49 results about "Severe plastic deformation" patented technology

The invention discloses a method for improving the oxidation resistance of nickel-based superalloy, and belongs to the technical field of metal material surface modification. Based on the high-energy transient effect of laser shock waves, the method mainly comprises the key steps of alloy surface pretreatment, laser shock peening process implementation, post-treatment and the like. Specifically, firstly, the surface of the nickel-based single crystal alloy is subjected to pretreatment such as polishing and cleaning, surface defects and pollutants are removed, and the treatment quality is guaranteed; then, according to the material characteristics and performance requirements of the nickel-based single crystal alloy, laser parameters such as laser energy, pulse width and light spot diameter are accurately set, and proper restraint layer and absorption layer materials are selected; then, high-energy pulse laser is utilized to irradiate the absorption layer, high-temperature and high-pressure plasma is induced to be generated, the plasma expands and explodes to generate strong shock waves, the shock waves act on the alloy surface, the surface material is subjected to severe plastic deformation, a residual compressive stress layer with the depth capable of reaching hundreds of micrometers is formed, meanwhile, surface grains are refined, and the microstructure is optimized; and after the strengthening treatment is completed, simple cleaning and performance detection post-treatment are carried out. Through laser shock strengthening, a special organization structure with high density and low defect density is formed on the surface of the nickel-based single crystal alloy, diffusion and invasion of oxygen atoms are effectively hindered, and the oxidation resistance of the alloy is remarkably improved. According to the method, the controllability of technological parameters is high, the strengthening effect can be accurately regulated and controlled, the treatment process is free of pollution and high in efficiency, the obtained strengthened nickel-based single crystal alloy can be widely applied to the fields such as aerospace engine hot end parts and nuclear energy equipment which have strict requirements for high-temperature oxidation resistance, the reliability of related parts is greatly improved, and the service life of the related parts is greatly prolonged.

The invention discloses a preparation method of a high-strength and high-conductivity aluminum alloy profile, which comprises the following steps: 1) carrying out solution treatment on an aluminum alloy raw material to obtain a supersaturated solid solution; (2) the supersaturated solid solution is subjected to low-temperature extrusion treatment, and the aluminum alloy profile is obtained; and thirdly, the aluminum alloy profile is heated, and the high-strength and high-conductivity aluminum alloy profile is obtained. According to the method, hot extrusion is replaced by low-temperature extrusion, so that the aluminum alloy profile generates a remarkable cold hardening effect, the strength of the alloy is greatly improved, meanwhile, severe plastic deformation at the extrusion temperature generates a large number of intragranular dislocations, Mg and Si elements are promoted to be quickly and fully dispersed and separated out, the alloy generates a precipitation strengthening effect, and the conductivity is improved.

The invention discloses a near-net forming friction welding method for a dissimilar metal stud based on a middle layer, which comprises the following steps of: pre-processing a similar T-shaped boss with a thread or a circular truncated cone-shaped boss without a thread section on the end surface of a workpiece with high hardness, and pre-processing a corresponding similar T-shaped groove or a circular truncated cone-shaped groove on the end surface of a workpiece with low hardness; and before welding, middle-layer alloy is placed at the upper end and the bottom of the T-like groove or the bottom of the circular-truncated-cone-shaped groove, and the welding steps comprise rotary pressing, rotary pressing and friction, sudden stop and upsetting. The intermediate layer alloy is used as a medium, direct contact friction of a welded workpiece is avoided, surface oxidation films of adjacent base metal are broken and gaps are filled through severe plastic deformation of the intermediate layer under rotary extrusion of the workpiece, and effective welding under the conditions of low upsetting friction pressure and no obvious deformation of the workpiece is achieved. And a dissimilar metal welding interface is prevented from being overheated to generate an overthick intermetallic compound, subsequent machining is omitted, near-net forming of a friction welding joint is achieved, and the production efficiency is improved.

