EP0297004B1 - Use of a process for improving the ductility of a product made from a martensitic transformation alloy - Google Patents
Use of a process for improving the ductility of a product made from a martensitic transformation alloy Download PDFInfo
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- EP0297004B1 EP0297004B1 EP88420216A EP88420216A EP0297004B1 EP 0297004 B1 EP0297004 B1 EP 0297004B1 EP 88420216 A EP88420216 A EP 88420216A EP 88420216 A EP88420216 A EP 88420216A EP 0297004 B1 EP0297004 B1 EP 0297004B1
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- 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
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- the present invention relates to the use of a heat treatment for improving the ductility of a semi-finished metal alloy with martensitic transformation by means of a succession of hot and cold treatments, in particular to facilitate the transformation of semi-finished products into shape memory alloy.
- Document EP-A-0 161 952 discloses a process for educating a metal alloy object with martensitic transformation "with shape memory", this process consisting in imposing on the object, over one or more cycles , a series of thermal and / or mechanical stresses, the object being for example, in each cycle, treated in the austenitic phase then deformed and cooled in the martensitic phase. This education process is used to impart better memory accuracy.
- alloys with martensitic transformation exhibit poor cold deformability, which is particularly troublesome when they have to be delivered in half: products of thick or small diameter, for example between 0.5 and 3 mm.
- This insufficient ductility with respect to deformations such as rolling, drawing, drawing or hammering particularly affects the transformation into semi-finished products of certain shape memory alloys.
- alloys of the Ti-Ni 50/50 at% and Cu-Al 14 at% -Ni 4 at% types typically have deformation rates between anneals of 10% or less, which makes their cold transformation excessively long and expensive.
- the subject of the invention is the use of a heat treatment of a semi-product in martensitic transformation alloy, comprising in succession a cold treatment below the temperature M s of the start of martensitic transformation of the semi-product and a hot treatment at a temperature at least equal to 700 ° C., in order to improve the ductility of said semi-finished product with regard to its successive working, characterized in that after working said semi-working, it is subjected to a cycle of said heat treatment , the cold treatment of said cycle being carried out at a temperature both below -50 ° C and (M s -50 ° C), and the hot treatment does not result in recrystallization of the product unless it is the last heat treatment.
- Said semi-finished product is optionally subjected to at least one additional cycle following said first cycle, the cold treatment of this additional cycle being at a temperature below both -50 ° C and (M s -30 ° C) and its treatment hot being at temperature at least equal to 600 ° C. and not causing the recrystallization of said semi-finished product when it is not the last heat treatment.
- the cold and hot treatments of the successive cycles are alternated.
- each hot or cold heat treatment After each hot or cold heat treatment, the product is usually brought back to room temperature for practical reasons.
- Each hot treatment has an effect of homogenization and relaxation of internal constraints, incomplete relaxation since there is no recrystallization, the residual stresses then having a favorable effect for the cold treatment which follows it.
- Each cold treatment leads to a crystallization of fine martensite, and the succession of treatments results in homogenization with softening of the matrix and, in the martensitic phase, an increasingly fine crystallization and tending towards isotropy.
- the method of the invention makes it possible to obtain, in one or more cycles depending on the alloy considered, an exceptional ductility resulting, for example, by a multiplication by 3 of the elongation at break of the tensile test, the improvement product ductility at martensitic transformation treated is progressive, the improvement effect of each of the successive cycles decreasing, so that in practice we can limit our to at most 5 cycles and typically to 3 cycles, 80 to 95% of the improvement possible ductility then being obtained.
- the minimum temperature of the hot treatment (s) can be compared to "M s " like the temperature of the cold treatment (s) during any subsequent cycles, this hot treatment temperature then remaining at least equal to 600 ° C.
- the product in order to maintain the homogenized or partially homogenized state produced by the hot treatment or by each of the hot treatments, it is preferable to cool the product by quenching, typically a quenching with water, after this or these hot treatments .
- the product to be treated When the product to be treated is in the hot-worked state, it is it is it is preferable to start the first cycle of treatments according to the invention, which may be the only cycle of treatments, with its cold treatment.
- the heat treatments of the invention can be brief, which is a great advantage for industrial manufacturing: typically from a few seconds to 5 min for cold treatments, from 30 s to 20 min for hot treatments, processed products most often having a diameter or thickness of between 0.2 and 20 mm.
- Common cooling agents for cold treatments are liquid nitrogen (-196 ° C) and dry ice (-70 ° C), the former making it possible to treat all temperature alloys under good conditions " M s "at least equal to -145 ° C.
- Cold treatments can be carried out by soaking in the cooling agent or by passing through this agent, or by spraying this agent.
