EP1584697A2 - Titanium-aluminium alloy having high-temperature ductility - Google Patents

Titanium-aluminium alloy having high-temperature ductility Download PDF

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EP1584697A2
EP1584697A2 EP05290750A EP05290750A EP1584697A2 EP 1584697 A2 EP1584697 A2 EP 1584697A2 EP 05290750 A EP05290750 A EP 05290750A EP 05290750 A EP05290750 A EP 05290750A EP 1584697 A2 EP1584697 A2 EP 1584697A2
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aluminum
alloys
iron
ductility
molybdenum
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EP1584697A3 (en
EP1584697B1 (en
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Marc Thomas
Agnès Bachelier-Locq
Shigehisa Naka
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Office National dEtudes et de Recherches Aerospatiales ONERA
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C14/00—Alloys based on titanium
    • 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
    • C22F1/16—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of other metals or alloys based thereon
    • C22F1/18—High-melting or refractory metals or alloys based thereon
    • C22F1/183—High-melting or refractory metals or alloys based thereon of titanium or alloys based thereon

Definitions

  • the invention relates to an alloy consisting of aluminum aluminide titanium in which a minority fraction of the atoms of aluminum and titanium is replaced by other atoms.
  • TiAl intermetallic alloys find a advantageous use at high temperature in turbomachines aeronautical.
  • TiAl is characterized by its weak density which gives it a mechanical resistance to hot relative to the density higher than that of the conventional titanium alloys and even to that of some superalloys of nickel. This is due to a limit of elasticity which remains constant typically between 20 and 700 ° C. Nevertheless, the low ductility of this alloy is of a nature to compromise its use for rotating parts. So research is being done around the world for the development of transformation ranges that ductilize TiAl to allow the introduction of this material in aeronautical turbomachines. The work is parallel on the choice of shades most suited to such or such range of transformation.
  • the object of the present invention is to provide an alloy of TiAl type having high ductility when hot, while retaining the usual mechanical properties for these alloys.
  • the invention aims in particular at an alloy of the kind defined in introduction, and provides that it contains in atoms 44 to 49% of aluminum, 0.5 to 3% of zirconium, 0.5 to 2% of iron, 0.5 to 2% molybdenum, 0.2 to 0.5% silicon and 0 to 3% niobium.
  • the subject of the invention is also a method of treatment of an alloy as defined above, in which its constituent elements are put in solution by heating to a temperature of between 1200 ° C and 1350 ° C, cool to room temperature and annealing at a temperature between 800 ° C and 950 ° C.
  • the dissolution is carried out at 1250 ° C. about 4 hours and annealing at 900 ° C. about 4 hours.
  • alloy grades of the TiAl type (or more briefly "TiAl alloys") with high aluminum content 48% are more ductile and less resistant than shades with low aluminum content such as 44%.
  • contents greater than 48% the trend reverses quickly with reduced ductility then creep resistance and oxidation resistance are find improved.
  • the aluminum content must be locked in a window of very narrow composition (47-48 %) to ensure a good compromise of properties.
  • this high sensitivity of the aluminum content of TiAl alloys is a serious handicap for their development which requires a very high degree of precision in quantities of added elements. An ingot of several kilograms can thus present variations in levels in aluminum greater than 1% in different places, with consequence of the different properties, which may differ from user specifications.
  • aluminum is volatile during the merger, causing a loss of aluminum concentration which is dependent on the number of mergers. This is another reason why he is difficult to scrupulously respect the levels in nominal aluminum.
  • Iron has the effect of enlarging the window of aluminum for which the good compromise of properties is respected. In other words, the properties of ductility and mechanical strength remain constant over a wider aluminum content range, thus making the delicate manufacturing of alloys to obtain the desired properties.
  • TiAl alloys containing iron are distinguished by a another way. While almost all TiAl alloys in the poured state plastically deform only at temperatures above 800 ° C, the shades containing Iron can deform plastically at lower temperatures. The brittle-ductile transition temperature is indeed very brutal for all TiAl alloys which can therefore be classified according to this characteristic. A big number of elementary additives proved to be ineffective in the past to improve ductility at temperatures below 800 ° C. However, it has been found that the addition joint of iron and zirconium makes TiAl alloys even more ductile at 800 ° C. The advantage then removed is to be able to manufacture them by resorting to traditional shaping processes using temperatures compatible with common tools.
  • the only penalizing effect of iron that has been found is a decrease in creep resistance, which may lead to the addition of iron to small amounts (around 1%).
  • the use of silicon in the present invention can compensate for this effect by providing an extremely fast gain creep resistance, which limits its concentration at 0.5%. Indeed, higher silicon contents are discouraged because they cause the precipitation of silicides that are known to be detrimental to the ductility.
  • zirconium With regard to zirconium, it has been found that high level (5%) had the effect of delaying the transition fragile-ductile towards high temperatures and therefore counteract the beneficial effect of iron. Therefore, the zirconium content to be used must be significantly lower at 5 %. It is also preferable to limit the content of zirconium for density reasons. Finally, Macroscopic properties of TiAl can be affected by presence of zirconium due to steric effects which predominate over electronic effects. Works made by the inventors made it possible to verify that was not desirable to incorporate more than 2 to 3% of zirconium to maintain an acceptable compromise resistance-ductility.
