阅读说明：本技术 扩散焊叠层缺陷超声检测试块、其制备方法及应用 (Ultrasonic detection test block for diffusion welding lamination defects, and preparation method and application thereof ) 是由 宋慧 熊江涛 尹小康 李京龙 宋文清 于 2021-01-20 设计创作，主要内容包括：本发明公开了扩散焊叠层缺陷超声检测试块、其制备方法及应用,涉及扩散焊技术领域。扩散焊叠层缺陷超声检测试块,其由自上而下叠加装配的多层基板进行扩散焊形成,在相邻的两层基板之间的扩散焊界面位置处均具有缺陷槽,且位于上一层的缺陷槽与相邻的位于下一层的缺陷槽呈交叉状态。利用呈交叉状态的缺陷槽形成组配,可以形成微米级缺陷上下层重叠的多种尺寸组配,以便于研究在上层微米级缺陷信号的影响下,下层微米级缺陷的检出能力。同时可以利用无交叉部分,即缺陷不存在上下层重叠的单层缺陷作为参考缺陷。提升多层缺陷重叠时下层微米级缺陷的检出精度,提升多层扩散焊缺陷检测的检测效果。(The invention discloses a diffusion welding lamination defect ultrasonic detection test block, a preparation method and application thereof, and relates to the technical field of diffusion welding. The ultrasonic testing block for detecting the defects of the diffusion welding lamination is formed by performing diffusion welding on a plurality of layers of base plates which are assembled in a superposition mode from top to bottom, defect grooves are formed in the positions of diffusion welding interfaces between two adjacent layers of base plates, and the defect grooves in the upper layer and the adjacent defect grooves in the lower layer are in a crossed mode. The defect grooves in the cross state are used for forming assembly, and the assembly with various sizes of the micron-sized defects overlapped with the upper layer and the lower layer can be formed, so that the detection capability of the micron-sized defects of the lower layer under the influence of the micron-sized defect signals of the upper layer can be conveniently researched. Meanwhile, a single-layer defect without an intersection part, namely a defect without overlapping an upper layer and a lower layer, can be used as a reference defect. The detection precision of the lower-layer micron-sized defects when the multiple layers of defects are overlapped is improved, and the detection effect of the multiple-layer diffusion welding defect detection is improved.)

1. A diffusion welding lamination defect ultrasonic detection test block is characterized in that the diffusion welding lamination defect ultrasonic detection test block is formed by performing diffusion welding on a plurality of layers of base plates which are assembled in a superposition mode from top to bottom, defect grooves are formed in the positions of diffusion welding interfaces between two adjacent layers of base plates, and the defect grooves in the upper layer are in a crossed state with the adjacent defect grooves in the lower layer.

2. The ultrasonic testing block for the defects of the diffusion welding lamination as claimed in claim 1, wherein the defect groove of each layer extends from one end of the substrate to the other opposite end, and the defect groove of each layer is a plurality of grooves arranged at intervals;

preferably, the groove widths of the plurality of defective grooves of each layer are different, and the groove widths of the defective grooves are all between 70 and 250 μm;

preferably, the distance between two adjacent defect grooves on each layer is 4-6 mm.

3. The ultrasonic testing block for the defects of the diffusion welding lamination according to claim 1 or 2, wherein the defect groove located at the upper layer and the adjacent defect groove located at the lower layer are in a cross state;

preferably, the defect grooves in the previous layer extend in a first direction, and the defect grooves in the next layer extend in a second direction perpendicular to the first direction.

4. The ultrasonic testing block for detecting the defects of the diffusion welding lamination as claimed in claim 3, wherein each layer of the defect grooves is 4, and the groove widths of the 4 defect grooves are 70-90 μm, 90-110 μm, 140-160 μm and 190-210 μm in sequence.

5. The method for preparing the ultrasonic testing block for the defects of the diffusion welding lamination as claimed in any one of claims 1 to 4, is characterized in that the multilayer substrate is superposed and assembled from top to bottom and then diffusion welding is carried out;

after the two substrates are stacked and assembled, at least one of the two contact plate surfaces of the two adjacent substrates is provided with a defect groove, and the defect groove positioned on the upper layer and the adjacent defect groove positioned on the lower layer are in a crossed state.