The invention discloses a high-cycle fatigue life test method and device for a thin-wall sinking locking structure, relates to the technical field of thin-wall sinking locking structures, and aims to solve the problems that a mechanical property test method for a locking structure after severe plastic deformation is lacked at present, and a test piece adopted by an existing thin-wall test is extremely easy to break. The method comprises the following steps: acquiring a first target loading load and a second target loading load of a test piece; the test piece is of a cantilever beam type structure; based on the first target loading load, the test device is adopted to carry out initial plastic strain force loading treatment on the test piece, and a target test piece is obtained; and performing a high-cycle fatigue test on the test piece by using the test device based on the second target loading load. The test piece adopted by the high-cycle fatigue life test method for the thin-wall sinking locking structure is not easy to break, and the fatigue life test of the locking structure after severe plastic deformation can be realized.

The invention discloses an antibacterial heterostructure stainless steel coating and a preparation method thereof, and relates to the technical field of metal material surface modification.The preparation method of the coating comprises the steps that a stainless steel plate serves as a base body, heterostructure alloy bars of different proportions are prepared through a bar insertion method, and the heterostructure alloy bars are prepared; and the heterostructure alloy bar is subjected to solid-phase coating on the surface of the matrix through friction surfacing, so that the antibacterial heterostructure stainless steel coating is obtained. Two different metals are fused through severe plastic deformation generated by friction surfacing to form a heterostructure stainless steel coating to be coated on a substrate, and the corrosion resistance and antibacterial performance of the coating can be improved by adjusting the volume ratio of the two materials. The coating prepared by the preparation method disclosed by the invention is uniformly coated on the surface of a matrix and has corrosion resistance and antibacterial property, the antibacterial rate on pseudomonas aeruginosa can reach 94.6%, and the antibacterial rate on staphylococcus aureus can reach 96.7%.

The application relates to a composite plate performance optimization method based on a roller bending-ultrasonic flattening process cycle, S1, selecting a composite plate blank with a corresponding thickness; S2, placing the composite plate blank into a heating furnace and heating; S3, repeatedly roller bending the heated composite plate blank to be rolled into a circular arc shape with a certain angle; S4, inverting and turning over the repeatedly roller-bent composite plate blank on a mold for ultrasonic flattening; S5, turning over the composite plate blank, reheating the composite plate blank after turning over, and then performing reverse roller bending and reverse ultrasonic flattening; S6, setting the heating composite plate-roller bending-ultrasonic flattening-turning over the composite plate blank-reheating-reverse roller bending-reverse ultrasonic flattening of steps S2-S5 as one cycle, and then recycling steps S2-S5 multiple times to obtain the composite plate blank. The application can eliminate residual stress, break grains and improve microstructure through repeated severe plastic deformation and physical ultrasonic vibration, so as to improve the performance of the plate blank.

This invention discloses a two-step oscillating hot-pressing sintering method for WC-Co cemented carbide. Specifically, the method involves: loading WC-Co cemented carbide mixed powder into a mold and pre-pressing it; firstly, holding the powder at 800°C in a vacuum environment to degas and pre-sinter the billet; then applying unidirectional oscillating pressure to the billet through the mold and raising the temperature to 1100°C for solid-state sintering. Dynamic pressure causes WC particles to rearrange, and Co particles undergo severe plastic deformation under the pressure of the WC particles, further increasing the relative density of the billet; finally, the temperature is raised to 1300-1350°C to form a WC-Co eutectic liquid phase. Dynamic pressure drives further particle rearrangement, and the eutectic liquid phase uniformly fills the gaps between WC particles, completing the sintering process. This invention improves the three-dimensional spatial distribution uniformity of the Co phase, eliminates residual porosity, effectively inhibits abnormal growth of WC grains, and produces cemented carbide with excellent strength and toughness.

The application discloses a strain-induced supersaturated solid solution analysis method for a non-miscible alloy system based on mixed entropy evolution, and the method comprises the following steps: for a target A-B binary alloy, a mixed entropy-component relationship diagram of the target A-B binary alloy is drawn; the average component and the initial equilibrium phase component point of the target A-B binary alloy are calibrated in the diagram; based on the increase of the mixed degree of the entropy generation driving force, the two-phase components are predicted to evolve in the entropy increase direction during a severe plastic deformation process, until a single-phase supersaturated solid solution is formed. Based on the irreversible thermodynamic principle, the severe plastic deformation process is defined as a continuous external entropy generation source for driving the evolution of the system, through the analysis of the dynamic competition mechanism of element mixing and element demixing dominated by the entropy generation source, the formation mechanism of the supersaturated solid solution is revealed, and the application provides a universal theoretical tool for understanding and predicting the supersaturated solid solution behavior of the non-miscible alloy system under the severe plastic deformation.

