CN101194055A - Method of producing nanocrystalline monolithic articles - Google Patents

Abstract

A products having at least a portion thereof with a nanocrystalline microstructure, and methods of producing such products. The method generally entails machining a body to produce a polycrystalline chip having a nanocrystalline microstructure. The chips produced by the machining operation may be in the form of particulates, ribbons, wires, filaments and/or platelets. The chips may be consolidated (with or without comminution) to form a product, such that the product is essentially a nanocrystalline monolithic material consisting essentially or entirely of nano-crystals, or of grains grown from nano-crystals. Alternatively, the chips may be dispersed in a matrix material, such that the product is a composite material in which the chips are dispersed as a reinforcement material. According to a particular aspect, a monolithic article can be formed entirely from a single chip by deforming the chip and/or removing material from the chip.

Description

Produce the method for nanocrystalline monolithic articles

The cross reference of related application

Present patent application requires the U.S. Provisional Application the 60/677th submitted on May 3rd, 2005, No. 248 interests, and the present invention be submitted on January 30th, 2004, co-pending U.S. Patent application the 10/707th, the part of 999 series numbers continues patent application, this U.S. Patent application the 10/707th, 999 series numbers are United States Patent (USP)s the 6th, 706, No. 324 divide an application, this United States Patent (USP) the 6th, the interests of No. the 60/244th, 087, the U.S. Provisional Application submitted on October 28th, 2000 have been required for 706, No. 324.By reference these contents in first to file are merged in this literary composition.

Background of invention

The present invention relates generally to the method for producing material and article with nanocrystalline microstructure, in more detail, relates to by processing (machining) and produces such material and article, and utilize described Nanocrystalline materials to form product subsequently.

Can make the metal alloy distortion obtain very many benefits by applying very large plastix strain (plastic strains).Main benefit is to obtain microstructure to refine and enhanced mechanical property and physicals.The microstructure that current people are interested especially to be to use the plastic deformation (SPD) of " acutely " to produce to have superfine crystal particle (UFG ' s), especially the bulk solid of nanocrystalline structures (NS) (bulk solid), the feature of described nanocrystalline structures be they atomic arrangement specified size less than 1 micron crystal in.Because nanocrystalline solids shows and has very big ductility, formability and resistance of crack propagation, and has interesting chemistry, optics, magnetics and electrical properties, so they have caused people's interest.Nanocrystalline solids also seems very different with micro crystal material (specified size is 1 micron crystal that arrives less than 1 millimeter) to the response of radiation and mechanical stress, can be by changing the response that crystallographic dimension change them.Material by fixed nanocrystalline powders manufacturing also demonstrates has the enhanced quality that can not find usually in common material.As a result, if Nanocrystalline materials can be made cheaply, believe that they have the great potential of using in industrial application.

Multistage deformation processing (multi-stage deformation processing) is one of the most widely used experimental technique of changing of microstructure that research produces by very big strain deformation (strain deformation).Noticeable example comprises for example roll extrusion, stretching and equal channel angular extruding (ECAE) such technology.In this method, by the deformation in a plurality of stages of cumulative application very big plastix strain (true plastix strain is 4 or bigger) to be forced in sample, the Effective strain in each stage of deformation is about 1.The formation of microlitic structure and nanocrystalline structures has utilized multistage deformation processing to be proved in multiple ductile metal and alloy.But this processing technology has very large limitation and shortcoming.An important limitation is for example to cause big strain (strain) in the tool steel at very hard material.Other limitation comprises sizable uncertainty of the strain that can not force in the single deformation stage much larger than 1, deformation district (deformation field) and these are considered to that the formation of microstructure and material character are had main influence to the minimum control---for example strain, temperature, strain rate (strain rate) and phase transformation---of deformation district significant variable.

The most widely used technology of synthesis of nano crystal metal is a condensation of metal atoms from vapour phase.In this technology, make evaporation of metal by heating, and the atom that is evaporated for example is cooled in helium or the argon by being exposed to rare gas element subsequently, preventing chemical reaction, thereby kept the purity of described metal.The refrigerative atom condenses into common size in 1 single-crystal clusters (single-crystal cluster) that arrives in the 200nm scope.The production of ceramic nano crystalline is similar, just before the atoms metal that is evaporated is condensing, they and suitable gas (being oxygen under the situation of producing oxide ceramics for example) is reacted.The crystal that is produced can be compacted and sintering to form article, under the required sintering temperature of the microcrystal powder that is lower than same material, carry out usually.Though this condensation method is fit to make powder and the little sample that compresses, and can control the particulate size admirably, for most of non-experimental application, this condensation method is at present also impracticable.Because be difficult to by the forming of vapour phase control material, the aspect of the special limitation of this condensation method is the Nanocrystalline materials that can not form alloy.Another limitation aspect of this condensation method is, since the nano-sized particles of being produced, the more difficult high voltage block density that reaches.Other methods that have been used to the synthesis of nano crystal comprise aerosol processing, sol-gel method, high-energy ball milling polishing and hydrothermal method.But these technology can not be come the production Nanocrystalline materials with the practical application acceptable cost.

