CN103409663B - Method for preparing two-way memory nickel-titanium alloy for artificial sphincters through rapid solidification - Google Patents
Method for preparing two-way memory nickel-titanium alloy for artificial sphincters through rapid solidification Download PDFInfo
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- CN103409663B CN103409663B CN201310290159.7A CN201310290159A CN103409663B CN 103409663 B CN103409663 B CN 103409663B CN 201310290159 A CN201310290159 A CN 201310290159A CN 103409663 B CN103409663 B CN 103409663B
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Abstract
The invention discloses a method for preparing a two-way memory nickel-titanium alloy for artificial sphincters through rapid solidification. The method comprises the following steps of: weighing high-purity nickel and high-purity titanium which are used as raw materials according to the condition that the atomic ratio of nickel atoms to titanium atoms is 51:49; putting and smelting the raw materials a nonconsumable vacuum arc smelting furnace, absorbing molten metal into a copper die cavity by virtue of a negative-pressure suction casting method carried out by a water-cooled copper die, and carrying out rapid solidification, thereby obtaining a material in the required shape; homogenizing the material; fixing the treated material in a semicircular die with curvature radius, deforming the material under constraint of the die to correspond to the curvature of the die, putting the material together with the die into a resistance furnace to undergo constraint aging at 350-500 DEG C which is maintained for 10-100 hours and quenching the material and the die in water, thus preparing the two-way memory nickel-titanium alloy material for the artificial sphincters. The two-way memory nickel-titanium alloy material has narrow temperature zone response, has a straight shape at normal temperatures of human bodies and has bigger deformation curvature after temperature raising, thus being suitable for serving as the function material of the artificial sphincters.
Description
Technical field
The present invention relates to a kind of bidirectional memory nickel-titanium alloy material, particularly relate to a kind of method that rapid solidification prepares narrow warm area response artificial sphincter bidirectional memory Ni-Ti alloy, belong to biomedical applications field shape-memory material.
Background technology
Shape memory alloy is from being found existing half a century; Up to now, the alloy with shape memory effect reaches 50 kinds more than, but really have use value and obtain practical engineering application mainly contain NiTi base and Cu base, Fe base alloy.NiTi shape memory alloy has excellent shape memory effect and super-elasticity behavior, and good mechanical property, erosion resistance and biocompatibility, and thus it is most widely used a kind of memory metal in all shape memory alloys.Cu base marmem is cheaper relative to NiTi base alloy price, and its conduction, heat conductivility is also better than NiTi base alloy, and wherein Cu-Zn-Al, Cu-Al-Ni alloy has shown good application prospect.Fe-Mn-Si alloy is cheap, because shape memory effect is little, is applicable to make tube stub.In some application, Cu base, Fe base alloy can substitute NiTi alloy, but in human body application aspect, but do not have which class shape memory alloy to substitute NiTi alloy.This is mainly not available for other shape memory alloy due to the biocompatibility of NiTi alloy, and it can implant into body safely.
NiTi alloy has considerable example in the application of biomedical sector, and according to existing, its application comprises NiTi alloy inner support, minimally invasive medical apparatus, orthopedics and brain surgery and stomatology field etc.The medical use of NiTi alloy has formed a collection of high-tech industry having considerable scale in the U.S., Japan and Europe, and the annual output value reaches 4,000,000,000 dollars.NiTi alloy is used as artificial organs core material by the scholar also had, and namely the present invention relates to an application example---the artificial anal sphincter that NiTi substitutes human organ, to treatment patient anal function incontinence problems.
Fecal incontinence is the congenital functional defect of anal sphincter or downright bad and restraining defecation defective disease that is that cause, although it can not direct life-threatening, brings inconvenience and puzzlement, cause dual misery to body & mind to patient.For treatment fecal incontinence, the method generally used is sphincteroplasty and colonic diversion, but there will be " leakage excrement " phenomenon and graft muscle fatigue.Therefore, implement operating method and can not play good result for the treatment of, people just expect in the sphincteral method of human body implantable artificial.Christiansen J etc. has invented a kind of artificial sphincter (AMS800) makes many patients benefit, but its complex structure and work-ing life shorter.Amae S etc. once proposed the bidirectional shape memory effect design artificial sphincter utilizing shape memory alloy; Its principle is had by two panels that the alloy slice two ends of two-way memory effect are hinged forms functional framework, clamped by rectum, form similar " sandwich " structure.The two-way memory effect of Ni-Ti alloy refers to shape when Ni-Ti alloy can distinguish " remembeing " high temperature and low temperature, can occur reversible change in intensification and temperature-fall period between two shapes.According to the characteristic of shape memory alloy, when patient realizes without defecation, two alloy slices are in intimate straightened condition, thus play the effect of closing rectum; When patient starts defecation, two alloy slices are bent to form rapidly arc-shaped due to the heat effect of indirect heating element, formed and have the inner chamber of one fixed width, carry out defecation for intestine activities; When defecation terminates, treat that two alloy slices are down to body temperature naturally, alloy slice also returns to original straightened condition, and rectum is closed.
