CN1399002A

CN1399002A - Deformation induced aging-type iron-base shape memory alloy and its prepn process

Info

Publication number: CN1399002A
Application number: CN 02133699
Authority: CN
Inventors: 文玉华; 李宁; 胥永刚
Original assignee: Sichuan University
Current assignee: Sichuan University
Priority date: 2002-09-03
Filing date: 2002-09-03
Publication date: 2003-02-26
Anticipated expiration: 2022-09-03
Also published as: CN1158399C

Abstract

A strain-induced aging-type shape memory alloy features that it has austenite crystal grain the Cr23C6 second phase separated out. The alloy is prepared through solid solution treatment of alloy shapes which are obtained through smelting and casting, or forging, or cold/hot-rolling or cold-drawing of alloy contain Fe, MN, Si, Cr, Ni and C elements in a certain proportion, at temperature over 1050 deg.c for at least 0.5 hr, deforming at room temperature, and further aging at 650-1050 deg.C. The alloy gas greater, up to 72% greater, shape memory effect, simpler production process and lower cost than that of alloy prepared by the direct aging process or hot mechanical circulating training process.

Description

Deformation induced aging-type iron-base shape memory alloy and preparation method thereof

One, technical field

The invention belongs to the shape memory alloy technical field, be specifically related to a kind of deformation induced aging-type iron-base shape memory alloy and preparation method.Shape memory function with the shape memory alloy of this method preparation strengthens greatly, can be at driving mechanism, and the fields such as element and sensing member that be fastenedly connected obtain to use.

Two, background technology

Since find the FeMnSi monocrystalline have shape memory effect two during the last ten years, it is memorial alloy that people develop anti-corrosion FeMnSiCr and FeMnSiCrNi again in succession.But regrettably, these alloys all also do not enter the application stage that realizes.Tracing it to its cause, mainly is that the recovered deformation because of these alloys only is 1.5～2%, can not reach engineering and use requirement greater than 3%.In order to change this situation, the scientific worker has carried out finding behind the big quantity research that the shape memory effect of alloy derives from stress-induced austenite γ → ε martensitic transformation and reversible reverse becomes.Thereby to improve the shape memory effect of alloy, and the one, increase austenitic matrix sliding deformation critical stress σ _sWith stress-induced phase transformation critical stress σ _{γ → ε}Between difference DELTA σ; The 2nd, increase the reversible reverse sex change of stress-induced.

The requirement that satisfy to increase Δ σ just means that distortion of materials born by stress-induced γ → ε martensitic transformation as far as possible, thereby just can avoid irrecoverable distortion---the viscous deformation of perfect dislocation slippage generation.But the requirement that satisfy to increase the reversible reverse sex change of stress-induced just mean phase transformation cause being out of shape in the increase of recuperation section.

The principle that present scientific worker both domestic and external improves according to shape memory alloy recovery of shape strain, research has also reported that openly some can be used to improve the method for the shape memory effect of alloy.As people such as Gu.Q (Scripta Metall, 1994, Vol30, P1587) Bao Dao hot mechanical cycles training method.This method is meant and at room temperature applies 2～3% distortion, then annealing and the process repeatedly handled repeatedly near 600 ℃ more than the anti-phase height.Hot mechanical cycles training method has reduced the critical stress σ of stress-induced γ → ε martensitic transformation simultaneously again because the lattice defect of introducing has improved the critical stress σ s of austenitic matrix sliding deformation on the one hand _{γ → ε}, thereby increased difference DELTA σ between them; On the other hand, after the hot mechanical cycles training, ε martensite forms in the mode of compartmentation, has increased the martensitic reversible reverse sex change of ε, thereby hot mechanical cycles training can significantly improve the shape memory effect of alloy.But this treatment process is too loaded down with trivial details, and has also increased manufacturing cost simultaneously.(metal heat treatmet, 2000,6, P274) people (Scripta Metall, 1998, Vol38, P1163) Bao Dao alloyage process such as Bao Dao indeformable direct aging method and Zhao such as Wen Yuhua, Li Ning and for example.These two kinds of methods are because it can only increase austenitic matrix sliding deformation critical stress σ _sWith stress-induced phase transformation critical stress σ _{γ → ε}Between difference DELTA σ, thereby the effect of its raising is very not remarkable.