From as can be seen above, if a kind of more controllable and preferred low cost method can be used to the synthetic nanocrystalline solids that product is made that is used for, so such method will be an ideal.If a kind of method can be produced the nanocrystalline solids of multiple material, comprise being difficult to maybe very hard material and the alloy that can not handle with prior art that so such method will be an ideal.

Except above record be devoted to produce the effort of material by fixed nanocrystalline powders, people also to by functional material for example metal, alloy and pottery is made miniature and meso-scale components for example axle (shafts), dish and gear are very interested.Used herein, miniature and meso-scale components is the two and three dimensions article, its feature dimension is approximately from several microns to several millimeters.Though the Application Areas of these parts is clearly divided as yet, the expection Application Areas is widely, comprises ground transport, biomedicine, MEMS (micro electro mechanical system) (MEMS), space flight, generating, defence, nuclear industry and other.Current normally used miniature and manufacture method meso-scale components comprise for example energy beam processing of material removal process (material removal processes), little milling, little turning, laser ablation and micro discharges process (micro electro dischargemachining, micro-EDM).Use (substractive) material removal process technology that deducts in the production process of these miniature and meso-scale components and supply and add material processing (complement additive material processes), for example rapid prototyping technology and LIGA (taking from the initial of German words litho graphie, galvanoformung and abformung (lithography, electroforming and moulding))

Summary of the invention

The invention provides the method that its at least a portion has the product of nanocrystalline microstructure and produces such product.The present invention also provides can be by UFG, and particularly Nanocrystalline materials is produced the method for small article.The latter comprises the inexpensive method of making nano structural material and UFG material, and it combines with shaping and/or material removal process, to make the small article that can show enhanced structure properties and mechanical property.

Present method needs to process body (body) has nanocrystalline microstructure with production polycrystalline fragment (chip) generally.For example, described body can be processed by this way,, carries out process operation in the mode of forcing enough big strain deformation that is, to produce the fragment of being made up of nanocrystal fully.Described body can be formed by various materials, comprises metal, metal alloy, intermetallic material and stupalith.In addition, described body can have the microstructure of not having nanocrystal substantially, even can have single-crystal microstructure.Fragment by described process operation production can be microgranular, banded, wire, thread and/or tabular.Described fragment can be by fixed (pulverize or do not pulverize) to form product, so that described product is the nanocrystalline monolithic material substantially, this material is formed by nanocrystal or by the crystal grain of nanocrystal growth basically or fully.As selection, described fragment can be dispersed in the body material (matrix material), so that described product is matrix material (composite material), described fragment is dispersed in wherein as reinforcement material.According to special aspects of the present invention, by single fragment being out of shape and/or removing material from described fragment, monolithic articles can be formed by single fragment fully.

The above feature of the present invention is based on such judgement (determination),, comprises high strain rate by processing under appropriate condition to produce very big strain deformation that is, for example about 0.5 to about 10 plastix strain and up to per second 10 ⁶Strain rate, can in material, form nanocrystalline structures.The working method that is considered to produce suitable nanocrystalline structures comprises cutting technology and abrasion techniques.Cutting speed seems, and it is conclusive not being, if so that cutting tool is used to carry out process operation, can use any cutting speed basically.Because the production method of described fragment is the process operation that its parameter can accurately be controlled, thus for given bulk material, can be accurately with obtain fragment repeatablely required nanocrystalline microstructure.In addition, can adjust described process operation and be used for fragment multiple application, that have different grain sizes and macroshape with production.Usually can use the present invention to realize production of nanocrystalline chips, and can not produce any negative impact, so that described nanocrystalline chips can be used as the useful by-product of existing manufacturing operation and is produced to processed article.It should be noted that byproduct, before can be regarded as the waste material that described operation produces and abandoned simply by the fragment of production of the present invention and use, or fusing is with recycling as such manufacturing operation.

In view of the above, the invention provides a kind of controllable and inexpensive method of synthesis of nano crystalline solid, described nanocrystalline solids can be used to produce material all in one piece with the compound product.Method of the present invention also makes by being difficult to maybe can not to become possibility with the material produce nanocrystalline solids that prior art is handled, for example the alloy that can not process the stone material handled and can not handle with condensation method with multistage deformation.

Other purposes of the present invention and advantage will be understood better from following detailed description.

The accompanying drawing summary

Fig. 1 is according to an aspect of the present invention, uses the process synoptic diagram of cutting tool processing body with the production nanocrystalline chips.

Fig. 2 is electron lucent particulate transmission electron microscope (TEM) image from 52100 steel fragments, and three electron diffraction patterns that obtain from described particle different zones, the zone of each correspondence all is the distinct single crystal of the about 50nm of grain size to about 300nm in its proof image.

Fig. 3 shows the figure of annealing to the influence of copper fragment, wherein said copper fragment according to the present invention, make it have nanocrystalline structures by processing to produce.

Fig. 4 has shown the bright field TEM image of OFHC copper, and wherein said OFHC copper is processed according to the present invention, has the nanocrystalline microstructure that is produced by the different levels shear strain.

Fig. 5 is presented in the A16061-T6 alloy, the TEM image of the microstructure that produces with differently strained level processing according to the present invention.

Fig. 6 shows the TEM image of the grain growing (to about 200nm) in two nanocrystalline microstructure of Fig. 5, and wherein grain growing is owing to producing in about 1 hour at about 175 ℃ of thermal annealings.