The existing techniqueflow preparing two-way shape memory Ni-Ti alloy is generally: raw material → molten alloy ingot → casting → forging → cold rolling/hot rolling → annealing → shape memory process repeatedly.These methods often need carry out the viscous deformation of large sstrain amount to material and introduce highdensity dislocation, and the size of crystal grain, shape and distribution etc. are in obvious directivity (such as crystal grain is elongated along rolling direction and is crushed along rolling normal direction) thus cause the anisotropy in performance; Especially by dislocation mechanism predominant methods train acquisition double process shape-memory effect mainly to be produced by martensitic transformation and reverse transformation thereof, there is the temperature lower (usually in sub-zero zero) of positive reverse martensitic transformation, and the hysteresis of phase transformation interval of its adjoint two-way shape memory behavior comparatively large (50 ~ 60 DEG C), double process shape-memory effect also easily fails.The present invention adopts flash set technology first in NiTi mother metal, to obtain tiny and equally distributed crystal grain, and the crystal grain with this feature is conducive to Ni in constraint aging process
4ti
3a large amount of precipitations of precipitated phase, and the R phase transformation of induced phase transition temperature hysteresis interval less (5 ~ 10 DEG C) and reverse transformation thereof produce; Under suitable Time restrains art breading, the transformation temperature of R phase transformation can be conditioned and by stability contorting near body temperature with human body institute tolerant temperature range in, be suitable as very much the biomedical SMART METALS material of implant into body, be especially suitable for preparing narrow warm area response artificial sphincter core material proposed by the invention.
Summary of the invention
A kind of rapid solidification is the object of the present invention is to provide to prepare the method for narrow warm area response artificial sphincter Ni-Ti alloy, for manually the sphincteral material that should be used as prepares.
Artificial sphincter bidirectional memory NiTi alloy should meet following requirement:
(1) NiTi alloy transformation temperature is delayed little, has sufficiently high stability and lasting reliability.
(2) phase transition temperature interval is little as far as possible, and change in shape is fast.Phase transition temperature interval is little can shortening heat cumulative process, reduces heat-up time, and can play quick " on-off " function.
(3) NiTi alloy shape change (phase transformation) temperature should can bear temperature with human body and is suitable for mutually, then near body temperature, (as 36 DEG C) change in shape can not be there is time too much lower than body temperature, time too high, then burning sensation can be brought even to cause damaging (general requirement is not higher than 60 DEG C) to tissue.Therefore, require that NiTi alloy has bidirectional memory function fast within the scope of the comparatively narrow temperature of setting.
(4) in order to meet normal folding, require that two panels NiTi alloy shell fragment has compared with macrobending radius of the radian in closed state or is bordering on straight, and have less crooked radian radius when opening to ensure that enough major lumen are movable for intestinal tube.
Bidirectional shape memory effect is not the build-in attribute of material, and could must be obtained by certain Re-Li process, the repetition Re-Li of this experience phase transition temperature interval circulation is referred to as " training " by the present invention.Common bidirectional memory training method comprises following several: the distortion that (1) is once excessive; (2) constant stress thermal cycling; (3) super-elasticity training; (4) shape memory training; (5) constraint aging.But above-mentioned " training " process can make NiTi alloy inside produce the distribution of specific dislocation (1 ~ 4) or precipitated phase (5), in the process of heating, twin crystal martensite variant disappears and changes to austenitic state, but dislocation and precipitated phase are still present in parent phase.When cooled, dislocation and the specific stress riser of precipitated phase, by forming the martensite variants of effective internal stress field initiation specific orientation, make NiTi alloy produce spontaneous change in shape, bring out bidirectional shape memory effect.
The two-way memory effect that NiTi alloy produces through (1 ~ 4) training method, causes internal stress field by dislocation mechanism, and material will produce true plastic distortion, namely leave residual strain.Originally straight material, can not return to original state completely, namely can not meet when artificial sphincter requirement closes and be bordering on straight condition after training in cold cycling subsequently.And the NiTi alloy of rich Ni causes a kind of special two-way memory effect after timeliness, can there is reverse bending when being down to low temperature in it, thus must occur straight state in temperature-fall period.
NiTi alloy is after the training of (1 ~ 4) method, and the dislocation formed in Thermal Cycling can produce interaction, the internal stress field produced when thus relaxing training with the dislocation produced during training, causes two-way memory effect to be decayed.NiTi alloy there will be R phase transformation through the training of (5) method with temperature decline, and this treatment process makes NiTi alloy inside separate out Ni
4ti
3precipitated phase, brings out R phase and the B19 ' martensite variants of preferred orientation under the stress field effect that they are formed.R phase transformation has the little hysteresis of phase transformation and high stability, and under constant stress after thermal cycling 500,000 times, the stress-strain curve of R phase does not also have significant change.Ni at not higher than 600 DEG C of temperature in circulation time alloy
4ti
3precipitated phase is stable, and effective internal stress field energy that thus it is formed continues the two-way memory effect causing alloy, does not decay; So just can ensure reliability during NiTi memorial alloy continuous firing.
