165 results about "Crack free" patented technology

The invention discloses a high-wear-resistance additive forming titanium-based composite material and a preparation method thereof. The high-abrasion-resistance additive forming titanium-based composite material is mainly composed of a base body and an amorphous ceramic film, and the high-abrasion-resistance additive forming titanium-based composite material is prepared from, by mass, 97.0%-99.8% of the base body and 0.2%-3% of the amorphous ceramic film. By accurately controlling the thickness and the quality of the amorphous ceramic film, the number and the size of the reinforced phases can be regulated and controlled, and the fluidity and the oxidation resistance of the additive manufacturing titanium alloy powder can be remarkably improved through introduction of the amorphous ceramic film; the in-situ synthesis ceramic reinforced titanium-based composite material prepared through additive manufacturing is free of cracks, high in hardness, good in wear resistance and suitable for being used under harsh working conditions.

The invention discloses a corrosion-resistant and wear-resistant composite metal plate, which relates to the technical field of composite metal materials, and is technically characterized by comprising the following steps: firstly, preparing a flux-cored wire, and preparing deposited metal components according to mass percent by using a specific low-carbon steel strip; then, a thick low-carbon steel plate or a low-alloy steel plate serves as a base plate, a double-layer structure is formed through a gradient surfacing technology, a transition layer is prepared according to the proportion, a main wear-resisting layer is formed by fusing and diffusing flux-cored wires and contains various high-hardness wear-resisting phases, the lap joint width is controlled, cooling is conducted, and a surfacing composite layer is formed; the surfacing composite layer is integrally leveled through a press machine, and a semi-finished product is obtained; and finally, mixing organic silicon modified polyester resin and the like to prepare a joint sealing agent, coating the semi-finished product for 3-4 layers, and curing to obtain a finished product. The wear-resistant layer is free of cracks, and the corrosion resistance of the base body is improved.

The present invention relates to a method for manufacturing a part (1) with improved resistance to oxidation and high-temperature corrosion, comprising at least the deposition of a non-cracked crystalline β-Yb2Si2O7 environmental barrier layer (7) on an at least partially ceramic matrix composite material (3), wherein the environmental barrier layer is deposited by chemical vapour deposition from a gas phase comprising a precursor mixture of (a) a compound A of formula SiClxHy, in which x is an integer from 1 to 4 and y is an integer from 0 to 3, with x + y = 4, and (b) elementary ytterbium or ytterbium(III) chloride, and wherein, during deposition, a temperature between 1100°C and 1300°C and a pressure of 150 mbar or less are imposed.

A SiC carrier wafer has a diameter of at least 7.5 cm and a height between 200 μm and 500 μm. The wafer includes an inner section and an outer section. The outer section surrounds the inner section and the inner section includes a part of a SiC growth substrate. The inner section is formed by a crystal structure that is predominantly formed by a 3C crystal structure. The outer section is formed by a crystal structure predominantly formed by a 3C crystal structure and includes crystallites extending in length direction of the individual crystallite of more than 5 μm. A bow of the wafer is less than 50 μm and a warp of the wafer is less than 50 μm. The crystal structure of the inner section and the crystal structure of the outer section are Nitrogen doped and have an electric resistivity less than 0.03 Ohm-cm.

The invention discloses ceramic particle reinforced medium-entropy alloy powder with large density difference as well as a preparation method and application thereof. The composite powder consists of 3-5wt% of B4C powder and the balance of CoCrNi alloy powder. The average particle size of the B4C powder is less than 0.5 mu m, and the average particle size of the CoCrNi alloy powder is 80-150 mu m; b4C powder and CoCrNi alloy powder are mixed through an acoustic resonance mixing technology, and the surface of the CoCrNi alloy powder is coated with nanometer B4C powder. According to the method, the surface of CoCrNi alloy powder is evenly coated with small-particle-size B4C powder through the acoustic resonance mixing technology to prepare the CoCrNi-B4C composite powder, the optimal balance of strength and toughness is achieved, uniform powder feeding cladding is achieved, the surface of a to-be-cladded plate is cladded with the composite powder subsequently through rectangular light spot laser equipment, and therefore the composite powder is obtained. The large-area crack-free laser cladding high-hardness CoCrNi-B4C composite coating is obtained, the cladding efficiency is greatly improved, and the hardness of the coating exceeds 400 HV.