6. The method for preparing the multilayer substrate according to claim 5, wherein the multilayer substrate is sequentially a first substrate to an Nth substrate from top to bottom, and defect grooves are formed in the surfaces of the second substrate to the Nth substrate on one side close to the first substrate;

preferably, the number of the multilayer substrate is 3-5 layers;

preferably, the defective groove is formed by milling.

7. The production method according to claim 5, wherein each of the substrates is subjected to surface cleaning before the multilayer substrate is assembled;

preferably, the surface cleaning comprises grinding, polishing, acid washing, water washing and drying which are sequentially carried out;

preferably, the polishing is carried out by using polishing solution formed by silica sol and hydrogen peroxide; more preferably, the mass ratio of the silica sol to the hydrogen peroxide is 9-11: 1;

preferably, the acid washing is performed by using HF, HCl and HNO₃Washing with water for 1-2 min;

preferably, the rinsing time of the water washing process is 20-40 min.

8. The production method according to claim 7, characterized in that solvent washing is performed between the acid washing and the water washing;

preferably, the solvent washing is washing with at least one of ethanol, methanol and propanol;

preferably, the solvent cleaning is performed by ultrasonic cleaning, and the cleaning time is 8-15 min.

9. The method as claimed in claim 5, wherein the welding temperature of the diffusion welding process is 800-;

preferably, the welding temperature is 840-860 ℃, and the welding pressure is 1.8-2.2 MPa;

preferably, the heat preservation time of the diffusion welding process is 50-70 min;

preferably, solder masks are added to both sides of the multilayer substrate during assembly.

10. Use of the diffusion welding lamination defect ultrasonic detection test block of any one of claims 1-4 in diffusion welding defect detection.

Technical Field

The invention relates to the technical field of diffusion welding, in particular to a diffusion welding lamination defect ultrasonic detection test block, and a preparation method and application thereof.

Background

In order to ensure the accuracy, repeatability and comparability of the detection results in ultrasonic detection, the detection system must be calibrated with a sample having known fixed characteristics. The sample with simple geometric shape artificial reflector or simulated defect designed and manufactured according to certain application is generally called test block, and the test block for ultrasonic detection is generally divided into standard test block, comparison test block and simulated test block. The artificial reflector in the test block is selected according to the purpose, should be as close as possible to the defect characteristics to be detected, usually the required shape and size are processed in the material or on the surface by a mechanical processing mode, and the common artificial reflector mainly comprises a long transverse hole, a short transverse hole, a transverse through hole, a flat bottom hole, a V-shaped groove, other line cutting grooves and the like.

The transverse through hole and the long transverse hole have the characteristics of axial symmetry, stable reflection amplitude and linear defect characteristics, and generally represent that the inside of a workpiece has cracks, incomplete penetration, incomplete fusion and strip-shaped slag inclusion with certain length. It is commonly used in ultrasonic testing of butt joints, weld overlays, and also in bolt pieces and castings. The short transverse hole is characterized by a linear reflector in an incoming field region and a point reflector in a far field region, and is mainly used for butt welding joint detection. The flat bottom hole generally has the characteristic of a point-shaped area type reflector, is mainly used for ultrasonic detection of forgings, steel plates, butt-joint welding joints, composite plates and surfacing layers, and is generally suitable for calibration and detection of a straight probe and a twin probe. V-grooves and other cut grooves feature linear defects with open surfaces. The device is suitable for transverse wave detection of workpieces such as steel plates, steel pipes, forgings and the like, and can also simulate the defects on the surfaces or near surfaces of other workpieces or butt joints to adjust the detection sensitivity.

The existing method for preparing the test block has a multi-layer welding mode besides mechanical processing inside or on the surface of the material, and meets the requirement of higher precision by processing the defect with a specific shape and then performing multi-layer diffusion welding. Meanwhile, because the upper-layer defect and the lower-layer defect are overlapped and assembled in the test block, the problems of signal interference of the upper-layer defect to the lower-layer defect and detectability of the lower-layer defect under the micron-scale defect scale can be researched by utilizing the assembly.

