connection layer. The invention also divides the mixed 2 area into two parts, and controls the boundary to be positioned in the basal body layer of the sample or at the junction of the basal body layer and the metal connecting layer, therefore, the sample 2 area above the boundary comprises part of the zinc coating layer, the transition layer, the internal oxidation layer and (part or all) the basal body layer; more preferably, the control boundary is located within the matrix layer of the sample, i.e., the region of sample 2 above the boundary is a small portion of the zinc coating layer + the transition layer + the internal oxide layer + a large portion of the matrix layer. In the present invention, the sample width (corresponding to the depth direction of the pit in step S3) of the control sample 2 region is preferably 6 μm. In the present invention, the length of the sample in the sample 2 region is preferably 8 μm.

In some embodiments of the invention, the dimensions of the area to be cut are as follows: area to be cut 1: length 8 μm, width 5 μm; area to be cut 2: length 11 μm, width 4 μm; area to be cut 3: length 8 μm and width 4 μm.

Cutting: and cutting the area to be cut 1, the area to be cut 2 and the area to be cut 3 to form a sample 1 and a sample 2.

In the present invention, the cutting of the region to be cut is preferably performed by ion beam cutting, and after the ion beam cutting, a sample 1 region and a sample 2 region are mainly left, which are respectively a sample 1 and a sample 2. Referring to fig. 15, fig. 15 is a schematic diagram of the cut sample in step S7, wherein 1 is sample 1,2 is sample 2. Wherein, sample 1 is a pure zinc coating, and sample 2 comprises a part of zinc coating + transition layer + internal oxidation layer + (part or all) of substrate layer, more specifically a small part of zinc coating + transition layer + internal oxidation layer + a large part of substrate layer. In the present invention, it is preferable to control the width of the zinc plating layer to the width of all the remaining layers to be 1: 3 in the sample 2 area, that is, to control the width of the area above the boundary line to the width of the area below the boundary line to be 1: 3 in the sample 2 area.

It can be seen that after 3 areas to be cut are cut off, the remaining 2 samples are conjoined samples, that is, 1 whole sample comprises 2 sample areas at different positions, that is, two observation samples are obtained simultaneously, and different positions and different layers of the initial cut sample can be observed simultaneously. Wherein the two samples each preferably have a length of 7 to 8 μm and a width of 4 to 5 μm.

[ with respect to step S8]:

and depositing a metal protective layer on the upper surface of the sample 2, and then carrying out ion thinning on the sample 1 and the sample 2 to obtain a transmission electron microscope test sample of the hot-dip galvanized steel plate.

In the present invention, the upper surface of the sample 2 refers to the surface of the sample 2 away from the metal support, or the surface exposed after the region 2 to be cut is removed. Referring to fig. 16, a schematic diagram of depositing a metal layer on the surface of sample 2 in step S8 in fig. 16, where 1 is the metal layer deposited on the surface of sample 2, and the metal layer serves as a protective layer (hereinafter referred to as a metal protective layer C) on the surface of sample 2.

In the present invention, the metal protective layer C is preferably metal Pt. In the present invention, the thickness of the metal protective layer C is preferably 1.5 to 2 μm, and more preferably 1.5 μm.

In the present invention, after the above surface deposition, ion thinning was performed on samples 1 and 2. Referring to fig. 17, fig. 17 is a schematic view of the thinned region in step S8, in which the regions enclosed by the dotted lines represent the regions to be thinned, i.e., the regions of sample 1 and sample 2, respectively. Specifically, when the sample 2 is thinned, not only the sample body of the sample 2 but also the metal layer deposited on the surface of the sample 2 is thinned.

In the present invention, the thinning means thinning in the thickness direction, and the direction is as shown in fig. 17. In the present invention, samples 1 and 2 were thinned in this order. In the present invention, the degree of thinning is preferably controlled as follows: reducing the thickness to be less than 100 nm. After thinning, the structure of the sample is shown in fig. 18, and fig. 18 is a schematic diagram of the sample thinned in step S8. In one embodiment of the present invention, sample 1 has a length of 8 μm and a width of 6 μm, and sample 2 has a length of 8 μm and a width of 6 μm, as shown in FIG. 18.