The application provides a preparation method of laser additive manufacturing crack-free Ni3Al-based high-temperature alloy, comprising the following steps: (1) uniformly mixing micron-sized Ni3Al-based high-temperature alloy powder and nano Hf ceramic particles, so that the nano Hf ceramic particles are uniformly wrapped on the surface of the micron-sized Ni3Al-based high-temperature alloy powder, to obtain a composite powder; (2) drying the composite powder; (3) layer-by-layer melt forming the composite powder by using a laser directional deposition device, to obtain the laser additive manufacturing crack-free Ni3Al-based high-temperature alloy. The application also provides the laser additive manufacturing crack-free Ni3Al-based high-temperature alloy prepared by the method. The preparation method of the laser additive manufacturing crack-free Ni3Al-based high-temperature alloy can prepare the crack-free Ni3Al-based high-temperature alloy by the laser additive manufacturing method, and is simple in preparation and low in cost.

This invention provides a high-hardness, crack-free flux-cored welding wire and its preparation method. The flux-cored welding wire includes an outer sheath and a flux core. By weight, the flux core comprises the following components: boron carbide 5.6-8.6 parts; 75% ferrosilicon 3.1-4.6 parts; electrolytic manganese 0.6-1.6 parts; 80% ferrovanadium 0.3-1.2 parts; nickel powder 0.3-1.0 parts; 68% high-carbon ferrochrome 67.5-94.5 parts; and iron powder 6-6.5 parts. The preparation method of the flux-cored welding wire is as follows: [The following components are listed:] boron carbide, 75% ferrosilicon, electrolytic manganese, 80% ferrovanadium... Ferrovanadium, nickel powder, 68% high-carbon ferrochrome, and iron powder are added sequentially to a dryer and dried for 2-3 hours. The mixture is then thoroughly mixed using a three-dimensional motion mixer and placed in an insulated box for later use. The outer sheath is placed on a forming machine, which rolls the outer steel strip into a U-shaped groove. Flux-cored powder is added to the U-shaped groove, and the forming machine closes and pulls the groove to obtain the flux-cored welding wire. The flux-cored welding wire of this invention features high hardness, no cracks, high temperature resistance, and corrosion resistance. Furthermore, the low production cost of the flux-cored welding wire facilitates industrial production.

The invention relates to a nuclear power plant main pipeline damage tolerance establishment method. The method comprises the following steps: S1, determining the critical crack size of the main pipeline of the nuclear power plant at the end of the life; and S2, performing finite element calculation based on the established finite element model of the crack-free structure of the main pipeline so as to obtain stress distribution of the crack-free structure under each load working condition. S3, according to the initial crack size and the finite element calculation result, stress intensity factor calculation, transient pairing, elastic-plastic correction and fatigue crack propagation calculation are conducted in sequence, and the life end crack size of the main pipeline is obtained. And S4, when it is judged that the life end crack size of the main pipeline is smaller than the critical crack size, the step S3 is executed again to conduct iterative calculation on the initial crack size. And when the final crack size of the service life of the main pipeline is judged to be greater than the critical crack size, taking the initial crack size updated by the last iteration as the structural damage tolerance. The nuclear power pipeline defect evaluation period can be shortened, and the evaluation efficiency is improved.

