57 results about "Abnormal grain growth" patented technology

The invention discloses a heat treatment method of an iron-nickel-based high-temperature alloy, which solves the contradiction between stress relief annealing and performance maintenance through four-step temperature coordinated regulation and control: in the first step, MC type carbide is dissolved through solid solution, segregation is eliminated, and excessive growth of crystal grains is avoided; in the second step, roughening of M23C6 type carbides is inhibited through solid solution, and formation of fine and uniform carbides on grain boundaries is promoted so as to strengthen the grain boundaries; in the third step, the residual stress is reduced through stress relief annealing, and meanwhile grain boundary carbide growth and abnormal grain growth are avoided; and in the fourth step, uniform and stable precipitation of a gamma'phase is promoted through aging, the nanometer size and the high volume fraction are maintained, and coarsening is avoided. Through precise temperature connection, the residual stress is effectively reduced, grain growth, structure nonuniformity or performance degradation caused by traditional annealing are avoided, and finally the application requirement of the superhigh-temperature steam environment at the temperature of 650 DEG C or above is met on the premise that the mechanical property and the corrosion resistance are guaranteed.

The invention provides a method for inhibiting abnormal grain growth of a 7xxx series aluminum alloy friction stir welding joint, which comprises the following steps: step 1), performing wire filling welding treatment on a to-be-welded aluminum alloy part to obtain a welding part; wherein the welding flux is an aluminum alloy containing a scandium element; (2) the welding part is subjected to friction stir welding treatment, and a friction stir welding head is obtained; and (3) post-treatment is conducted on the friction stir welding head. Welding materials used are characterized in that a certain amount of scandium is added, then differential friction stir welding treatment is carried out, the differential friction stir welding treatment is carried out by independently regulating and controlling the rotating speed of a shaft shoulder and the rotating speed of a stirring needle, and on the premise that the rotating speed of the stirring needle is greatly increased to improve material flowing, the welding efficiency is greatly improved. The low shaft shoulder rotating speed is applied to eliminate overheating, defects are avoided, pinning particles are dispersed, and the effect of completely inhibiting growth of abnormal crystal grains is achieved.

The application discloses a method for preparing high-purity superfine tungsten powder by series impurity removal and microwave calcination, and relates to the technical field of refractory metal powder metallurgy. The method uses 99% and below industrial-grade ammonium paratungstate as raw material, and sequentially performs pyrolysis, two-stage physical purification, ultrasonic synergic acidolysis deep purification, microwave uniform calcination and sectional reduction. Firstly, the ammonia solution-evaporation crystallization method and the chemical precipitation method are connected in series to realize deep impurity removal, and the chemical precipitation method is used to directly obtain a nano tungsten oxide precursor, so that the morphology of the tungsten powder is guaranteed for subsequent reduction; secondly, the microwave calcination process is introduced to realize fast and green and environment-friendly uniform heating, and the hard agglomeration of the precursor is significantly reduced; finally, the sectional reduction method is adopted to effectively block the CVT effect in the reduction process, and abnormal grain growth is avoided. The method solves the problems of incomplete purification, sintering agglomeration of the precursor during reduction and out-of-control reduction particle size in the prior art, and the prepared tungsten powder has high purity and small average particle size.

A method is provided for forming a large metallic component using a friction stir welded blank. A first and second metallic plate are positioned in an abutting arrangement with corresponding faying surfaces. A backing plate is attached across the abutment. The plates are friction stir welded along the faying surfaces, the friction stir weld including a weld root that terminates in the backing plate. After welding, the backing plate is removed, including the weld root, to create a welded blank. The blank is then formed into a desired component shape, heat treated and aged to produce the final large metallic component. The resulting friction stir weld has a stable microstructure with minimal or no abnormal grain growth during high-temperature forming, heat treatment, or aging.