In the present invention, after the above-mentioned thinning treatment, a transmission electron microscope test sample of the galvanized steel sheet is obtained, each region in the cross section of the sample is shown in fig. 19, fig. 19 is a schematic distribution diagram of each region in the final product, wherein, region (1) is a metal protective layer (specifically, a metal Pt layer), (2) is a galvanized layer, (3) is a transition layer + an inter-oxidation layer + a base layer, and the width ratio of region (2) to region (3) in sample 2 is about 1: 3. In the transmission test, the sample assembly with the metal holder and the support column shown in fig. 18 was put into a testing apparatus for testing.

The invention provides a preparation method of a transmission electron microscope test sample of a hot-dip galvanized steel plate, in particular to a preparation method of an ultrathin sample containing coatings with different hardness by FIB, which comprises the following steps: cutting the hot-dip galvanized ultrahigh-strength steel plate to obtain a test sample which can be placed in a dual-beam system sample observation chamber; selecting a region to be sampled and depositing metal protection by using dual-beam type focused ion beam equipment; digging a pit around a sample to be sampled by using a focused ion beam, taking out the sample by using a nanometer robot, transferring the sample to a metal support, processing three support columns at the metal support at the bottom of the sample, dividing a region to be cut between every two adjacent support columns, and cutting and removing by using the ion beam; and depositing protective metal on the two surfaces of the sample again, and then respectively carrying out ion thinning on the remaining two sample areas. The invention utilizes a double-beam type focused ion beam system to cut and prepare a hot-dip galvanized ultrahigh-strength steel section transmission sample without adding extra instruments and equipment, and utilizes focused ion beams to divide, cut and remove and respectively reduce ions of a hot-dip galvanized ultrahigh-strength steel section sample area, thereby ensuring the continuity and integrity of the hot-dip galvanized ultrahigh-strength steel section transmission sample and obtaining a complete and continuous hot-dip galvanized ultrahigh-strength steel coating/substrate section transmission sample which cannot be obtained by the traditional means. And the method can obtain ultrathin FIB slices containing dissimilar metals with large hardness difference in a visible area, can obtain two comparative transmission samples with an overlong observation visual distance at one time, and a same support column is shared between the two transmission samples, and meanwhile, the operation flow is simple, so that the efficiency and the success rate of the preparation of the transmission samples of the hot-dip galvanized ultrahigh-strength steel section are improved.

For a further understanding of the invention, reference will now be made to the preferred embodiments of the invention by way of example, and it is to be understood that the description is intended to further illustrate features and advantages of the invention, and not to limit the scope of the claims.

Example 1

S1, cutting the hot-dip galvanized steel plate to obtain an initial cut sample with the length of 15mm multiplied by the width of 15mm. As shown in fig. 1-2, the initial cut preferably comprises sequentially contacting: a zinc coating layer 1, a transition layer 2, an inner oxidation layer 3 and a base layer 4, wherein the zinc coating layer 1 has a thickness of about 5 μm, the hot-dip galvanized steel sheet is a hot-dip galvanized ultrahigh-strength steel sheet, and the chemical composition of the base layer 4 is 0.2C-1.8Si-2.6Mn-Fe (wt%).

S2, placing the initial cut sample into a sample chamber of a double-beam type focused ion beam device, setting the voltage to be 20kV, and selecting and positioning a region to be sampled in a secondary electron mode. Under an ion beam window, setting the ion beam voltage to be 30kV and the beam current to be 0.3nA, and depositing a Pt metal protective layer with the thickness of 1.5 mu m in a calibrated region to be sampled, as shown in figure 3.

And S3, digging holes downwards on the two sides of the Pt metal protective layer in the length direction relative to the initial cutting sample by using ion beams, wherein the length of each digging hole is 25 mu m, the width of each digging hole is 13 mu m, the depth of each digging hole is 13 mu m, and the inclination angle alpha of each digging hole is 45 degrees. Determining the size to be sampled: length 23 μm and width (i.e. in the direction of the depth of the pit) 12 μm (including the Pt metal cap layer on top of the sample body), as shown in figures 4-5.

