CN103981472B - A kind of Equal-channel Angular Pressing prepares the method for the pure titanium of Ultra-fine Grained - Google Patents
A kind of Equal-channel Angular Pressing prepares the method for the pure titanium of Ultra-fine Grained Download PDFInfo
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Abstract
A kind of Equal-channel Angular Pressing prepares the method for the pure titanium of Ultra-fine Grained, improve test conditions on the basis of existing technology, extruded sample is designed to the form that copper is wrapped in titanium rod, reduce the frictional force that in extrusion process, sample and channel contact produce, squeeze is reduced to and is no more than 150KN, improve the operability of experiment, under less squeeze, can be out of shape by Equal-channel Angular Pressing the thinning processing at room temperature completed to industrially pure titanium.Under room temperature, crystal grain seldom produces the softening phenomenon of Recovery and recrystallization when refinement, thus grain refining effect can be made remarkable, only needs the extruding of less passage just can obtain the pure titanium bulk of high strength industrial.The pure titanium of Ultra-fine Grained prepared the present invention carries out Mechanics Performance Testing to be proved, the improvement of its comprehensive mechanical property is very remarkable, and the pure titanium of block body ultrafine grain can do practical application, expands its range of application.
Description
Technical field
The present invention relates to the Technology of Plastic Processing field of material, specifically at room temperature utilize Equal-channel Angular Pressing technology to prepare the method for the pure titanium of Ultra-fine Grained.
Background technology
Titanium is due to its specific tenacity and specific rigidity is high, corrosion resistance and good and have excellent biological chemistry consistency and biomechanical compatibility, therefore gets a lot of applications in aerospace, automobile, biology and medicine and other fields.But the shortcomings such as its intensity is lower, wear resistance is poor make it apply to be restricted, and grain refining is the effective way put forward high purity titanium mechanical property, expand its range of application.
Severe plastic deformation (SeverePlasticDeformation is called for short SPD) technology is the most promising method preparing block nanometer and super fine crystal material that current international material educational circles generally acknowledges.It has strong grain refining capability, directly the microtexture of material can be refine to submicron and even nano level.The eighties in 20th century proposes a kind of Equal-channel Angular Pressing technology (EqualChannelAngularPressing by USSR (Union of Soviet Socialist Republics) scientist Segal, hereinafter referred to as ECAP), they repeatedly process material thus obtain special deformation texture to utilize this technology.After entering the nineties in 20th century, Valiev etc. find to utilize this technology effectively can like the crystal grain of polycrystalline material.The design of this technological core is that the two channels of uniform cross section diameter is handed over to cut and forms, and cross-sectional geometry is identical, completely connected according to certain angle.In extrusion process, passage will be put into the close-fitting sample of passage, and then use pressure head along channel pressings, just produce the distortion being similar to pure shear like this at sample through the passage angle of cut.Due to the geometrical feature of mould, sample can realize multi-pass extruding, thus accumulation obtains large equivalent plastic strain, and therefore crystal grain also refine to submicron even Nano grade.
There is a lot of example industrially pure titanium being carried out to ECAP thinning processing both at home and abroad.Foreign scholar mainly realizes the thinning processing of industrially pure titanium by improving extrusion temperature.The document that what S.L.Semiatin etc. delivered on " MetallurgicalsandMaterialsTransactions " be entitled as " WorkabilityofCommercial-purityTitaniumand4340SteelduringEqualChannelAngularPress ingatCold-WorkingTemperature ", the article pointed out adopted die channel filleted corner Φ=90, graphite treated lubricant is selected to do profit process, between 25 DEG C to 325 DEG C, the strain rate of 0.0021/s to 21/s is adopted to carry out ECAP deformation process to industrially pure titanium, during result room temperature 25 DEG C, adopt great extrusion speed all to fail and prepare Ultra-fine Grained industrially pure titanium, all samples are all cut off in passage corner, even become fragment, for other temperature, as the trial of 125 DEG C to 325 DEG C, due to the impact of the factor such as extrusion speed and lubricating condition, sample also shows damage in various degree.VladimirV.Stolyrov, YuntianT.Zhu etc. improve metal fluidity by raising extrusion temperature subsequently, achieve ECAP thinning processing at 400 DEG C-450 DEG C to industrially pure titanium, and final acquisition surface is without the block grained material of visible slight crack; Kim etc. also utilize ECAP method to prepare the pure titanium of Ultra-fine Grained at 200-600 DEG C.
Shanghai Communications University is disclose a kind of micro-/ nano brilliant industrially pure titanium same bending angle pressure preparation method in the innovation and creation of 200510029663.7 in the patent No., and this invention also implements ECAP distortion at 400-500 DEG C to industrially pure titanium.Raise extrusion temperature and successfully can realize ECAP distortion, thus reach the object of crystal grain thinning, but high temperature will cause grain-size to increase, make structure refinement and hydrodynamics decrease in efficiency, the distortion must carrying out more multi-pass compared with room temperature just likely reaches identical thinning effect, and high temperature deformation requires higher to moulding stock.