The conventional process preparing memorial alloy is: raw material → alloy pig → forging → cold rolling/hot rolling → annealing → shape memory process.Relatively loaded down with trivial details in production technique, tooling cost is higher, and the shape memory effect obtained is often based on martensitic transformation and reverse transformation thereof, does not possess the feature that HYSTERESIS OF PHASE TRANSFORMATION TEMPERATURE is little and phase transition temperature interval is little; Even if adopt repetitious constraint aging process to bring out part R phase transformation, but due to the reason such as anisotropy of coarse grains and crystal grain distribution, be also difficult to obtain large deformation quantity and stable deformation effect.The present invention utilizes flash set technology to combine with constraint aging process, in alloy mother metal, first obtain the tiny and two columanar structures that are that formed along both sides, thickness of sample direction crystal grain to interstitial growth of crystal grain; The alloy material with this tissue characteristic, in round trip memory process, only needs can obtain and meet by carrying out disposable constraint aging process the nickel-titanium alloy material that artificial sphincter requirement has narrow warm area response bidirectional memory characteristic under specific processing parameter.Namely flash set technology is that (rate of cooling is greater than 10 at a terrific speed by liquid metal
4~ 10
6k/s) be quickly cooled to room temperature and solidify the technology of setting.It is applicable to produce the small dimension product such as strip, filament, pole, and can once shaped, and technique is simple, has higher yield rate.Flash set technology can improve microstructure, crystal grain thinning, reduces segregation.The sample prepared of flash set technology through raw material → melting → rapid solidification shaping → operational path of shape memory process obtains memorial alloy, shortens usual processing route, reduce production cost.
Therefore, the present invention adopts rapid solidification to prepare the method for artificial sphincter bidirectional memory Ni-Ti alloy, strains at initial bending
under carry out constraint aging " training ",
value need ensure that Ni-Ti alloy sheet specimens is at room temperature in straightened condition; Cause the two-way memory effect of Ni-Ti alloy, work out complete bidirectional memory Ni-Ti alloy preparation technology and technology, be the manually sphincteral preparation that should be used as on material, and to the preparation of shape memory alloy, also there is important reference value.
For realizing the object of the invention, undertaken by following technical scheme:
Rapid solidification prepares the method for artificial sphincter bidirectional memory Ni-Ti alloy, comprises the steps:
(1) compare for 51:49 according to nickel, titanium atom, take high purity nickel and high purity titanium raw material;
(2) step (1) raw material is put into the melting of non-consumable vacuum arc melting furnace, and with water cooled copper mould negative pressure suction casting method, molten metal is sucked in copper die cavity, after rapid solidification, obtain the material of desired shape;
(3) step (2) material is put into vitreosil pipe and passed into high-purity argon gas protection, at 800 ~ 950 DEG C of temperature, insulation carries out Homogenization Treatments in 1 ~ 10 hour, then quenches in water;
(4) will be fixed in the circular dies with crooked radian radius by material after step (3) process, the distortion that material is subject to the constraint generation of mould corresponding with mold bending radian, material is put into together with mould the constraint aging process that resistance furnace carries out being incubated at 350 ~ 500 DEG C 10 ~ 100h, then quench in water, obtained have narrow warm area response artificial sphincter bidirectional memory nickel-titanium alloy material; The crooked radian radius of described circular dies is according to formula
determine, wherein t is material thickness, unit mm; Crooked radian radius when ρ is constraint, unit mm; ε
tfor flexural strain, be 0.80% ~ 1.50%.
For realizing the object of the invention further, the purity of selected high purity nickel is higher than 99.96%, and high purity titanium purity is higher than 99.76%.
The preferred purity of high-purity argon gas is higher than 99.999%.
A typical sizes of Ni-Ti alloy sheet is that 50 ~ 100mm(is long) × 8 ~ 10mm(is wide) × 0.5 ~ 1.5mm(is high), also by the different copper mold of processing, other size can be obtained, also can with Linear cut or other method be thinning or change alloy slice size.
The present invention is relative to the advantage of prior art:
1, preparation technology is simple.The present invention's flash set technology prepares Ni-Ti alloy, without the need to through complicated mechanical processing process after shaping, has significant advantage for for the preparation of the small dimension product in biomedicine.
2, shape memory effect process adopts " training " method of a constraint aging, circulates " training " without Re-Li, and one treatedly can obtain stable performance and meet the material of artificial sphincter service requirements.
3, the Ni-Ti alloy hysteresis of phase transformation (A
f-R
sor A
s-R
f) little, be about 5 ~ 10 DEG C.The hysteresis of phase transformation is little, then the temperature range lower the temperature, heated up is also little, is applicable to have the action element that " on-off " acts on.
4, the temperature range (R of Ni-Ti alloy distortion
s-R
fand A
f-A
s) little, be about 8 ~ 15 DEG C.In narrow temperature range internal strain, can accelerate the process of heat accumulation, Ni-Ti alloy can quick motion at short notice, is specially adapted to medical use.