Fig. 7 and 8 is respectively the TEM image of Inconel(nickel alloys) 718 and titanium foil, has shown according to the present invention the nanocrystalline structures after the processing.

Fig. 9 has shown the scanning image of nanocrystalline chips, and the various types of miniature and middle-sized parts of Figure 10 to 12 for can be directly being processed into by the fragment of Fig. 9.

Detailed Description Of The Invention

Be the microstructure and the mechanical property of the fragment determining to produce by machined steel, and for probing into the condition of producing them, we have carried out a research, the research causes having produced the present invention.The AISI 52100,4340 of the about 15.7mm of diameter and the steel column of M2 tool steel are heat-treated to hardness value respectively by through heating (through-hardening) and tempering be about 60 to 62R _c, about 56 to 57R _cWith about 60 to 62R _cBefore the processing, the initial microstructures of steel is the tempered martensite.The composition of steel sample (weight percent), austenitizing temperature (A _C3) and general grain size (GS) be summarised in the following table 1.

Table 1

The type of steel (AISI)
				C Mn Si Cr Ni Mo P S V Cu Al Co W Fe A C3(℃) GS(μm)	Maximum 0.035 maximum 0.040----------the surplus 815-845 7 of 4340 0.38-0.43 0.6-0.8 0.15-0.3 0.7-0.9 1.65-2.00 0.2-0.3	52,100 1.00 0.31 0.26 1.45 0.14 0.04 maximum 0.009 maximum 0.019--0.09------surplus 775-800 5	M2 0.8 0.35 0.35 4.52 0.2 5.39 maximum 0.027 maximum 0.005 2.09 0.13 0.02 0.39 6.86 surplus 1190-1230 5

Be noted that M2 has than 52100 and 4340 steel (A _C3About 800 ℃) much higher austenitizing temperature (A _C3About 1200 ℃).The high-accuracy lathe that has polycrystal cubic boron nitride (CBN) cutting tool by use is processed described steel column.Under certain conditions, comprise that cutting speed is that about 50 to 200m/min, depth of cut is that about 0.1 to 0.2mm, tool feeding speed (tool feed rate) is at least 0.05mm/rev, observe so-called white layer (WL) at the machined surface of 51200 and 4340 steel, but in any M2 steel sample, do not observe.As known in the art, white layer is (thick less than the 50 μ m usually) solid bed that approaches, and when steel stood high speed processing, abrasion or slides, white layer can form in the surface of some steel and fragment.White layer is resisted chemical corrosion and seem not have any feature under opticmicroscope, so be called " white layer ".

The fragment of Sheng Chaning is analyzed with opticmicroscope, X-ray diffraction, transmission electron microscope (TEM) and nano impress under these conditions, to determine their structure, composition and mechanical property.The nano hardness of described fragment is to assess by go up the impression that uses Berkovitch impression instrument (three diamond pyramids) to make the sub-micro degree of depth (sub-microdepth) at nano hardness tester (Nanoindenter XP).Impression instrument penetration depth is arranged on about 200nm usually, and it is usually corresponding to the load of about 10mN.This penetration depth is significantly less than the size (the most about 0.1mm) of analyzed fragment.According to the heavy burden-break-through curve during measurement impression and the discharged later, assess the hardness and the Young's modulus of described fragment.The particulate electron transparent samples of from fragment, obtaining by tem observation to determine their structure (for example, crystalline form or amorphous) and grain size.For this purpose, use mortar and pestle that described fragment is broken into smaller particles lightly, it is separated by ultrasonic agitation in methyl alcohol subsequently.Described subsequently particle is placed on screen (grid) and goes up and observe under TEM.Some particle or some zone of these particulate are electron lucents, can obtain directly image and these regional diffractograms.Described diffractogram is used for determining particulate degree of crystallinity, and the combination of bright field image and diffraction is used for determining grain size.

It should be noted that the fragment of each sample and machined surface all will stand very big strain deformation this moment during processing.The deformation that appears at the fragment shear surface can be as can be seen from Figure 1, and Fig. 1 has described, as described in the research, with wedge shape impression instrument (instrument) processing work surface.Just by the material of big strain deformation removal, that is, described fragment is gone up slip on the surface (being called inclined-plane (rake face)) of instrument.Angle between tool rake face and the working-surface normal is called as inclination angle (α).The limit that penetrates the wedge of described workpiece is a cutting edge.Amount of interference between instrument and workpiece is undeformed chip thickness depth of cut (t ₀), the speed of relative movement between instrument and workpiece is cutting speed (V _c).When the instrument cutting edge perpendicular to cutting speed and width of cut than cutting edge length and t ₀Hour, the state of plane strain deformation is preponderated, the experimental study that it is considered to process and the preferable configuration of theoretical investigation.

Can see that the formation of fragment is to take place by shearing among Fig. 1 in the planar set that is called as shear surface, wherein during fragment forms, force shear strain (γ).Shear strain can be estimated by following equation (1):

γ=cos α/sin Φ cos (Φ-α) (equation 1)

Wherein shear plane angle (Φ) is known t ₀And t _cFunction.Can use

ε=γ/(3) ^1/2(equation 2)

Predict effective Von Mises strain (ε).

