CN103981472A - Preparation method for ultra-fine grain pure titanium through equal channel angular pressing - Google Patents
Preparation method for ultra-fine grain pure titanium through equal channel angular pressing Download PDFInfo
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Abstract
The invention provides a preparation method for ultra-fine grain pure titanium through equal channel angular pressing. According to the invention, test conditions are improved on the basis of the prior art, a to-be-extruded sample is designed to be a copper-wrapped titanium rod, so frictional force generated during contact between the sample and a channel is reduced during extruding; extruding force is decreased to no more than 150 KN, so experimental operability is improved, and refining of industrial pure titanium can be finished at room temperature under small extruding force through equal channel angular pressing. At room temperature, the phenomena of restoring and recrystallization softening of crystal grains during refining hardly occur, so a substantial crystal grain refining effect is obtained and a high-strength industrial pure titanium block can be obtained through few times of extruding. According to results of testing of mechanical properties of the prepared ultra-fine grain pure titanium, the ultra-fine grain pure titanium has substantially improved comprehensive mechanical properties, block ultra-fine grain pure titanium can be used in practice, and the application scope of the ultra-fine grain pure titanium is broadened.
Description
Technical field
The present invention relates to the Technology of Plastic Processing field of material, specifically at room temperature utilize during 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 are restricted its application, and grain refining is the effective way of putting forward high purity titanium mechanical property, expanding its range of application.
Severe plastic deformation (Severe Plastic Deformation is called for short SPD) technology is the generally acknowledged the most promising method of preparing block nanometer and super fine crystal material of current international material educational circles.It has strong grain refining capability, can directly the microtexture of material be refine to submicron and even nano level.Propose a kind of during Equal-channel Angular Pressing technology (Equal Channel Angular Pressing by USSR (Union of Soviet Socialist Republics) scientist Segal the eighties in 20th century, hereinafter to be referred as ECAP), thereby utilize this technology, they repeatedly process and obtain special deformation texture material.Enter after the nineties in 20th century, the discoveries such as Valiev utilize this technology can effectively like the crystal grain of polycrystalline material.This technological core design is that the two channels friendship section of uniform cross section diameter forms, and cross-sectional geometry is identical, completely connected according to certain angle.In extrusion process, will put into passage with the close-fitting sample of passage, then push along passage with pressure head, in the time of the sample process passage angle of cut, just produce like this distortion that is similar to pure shear.Due to the geometrical feature of mould, sample can be realized multi-pass extruding, thereby accumulation obtains large equivalent plastic strain, and therefore crystal grain also refine to even Nano grade of submicron.
There is the example that much industrially pure titanium is carried out ECAP thinning processing both at home and abroad.Foreign scholar is mainly the thinning processing that realizes industrially pure titanium by improving extrusion temperature.The document that what S.L.Semiatin etc. delivered on " Metallurgicals and Materials Transactions " be entitled as " Workability of Commercial-purity Titanium and4340Steel during Equal Channel Angular Pressing at Cold-Working Temperature ", the article pointed out adopted die channel filleted corner Φ=90, selecting graphite treated lubricant to make profit processes, between 25 DEG C to 325 DEG C, adopt 0.0021/s, to the strain rate of 21/s, industrially pure titanium is carried out to ECAP deformation process, when 25 DEG C of result room temperatures, 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.Vladimir V.Stolyrov subsequently, Yuntian T.Zhu etc. improves metal fluidity by rising extrusion temperature, at 400 DEG C-450 DEG C, industrially pure titanium has been realized to ECAP thinning processing, the final block grained material of surface without visible slight crack that obtain; Kim etc. also utilize ECAP method to prepare the pure titanium of Ultra-fine Grained at 200-600 DEG C.