- Washers 3 mm thick cut from the bars of the three compositions were each co-laminated at around 900 ° C. between two stainless steel washers of the AISI 304 type. The assessment of the ductility is then made by simple test of folding. The laminated washers, separated from their stainless steel covers, were then immersed 3 to 4 min in liquid nitrogen, then after returning to the ambient treated 1 min at a temperature between 800 ° and 900 ° C and quenched at water, all of these cold and hot treatments constituting the first cycle of the process according to the invention. An increase in the ductility was not very noticeable for (CI) whose cold treatment temperature is 46 ° C below M s , and very clear for (C2) and (C3).
- the sequence (T3) in this case shows the surprising effect on A% of a single cycle of heat treatments according to the invention.
- the temperature at the start of recrystallization for a hot treatment of 10 min is, for the present alloy, from 910 to 920 ° C. and that risks of burns appear only above 950 ° C.
- the considerable increase in tensile elongation here corresponds to a possibility of deformation with elongation of approximately 35%, before the following annealing or softening heat treatment, instead of less than 10% previously.
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Description
La présente invention concerne l'utilisation d'un traitement thermique pour l'amélioration de la ductilité d'un demi-produit en alliage métallique à transformation martensitique au moyen d'une succession de traitements à chaud et à froid, en particulier pour faciliter la transformation de demi-produits en alliage à mémoire de forme.The present invention relates to the use of a heat treatment for improving the ductility of a semi-finished metal alloy with martensitic transformation by means of a succession of hot and cold treatments, in particular to facilitate the transformation of semi-finished products into shape memory alloy.
Par le document EP-A-0 161 952, on connaît un processus d'éducation d'un objet en alliage métallique à transformation martensitique "à mémoire de forme", ce processus consistant à imposer à l'objet, sur un ou plusieurs cycles, une série de contraintes thermiques et/ou mécaniques, l'objet étant par exemple, dans chaque cycle, traité en phase austénitique puis déformé et refroidi en phase martensitique. Ce processus d'éducation est utilisé pour conférer une meilleure précision de mémoire de forme.Document EP-A-0 161 952 discloses a process for educating a metal alloy object with martensitic transformation "with shape memory", this process consisting in imposing on the object, over one or more cycles , a series of thermal and / or mechanical stresses, the object being for example, in each cycle, treated in the austenitic phase then deformed and cooled in the martensitic phase. This education process is used to impart better memory accuracy.
Selon une préoccupation différente, celle de la fabrication des produits, beaucoup d'alliages à transformation martensitique présentent une déformabilité à froid médiocre, ce qui est particulièrement gênant lorsqu'ils doivent être livrés en demi:produits d'épaisseur ou de diamètre faible, par exemple compris(e) entre 0,5 et 3 mm. Cette ductilité insuffisante vis-à-vis de déformations telles que le laminage, le tréfilage, l'étirage ou le martelage affecte particulièrement la transformation en demi-produits de certains alliages à mémoire de forme. Ainsi, les alliages des type Ti-Ni 50/50 at % et Cu-Al 14 at %-Ni 4 at % ont typiquement des taux de déformation entre recuits de 10% ou moins, ce qui rend leur transformation à froid exagérément longue et coûteuse.According to a different concern, that of the manufacture of products, many alloys with martensitic transformation exhibit poor cold deformability, which is particularly troublesome when they have to be delivered in half: products of thick or small diameter, for example between 0.5 and 3 mm. This insufficient ductility with respect to deformations such as rolling, drawing, drawing or hammering particularly affects the transformation into semi-finished products of certain shape memory alloys. Thus, alloys of the Ti-Ni 50/50 at% and Cu-Al 14 at% -Ni 4 at% types typically have deformation rates between anneals of 10% or less, which makes their cold transformation excessively long and expensive.
La demanderesse s'est donnée pour tâche de trouver un moyen pour surmonter cet inconvénient, c'est-à-dire pour améliorer notablement la ductilité de tels alliages vis-à-vis des transformations à froid, aucune solution à ce problème n'étant à sa connaissance connue.The Applicant has given itself the task of finding a way to overcome this drawback, that is to say to significantly improve the ductility of such alloys vis-à-vis cold processing, no solution to this problem being to his known knowledge.