Equation (1) shows that shear strain (γ) can be by doing large-scale change from big on the occasion of changing into big negative value (see figure 1) with inclination angle (α).In addition, the friction of instrument-chip interface also influences shear strain (γ) by its influence to shear plane angle Φ.

In view of the above and document report, can utilize suitable processing conditions produce between about 0.5 to about 10 effective plastix strain and up to per second 10 ⁶Strain rate, and large-scale shear plane temperatures.The scope of these values is apparently higher than the value that can realize in common violent plastic deformation processes.The geometric parameter such as the depth of cut (t of processing ₀), inclination angle (α) and cutting speed (V _c) influence shear deformation to be similar to the mode of forging or extrude middle punch die (dies) effect.Effective plastix strain along shear surface (deformation district) in the fragment can come systematically to change between about 0.5 to about 10 by changing the instrument inclination angle, and can change to lesser extent by change instrument and interfragmental friction.By changing for example V of tool geometry parameter and processing parameter _cAnd t ₀Can change average shear and normal stress (mean shear and normalstresses) on the shear surface, and the value of these stress can obtain from force measurement.At last, the temperature in deformation district can systematically change by changing cutting speed.For example, by in low speed (about 0.5mm/s) time cutting, temperature can remain on a little higher than envrionment temperature and reach very big strain deformation simultaneously.As selection, by cutting speed being increased to higher value, for example, and about 1 to about 2m/s, can reach the temperature that can be desirably in the fragment when undergoing phase transition (for example martensite phase transformation, fusing phase transformation).To change the ability that changes along the frictional force of instrument-chip interface up to triple, also be confirmed by low frequency modulation and the lubrication that is used in combination instrument coating, instrument-chip interface, wherein said lubrication guarantees that lubricant always is present on described instrument and the described interfragmental interface.Described in process operation the control degree that can reach to friction (and other parameters discussed above and condition) can not in other violent plastic deformation processes, reach.In a word, the temperature in deformation district, stress, strain, strain rate and velocity field can utilize available mechanics model suitably to estimate, or obtain by direct measurement.So very big strain deformation conditions can be forced and can be on a large scale systematically change, this scope reaches and has exceeded getable scope in current other violent plastic deformation processes.

In research AISI 52100,4340 and M2 steel, normal stress and the shear-stress forced at the finished surface of described shear surface and each sample are estimated as about 2 to 4GPa.The temperature rising of inferring fragment raises greater than the temperature of machined surface usually, because the big relatively quality of described machined surface can pass away heat of friction that produces on most of tool rake face and the heat that produces owing to plastic flow in elementary deformation district (shear surface).Speed of cooling in described fragment and the workpiece is very high, estimates to be at least 0.5 * 10 ⁵℃/s.

Table 2 has been summed up the result who measures nano hardness in 52100 sample fragments and 52100 sample main bodys (bulk).

Table 2

	Hardness (GPa)	Durometer level (GPa)	Young's modulus (GPa)
				The fragment main body	12.85±0.80 10.70±0.85	11.5-16.2 9.0-12.0	235±8 235±16

Can find out that the chip hardness value is high more about 25% than the nano hardness value of 52100 steel main bodys, and they are discrepant on the statistics.In addition, described chip hardness is significantly higher than Knoop value, and the latter is used to report the not tempering martensite that is produced by 52100 steel samples that quench.This difference is significant, even causes producing such fact, that is, the hardness measurement of carrying out with sub-micron penetration produces usually than the high slightly hardness value of knoop hardness measurement.The described fragment that obtains by impression and the Young's modulus of material of main part almost with described material of main part indistinction, and approach the modulus value of the 220GPa that quotes as proof usually of steel.

Fig. 2 is the electron lucent particulate TEM image from described 52100 steel fragments.Three electron-diffraction diagrams that obtain from described particulate different zones are also shown in Fig. 2.Described diffractogram shows that each respective regions all is unique monocrystalline in the image, shows that described particle is a polycrystalline.In addition, can find out that crystal (or crystal grain) size is in about 50nm arrives the scope of about 300nm from the TEM image of each crystal region.To from 4340,52100 and the analysis of the TEM image of other debris particle of M2 steel, show that also fragment is a polycrystalline, its grain size usually at about 30nm in the scope of about 300nm.All comprise that cutting speed is about 100 to 200m/min, depth of cut about 0.1 to 0.2mm and tool feeding speed is at least the fragment that produces under the processing conditions of 0.05mm/rev and all shows and contain nanocrystalline structures (NS).And, the grain size of the grain size of the nano-scale of described fragment 5-7 micron of heat-treated steel sample before the processing of above report.Therefore, significantly, the not tempering martensite that is present at first in the steel sample has experienced change/transformation during processing.This conclusion is also consistent with the nano hardness comparative result of the fragment of steel sample discussed above and main body.