In the innovation and creation that Shanghai Communications University is 200510029663.7 in the patent No., disclose the isometrical bent angle extruding production of the brilliant industrially pure titanium of a kind of micro-/ nano, this invention is also implemented ECAP distortion at 400-500 DEG C to industrially pure titanium.Rising extrusion temperature can successfully be realized ECAP distortion, thereby reach the object of crystal grain thinning, but high temperature will cause grain-size to increase, make structure refinement and hydrodynamics decrease in efficiency, compare with room temperature and must carry out the more distortion of multi-pass and just likely reach identical thinning effect, and high temperature deformation requires higher to moulding stock.
The pure titanium bulk of a kind of high strength industrial room temperature equal-diameter bending passage deformation preparation method is disclosed in the innovation and creation that are 2008100172888 in the patent No., a kind of difficult-to-deformation metal block material room temperature equal-diameter bending passage deformation production method is disclosed in the innovation and creation that are 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 to process and remove the very high unrelieved stress of gross distortion process.
But while 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 die channel contact, cause extrusion stem fracture thereupon, therefore such preparation method has proposed 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 squeeze existing in prior art, the present invention proposes a kind of method that during Equal-channel Angular Pressing is prepared 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 to multiple titanium rods.One end of this titanium rod is cone-shaped body.Fine copper is made to multiple copper rods.In this copper rod, there is vertically tapered blind hole.Described titanium rod is packed in copper rod, be assembled into one and become copper-clad and wrapping up in copper-titanium sample of titanium rod, sample is placed in to the inherent 300 DEG C of insulation 2h of process furnace and carries out anneal.Obtain multiple copper-titanium samples.
Step 2, the installation of extrusion mould:
In die channel, evenly apply compounded lubricant; Two set of half mould sets are dressed up to one and be placed on universal testing machine, and make the extrusion stem on mould coaxial with the pressure head of trier.Described compounded lubricant is formulated by 85% graphite and 15% molybdenumdisulphide, and 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 the once anneal to copper-titanium sample between 4 passages.Specifically,
The pure titanium of Ultra-fine Grained is prepared in the first passage extruding: the compounded lubricant that is 0.1mm at the even smearing thickness of copper-titanium specimen surface obtaining, copper-titanium sample is put into die channel, and by extrusion stem, copper-titanium sample is pressed into 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 pushed.After described copper-titanium sample is completely by the bent angle in mould, complete the extruding of the first passage.Copper-titanium the sample completing after a time extruding still rests in exit passageway, when putting into when second copper-titanium sample pushes, first sample is ejected, and completes the extruding preparation process for the first time of this copper-titanium sample.
The pure titanium of Ultra-fine Grained is prepared in the second passage extruding: will again put into die channel through copper-titanium sample of extruding for the first time, and the preparation process that repeats to push for the first time, complete the extruding preparation process for the second time to this copper-titanium sample.
Anneal: after having pushed for the second time, this copper titanium sample is placed in process furnace, the copper titanium sample of preparing through twice extruding is carried out to anneal, to remove the unrelieved stress producing due to large plastometric set, ensure that plastix strain larger in follow-up extrusion process can not cause the cracked of sample.Anneal temperature is 200 DEG C, and soaking time is 1h.After insulation finishes, air cooling is to room temperature.
The pure titanium of Ultra-fine Grained is prepared in all the other each passages extruding: constantly repeat the process of pushing for the first time, complete the extruding preparation process of setting, until obtain the pure titanium sample of Ultra-fine Grained.
Step 4, surface treatment: method or chemical process by mechanical workout are removed the copper layer of copper-titanium sample outside, obtain Ultra-fine Grained pure titanium rod material.
The present invention has improved test conditions on the basis of existing technology, extruded sample is designed to copper and is wrapped in the form of titanium rod, improve the operability of experiment, can under less squeeze, be out of shape by during Equal-channel Angular Pressing the thinning processing at room temperature completing industrially pure titanium.Under room temperature, crystal grain seldom produces the softening phenomenon of Recovery and recrystallization in the time of refinement, thereby can make grain refining effect remarkable, only needs the extruding of less passage just can obtain the pure titanium bulk of high strength industrial.