L'invention a pour objet l'utilisation d'un traitement thermique d'un demi-produit en alliage à transformation martensitique, comportant en succession un traitement froid en dessous de la température Ms de début de transformation martensitique du demi-produit et un traitement chaud à température au moins égale à 700°C, pour améliorer la ductilité du dit demi-produit vis à vis de ses corroyages successifs, caractérisé en ce que après un corroyage du dit demi produit on le soumet à un cycle du dit traitement thermique, le traitement froid du dit cycle étant effectué à température à la fois inférieure à -50°C et à (Ms-50°C), et le traitement chaud n'entraînant pas la recristallisation du produit sauf s'il constitue le dernier traitement thermique.The subject of the invention is the use of a heat treatment of a semi-product in martensitic transformation alloy, comprising in succession a cold treatment below the temperature M s of the start of martensitic transformation of the semi-product and a hot treatment at a temperature at least equal to 700 ° C., in order to improve the ductility of said semi-finished product with regard to its successive working, characterized in that after working said semi-working, it is subjected to a cycle of said heat treatment , the cold treatment of said cycle being carried out at a temperature both below -50 ° C and (M s -50 ° C), and the hot treatment does not result in recrystallization of the product unless it is the last heat treatment.
On soumet éventuellement ledit demi-produit à au moins un cycle supplémentaire succédant audit premier cycle, le traitement froid de ce cycle supplémentaire étant à température inférieure à la fois à -50°C et à (Ms-30°C) et son traitement chaud étant à température au moins égale à 600°C et n'entraînant pas la recristallisation du dit demi-produit lorsqu'il n'est pas le dernier traitement thermique. Les traitements froids et chauds des cycles successifs sont alternés.Said semi-finished product is optionally subjected to at least one additional cycle following said first cycle, the cold treatment of this additional cycle being at a temperature below both -50 ° C and (M s -30 ° C) and its treatment hot being at temperature at least equal to 600 ° C. and not causing the recrystallization of said semi-finished product when it is not the last heat treatment. The cold and hot treatments of the successive cycles are alternated.
Après chaque traitement thermique chaud ou froid, on fait habituellement revenir pour des raisons pratiques à la température ambiante le produit traité. Chaque traitement chaud a un effet d'homogénéisation et de relâchement des contraintes internes, relâchement incomplet puisqu'il n'y a pas recristallisation, les contraintes résiduelles ayant alors un effet favorable pour le traitement froid qui lui succède. Chaque traitement froid entraîne une cristallisation de martensite fine, et la succession des traitements entraîne une homogénéisation avec adoucissement de la matrice et, en phase martensitique, une cristallisation de plus en plus fine et tendant vers l'isotropie.After each hot or cold heat treatment, the product is usually brought back to room temperature for practical reasons. Each hot treatment has an effect of homogenization and relaxation of internal constraints, incomplete relaxation since there is no recrystallization, the residual stresses then having a favorable effect for the cold treatment which follows it. Each cold treatment leads to a crystallization of fine martensite, and the succession of treatments results in homogenization with softening of the matrix and, in the martensitic phase, an increasingly fine crystallization and tending towards isotropy.
Le procédé de l'invention permet d'obtenir, en un ou plusieurs cycles selon l'alliage considéré, une ductilité exceptionnelle se traduisant par exemple par une multiplication par 3 de l'allongement de rupture de l'essai de traction, l'amélioration de ductilité du produit à transformation martensitique traité est progressive, l'effet d'amélioration de chacun des cycles successifs allant en décroissant, de sorte qu'on peut en pratique se limiter à au plus 5 cycles et typiquement à 3 cycles, 80 à 95% de l'amélioration possible de ductilité étant alors obtenue.The method of the invention makes it possible to obtain, in one or more cycles depending on the alloy considered, an exceptional ductility resulting, for example, by a multiplication by 3 of the elongation at break of the tensile test, the improvement product ductility at martensitic transformation treated is progressive, the improvement effect of each of the successive cycles decreasing, so that in practice we can limit ourselves to at most 5 cycles and typically to 3 cycles, 80 to 95% of the improvement possible ductility then being obtained.