5, flexural strain ε is determined
tspan, the Ni-Ti alloy of different size/thickness can be prepared, there is very large selectivity and handiness.As long as constraint aging within the scope of this, straight under all can obtaining room temperature, bend to the Ni-Ti alloy of circular arc after intensification, there is important directive significance.
6, be incubated the constraint aging processing condition of 10 ~ 100h at 350 ~ 500 DEG C under, different flexural strain ε is adopted
tall can obtain identical from high temperature to room temperature between bidirectional reversible dependent variable, its value is about 0.4 ~ 0.6%.Therefore can select the size/thickness of Ni-Ti alloy flexibly, obtain different maximum flexibility radians.
Accompanying drawing explanation
Fig. 1-1 is constraint aging training schematic diagram: (a) is restrained condition; B () is restraint release state.
Fig. 1-2 is Ni-Ti alloy sample optical microstructure photo prepared by rapid solidification method: (a) is sample surfaces microstructure; B () is example cross section microstructure.
Fig. 1-3 is the DSC curve of (nonageing process) NiTi sample after Homogenization Treatments.
Fig. 1-4 is that Ni-Ti alloy is in differently curved strain stress
tunder carry out the DSC curve after being incubated 50h timeliness at 450 DEG C.
Fig. 1-5 is the X ray diffracting spectrum after embodiment 1 Homogenization Treatments.
Fig. 1-6 is the X ray diffracting spectrum of embodiment 1 after being incubated 50h timeliness at 450 DEG C.
Fig. 1-7 occurs bending and deformation after embodiment 1 constraint aging and recovers flat situation between boiled water temperature (a, about 100 DEG C) Yu room temperature (b, about 30 DEG C).
Fig. 1-8 strains variation with temperature graphic representation in slow lifting/lowering temperature process for after embodiment 1 constraint aging in thermostat water bath.
Fig. 2-1 occurs bending and deformation and the situation recovering flat after embodiment 2 constraint aging between boiling water (a, about 100 DEG C) temperature and room temperature (b, about 30 DEG C).
Fig. 3-1 occurs bending and deformation and the situation recovering flat after embodiment 3 constraint aging between boiling water (a, about 100 DEG C) temperature and room temperature (b, about 30 DEG C).
Embodiment
For better understanding the present invention, below in conjunction with embodiment and accompanying drawing, the present invention will be further described, but the scope of protection of present invention is not limited to the scope that embodiment represents.
Embodiment 1
Be 51:49(mass ratio by high purity nickel (quality purity 99.96%) and high purity titanium (quality purity 99.7%) in Ni, Ti atomic ratio be 56.05:43.95) ratio take, its total mass is 6.5g.After high purity nickel and high purity titanium mixing, put in the water jacketed copper crucible of non-consumable vacuum arc melting furnace (WK-1 type, Beijing Wu Ke Electro-optical Technology, INC. (US) 62 Martin Road, Concord, Massachusetts 017).Non-consumable vacuum arc melting furnace is through taking out rough vacuum (5Pa) and high vacuum (5 × 10
-3pa) after, pour an atmospheric high-purity argon gas (purity is 99.999%) and carry out gas washing, then repeat once to take out rough vacuum (5Pa) and high vacuum (5 × 10
-3then pour an atmospheric high-purity argon gas as protection gas and striking gas Pa).
The electrode made by tungsten bar and crucible bottom electrode moment short circuit are also removed rapidly, to draw electric arc, the purification of placing in addition in first smelting pot with pure titanium block to remove foreign gas in non-consumable vacuum arc melting furnace chamber further, then electric arc is aimed at the nickel on crucible, titanium biased sample makes it melt and alloying, melting electric current 100A also keeps 1 minute, then turn-off current.Again use the electric current melting Ni-Ti alloy 60 seconds of 160A after striking, Ni-Ti alloy becomes split pole uneven after above-mentioned melting, after its cooling, utilize non-consumable vacuum arc melting furnace supporting machinery hand to be overturn by alloy pig, by aforementioned identical melting condition (160A, 60 seconds) remelting, repeats this process and makes alloying constituent homogenizing 5 ~ 6 times.Vacuum arc melting furnace is furnished with copper mold crystallizer, logical recirculated cooling water around copper mold crystallizer.Copper mold lower end is connected with the forepump of non-consumable vacuum arc melting furnace, and alloy pig again melts and increases melting electric current to 180A to improve its mobility.When inhaling casting, provide an instantaneous negative pressure to be sucked rapidly in copper mold by molten metal bath by vacuum pump, under the heat transfer process of copper mold and outside recirculated cooling water thereof, speed of cooling can reach 1.0 × 10
4k/S, thus has very large condensate depression; With the melt generation Fast Inhomogeneous forming core of copper mold inwall contacts side surfaces, simultaneously due to the radiating mode of melt composition (along thickness of sample direction from heart portion to sample surfaces) from inside to outside, i.e. positive thermograde, the crystal grain of forming core under this thermograde particular crystal orientation along heat dissipation direction preferential growth, namely along the crystal grain of both sides, thickness of sample direction to interstitial growth, two columanar structure is finally formed.Nickel-titanium metal liquid is by inhaling after casting process realizes rapid solidification in copper mold, and the fine and close Ni-Ti alloy of obtained sheet, its typical sizes is that 60mm(is long) × 8mm(is wide) × 1mm(is high).