Three, summary of the invention

The objective of the invention is problem, a kind of deformation induced aging-type iron-base shape memory alloy is provided at the prior art existence.Another object of the present invention provides the method for this deformation induced aging-type iron-base shape memory alloy of preparation, and this method can make alloy obtain higher recovery of shape strain.

Deformation induced aging-type iron-base shape memory alloy provided by the invention, this alloy contain Mn, Si, Cr, Ni, C, Fe element, it is characterized in that the Cr that the austenite crystal intragranular has directivity to separate out ₂₃C ₆Second phase.This deformation induced aging-type iron-base shape memory alloy provided by the invention is prepared by method provided by the invention, this preparation method is the Mn that melting is obtained to contain certain Chemical Composition proportioning, Si, Cr, Ni, C, the alloy of Fe is through casting or forging or cold rolling or hot rolling or cold drawn section bar,＞1050 ℃ of following solution treatment after at least 0.5 hour, under 650～1050 ℃, carry out ageing treatment again, the Chemical Composition Mn 10～25% that it is characterized in that this alloy, Si 3～7%, Cr 4～16%, Ni 3～8%, C 0.06～0.3% (all being weight percentage), surplus is Fe; Section bar at room temperature must be out of shape before the ageing treatment, the deflection of section bar is 5～25%, preferred 5～15%.Because the present invention adopts after the distortion method of timeliness again, thereby second certain specific direction that hands down that makes that timeliness separates out separates out, and austenite crystal is divided into several regions, as shown in Figure 1.Just because of the effect of cutting apart of the second phase particle, during stress-induced austenite γ → ε martensitic transformation, ε martensite also forms in the compartmentation mode, thereby has improved the martensitic reversible reverse of ε.Second σ that can significantly strengthen mutually austenitic matrix again that separates out of timeliness on the other hand _sThereby, also just increased itself and σ _{γ → ε}Between difference DELTA σ, thereby significantly improved the recovery of shape strain of alloy.

Distortion back timeliness is wanted to separate out second phase, must contain the second easy mutually forming element in the alloy.Carbide is the most a kind of second phase of easy formation in the alloy, therefore the present invention has broken the carbon content that common FeMnSiCrNi is an alloy＜0.02% routine (Bergeon, Kajiwara and Kikuchi Acta Materialia, 2000 of (belonging to the Ultra-low carbon alloy), 48, P4053 and Liu Qingsuo, Zhao Liancheng, material engineering, 2000,6, P39), and adopted higher carbon content 0.06～0.3%.Because alloy contains enough carbon and chromium, thereby timeliness just can directivity is arranged be separated out Cr at the austenite crystal intragranular after being out of shape ₂₃C ₆Second phase.

Ageing treatment was preferably handled 2～6 hours down at 750～950 ℃ among the preparation method of the present invention; Preferred 1050～1200 ℃ of the temperature of solution treatment, preferred 0.5～2 hour of time.

Four, description of drawings

Fig. 1 is out of shape back aging alloy tissue morphology synoptic diagram for the present invention;

Fig. 2 is the influence of aging process to alloy recovery of shape rate;

Fig. 3 is the influence of hot mechanical cycles training to alloy recovery of shape rate;

Fig. 4 is out of shape the alloy stereoscan photograph of back timeliness for the present invention;

Fig. 5 is the alloy stereoscan photograph of indeformable direct aging;

Fig. 6 is out of shape the X-Ray diffraction spectra of back aging alloy for the present invention.

Five, embodiment

Provide embodiment below, so that the invention will be further described.It is worthy of note that the embodiment that provides can not be interpreted as limiting the scope of the invention, the person skilled in the art in this field must belong to protection domain of the present invention according to the content of the invention described above to some nonessential improvement and the adjustment that the present invention makes.

