EP0382109A1 - Verfahren zur Behandlung eines Werkstücks aus einer metallischen Formgedächtnislegierung mit zwei umkehrbaren Formgedächtniszuständen - Google Patents

Verfahren zur Behandlung eines Werkstücks aus einer metallischen Formgedächtnislegierung mit zwei umkehrbaren Formgedächtniszuständen Download PDF

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Publication number
EP0382109A1
EP0382109A1 EP90102048A EP90102048A EP0382109A1 EP 0382109 A1 EP0382109 A1 EP 0382109A1 EP 90102048 A EP90102048 A EP 90102048A EP 90102048 A EP90102048 A EP 90102048A EP 0382109 A1 EP0382109 A1 EP 0382109A1
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EP
European Patent Office
Prior art keywords
state
shape memory
temperature
austenitic
phase
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP90102048A
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English (en)
French (fr)
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EP0382109B1 (de
Inventor
Guy Grenouillet
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Nivarox Far SA
Nivarox SA
Original Assignee
Nivarox Far SA
Nivarox SA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from CH428/89A external-priority patent/CH677677A5/fr
Priority claimed from FR8901764A external-priority patent/FR2643086B1/fr
Application filed by Nivarox Far SA, Nivarox SA filed Critical Nivarox Far SA
Publication of EP0382109A1 publication Critical patent/EP0382109A1/de
Application granted granted Critical
Publication of EP0382109B1 publication Critical patent/EP0382109B1/de
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
    • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
    • C22F1/006—Resulting in heat recoverable alloys with a memory effect