Ni-Ti alloy is enclosed in vitreosil pipe, and at 850 DEG C, insulation carries out Homogenization Treatments in 10 hours, after quench in water.After Homogenization Treatments, micro-area composition can be obtained and organize uniformly.
Shape memory effect process is carried out in the following manner: be 66mm(flexural strain ε by being incubated at 850 DEG C after 10 hours Homogenization Treatments that gained 0.7mm slab-like sample is tied to diameter
t=1.05%) in circular dies, the distortion that material is subject to the constraint generation of mould corresponding with mold bending radian, material puts into chamber type electric resistance furnace with mould, at 450 DEG C, be incubated 50h; After shrend, shed mould, clean sample, obtained artificial sphincter is suitable for bidirectional memory nickel-titanium alloy material.As Figure 1-1, material is by restrained distortion and be close to bed die outer wall for semicircle constraint aging mould diagrammatic cross-section, is determined by the thickness of material and the radius of mould the restraint strain that material produces.The circular dies with crooked radian radius ρ strains according to formula the forced synchroniztion that sample produces
determine, experimental data shows, for ensureing that Ni-Ti alloy sheet specimens is at room temperature in straightened condition, ε
tshould be 0.80% ~ 1.50%; Wherein t is material thickness (the present embodiment is 0.7mm); ε
tfor flexural strain, the present embodiment ε
t=1.05%.Determine that crooked radian radius ρ when retraining is 33mm by this formula.Fig. 1-2 is Ni-Ti alloy sample light micrograph prepared by rapid solidification method: Fig. 1-2 (a) is sample surfaces light micrograph; Can find out that Ni-Ti alloy sample surfaces prepared by rapid solidification method is equally distributed equi-axed crystal from Fig. 1-2 (a), grain size size is at about 10 ~ 20 μm, and Ni-Ti alloy prepared by this explanation rapid solidification method can obtain the crystal grain of fine size.Fig. 1-2 (b) is the light micrograph at rapid solidification example cross section place, and as can be seen from the figure on the cross section of NiTi sheet sample, crystal grain is column crystal.
Fig. 1-3 is the DSC curve of (nonageing process) NiTi sample after Homogenization Treatments.As can be seen from the figure, Ni-Ti alloy is there are no any phase transformation peak in probe temperature interval, and this is that Ni-Ti alloy B19 ' martensitic transformation temperature when lowering the temperature of rich nickel causes lower than-100 DEG C.
Fig. 1-4 is that Ni-Ti alloy is at flexural strain ε
tbe carry out the DSC curve after being incubated 50h timeliness at 450 DEG C for 0.97% ~ 2.44% time.Wherein R
s, R
fand M
s, M
fr phase transformation and B19 ' martensitic transformation starting and ending temperature during expression cooling respectively; A
s, A
frepresent the starting and ending temperature of austenite phase transformation (martensite reverse transformation) respectively.As can be seen from Fig. 1-7, R
s, M
sthe impact that point strains size is by bending little, and this illustrates R phase transformation and B19 ' martensitic transformation temperature mainly by aging temp and the impact of time.Be incubated the aging condition of 50h at 450 DEG C under, Ni
4ti
3phase and B2 parent phase reach equilibrium state, and the quantity separating out precipitated phase from matrix is certain, and the difference of flexural strain only can affect the orientation of precipitated phase.After measured, 50h constraint aging process flexural strain ε is incubated at 450 DEG C
tbe 0.97% ~ 2.44% its R phase transformation of aging samples and Reverse Martensitic Transformation Temperatures interval be respectively 7 ~ 10 DEG C and 8 ~ 11 DEG C, HYSTERESIS OF PHASE TRANSFORMATION TEMPERATURE is 5 ~ 10 DEG C.Differential scanning calorimetric analysis/DSC is a kind of effective ways of research alloy phase change process, it, by the thermal change of detection of dynamic alloy system in program-controlled heating process, directly or indirectly measures the thermodynamics and kinetics information such as the transformation temperature of alloy, phase transformation heat content.
Fig. 1-5 is the X ray diffracting spectrum after embodiment 1 Homogenization Treatments.Diffraction analysis shows, after Homogenization Treatments, alloy obtains the single-phase and a small amount of NiTi of single B2 structure NiTi
2and Ni
3ti phase.Fig. 1-6 is the X-ray diffractogram of embodiment 1 after being incubated 50h timeliness at 450 DEG C, as can be seen from the figure after long-time timeliness, has separated out Ni in matrix
4ti
3precipitated phase, at room temperature (25 DEG C) have B2 and R phase simultaneously.Ni
4ti
3bring out the R phase variant of preferred orientation with the coherence internal stress field of matrix, and then cause the two-way memory effect of Ni-Ti alloy.Relative to the Ni-Ti alloy X ray diffracting spectrum after Homogenization Treatments in Fig. 1-5, after constraint aging, Ni-Ti alloy sample has obvious preferred orientation, and this is the result that matrix and precipitated phase have direction to arrange.