Embodiment 1～9

With the alloy that contains the Chemical Composition listed that obtains respectively after the melting silk material through cold drawn one-tenth φ 1.5mm just like subordinate list, 1150 ℃ of following solution treatment 0.5 hour, then at room temperature respectively through after 5%, 10%, 15% the distortion, under 850 ℃, carry out the ageing treatment different time again, adopt diastrophic method to be determined at the recovery of shape rate of different time at last, the maximum recovery of shape rate of gained the results are shown in subordinate list.

Comparative example 1

To contain Mn 13.53%, Si 4.86%, Cr 8.16%, Ni 3.82%, C 0.16% by what obtain after the melting, surplus is the silk material of the alloy of Fe through cold drawn one-tenth φ 1.5mm, 1150 ℃ of following solution treatment 0.5 hour, then at 850 ℃ of following indeformable ageing treatment different times that directly carry out, and adopting diastrophic method to be determined at the recovery of shape rate of different time, the maximum recovery of shape rate of gained the results are shown in subordinate list.

Comparative example 2

To contain Mn 13.53%, Si 4.86%, Cr 8.16%, Ni 3.82%, C 0.16% by what obtain after the melting, surplus is the silk material of the alloy of Fe through cold drawn one-tenth φ 1.5mm, 1150 ℃ of following solution treatment 0.5 hour, adopt 650 ℃ of best at present process annealing temperature to carry out hot mechanical cycles training then, and adopting diastrophic method to be determined at the recovery of shape rate of different frequency of training, the maximum recovery of shape rate of gained the results are shown in subordinate list.

Subordinate list

Embodiment	Alloy composition (weight percent)						Strain aging technology	Maximum recovery of shape rate (5% flexural deformation)
	Alloy composition (weight percent)								??Mn	????Si	????Cr	???Ni	????C	????Fe
	??1	? ? ? ??13.53	? ? ? ???4.86	? ? ? ???8.16	? ? ? ???3.82	? ? ? ???0.16			??Mn	????Si	????Cr	???Ni	????C	????Fe	Surplus	5%+850 ℃ of timeliness different time	300min reaches maximum value 80%
??2	??1						10%+850 ℃ of timeliness different time	180min reaches maximum value 90%								5%+850 ℃ of timeliness different time	300min reaches maximum value 80%
??2	??3						10%+850 ℃ of timeliness different time	180min reaches maximum value 90%	15%+850 ℃ of timeliness different time	300min reaches maximum value 83%
??4	??3						? ? ? ??17.80	? ? ? ???4.73	15%+850 ℃ of timeliness different time	300min reaches maximum value 83%	? ? ? ???7.80	? ? ? ???4.12	? ? ? ???0.10	Surplus		5%+850 ℃ of timeliness different time	300min reaches maximum value 84%
??4	??5	10%+850 ℃ of timeliness different time	180min reaches maximum value 92%													5%+850 ℃ of timeliness different time	300min reaches maximum value 84%
??6	??5	10%+850 ℃ of timeliness different time	180min reaches maximum value 92%	15%+850 ℃ of timeliness different time	300min reaches maximum value 83%
??6	??7	? ? ? ??21.80	? ? ? ???5.50	15%+850 ℃ of timeliness different time	300min reaches maximum value 83%	? ? ? ???11.54			? ? ? ???5.12	? ? ? ???0.22					Surplus	5%+850 ℃ of timeliness different time	300min reaches maximum value 82%
??8	??7			10%+850 ℃ of timeliness different time	180min reaches maximum value 86%											5%+850 ℃ of timeliness different time	300min reaches maximum value 82%
??8	??9			10%+850 ℃ of timeliness different time	180min reaches maximum value 86%		15%+850 ℃ of timeliness different time	300min reaches maximum value 80%
Comparative example	??9			Alloy composition (weight percent)							Treatment process	Maximum recovery of shape rate (5% flexural deformation)
	??Mn	???Si	????Cr	Alloy composition (weight percent)						??Ni			???C	????Fe
	??Mn	???Si	????Cr	??1	??13.53	???4.86	???8.16	???3.82	???0.16	??Ni			???C	????Fe	Surplus	850 ℃ of indeformable direct aging different times	300min reaches maximum value 53%
??2	650 ℃ of hot mechanical cycles training of process annealing	Train and reach maximum value 78% nine times		??1												850 ℃ of indeformable direct aging different times	300min reaches maximum value 53%