The application discloses a kind of metal surface nanocrystalline preparation method and application based on controllable fretting friction, belong to material preparation technical field.The method is first to the surface of metal sample pretreatment, subsequently it is placed in fretting friction testing machine, by controlling normal load, displacement amplitude, frequency, time and environmental temperature etc.Parameter, make the pair of mating and sample surface occur fretting friction.The core is, utilize the local transient temperature rise generated in the process of fretting friction, make metal surface layer occur dynamic recrystallization while severe plastic deformation, to form nanocrystalline layer in one step, without secondary heat treatment.The application solves the problems such as long process, high energy consumption and difficult to control surface quality of traditional surface nanocrystallization technology, can prepare the uniform nanocrystalline layer with surface grain size in 200-1200nm and layer thickness in 2-30μm range, significantly improve the corrosion resistance of metal material, and process is simple, controllability is strong, and widely applicable material.

The application discloses a high-entropy layered transition layer material for titanium-steel connection and a preparation method thereof, and belongs to the technical field of alloy or non-ferrous metal processing. Flaky metals are stacked together, rolling is carried out at room temperature, the rolled product is folded along the length direction, and the rolling is recycled to a predetermined pass, and then the obtained intermediate sample is made into a bulk material; the bulk material is subjected to heat treatment-heat rolling and thinning, and finally the high-entropy layered transition layer material for titanium-steel connection is obtained. Through the method, the metals are subjected to severe plastic deformation, the layer spacing is reduced, and partial solid solution occurs between the metals after rolling. After heat treatment, element diffusion is completed and a layered non-uniform structure is maintained, and the alloy defects are further reduced through heat rolling and thinning. The application has the advantages of simple process, single-phase structure of the prepared alloy, and relatively high hardness.

The invention relates to a high-strength and ultralow-magnetic susceptibility Au-Pt-Pd alloy wire as well as a preparation method and application thereof, and relates to the technical field of new materials. According to the preparation method, through the unique process combination of smelting, homogenization, severe plastic deformation and specific aging, the problem of contradiction between the alloy strength and the ultralow magnetic susceptibility is successfully solved, and the prepared Au-Pt-Pd alloy wire has the strength and the ultralow magnetic susceptibility far higher than those of a traditional Au-Pt alloy and still keeps certain plasticity.

The present application belongs to the technical field of plastic processing of thin-walled aluminum alloy products, and relates to an aluminum alloy seamless gas cylinder and a manufacturing method thereof. The gas cylinder is formed by a cylinder mouth side half cylinder and a cylinder bottom side half cylinder through seamless inertia friction welding. The cylinder mouth side half cylinder and the cylinder bottom side half cylinder are both prepared by performing severe plastic deformation on an aluminum alloy cylinder body at room temperature through a low-temperature high-pressure torsion device. The shoulder and / or bottom curve surface of the cylinder is formed by layer-by-layer crystallization refinement of metal under high pressure, and a uniform nano-scale or sub-micron ultra-fine grain structure is formed in the material. The present application solves the problems of wrinkle, stacking and high scrap rate caused by difficult temperature control in the traditional hot closing process by performing layer-by-layer severe plastic deformation on the aluminum alloy cylinder body at room temperature through a low-temperature high-pressure torsion process, thereby greatly improving the forming quality and mechanical reliability of the gas cylinder.

The invention discloses a preparation method of a fine-grain high-hardness high-flatness copper plate, which comprises the following steps: (1) sequentially cleaning and polishing a high-purity oxygen-free copper plate to obtain a pre-rolled plate; (2) stacking a plurality of pre-rolled plates, fixing the edges of the pre-rolled plates, and performing multi-pass rolling at room temperature to realize accumulative ply rolling, so as to obtain rolled plates; (3) carrying out annealing treatment on the rolled plate in an inert atmosphere, and then straightening; (4) the annealed plate is subjected to laser surface melting treatment; and (5) surface chemical mechanical polishing and cleaning are carried out, and the fine-grain high-hardness high-flatness copper plate is obtained. According to the method, the copper plate is subjected to severe plastic deformation through the accumulative roll bonding technology, the refining limit of a traditional machining mode on the grain size is broken through through the large dependent variable, then through laser surface melting, the grain size of the surface of the copper plate is further reduced, meanwhile, the surface hardness is increased to 120-190 HV from 50-60 HV, the polishing efficiency is remarkably improved, and the polishing quality is improved. And finally, the high-flatness copper plate is obtained.