Fig. 1-7 occurs bending and deformation and the recording photograph recovering flat after embodiment 1 constraint aging between boiled water temperature (a, about 100 DEG C) Yu room temperature (b, about 30 DEG C).Boiled water temperature is higher than A
fpoint, Ni-Ti alloy returns to B2 parent phase, has maximum flexibility radian; Room temperature is in R
fwith M
sbetween point, Ni-Ti alloy R phase transformation completes, is in and is bordering on straightened condition.Fig. 1-8 strains variation with temperature graphic representation in slow lifting/lowering temperature process for after embodiment 1 constraint aging in thermostat water bath.At room temperature strain value is very little is about 0.01%, its shape corresponding diagram 1-7(a for sample); When being warming up to A
fit is 0.48% that later sample can reach maximum strain, its shape corresponding diagram 1-7(b), R phase is all converted into B2 parent phase, continues intensification shape and does not also change.Ni-Ti alloy is at phase transition temperature interval (R
s, R
fand A
s, A
f) change in shape speed is fast, also have certain change in shape in non-phase transition temperature interval, but rate of change is little, this is that the adjustment of R phase variant orientation causes.Strain value according to lifting/lowering temperature changes, the initial sum final temperature of R phase transformation and reverse transformation thereof can also be drawn, its R phase transformation and Reverse Martensitic Transformation Temperatures interval are respectively 6 ~ 10 DEG C and 8 ~ 12 DEG C, and the R HYSTERESIS OF PHASE TRANSFORMATION TEMPERATURE that also can calculate embodiment 1 is accordingly very little, only has 4 ~ 8 DEG C.This result is consistent with DSC test result.
As mentioned above, embodiment 1 utilizes flash set technology to combine with constraint aging process, in alloy mother metal, first obtain the tiny and two columanar structures that are that formed along both sides, thickness of sample direction crystal grain to interstitial growth of crystal grain; The alloy material with this tissue characteristic, in round trip memory process, only needs can obtain and meet by carrying out disposable constraint aging process the nickel-titanium alloy material that artificial sphincter requires to have narrow warm area response bidirectional memory characteristic under the processing parameter of the present embodiment.Even and if existing technology adopts repetitious constraint aging process to be also difficult to obtain the two-way shape memory materials that HYSTERESIS OF PHASE TRANSFORMATION TEMPERATURE is interval and phase transition temperature interval is all narrow.
Embodiment 2
Be 51:49(mass ratio by high purity nickel (purity 99.96%) and high purity titanium (purity 99.7%) in Ni, Ti atomic ratio be 56.05:43.95) ratio take, its total mass is 8.2g.After high purity nickel and high purity titanium mixing, put in the water jacketed copper crucible of non-consumable vacuum arc melting furnace (WK-1 type, Beijing Wu Ke Electro-optical Technology, INC. (US) 62 Martin Road, Concord, Massachusetts 017).Smelting furnace is through taking out rough vacuum (5Pa) and high vacuum (5 × 10
-3pa) after, pour an atmospheric high-purity argon gas (purity is 99.999%) and carry out gas washing, then repeat to take out a rough vacuum (5Pa) and high vacuum (5 × 10
-3then pour an atmospheric high-purity argon gas as protection gas and striking gas Pa).
The electrode made by tungsten bar and crucible bottom electrode moment short circuit are also removed rapidly, to draw electric arc, the pure titanium block placed in first smelting pot is to remove foreign gas in chamber further, then electric arc is aimed at the nickel on crucible, titanium biased sample makes it melt and alloying, melting electric current 80A also keeps 90 seconds, then turn-off current.Again use the electric current melting Ni-Ti alloy 90 seconds of 140A after striking, Ni-Ti alloy becomes split pole uneven after above-mentioned melting, after its cooling, utilize non-consumable vacuum arc melting furnace supporting machinery hand to be overturn by alloy pig, by aforementioned identical melting condition (140A, 90 seconds) remelting, repeats this process and makes homogenization of composition 5 ~ 6 times.Vacuum arc melting furnace is furnished with copper mold crystallizer, logical recirculated cooling water around copper mold.Copper mold lower end is connected with the forepump of equipment, and alloy pig again melts and increases melting electric current to 200A to improve its mobility.When inhaling casting, provide an instantaneous negative pressure to be sucked rapidly in copper mold by molten metal bath by vacuum pump, under the heat transfer process of copper mold and outside recirculated cooling water thereof, speed of cooling can reach about 1.2 × 10
4k/S, thus has very large condensate depression.Nickel-titanium metal liquid realizes molten metal rapid solidification in copper mold after rapid solidification by inhaling casting process in copper mold, the fine and close Ni-Ti alloy of obtained sheet, and its typical sizes is that 80mm(is long) × 10mm(is wide) × 1.2mm(is high).Ni-Ti alloy is enclosed in vitreosil pipe, is incubated 10 hours, carries out Homogenization Treatments at 950 DEG C, after quench in water.After Homogenization Treatments, micro-area composition can be obtained and organize uniformly.