Maximum of the present invention is characterised in that the form that extruded sample is designed to copper and is wrapped in titanium rod, utilize the frictional coefficient that copper layer and steel die interchannel are less, can will control squeeze below 150KN, effectively reduce the requirement for mold material selection, also can under harsher experiment condition, complete the ECAP distortion to industrially pure titanium.When the present invention tests, the filleted corner of selected mould is that 120 °, bullnose are 20 °, selecting extruding route is the best Bc route of thinning effect, be that after every time extruding completes, copper-titanium sample is rotated in a clockwise direction 90 °, extrusion speed is 0.5mm/s-1.5mm/s.Also can select 90 ° of moulds and other extrusion path lines and speed to carry out material preparation.
The present invention is by the final pure titanium of the flawless Ultra-fine Grained of smooth surface that obtains of four road extruding, and after having pushed rear 1,2,4 passage copper-titanium samples and having removed copper layer, pure titanium rod pictorial diagram as shown in Figure 2.By SEM and its microtexture of tem observation, result shows that 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.
When extruding pure metal, according to the present invention, selected die parameters Theoretical Calculation is known, and every time average plastix strain is about 0.635.By ABAQUS, the present invention is simulated, from analog result, outer wrap copper layer 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 of independent extruding 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, has improved thin brilliant efficiency.In test subsequently, find, attenuate copper layer thickness can increase the amount of plastic deformation of inner pure titanium rod, effectively improve grain refining level, simultaneously outside copper layer thickness reduce can also obtain the ultrafine grain metal bulk that volume is larger, expand 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 properties.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 dynamic compression load, its 10% strain place stress of fluidity has promoted respectively 71% and 86%, is related to σ=σ according to classical Hall-Petch
0+ kd
-1/2, the reducing of grain-size d will promote the intensity of metal effectively.This is mainly because grain-size has reduced to increase the volume fraction of crystal boundary in crystal, and crystal boundary exists inhibition for the movement of dislocation, and therefore the intensity of metal can significantly improve.
The present invention the present invention before experiment utilizes FEM software ABAQUS to simulate ECAP deformation process, analog result shows, carrying out in the process of metallic substance during Equal-channel Angular Pressing, squeeze mainly contains two portions compositions, the frictional force that test button required shearing force and sample when by bent angle contacts with interchannel.Utilize finite element software simulation extrusion process can obtain the trend map that squeeze changes, as shown in Figure 1, find that squeeze increases exponentially under the impact of frictional coefficient.Therefore the key that industrially pure titanium ECAP processes is to be to solve that sample contacts with passage and the problem that produces frictional force.Utilize lubricant can effectively improve friction problem, but larger squeeze easily causes the destruction of lubricant film layer in the time preparing agglomerate body material, thereby cause lubrication failure.The present invention adopts the fashion of extrusion of copper layer parcel titanium rod, utilizes copper layer with the very little frictional coefficient of mould (steel) interchannel, effectively reduces squeeze.The mode of utilizing copper layer to reduce friction in industry is also widely used in the processing such as the drawing of pure titanium.Copper also has good intensity can carry out extruding repeatedly simultaneously, therefore can realize the multi-pass thinning processing of industrially pure titanium.
Conventionally the ECAP of metal processes and need to, through the extruding of multi-pass, reach the large plastometric set of metal by the accumulation of plastix strain, thus crystal grain thinning.As shown in Fig. 2 .a, from exit passageway has obtained copper-titanium sample of once extruding, need to again put back to access road along the original direction of extrusion and push for the second time, thereby extruding so repeatedly completes large plastometric set.But because exit passageway diameter is identical with access road diameter, and outside copper layer is softer, become identical with channel size completing once copper-titanium sample external diameter after extruding, therefore copper-titanium sample is not easy again to put into access road, therefore need copper-titanium specimen surface to polish, make this copper-titanium sample can put into die entrance channel interior and again push.