In the follow-up study of above research, we infer that the formation of nanocrystalline structures is shown as universal phenomenon in the course of processing, but not the phenomenon of having only steel and just can producing with wedge tool processing.For example, the hardness value of measuring the described layer of nano hardness demonstration of the 4340 steel fragments of producing by grinding is about 12 to about 13GPa, is significantly higher than the hardness of the initial perlite microstructure of described sample.Microstructure analysis shows that these fragments have the feature similar to the above fragment.By to grind the preliminary tem analysis of the fragment that titanium, copper, single-crystal iron and M50 steel produce with the wheel speed of 33m/s, show that also the fragment that is produced is made up of nanocrystalline structures.In another research, the nano impress of the brass fragment that produces by processing shows, their hardness than processing before the hardness about 50% of brass material to about 75%, show that these fragments also may be made up of NS.These observed results show, felicity condition very big strain deformation down may be the main drive of NS formation during occurring in material and removing.

Based on above research, we infer, are about 100 to process to about 200m/min with cutting speed, if enough big strain deformation, can 52100,4340 and the M2 steel in as one man produce nanocrystalline structures.Based on analyzing the formation of nanocrystalline structures in processing and grinding, consider that other conditions that may influence that nanocrystalline structures forms in the steel are useful.During processing, NS forms big strain deformation, localized hyperthermia, high quenching velocity and the possible austenite-martensite phase transformation of district's experience.The some of them condition may influence the generation of NS in this research.But except big strain deformation, these other conditions can reach in the Heat Treatment Of Steel of routine at an easy rate.For example, the described austenite-martensite phase transformation that is caused by rapid quenching is the key element in the thermal treatment.But, do not report that the NS in the steel is changed by thermal treatment.The hardness value of the martensite that is formed by thermal treatment also is starkly lower than the hardness value of the NS that is produced by high-velocity deformation in the similar type steel.These observationss show that though temperature-time history and phase transformation may be important, the condition that produces very big strain deformation seems that it is essential forming for NS in the hardness of determining grain size range, physicals and NS.Observations (all not experiencing the displacement sex reversal) by NS in the above non-ferrous metal has strengthened such supposition.Stand the microstructure in macroscopical metal sample of such distortion by observation, confirmed that described big strain deformation can cause producing very thin grain size.

In another research, form fragment by processing anaerobic high conductivity (OFHC) copper, commercially pure iron and 1018 steel.The initial grain size of these samples is respectively about 170,55,70 microns.The processing conditions of these materials comprises that depth of cut is that about 2.54mm and tool feeding speed are about 0.21mm/rev.For described copper sample, use about 28.8m/ minute cutting speed, and use about 6.375m/ minute cutting speed for described iron sample and 1018 steel samples.The common thickness of the fragment that produces is about 200 to about 1000 μ m.Prepare described fragment to be used for follow-up hardness and microstructure analysis by the metallography polishing.Use the Vickers impression to do hardness measurement so that obtain accurate mensuration, and do not have the relevant influence in surface described fragment bulk hardness.The indenture size is maintained at below 1/5 of described chip samples size, to guarantee the accuracy of hardness measurement.The chip samples of metallography polishing is also etched, with existing of substructure in analysis grain size, flow pattern and the crystal grain.Use SEM, AFM, TEM and opticmicroscope to observe these fragments.

We have also carried out parallel series of studies to the bulk samples (bulk samples) of described material, so that their hardness and microstructures before processing are assessed.Before processing, bulk samples is generally work hardening (work-hardened) state, because they are by stretching or extrusion process production.As a reference, the bulk samples of some sample and chip samples are annealed and replication hardness, so that obtain the true measuring result of the changes in hardness that caused by processing.For this purpose, on described copper fragment, iron fragment and 1018 steel fragments, carry out a series of annealing experiment, to understand the recrystallize behavior of these chip samples.Described recrystallize experiment uses different time-temperature cycle to carry out in controlled argon atmosphere furnace.For 4340,52100 and the research of M2 steel, analyze the hardness and the grain size of these samples according to above-described.

Table 3 is summaries of Vickers hardness measurement, and is provable from this table, and for described copper sample and iron sample, the hardness of fragment is apparently higher than the hardness of preceding described sample of processing and annealing specimen.

Table 3

Vickers hardness (kg/mm 2)
				Treatment condition copper iron 1018 steel	Substrate (base) 93 125 230	Fragment 143 290 300	Annealed substrate 67 86 209

Do hardness measurement at the different positions of whole fragment volume and show that Hardness Distribution is uniform basically.To studies show that of the Hardness Distribution in the partially-formed fragment of in the experiment of particular design, producing, when enter fragment from material of main part, when passing described shear surface, hardness sharply increases.

Fig. 3 has shown the recrystallize result of experiment on some copper fragment, and about critical temperature of 100 ℃ of proof existence, and when being lower than this temperature, even annealing time is 6 hours, hardness value can not reduce yet.This shows the mechanical property that can keep fragment by some heat treatment cycle.Come the PRELIMINARY RESULTS of the annealing experiment on comfortable iron and 1018 steel to show similar recrystallize behavior takes place when significantly higher temperature.Experiment shows that even after about 1000 hours, at room temperature, the hardness of described copper fragment, iron fragment and 1018 steel fragments also is retained, and at room temperature, after long-term observation, only observes the less variation of copper fragment microstructure.