Shape memory effect process is carried out in the following manner: 1.2mm slab-like sample Linear cut mode is obtained 0.55mm thick; Sample being tied to diameter is D=48mm(ε
t=1.13%) constraint aging being incubated 100h at 350 DEG C is carried out in circular dies; After shrend, shed mould, clean sample, obtained artificial sphincter bidirectional memory nickel-titanium alloy material.The circular dies with crooked radian radius ρ strains according to formula the forced synchroniztion that sample produces
determine, wherein t is material thickness (the present embodiment is 0.55mm); ε
tfor flexural strain is answered, the present embodiment ε
t=1.13%.Determine that crooked radian radius ρ when retraining is 24mm by this formula.
Fig. 2-1 occurs bending and deformation and the recording photograph recovering flat between boiled water temperature (Fig. 2-1a about 100 DEG C) Yu room temperature (Fig. 2-1b, about 30 DEG C) temperature for embodiment 2.Its maximum bending strain in boiling water is 0.55%, and the flexural strain under room temperature is 0.02%, and the bidirectional reversible dependent variable between thus from high temperature to room temperature is 0.53%.
Embodiment 3
Be 51:49(mass ratio by high purity nickel (purity 99.96%) and high purity titanium (purity 99.7%) in Ni, Ti atomic ratio be 56.05:43.95) ratio take, its total mass is 7.5g.After high purity nickel and high purity titanium mixing, put in the water jacketed copper crucible of non-consumable vacuum arc melting furnace (WK-1 type, Beijing Wu Ke Electro-optical Technology, INC. (US) 62 Martin Road, Concord, Massachusetts 017).Smelting furnace is through taking out rough vacuum (5Pa) and high vacuum (5 × 10
-3pa) after, pour an atmospheric high-purity argon gas (purity is 99.999%) and carry out gas washing, then repeat to take out a rough vacuum (5Pa) and high vacuum (5 × 10
-3then pour an atmospheric high-purity argon gas as protection gas and striking gas Pa).
The electrode made by tungsten bar and crucible bottom electrode moment short circuit are also removed rapidly, to draw electric arc, the pure titanium block placed in first smelting pot is to remove foreign gas in chamber further, then electric arc is aimed at the nickel on crucible, titanium biased sample makes it melt and alloying, melting electric current 90A also keeps 80 seconds, then turn-off current.Again use the electric current melting Ni-Ti alloy 80 seconds of 150A after striking, Ni-Ti alloy becomes split pole uneven after above-mentioned melting, after its cooling, utilize non-consumable vacuum arc melting furnace supporting machinery hand to be overturn by alloy pig, by aforementioned identical melting condition (150A, 80 seconds) remelting, repeats this process and makes homogenization of composition 5 ~ 6 times.Vacuum arc melting furnace is furnished with copper mold crystallizer, logical recirculated cooling water around copper mold.Copper mold lower end is connected with the forepump of equipment, and alloy pig again melts and increases melting electric current to 190A to improve its mobility.When inhaling casting, provide an instantaneous negative pressure to be sucked rapidly in copper mold by molten metal bath by vacuum pump, under the heat transfer process of copper mold and outside recirculated cooling water thereof, speed of cooling can reach 1.1 × 10
4k/S, thus has very large condensate depression.Nickel-titanium metal liquid is by inhaling after casting process realizes rapid solidification in copper mold, and the fine and close Ni-Ti alloy of obtained sheet, its typical sizes is that 70mm(is long) × 10mm(is wide) × 1.0mm(is high).Ni-Ti alloy is enclosed in vitreosil pipe, and at 950 DEG C, insulation carries out Homogenization Treatments in 1 hour, after quench in water.After Homogenization Treatments, micro-area composition can be obtained and organize uniformly.
Shape memory effect process is carried out in the following manner: it is D=74mm(ε that t=1.0mm slab-like sample is tied to diameter
t=1.33%) constraint aging being incubated 10h at 500 DEG C is carried out in circular dies; After shrend, shed mould, clean sample, obtained artificial sphincter bidirectional memory nickel-titanium alloy material.The circular dies with crooked radian radius ρ strains according to formula the forced synchroniztion that sample produces
determine, wherein t is material thickness (the present embodiment is 1.0mm), and ρ is crooked radian radius (the present embodiment is 37mm); ε
tfor flexural strain is answered, determined the forced synchroniztion strain stress of this enforcement by this formula
t=1.33%.