  • the alloys according to the invention correspond to the poured state high hot ductility requirements allowing their implementation form by anisothermic forging.
  • the alloys described in the examples below were manufactured using vacuum arc melting.
  • the ingots were then subjected to isostatic compaction at 1250 ° C for the closure of porosities and shrinkage.
  • the comparative characterization of the alloys took place after compaction and heat treatment.
  • the heat treatment comprises a solution of 4 hours at 1250 ° C followed by a cooling of the oven and a stress relieving annealing of 4 hours at 900 ° C. This treatment aims to generate two types of structures according to the aluminum concentration.
  • the alloys according to the invention comprise on the one hand an addition of zirconium, and on the other hand additions of elements W, Mo, Fe and Cr which are known as ⁇ -generic elements, in that they stabilize the formation of the ⁇ phase.
  • the hot ductility is determined by the tensile properties at 800 ° C. Since these alloys must retain sufficient cold ductility to allow the machining and handling of parts, tensile properties at 20 ° C have also been determined.
  • a first series of tests is intended to test the combination of hardening elements (W, Mo) and a ductilizing element (Zr). Alloys containing either 2% W or 1% W + 1% Mo are prepared with, for each of these combinations, two values of Al + Mo, the aluminum content being thus chosen slightly lower in the presence of molybdenum because of the more low power ⁇ -gene molybdenum compared to that of tungsten.
  • the second series of shades is characterized by the following compositions: 1031 Ti-45Al-2W-2Cr-1ZR (Ti-29,1Al-8,8W-2,5Cr-2,2Zr) 1032 Ti-47Al-2W-2Cr-1ZR (Ti-30,7Al-8,9W-2,5Cr-2,2Zr) 1033 Ti-46Al-1FE-1W-1ZR (Ti-30,5Al-1,4Fe-4,6W-2,3Zr) 1034 Ti-48Al-1FE-1W-1ZR (Ti-32,6Al-1,4Fe-4,6W-2,3Zr)
  • the aim of this series is to test the combination of a single hardening element (W) and several ductilizing elements (Cr, Fe, Zr), which led to a reduction of 1% in the zirconium content (Table 2).
  • the ductility results reveal that the elongations do not exceed 1% at 20 ° C. Tungsten clearly appears to be responsible for this fragility at low temperature, which confirms the results of the first series.
  • a 1% reduction in the hardening element content (W) is reflected in a softening manner. It should be noted that the two grades containing iron are characterized by the same ductility at 20 ° C despite the difference in aluminum content, a behavior that contrasts with other pairs of grades.
  • the single figure represents, for the alloys of the two previous series, the elastic limit and elongation at break at 20 ° C as a function of the aluminum content.
  • the points corresponding to each property are located approximately on a straight line.
  • ductility and the yield strength there is an inverse relationship between ductility and the yield strength.
  • the increase in ductility and the decrease in the yield strength as observed on the richer aluminum compositions are related to two microstructural changes.
  • the richer aluminum grade firstly has a higher monolithic ⁇ volume fraction (and correspondingly a lower lamellar fraction); however, it is known that duplex structures are more ductile and less resistant than fully lamellar structures. In addition, this shade is less rich in ⁇ phase.
  • the Ti-48Al-1Fe-1W-1Zr grade is predominantly composed of monolithic ⁇ -phase and the low volume fraction of lamellae no longer makes it possible to fractionate the grain size, which explains the level of ductility slightly reduced at ambient temperature than for other additions.
  • the incorporation of iron produces a particular effect since it makes it possible to reach a certain level of ductility for the standard heat treatment, in this case 0.8% for the alloy Ti-46Al-1Fe-1W- 1Zr, which is not the case for other shades rich in titanium.
  • the Ti-46Al-1Fe-1W-1Zr grade is characterized by the presence of a high amount of ⁇ - phase while the Ti-48Al-1Fe-1W-1Zr grade has a majority of monolithic ⁇ -phase. and a phase minority ⁇ .
  • the third series of shades is characterized by additions of iron, zirconium and molybdenum. Two shades correspond to a substitution of Mo to W with respect to the preferred shades above. The other two grades are characterized by the absence of molybdenum: 1144 Ti-46Al-1FE-1ZR-0,2Si (Ti-32A1-1,4Fe-2,4Zr-0,2Si) 1145 Ti-47Al-1FE-1ZR-0,2Si (Ti-32,9Al-1,4Fe-2,4Zr-0,2Si) 1147 Ti-46Al-1FE-1Mo-1ZR-0,2Si (Ti-31,6Al-1,4Fe-2.5Mo-2,3Zr-0,2Si) 1146 Ti-47Al-1FE-1Mo-1ZR-0,2Si (Ti-32,5Al-1,4Fe-2.5Mo-2,3Zr-0,2Si)
  • Creep tests were also carried out at 750 ° C. 200 MPa on most alloys of the previous three series in order to test them in the most close to use in aerospace turbomachines.
  • the creep results of the first series reflect more strongly the strong influence of aluminum content and indirectly the microstructure on creep resistance than the effect of substitution of Mo to W (Table 4). Indeed, the comparison of the TiAl + 2W + 2Zr grades with different aluminum contents (1017 and 1029) reveals the high sensitivity of the creep resistance to aluminum. There is almost an order of magnitude between the secondary creep rates to the advantage of the aluminum rich shade. For low aluminum grades, the residual ⁇ phase is quite coarse. On the other hand, for the shades with high aluminum content, the ⁇ phase is smaller and is characterized by a dense precipitation in the lamellae. These precipitates act as obstacles to deformation and explain the unexpected improvement in creep.
  • the alloys used in aeronautical turbomachines must also have good resistance to oxidation.
  • the resistance to oxidation of alloys may, if necessary, be improved by introducing of a certain amount of niobium, an element known for his favorable action on this property.