Be in the innovation and creation of 2008100172888, disclose a kind of high strength industrial pure titanium bulk room temperature equal-diameter bending passage deformation preparation method in the patent No., be disclose a kind of difficult-to-deformation metal block material room temperature equal-diameter bending passage deformation production method in the innovation and creation of 200910023545.3 in the patent No., in foregoing invention is created, by design extrusion mould parameter, increase passage Inner angle to 120 °, design bullnose is 20 °, improve lubricating system-employing molybdenumdisulphide and compound lubricant of graphite, and in extrusion process, utilize low-temperature annealing process to remove the very high unrelieved stress of gross distortion process.
But when using the method to prepare the pure titanium of Ultra-fine Grained, squeeze up to 300-500KN very easily causes extrusion stem unstability, extrusion stem causes squeeze sharply to rise with mould channel contact, cause extrusion stem to rupture thereupon, therefore such preparation method proposes high requirement to extrusion mould, the security existing problems of test, can not realize the batch production of the pure titanium of block body ultrafine grain.
Summary of the invention
For overcoming the excessive deficiency of the squeeze that exists in prior art, the present invention proposes a kind of method that Equal-channel Angular Pressing prepares the pure titanium of Ultra-fine Grained.
Detailed process of the present invention is:
Step 1, the preparation of copper-titanium sample:
Industrially pure titanium is made multiple titanium rod.One end of this titanium rod is cone-shaped body.Fine copper is made multiple copper rod.Tapered blind hole is had vertically in this copper rod.Described titanium rod is loaded in copper rod, is assembled into one and namely becomes copper-titanium sample that copper-clad wraps up in titanium rod, sample is placed in the inherent 300 DEG C of insulation 2h of process furnace and carries out anneal.Obtain multiple copper-titanium sample.
Step 2, the installation of extrusion mould:
Evenly compounded lubricant is applied in die channel; Two set of half mould sets are dressed up and is integrally placed on universal testing machine, and make the extrusion stem on mould coaxial with the pressure head of trier.Described compounded lubricant by 85% graphite and 15% molybdenumdisulphide formulated, described per-cent is mass percent.
Step 3, the pure titanium of Ultra-fine Grained is prepared in 4 passage extruding:
Prepare the pure titanium of Ultra-fine Grained by 4 passage extruding, and increase between 4 passages once to the anneal of copper-titanium sample.Specifically,
The pure titanium of Ultra-fine Grained is prepared in first passage extruding: be the compounded lubricant of 0.1mm at the copper obtained-titanium specimen surface uniform application thickness, copper-titanium sample is put into die channel, and by extrusion stem by copper-titanium sample press-in channel bottom, until copper-titanium sample withstands passage corner, extrusion stem indwelling is in passage.Regulate the pressure head of universal testing machine to contact with extrusion stem upper surface, and by universal testing machine, copper-titanium sample is extruded.After described copper-titanium sample is completely by the bent angle in mould, namely complete the extruding of the first passage.Copper-titanium the sample completed after a time extruding still rests in exit passageway, is ejected by first sample when putting into second copper-titanium sample and extruding, and namely completes the first time extruding preparation process of this copper-titanium sample.
The pure titanium of Ultra-fine Grained is prepared in second passage extruding: the copper-titanium sample through first time extruding is put into die channel again, and repeats the preparation process of first time extruding, completes the second time extruding preparation process to this copper-titanium sample.
Anneal: after second time has extruded, this copper titanium sample is placed in process furnace, anneal is carried out to the copper titanium sample prepared through twice extruding, to remove the unrelieved stress because large plastometric set produces, ensure that in subsequent extrusion process, larger plastix strain can not cause the cracked of sample.Anneal temperature is 200 DEG C, and soaking time is 1h.After insulation terminates, air cooling is to room temperature.
The pure titanium of Ultra-fine Grained is prepared in all the other each passage extruding: the process constantly repeating first time extruding, completes the extruding preparation process of setting, until obtain the pure titanium sample of Ultra-fine Grained.
Step 4, surface treatment: by the method for mechanical workout or the layers of copper of chemical process removal copper-titanium sample outside, obtain Ultra-fine Grained pure titanium rod material.
The present invention improves test conditions on the basis of existing technology, extruded sample is designed to the form that copper is wrapped in titanium rod, improve the operability of experiment, under less squeeze, can be out of shape by Equal-channel Angular Pressing the thinning processing at room temperature completed to industrially pure titanium.Under room temperature, crystal grain seldom produces the softening phenomenon of Recovery and recrystallization when refinement, thus grain refining effect can be made remarkable, only needs the extruding of less passage just can obtain the pure titanium bulk of high strength industrial.