The invention relates to the technical field of special ceramic product preparation, and discloses a zirconium oxide secondary densification process in special ceramic part processing, which comprises the following steps: a vacuum pressure infiltration step: driving an aluminosilicate-based precursor to infiltrate into microcracks on the surface layer of a zirconium oxide workpiece by using pressure difference; a phase change interval critical rate heating step: controlling the heating rate to match the volume shrinkage of the zirconium oxide from monoclinic phase to tetragonal phase transformation, and generating a grain boundary gap to drive the precursor to deeply permeate; an in-situ reaction densification step: inducing the precursor in-situ reaction at high temperature to generate an aluminosilicate solid phase and filling crystal boundary trident points; according to the method, through a phase change coupling permeation mechanism, reactive healing of microcracks is achieved on the premise that abnormal growth of crystal grains is not caused, and the fracture toughness and the anti-aging performance of the zirconia ceramic are improved.

This invention discloses a high-boron Y–Ce–Co co-substituted nanocrystalline material and its preparation method. The general chemical formula of the nanocrystalline material, expressed as a percentage by mass, is: [RE x (Y y Ce 1‑y ) 1‑x ] z Fe 100‑z‑u‑v‑w Co u M v B w The composition is defined as follows: 0 ≤ x ≤ 0.9, 0.05 ≤ y ≤ 0.9, 25 ≤ z ≤ 35, 5 ≤ u ≤ 50, 0 ≤ v ≤ 3, 1.7 ≤ w ≤ 3. This invention utilizes Y–Ce–Co co-substitution to synergistically regulate the lattice occupancy, elemental valence states, and magnetic exchange interactions of the main phase, significantly improving the temperature stability of the Ce-rich system. Addressing the issues of abnormal grain growth and excessive Laves phase precipitation caused by Co introduction, increasing the mass percentage of B significantly enhances the alloy's amorphous forming ability, refines the main phase grains, and suppresses the formation of harmful second phases. Based on this compositional design, a low-linear-velocity melt rapid quenching process (12 to 18 m / s) can directly prepare materials with uniform nanocrystalline structures without subsequent crystallization annealing, achieving high coercivity and high temperature resistance while significantly reducing raw material costs.

The invention discloses a management control method for abnormal grain growth of an electronic aluminum foil, and the method comprises the steps: building an intermediate annealing-dislocation density attenuation model, a cold rolling-dislocation density proliferation model and an abnormal grain growth probability model through detecting the dislocation density in cold rolling and intermediate annealing processes; the model is used for calculating the real-time dislocation density and pre-judging the abnormal grain growth probability, the cold rolling machining amount and intermediate annealing process adjustment can be guided, the limitation brought by traditional tentative process adjustment is solved, production is promoted to be converted into data driving, and the method is suitable for medium-high voltage electronic aluminum foil production.

This invention relates to the field of special ceramics preparation technology, and discloses a process for preparing high thermal conductivity ceramic materials for high-nickel ternary cathode sintering, including: preparing magnesium aluminum spinel green blanks containing magnesium oxide, yttrium oxide and titanium oxide composite additives; performing cyclic variable oxygen pressure sintering at 1420℃ to 1480℃, controlling the furnace atmosphere to periodically switch between the first and second oxygen partial pressure states. This invention utilizes the oxygen potential difference to drive the grain boundary liquid phase to alternate between low viscosity wetting and high viscosity pinning characteristics, eliminating the rheological quiescent zone at the end of sintering, effectively suppressing abnormal grain growth while ensuring high material density, and improving the thermal conductivity and lithium erosion resistance of the ceramic sagger.

The invention relates to the technical field of alloy materials, in particular to a hard alloy material for high-speed cutting and a preparation method thereof. The material comprises a hard phase and a binding phase, wherein the hard phase is tungsten carbide particles distributed in a bimodal mode, and a gradient diffusion layer is formed on the surface of the hard phase through a shell layer containing vanadium and chromium on the interface; and the binding phase is a multi-component alloy containing cobalt, chromium, iron, nickel, molybdenum and ruthenium. The preparation method comprises the following steps: carrying out dopamine pretreatment on tungsten carbide, carrying out pyrolysis on tungsten carbide and a metal organic precursor to form a shell layer, preparing binding phase powder, mixing and granulating, forming and dewaxing, sintering and carrying out hot isostatic pressing treatment. Abnormal growth of crystal grains is inhibited through the core-shell structure, high-temperature stability and interface bonding are enhanced through the multi-element binding phase, the material has high hardness, high toughness and thermal shock resistance at the same time, the wear resistance of a tool in high-speed cutting is remarkably improved, and the service life of the tool in high-speed cutting is remarkably prolonged.