And S4, cutting off the bottom of the removed sample, thinning the metal on the other side, suspending one end of the nanometer robot close to the Pt metal protection layer above the Pt metal protection layer without contact, and depositing a Pt metal connector between the nanometer robot and the Pt metal protection layer A by using ion beams to weld the nanometer robot and the Pt metal protection layer A together, as shown in FIG. 7. And then, cutting off the residual joint at the top by using the focused ion beam, so that the sample to be sampled is completely disconnected from the initial cut sample. Then, the nanomachinery hand is lifted up, and the sample is extracted, as shown in fig. 8.

S5, operating the nanometer robot to transfer the sample to the copper support, depositing a Pt metal connecting layer B (with the thickness of 1.5 mu m) at the joint between the sample and the copper support, and welding the sample and the copper mesh together, as shown in FIG. 9. Thereafter, the nanomachiner hand is separated from the sample as shown in fig. 10.

S6, processing the copper support by using ion beam bombardment to form three support columns below the metal connecting layer, wherein the three support columns are all connected with the metal connecting layer B and are distributed at equal intervals, two support columns at two ends are respectively flush with the end faces at two ends of the Pt metal connecting layer B, the width of the middle support column is 4 micrometers, and the widths of the support columns at two ends are both 3 micrometers, as shown in figures 11-12.

S7, carrying out region division on the sample: extending towards the inside of the sample along the standing direction of the three support columns, and forming two extension zones, namely an extension zone 1 and an extension zone 2, in the sample; dividing the extension area 1 into two areas along the width direction of the sample, wherein the boundary is positioned in a galvanized layer of the sample or at the junction of the galvanized layer and a transition layer, the area close to the metal protection layer is marked as a sample 1 area, and the remaining area close to the metal connecting layer is marked as a to-be-cut area 1; dividing the extension region 2 into two regions along the width direction of the sample, wherein the boundary is positioned in a galvanized layer of the sample, the region close to the metal protection layer is marked as a region 2' to be cut, and the remaining region close to the metal connecting layer is marked as a mixed region 2; extending the area 2' to be cut to the side of the sample end far away from the area of the sample 1 along the length direction of the sample until the area is flush with the side of the sample end, and marking the area as the area 2 to be cut; the mixed region 2 is divided into two regions, a boundary line is located in the base layer of the sample or at the boundary between the base layer and the metal connection layer, a region below the boundary line is designated as a region 3 to be cut, and the remaining region is designated as a sample 2 region. As shown in fig. 13-14. Wherein, the sizes of all parts are as follows: area to be cut 1: length 8 μm, width 5 μm; area to be cut 2: length 11 μm, width 4 μm; area to be cut 3: the length was 8 μm and the width was 4 μm. Sample 1 zone: the length is 8 μm, and the width is 6 μm; sample 2 zone: the length is 8 μm and the width is 6 μm.

Cutting the sample: and cutting the area to be cut 1, the area to be cut 2 and the area to be cut 3 by using an ion beam to obtain a cut sample, as shown in fig. 15.

S8, depositing a Pt metal layer (with the thickness of 1.5 microns) on the upper surface of the sample 2, and then carrying out ion thinning on the sample 1 and the sample 2 until the thickness is less than 100nm to obtain a final product sample, as shown in figures 16-19, wherein the region (1) is a Pt metal protective layer, the region (2) is a zinc coating layer, the region (3) is a transition layer + an internal oxidation layer + a base layer, and the width ratio of the region (2) to the region (3) in the sample 2 is about 1: 3.

The obtained sample is observed in an SEM mode in a dual-beam focused ion beam apparatus, and the result is shown in fig. 20, fig. 20 is an SEM image of the sample obtained in example 1, and it can be seen that two samples, sample 1 and sample 2, can be observed at the same time, and that sample 2 has good integrity and continuity at different layer interfaces.

The foregoing examples are included merely to facilitate an understanding of the principles of the invention and their core concepts, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention. The scope of the invention is defined by the claims and may include other embodiments that occur to those skilled in the art. Such other embodiments are intended to be within the scope of the claims if they have structural elements that approximate the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.