However, the conventional method for preparing a test block has the following disadvantages: (1) because the diffusion welding defects exist in the joint, namely the diffusion welding interface position, and the dimension is micron-sized, the position precision cannot be ensured and the dimension precision cannot be ensured by the traditional machining mode, namely the machining of the internal micron-sized artificial reflector is difficult to realize. (2) Although the method of surface turning and processing threads on the surface to be welded can realize defect prefabrication at a diffusion welding interface, the dimensional precision is difficult to ensure, the shape is uneven, and a test block is difficult to form. (3) The existing prefabrication method for the multilayer defects can only manufacture macroscopic defects, can not realize prefabrication of diffusion welding multilayer micron-sized defects, does not have assembly of upper and lower layer defects, and is difficult to form test blocks.

In view of this, the invention is particularly proposed.

Disclosure of Invention

The invention aims to provide a diffusion welding lamination defect ultrasonic detection test block and a preparation method thereof, and aims to prepare a test block with higher forming precision by forming assembly by using upper and lower layer defects.

The second purpose of the invention is to provide the application of the diffusion welding lamination defect ultrasonic detection test block in diffusion welding defect detection.

The invention is realized by the following steps:

the embodiment of the invention provides a diffusion welding lamination defect ultrasonic detection test block which is formed by performing diffusion welding on a plurality of layers of substrates which are assembled in a superposition mode from top to bottom, wherein defect grooves are formed in the positions of diffusion welding interfaces between two adjacent layers of substrates, and the defect groove in the upper layer and the adjacent defect groove in the lower layer are in a crossed mode.

The embodiment of the invention also provides a preparation method of the ultrasonic testing block for the diffusion welding lamination defects, which comprises the steps of stacking and assembling the multilayer substrates from top to bottom and then performing diffusion welding; after the two adjacent layers of substrates are assembled in a superposition mode, at least one of the two contact plate surfaces of the two adjacent layers of substrates is provided with a defect groove, and the defect groove on the upper layer and the adjacent defect groove on the lower layer are in a crossed state.

The embodiment of the invention also provides application of the ultrasonic testing block for the diffusion welding lamination defect in the diffusion welding defect detection.

The invention has the following beneficial effects: the ultrasonic testing block for detecting the diffusion welding lamination defects is prepared by a multi-layer diffusion welding mode, defect grooves are formed in the positions of diffusion welding interfaces between two adjacent layers of substrates, and the defect groove in the upper layer and the adjacent defect groove in the lower layer are in a crossed state. The defect grooves in the cross state are used for forming assembly, and the assembly with various sizes of the overlapped upper layer and the lower layer of the micron-sized defects can be formed, so that the detection capability of the micron-sized defects of the lower layer under the influence of the signal of the micron-sized defects of the upper layer can be conveniently researched.

In the using process, the non-cross part, namely the defect does not have the single-layer defect overlapped by the upper layer and the lower layer, can be used as a reference defect, the detection precision of the lower-layer micron-sized defect when the multi-layer defect is overlapped is improved, the detection precision of the test block is improved, and the detection effect of the multi-layer diffusion welding defect detection is improved.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.

FIG. 1 is a schematic view of a diffusion bond joint interface defect;

FIG. 2 is a schematic view of diffusion wire bonding defect prefabrication;

FIG. 3 is an assembly view of the test block of comparative example 1;

FIG. 4 is an assembly view of the test block of comparative example 3;

FIG. 5 is an ultrasonic C-scan test chart of the test block prepared in example 1;

FIG. 6 is an ultrasonic C-scan test chart of a test block prepared in comparative example 1;

FIG. 7 is an ultrasonic C-scan test chart of a test block prepared in comparative example 3;

fig. 8 is a metallographic cross-sectional view of comparative example 3.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.