Extruded sample is designed to the form that copper is wrapped in titanium rod by maximum being characterised in that of the present invention, utilize layers of copper and the less frictional coefficient of steel die interchannel, can by control squeeze at below 150KN, effectively reduce the requirement for mold material selection, also can complete under harsher experiment condition and the ECAP of industrially pure titanium is out of shape.When the present invention tests, the filleted corner of selected mould is 120 °, bullnose is 20 °, extruding route is selected to be the best Bc route of thinning effect, namely every time has extruded rear copper-titanium sample and has been rotated in a clockwise direction 90 °, and extrusion speed is 0.5mm/s-1.5mm/s.Also 90 ° of moulds and other extrusion path lines and speed can be selected to carry out material preparation.
The present invention passes through the pure titanium of the four roads extruding final acquisition flawless Ultra-fine Graineds of smooth surface, and after having extruded rear 1,2,4 passage copper-titanium samples and removal layers of copper, pure titanium rod pictorial diagram as shown in Figure 2.By SEM and its microtexture of tem observation, result display grain refining effect is remarkable.Original coarse-grain titanium average grain size is about 50um, and as shown in Figure 3, after 4 passage extruding, average grain size can reach 0.3-0.4um, as shown in Figure 4.
During extruding pure metal, die parameters Theoretical Calculation selected by the present invention, every time average plastix strain is about 0.635.By ABAQUS, the present invention is simulated, from analog result, outer wrap layers of copper affects to some extent for single pass equivalent plastic strain, but every time average plastix strain also reaches 0.5, be more or less the same with the deflection extruding separately pure metal, such 4 passage accumulated plastic strains are about 2, and plastix strain is the basic reason of grain refining, under room temperature, preparation reply is also effectively suppressed in addition, improves thin brilliant efficiency.Find in test subsequently, thinning copper layer thickness can increase the amount of plastic deformation of inner pure titanium rod, effectively improve grain refining level, the reduction of external copper thickness simultaneously can also obtain the larger ultrafine grain metal bulk of volume, expands its practical ranges.After the pure titanium of acquisition Ultra-fine Grained, utilize HVS-1000 type digital micro-analysis Vickers hardness tester, CSS44100 electronic universal tester and Hopkinson depression bar to carry out the test of a series of mechanical property.Changes in hardness is as shown in table 1, is brought up to the 2458MPa of 4 passage Ultra-fine Grained titaniums by the 1498MPa of coarse-grain titanium.The compression true stress and strain curve of the pure titanium of original coarse-grain and the pure titanium of each passage Ultra-fine Grained is as shown in accompanying drawing 6 and Fig. 7, under quasistatic and the effect of dynamic compression load, its 10% strain place stress of fluidity improves 71% and 86%, respectively according to the Hall-Petch relation σ=σ of classics
0+ kd
-1/2, the reduction of grain-size d will promote the intensity of metal effectively.This is mainly because grain-size reduces to add the volume fraction of crystal boundary in crystal, and crystal boundary also exists inhibition for the movement of dislocation, and therefore the intensity of metal can significantly improve.
The present invention on pretreatment the present invention utilizes FEM software ABAQUS to simulate ECAP deformation process, analog result shows, in the process of carrying out metallic substance Equal-channel Angular Pressing, squeeze mainly contains two portions composition, and namely test button is in the frictional force contacted with interchannel by required shearing force during bent angle and sample.Utilize finite element software simulation extrusion process can obtain the trend map of squeeze change, as shown in Figure 1, find that squeeze increases exponentially under the impact of frictional coefficient.Therefore the key of industrially pure titanium ECAP process is the problem being to solve sample and channel contact and producing frictional force.Utilize lubricant effectively can improve friction problem, but the squeeze larger when preparing agglomerate body material easily causes the destruction of lubricant film layer, thus cause lubrication failure.The present invention adopts layers of copper to wrap up the fashion of extrusion of titanium rod, utilizes layers of copper to follow the frictional coefficient that mould (steel) interchannel is very little, effectively reduces squeeze.The mode utilizing layers of copper to reduce friction in the industry is also widely used in the process such as the drawing of pure titanium.The simultaneously copper extruding that also has good intensity can carry out repeatedly, therefore can realize the multi-pass thinning processing of industrially pure titanium.
The ECAP process of usual metal needs the extruding through multi-pass, is reached the large plastometric set of metal by the accumulation of plastix strain, thus crystal grain thinning.As shown in Fig. 2 .a, obtained the copper-titanium sample once extruded from exit passageway after, need to place back in access road along the original direction of extrusion and carry out second time extruding, extruding so repeatedly thus complete large plastometric set.But due to Outlet Passage Diameter identical with access road diameter, and external copper is softer, after completing once extruding, copper-titanium sample external diameter becomes identical with channel size, therefore copper-titanium sample is not easy again to put access road into, therefore need to polish to copper-titanium specimen surface, enable this copper-titanium sample put into die entrance channel interior and again extrude.