The invention relates to the technical field of semiconductor manufacturing, in particular to a high-yield and crack-free temporary bonding method for laser lift-off of a Mini / MicroLED COW whole-surface chip structure. According to the method, a composite membrane material composed of double-sided acrylic UV viscosity-reducing glue and a PET rigid base material is adopted. And high pressure is applied in a vacuum environment to complete bonding of the temporary substrate and the COW, so that large-area and high-density embedding of the acrylic acid adhesive layer and the surface structure of the chip is realized. And carrying out UV exposure to promote the phase change of the acrylic adhesive layer, and curing the acrylic adhesive layer from an initial soft viscoelastic state to a high-modulus hard acrylic support structure. The hard supporting surface and the vacuum embedded structure act together, so that excellent internal stress resistance is provided, and cracks in laser lift-off and subsequent processes are effectively prevented. Meanwhile, after the cured structure is subjected to subsequent permanent bonding, the visbreaking layer can be activated through simple UV irradiation, and residue-free and easy-to-separate de-bonding of the temporary substrate and the PET film material is realized.

The application relates to a preparation method of an aluminum-based composite material plate. After sintering and forging, an aluminum-based composite material powder blank with a length-width ratio of 1.5-2 and a thickness of 70mm-110mm is pressed three times to prepare an aluminum-based composite material plate with a length-width ratio of 9-12 and a thickness of 10mm-35mm. The sintered blank is densified under small deformation through the first pressing, the sintered blank which has been densified is deformed in a large size under low pressure through the second pressing, the sintered blank is filled under low pressure through the third pressing, near-net-shape forming is realized, and thus the aluminum-based composite material plate without circumferential cracks and with consistent internal density is obtained.

The application discloses a method for eliminating thermal cracks in nickel-based alloy additive repair, which comprises the following steps: firstly, quantitatively analyzing elements contained in the nickel-based alloy, and simulating a solidification curve based on thermodynamics according to the elements; secondly, obtaining a CSI-fs curve based on the solidification curve; thirdly, designing a heat treatment system through thermodynamic simulation, and performing composition homogenization treatment on the nickel-based alloy; and finally, performing electron beam additive repair. Results show that the nickel-based alloy treated by the method does not produce cracks during the additive repair, i.e., the thermal cracks are eliminated, the connection is stable, and the crack-free additive repair is successfully realized.

This invention discloses a rapid generation method for rectangular disks suitable for structured meshes. This method simplifies crack propagation calculations of the disk into a parametric fracture mechanics model, enabling the calculation of stress intensity factor and crack propagation life. Specifically, finite element modeling is employed to extract the geometric boundaries of the disk and its partitions, considering the influence of geometric dimensions and boundary effects on crack propagation. Based on coordinate system transformation, using the crack initiation point and stress gradient direction as a reference, the rectangular plate can be accurately located, improving modeling efficiency. This invention simplifies the crack propagation plane into a finite-size rectangular plate. Based on boundary intersection point capture, it achieves high-fidelity equivalence between the rectangular plate model and the actual complex contour of the disk, reducing calculation errors in the boundary region using traditional methods. Furthermore, by extracting the crack-free stress distribution along the crack propagation direction on the rectangular plate, the stress intensity factor at the crack tip and crack propagation life can be calculated using the weighted function method.

The application belongs to the technical field of metal-organic framework material and gas separation membrane preparation, and particularly relates to a preparation method of a halogen-modified high-porosity self-supporting MOF glass membrane, which comprises the following steps: firstly, a high-porosity vitrifiable MOF material with imidazole as a first ligand and a series of halogen benzimidazoles as second ligands is synthesized by a low-temperature solvothermal method; then, halogen MOF powder with high-temperature melting characteristics is pressed into a dense and crack-free disc-shaped precursor by a mechanical cold-pressing method; and finally, the disc-shaped precursor is subjected to high-temperature melting heat treatment under an inert atmosphere, and the heating temperature can ensure that the MOF particles are fully melted and flow, so that the interstitial gaps, defects and grain boundaries among the original particles in the thin sheet are completely eliminated. The application aims to prepare a defect-free, high-selectivity and high-flux MOF glass membrane, and solves the problems of low porosity and limited gas separation performance of the existing MOF glass membrane.