Les modifications surprenantes, en particulier l'amélioration de ductilité causées dans le produit par le ou les cycles de traitements thermiques selon l'invention, peuvent être en partie comprises au moyen d'une hypothèse explicative. Dans l'état initial du produit traité, il existerait à l'échelle microscopique et submicroscopique une dispersion importante des domaines de températures de transition austenite/martensite locaux autour des températures de transition moyennes telles que "Ms". La position de la température du traitement froid de l'invention par rapport à "Ms" permet alors d'obtenir la transformation martensitique dans la totalité ou la presque totalité des micro-zones du produit, tandis que le niveau de cette température de traitement plus faible que -50°C conduit, en combinaison avec les contraintes résiduelles du produit, à une cristallisation fine de martensite favorisant les effets d'homogénéisation ultérieurs. Cet effet d'un traitement froid se produit plus sûrement pour la totalité des micro-zones du produit lorsque sa température est encore plus faible par rapport à Ms et en pratique inférieure alors à (Ms-100°C). On a remarqué que, sans doute à cause du resserrement des intervalles de températures de transition locaux autour de Ms dû aux premiers traitements, on pouvait sans inconvénient remonter un peu les températures de traitement froid des cycles suivant éventuellement le premier cycle par rapport à la température "Ms", ce qui est intéressant pour une fabrication industrielle. Pour les cycles suivant le premier, on peut ainsi avoir une température maximale de (Ms-30°C) au lieu de (Ms-50°C) dans le cas général, et de (Ms-80°C) au lieu de (Ms-100°C) dans le cas des réglages préférentiels du traitement froid, cette ou ces températures de froid restant par ailleurs inférieures à -50°C. Dans le cas du ou des traitements chauds, le niveau de la température est important en lui-même pour produire un effet d'homogénéisation et un relâchement des contraintes, cette température étant alors largement au-dessus des températures de transition des microzones du produit, les températures "Ms" des alliages à transformation martensitique étant typiquement comprises entre -200°C et +250°C.The surprising modifications, in particular the improvement in ductility caused in the product by the heat treatment cycle or cycles according to the invention, can be partly understood by means of an explanatory hypothesis. In the initial state of the treated product, there would exist on a microscopic and submicroscopic scale a significant dispersion of the local austenite / martensite transition temperature ranges around average transition temperatures such as "M s ". The position of the cold treatment temperature of the invention relative to "M s " then makes it possible to obtain the martensitic transformation in all or almost all of the micro-zones of the product, while the level of this treatment temperature lower than -50 ° C leads, in combination with the residual stresses of the product, to a fine crystallization of martensite promoting the subsequent homogenization effects. This effect of a cold treatment occurs more surely for all the micro-zones of the product when its temperature is even lower compared to M s and in practice then lower than (M s -100 ° C). It was noted that, no doubt because of the tightening of the local transition temperature intervals around M s due to the first treatments, it was possible without inconvenience to slightly raise the cold treatment temperatures of the cycles possibly following the first cycle with respect to the temperature "M s ", which is advantageous for industrial manufacturing. For the cycles following the first, we can thus have a maximum temperature of (M s -30 ° C) instead of (M s -50 ° C) in the general case, and of (M s -80 ° C) at instead of (M s -100 ° C) in the case of preferential settings for the cold treatment, this or these cold temperatures also remaining below -50 ° C. In the case of hot treatment (s), the temperature level is important in itself to produce a homogenization effect and a relaxation of the stresses, this temperature then being largely above the transition temperatures of the product microzones, the temperatures "M s " of the martensitic transformation alloys being typically between -200 ° C. and + 250 ° C.
La température minimale du ou des traitements chauds peut être rapprochée de "Ms" comme la température du ou des traitements froids lors des éventuels cycles suivants, cette température de traitement chaud restant alors au moins égale à 600°C.The minimum temperature of the hot treatment (s) can be compared to "M s " like the temperature of the cold treatment (s) during any subsequent cycles, this hot treatment temperature then remaining at least equal to 600 ° C.
Par ailleurs, de façon à conserver l'état homogénéisé ou partiellement homogénéisé produit par le traitement chaud ou par chacun des traitements chauds, il est préférable de refroidir le produit par trempe, typiquement une trempe à l'eau, après ce ou ces traitements chauds.Furthermore, in order to maintain the homogenized or partially homogenized state produced by the hot treatment or by each of the hot treatments, it is preferable to cool the product by quenching, typically a quenching with water, after this or these hot treatments .
Lorsque le produit à traiter est à l'état corroyé à chaud, il est préférable de commencer le premier cycle de traitements selon l'invention, qui peut être le seul cycle de traitements, par son traitement froid.When the product to be treated is in the hot-worked state, it is it is preferable to start the first cycle of treatments according to the invention, which may be the only cycle of treatments, with its cold treatment.
Au contraire, lorsque le produit à traiter est dans un état corroyé à froid, il vaut mieux commencer le premier cycle de traitements par son traitement chaud, de façon à avoir des contraintes internes ajustées à un niveau faible avant le traitement froid.On the contrary, when the product to be treated is in a cold-worked state, it is better to start the first cycle of treatments with its hot treatment, so as to have internal stresses adjusted to a low level before the cold treatment.