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Abstract

Alliage du type TiA1 contenant en atomes 44 à 49 % d'aluminium, 0,5 à 3 % de zirconium, 0,5 à 2 % de fer, 0,5 à 2 % de molybdène, 0,2 à 0,5 % de silicium et 0 à 3 % de niobium. Utilisation dans les turbomachines aéronautiques.TiAl type alloy containing 44 to 49% aluminum, 0.5 to 3% zirconium, 0.5 to 2% iron, 0.5 to 2% molybdenum, 0.2 to 0.5% of silicon and 0 to 3% of niobium. Use in aeronautical turbomachines.

Description

L'invention concerne un alliage constitué d'aluminiure de titane dans lequel une fraction minoritaire des atomes d'aluminium et de titane est remplacée par d'autres atomes.The invention relates to an alloy consisting of aluminum aluminide titanium in which a minority fraction of the atoms of aluminum and titanium is replaced by other atoms.

Les alliages intermétalliques du type TiAl trouvent une utilisation avantageuse à haute température dans les turbomachines aéronautiques. TiAl se caractérise par sa faible masse volumique qui lui confère une résistance mécanique à chaud rapportée à la masse volumique supérieure à celle des alliages de titane classiques et même à celle de certains superalliages de nickel. Ceci est dû à une limite d'élasticité qui demeure constante typiquement entre 20 et 700 °C. Néanmoins, la faible ductilité de cet alliage est de nature à compromettre son utilisation pour les pièces tournantes. Des recherches sont donc actuellement menées dans le monde pour la mise au point de gammes de transformation qui ductilisent TiAl pour permettre l'introduction de ce matériau dans les turbomachines aéronautiques. Les travaux portent en parallèle sur le choix des nuances les plus adaptées à telle ou telle gamme de transformation.TiAl intermetallic alloys find a advantageous use at high temperature in turbomachines aeronautical. TiAl is characterized by its weak density which gives it a mechanical resistance to hot relative to the density higher than that of the conventional titanium alloys and even to that of some superalloys of nickel. This is due to a limit of elasticity which remains constant typically between 20 and 700 ° C. Nevertheless, the low ductility of this alloy is of a nature to compromise its use for rotating parts. So research is being done around the world for the development of transformation ranges that ductilize TiAl to allow the introduction of this material in aeronautical turbomachines. The work is parallel on the choice of shades most suited to such or such range of transformation.

Le but de la présente invention est de fournir un alliage du type TiAl présentant une grande ductilité à chaud, tout en conservant les propriétés mécaniques habituelles pour ces alliages.The object of the present invention is to provide an alloy of TiAl type having high ductility when hot, while retaining the usual mechanical properties for these alloys.

L'invention vise notamment un alliage du genre défini en introduction, et prévoit qu'il contient en atomes 44 à 49 % d'aluminium, 0,5 à 3 % de zirconium, 0,5 à 2 % de fer, 0,5 à 2 % de molybdène, 0,2 à 0,5 % de silicium et 0 à 3 % de niobium.The invention aims in particular at an alloy of the kind defined in introduction, and provides that it contains in atoms 44 to 49% of aluminum, 0.5 to 3% of zirconium, 0.5 to 2% of iron, 0.5 to 2% molybdenum, 0.2 to 0.5% silicon and 0 to 3% niobium.