Finally, the Inspection Certificate of the opticmicroscope of main body workpiece material, fragment and recrystallize fragment, AFM, SEM and TEM image, though described bulk samples has big relatively crystal grain (arriving about 170 microns scope about 55) before processing, (resolved) unique structure of telling in fragment is that size is in about 100 substructures that arrive in the scope of 500nm.Fig. 4 has shown the bright field TEM image of OFHC copper, and wherein OFHC copper is processed according to the present invention, has the nanocrystalline microstructure by shear strain (γ) generation of different levels.The corresponding diffraction image in zone of selecting has confirmed described polycrystalline microstructure, and this polycrystalline microstructure is equiaxial and average crystal grain is big or small is about 150nm.Usually in the feature that begins of the dynamic recrystallization fragment that can produce in about 13 shear strain as seen.Fig. 5 has shown the microstructure that produces in the A16061-T6 alloy in differently strained level processing according to the present invention.When higher strain (5.2), common grain size is about 90nm.Fig. 6 has shown because about 1 hour of about 175 ℃ of heating anneals, the TEM image of the grain growing that is produced in two nanocrystalline microstructure of Fig. 5 (to about 200nm).At last, Fig. 7 and 8 is respectively the TEM image of Inconel(nickel alloys) 718 and titanium foil, shows the nanocrystalline structures after the processing according to the present invention.Common grain size is about 70-100nm.

A series of studies show that described above can be present in other black and non-ferrous metal and the alloy by the condition of very big strain deformation formation nanocrystalline structures, for example titanium, aluminium, tungsten and their alloy.For example, after above research,, in annealed iron and single-crystal tungsten, produced grain size and be about 100 to 300nm nanocrystalline structures by very big strain deformation.So conclusion is, if processing conditions is forced very big strain deformation, can various cutting speeds process multiple material, as one man to produce grain size about 30, may be lower than 300 and the fragment of 100nm to 500nm.Usually for differing materials, suitable processing conditions difference, but can determine at an easy rate by experiment and can confirm by the existence of nanocrystalline grains.Because can control many different processing conditionss independently,, has the fragment of required grain size range with production so may adjust processing conditions.During studying, but also observe the fragment with NS of production different shapes and size.Usually by or the form of the fragment that can be produced comprise tabular, microgranular, banded, spirrillum, wire and the wrap wire round (tangled coils) that obtains by tool using processing.Subtract and cut described workpiece material though the formation of fragment is included in the narrow zone of shear surface, produce very big strain, described fragment vertically and cross-sectional shape mainly control by the geometric parameter of processing conditions (for example, speed of feed and depth of cut) and instrument.For example, by use groove on tool rake face, described fragment can be curled into helix.So it is feasible producing high strength, nanocrystalline chips with various macroshapes.Such fragment can be by fixed (pulverize or do not pulverize) and sintering producing nanocrystalline monolithic articles, or be used as the continuous and/or discontinuous stiffener of multiple body material, and described body material comprises polymkeric substance, metal and pottery.Make the design that the possibility with the continuous nanocrystal stiffener of difform cheapness helps novel material by the present invention's processing.

Infer also that from above research if use enough sharp instrument to form fragment, pottery and intermetallic material can be processed by cutting or abrasion probably, to form the fragment of being made up of nanocrystalline structures fully.Under such condition, can expect to occur big strain plastic flow, and in fibrous, zonal potsherd, observe described big strain plastic flow by abrasion MgO pottery and soda-lime glass production.These fragments demonstrate with the plasticity by ductile metal and cut the closely similar feature of fragment that forms.When and glass for example ceramic with sharp instrument cutting brittle solid, force significant confined pressure compression because form the district at fragment, can expect high-velocity deformation to occur, and high temperature occur.We think, process with high cutting speed with sharp, monocrystalline or polycrystalline diamond instrument, with the plasticity cutting that is implemented in the brittle solid,, under 30 to 100m/s, grind at a high speed as diamond-impregnated wheel with the fine granularity size to produce the meticulous granular or tabular fragment of forming by NS.Under such condition, because used high cutting speed, the extremely high pressure of forcing and in the shearing of abrasive-chip interface, described fragment stands violent deformation and high temperature probably.

Though the previous indicator gauge of nanocrystalline structures reveals unique natural characteristics combination, realize that in material of main part these properties of combination are subjected to the expensive obstruction of nanocrystalline structures (i.e. the nanocrystalline structures of producing by condensation method) always.As previously mentioned, the nanocrystalline structures by condensation method production also is limited to the particle of the nano-scale of pure metal or pottery basically, and the ultra-fine grain limitation of size can be by the compact density of fixed realization.But, the polycrystalline material source that the present invention makes acquisition have nano-sized grains becomes possibility, and can low relatively cost production, particularly the present invention have proved that the fragment with nanocrystalline structures can produce under the situation of the workpiece quality that does not damage processing.As a result, the present invention makes the low-cost monolithic that contains nanocrystalline structures and the widespread use of compound material become possibility.(for example pulverize, ball milling, abrasion and jet grinding or the like) fragment with nanocrystalline structures, make it possible to scale operation polycrystalline particulate, described polycrystalline particulate than the nano-sized particles of producing by condensation more easily by fixed and be compacted into big monolithic materials.Can further promote the compacting during sintering, because because the lattice defect of high density, Nanocrystalline materials shows the enhanced sintering kinetics usually, so can use lower sintering temperature.Though thermal treatment may cause grain coarsening (for example, as shown in Figure 6, recrystallize and grain growing), but for many application, the benefit that enhanced is handled (for example, lower sintering temperature, higher density, or the like) can surpass the grain coarsening result in the monolithic materials.The defect structure of the nanocrystalline particulate that produces by processing also may produce obtain monolithic materials new deformation process approach (for example, metal injection molded or flow casting molding (tape casting)), even for example silicon nitride is too for intrinsic brittle ceramic.In addition, can in by the electrical sheet of production of nanocrystalline chips, realize special magnetic property, for example enhanced property of transformer core.