On a trouvé que les traitements thermiques de l'invention pouvaient être brefs, ce qui est un grand avantage pour la fabrication industrielle: typiquement de quelques secondes à 5 min pour les traitements froids, de 30 s à 20 min pour les traitements chauds, les produits traités étant le plus souvent de diamètre ou épaisseur compris(e) entre 0,2 et 20 mm. Des agents de refroidissement habituels pour les traitements froids sont l'azote liquide (-196°C) et la neige carbonique (-70°C), le premier permettant de traiter dans de bonnes conditions selon l'invention tous les alliages de température "Ms" au moins égale à -145°C. Les traitements froids peuvent être faits par trempage dans l'agent refroidissant ou par passage au travers de cet agent, ou aspersion de cet agent.It has been found that the heat treatments of the invention can be brief, which is a great advantage for industrial manufacturing: typically from a few seconds to 5 min for cold treatments, from 30 s to 20 min for hot treatments, processed products most often having a diameter or thickness of between 0.2 and 20 mm. Common cooling agents for cold treatments are liquid nitrogen (-196 ° C) and dry ice (-70 ° C), the former making it possible to treat all temperature alloys under good conditions " M s "at least equal to -145 ° C. Cold treatments can be carried out by soaking in the cooling agent or by passing through this agent, or by spraying this agent.
Le procédé utilisé selon l'invention est particulièrement intéressant pour la transformation à froid des types d'alliages à mémoire de forme suivants:
- A_ les alliages Ti-Ni sans autre addition à 48-52 at % de chaque métal, et les alliages Ti-Ni dopés par exemple au Fe, Zr, Cu, Al ou Co, l'un au moins de ces éléments remplaçant une partie du titane ou du nickel. Leurs températures "Ms" extrêmes vont de -200 à +120°C, leurs valeurs les plus courantes sont comprises entre -150 et +100°C. Les températures de traitement chaud sont alors comprises entre 700 et 900°C, les températures de recristallisation pour les durées de traitement utilisées étant elles-mêmes habituellement supérieures à 920°C. Ces températures de traitement sont typiquement comprises entre 750°C et 850°C, les durées des traitements ou temps de maintien à température du ou des produits étant alors typiquement de 1 à 5 min pour les produits minces de diamètre ou épaisseur au plus égal(e) à 2 mm, et de 5 à 15 min pour les produits plus épais de diamètre ou épaisseur compris(e) entre 2 et 15 mm.
Les traitements froids utilisent typiquement de l'azote liquide ou de la neige carbonique. - B_ Les alliages à base cuivre (% en masse):
- · Cu-Zn-Al, typiquement à 26 à 29% de Zn et 3 à 8% de Al
- · Cu-Al-Ni, typiquement à 13 à 15% d'Al et 2 à 6% de Ni
- · Cu-Zn-Mn.
Les températures "Ms" sont typiquement comprises entre -140°C et +200°C. On utilise un cycle de traitements thermiques selon l'invention, ou 2 à 5 cycles successifs. Le traitement chaud du premier cycle est de 1 à 15 min à température choisie entre 700 et 900°C, cette durée et cette température permettant d'éviter la recristallisation du produit. Les traitements chauds des cycles suivants d'une procédure à plusieurs cycles selon l'invention peuvent être au même niveau de température ou à température plus faible au moins égale à 600°C, comme indiqué dans l'exposé général de l'invention. Les traitements froids peuvent être très brefs, spécialement lorsqu'il s'agit de fils fins ou de produits minces et qu'ils sont faits au passage (par exemple par immersion locale ou aspersion d'azote liquide). Des essais de laboratoire sur des échantillons de tôle Cu-Zn-Al d'épaisseur 0,5 mm ont montré qualitativement que les cycles de traitements thermiques de l'invention pouvaient conduire à une simplification du processus d'éducation décrit dans la demande de brevet EP-A-0161952 et appliqué à des objets découpés dans ces échantillons, sans doute à cause de l'homogénéisation fine résultant des traitements selon l'invention. Cette amélioration de l'aptitude à l'éducation intéresse les divers alliages à mémoire de forme. - C_ Les alliages à base fer, par exemple des types Fe-Mn-Si, Fe-Cr-Mn et Fe-Cr-Si.
- A_ Ti-Ni alloys without further addition to 48-52 at% of each metal, and Ti-Ni alloys doped for example with Fe, Zr, Cu, Al or Co, at least one of these elements replacing a part titanium or nickel. Their extreme "M s " temperatures range from -200 to + 120 ° C, their most common values are between -150 and + 100 ° C. The hot treatment temperatures are then between 700 and 900 ° C., the recrystallization temperatures for the treatment durations used being themselves usually greater than 920 ° C. These treatment temperatures are typically between 750 ° C. and 850 ° C., the durations of the treatments or time keeping the temperature of the product (s) then being typically from 1 to 5 min for thin products of diameter or thickness at most equal ( e) 2 mm, and 5 to 15 min for thicker products with a diameter or thickness between 2 and 15 mm.
Cold treatments typically use liquid nitrogen or dry ice. - B_ Copper-based alloys (% by mass):
- Cu-Zn-Al, typically 26 to 29% Zn and 3 to 8% Al
- Cu-Al-Ni, typically 13 to 15% Al and 2 to 6% Ni
- Cu-Zn-Mn.