The process that repeats the 1st passage ECAP deformation process can complete the multi-pass extruding of pure titanium.Finite element analogy result shows, completes an extrusion process equivalent plastic strain and is about 0.5, and the present invention has completed 4 passage extruding altogether, and accumulation equivalent plastic strain is about 2.Reader can be according to the experiment purpose of oneself, and need complete great distortion and carry out the estimation of extrusion passes, but the unsuitable too much extruding of number of times, excessive viscous deformation easily causes the cracked of sample.After last extruding, do not need to carry out grinding process.
In the present invention, after the second passage has been pushed, sample is placed in process furnace and carries out anneal at 200 DEG C of insulation 1h, remove the unrelieved stress producing due to large plastometric set, ensure that plastix strain larger in follow-up extrusion process can not cause the cracked of sample.In previous literature, can see that every time all anneals or the direct situation such as unannealed, but too much annealing can reduce the efficiency of grain refining, and the unannealed preparation that is difficult to ensure complete grained material.In the middle of the present invention is chosen in, between 4 passages, carry out low-temperature annealing one time, effectively improved success ratio prepared by sample.
In sum, the present invention has reduced sample in extrusion process by copper-titanium sample and has contacted the frictional force producing with passage, effectively reduce squeeze, maximum extrusion pressure is no more than 150KN, can, at the pure titanium of large batch of production Ultra-fine Grained under common experiment condition, find by follow-up Mechanics Performance Testing experiment like this, it is very remarkable that the present invention prepares the comprehensive mechanical property improvement of Ultra-fine Grained bulk, 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 passages | Hv(MPa) |
| 0pass | 1498 |
| 1pass | 2036 |
| 2pass | 2289 |
| 4pass | 2458 |
Brief description of the drawings
Fig. 1 utilizes finite element software ABAQUS simulation having friction and the time dependent trend map of squeeze size of wrapping up in titanium rod sample without ECAP processing copper-clad under friction condition; In figure, 1 indicates that friction, 2 indicates without friction.
Fig. 2 is half module and the extrusion stem schematic diagram of the pure titanium ECAP distortion of the present invention mould that adopts, and wherein 2a is the structural representation of half module, and 2b is the structural representation of extrusion stem.
Fig. 3 is pure titanium rod pictorial diagram after four-pass has pushed rear 1,2,4 passage copper-titanium samples and removed copper layer, wherein the I in Fig. 3 a is after 1 passage extruding, not yet to remove copper-titanium sample of outside copper layer, II is after 2 passage extruding, not yet to remove copper-titanium sample of outside copper layer, and III is after 4 passage extruding, not yet to remove copper-titanium sample of outside copper layer.In figure, 3b, 3c and 3d are respectively the pictorial diagram of removing inner pure titanium rod after outside copper layer after 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 passages have been pushed 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 quasistatic of Ultra-fine Grained Compressive Mechanical Properties after the pure titanium of original coarse-grain and the extruding of 1,2,4 passages; In figure: 1. the pure titanium quasistatic of original coarse-grain compressive stress strain curve; 2. the quasistatic compression true stress and strain curve of the pure titanium of Ultra-fine Grained after the 1st passage extruding; 3. the quasistatic compression true stress and strain curve of the pure titanium of Ultra-fine Grained after the 2nd passage extruding; 4. the quasistatic compression true stress and strain curve of the pure titanium of Ultra-fine Grained after the 4th passage extruding;
Fig. 7 is the pure titanium dynamic compression of Ultra-fine Grained mechanics performance after the pure titanium of original coarse-grain and the extruding of 1,2,4 passages, in figure: 5. original thick pure titanium dynamic compressing stress-strain curve; 6. the dynamic compression true stress and strain curve of the pure titanium of Ultra-fine Grained after the 1st passage extruding; 7. the dynamic compression true stress and strain curve of the pure titanium of Ultra-fine Grained after the 2nd passage extruding; 8. the dynamic compression true stress and strain curve of the pure titanium of Ultra-fine Grained after 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, during Equal-channel Angular Pressing is prepared the pure titanium of Ultra-fine Grained, is that employing is at room temperature successfully to prepare the method for the pure titanium of Ultra-fine Grained based on during Equal-channel Angular Pressing technology.The described full name based on during Equal-channel Angular Pressing technology is Equal Channel Angular Pressing, is called for short ECAP, can at room temperature successfully prepare the pure titanium of Ultra-fine Grained.