The process repeating the 1st passage ECAP deformation process can complete the multi-pass extruding of pure titanium.Finite element analogy result shows, and completes an extrusion process equivalent plastic strain and is about 0.5, and the present invention completes 4 passage extruding altogether, and accumulation equivalent plastic strain is about 2.Reader according to the experiment purpose of oneself, can need complete great distortion to carry out the estimation of extrusion passes, but the extruding of unsuitable too much number of times, excessive viscous deformation easily causes the cracked of sample.Do not need after last extruding completes to carry out grinding process.
After the second passage has extruded, sample is placed in the present invention in process furnace and carries out anneal at 200 DEG C of insulation 1h, remove the unrelieved stress because large plastometric set produces, ensure that in subsequent extrusion process, larger plastix strain can not cause the cracked of sample.Can see that in previous literature every time is all annealed or the direct situation such as unannealed, but too much annealing can reduce the efficiency of grain refining, and unannealedly be difficult to the preparation ensureing complete grained material.The present invention selects to carry out a low-temperature annealing between middle 4 passages, effectively improves success ratio prepared by sample.
In sum, the present invention reduces by copper-titanium sample the frictional force that in extrusion process, sample and channel contact produce, effectively reduce squeeze, maximum extrusion pressure is no more than 150KN, like this can under usual experiment condition the pure titanium of large batch of production Ultra-fine Grained, found by follow-up Mechanics Performance Testing experiment, the comprehensive mechanical property improvement that the present invention prepares Ultra-fine Grained bulk is very remarkable, the pure titanium of block body ultrafine grain can do practical application, expands its range of application.
Table 1 is the pure titanium changes in hardness of each passage Ultra-fine Grained
| Different passage | Hv(MPa) |
| 0pass | 1498 |
| 1pass | 2036 |
| 2pass | 2289 |
| 4pass | 2458 |
Accompanying drawing explanation
Fig. 1 utilizes finite element software ABAQUS to simulate having friction and the time dependent trend map of squeeze size wrapping up in titanium rod sample without ECAP process copper-clad under friction condition; In figure, 1 indicates that friction, 2 indicates without friction.
Fig. 2 be the pure titanium ECAP of the present invention be out of shape adopt half module and the extrusion stem schematic diagram of mould, wherein 2a is the structural representation of half module, and 2b is the structural representation of extrusion stem.
Fig. 3 is that four-pass has extruded rear 1,2,4 passage copper-titanium samples and pure titanium rod pictorial diagram after removing layers of copper, wherein I in Fig. 3 a is the copper-titanium sample not yet removing external copper after 1 passage extruding, II is the copper-titanium sample not yet removing external copper after 2 passage extruding, and III is the copper-titanium sample not yet removing external copper after 4 passage extruding.In figure, 3b, 3c and 3d remove the pictorial diagram of inner pure titanium rod after external copper after being respectively 1,2 and 4 passages extruding.
Fig. 4 is that SEM observes the pure titanium micro-structure diagram of original coarse-grain;
Fig. 5 is the micro-structure diagram that tem observation 4 passage has extruded the pure titanium of rear Ultra-fine Grained, and wherein, 5a is TEM light field shooting results, and 5b is details in a play not acted out on stage, but told through dialogues shooting results;
Fig. 6 is the pure titanium of original coarse-grain and the rear Ultra-fine Grained pure titanium quasistatic compression mechanical property of 1,2,4 passages extruding; In figure: 1. original coarse-grain pure titanium quasistatic compression stress-strain curve; 2. the quasistatic compression true stress and strain curve of the rear pure titanium of Ultra-fine Grained of the 1st passage extruding; 3. the quasistatic compression true stress and strain curve of the rear pure titanium of Ultra-fine Grained of the 2nd passage extruding; 4. the quasistatic compression true stress and strain curve of the rear pure titanium of Ultra-fine Grained of the 4th passage extruding;
Fig. 7 is the pure titanium of original coarse-grain and the rear Ultra-fine Grained pure titanium mechanical dynamic compression property performance of 1,2,4 passages extruding, in figure: 5. original thick pure titanium dynamic compressing stress-strain curve; 6. the dynamic compression true stress and strain curve of the rear pure titanium of Ultra-fine Grained of the 1st passage extruding; 7. the dynamic compression true stress and strain curve of the rear pure titanium of Ultra-fine Grained of the 2nd passage extruding; 8. the dynamic compression true stress and strain curve of the rear pure titanium of Ultra-fine Grained of the 4th passage extruding;
Fig. 8 is schema of the present invention.
Embodiment
The present embodiment is a kind of method that under room temperature, Equal-channel Angular Pressing prepares the pure titanium of Ultra-fine Grained, is that to adopt be at room temperature successfully prepare the method for the pure titanium of Ultra-fine Grained based on Equal-channel Angular Pressing technology.The described full name based on Equal-channel Angular Pressing technology is EqualChannelAngularPressing, is called for short ECAP, at room temperature can successfully prepares the pure titanium of Ultra-fine Grained.
Provide the entire protocol of concrete implementation and operation below, at room temperature can obtain the pure titanium of Ultra-fine Grained according to following steps.