The temperatures "M s " are typically between -140 ° C and + 200 ° C. A cycle of heat treatments according to the invention is used, or 2 to 5 successive cycles. The hot treatment of the first cycle is from 1 to 15 min at a temperature chosen between 700 and 900 ° C., this duration and this temperature making it possible to avoid recrystallization of the product. The hot treatments of the following cycles of a procedure with several cycles according to the invention can be at the same temperature level or at a lower temperature at least equal to 600 ° C., as indicated in the general description of the invention. Cold treatments can be very brief, especially in the case of fine wires or thin products and they are done in passing (for example by local immersion or spraying with liquid nitrogen). Laboratory tests on samples of Cu-Zn-Al sheet 0.5 mm thick have shown qualitatively that the thermal treatment cycles of the invention could lead to a simplification of the education process described in the patent application EP-A-0161952 and applied to objects cut from these samples, no doubt because of the fine homogenization resulting from the treatments according to the invention. This improvement in educational ability is of interest to the various shape memory alloys. - C_ Iron-based alloys, for example of the Fe-Mn-Si, Fe-Cr-Mn and Fe-Cr-Si types.
Outre une amélioration surprenante de la ductilité des produits en alliage à transformation martensitique facilitant considérablement leur transformation à froid ou à tiède, le procédé de l'invention apporte ainsi les avantages suivants:
- stabilisation des états austénitique et/ou martensitique, résultant de la modification avec resserrement des points et intervalles de transformation austénite/martensite locaux du produit;
- amélioration de l'aptitude à l'éducation des demi-produits en alliage à mémoire de forme.
- aucune traitement mécanique n'est associé aux traitements thermiques successifs du procédé de l'invention, ce qui facilite l'exécution de ce procédé.
- stabilization of the austenitic and / or martensitic states, resulting from the modification with tightening of the points and intervals of local austenite / martensite transformation of the product;
- improvement of the educational ability of semi-finished products in shape memory alloy.
- no mechanical treatment is associated with the successive heat treatments of the process of the invention, which facilitates the execution of this process.
Les essais qui suivent permettront d'illustrer l'application du procédé de l'invention et ses effets.The following tests will illustrate the application of the process of the invention and its effects.
On a utilisé des barres 18 mm brutes de filage à chaud en Cu-Al-Ni de 3 compositions (en % atomique)
Des rondelles d'épaisseur 3 mm découpées dans les barres des trois compositions ont été colaminées chacune à 900°C environ entre deux rondelles d'acier inoxydable du type AISI 304. L'appréciation de la ductilité est faite par la suite par simple essai de pliage. Les rondelles laminées, séparées de leurs couvertures d'acier inoxydable, ont été ensuite plongées 3 à 4 min dans l'azote liquide, puis après retour à l'ambiante traitées 1 min à température comprise entre 800° et 900°C et trempées à l'eau, l'ensemble de ces traitements froid et chaud constituant le premier cycle du procédé selon l'invention. On a constaté alors un accroissement de la ductilité peu perceptible pour (CI) dont la température de traitement froid est à 46°C au-dessous de Ms, et très net pour (C2) et (C3). On a continué sur une partie des échantillons de chaque nuance les cycles de traitements thermiques en allant jusqu'à un total de 15 cycles. Après le 3° cycle, (C2) et (C3) ont une très bonne ductilité, avec, comme on a pu le constater à l'ambiante pour (C3), une martensite fine distribuée de faon isotrope. La ductilité de (C1) est médiocre. Au bout de 15 cycles, (C2) et (C3) montrent en plus d'une très bonne ductilité une mémoire de forme. En ce qui concerne la ductilité, on a estimé que 90 à 95% de l'amélioration de ductilité était acquise au bout de 3 cycles.Washers 3 mm thick cut from the bars of the three compositions were each co-laminated at around 900 ° C. between two stainless steel washers of the AISI 304 type. The assessment of the ductility is then made by simple test of folding. The laminated washers, separated from their stainless steel covers, were then immersed 3 to 4 min in liquid nitrogen, then after returning to the ambient treated 1 min at a temperature between 800 ° and 900 ° C and quenched at water, all of these cold and hot treatments constituting the first cycle of the process according to the invention. An increase in the ductility was not very noticeable for (CI) whose cold treatment temperature is 46 ° C below M s , and very clear for (C2) and (C3). The heat treatment cycles were continued on part of the samples of each grade, going up to a total of 15 cycles. After the 3rd cycle, (C2) and (C3) have a very good ductility, with, as we have seen at the ambient for (C3), a fine martensite distributed isotropically. The ductility of (C1) is poor. After 15 cycles, (C2) and (C3) show in addition to very good ductility a shape memory. With regard to ductility, it has been estimated that 90 to 95% of the improvement in ductility is acquired after 3 cycles.