From subordinate list as can be seen: 1. the present invention adopts under the room temperature after distortion again that the method for ageing treatment can make alloy obtain good shape memory effect, alloy than indeformable direct aging method and the manufacturing of hot mechanical cycles coaching method all is greatly increased, especially more indeformable direct aging method improves morely, reach as high as 72%, thereby not only can replace the relatively poor indeformable direct aging method of effect and handle too loaded down with trivial details hot mechanical cycles coaching method, also can save manufacturing cost greatly.2. the maximum recovery of shape rate that obtained of ageing treatment alloy is the highest again after 10% distortion under the room temperature of the present invention, and required aging time is the shortest, and this can also further shorten the manufacturing cycle, saves the energy, reduces manufacturing cost.

In addition, because carbon content is higher in the alloy of the present invention, just can carries out melting without vacuum induction furnace, and adopt antivacuum induction furnace melting, this also can reduce the manufacturing cost of alloy greatly.

For the influence of two kinds of different aging process of reflection more directly perceived and hot mechanical cycles training to alloy recovery of shape rate, the present invention plots figure to embodiment 2 and comparative example 1,2 test results of being done and provides, and sees Fig. 2 and Fig. 3.

The present invention handles the microscopic pattern of back alloy in order to investigate distortion back timeliness and indeformable direct aging, respectively the sample of embodiment 2 and comparative example 1 has been made sem test, and photo is seen Fig. 4 and Fig. 5.By observing and analyzing, the second phase particle that distortion back timeliness is separated out is Cr ₂₃C ₆(this can be verified from the X-Ray diffraction spectra of Fig. 6), it is separated out along certain specific direction at the austenite crystal intragranular, sees Fig. 4; And indeformable direct aging method, though also have second to separate out mutually, precipitated phase is mainly separated out along crystal boundary, and it is non-directional to separate out the position, its quantity also distortion back timeliness separate out manyly, see Fig. 5.

Claims

1, a kind of deformation induced aging-type iron-base shape memory alloy, this alloy contain Mn, Si, Cr, Ni, C, Fe element, it is characterized in that the Cr that the austenite crystal intragranular has directivity to separate out ₂₃C ₆Second phase.

2, a kind of method for preparing the described shape memory alloy of claim 1, be that melting is obtained to contain the alloy of Chemical Composition Mn, Si, Cr, Ni, C, Fe through casting or forging or cold rolling or hot rolling or cold drawn section bar,＞1050 ℃ of following solution treatment after at least 0.5 hour, under 650～1050 ℃, carry out ageing treatment again, the Chemical Composition Mn 10～25% that it is characterized in that this alloy, Si 3～7%, Cr 4～16%, Ni 3～8%, C 0.06～0.3% (all being weight percentage), surplus is Fe; Section bar at room temperature must be out of shape before the ageing treatment.

3, the preparation method of shape memory alloy according to claim 2, the deflection that it is characterized in that section bar is 5～25%.

4, the preparation method of shape memory alloy according to claim 2, the deflection that it is characterized in that section bar is 5～15%.

5,, it is characterized in that timeliness is to handle 2～6 hours down at 750～950 ℃ according to the preparation method of claim 2 or 3 or 4 described shape memory alloys.

6, according to the preparation method of claim 2 or 3 or 4 described shape memory alloys, the temperature that it is characterized in that solution treatment is 1050～1200 ℃, and the time is 0.5～2 hour.

7, the preparation method of shape memory alloy according to claim 5, the temperature that it is characterized in that solution treatment is 1050～1200 ℃, the time is 0.5～2 hour.