In an actual welding manufacturing process, in order to pursue the complexity of the structure, the deformation amount after welding needs to be controlled, and all process parameters in the welding process cannot be satisfied at the same time, which may cause welding defects such as non-welding (fig. 1 (a)), weak connection (fig. 1 (b)), holes (fig. 1 (c)) and the like at the interface as shown in fig. 1. The weld formed by diffusion welding is a quasi-two-dimensional interface region with a small thickness, so that the defect of diffusion welding can be equivalent to the defect of a two-dimensional plane without the thickness.

The lack of welding refers to the existence of obvious continuous defects at the welding interface, and the main reasons for the occurrence of the defects are generally low welding temperature, insufficient welding pressure, insufficient heat preservation time or low vacuum degree and other process deviations. In addition, when the surface to be welded is contaminated or has a large roughness, the defect of non-welded interface is easily generated, and usually, the non-welded interface is easily generated at the edge part of the welded sample due to the uneven distribution of the stress of the interface. The weak connection means that the two welding interfaces are only in close physical contact without atomic bonding, and the gap size is in the micron order. The void defects are discrete small voids, typically on the order of microns in size, which is one of the most common defects in diffusion welding. When the welding temperature is low, the welding pressure is low, or the roughness of the surface to be welded is large, the interface hole is not completely closed, and then the defect of the micro-hole is formed.

Aiming at the welding head interface defects in diffusion welding, a targeted test block is needed to be adopted for calibration before ultrasonic detection, so that the accuracy of ultrasonic detection is improved. And aiming at different types of welding defects, the types of the adopted test blocks are different. The test block provided in the embodiment of the application is formed by assembling the defects of the upper layer and the lower layer aiming at the micron-sized linear defects.

The embodiment of the invention provides a preparation method of a diffusion welding lamination defect ultrasonic detection test block, which is prepared in a multilayer diffusion welding mode and specifically comprises the following steps:

s1 processing substrate defects

As shown in fig. 2 (a), a groove-like defect is processed on the substrate. In some embodiments, the substrate may be formed by a milling process, using a milling tool.

The number of substrates is not limited and may be 3-5 layers, such as 3 layers, 4 layers, or 5 layers, in some embodiments. In other embodiments, the number of layers of the substrate may be more, and is not limited herein.

In order to further improve the assembly effect, the inventor specifically optimizes groove-shaped defects on the substrate, such as groove width, space and the like. In some preferred embodiments, the defect grooves each extend from one end of the substrate to the opposite end, and the defect groove on each substrate is a plurality of defect grooves arranged at intervals. Through setting up a plurality of defect groove intervals, keep certain interval and can guarantee that the supersound echo signal of defect groove and defect groove does not influence each other.

In some preferred embodiments, the plurality of defective trenches of each layer have different trench widths, and the trench widths of the defective trenches are preferably 70-250 μm, so as to form a defective trench of a micrometer scale. In the actual operation process, milling cutters with different processing sizes can be used for processing and forming on the substrate, and the distance between every two adjacent defect grooves is preferably 4-6mm, so that ultrasonic echo signals of the two adjacent defect grooves are not affected by each other.

In some embodiments, the number of the defect trenches on each substrate is 4, and the trench widths of the 4 defect trenches are 70-90 μm, 90-110 μm, 140-160 μm and 190-210 μm, such as 80 μm, 100 μm, 150 μm and 200 μm, such as 70 μm, 90 μm, 140 μm and 190 μm, such as 90 μm, 110 μm, 160 μm and 210 μm.

S2 substrate surface treatment

Before assembling the multilayer substrates, surface cleaning is carried out on each layer of substrate, and strict surface cleaning is mainly carried out on the to-be-welded surfaces of the non-defect positions of the substrates so as to ensure the welding quality.

In some preferred embodiments, the surface cleaning comprises grinding, polishing, pickling, washing with water and drying, which are performed sequentially. The substrate is generally a titanium alloy plate with the size of 25 × 25 × 2mm, the surface of the titanium alloy plate is polished to be smooth, the titanium alloy plate is polished to be a mirror surface, an oxide film on the surface of the substrate is removed through acid cleaning, and the titanium alloy plate is washed with water and dried to obtain a clean plate.

The grinding, polishing and acid washing modes are not limited, and can be conventional treatment modes in the prior art, so as to achieve the purpose of smoothing and cleaning the surface of the substrate. Wherein, the surface can be gradually polished by sand paper.