This invention discloses a method for preparing high-elongation bars for cold forging, belonging to the field of aluminum alloy preparation technology. Through optimization of composition and process, the prepared bars possess high purity, uniform and fine equiaxed grain structure, and excellent plasticity, with significantly improved elongation. This meets the stringent requirements of cold forging for high material plasticity, resulting in a bright, crack-free surface and uniform grains after cold forging, overcoming problems such as oxide scale, coarse grains, and poor dimensional accuracy caused by hot forging. Furthermore, the introduction of modified talc and sodium nitrate as refining agents further promotes uniform microstructure, achieving high elongation and excellent cold forging performance.

The invention relates to a ceramic bottle crack detection method based on machine learning open set recognition, which comprises the following steps: detecting the passing of a ceramic bottle on a conveyor belt through a photoelectric sensor, and when the passing is detected, controlling a knocking hammer to knock the bottle and collecting a sound signal through a microphone; intercepting, filtering and preprocessing the sound signal, and extracting a plurality of features; performing crack open set identification in two steps, adopting an improved MFCC to train a dichotomous support vector machine to detect whether a bottle has a crack or not, respectively training five single-class support vector machines by using all features to serve as a basic model of a first layer of a stacking model, and adopting a local outlier factor as a meta-model of a second layer of the stacking model to identify the crack open set of the bottle; the stacking model is used for detecting whether abnormal noise exists or not; and 4, according to an open set identification result, if abnormal noise exists during detection, re-detection is carried out, and otherwise, the ceramic bottles with cracks are removed according to a binary classification result. The open set recognition method is adopted to remove the influence of abnormal noise on the detection result, and the detection precision is high.

The invention provides a preparation method of a multi-field coupling laser cladding FeCoCrNiMo high-entropy alloy coating, and aims to solve the problems of chloride ion corrosion and cavitation corrosion of marine propellers and rudder shafts in a marine environment. The preparation method comprises the steps of base material pretreatment, composite powder preparation, multi-field coupling laser cladding, post-treatment and the like. According to the method, a certain proportion of the composite slag former (CaO-Al2O3-MgO-CaF2-Y2O3) is added into the FeCoCrNiMo high-entropy alloy powder, and in the laser cladding process, an ultrasonic field and / or a magnetic field are / is adopted for assistance, so that the uniformity, compactness and corrosion resistance of the high-entropy alloy coating are remarkably improved. The prepared FeCoCrNiMo high-entropy alloy coating is good in bonding performance with a base material, has no defects such as cracks and holes, has excellent chloride ion corrosion resistance and cavitation corrosion resistance, and can meet the high protection requirement in the marine environment.

The application provides a three-step forming cold extrusion process method and a forming die for a firing pin, which comprises the following steps: pre-cutting, pre-cutting two adjacent part material sheets apart by using a pre-cutting punch and a pre-cutting die; pre-forming, pressing the required material of the part into a material storage hole by using a pre-forming punch and a pre-forming die, and extruding the excess material into the extrusion area of the next working step; rough forming, rough forming of the part is completed by using a rough forming punch and a rough forming die; trimming the excess material, the material extruded in the pre-forming and rough forming steps is cut off by using a trimming punch and a trimming die, so that the edge of the material is ensured to be free of cracks; fine forming, fine forming of the steel strip is performed by using a fine forming punch and a fine forming die. The three-step forming cold extrusion process method breaks through the bottleneck in the cold extrusion forming process of small high-strength, high-precision and special-shaped metal parts, significantly improves the forming efficiency and improves the forming quality. The forming quality of the firing pin obtained by the forming die is high.