The invention relates to the technical field of silicon carbide material preparation, in particular to a reaction sintering method of a large-size silicon carbide material, which comprises the steps of raw material preparation, slip casting and reaction sintering, the gradient heating and cooling process in the reactive sintering process is divided into five stages: a low-temperature stage, a medium-temperature stage, a high-temperature stage, a cooling stage and a tempering stage. Through the synergistic effect of staged gradient heating, tempering treatment after sintering, high-pressure argon pressure sintering and silicon nitride nano powder grain boundary regulation and control, the technical problems of cracking, non-uniform density and abnormal grain growth in the sintering process of the large-size silicon carbide material are effectively solved.

The invention relates to the technical field of heat treatment of steel and iron materials, and discloses a structure-performance cooperative control production method of a seamless steel tube for a 40Cr hollow anchor rod, which comprises the following steps: performing hot piercing on round steel to prepare a hollow tube blank; spheroidizing annealing is conducted on the hollow pipe blank; cold finish rolling is carried out after acid pickling, the total true strain is set, and the lt is calculated through a pass distribution coefficient according to a formula; 111gt, 111gt; a crystal orientation texture index; recrystallization annealing is conducted, the recrystallization annealing temperature is determined according to the spheroidizing annealing temperature in combination with the collaborative relational expression, and the heat preservation time is determined according to the total true strain in combination with the collaborative relational expression; and straightening and sizing cutting are performed to obtain a finished steel pipe. Aiming at the defect of mechanical property fluctuation caused by existing parameter isolation, a multi-process quantitative constraint model is established, and growth of abnormal grains is effectively inhibited through matching of a thermodynamic state and deformation dynamic compensation, so that a high-index oriented texture is formed in a pipe body, batch mechanical property fluctuation is reduced, and product consistency is improved.

The invention belongs to the field of metal materials, and provides a high-strength plastic magnesium alloy based on isothermal annealing under constant stress and a preparation method. The magnesium alloy is prepared from the following components in percentage by mass: 1.2 to 1.5 percent of Al, 0.2 to 0.4 percent of Ca, 0.5 to 0.8 percent of Gd, less than or equal to 0.05 percent of inevitable impurities and the balance of magnesium. The preparation method of the high-strength plastic magnesium alloy comprises the steps of casting, stepped homogenization treatment, hot extrusion, high-temperature solid solution treatment, rolling and isothermal annealing treatment under constant stress. Rapid recrystallization and texture weakening are achieved under the low-temperature and short-time conditions, a large number of high-thermal-stability nano Al-Gd and Al-Ca phases exist in the alloy, the strength is improved, meanwhile, the defects of uneven tissue, abnormal grain growth and the like caused by traditional high-temperature heat treatment are overcome, and the heat treatment cost is remarkably reduced. The finally obtained alloy has a weak texture which deflects in the rolling direction RD and the transverse direction TD, and the peak strength is smaller than or equal to 6.8 mrd. The recrystallization area fraction is larger than or equal to 63.8%, the average grain size is smaller than or equal to 7.7 micrometers, the tensile strength is larger than or equal to 234.6 MPa, the ductility is larger than or equal to 17.9%, and excellent strength and plasticity matching is achieved.

The application provides an aluminum alloy component and a hybrid manufacturing method, relates to the technical field of hybrid manufacturing, and comprises the following steps: solid-phase additive manufacturing is performed on an aluminum alloy raw material to obtain an additive component; plastic processing treatment is performed on the additive component to obtain the additive component after plastic processing treatment; and heat treatment is performed on the additive component after plastic processing treatment to obtain an aluminum alloy component; in the structure of the solid-phase additive component of the aluminum alloy, the grain size is small, and more grain boundary energy is stored; during solid solution heat treatment, abnormal grain growth is prone to occurring, mm-level grains appear in the structure, and the tensile property is harmed; strain energy is introduced into the additive structure through plastic processing treatment, so that recrystallization nucleation and growth are promoted during heat treatment, and the effect of limiting abnormal grain growth is achieved.