The invention discloses a method for regulating and controlling heterogeneous growth of a layered double-metal hydroxide film in a friction stir welding seam area, and relates to the technical field of friction stir welding corrosion protection. The method comprises the following steps: performing friction stir welding on two magnesium alloy plates to obtain a weld zone; and placing the weld zone in an LDHs growth solution for hydrothermal reaction. The reaction time is regulated and controlled through a hydrothermal method, and an MgAl-LDHs film layer grows in a weld zone. More electrochemical active sites are formed in a welding seam area due to severe plastic deformation in the welding process, more precursors are promoted to be formed in the initial growth stage, and the LDHs structure is induced to grow more compactly and more uniformly due to inherent defects of the welding seam area, so that structural optimization of an LDHs film layer is realized, and the welding seam area is better protected from being corroded.

The application belongs to the technical field of cord steel preparation, and particularly relates to a high-strength and high-plasticity cord steel and a preparation method thereof, the preparation method comprising the following steps: S1, obtaining a cord steel casting blank, heating, rolling and cooling the cord steel casting blank to obtain a cord steel wire rod, and the structure of the cord steel wire rod is a pearlite structure with an average interlamellar spacing of 95-100 nm; S2, cold drawing the cord steel wire rod to obtain a cord steel wire material, and the total surface reduction of the cold drawing is greater than or equal to 85%; and S3, heat treating the cord steel wire material to obtain the high-strength and high-plasticity cord steel, and the holding temperature of the heat treatment is 280-300 DEG C. According to the application, a pearlite matrix is obtained through alloy composition and cooling design, and severe plastic deformation is performed to construct an initial state with high defect density, low-temperature heat treatment is adopted to drive short-range diffusion of interface carbon atoms to construct a composition gradient and drive diffusion of micro-alloy elements to regulate nanometer precipitates, and the interface plasticization and precipitation reinforcement are synergized.

The invention discloses a preparation method of a high-strength aluminum-magnesium-manganese alloy material, and belongs to the technical field of metal materials. The method comprises the following steps: taking aluminum as a matrix, and adding elements such as magnesium, manganese, zinc, copper, zirconium and titanium to prepare a master melt; the preparation method comprises the following steps: preparing yttrium oxide and other nano ceramic suspension liquid, atomizing and drying into powder, and blowing into a melt to introduce nano particles; and through severe plastic deformation such as semi-continuous casting, homogenization heat treatment, equal channel angle channel extrusion and the like, hot rolling and aging treatment, dispersion strengthening of the nano-particles is achieved. Optimization includes nano-particle replacement, multiphase strengthening, parameter adjustment, in-situ phase formation and the like, alloy grains are refined to 80-200 nm, and the strength is remarkably improved. Compared with the prior art, the process is environmentally friendly, accurate in control and suitable for high-strength application of an inverter shell and the like, the tensile strength can reach 450 MPa or above, and the ductility is larger than or equal to 10%.

According to the high-strength alloy serving under the medium-temperature long-time aging working condition and the preparation method of the high-strength alloy, the alloy structure is refined in the mode that severe plastic deformation and medium-temperature annealing treatment are combined, and the grain size of the finally prepared alloy ranges from 0.3 micrometer to 0.4 micrometer. According to the invention, through a simple severe plastic deformation process, grains are sharply refined to ultra-fine grain size, and the strength of the alloy is obviously improved; while grains are refined and the strength is improved, a large number of grain boundaries and dislocations are successfully introduced, and generation of a precipitated phase is promoted. A precipitated phase effectively pinns a grain boundary, so that the strength is improved, the precipitated phase and crystal grains grow and symbiosis in the long-time annealing process, the crystal grains grow very slowly, growth of the crystal grains is effectively inhibited, even if the alloy is subjected to long-time annealing at 600 DEG C, the crystal grain size is still kept at the ultra-fine grain size, excellent thermal stability is kept, and performance reduction is slowed down. The alloy is suitable for application scenes requiring high performance and needing long-term service in a medium-temperature environment.