The present invention relates to a process for producing a steel alloy part, which includes providing a steel alloy powder mixture containing SiC, forming the part from the powder mixture using an additive manufacturing technique, and subjecting the formed part to a thermal treatment for a duration of 1 to 150 minutes at a temperature ranging from 600°C to 750°C. This process is particularly suitable for creating parts with enhanced properties, such as cutting tools, bearings, punches, and gears, which can be crack-free and defect-free. The additive manufacturing technique is Laser Powder Bed Fusion. The steel alloy powder mixture composition and preparation method are also detailed, along with the characteristics of the resulting steel alloy part, which comprises a bainitic ferrite matrix with graphite particles and carbides distributed therein.

The invention discloses a metallurgical-defect-free high-temperature wear-resistant cobalt-based alloy coating and a preparation method and application thereof.The preparation method comprises the following steps that (1) Fe powder, Co powder, Cr powder, Ti powder, Mo powder and Ni powder are accurately weighed according to the stoichiometric equation Co57Fe5Ni5Cr25Ti5Mo3, and (2) the weighed powder is put into a ball milling tank to be subjected to ball milling, so that the powder is evenly mixed, and then drying, sieving and drying storage are conducted; (3) 5NiCrMo hot work die steel is selected as a base material, a sand mill is used for polishing the surface of the base material so as to remove surface oxide skin until a bright surface is exposed, and oil stains on the surface are removed; and (4) a laser directional energy deposition method in laser additive manufacturing is used for continuously depositing the crack-free cobalt-based alloy coating with high temperature resistance, wear resistance and no cracks one by one. The high-temperature wear-resistant alloy shows excellent wear resistance at a high temperature, the alloy has a shallower wear depth and a narrower grinding crack width at the high temperature, and the wear rate at the high temperature of 800 DEG C is reduced from 2.171 * 10 <-4 > mm < 3 > / N.m of a 5CrNiMo base material to 2.45 * 10 < 6 > mm < 3 > / N.m of a coating.

The invention discloses a super duplex stainless steel S32750 medium plate and a hot rolling method thereof.The medium plate comprises, by mass, less than or equal to 0.03% of C, less than or equal to 0.8% of Si, less than or equal to 1.2% of Mn, less than or equal to 0.035% of P, less than or equal to 0.020% of S, 24.0-26.0% of Cr, 6.0-8.0% of Ni, 0.24-0.32% of N, 3.0-5.0% of Mo, less than or equal to 0.5% of Cu and the balance Fe. The method comprises the steps that a continuous casting blank is heated in a multi-step temperature difference mode, the temperature of a first temperature step is controlled to range from 400 DEG C to 500 DEG C, and heat preservation is conducted for 100-130 min; raising the temperature to a second temperature step in a linear temperature raising manner, controlling the temperature of the second temperature step to be 1000-1100 DEG C, and keeping the temperature for 170-190 minutes; raising the temperature to a third temperature step in a linear temperature raising manner, controlling the temperature of the third temperature step to be 1250-1300 DEG C, and keeping the temperature for 170-190 minutes; rolling is conducted, the heated continuous casting billet is subjected to multi-pass rolling in a broadening longitudinal rolling mode, the finish rolling temperature is controlled to be 1000 DEG C or above, and ACC rapid cooling is adopted after rolling, and by means of the method, a plate with the thickness larger than or equal to 100 mm and the width larger than or equal to 2000 mm can be prepared for rolling, so that the plate in the hot rolling state is free of sigma phase, and the surface and the edge are free of cracks.

A photocurable sol-gel composition for preparing a transparent and crack-free glass body, wherein the composition comprises a silica sol-gel precursor, a photopolymerizable monomer, a transition metal precursor, an organic solvent, and water. Also disclosed are methods of making the photocurable sol-gel compositions and methods of making transparent and crack-free glass objects from the photocurable sol-gel compositions.