The invention provides a Fe-Mn-Al-Ni-based superelastic alloy and a preparation method thereof, and belongs to the technical field of iron-based superelastic alloys. The Co element is added, so that a gamma phase with high number density can be formed, after the gamma phase is heated to an alpha single-phase region, a sub-crystal structure with wide orientation distribution, high average orientation difference and number density is formed in alpha-phase crystal grains, abnormal growth of individual sub-crystals is caused, other sub-crystals in mother crystal grains are completely consumed by the sub-crystals which grow abnormally, and therefore the performance of the alloy is improved. A huge free energy gradient is formed between mother crystal grains and surrounding normal crystal grains with sub-crystals, so that a greater driving force is provided for the growth of abnormal crystal grains, and the growth process of the abnormal crystal grains is greatly shortened; by adding the Mo element, the width of the sub-grain low-density area can be increased, the time that the grain boundary crosses the sub-grain low-density area is prolonged, and therefore the number of abnormal grains is reduced, and the final size of the grains is increased.

This invention belongs to the field of heat exchanger technology, specifically relating to a heat treatment enhancement method and system for heat exchangers. The invention employs a three-stage magnetic field design, applying specific types, parameters, and directions of magnetic fields at three key stages: 200-400℃, 600-900℃, and 900-1100℃. In the low-temperature stage, an alternating magnetic field at a 30-60° angle to the heat transfer path is used to uniformly eliminate residual stress. In the medium-temperature stage, a high-energy pulsed strong magnetic field drives dislocation movement and grain boundary migration. In the high-temperature stage, a uniformly rotating magnetic field achieves uniform distribution of the temperature and electromagnetic fields across the entire domain. This solves the problems of stress concentration, uneven recrystallization, and abnormal grain growth caused by the single direction of the magnetic field in traditional processes. It significantly optimizes the microstructure of the substrate and effectively improves the uniformity of the austenite structure and the grain refinement effect.

The invention belongs to the field of ceramic cutting tool materials, and particularly relates to a complex-phase Ti (C, N)-based ceramic material with a double-solid-solution microstructure and a preparation method of the complex-phase Ti (C, N)-based ceramic material. The prepared ceramic material is prepared by taking Ti (C, N) as a matrix and adding ZrC, NbC and Mo2C as reinforcing phases through spark plasma sintering. The addition of ZrC induces the formation of a (Ti, Zr, Nb) (C, N) second solid solution phase rich in Zr elements; the dispersed distribution of the (Ti, Zr, Nb) (C, N) second solid solution phase in the crystal and at the crystal boundary can effectively pinning the crystal boundary, inhibit the abnormal growth of the crystal grains in the sintering process, realize the spanning from a single solid solution to the multiphase ceramic, obviously improve the bending strength, hardness and wear resistance of the Ti (C, N)-based ceramic material, and greatly improve the service life of the ceramic material. And irreplaceable importance is shown in the fields of cutter materials, precision machining and the like.

The invention relates to a preparation method of a high-thermal-conductivity aluminum alloy for an energy storage battery pack, and belongs to the technical field of aluminum alloy production. The invention discloses a preparation method of a high-thermal-conductivity aluminum alloy for an energy storage battery pack. The preparation method comprises a component adjustment step, after component adjustment is completed, second-stage solid solution is carried out; aging treatment is carried out after the second-stage solid solution is completed; the component adjusting step specifically comprises the following steps: when the aluminum alloy is smelted, the temperature of a melt is 730-750 DEG C, the content of Fe is less than or equal to 0.15 wt%, the content of Cr reaches 0.05-0.10 wt%, and the content of rare earth reaches 0.05-0.15 wt%; according to the two-stage solid solution process, by accurately controlling the temperature and the time, sufficient solid solution of a second phase is guaranteed, meanwhile, abnormal growth of crystal grains and composition segregation are avoided, the purity and the structure uniformity of a matrix are improved, meanwhile, the process period is shortened, and the production efficiency is improved.

The utility model relates to the field of metal material machining and forming, in particular to an aluminum alloy section machining system which comprises a feeding assembly, a first heater, an extrusion forming assembly, a second heater and a cooling assembly. Aluminum alloy casting bars are provided for the whole machining system through the feeding assembly; the first heater comprises a first heating cavity, and the aluminum alloy casting bar is heated through the first heating cavity; the extrusion forming assembly is used for carrying out extrusion forming on the heated aluminum alloy casting bar to obtain a tubular blank; the second heater comprises a second heating cavity, and the tubular blank is heated through the second heating cavity; and the cooling assembly is used for cooling the heated tubular blank. The method is reasonable in layout, composition segregation and abnormal growth of crystal grains in the welding line of the seamed pipe can be eliminated, the defects of cracks and slag inclusion occurring during welding of the aluminum alloy seamed pipe are reduced, and the service life of a product is prolonged.