The continuous band-shaped thing of high-strength nano crystallization fragment and thread can be in composite article and structure use as stiffener, and described composite article and structure comprise the concrete that is used for current runway, highway and the tunnel of strengthening by steel wire.As selection, long fragment can be interrupted to produce the stiffener of specified shape and size.For example, plate object can be produced by the fracture of control ribbon chips, and it can provide the most effective sclerosis in all discontinuous stiffener shapes.We have carried out preliminary research, and wherein the nanocrystalline chips of M2 steel is broken to form plate object, and it is added in the bronze matrix by spontaneous (stress-free) fusing infiltration subsequently, and does not have tangible chemical interaction.We have also successfully realized the infiltration of aluminium alloy (Al 356) matrix around the same M2 fragment that is shaped.The evaluation of the mechanical property of Al-M2 matrix material is to finish by done 60 nano impress at the different positions of this matrix material, has obtained the histogram of hardness and Young's modulus thus.Three kinds of different nature bunch, correspondence is positioned at the impression of Al matrix, M2 stiffener and Al-M2 interface zone, all differentiates in hardness and Young's modulus histogram.The hardness of Al matrix, interface zone and M2 steel stiffener and Young's modulus are respectively 0.8-1GPa and 70-90GPa, 1-4.5GPa and 100-140GPa, 8-13GPa and 180-235GPa.The average hardness of this matrix material and the entry evaluation of modulus value are shown these Al-SiC matrix materials with commercial acquisition are significantly not different.Do not observe tangible crackle around near the impression at Al-M2 interface or stiffener exposes (pull-out).These observationss make and be hopeful to add nanocrystalline platelets, continuous band-shaped thing, filament and particulate stiffener in multiple metallic matrixes, described metallic matrix comprises light-weight metal body material for example aluminium and magnesium, it has caused people's interest in the ground transport of many commerce and aerospace application, for example to reduce be the aspect of key factor to weight such as transmission shaft, brake facing and buoyant element.The liquid state processing that the use of expection metallic nanocrystalline stiffener can be conventional stiffener material (for example SiC) provides the wetting of remarkable improvement.

Osmotic treated is for utilizing the NS fortifier to produce for the matrix material, be several feasible way one of them.Additive method comprises stirring curtain coating, sintering and extruding.The problem of a key is the anneal act of the nanocrystal stiffener during matrix material is handled.In this, temper hardening tool steel and bearing steel for example M2 show their peak sclerosis response in the melting range of aluminium and magnesium alloy, the chance of improving stiffener character during handling matrix material is provided.In polymeric matrix, add nanocrystalline chips and be considered to practical, because the polymer cure temperature is low relatively, to such an extent as to do not have the stiffener annealing effect substantially by dip treating.

At last, the present invention also comprises the fragment forming process direct production article by the invention described above.Especially, above-mentioned processing treatment provides the ability of the tabular fragment of the multiple material of direct production, perhaps it can be deformed into tabular fragment, and do not lose required nanocrystalline structures, and carry out the post-treatment operation subsequently, by this operation, monolithic articles is formed by single fragment fully, for example by being out of shape this fragment or removing material from described fragment.Fig. 9 has shown directly the scanography image by the formalness of the tantalum with macro-size of processing and copper fragment.The about 75mm of tantalum fragment is long, and 5mm is wide, 500 micron thickness.This fragment directly by processing tantalum piece on the common forming mill with forming tool, is produced by roll straightening subsequently.Copper fragment shown in Fig. 9 is also produced by forming mill, but during fragment forms fragment is applied little tension force.The about 300mm of the size of copper fragment is long, and 5mm is wide, and 2mm is thick.Fragment shown in Figure 9 has confirmed can be directly to need not anyly fixedly just can produce big polycrystal by processing.That measures the fragment distortion shows that with undeformed thickness the shear strain during fragment forms in the fragment is much larger than 2.Discuss consistently with relevant strained, under big like this strain deformation conditions, have refining of significant microstructure, cause grain size in the fragment in about 50 scopes that arrive about 1000nm.Described chip hardness almost is three times of material of main part, and wherein said fragment processes from described material of main part.In various other metals and alloy, also refining of microstructure done similar viewing with the enhancing of relevant mechanical property.

Based on the ability of producing big like this nanocrystalline chips, we think can production length and width be several inches, thickness is up to the metallic nanocrystalline chips of about 0.25 inch (about 0.6cm).Those skilled in the art will recognize, produce the fragment that increases and to use machine, to adapt to the formation of so large-scale fragment with enough power and suitable tools.In addition, processed material for required chip size and the machine that is used for producing described fragment, should be enough ductile.Because the macroscopical fragment that goes out by processing and manufacturing shows curvature to a certain degree probably, so, may need the post-treatment deformation process of some types, for example roll straightening (comprising that thickness reduces a little) is eliminated curvature.In addition, may under different time-temperature condition, carry out such post-treatment deformation process, force extra control with microstructure and character to fragment.