Embodiment 1
The mould that the present embodiment uses adopts prior art, comprises two half modules, extrusion stem and some bolts, as shown in figures 2 a and 2b.Smear one deck compounded lubricant uniformly in channel interior before extruding, and extrusion stem is put into channel interior, such extrusion stem can play the effect of location, and when preventing from installing, two portions half module misplaces; Then be fitted together by the set of half mould sets of bolt by two portions symmetry, form complete mould, passage interior angle is 120 °, bullnose is 20 °.The Bc route that extrusion path line selection thinning effect is best, namely every time puts access road into after extruded sample being rotated clockwise 90 ° after having extruded again; What adjust universal testing machine crossbeam moves down speed, and extrusion stem is moved down along passage with 0.5 ~ 1.5mm/s speed.In the present embodiment, the speed that moves down of extrusion stem is 0.5mm/s.
The present embodiment operates at normal temperatures.
The detailed process of the present embodiment is:
Step 1, the preparation of copper-titanium sample:
Industrial pure titanium TA2 hot rolled plate is cut into length is 60mm, diameter is the right cylinder of 5mm, makes titanium rod.One end of this titanium rod is cone-shaped body.
By the right cylinder of fine copper cutting processing growth 80mm, diameter 10mm, make copper rod.In this copper rod, be processed with that diameter is 5mm, the degree of depth is the tapered blind hole of 60mm vertically.This tapered blind hole is coaxial with described copper rod.In this example to process angle of taper be 90 °.
Described titanium rod is loaded in copper rod, is assembled into one and namely becomes copper-titanium sample that copper-clad wraps up in titanium rod, sample is placed in the inherent 300 DEG C of insulation 2h of process furnace and carries out anneal.Obtain copper-titanium sample.This example is by above-mentioned steps processing sample 10 altogether, and reader can determine sample processing quantity as required.
Step 2, extrusion mould is assembled:
In die channel uniform application thickness be 85% graphite+15% molybdenumdisulphide compounded lubricant of 0.1mm to lubricate this die channel, the ratio of described compounded lubricant is mass percent.Two set of half mould sets bolts are assembled into and are integrally placed on 60t universal testing machine, and make the extrusion stem on mould coaxial with the pressure head of trier.
Step 3, the pure titanium of Ultra-fine Grained is prepared in multi-pass extruding:
The present embodiment prepares the pure titanium of Ultra-fine Grained by 4 passage extruding, and increases between 4 passages once to the anneal of copper-titanium sample.Specifically,
The pure titanium of Ultra-fine Grained is prepared in first passage extruding: be the compounded lubricant of 0.1mm at the copper obtained-titanium specimen surface uniform application thickness, copper-titanium sample is put into die channel, with extrusion stem by copper-titanium sample press-in channel bottom, until copper-titanium sample withstands passage corner, extrusion stem indwelling is in passage.The pressure head of universal testing machine is regulated to contact with extrusion stem upper surface.Adjustment Tests machine crossbeam lowering speed, extrudes copper-titanium sample with the speed of 0.5mm/s.After described copper-titanium sample is completely by the bent angle in mould, namely complete the extruding of the first passage.Copper-titanium the sample completed after a time extruding still rests in exit passageway, is ejected by first sample when putting into second copper-titanium sample and extruding, and namely completes the first time extruding preparation process of this copper-titanium sample.
The pure titanium of Ultra-fine Grained is prepared in second passage extruding: the copper-titanium sample through first time extruding is put into die channel again, and repeats the preparation process of first time extruding, completes the second time extruding preparation process to this copper-titanium sample.
Anneal: after second time has extruded, this copper titanium sample is placed in process furnace, anneal is carried out to the copper titanium sample prepared through twice extruding, to remove the unrelieved stress because large plastometric set produces, ensure that in subsequent extrusion process, larger plastix strain can not cause the cracked of sample.Anneal temperature is 200 DEG C, and soaking time is 1h.After insulation terminates, air cooling is to room temperature.
Because too much annealing can reduce the efficiency of grain refining, and the unannealed preparation being difficult to the complete grained material of guarantee, therefore the present embodiment is being selected to prepare in the process of the pure titanium of Ultra-fine Grained in multi-pass extruding to carry out anneal.
The pure titanium of Ultra-fine Grained is prepared in all the other each passage extruding: the process constantly repeating first time extruding, completes the extruding preparation process of setting, until obtain the pure titanium sample of Ultra-fine Grained.
Step 4, surface treatment: by the method for mechanical workout or the layers of copper of chemical process removal copper-titanium sample outside, obtain Ultra-fine Grained pure titanium rod material.The present embodiment adopts turning mode to carry out surface working to the pure titanium sample of the Ultra-fine Grained obtained.