Provide the complete step of concrete implementation and operation below, can at room temperature 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 Fig. 2 a and 2b.Before extruding, smear uniformly one deck compounded lubricant in channel interior, and extrusion stem is put into channel interior, extrusion stem can play the effect of location like this, and while preventing from installing, two portions half module misplaces; Then with bolt, the set of half mould sets of two portions symmetry is fitted together, forms complete mould, passage interior angle is that 120 °, bullnose are 20 °.The best Bc route of thinning effect for extrusion path line selection, i.e. put access road into after extruded sample being rotated clockwise to 90 ° after every time extruding completes again; The speed that moves down of adjusting universal testing machine crossbeam, makes extrusion stem move down with 0.5～1.5mm/s speed along passage.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:
It is the right cylinder that 60mm, diameter are 5mm that industrial pure titanium TA2 hot rolled plate is cut into length, 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, being processed with vertically diameter is the tapered blind hole that 5mm, the degree of depth are 60mm.This tapered blind hole is coaxial with described copper rod.In this example, the angle of taper of processing is 90 °.
Described titanium rod is packed in copper rod, be assembled into one and become copper-clad and wrapping up in copper-titanium sample of titanium rod, sample is placed in to the inherent 300 DEG C of insulation 2h of process furnace and carries out anneal.Obtain copper-titanium sample.This example is total to 10 of processing sample by above-mentioned steps, and reader can determine sample processing quantity as required.
Step 2, extrusion mould assembling:
85% graphite+15% molybdenumdisulphide the compounded lubricant that evenly smearing thickness is 0.1mm in die channel is to lubricate this die channel, and the ratio of described compounded lubricant is mass percent.Two set of half mould sets are assembled into one with bolt and are 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 is prepared the pure titanium of Ultra-fine Grained by 4 passage extruding, and increases the once anneal to copper-titanium sample between 4 passages.Specifically,
The pure titanium of Ultra-fine Grained is prepared in the first passage extruding: the compounded lubricant that is 0.1mm at the even smearing thickness of copper-titanium specimen surface obtaining, copper-titanium sample is put into die channel, copper-titanium sample is pressed into channel bottom with extrusion stem, 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.Adjust trier crossbeam lowering speed, with the speed of 0.5mm/s, copper-titanium sample is pushed.After described copper-titanium sample is completely by the bent angle in mould, complete the extruding of the first passage.Copper-titanium the sample completing after a time extruding still rests in exit passageway, when putting into when second copper-titanium sample pushes, first sample is ejected, and completes the extruding preparation process for the first time of this copper-titanium sample.
The pure titanium of Ultra-fine Grained is prepared in the second passage extruding: will again put into die channel through copper-titanium sample of extruding for the first time, and the preparation process that repeats to push for the first time, complete the extruding preparation process for the second time to this copper-titanium sample.
Anneal: after having pushed for the second time, this copper titanium sample is placed in process furnace, the copper titanium sample of preparing through twice extruding is carried out to anneal, to remove the unrelieved stress producing due to large plastometric set, ensure that plastix strain larger in follow-up extrusion process can not cause the cracked of sample.Anneal temperature is 200 DEG C, and soaking time is 1h.After insulation finishes, air cooling is to room temperature.