In some embodiments, the polishing is carried out by using a polishing solution formed by silica sol and hydrogen peroxide; the mass ratio of the silica sol to the hydrogen peroxide is 9-11: 1. By further optimizing the composition of the polishing solution, the surface of the substrate after polishing is made to be a mirror surface and maintained in parallelism.

In some embodiments, the acid wash is performed with HF, HCl, HNO₃Washing with water for 1-2 min; the rinsing time of the water washing process is 20-40 min. The acid washing is performed by using a Keller reagent prepared in advance, the concentration of each component in the components is not limited too much, and 1ml of HF, 1.5ml of HCl and 2.5ml of HNO can be used₃And 95ml of H₂Formation of O configuration, HF, HCl and HNO₃All are commercially available concentrated acids. And removing the residual polishing solution and pickling solution on the surface of the substrate by washing so as to avoid influencing diffusion welding.

In some embodiments, to optimize the cleaning effect, a solvent cleaning may be performed between the acid washing and the water washing. The solvent cleaning is performed by using at least one of ethanol, methanol and propanol, such as absolute ethanol, to remove the polishing solution better. The solvent cleaning is carried out by ultrasonic cleaning for 8-15 min.

S3 diffusion welding assembly

When a to-be-welded sample is loaded into a furnace, the sample is reasonably assembled firstly, the multilayer substrates are superposed and assembled from top to bottom, at least one of two contact plate surfaces of two adjacent layers of substrates is provided with a defect groove after superposition and assembly, and the defect groove on the upper layer and the adjacent defect groove on the lower layer are in a crossed state. And crossing the defect grooves on the two adjacent layers of substrates to form assembly, and preparing a test block with higher forming precision.

In some embodiments, the defect groove in the upper layer and the adjacent defect groove in the lower layer are in a cross state; that is, as shown in fig. 2 (b), the defect grooves in the previous layer extend in a first direction, the adjacent defect grooves in the next layer extend in a second direction perpendicular to the first direction, and the defect grooves in the previous layer are intersected with the defect grooves in the next layer to form an assembly.

As shown in fig. 2, the multilayer substrates are sequentially a first substrate to an nth substrate from top to bottom, defect grooves are formed on the second substrate to the nth substrate on the side surfaces close to the first substrate, and the first substrate is a cover plate and is not processed with the defect grooves.

In the actual operation process, the two substrates shown in fig. 2a can be crossed and covered with the cover plate, the surfaces to be welded are fitted and centered, and the misalignment of the sample is prevented to ensure that the pressure can be uniformly applied to the surfaces to be welded; mica sheets are added between the upper surface and the lower surface of the sample and the contact position of the pressure head to serve as solder masks (namely, the solder masks are added on two sides of the multilayer substrate), so that diffusion bonding between the sample and the pressure head is prevented. After the sample was assembled, it was placed in an FJK-2 type diffusion welder at a height centered in the oven cavity and initial pressure was applied to bring the joints into intimate contact.

S4, diffusion welding

The multilayer substrate can be compositely molded by multilayer diffusion welding, and the defect groove in the multilayer substrate is reserved. In order to further improve the welding effect, the inventor further optimizes parameters such as welding temperature, pressure, heat preservation time and the like, wherein the welding temperature in the diffusion welding process is 800-.

In a preferred embodiment, the welding temperature is 840-860 ℃ and the welding pressure is 1.8-2.2 MPa. By further optimizing the welding parameters, the welding effect is ensured, other defects do not exist except for the defect groove of the multilayer substrate, and the precision of the test block is ensured.

The embodiment of the invention also provides a diffusion welding lamination defect ultrasonic detection test block which is formed by performing diffusion welding on a plurality of layers of substrates which are assembled in a superposition mode from top to bottom, wherein defect grooves are formed in the positions of diffusion welding interfaces between two adjacent layers of substrates, and the defect groove positioned on the upper layer and the adjacent defect groove positioned on the lower layer are in a crossed mode. The method can be prepared by the preparation method, the adjacent two layers of defect grooves are formed and matched, the method can be applied to the detection of the defects of the multi-layer diffusion welding, the problems of signal interference of micro defects of upper and lower layers and detection of the defects of the lower layer in the multi-layer diffusion welding structure can be researched, the detection capability of the defects of the multi-layer diffusion welding structure is improved, and the detection precision of the defects of the lower layer can be improved.