The invention relates to a high-performance bismuth telluride-based thermoelectric material and a preparation method thereof. According to the method, a preformed blank is subjected to a multi-stage thermal deformation process, specifically, first-stage thermal extrusion is conducted at the temperature of 430-530 DEG C and the medium extrusion ratio, and densification and texturing are preliminarily completed; then, second-stage hot extrusion is immediately carried out at the temperature of 350-450 DEG C under the high extrusion ratio, and high-density dislocation is introduced through violent plastic deformation; and in the third stage, equal-channel angular pressing can be adopted for subsequent shear deformation, so that the dislocation density is further increased, and grains are refined. By accurately controlling the time sequence and strength of a thermal field and a shear force field, a multi-mode defect structure from a nano precipitated phase and a crystal boundary in-place error network is cooperatively constructed in the material, and full-spectrum scattering of phonons is realized, so that the crystal lattice thermal conductivity is remarkably reduced while good electric transport performance is kept.

The invention discloses an ultra-fine grain high-plasticity copper-silver alloy stranded wire and a preparation method thereof, and belongs to the technical field of copper alloy materials, the copper-silver alloy stranded wire is composed of, by mass, 2%-4% of silver, 0.05%-0.1% of zirconium and the balance copper, the average grain size ranges from 200 nm to 500 nm, the tensile strength is larger than or equal to 500 MPa, the ductility is larger than or equal to 8%, and the electric conductivity is larger than or equal to 85% IACS. The preparation method comprises the steps of vacuum induction melting, homogenizing annealing, hot extrusion cogging, equal-channel angular pressing, cold drawing, stranding forming and low-temperature recovery annealing, the ultra-fine grain structure is regulated and controlled through the zirconium microalloying and composite severe plastic deformation process, and the bending life is prolonged by more than three times compared with that of a common copper stranded wire; the cable bending device can be used for frequent bending scenes such as robot cables and medical equipment cables.

The invention discloses a preparation method of a high-strength and high-conductivity graphene metal-based composite material, and belongs to the technical field of metal-based composite materials. The invention relates to a preparation method of a high-strength and high-conductivity graphene metal-based composite material, which comprises the following steps: compounding spherical graphite serving as a raw material with metal powder, molding and sintering the mixed powder to obtain an ingot blank, and finally gradually stripping a graphite sheet layer through severe plastic deformation to form graphene, thereby obtaining the graphene metal-based composite material. After the spherical graphite and the metal powder are mechanically mixed and ball-milled for a certain time, all phases of the powder are uniformly distributed, and after an ingot blank is prepared and sintered, multi-stage severe plastic deformation is carried out. In the process of large plastic deformation, graphite flake layers are gradually peeled off and arranged in a certain direction, and the graphene metal matrix composite material is finally obtained after multi-stage plastic deformation.

The application discloses a heat treatment process for a metal alloy after large plastic deformation and relates to the technical field of metallurgy. The process is de-energization treatment before solid solution treatment. The de-energization treatment is heat preservation for 12 hours or more under the condition that the solid solution temperature of the metal alloy is 1 / 3 or less. The application realizes the transformation of the structure from a metastable state to a stable state based on the dissipation of the energy of the alloy structure after deformation, and then realizes the regulation and optimization of the second phase while inhibiting the grain growth.

The invention relates to a preparation method and application of a titanium hydrogen storage alloy block. After the titanium hydrogen storage alloy block prepared by the preparation method disclosed by the invention is stripped from the outer-layer titanium shell, the titanium hydrogen storage alloy block can be directly subjected to hydrogen absorption and desorption reaction at normal temperature in a complete block form without secondary treatment; the problem that the titanium hydrogen storage alloy block is difficult to strip due to too compact shell is effectively avoided; the titanium waste is adopted as the raw material, and low raw material cost is maintained. In addition, according to the preparation process, the traditional procedures such as smelting crushing or severe plastic deformation are simplified, the titanium hydrogen storage alloy block capable of being directly used is obtained only through one-step sintering, addition of high-cost rare earth elements is avoided, and the advantages of short procedures and low cost are both considered.