On est parti d'un lingot de Ti-Ni 50/50 at % obtenu par fusion à l'arc sous vide. Ce lingot a été transformé en barres forgées puis traitées 30 min à 700°C, dans lesquelles on a usiné des éprouvettes 0 5 mm dont l'état (To) est l'état de référence, avec un allongement de rupture à l'essai de traction de 16,9%.We started with an ingot of Ti-Ni 50/50 at% obtained by vacuum arc melting. This ingot was transformed into forged bars and then treated for 30 min at 700 ° C., in which specimens 0 5 mm were machined, the state (To) of which is the reference state, with an elongation at break under test. 16.9% traction.
Sur les éprouvettes d'état (To), on a fait une déformation par allongement sur le banc de traction suivie de traitements thermiques et d'un essai de traction, selon quatre séquences différentes à partir de l'état (To):On the state test pieces (To), a deformation was made by elongation on the traction bench followed by heat treatments and a tensile test, according to four different sequences starting from the state (To):
- · déformation avec allongement de 9,9%Deformation with 9.9% elongation
- · traitement 10 min dans l'azote liquide· Treatment 10 min in liquid nitrogen
- · essai de traction: A% = 2,4.· Tensile test: A% = 2.4.
- · déformation avec allongement de 9,7%Deformation with 9.7% elongation
- · traitement 10 min à 500°C + trempe à l'eau· Treatment 10 min at 500 ° C + water quenching
- · essai de traction: A% = 11,6.· Tensile test: A% = 11.6.
- · déformation avec allongement de 9,8%Deformation with 9.8% elongation
- · traitement 10 min à 800°C + trempe à l'eau· Treatment 10 min at 800 ° C + water quenching
- · traitement 10 min dans l'azote liquide, retour à l'ambiante· Treatment 10 min in liquid nitrogen, return to ambient
- · essai de traction: A% = 49.Tensile test: A% = 49.
- · déformation avec allongement de 10%, provoquant la rupture de la barreDeformation with 10% elongation, causing the bar to break
- · par traitement à 800°C non suivi d'un traitement froid selon l'invention, on aurait obtenu un A% légèrement amélioré, soit environ 15 à 20%.· By treatment at 800 ° C not followed by a cold treatment according to the invention, a slightly improved A% would have been obtained, ie approximately 15 to 20%.
La séquence (T3) montre dans ce cas l'effet surprenant sur A% d'un seul cycle de traitements thermiques selon l'invention. Il est à remarquer que la température de début de recristallisation pour un traitement chaud de 10 min est, pour le présent alliage, de 910 à 920°C et que des risques de brûlure n'apparaissent qu'au-dessus de 950°C. L'augmentation considérable de l'allongement de traction correspond ici à une possibilité de déformation avec allongement de 35% environ, avant le traitement thermique de recuit ou d'adoucissement suivant, au lieu de moins de 10% précédemment.The sequence (T3) in this case shows the surprising effect on A% of a single cycle of heat treatments according to the invention. It should be noted that the temperature at the start of recrystallization for a hot treatment of 10 min is, for the present alloy, from 910 to 920 ° C. and that risks of burns appear only above 950 ° C. The considerable increase in tensile elongation here corresponds to a possibility of deformation with elongation of approximately 35%, before the following annealing or softening heat treatment, instead of less than 10% previously.
L'utilisation d'un cycle de traitements thermiques selon l'invention au lieu du ou des recuits intermédiaires classiques permet de continuer la transformation avec des déformations importantes entre traitements intermédiaires.The use of a heat treatment cycle according to the invention instead of the conventional intermediate annealing (s), the transformation can continue with significant deformations between intermediate treatments.