The microtexture of the pure titanium of Ultra-fine Grained obtained by SEM, tem observation the present embodiment, after 4 passages extruding, the average grain size of the pure titanium of gained Ultra-fine Grained reaches 0.3 ~ 0.4um, effectively refinement crystal grain.Digital Vickers hardness tester, universal testing machine and Hopkinson bar is utilized to carry out Mechanics Performance Testing, after result display thinning processing, the mechanical property of material is greatly improved, and hardness brings up to the 2458MPa of 4 passage Ultra-fine Grained titaniums by the 1498MPa of coarse-grain titanium.Compared to the pure titanium of original coarse-grain, the pure titanium of 4 passage Ultra-fine Grained its 10% strain place stress of fluidity under the effect of quasistatic compression load rises to 813MPa by 475MPa; Under Dynamic Loading, its 10% strain place stress of fluidity rises to 1215MPa by 652MPa, improves 71% and 86% respectively.
Embodiment 2
Mould selected by the present embodiment is passage angle is 120 °, bullnose is the mould of the two-half die composition of 20 °, the Bc route that extrusion path line selection thinning effect is best, namely every time puts access road into after extruded sample being rotated clockwise 90 ° after having extruded again; It is 0.5mm/s that extrusion stem moves down speed along passage, and adjustment universal testing machine crossbeam moves down speed and can control.The present embodiment operates at normal temperatures.
The detailed process of the present embodiment is:
Step 1, the preparation of copper-titanium sample:
Industrial pure titanium TA2 hot rolled plate is cut into length is 70mm, diameter is the right cylinder of 8mm, makes titanium rod.One end of this titanium rod is cone-shaped body.
By the right cylinder of fine copper cutting processing growth 80mm, diameter 10mm, make copper rod.In this copper rod, be processed with that diameter is 8mm, the degree of depth is the tapered blind hole of 70mm vertically.This tapered blind hole is coaxial with described copper rod.In this example to process angle of taper be 120 °.
The effect that peripheral layers of copper of the present invention plays reduces extruded sample with the friction between squeezing passage, effectively reduces squeeze, thus improve the property prepared under the pure titanium room ambient conditions of Ultra-fine Grained.The change of external copper thickness will have influence on the accumulation of inner pure titanium rod viscous deformation, and external copper is thinning makes inner pure titanium rod obtain larger distortion when every time extrudes, thus grain refining effect is more obvious, and mechanical property has larger improvement.Meanwhile, the thinning external copper thickness pure titanium of Ultra-fine Grained that can obtain more volume.
In addition, tapered blind hole interior tapered angle in copper rod is changed in this example, according to the analysis of ABAQUS finite element analogy result, the extruded sample change that different angle of taper will cause inner pure titanium rod front end with outside tapered blind hole interior side contacts state in the process of extruding, excessive cone angle easily produces being separated of pure titanium rod front end and copper rod tapered blind hole front end after repeatedly extruding, easily chipping after pure titanium rod repeatedly extrudes.
Described titanium rod is loaded in copper rod, is assembled into one and namely becomes copper-titanium sample that copper-clad wraps up in titanium rod, sample is placed in the inherent 300 DEG C of insulation 2h of process furnace and carries out anneal.Obtain copper-titanium sample.This example is by above-mentioned steps processing sample 10 altogether, and reader can determine sample processing quantity as required.
Step 2, extrusion mould is assembled:
In die channel uniform application thickness be 85% graphite+15% molybdenumdisulphide compounded lubricant of 0.1mm to lubricate this die channel, the ratio of described compounded lubricant is mass percent.Two set of half mould sets bolts are assembled into and are integrally placed on 60t universal testing machine, and make the extrusion stem on mould coaxial with the pressure head of trier.
Step 3, the pure titanium of Ultra-fine Grained is prepared in multi-pass extruding:
The present embodiment prepares the pure titanium of Ultra-fine Grained by 4 passage extruding, and increases between 4 passages once to the anneal of copper-titanium sample.Specifically,
The pure titanium of Ultra-fine Grained is prepared in first passage extruding: be the compounded lubricant of 0.1mm at the copper obtained-titanium specimen surface uniform application thickness, copper-titanium sample is put into die channel, with extrusion stem by copper-titanium sample press-in channel bottom, until copper-titanium sample withstands passage corner, extrusion stem indwelling is in passage.The pressure head of universal testing machine is regulated to contact with extrusion stem upper surface.Adjustment universal testing machine crossbeam move down speed, extrusion stem to be moved down with 0.5 ~ 1.5mm/s speed along passage copper-titanium sample is extruded.In the present embodiment, the speed that moves down of extrusion stem is 1.0mm/s.
After described copper-titanium sample is completely by the bent angle in mould, namely complete the extruding of the first passage.Copper-titanium the sample completed after a time extruding still rests in exit passageway, is ejected by first sample when putting into second copper-titanium sample and extruding, and namely completes the first time extruding preparation process of this copper-titanium sample.
The pure titanium of Ultra-fine Grained is prepared in second passage extruding: the copper-titanium sample through first time extruding is put into die channel again, and repeats the preparation process of first time extruding, completes the second time extruding preparation process to this copper-titanium sample.