The invention discloses titanium alloy bar ultra-fine grain structure drawing equipment and a titanium alloy bar ultra-fine grain structure drawing method. The equipment comprises a rack, a preheating mechanism, a multidirectional asynchronous shearing deformation die holder, a traction mechanism and a material receiving mechanism which are arranged in sequence. The core is that a die core assembly which can be driven by an independent servo system to rotate and an inlet floating clamp holder are arranged in the die holder. During working, a bar continuously passes through the die rotating at a high speed under the action of traction force, and continuously changing circumferential shear deformation is dynamically superposed on the basis of axial tensile deformation of the bar by independently controlling the drawing speed and the rotating speed of the die, so that multidirectional asynchronous shear strain accumulation and efficient grain refinement are realized. The method strictly follows the drawing process definition, the problem that continuous production cannot be achieved through a traditional severe plastic deformation technology is solved, and the high-performance ultra-fine grain titanium alloy long bar can be efficiently and stably prepared.

The invention relates to the field of metallurgy, in particular to a production method of a low-cost high-quality high-carbon bearing steel GCr15 wire rod, the process route comprises the steps of steelmaking, continuous casting, heating in a heating furnace and rolling, crystallizer electromagnetic stirring and tail end electromagnetic stirring are used for continuous casting, and a continuous casting billet dynamic soft reduction process is used. The compression ratio of the cross section area of a casting blank to a final wire rod is larger than or equal to 160, and a high-temperature decarburization prevention coating is sprayed before the casting blank enters a furnace. Through the high compression ratio and severe plastic deformation, coarse carbides are crushed into fine dispersed particles, original as-cast dendritic crystals are crushed, and macrosegregation is relieved; through continuous casting crystallizer electromagnetic stirring, tail end electromagnetic stirring and large continuous casting blank rolling reduction, casting blank element segregation is improved, and the core compactness is improved; through casting blank shot blasting and anti-decarburization coating spraying, the high-temperature diffusion and anti-decarburization requirements of the heating furnace are balanced; and by controlling the rolling temperature and the cooling rate, precipitation of network carbides is inhibited, and the control level of the bearing steel wire rod carbides is further improved.

The invention discloses a metal copper bar bending method. The method comprises the following steps: firstly, preferentially selecting annealed soft T2 red copper (the hardness is HV50) with the oxygen content of less than or equal to 0.02%; then the copper bar is subjected to recrystallization annealing softening treatment, and the annealing temperature is 260 + / -10 DEG C; and after the annealed copper bar is cooled to room temperature (25 + / -5 DEG C), the copper bar with scratches, oxide skin, mechanical internal damage or rolling defects on the surface is removed in a visual inspection or ultrasonic flaw detection mode. T2 red copper with the oxygen content being smaller than or equal to 0.02% is adopted as a raw material to machine the metal copper bar, recrystallization annealing softening treatment is conducted, and therefore the ductility of the copper bar is improved. And then the bending radius of the copper bar is optimized, so that the included angle between the bending line of the copper bar and the rolling direction of the copper plate is 45-90 degrees, bending in the parallel rolling direction is avoided, the cracking risk is reduced, the risk of severe plastic deformation of the inner side and the outer side of the copper bar is reduced, and the conductivity of the copper bar is prevented from being influenced.

The invention discloses a friction stir deposition method and a friction rolling deposition forming device. The friction stir deposition method comprises the step of rolling a deposition layer formed by friction stir deposition. The friction rolling deposition forming device comprises friction stir deposition equipment and rolling equipment, the rolling equipment comprises a rolling wheel, and after a deposition layer is formed through friction stir deposition, the rolling wheel can roll the deposition layer. Through rolling, the deposition layer generates severe plastic deformation and induces dynamic recrystallization, the grain refining effect is achieved, meanwhile, replastic flowing at the interface of the deposition layer and the substrate is promoted, and the interface bonding strength of the deposition layer and the substrate is remarkably improved; the friction contact between the tool head and the deposited workpiece can be weakened, the tool head is prevented from being abraded, and the service life of the tool is prolonged.