The features and properties of the present invention are described in further detail below with reference to examples.

Example 1

The embodiment provides a method for preparing a diffusion welding lamination defect ultrasonic detection test block, as shown in fig. 2, including:

(1) substrate defect processing

Taking 3 substrates (TC4 plates), wherein one substrate is used as a cover plate and is not subjected to defect processing, the other 2 substrates are processed into line groove-shaped defects with the widths of 80 microns, 100 microns, 150 microns and 200 microns by using milling cutters with different processing sizes, and the center distance between two adjacent defect grooves is 5 mm.

(2) Surface treatment of substrates

The method comprises the following steps of (1) carrying out surface cleaning on a to-be-welded surface of a non-defect position of a substrate to ensure welding quality, and specifically comprising the following steps: first, the surface was polished stepwise with sandpaper, and polished to a mirror surface with a polishing solution (silica sol: hydrogen peroxide: 10:1) while maintaining parallelism. Keller reagent (1ml HF +1.5ml HCl +2.5ml HNO) was used before weld assembly₃+95ml H₂O) pickling a sample to be welded for 2 minutes, taking out the sample and putting the sample into anhydrous BUltrasonic cleaning in alcohol for 10 min, rinsing with clear water for 30min, and blow-drying with cold air.

(3) Diffusion welding assembly

And (3) adding cover plates to the two substrates in a crossed manner, fitting and centering the surfaces of the surfaces to be welded, and adding mica sheets between the upper surface and the lower surface of the sample and the contact position of the pressure head to serve as solder masks.

(4) Diffusion welding

After assembly was completed, the assembly was loaded into an FJK-2 type diffusion welder with the height at the center of the oven cavity and initial pressure was applied to bring the connection joints into intimate contact. Controlling the welding temperature to 850 ℃, the welding pressure to be 2MPa and the heat preservation time to be 60min, and operating the program to weld. And slowly cooling after heat preservation is finished to form a diffusion welding joint, and reserving the prefabricated defects at the diffusion welding interface position to form a test block.

Example 2

The embodiment provides a method for preparing a diffusion welding lamination defect ultrasonic detection test block, as shown in fig. 2, including:

(1) substrate defect processing

Taking 3 substrates (TC4 plates), wherein one substrate is used as a cover plate and is not subjected to defect processing, the other 2 substrates are processed into line groove-shaped defects with the widths of 70 micrometers, 90 micrometers, 140 micrometers and 190 micrometers by using milling cutters with different processing sizes, and the center distance between two adjacent defect grooves is 4 mm.

(2) Surface treatment of substrates

The method comprises the following steps of (1) carrying out surface cleaning on a to-be-welded surface of a non-defect position of a substrate to ensure welding quality, and specifically comprising the following steps: first, the surface was polished stepwise with sandpaper, and polished to a mirror surface with a polishing solution (silica sol: hydrogen peroxide: 9:1) while maintaining parallelism. Keller reagent (1ml HF +1.5ml HCl +2.5ml HNO) was used before weld assembly₃+95ml H₂O) pickling the sample to be welded for 1 minute, taking out, putting the sample into absolute ethyl alcohol, ultrasonically cleaning for 8 minutes, taking out, rinsing with clear water for 20 minutes, and drying with cold air for later use.

(3) Diffusion welding assembly

And (3) adding cover plates to the two substrates in a crossed manner, fitting and centering the surfaces of the surfaces to be welded, and adding mica sheets between the upper surface and the lower surface of the sample and the contact position of the pressure head to serve as solder masks.