Anneal: after second time has extruded, this copper titanium sample is placed in process furnace, anneal is carried out to the copper titanium sample prepared through twice extruding, to remove the unrelieved stress because large plastometric set produces, ensure that in subsequent extrusion process, larger plastix strain can not cause the cracked of sample.Anneal temperature is 200 DEG C, and soaking time is 1h.After insulation terminates, air cooling is to room temperature.
Because too much annealing can reduce the efficiency of grain refining, and the unannealed preparation being difficult to the complete grained material of guarantee, therefore the present embodiment is being selected to prepare in the process of the pure titanium of Ultra-fine Grained in multi-pass extruding to carry out anneal.
The pure titanium of Ultra-fine Grained is prepared in all the other each passage extruding: the process constantly repeating first time extruding, completes the extruding preparation process of setting, until obtain the pure titanium sample of Ultra-fine Grained.
Step 4, surface treatment: by the method for mechanical workout or the layers of copper of chemical process removal copper-titanium sample outside, obtain Ultra-fine Grained pure titanium rod material.The present embodiment adopts turning mode to carry out surface working to the pure titanium sample of the Ultra-fine Grained obtained.
Embodiment 3
Mould selected by the present embodiment is passage angle is 90 °, and bullnose is the mould of the two-half die composition of 30 °.Die channel angle and bullnose affect extruded sample every time has extruded the important parameter of after strain amount size, reduces passage angle and effectively can increase every time extruded sample amount of plastic deformation, increase bullnose and sample can be made easier to pass through bent angle.The Bc route that extrusion path line selection thinning effect is best, namely every time puts access road into after extruded sample being rotated clockwise 90 ° after having extruded again; It is 1.5mm/s that extrusion stem moves down speed along passage, and adjustment universal testing machine crossbeam moves down speed and can control.The present embodiment operates at normal temperatures.
The detailed process of the present embodiment is:
Step 1, the preparation of copper-titanium sample:
Industrial pure titanium TA2 hot rolled plate is cut into length is 70mm, diameter is the right cylinder of 8mm, makes titanium rod.One end of this titanium rod is cone-shaped body.
By the right cylinder of fine copper cutting processing growth 80mm, diameter 10mm, make copper rod.In this copper rod, be processed with that diameter is 8mm, the degree of depth is the tapered blind hole of 70mm vertically.This tapered blind hole is coaxial with described copper rod.In this example to process angle of taper be 90 °.
Described titanium rod is loaded in copper rod, is assembled into one and namely becomes copper-titanium sample that copper-clad wraps up in titanium rod, sample is placed in the inherent 300 DEG C of insulation 2h of process furnace and carries out anneal.Obtain copper-titanium sample.This example is by above-mentioned steps processing sample 10 altogether, and reader can determine sample processing quantity as required.
Step 2, extrusion mould is assembled:
In die channel uniform application thickness be 85% graphite+15% molybdenumdisulphide compounded lubricant of 0.1mm to lubricate this die channel, the ratio of described compounded lubricant is mass percent.Two set of half mould sets bolts are assembled into and are integrally placed on 60t universal testing machine, and make the extrusion stem on mould coaxial with the pressure head of trier.
Step 3, the pure titanium of Ultra-fine Grained is prepared in 4 passage extruding:
The present embodiment prepares the pure titanium of Ultra-fine Grained by 4 passage extruding, and increases between 4 passages once to the anneal of copper-titanium sample.Specifically:
The pure titanium of Ultra-fine Grained is prepared in first passage extruding: be the compounded lubricant of 0.1mm at the copper obtained-titanium specimen surface uniform application thickness, copper-titanium sample is put into die channel, with extrusion stem by copper-titanium sample press-in channel bottom, until copper-titanium sample withstands passage corner, extrusion stem indwelling is in passage.The pressure head of universal testing machine is regulated to contact with extrusion stem upper surface.Adjustment Tests machine crossbeam lowering speed, extrudes copper-titanium sample with the speed of 1.5mm/s.After described copper-titanium sample is completely by the bent angle in mould, namely complete the extruding of the first passage.Copper-titanium the sample completed after a time extruding still rests in exit passageway, is ejected by first sample when putting into second copper-titanium sample and extruding, and namely completes the first time extruding preparation process of this copper-titanium sample.
The pure titanium of Ultra-fine Grained is prepared in second passage extruding: the copper-titanium sample through first time extruding is put into die channel again, and repeats the preparation process of first time extruding, completes the second time extruding preparation process to this copper-titanium sample.
Anneal: after second time has extruded, this copper titanium sample is placed in process furnace, anneal is carried out to the copper titanium sample prepared through twice extruding, to remove the unrelieved stress because large plastometric set produces, ensure that in subsequent extrusion process, larger plastix strain can not cause the cracked of sample.Anneal temperature is 200 DEG C, and soaking time is 1h.After insulation terminates, air cooling is to room temperature.