The invention discloses a semi-solid metal slurry preparation method based on equal channel angular pressing, and belongs to the technical field of metal semi-solid forming. The method comprises the following steps: (1) carrying out homogenizing annealing treatment on a metal as-cast blank to obtain an annealed blank; (2) cutting a bar, putting the bar into an equal channel angular extrusion die channel, and carrying out graded speed regulation equal channel angular extrusion on the bar; (3) rotating the extruded blank by taking the axis of the blank as a rotating shaft, and repeating the step of graded speed regulation equal channel angular extrusion until the total rotating angle of the blank reaches 360 degrees, so as to obtain a deformed blank; and (4) the deformed blank is subjected to semi-solid isothermal treatment, and semi-solid slurry is obtained after water cooling. According to the method, by optimizing the corner angle of the equal channel angular extrusion die channel and combining graded speed regulation control in the extrusion process, stress concentration and severe plastic deformation of the as-cast blank can be well generated, and crystal grains are broken and fine, so that element segregation of the semi-solid slurry is improved, and the slurry with uniform solid and liquid and fine crystal grains is obtained.

The invention discloses a device and method for friction stir welding of a hyperbolic skin in a shaft shoulder self-adaption mode. The device comprises a rotating shaft sleeve device, an adjustable stirring needle, a first fastening bolt, a fixing disc, a jackscrew and a self-adaption rolling device, wherein the rotating shaft sleeve device is installed on a main shaft of a welding machine. The specific process is as follows: firstly, an adjustable stirring needle and a self-adaptive rolling device take a complex space curved surface of a skin piece as a reference surface, a stirring connecting part is inserted into a certain depth of a plate, the material is stirred, rubbed and softened under the action of high-speed rotation, and a metal material generates severe plastic deformation under the coupling action of a heat engine; shaft shoulder rolling part curved surfaces at the bottoms of the self-adaptive rolling devices are in self-adaptive point contact and roll-press a skin part to be welded along with welding, shaft shoulders and complex curved surfaces are high in fitting performance, finally, a softened metal material forms a fine equiaxed crystal structure in a dynamic recrystallization mode, metallurgical connection of hyperbolic skin is completed, and the service life of the hyperbolic skin part is prolonged. Therefore, non-thinning welding forming of the hyperbolic skin is achieved.

The invention belongs to the technical field of material surface mechanical strengthening, and particularly relates to a construction method of a variable-diameter thin-wall shaft surface gradient nanostructure, which is suitable for surface strengthening machining of key parts of high-end equipment such as a gas turbine transmission shaft and a wind power main shaft. A gradient nanostructure layer with a certain depth is formed on the surface of the variable-diameter thin-wall shaft part through the surface nanocrystallization technology, and the surface of the variable-diameter thin-wall shaft part is remarkably strengthened. The core of the method is that a tool platform for conducting surface nanometer strengthening on the large-size and complex-shape shaft piece is built; and meanwhile, in the surface severe plastic deformation treatment process, rigidity compensation is provided for supporting the thin-wall structure, and the thin-wall shaft piece is prevented from deforming and losing efficacy. And finally, the gradient nanostructure layer with the obvious strengthening characteristic is completely obtained on the surface of the thin-wall shaft piece. According to the method, the problem of keeping the structural stability of the variable-diameter thin-wall shaft part in the surface machining process can be solved, and meanwhile a machining platform and a solving mode are provided for surface nanocrystallization treatment of large-size complex devices.

The invention discloses a preparation method and application of metal surface nanocrystals based on controllable fretting friction, and belongs to the technical field of material preparation. The method comprises the following steps: firstly, pretreating the surface of a metal sample, then placing the metal sample in a fretting friction testing machine, and enabling a friction pair and the surface of the sample to generate fretting friction by controlling parameters such as normal load, displacement amplitude, frequency, time and environment temperature. The method is characterized in that local instantaneous temperature rise generated in the fretting friction process is utilized to enable a metal surface layer to generate dynamic recrystallization while severe plastic deformation is performed, so that a nanocrystalline layer is formed by a one-step method, and secondary heat treatment is not needed. According to the method, the problems that a traditional surface nanocrystallization technology is long in process, high in energy consumption, difficult in surface quality control and the like are solved, the uniform nanocrystalline layer with the surface grain size ranging from 200 nm to 1200 nm and the layer thickness ranging from 2 micrometers to 30 micrometers can be prepared, the corrosion resistance of the metal material is remarkably improved, the process is simple, controllability is high, and the applicable materials are wide.