The invention discloses a cable tunnel flat spectrum detector, a crack measuring method and a storage medium, and relates to the technical field of tunnel cracks, and the cable tunnel flat spectrum detector comprises a flat spectrum detection module, a signal processing module, a data storage module, a data comparison and analysis module and a display. A plurality of standard crack test pieces with different crack depths or lengths and frequency spectrum characteristic information of crack-free standard test pieces are pre-stored in the data storage module; the signal processing module compares the reference spectrum of the crack-free standard test piece with the spectrum detected by the flat spectrum detection module, screens out a newly added characteristic peak and a frequency deviation peak as characteristic peaks to be detected, and calculates spectrum characteristic information; and the data comparison and analysis module is used for matching the current spectrum characteristic information with the spectrum characteristic information of the standard crack test piece in the crack parameter database to obtain crack parameters. Traditional cable tunnel detection depends on local ultrasonic flaw detection, hysteresis exists, and early-stage tiny cracks are difficult to find; in order to overcome the hysteresis, cracks are found in a full-time monitoring mode through a flat spectrum detection module.

The application discloses a method for improving the surface quality and performance of a laser cladding NiCrSiBC-WC composite coating, relates to the field of composite coating surface processing technology, and aims at solving the problem that the coating prepared through single laser cladding is prone to cracks. The method comprises the following steps: S1, pretreatment of a base material; S2, preparation of laser cladding powder; S3, laser cladding treatment; S4, temperature field auxiliary treatment; and S5, laser remelting composite temperature field auxiliary treatment. The laser remelting composite temperature field auxiliary technology can break the limitation of the WC material addition amount on the performance of the coating, and a low-WC-mass-fraction high-hardness crack-free NiCrSiBC-WC composite coating can be obtained through the technology. The structure compactness of the NiCrSiBC-WC coating is improved, and the surface hardness and bonding force of the coating are improved.

The invention provides a crack-free lithium niobate film based on a Si substrate and a growth method and application thereof, and belongs to the field of ferroelectric film growth methods. According to the crack-free lithium niobate thin film based on the Si substrate, the substrate is selected from a Si substrate, and a target material is selected from congruent lithium niobate ceramic doped with 2.0 mol%-5.0 mol% of erbium and congruent lithium niobate ceramic doped with 5.0 mol% of iron prepared by a solid-phase reaction method, or is selected from congruent lithium niobate crystal doped with 2.0 mol% of erbium and congruent lithium niobate crystal doped with 5.0 mol% of iron prepared by a Czochralski method, or is selected from congruent lithium niobate crystal doped with 5.0 mol% of erbium and congruent lithium niobate crystal doped with 5.0 mol% of iron prepared by a Czochralski method. The lithium niobate thin film shows a lithium niobate (006) characteristic diffraction peak and a lithium-deficient phase LiNb3O8 (-602) characteristic diffraction peak, the surface of the lithium niobate thin film is flat, smooth and crack-free, the problem of surface cracking of a Si-based lithium niobate thin film for a long time is solved, and the lithium niobate thin film can be used for preparing micro-cavities, electro-optical modulators, photoelectric detectors, super-surface micro-nano devices and the like and has wide application prospects. And a foundation is laid for manufacturing and researching an integrated device on a lithium niobate film sheet.

The invention belongs to the technical field of metal additive manufacturing, and discloses a method for inhibiting cracks of an additive manufacturing high-temperature alloy, which can achieve the effect of high density while realizing crack-free forming of a material. Specifically, cracks are inhibited in the high-temperature alloy additive manufacturing process through a method combining alloy component design optimization and forming process optimization, and the method is suitable for forming of high-temperature alloys of multiple additive manufacturing technologies such as selective laser melting and directional energy deposition.

This application discloses a processing apparatus and method for elliptical vibration flying cutter of complex optical surfaces. The processing apparatus includes an elliptical vibration mechanism and a flying cutter. The elliptical vibration mechanism is configured to be mounted on the spindle of a machining lathe, and the flying cutter is mounted on the elliptical vibration mechanism, with the flying cutter located outside the rotation axis of the spindle. The above-described processing apparatus and method can solve the problem of low processing efficiency in the current processing of complex surfaces such as free-form surfaces on brittle materials, where a small feed rate and depth of cut are required to obtain a crack-free surface.