Because too much annealing can reduce the efficiency of grain refining, and the unannealed preparation being difficult to the complete grained material of guarantee, therefore the present embodiment is being selected to prepare in the process of the pure titanium of Ultra-fine Grained in multi-pass extruding to carry out anneal.
The pure titanium of Ultra-fine Grained is prepared in all the other each passage extruding: the process constantly repeating first time extruding, completes the extruding preparation process of setting, until obtain the pure titanium sample of Ultra-fine Grained.
Step 4, surface treatment: by the method for mechanical workout or the layers of copper of chemical process removal copper-titanium sample outside, obtain Ultra-fine Grained pure titanium rod material.The present embodiment adopts turning mode to carry out surface working to the pure titanium sample of the Ultra-fine Grained obtained.
Claims (2)
1. Equal-channel Angular Pressing prepares a method for the pure titanium of Ultra-fine Grained, it is characterized in that, detailed process is:
Step 1, the preparation of copper-titanium sample:
Industrially pure titanium is made multiple titanium rod; One end of this titanium rod is cone-shaped body; Fine copper is made multiple copper rod; Tapered blind hole is had vertically in this copper rod; Described titanium rod is loaded in copper rod, is assembled into one and namely becomes copper-titanium sample that copper-clad wraps up in titanium rod, sample is placed in the inherent 300 DEG C of insulation 2h of process furnace and carries out anneal, to remove unrelieved stress; Obtain multiple copper-titanium sample;
Step 2, the installation of extrusion mould:
Evenly compounded lubricant is applied in die channel; Two set of half mould sets are dressed up and is integrally placed on universal testing machine, and make the extrusion stem on mould coaxial with the pressure head of trier; The passage angle of described mould is 90 °, and the bullnose of described mould is 30 °; Or the passage angle of described mould is 120 °, the bullnose of described mould is 20 °;
Step 3, the pure titanium of Ultra-fine Grained is prepared in four-pass extruding:
Prepare the pure titanium of Ultra-fine Grained by four-pass extruding, and increase once to the anneal of copper-titanium sample between four-pass; Specifically,
The pure titanium of Ultra-fine Grained is prepared in first passage extruding: be the compounded lubricant of 0.1mm at the copper obtained-titanium specimen surface uniform application thickness, copper-titanium sample is put into die channel, and by extrusion stem by copper-titanium sample press-in channel bottom, until copper-titanium sample withstands passage corner, extrusion stem indwelling is in passage; Regulate the pressure head of universal testing machine to contact with extrusion stem upper surface, and extruded copper-titanium sample by universal testing machine, extrusion speed is 0.1 ~ 1.5mm/s; After described copper-titanium sample is completely by the bent angle in mould, namely complete the extruding of the first passage; Copper-titanium the sample completed after a time extruding still rests in exit passageway, is ejected by first sample when putting into second copper-titanium sample and extruding, and namely completes the first time extruding preparation process of this copper-titanium sample; The pure titanium of Ultra-fine Grained is prepared in second passage extruding: the copper-titanium sample through first time extruding is put into die channel again, and repeats the preparation process of first time extruding, completes the second time extruding preparation process to this copper-titanium sample; Anneal: after second time has extruded, this copper titanium sample is placed in process furnace, anneal is carried out to the copper titanium sample prepared through twice extruding, to remove the unrelieved stress because large plastometric set produces, ensure that in subsequent extrusion process, larger plastix strain can not cause the cracked of sample; Anneal temperature is 200 DEG C, and soaking time is 1h; After insulation terminates, air cooling is to room temperature;
The pure titanium of Ultra-fine Grained is prepared in all the other each passage extruding: the process constantly repeating first time extruding, completes the extruding preparation process of setting, until obtain the pure titanium sample of Ultra-fine Grained; Step 4, surface treatment: by the mode of turning or the layers of copper of chemical process removal copper-titanium sample outside, obtain Ultra-fine Grained pure titanium rod material.
2. Equal-channel Angular Pressing prepares the method for the pure titanium of Ultra-fine Grained as claimed in claim 1, it is characterized in that, described compounded lubricant by 85% graphite and 15% molybdenumdisulphide formulated, described per-cent is mass percent.
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| CN106333754B (en) * | 2016-09-21 | 2017-11-17 | 中国人民解放军第四军医大学 | A kind of pure titanium oral cavity micro-implant of Ultra-fine Grained and preparation method thereof |
| CN107123466A (en) * | 2017-04-27 | 2017-09-01 | 西北有色金属研究院 | A kind of high-strength high conductivity low-density copper-clad titanium composite contact wire and preparation method thereof |
| CN107881447B (en) * | 2017-11-22 | 2019-04-23 | 四川大学 | A kind of pure titanium of high-strength tenacity filiform crystal grain and preparation method thereof |
| CN110295334B (en) * | 2019-07-16 | 2020-11-24 | 常州大学 | Preparation method of high-strength high-plasticity industrial pure titanium with multi-level structure |
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