Claims (10)

1. The preparation method of the transmission electron microscope test sample for the cross section of the hot-dip galvanized steel sheet is characterized by comprising the following steps of:

s1, cutting a hot-dip galvanized steel plate to obtain an initial cut sample;

s2, placing the initial cutting sample into a sample chamber of a double-beam type focused ion beam device, and selecting and positioning a region to be sampled on the surface of the initial cutting sample in a secondary electron mode; then, depositing a metal protective layer on the area to be sampled in an ion beam mode;

s3, digging pits in the initial cutting sample along two sides of the length direction of the metal protection layer, forming two pit grooves below the metal protection layer, and taking a sample surrounded between the two pit grooves as a sample to be sampled;

s4, carrying out U-shaped cutting on the to-be-sampled part connected below the metal protective layer, specifically, removing one side and the bottom of the to-be-sampled part, and leaving part of the other side for connection; then cutting off the connection of the part to separate the sample to be sampled from the initial cutting sample, and then taking out the sample;

s5, transferring the sample to a metal support, and depositing a metal connecting layer at the joint between the sample and the metal support to weld the sample and the metal support together;

s6, processing the metal support to form three support columns below the metal connecting layer; the three supporting columns are all connected with the metal connecting layer and are distributed at equal intervals;

s7, carrying out area division and cutting on the sample:

area division:

extending towards the inside of the sample along the standing direction of the three support columns, and forming two extension zones, namely an extension zone 1 and an extension zone 2, in the sample;

dividing the extension area 1 into two areas along the width direction of the sample, wherein a boundary is positioned in a zinc coating layer of the sample or at the junction of the zinc coating layer and a transition layer, the area close to the metal protection layer is marked as a sample 1 area, and the remaining area close to the metal connecting layer is marked as a to-be-cut area 1;

dividing the extension region 2 into two regions along the width direction of the sample, wherein the boundary is positioned in a galvanized layer of the sample, the region close to the metal protection layer is marked as a region 2' to be cut, and the remaining region close to the metal connecting layer is marked as a mixed region 2; extending the area 2' to be cut to the side of the sample end far away from the area of the sample 1 along the length direction of the sample until the area is flush with the side of the sample end, and marking the area as the area 2 to be cut; dividing the mixed area 2 into two areas, wherein a boundary is positioned in a base layer of a sample or at the junction of the base layer and a metal connecting layer, the area below the boundary is marked as an area 3 to be cut, and the rest area is marked as an area of the sample 2;

cutting:

cutting the area to be cut 1, the area to be cut 2 and the area to be cut 3 to form a sample 1 and a sample 2;

s8, depositing a metal protective layer on the upper surface of the sample 2, and then carrying out ion thinning on the sample 1 and the sample 2 to obtain a transmission electron microscope test sample of the hot-dip galvanized steel plate.

2. The method according to claim 1, wherein in step S1, the initial cut sample comprises sequentially contacting: a zinc coating, a transition layer, an internal oxidation layer and a base layer.

3. The method according to claim 1, wherein in the step S2:

the conditions of the secondary electron mode are: the voltage is 10-30 kV;

the conditions of the ion beam mode are: the voltage is 10-30 kV, and the ion beam current is 0.1-0.3 nA.

4. The production method according to claim 1, wherein in the step S2, the metal protective layer is a Pt metal protective layer.

5. The production method according to claim 1 or 4, wherein in the step S2, the metal protective layer has a length of 23 to 25 μm, a width of 2.5 to 3 μm, and a thickness of 1.5 to 2 μm.

6. The manufacturing method according to claim 1, wherein the step S4 further includes, between the U-shaped cutting and the cutting: welding a nanometer robot hand and the metal protective layer together;

after the cutting, the nanomachinery hand is lifted up, and thus a sample is extracted.

7. The preparation method according to claim 6, wherein the welding of the nanomachine hand and the metal protection layer specifically comprises: depositing a metal connector between the nanometer robot hand and the metal protective layer by using ion beams to weld the nanometer robot hand and the metal protective layer together;

the metal connector is a Pt metal connector.

8. The method according to claim 1, wherein in the step S3, the pit has a length of 23 to 25 μm, a width of 12 to 15 μm, and a depth of 12 to 15 μm.

9. The preparation method according to claim 1, wherein in the step S6, two support columns at two ends of the three support columns are respectively flush with end faces at two ends of the metal connecting layer;

the width of the two support columns at the two ends is smaller than that of the middle support column.

10. The method according to claim 1, wherein in step S5, the metal connection layer is a Pt metal connection layer;

in the step S7, the width of the zinc coating layer to the width of all the other layers in the sample 2 area is 1: 3.

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