(4) Diffusion welding

After assembly was completed, the assembly was loaded into an FJK-2 type diffusion welder with the height at the center of the oven cavity and initial pressure was applied to bring the connection joints into intimate contact. Controlling the welding temperature at 800 ℃, the welding pressure at 1.5MPa and the heat preservation time at 70min, and operating the program to weld. And slowly cooling after heat preservation is finished to form a diffusion welding joint, and reserving the prefabricated defects at the diffusion welding interface position to form a test block.

Example 3

The embodiment provides a method for preparing a diffusion welding lamination defect ultrasonic detection test block, as shown in fig. 2, including:

(1) substrate defect processing

Taking 3 substrates (TC4 plates), wherein one substrate is used as a cover plate and is not subjected to defect processing, the other 2 substrates are processed into line groove-shaped defects with the widths of 90 micrometers, 110 micrometers, 160 micrometers and 210 micrometers by using milling cutters with different processing sizes, and the center distance between two adjacent defect grooves is 6 mm.

(2) Surface treatment of substrates

The method comprises the following steps of (1) carrying out surface cleaning on a to-be-welded surface of a non-defect position of a substrate to ensure welding quality, and specifically comprising the following steps: first, the surface was polished stepwise with sandpaper, and polished to a mirror surface with a polishing solution (silica sol: hydrogen peroxide: 11:1) while maintaining parallelism. Keller reagent (1ml HF +1.5ml HCl +2.5ml HNO) was used before weld assembly₃+95ml H₂O) pickling the sample to be welded for 2 minutes, taking out, putting the sample into absolute ethyl alcohol, ultrasonically cleaning the sample for 15 minutes, taking out, rinsing the sample with clean water for 40 minutes, and drying the sample with cold air for later use.

(3) Diffusion welding assembly

And (3) adding cover plates to the two substrates in a crossed manner, fitting and centering the surfaces of the surfaces to be welded, and adding mica sheets between the upper surface and the lower surface of the sample and the contact position of the pressure head to serve as solder masks.

(4) Diffusion welding

After assembly was completed, the assembly was loaded into an FJK-2 type diffusion welder with the height at the center of the oven cavity and initial pressure was applied to bring the connection joints into intimate contact. Controlling the welding temperature at 900 ℃, the welding pressure at 2.5MPa and the heat preservation time at 50min, and operating the program to weld. And slowly cooling after heat preservation is finished to form a diffusion welding joint, and reserving the prefabricated defects at the diffusion welding interface position to form a test block.

Comparative example 1

The comparative example provides a preparation method of a diffusion welding lamination defect ultrasonic detection test block, which is different from the embodiment 1 in that: the shapes of the defects processed on the substrates are different, and the specific shape is that circular holes are processed on the substrates of different layers, the sizes of the circular holes are phi 80 μm and phi 100 μm, and the defect intervals are set to be 5 mm. The schematic view is shown in fig. 3, fig. 3a is a front view, and fig. 3b is a top view of the second laminate.

Comparative example 2

The comparative example provides a preparation method of a diffusion welding lamination defect ultrasonic detection test block, which is different from the embodiment 1 in that: the diffusion welding temperature was 700 ℃.

Comparative example 3

The comparative example provides a preparation method of a diffusion welding lamination defect ultrasonic detection test block, which is different from the embodiment 1 in that: the substrates are assembled in different ways, specifically, linear defects on the substrates of different layers are arranged in parallel rather than crossing perpendicularly, and the schematic diagram is shown in fig. 4.

Test example 1

Performing ultrasonic C-scan detection on the test block prepared in the example 1, selecting a probe with the frequency of 50MHz, the diameter of a wafer of 6mm and the focal length of 20mm, and performing ultrasonic C-scan detection on the laminated defect test block, wherein FIG. 5 is an ultrasonic C-scan image of the laminated defect, and (a) is the distribution of the laminated defect with a focus focused at the depth position of the centers of the upper and lower defects; (b) upper defect distribution with focus focused at upper defect depth; (c) lower layer defect distribution focused at a lower layer defect depth for a focus; (d) scan the overlay defect distribution C.