Because too much annealing can reduce the efficiency of grain refining, and the unannealed preparation that is difficult to ensure complete grained material, therefore the present embodiment carries out anneal in the process that is chosen in multi-pass extruding and prepares the pure titanium of Ultra-fine Grained.
The pure titanium of Ultra-fine Grained is prepared in all the other each passages extruding: constantly repeat the process of pushing for the first time, complete the extruding preparation process of setting, until obtain the pure titanium sample of Ultra-fine Grained.
Step 4, surface treatment: method or chemical process by mechanical workout are removed the copper layer of 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 obtaining.
The microtexture of the pure titanium of Ultra-fine Grained obtaining 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.Utilize digital Vickers hardness tester, universal testing machine and Hopkinson bar to carry out Mechanics Performance Testing, after result demonstration thinning processing, the mechanical property of material is greatly improved, and hardness is brought 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 compressive load rises to 813MPa by 475MPa; Under Dynamic Loading, its 10% strain place stress of fluidity rises to 1215MPa by 652MPa, has promoted respectively 71% and 86%.
Embodiment 2
The selected mould of the present embodiment is that passage angle is 120 °, bullnose is the mould of the two-half die composition of 20 °, the best Bc route of thinning effect for extrusion path line selection, i.e. put access road into after extruded sample being rotated clockwise to 90 ° after every time extruding completes 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:
It is the right cylinder that 70mm, diameter are 8mm that industrial pure titanium TA2 hot rolled plate is cut into length, 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, being processed with vertically diameter is the tapered blind hole that 8mm, the degree of depth are 70mm.This tapered blind hole is coaxial with described copper rod.In this example, the angle of taper of processing is 120 °.
The effect that peripheral copper layer of the present invention plays is to reduce extruded sample with the friction between squeezing passage, effectively reduces squeeze, thereby improves the property prepared in the pure titanium room temperature of Ultra-fine Grained situation.The change of outside copper layer thickness will have influence on the accumulation of inner pure titanium rod viscous deformation, and the attenuation of outside copper layer makes inner pure titanium rod in the time that every time pushes, obtain larger distortion, thereby grain refining effect is more obvious, and mechanical property has larger improvement.Meanwhile, the outside copper layer thickness of attenuate can obtain the pure titanium of Ultra-fine Grained of more volume.
In addition, in this example, change tapered blind hole interior tapered angle in copper rod, according to the analysis of ABAQUS finite element analogy result, extruded sample in the process of extruding different angle of taper by the change that causes inner pure titanium rod front end with contact condition inside outside tapered blind hole, excessive cone angle easily produces separating of pure titanium rod front end and copper rod tapered blind hole front end after repeatedly pushing, and pure titanium rod is easily chipping after repeatedly pushing.
Described titanium rod is packed in copper rod, be assembled into one and become copper-clad and wrapping up in copper-titanium sample of titanium rod, sample is placed in to the inherent 300 DEG C of insulation 2h of process furnace and carries out anneal.Obtain copper-titanium sample.This example is total to 10 of processing sample by above-mentioned steps, and reader can determine sample processing quantity as required.
Step 2, extrusion mould assembling:
85% graphite+15% molybdenumdisulphide the compounded lubricant that evenly smearing thickness is 0.1mm in die channel is to lubricate this die channel, and the ratio of described compounded lubricant is mass percent.Two set of half mould sets are assembled into one with bolt and are 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 is prepared the pure titanium of Ultra-fine Grained by 4 passage extruding, and increases the once anneal to copper-titanium sample between 4 passages.Specifically,
The pure titanium of Ultra-fine Grained is prepared in the first passage extruding: the compounded lubricant that is 0.1mm at the even smearing thickness of copper-titanium specimen surface obtaining, copper-titanium sample is put into die channel, copper-titanium sample is pressed into channel bottom with extrusion stem, 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.The speed that moves down of adjusting universal testing machine crossbeam, makes extrusion stem move down copper-titanium sample is pushed with 0.5～1.5mm/s speed along passage.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, complete the extruding of the first passage.Copper-titanium the sample completing after a time extruding still rests in exit passageway, when putting into when second copper-titanium sample pushes, first sample is ejected, and completes the extruding preparation process for the first time of this copper-titanium sample.