Fig. 3-1 occurs bending and deformation and the recording photograph recovering flat between boiled water temperature (Fig. 3-1a about 100 DEG C) Yu room temperature (Fig. 3-1b, about 30 DEG C) temperature for embodiment 3.Its maximum bending strain in boiling water is 0.60%, and the flexural strain under room temperature is 0.12%, and the bidirectional reversible dependent variable between thus from high temperature to room temperature is 0.48%.
Claims (6)
1. rapid solidification prepares the method for artificial sphincter bidirectional memory Ni-Ti alloy, it is characterized in that comprising the steps:
(1) compare for 51:49 according to nickel, titanium atom, take high purity nickel and high purity titanium raw material;
(2) step (1) raw material is put into the melting of non-consumable vacuum arc melting furnace, and with water cooled copper mould negative pressure suction casting method, molten metal is sucked in copper die cavity, after rapid solidification, obtain the material of desired shape;
(3) step (2) material is put into vitreosil pipe and passed into high-purity argon gas protection, at 800 ~ 950 DEG C of temperature, insulation carries out Homogenization Treatments in 1 ~ 10 hour, then quenches in water;
(4) will be fixed in the circular dies with crooked radian radius by material after step (3) process, the distortion that material is subject to the constraint generation of mould corresponding with mold bending radian, material is put into together with mould the constraint aging process that resistance furnace carries out being incubated at 350 ~ 500 DEG C 10 ~ 100h, then quench in water, obtained have narrow warm area response artificial sphincter bidirectional memory nickel-titanium alloy material; The crooked radian radius of described circular dies is according to formula
determine, wherein t is material thickness, unit mm; Crooked radian radius when ρ is constraint, unit mm; ε
tfor flexural strain, be 0.80% ~ 1.50%.
2. rapid solidification according to claim 1 prepares the method for artificial sphincter bidirectional memory Ni-Ti alloy, it is characterized in that: by volume percentages, and the purity of described high purity nickel is higher than 99.96%; The purity of described high purity titanium is higher than 99.76%.
3. rapid solidification according to claim 1 prepares the method for artificial sphincter bidirectional memory Ni-Ti alloy; it is characterized in that: in described non-consumable vacuum arc melting furnace, melting selects high-purity argon gas as striking and protection gas; by volume percentages, the purity of high-purity argon gas is higher than 99.999%.
4. rapid solidification according to claim 1 prepares the method for artificial sphincter bidirectional memory Ni-Ti alloy, it is characterized in that: the described material obtaining desired shape after rapid solidification is sheet, is of a size of 50 ~ 100mm × 8 ~ 10mm × 0.5 ~ 1.5mm.
5. rapid solidification according to claim 1 prepares the method for artificial sphincter bidirectional memory Ni-Ti alloy, it is characterized in that: by volume percentages, and the purity of described step (3) high-purity argon gas is higher than 99.999%.
6. rapid solidification according to claim 1 prepares the method for artificial sphincter bidirectional memory Ni-Ti alloy, it is characterized in that: the melting of non-consumable vacuum arc melting furnace put into by described step (2) raw material is that starting material are put into non-consumable vacuum arc melting furnace, first keep 60 ~ 90 seconds under the melting electric current of 80 ~ 100A; Then keep carrying out melting in 60 ~ 90 seconds under the melting electric current of 140 ~ 160A, and repeat this fusion process and make alloying constituent even 5 ~ 6 times.
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| US11672883B2 (en) * | 2017-04-28 | 2023-06-13 | Medtronic, Inc. | Shape memory articles and methods for controlling properties |
| CN108754236B (en) * | 2018-08-21 | 2019-07-26 | 山东大学 | A method of improving niti-shaped memorial alloy functional stabilization |
| CN111534770A (en) * | 2020-05-12 | 2020-08-14 | 华南理工大学 | Near-equal atomic ratio nickel-rich nickel-titanium alloy two-way shape memory effect training method |
| CN111957966A (en) * | 2020-08-28 | 2020-11-20 | 东南大学 | Method for preparing nickel-titanium two-way memory deformation component and intelligent structure through 4D printing |
| CN113106317B (en) * | 2021-03-29 | 2022-02-11 | 北京科技大学 | Preparation method of high-superelasticity NiTiHf high-temperature shape memory alloy |
| CN113215421B (en) * | 2021-04-06 | 2021-12-21 | 华南理工大学 | Low-stress driven high-elasticity all-martensite nickel-titanium alloy and preparation method thereof |
| CN114855008B (en) * | 2022-04-07 | 2023-05-23 | 华南理工大学 | Nickel-titanium alloy double-pass shape memory effect training method with high nickel-rich content |
| CN115896498B (en) * | 2022-11-22 | 2024-03-05 | 西安交通大学 | Ti-Ni-Cu shape memory alloy plate with high phase-change cycle stability and preparation method thereof |
| CN116516270A (en) * | 2023-04-03 | 2023-08-01 | 华南理工大学 | Two-step training method for efficiently improving nickel-titanium alloy double-pass shape memory effect |
| CN117144274B (en) * | 2023-10-30 | 2024-02-02 | 武汉科技大学 | Preparation method of nickel-titanium alloy and overload automatic circuit breaking protector |
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