The ultrasound C-scan was performed in three times:

the first time is rough scanning, the water distance is adjusted, the sound beam emitted by the probe is focused on the middle position of the defect of the upper layer and the lower layer, namely the middle 3mm depth position of the TC4 plate of the second layer, a signal gate is arranged, the echo signals of the upper layer and the lower layer are arranged in the gate, and a C-scan image which simultaneously reflects the defect positions of the upper layer and the lower layer is obtained, as shown in (a) in FIG. 5, the defect positions of the upper layer and the lower layer are seen to be distributed in a crossed manner.

The second C-scan experiment is a fine scan, the water distance is adjusted, the acoustic beam emitted by the probe is focused at the upper-layer defect position, i.e., the depth position of the first-layer diffusion welding interface of 2mm, and the gate is also arranged at the depth position, so as to obtain a C-scan image only having the upper-layer defect, as shown in (b) of fig. 5.

The third C-scan experiment is also a fine scan, and the acoustic beam is focused on the position of the lower layer defect, i.e. the position of 4mm depth of the second diffusion welding interface, so as to obtain a C-scan image of only the lower layer defect as shown in (C) in fig. 5. In order to visually represent the corresponding relationship of the upper and lower layer defects, (a) in fig. 5 is colorized by image processing, and the corresponding sizes of the upper and lower layer defects are marked, so that an ultrasonic C-scan color image (which is subjected to gray processing to meet the patent publication requirements) shown in fig. 5(d) is obtained.

Test example 2

And (3) carrying out ultrasonic C-scan detection on the test block prepared in the comparative example 1, selecting a probe with the frequency of 50MHz, the diameter of the wafer of 6mm and the focal length of 20mm, and carrying out ultrasonic C-scan detection on the defects, wherein FIG. 6 is a corresponding ultrasonic C-scan diagram.

(a) The defect distribution at the position of the defect depth of the upper layer of the focus is shown; (b) selecting an ultrasonic c-scan of the upper layer of point defects with the design size of 100 mu m; (c) lower layer defect distribution focused at a lower layer defect depth for a focus; (d) an ultrasonic c-scan of the design size of 100 mu m of a point defect at the lower layer is selected.

Because the upper and lower layers of circular hole defects need to be aligned in two dimensions, and the size of the defects is only 100 micrometers, the alignment and overlapping of the upper and lower layers of defects in the assembling and processing processes are more difficult to ensure, namely, the assembly of the upper and lower layers of micron-sized defects is difficult to realize by using the method. Meanwhile, the c-scan shows that the round hole defects are difficult to ensure the uniformity in processing, and the shape is irregular. In addition, due to the fact that the micron-sized round hole is difficult to be made into a through hole and located inside the material, the actual size of the material is difficult to verify, and the material cannot be used as a standard test block.

The diffusion welding temperature of the TC4 titanium alloy was lowered in comparative example 2, resulting in failure to form a reliable connection without prefabrication defects, voids and lack of welding, as shown in fig. 1c, and thus failed as a standard coupon.

And (3) carrying out ultrasonic C-scan detection on the test block prepared in the comparative example 3, selecting a probe with the frequency of 50MHz, the diameter of the wafer of 6mm and the focal length of 20mm, and carrying out ultrasonic C-scan detection on the test block with the lamination defects, wherein FIG. 7 is an ultrasonic C-scan image of the lamination defects, FIG. 7a is an ultrasonic C-scan image with the focus of 200 microns of the first-layer welding interface, and FIG. 7b is an ultrasonic C-scan image with the focus of 200 microns of the second-layer welding interface.

FIG. 8 is a metallographic cross-section of comparative example 3, and it was found that it is difficult to ensure that the upper and lower defects overlap completely, i.e., that the assembly is shifted during the assembly process, and that the overlap of the upper and lower defects cannot be ensured.

In summary, the ultrasonic testing block for detecting the diffusion welding lamination defects provided by the embodiment of the present invention is prepared by using a multi-layer diffusion welding method, defect grooves are formed at the diffusion welding interface position between two adjacent layers of substrates, and the defect groove located at the upper layer and the adjacent defect groove located at the lower layer are in an intersection state. And the assembly is formed by utilizing the defect grooves in the cross state, so that the detection precision of the test block is improved, and the detection effect of the diffusion welding defect detection is improved.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.