The post-treatment thermal treatment or the hot mechanical treatment of macroscopic view fragment are extra steps, can carry out this step, by recrystallize and answer mechanism (recovery mechanisms) control microstructure.Because the microstructure that is produced after the thermal treatment depends on the strain formerly of forcing during fragment forms and the time-temperature history of thermal treatment (for example annealing), so, can realize multiple particulate or UFG microstructure with height homogeneity.The condition that can change described processing, deformation and heat treatment process makes the microstructure optimization, to obtain for any mechanical property and physicals of being overstated and being wanted by the article of described fragment manufacturing.

Subsequently, miniature and middle size article can be produced by described fragment, use tabular fragment as fertile material or the raw material of making described miniature and middle size article effectively.The article of Xing Chenging preferably keep the nanocrystal or the UFG microstructure of described fragment by this way, so expection shows enhanced mechanical properties, textural property, and/or physical properties, can improve performance, particularly in improving the application that strength-to-weight ratio and wear resistance play a crucial role.Example comprises miniature and middle-sized part, for example dish, gear and spiral type part.Figure 10 has shown discous part, and it is to be rolled by the smooth and A16061-T6 paper tinsel of nanocrystalline bulk to cut (punched) and form.Figure 11 and 12 shown utilize little EDM from the sample of nanocrystalline bulk Inconel(nickel alloys) 718 paper tinsels processing miniature/meso-scale components.Obviously find out from Figure 10 to 12, have overall dimension and reach several millimeters parts, can be directly by macroscopical fragment manufacturing of main body form, described fragment is according to the present invention, utilizes the common deformation process of a dimensioning, for example punching press, rolls and cuts, forges or the like (Figure 10) and utilize for example EDM, cutting and milling of material removal process (Figure 11 and 12) and produce.Can ignore because be applicable to the forming process of this step and the heating that the course of processing causes, so the nanocrystal of described fragment or UFG microstructure can be retained.

Though the present invention describes according to specific implementations,, significantly, those skilled in the art can adopt other forms.Therefore scope of the present invention is only limited by claim.

Claims (20)

1. method of producing nanocrystalline monolithic articles, this method comprises the steps:

The processing body has nanocrystalline microstructure with generation polycrystalline fragment; With

By described fragment is carried out single job at least, form monolithic articles by described fragment fully, described operation is selected from and makes described fragment distortion or remove material from described fragment.

2. the method for claim 1, this method further comprise, before the step that forms described monolithic articles, and leveling or align described fragment.

3. the process of claim 1 wherein and form monolithic articles by described fragment is out of shape.

4. the method for claim 3, wherein said deforming step is selected from punching press, rolls and cut and forge.

5. the process of claim 1 wherein and form monolithic articles by removing material from described fragment.

6. the method for claim 5, wherein said removal material step are the process operations that is selected from energy beam processing, little milling, little turning, laser ablation and micro discharges processing.

7. the method for claim 1, this method further comprises, after described formation step, carries out at least once additional material processing on described monolithic articles.

8. the method for claim 1, this method further comprises, after described formation step, to the thermal treatment at least once of described monolithic articles.

9. the method for claim 8, a wherein said at least thermal treatment comprises hot mechanical treatment.

10. the method for claim 8, wherein said thermal treatment causes the recrystallize of described monolithic articles.

11. the process of claim 1 wherein that described body is to be formed by the material that is selected from metallic substance, intermetallic material and stupalith, so that described monolithic articles is formed by described material fully.

12. the process of claim 1 wherein the maximum grain size of described fragment about 50 to the scope of about 1000nm.

13. the process of claim 1 wherein the maximum grain size of described monolithic articles about 50 to the scope of about 1000nm.

14. the process of claim 1 wherein that the maximum grain size of described fragment arrives the scope of about 1000nm about 50, and after described formation step, in described monolithic articles, keep the grain size of described fragment substantially.

15. the process of claim 1 wherein that the minimum size of described fragment is less than 1 centimetre.

16. the process of claim 1 wherein that the overall dimension of described monolithic articles is less than 1 centimetre.

17. the process of claim 1 wherein that the overall dimension of described monolithic articles is less than 1 millimeter.

18. the process of claim 1 wherein that monolithic articles is selected from axle, dish and gear.

19. the process of claim 1 wherein that described fragment experiences strain deformation during procedure of processing, it is characterized in that shear strain is greater than 2.

20. a method of producing nanocrystalline monolithic articles, this method may further comprise the steps:

Processing has the body of the microstructure of not having nanocrystal substantially to produce the polycrystalline fragment, this polycrystalline fragment is at least micron-scale, and has nanocrystalline microstructure, and this features of microstructures is, since enough strain deformation during the processing, maximum grain size about 50 to the scope of about 1000nm;

Leveling is also aligned described fragment; And subsequently

By described fragment is carried out single job at least, form described monolithic articles by described fragment fully, described operation is selected from and makes described fragment distortion or remove material from described fragment, the basic grain size that keeps described fragment in the described monolithic articles.

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