Definitions

  • the invention relates to a method for packaging parts made of metal alloy capable of undergoing a reversible transformation from the state of crystallographic phase of austenitic type to a state of crystallographic phase of martensitic type, and relates in particular to the packaging of parts having complex configurations for the reversible memorization by these of two states of shape memory.
  • the process can be broken down into two series of operations, namely the preparation of the part to be educated and the education of the part itself.
  • This preparation essentially comprises three successive operations during which the part is first shaped according to a configuration constituting a first state of shape memory, then heated in order to be brought into a state of austenitic phase and finally cooled and stabilized at a temperature close to room temperature.
  • the education method comprises the operations consisting successively of deforming the part in order to bring it into the configuration constituting its second state of shape memory by subjecting it, at ambient temperature, to mechanical stress, to subject this part under mechanical stress to lower the temperature as it is brought into a martensitic phase state, to remove the mechanical stress, and to heat the part to a temperature such that it is again brought into a phase state austenitic so that it resumes the configuration constituting its first state of shape memory.
  • This cycle can be repeated a number of times to complete the education.
  • the main object of the invention is therefore to remedy the drawbacks of the above-mentioned prior art.
  • the subject of the present invention is a method of conditioning a piece of metal alloy capable of undergoing a reversible transformation from the state of crystallographic phase of austenitic type to state of crystallographic phase of martensitic type for memorization.
  • reversible of two states of shape memory including the operations consisting - to conform, at room temperature, the part to the form constituting the first state of shape memory, to mechanically maintain the part in its first state of shape memory and to heat the part thus maintained to bring it into a state of austenitic crystallographic phase, and - subjecting the mechanically maintained part to a sudden lowering of the temperature, then to a thermal stabilization treatment while retaining its austenitic phase state, and - to submit the part to an education process, in order to conform it in the second state of shape memory.
  • the part is prepared while being maintained in a configuration corresponding precisely to its first state of shape memory so that it retains the desired initial conformation, whatever the complexity of its geometry.
  • the education method consists in subjecting the stabilized part in its austenitic state to a sudden lowering of temperature to bring the part into a martensitic state, while simultaneously imposing on it a mechanical stress intended for the conform in the second state of shape memory.
  • this education method further comprises an operation consisting in subjecting the part in its second state of shape memory and maintained under said mechanical stress, to a series of thermal stresses to bring the part alternately from a martensitic state to an austenitic state.
  • the packaging method according to the invention allows the preparation and education of metal alloy parts with shape memory for the purpose of their memorization, in a reversible manner, of two states of shape memory.
  • the transition from one phase state to another takes place in one direction as in the other in a temperature range.
  • the temperature at which the austenitic phase begins to appear when the alloy is heated is called As and the temperature at which the phase formation is completed is called Af (Af> As).
  • Af the temperature at which the phase formation is completed.
  • Ms and Mf the temperatures at the start and end of the martensitic phase transformation are called Ms and Mf respectively (Mf ⁇ Ms).
  • Ms and Mf are significantly lower than Af and As respectively, the temperature intervals [As, Af] and [Ms, Mf] being dependent on the composition of the alloy.
  • Figure 1 is a graph whose abscissa axis represents time and the ordinate axis of temperature. This graph schematically represents the thermal cycles and the configurations of a part P to be conditioned, during the successive operations 01, 02 ... O7 of the process.
  • the first two operations 01 and 02 are carried out at ambient temperature T1, that is to say from 0 ° to 50 ° C. approximately.
  • ambient temperature T1 that is to say from 0 ° to 50 ° C. approximately.
  • the reference temperatures As, Af, Ms, Mf can be higher or lower than ambient temperature, depending on the metal alloy used. These temperatures can be lower than 0 ° C, or higher than 0 ° C as shown on the graph.
  • the part P is shaped using appropriate configuration means according to a determined configuration.
  • This configuration which constitutes a first state of shape memory corresponds to the configuration of the part at high temperature.
  • the part thus shaped is then placed in a device in which it can be maintained under mechanical stress ⁇ (tension, compression or other) and / or simply supported, for example by a template, depending on the complexity of its geometry (operation 02). Thanks to this holding and / or support, it overcomes the inherent elasticity problems of the deformed part and the mechanical strength problems of the part during heat treatments. As a result, the part precisely retains its first state of shape memory.
  • mechanical stress ⁇ tension, compression or other
  • / or simply supported for example by a template, depending on the complexity of its geometry
  • the part is then subjected to a rise in temperature to be brought into a state of austenitic crystallographic phase (operation 03).
  • operation 03 heating is carried out at the heart of the part to a temperature T3 comprised in a range extending from approximately 600 ° to 850 ° C depending on the alloy considered.
  • This heating is carried out, for example, in a conventional chamber oven, the latter having been previously heated.
  • the passage time of the part in the oven must be as short as possible, taking into account the shape and size of the part, in order to avoid evaporation of the light metals of the alloy. Indeed, such evaporation results in a modification of the composition of the alloy and therefore a significant modification of the thermal (transition points, etc.) and mechanical (elastic limit, etc.) characteristics. which risks modifying the ability to educate the alloy on the one hand, and the temperature range of use of the part on the other hand.
  • the part still maintained and / or supported is subjected to a sudden cooling down to a temperature T4 (operation 04).
  • the lowering of the temperature achieved, for example, by means of quenching, allows the fixation of the austenitic phase.