The application relates to a high-strength quartz sand ceramic material and a preparation method and application thereof. A multi-scale reinforcing network is constructed by gradient matching of quartz fibers and silicon carbide fibers, grain boundary sliding is inhibited, nano-scale micropores are formed on the fiber surfaces through HF acid etching, and the interface shear strength is improved by combining with a silane coupling agent bridge. In addition, the composite powder of Al2O3 and ZrO2 can inhibit abnormal grain growth in a sintering process through stage gradient sintering, that is, first stage degumming, second stage nucleation and third stage densification. Nano-crystalline grains are twisted through high-density dislocations and are pinned through a grain boundary pinning effect, so that the grain boundary sliding resistance is improved by 3 times. Meanwhile, Si-O-Al bonds are formed between excessive Al2O3 and modified fibers, which is beneficial to reducing the interface thermal resistance, improving the heat resistance of the material and avoiding thermal stress concentration.

The present application relates to the technical field of electronic information functional ceramic materials and electronic devices, and particularly relates to a method for forming dielectric ceramic by microwave rapid annealing treatment, which comprises the following steps: (1) sample pretreatment, (2) microwave annealing, (3) cooling and discharging. The present application breaks through the limitation of heat damage caused by traditional process, and realizes the repair of non-intrinsic defects and intrinsic defects in the ceramic body by high-power microwave second-level transient annealing under the premise of completely maintaining the original grain size, crystal structure and phase composition of the ceramic, thereby fundamentally avoiding the problems of abnormal grain growth and volatilization of low-melting-point components, and realizing the lossless and rapid repair of defects of the formed dielectric ceramic. The processing period of traditional annealing lasting for several hours is shortened to 1-10 s, the process time is greatly shortened, and the quality factor Qxf of the dielectric ceramic after treatment is improved by 30%-100% in the terahertz band, and the quality factor Qxf is improved by 30%-60% in the microwave band.

The invention relates to a preparation method of Al2O3-coated TiB2 multiphase powder, TiO2 powder, Na2B4O7 and Al powder are taken as raw materials, a slow-release controllable aluminothermic reduction reaction is realized by accurately controlling a heating program, and the Al2O3-coated TiB2 multiphase powder with uniform particle size distribution and a tight coating structure is prepared by in-situ reaction at a low temperature of 1000-1300 DEG C; and carrying out low-temperature rapid sintering on the complex-phase powder through spark plasma sintering, so as to obtain the TiB2-Al2O3 complex-phase ceramic. According to the preparation method disclosed by the invention, through raw material innovation and three-section reaction path design, a milder slow-release controllable aluminothermic reduction reaction is realized, so that the nucleation and growth processes of Al2O3 and TiB2 can be accurately regulated and controlled, and the complex-phase powder with uniform particle size distribution and a unique coating structure is obtained; the multiphase powder can effectively inhibit abnormal growth of crystal grains and promote densification, so that multiphase ceramics with excellent mechanical properties can be obtained at a relatively low sintering temperature, and the multiphase powder has wide application prospects in the fields of flame nozzles of aerospace crafts, military bulletproof materials, cutting tools and the like.

The application belongs to the field of ceramic cutter material, and particularly relates to a dual solid solution microstructure composite Ti(C, N) based ceramic material and a preparation method. The ceramic material prepared by the application is prepared by adding ZrC, NbC and Mo2C as reinforcing phases by using discharge plasma sintering, with Ti(C, N) as a matrix. The addition of ZrC induces the formation of a Zr element-rich (Ti, Zr, Nb)(C, N) second solid solution phase; the dispersion distribution of the (Ti, Zr, Nb)(C, N) second solid solution phase at the intracrystalline and grain boundary can effectively pin the grain boundary, inhibit the abnormal grain growth in the sintering process, realize the leap from a single solid solution to a composite ceramic, and significantly improve the bending strength, hardness and wear resistance of the Ti(C, N) based ceramic material, which exhibits irreplaceable importance in the fields of cutter material and precision machining.