Claims (14)
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR8709272 | 1987-06-24 | ||
| FR8709272A FR2617187B1 (en) | 1987-06-24 | 1987-06-24 | METHOD FOR IMPROVING THE DUCTILITY OF A MARTENSITICALLY TRANSFORMED ALLOY PRODUCT AND THE USE THEREOF |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| EP0297004A2 EP0297004A2 (en) | 1988-12-28 |
| EP0297004A3 EP0297004A3 (en) | 1989-06-28 |
| EP0297004B1 true EP0297004B1 (en) | 1991-05-08 |
Family
ID=9352719
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP88420216A Expired - Lifetime EP0297004B1 (en) | 1987-06-24 | 1988-06-22 | Use of a process for improving the ductility of a product made from a martensitic transformation alloy |
Country Status (5)
| Country | Link |
|---|---|
| US (1) | US4878954A (en) |
| EP (1) | EP0297004B1 (en) |
| JP (1) | JPS6421042A (en) |
| DE (1) | DE3862691D1 (en) |
| FR (1) | FR2617187B1 (en) |
Families Citing this family (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0328319A (en) * | 1989-06-26 | 1991-02-06 | Nisshin Steel Co Ltd | Pipe joint made of stainless steel and its production |
| JPH0645822B2 (en) * | 1990-04-18 | 1994-06-15 | 川崎製鉄株式会社 | Method of manufacturing martensitic stainless steel pipe |
| FR2699263B1 (en) * | 1992-12-15 | 1995-01-27 | Cryotechnologies | Chiller fitted with a cold finger fitted with a thermal coupler. |
| US6106642A (en) * | 1998-02-19 | 2000-08-22 | Boston Scientific Limited | Process for the improved ductility of nitinol |
| US6149742A (en) * | 1998-05-26 | 2000-11-21 | Lockheed Martin Corporation | Process for conditioning shape memory alloys |
| WO2003064717A1 (en) * | 2002-02-01 | 2003-08-07 | Mide Technology Corporation | Enhery aborbring shape memory alloys |
| DE102004052962A1 (en) * | 2004-10-29 | 2006-05-04 | Linde Ag | Shut-off valve and method for producing a shut-off valve |
| CN102011038B (en) * | 2010-12-15 | 2012-02-29 | 河北师范大学 | Mn50Ni50-xAlx high-temperature ferromagnetic shape memory alloy material and preparation method thereof |
| CN114570948B (en) * | 2022-02-15 | 2023-04-11 | 中南大学 | Post-processing method for shape control of shape memory alloy part manufactured by additive manufacturing |
| CN115807199B (en) * | 2022-11-24 | 2023-12-22 | 新疆大学 | Method for simultaneously improving yield strength and plasticity of bulk amorphous alloy composite material |
Family Cites Families (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4067752A (en) * | 1973-11-19 | 1978-01-10 | Raychem Corporation | Austenitic aging of metallic compositions |
| DE3065930D1 (en) * | 1980-03-03 | 1984-01-26 | Bbc Brown Boveri & Cie | Memory alloy based on cu-al or on cu-al-ni and process for the stabilisation of the two-way effect |
| US4304613A (en) * | 1980-05-12 | 1981-12-08 | The United States Of America As Represented By The Secretary Of The Navy | TiNi Base alloy shape memory enhancement through thermal and mechanical processing |
| JPS58151445A (en) * | 1982-02-27 | 1983-09-08 | Tohoku Metal Ind Ltd | Titanium-nickel alloy having reversible shape storage effect and its manufacture |
| DE3370828D1 (en) * | 1982-05-13 | 1987-05-14 | Leuven Res & Dev Vzw | Process for thermally treating heat recoverable metallic articles and articles thereby obtained |
| US4502896A (en) * | 1984-04-04 | 1985-03-05 | Raychem Corporation | Method of processing beta-phase nickel/titanium-base alloys and articles produced therefrom |
| FR2563055A1 (en) * | 1984-04-12 | 1985-10-18 | Souriau & Cie | METHOD OF MAKING CONNECTOR |
| EP0176272B1 (en) * | 1984-09-07 | 1989-10-25 | Nippon Steel Corporation | Shape memory alloy and method for producing the same |
| JPS63654A (en) * | 1986-06-19 | 1988-01-05 | Fujitsu Ltd | Inter-processor communication control system |
| JP2606842B2 (en) * | 1987-05-30 | 1997-05-07 | 株式会社東芝 | Electric vacuum cleaner |
| JP2506853B2 (en) * | 1987-11-25 | 1996-06-12 | 松下電器産業株式会社 | Cooking device |
-
1987
- 1987-06-24 FR FR8709272A patent/FR2617187B1/en not_active Expired
-
1988
- 1988-06-17 US US07/208,035 patent/US4878954A/en not_active Expired - Fee Related
- 1988-06-22 DE DE8888420216T patent/DE3862691D1/en not_active Expired - Fee Related
- 1988-06-22 JP JP63154540A patent/JPS6421042A/en active Granted
- 1988-06-22 EP EP88420216A patent/EP0297004B1/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| EP0297004A3 (en) | 1989-06-28 |
| FR2617187B1 (en) | 1989-10-20 |
| FR2617187A1 (en) | 1988-12-30 |
| EP0297004A2 (en) | 1988-12-28 |
| DE3862691D1 (en) | 1991-06-13 |
| JPS6421042A (en) | 1989-01-24 |
| US4878954A (en) | 1989-11-07 |
| JPH036986B2 (en) | 1991-01-31 |
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