  • the temperature T4 reached after cooling must be higher than the temperature Af otherwise the education potential of the part is lost, the latter having, in this case, passed through its austenitic-martensitic phase transformation zone without changing the configuration.
  • the temperature T4 to which the part is cooled must be chosen so that any appearance of a parasitic phase, that is to say a phase other than austenite or associated with austenite, is avoided.
  • heat treatment is carried out to stabilize the part (operation 05).
  • This treatment consists in maintaining the part for a few tens of hours at a temperature T5 higher than Af and, for example, equal to the temperature T4 to which the part has been previously cooled.
  • This treatment allows a structural reorganization of the alloy and in particular makes it possible to release the internal stresses and to eliminate the gaps and other punctual defects which could have appeared during the sudden cooling.
  • the room temperature between the two operations 04 and 05 must remain a few tens of degrees above the temperature Af.
  • the part obtained being stabilized in its first state of shape memory can then be subjected to an education process.
  • the part prepared according to the invention (operations 01 to 05) can be educated according to the education process described in patent application EP-A1-161 952.
  • this education process requires, as mentioned above, numerous manipulations of the parts which makes it not very advantageous in the context of mass production.
  • an educational method is advantageously used according to the invention in which the part is first subjected to a sudden lowering of temperature to bring it into a martensitic state, while simultaneously imposing on it a mechanical stress intended to conform it in the second state of shape memory (operation 06). At this time, the play is already educated. Again, by lowering the temperature to bring the part into a martensitic state is meant a lowering to a temperature T6 lower than Mf.
  • This operation consists in subjecting the part mechanically maintained in its second state of shape memory to a series of thermal stresses to bring it alternately from the martensitic state to the austenitic state.
  • the education obtained is all the more effective as the number of thermal stresses is large and / or as the metal alloy used is of good quality.
  • FIGS. 2 and 3 show a helical spring 2 respectively in its first and second shape memory states.
  • the first state of shape memory corresponds to the shape of the spring at high temperature (T> Af) while the second state corresponds to the shape of the spring at low temperature (T ⁇ Mf).
  • the spring 2 has in its form at high temperature turns 4 spaced apart from one another by a pitch X and has in its form at low temperature, its turns 4 spaced apart by a pitch Y where X> Y.
  • pitch X the choice of the shapes of the parts at high and low temperatures is arbitrary and depends essentially on the application of these.
  • the following operation consists in energizing the spring 2 at ambient temperature so that it takes the configuration corresponding to its first state of shape memory.
  • the spring is fixed, for example, by each of its ends to a support device 6.
  • This support can be constituted by a gutter, the edges 8 of the walls of the latter being each engaged between two turns of a end of the spring.
  • a support device having a thermal inertia lower than or equal to that of the spring so as not to disturb the effects of subsequent heat treatments.
  • the support has been produced from a stainless steel mesh in order to avoid diffusion of the materials constituting the support on the part to be packaged.
  • the spring 2 placed on the support (that is to say under tension) is subjected to a temperature of approximately 750 ° C. in order to bring the spring in a certain manner into the state of austenitic phase.
  • the spring is introduced, for example, into a conventional chamber oven, the latter having been preheated for two hours at 750 ° C.
  • the spring is then kept in the oven for a few minutes, this time actually corresponding to the time necessary to carry out an austenitic transformation at the heart of the spring. Consequently, the heating time depends on the shapes and dimensions of the spring, and for reasons already explained above, the heating time must be as short as possible.
  • the spring retains its configuration during heating, and this even at high temperature, the tension under which it is kept preventing it from sagging despite the state of softening of the material at this temperature.
  • the austenitic phase is fixed (FIG. 7). This fixing is carried out by suddenly cooling the part to a temperature above Af while avoiding the formation of parasitic phases. In the case of the spring, it is cooled to a temperature 20 to 30 ° C higher than the temperature Af of the alloy, that is to say about 90 to 100 ° C.
  • This abrupt lowering of the temperature consists in quenching the spring in a bath thermostatically controlled at approximately 100 ° C.
  • This bath contains a heat-transfer fluid having characteristics of rapid and homogeneous cooling.
  • cryothermal types of oils are used in this temperature range, for example, a silicone oil of the type sold under the name Rhodorsil manufactured by Rhone Poulenc.
  • quenching can easily be carried out in water at ambient temperature.
  • the spring 2 is subjected to a thermal stabilization treatment (FIG. 8) in order to reorganize the crystal structure of the alloy and to release the internal stresses.
  • This treatment consists in keeping the spring in the bath in which it has been cooled for 10 to 20 hours, the latter having not been removed after the previous step. Since the configuration of the spring in its first shape memory state was fixed at the same time as the quenching, it is no longer necessary to keep the latter under tension.
  • FIG. 9 illustrates the essential operation of education, this operation consisting in simultaneously subjecting the spring 2, on the one hand, to a mechanical compressive stress C, in order to conform it in its second state of shape memory. and, on the other hand, to a sudden lowering of the temperature, namely, to a temperature lower than Mf.
  • the spring undergoes a so-called martensitic quenching at a temperature between 0 ° and 20 ° C, the spring being pinched, for example, between the edges 10 of a gutter 12 in order to reduce its pitch .
  • the conformation of the spring in its low temperature form is carried out in the temperature range between Af and Mf.
  • the spring while remaining subject to the above mechanical stress, is alternately heated to a temperature above Af, ie 90 ° to 110 ° C, then to sudden cooling to a temperature below Mf, ie from 0 ° to 20 ° C for the alloy in question this being repeated a few tens of times.
  • the support allowing the spring to be held under stress in its second shape memory state, is designed to allow the education of a large number of springs simultaneously. This eliminates the manipulation of the springs inherent in the process of the prior art described above.