The application discloses a kind of high-performance GH4738 alloy material and preparation method thereof, the grain size of the alloy material is 5~6.5 level, metallographic is uniform equiaxed crystal organization, and its composition is 18.0‑21.0wt%Cr, 12.0‑15.0wt%Co, 3.50‑5.00wt%Mo, 2.75‑3.25wt%Ti, 1.20‑1.60wt%Al and the balance of Ni.By the synergistic effect of cold drawing deformation and heat treatment recrystallization, the abnormal grain growth problem of GH4738 alloy after standard solid solution treatment is solved.The process not only stabilizes the grain size to 5~6.5 level, but also meets the high-temperature durability requirements in AMS5708 standard.Simultaneously, it has the advantages of low equipment cost, low energy consumption and high compatibility, providing high-performance material guarantee for aero-engine key components.

The application discloses a closed upsetting-extruding forming device and method, and relates to the field of forming devices.The closed upsetting-extruding forming device comprises a lower die assembly, a punch, a floating extruding cylinder and an upper die assembly; the lower die assembly and the upper die assembly are oppositely arranged at a first preset distance; the floating extruding cylinder is arranged between the upper die assembly and the lower die assembly; the punch is sealingly and slidably arranged in the lower die cavity and can slide along the lower die assembly to the inner cavity of the floating extruding cylinder; and the bottom end of the punch is used for extruding a blank. The punch is used for extruding the blank, the one-time integral closed upsetting-extruding forming of a formed part can be realized, and the multi-step forming process of the disc part and the shaft part of the formed part is combined; the integral closed upsetting-extruding forming extrudes the shaft part at the same time of the disc part upsetting forming in one forging fire, the critical small deformation zone of the disc-shaft transition zone is fundamentally eliminated, the abnormal grain growth defect of the disc-shaft transition zone is avoided, the material utilization rate is improved, and the uniform distribution of the strain field of the disc-shaft integrated turbine disc is realized.

The invention relates to the technical field of high-temperature alloy structure regulation and control, in particular to a method for achieving GH4080A ring piece rolling deformation grain uniformity and refinement through carbide precipitation. According to the method, carbides are introduced in the ring rolling process, intracrystalline carbides serve as non-shearing precipitated phases, dislocation movement can be hindered, and the carbides existing on grain boundaries have the effect of pinning the grain boundaries, so that migration of the grain boundaries in the ring rolling deformation process becomes more difficult, and the yield of the ring rolling deformation is improved. In the subsequent annealing treatment (static recrystallization) process, due to the fact that enough dislocation is accumulated in the carbide in the crystal and the dislocation is in a relatively uniform distribution table state, abnormal crystal grain growth in the static recrystallization process can be prevented, and then refined and uniform recrystallization crystal grains are obtained.

The invention relates to the technical field of metal material processing, and discloses a wear-resistant alloy grinding ball for refining grains through cooperation of multi-stage forging and pressing and second-phase pinning and a preparation method of the wear-resistant alloy grinding ball, and the wear-resistant alloy grinding ball is obtained through a dynamic recrystallization, second-phase pinning particle synergistic refining and crystal phase diagram oriented multi-stage forging and pressing treatment composite method. The forging and pressing ratio gradient matching is achieved, the forging and pressing ratio of preheating forging and pressing is 3.0-4.0, the forging and pressing ratio of main forging and pressing is larger than or equal to 5.7, the forging and pressing ratio of fine forging and pressing is 4.0-5.0, and abnormal grain growth caused by entering a 5-15% critical deformation degree interval is avoided; zener pinning is formed on the grain boundary through (Nb, Ti) (C, N) particles formed by Nb and Ti, and dynamic recrystallization nucleation and second phase resistance growth are cooperated, so that the grain size is stably kept at the level 7.0 or above; the crushing rate is reduced to 0.75-0.83 per mill from 1.45 per mill of the traditional grinding ball, the minimum wear rate is 11.97 mm / m, the impact energy is greater than or equal to 40J, and the high-frequency impact load of a mine can be borne.