The pure titanium of Ultra-fine Grained is prepared in the second passage extruding: will again put into die channel through copper-titanium sample of extruding for the first time, and the preparation process that repeats to push for the first time, complete the extruding preparation process for the second time to this copper-titanium sample.
Anneal: after having pushed for the second time, this copper titanium sample is placed in process furnace, the copper titanium sample of preparing through twice extruding is carried out to anneal, to remove the unrelieved stress producing due to large plastometric set, ensure that plastix strain larger in follow-up extrusion process can not cause the cracked of sample.Anneal temperature is 200 DEG C, and soaking time is 1h.After insulation finishes, air cooling is to room temperature.
Because too much annealing can reduce the efficiency of grain refining, and the unannealed preparation that is difficult to ensure complete grained material, therefore the present embodiment carries out anneal in the process that is chosen in multi-pass extruding and prepares the pure titanium of Ultra-fine Grained.
The pure titanium of Ultra-fine Grained is prepared in all the other each passages extruding: constantly repeat the process of pushing for the first time, complete the extruding preparation process of setting, until obtain the pure titanium sample of Ultra-fine Grained.
Step 4, surface treatment: method or chemical process by mechanical workout are removed the copper layer of 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 obtaining.
Embodiment 3
The selected mould of the present embodiment is that passage angle is 90 °, and bullnose is the mould of the two-half die composition of 30 °.Die channel angle and bullnose are the important parameters that affects every time extruding of extruded sample and complete after strain amount size, reduce passage angle and can effectively increase every time extruded sample amount of plastic deformation, increase bullnose and can make sample easier pass through bent angle.The best Bc route of thinning effect for extrusion path line selection, i.e. put access road into after extruded sample being rotated clockwise to 90 ° after every time extruding completes 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:
It is the right cylinder that 70mm, diameter are 8mm that industrial pure titanium TA2 hot rolled plate is cut into length, 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, being processed with vertically diameter is the tapered blind hole that 8mm, the degree of depth are 70mm.This tapered blind hole is coaxial with described copper rod.In this example, the angle of taper of processing is 90 °.
Described titanium rod is packed in copper rod, be assembled into one and become copper-clad and wrapping up in copper-titanium sample of titanium rod, sample is placed in to the inherent 300 DEG C of insulation 2h of process furnace and carries out anneal.Obtain copper-titanium sample.This example is total to 10 of processing sample by above-mentioned steps, and reader can determine sample processing quantity as required.
Step 2, extrusion mould assembling:
85% graphite+15% molybdenumdisulphide the compounded lubricant that evenly smearing thickness is 0.1mm in die channel is to lubricate this die channel, and the ratio of described compounded lubricant is mass percent.Two set of half mould sets are assembled into one with bolt and are 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 is prepared the pure titanium of Ultra-fine Grained by 4 passage extruding, and increases the once anneal to copper-titanium sample between 4 passages.Specifically:
The pure titanium of Ultra-fine Grained is prepared in the first passage extruding: the compounded lubricant that is 0.1mm at the even smearing thickness of copper-titanium specimen surface obtaining, copper-titanium sample is put into die channel, copper-titanium sample is pressed into channel bottom with extrusion stem, 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.Adjust trier crossbeam lowering speed, with the speed of 1.5mm/s, copper-titanium sample is pushed.After described copper-titanium sample is completely by the bent angle in mould, complete the extruding of the first passage.Copper-titanium the sample completing after a time extruding still rests in exit passageway, when putting into when second copper-titanium sample pushes, first sample is ejected, and completes the extruding preparation process for the first time of this copper-titanium sample.