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  • Chemical & Material Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Springs (AREA)
  • Heat Treatment Of Steel (AREA)
EP19900102048 1989-02-08 1990-02-02 Verfahren zur Behandlung eines Werkstücks aus einer metallischen Formgedächtnislegierung mit zwei umkehrbaren Formgedächtniszuständen Expired - Lifetime EP0382109B1 (de)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
CH428/89 1989-02-08
CH428/89A CH677677A5 (de) 1989-02-08 1989-02-08
FR8901764 1989-02-10
FR8901764A FR2643086B1 (fr) 1989-02-10 1989-02-10 Procede de conditionnement d'une piece en alliage metallique a memoire de forme presentant deux etats de memoire de forme reversibles

Publications (2)

Publication Number Publication Date
EP0382109A1 true EP0382109A1 (de) 1990-08-16
EP0382109B1 EP0382109B1 (de) 1993-12-08

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EP19900102048 Expired - Lifetime EP0382109B1 (de) 1989-02-08 1990-02-02 Verfahren zur Behandlung eines Werkstücks aus einer metallischen Formgedächtnislegierung mit zwei umkehrbaren Formgedächtniszuständen

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EP (1) EP0382109B1 (de)
DE (1) DE69004986D1 (de)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2681331A1 (fr) * 1991-09-17 1993-03-19 Imago Procede de modification des temperatures caracteristiques de transformation d'un alliage metallique a memoire de forme.
EP0709482A1 (de) * 1994-10-28 1996-05-01 Kazuhiro Otsuka Verfahren zur Herstellung von Formgedächtnislegierungen mit hoher Umwandlungstemperatur
CN112570715A (zh) * 2019-09-30 2021-03-30 上海微创医疗器械（集团）有限公司 一种结构件及其加工方法
CN114570948A (zh) * 2022-02-15 2022-06-03 中南大学 一种对增材制造形状记忆合金零件控形的后处理方法

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4283233A (en) * 1980-03-07 1981-08-11 The United States Of America As Represented By The Secretary Of The Navy Method of modifying the transition temperature range of TiNi base shape memory alloys
EP0035069A1 (de) * 1980-03-03 1981-09-09 BBC Aktiengesellschaft Brown, Boveri & Cie. Formgedächtnislegierung auf der Basis von Cu/Al oder Cu/Al/Ni und Verfahren zur Stabilisierung des Zweiwegeffektes
EP0161952A2 (de) * 1984-04-12 1985-11-21 Souriau Et Cie Verfahren zur Bedienung eines Zustands zu einem Gegenstand auf eine Formgedächtnislegierung mit zwei reversiblen Gedächtniszuständen

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0035069A1 (de) * 1980-03-03 1981-09-09 BBC Aktiengesellschaft Brown, Boveri & Cie. Formgedächtnislegierung auf der Basis von Cu/Al oder Cu/Al/Ni und Verfahren zur Stabilisierung des Zweiwegeffektes
US4283233A (en) * 1980-03-07 1981-08-11 The United States Of America As Represented By The Secretary Of The Navy Method of modifying the transition temperature range of TiNi base shape memory alloys
EP0161952A2 (de) * 1984-04-12 1985-11-21 Souriau Et Cie Verfahren zur Bedienung eines Zustands zu einem Gegenstand auf eine Formgedächtnislegierung mit zwei reversiblen Gedächtniszuständen

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2681331A1 (fr) * 1991-09-17 1993-03-19 Imago Procede de modification des temperatures caracteristiques de transformation d'un alliage metallique a memoire de forme.
EP0709482A1 (de) * 1994-10-28 1996-05-01 Kazuhiro Otsuka Verfahren zur Herstellung von Formgedächtnislegierungen mit hoher Umwandlungstemperatur
CN112570715A (zh) * 2019-09-30 2021-03-30 上海微创医疗器械（集团）有限公司 一种结构件及其加工方法
CN112570715B (zh) * 2019-09-30 2022-10-25 微创投资控股有限公司 一种结构件及其加工方法
CN114570948A (zh) * 2022-02-15 2022-06-03 中南大学 一种对增材制造形状记忆合金零件控形的后处理方法

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EP0382109B1 (de) 1993-12-08
DE69004986D1 (de) 1994-01-20

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