The invention discloses a preparation method, a preparation device and application of a hard alloy, and the preparation method comprises the following steps: placing an alloy raw material in an insulating mold, and carrying out pulse direct current sintering while applying pressure to obtain the hard alloy, the alloy raw materials comprise a hard phase raw material and a binding phase raw material; the hard phase raw material comprises at least one of WC, Ti (C, N), TiC, TaC or NbC; the binding phase raw material comprises at least one of Co, Fe, Ni or high-entropy alloy. A pulse direct current sintering method is utilized, an insulating mold is used for limiting current to directly flow through a powder sample, the whole powder sample can rapidly reach a uniform temperature field through Joule heat, second-level sintering is achieved, abnormal grain growth and a gradient structure caused by local overheating are reduced, grain growth is restrained, densification is promoted, and the yield is increased. And the preparation of the high-density nanocrystalline / ultra-fine grain hard alloy is realized.

This invention relates to the field of silicon carbide refractory ceramic thin-walled tube preparation technology, specifically to a pressureless sintered silicon carbide refractory ceramic thin-walled tube and its preparation method. The ceramic tube has a wall thickness of 0.5-3 mm and a bulk density ≥3.05 g / cm³ after sintering. The main phase of this invention adopts a bimodal structure of fine and coarse powder. The fine powder fills the pores to increase density, while the coarse powder inhibits abnormal grain growth. Simultaneously, nano-SiO2 binder and Si3N4 particles are introduced to pin the grain boundaries. Through the stress transfer mechanism, the room temperature flexural strength and bulk density are increased. Furthermore, a ZrO2 / SiO2 composite interface layer is formed by high-temperature pre-oxidation of hemp fiber and lotus leaf stalk mixed fiber impregnated with ethyl silicate solution. Combined with high-speed eddy current vibration, the fiber volume fraction is increased and the dispersion is reduced. This reduces the microcrack propagation rate and flexural strength fluctuation rate of the thin-walled tube under thermal cycling conditions, improves the bonding strength between the fiber and the matrix, effectively inhibits the propagation of microcracks in the thin-walled structure, and enhances the strength of the thin-walled tube.

The application belongs to the field of microwave ferrite materials, and provides a garnet ferrite with high dielectric constant and high bending strength and a preparation method thereof, so as to solve the problems of abnormal grain growth and high porosity caused by excessive liquid phase in the sintering process of the existing high dielectric constant bismuth-substituted garnet ferrite, and the problem of low bending strength caused thereby. In the main phase system of the bismuth-containing microwave garnet ferrite, a proper amount of nano-SiO2 is introduced as a grain boundary regulator, which is conducive to forming a dense and uniform fine-grained microstructure and optimizing the ferromagnetic resonance line width; while maintaining the high dielectric constant endowed by the high polarization rate of bismuth ions, the fracture toughness and intrinsic strength of the ferrite are significantly improved by means of fine-grained strengthening mechanism, so that the bending strength of the ferrite is increased, thereby effectively solving the problems of micro-cracks and edge collapse easily occurring in the processing steps such as slicing, grinding and polishing of the high dielectric microwave substrate, and meeting the application requirements of miniaturization and high yield production of the microwave circulator and isolator.

This invention discloses an efficient magnetic domain refinement method for ultra-low loss oriented silicon steel, relating to the field of steel material technology. The method includes: raw material preparation; hot rolling and final rolling; multi-stage thermomechanical processing; controlled suppression phase formation; secondary re-junction and magnetic field-induced selective growth; surface microstructure fabrication; low-temperature domain refinement annealing and alternating magnetic field coupling; segmented cooling and quality inspection. This invention, through controlled nanoscale suppression phase engineering, forms a high-density and uniform nanoscale suppression phase within the matrix, serving as pinning sites for grain boundaries and subgrain boundaries. This controls grain boundary migration dynamics during high-temperature secondary re-junction, overcoming the problems of abnormal grain growth and microstructure instability caused by uneven distribution and large size dispersion of traditional suppression phases. This avoids the root cause of large magnetic domains, improves the controllability and repeatability of the secondary re-junction process, obtains a more uniform orientation grain size distribution, and reduces localized magnetic domain enlargement and iron loss fluctuations caused by uneven grain size.