The pure titanium of Ultra-fine Grained is prepared in the second passage extruding: will again put into die channel through copper-titanium sample of extruding for the first time, and the preparation process that repeats to push for the first time, complete the extruding preparation process for the second time to this copper-titanium sample.
Anneal: after having pushed for the second time, this copper titanium sample is placed in process furnace, the copper titanium sample of preparing through twice extruding is carried out to anneal, to remove the unrelieved stress producing due to large plastometric set, ensure that plastix strain larger in follow-up extrusion process can not cause the cracked of sample.Anneal temperature is 200 DEG C, and soaking time is 1h.After insulation finishes, air cooling is to room temperature.
Because too much annealing can reduce the efficiency of grain refining, and the unannealed preparation that is difficult to ensure complete grained material, therefore the present embodiment carries out anneal in the process that is chosen in multi-pass extruding and prepares the pure titanium of Ultra-fine Grained.
The pure titanium of Ultra-fine Grained is prepared in all the other each passages extruding: constantly repeat the process of pushing for the first time, complete the extruding preparation process of setting, until obtain the pure titanium sample of Ultra-fine Grained.
Step 4, surface treatment: method or chemical process by mechanical workout are removed the copper layer of 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 obtaining.
Claims (2)
1. during Equal-channel Angular Pressing is prepared 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 to multiple titanium rods; One end of this titanium rod is cone-shaped body; Fine copper is made to multiple copper rods; In this copper rod, there is vertically tapered blind hole; Described titanium rod is packed in copper rod, be assembled into one and become copper-clad and wrapping up in copper-titanium sample of titanium rod, heat and be incubated by process furnace and carry out anneal, to remove unrelieved stress; Obtain multiple copper-titanium samples;
Step 2, the installation of extrusion mould:
In die channel, evenly apply compounded lubricant; Two set of half mould sets are dressed up to one and be placed on 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 four-pass extruding:
Push and prepare the pure titanium of Ultra-fine Grained by four-pass, and increase the once anneal to copper-titanium sample between four-pass; Specifically,
The pure titanium of Ultra-fine Grained is prepared in the first passage extruding: the compounded lubricant that is 0.1mm at the even smearing thickness of copper-titanium specimen surface obtaining, copper-titanium sample is put into die channel, and by extrusion stem, copper-titanium sample is pressed into 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 pushed, extrusion speed is 0.1～1.5mm; After described copper-titanium sample is completely by the bent angle in mould, complete the extruding of the first passage; Copper-titanium the sample completing after a time extruding still rests in exit passageway, when putting into when second copper-titanium sample pushes, first sample is ejected, and completes the extruding preparation process for the first time of this copper-titanium sample; The pure titanium of Ultra-fine Grained is prepared in the second passage extruding: will again put into die channel through copper-titanium sample of extruding for the first time, and the preparation process that repeats to push for the first time, complete the extruding preparation process for the second time to this copper-titanium sample; Anneal: after having pushed for the second time, this copper titanium sample is placed in process furnace, the copper titanium sample of preparing through twice extruding is carried out to anneal, to remove the unrelieved stress producing due to large plastometric set, ensure that plastix strain larger in follow-up extrusion process can not cause the cracked of sample; Anneal temperature is 200 DEG C, and soaking time is 1h; After insulation finishes, air cooling is to room temperature;
The pure titanium of Ultra-fine Grained is prepared in all the other each passages extruding: constantly repeat the process of pushing for the first time, complete the extruding preparation process of setting, until obtain the pure titanium sample of Ultra-fine Grained;
Step 4, surface treatment: method or chemical process by mechanical workout are removed the copper layer of copper-titanium sample outside, obtain Ultra-fine Grained pure titanium rod material.
2. during Equal-channel Angular Pressing is prepared the method for the pure titanium of Ultra-fine Grained as claimed in claim 1, it is characterized in that, described compounded lubricant is formulated by 85% graphite and 15% molybdenumdisulphide, and described per-cent is mass percent.
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