This invention relates to a method for preparing a silicon nitride wear-resistant coating on the surface of a graphite part. The method involves coating the graphite part with polynitrosilane, followed by drying and subsequent decoking and high-temperature ceramization treatments. The process is precisely designed as a multi-stage heating decoking and high-temperature ceramization process. By strictly controlling the heating rate and holding time, the method avoids coating shrinkage and cracking caused by rapid heating, as well as resource waste and increased internal stress caused by excessively slow heating. Simultaneously, the decoking temperature is optimized to prevent excessive decomposition and escape of polynitrosilane or residual small molecules. This effectively solves the coating cracking problem caused by the difference in thermal expansion coefficients between graphite and silicon nitride, thereby obtaining a dense, uniform, and crack-free silicon nitride coating.

The invention discloses an SPS preparation method and application for sintering and connecting TZM and graphite by using titanium hydride powder in the field of connection of TZM / graphite dissimilar materials, and particularly relates to a TZM / graphite composite material obtained by performing sintering diffusion connection on the TZM and graphite dissimilar materials by using the titanium hydride powder as a middle layer material through an SPS technology. The method has the following advantages that the titanium hydride powder serves as an interlayer material, compared with existing used titanium powder or titanium foil, the titanium hydride powder is environmentally friendly and low in component content, the titanium hydride powder can release hydrogen and generate elemental titanium within the temperature range of 400-800 DEG C, oxidation of titanium can be reduced while a base metal oxide layer can be removed, interdiffusion and solid solution of interface Mo and Ti atoms are promoted, and the service life of the interface Mo and Ti is prolonged. And a good metallurgical bonding interface is formed through reaction with the graphite side, and the TZM / graphite composite material which is free of crack defects, high in interface bonding strength and good in durability is obtained.

The application provides a layered preparation method and system of a diamond heat sink sheet, and the method comprises the following steps: preparing a crystal direction anchoring microstructure on a growth surface of a substrate and a moment buffer layer on a non-growth surface; obtaining a first layer of diamond through crystal direction anchoring, and generating a reverse moment on the growth surface through the moment buffer layer; removing surface defects on the diamond surface to form an atomic level step; depositing a liquid metal on the atomic level step for stress release, and then removing the liquid metal; continuously growing a second layer of diamond, and accurately controlling the stress state of the second layer of diamond; and cooling to obtain a crack-free diamond heat sink sheet. Through the synergistic process design of the diamond layering construction and the reverse moment buffer, the application blocks the path of stress accumulation and crack initiation and expansion, effectively solves the cracking problem in the preparation process of the diamond heat sink sheet, balances the process feasibility and the product performance stability, greatly improves the yield and the structural integrity of the diamond heat sink sheet, and reduces the production cost.

The invention provides a permanent magnet crack detection method and a permanent magnet crack detection device, which are characterized in that a pair of current probes are utilized to introduce stable direct current or alternating current into a permanent magnet to be detected, and one or more potential probes are utilized to measure potential differences of contact points of the probes and the permanent magnet relative to a reference end. By comparing the measured values of the to-be-measured permanent magnet and the crack-free standard permanent magnet which are the same in shape, size and material, whether current density distribution abnormity caused by cracks exists in the to-be-measured permanent magnet or not is judged, and then the crack degree of the to-be-measured permanent magnet is evaluated and screened. Compared with the existing machine vision, eddy current, ultrasonic and magnetic powder detection technologies, the method has the beneficial effects that the requirement on the surface smoothness of the permanent magnet is low, the detection depth is large, the permanent magnet is not easily interfered by the residual magnetic flux density of the permanent magnet, and the detection efficiency is high.