Il a été proposé d'ajouter du fer (US-A-6 165 414 et US-A-6 174 495) pour améliorer la coulabilité des alliages TiAl, du zirconium (US-A-4 983 357, US-A-5 207 982 et US-A-5 997 808) pour améliorer le compromis résistance-ductilité, la ténacité, la tenue à l'oxydation et la résistance mécanique à chaud, du molybdène (US-A-5 350 466 et US-A-6 214 133) pour améliorer la tenue à chaud. Cependant, aucun de ces documents ne suggère une combinaison des éléments Fe, Zr et Mo.It has been proposed to add iron (US-A-6,165,414 and US-A-6 174,495) to improve the flowability of TiAl alloys, zirconium (US-A-4,983,357, US-A-5,207,982 and US-A-5 997 808) to improve the resistance-ductility compromise, toughness, resistance to oxidation and mechanical resistance when hot, molybdenum (US-A-5,350,466 and US-A-6,214,133) to improve the heat resistance. However, none of these documents suggests a combination of elements Fe, Zr and Mo.

Des caractéristiques optionnelles de l'alliage selon l'invention, complémentaires ou de substitution, sont énoncées ci-après:

  • Il contient en atomes 45 à 48 % d'aluminium, environ 1 % de zirconium, environ 1 % de fer, environ 1 % de molybdène et environ 0,2 % de silicium.
  • Il est composé exclusivement d'aluminium, de titane, de zirconium, de fer, de molybdène, de silicium et le cas échéant de niobium, sous réserve d'impuretés éventuelles.
Optional features of the alloy according to the invention, complementary or substitution, are set out below:
  • It contains in atoms 45 to 48% of aluminum, about 1% of zirconium, about 1% of iron, about 1% of molybdenum and about 0.2% of silicon.
  • It is composed exclusively of aluminum, titanium, zirconium, iron, molybdenum, silicon and optionally niobium, subject to possible impurities.

L'invention a également pour objet un procédé de traitement thermique d'un alliage tel que défini ci-dessus, dans lequel on met en solution ses éléments constitutifs par chauffage à une température comprise entre 1200 °C et 1350 °C, on refroidit à la température ambiante et on recuit à une température comprise entre 800 °C et 950 °C.The subject of the invention is also a method of treatment of an alloy as defined above, in which its constituent elements are put in solution by heating to a temperature of between 1200 ° C and 1350 ° C, cool to room temperature and annealing at a temperature between 800 ° C and 950 ° C.

Avantageusement, la mise en solution est effectuée à 1250 °C environ pendant 4 heures environ et le recuit à 900 °C environ pendant 4 heures environ.Advantageously, the dissolution is carried out at 1250 ° C. about 4 hours and annealing at 900 ° C. about 4 hours.

Les caractéristiques et avantages de l'invention sont exposés plus en détail dans la description ci-après, avec référence au dessin annexé, qui représente sous forme de graphique la variation de certaines propriétés de l'alliage selon l'invention en fonction de sa teneur en aluminium.The features and advantages of the invention are exposed in more detail in the description below, with reference in the appended drawing, which shows in graphic form the variation of certain properties of the alloy according to the invention depending on its aluminum content.

Dans la présente description, sauf indication contraire, toutes les proportions sont données en atomes. In this description, unless otherwise indicated, all proportions are given in atoms.

Il a été constaté que les nuances d'alliages du type TiAl (ou plus brièvement "alliages TiAl") à forte teneur en aluminium telle que 48 % sont plus ductiles et moins résistantes que les nuances à faible teneur en aluminium telle que 44 %. Toutefois, pour des teneurs supérieures à 48 % la tendance s'inverse rapidement avec une ductilité plus réduite alors que la tenue au fluage et la résistance à l'oxydation se trouvent améliorées. Ainsi, la teneur en aluminium doit être enfermée dans une fenêtre de composition très étroite (47-48 %) pour assurer un bon compromis de propriétés . Cependant, cette forte sensibilité de la teneur en aluminium des alliages TiAl constitue un handicap sérieux pour leur élaboration qui nécessite une très grande précision dans les quantités d'éléments ajoutés. Un lingot de plusieurs kilogrammes peut ainsi présenter des variations de teneurs en aluminium supérieures à 1% en différents endroits, avec comme conséquence des propriétés différentes, pouvant s'écarter des spécifications des utilisateurs. En outre, l'aluminium est volatil au cours de la fusion, provoquant une perte de concentration en aluminium qui est dépendante du nombre de fusions. C'est une raison supplémentaire pour laquelle il est difficile de respecter scrupuleusement les teneurs en aluminium nominales.It has been found that alloy grades of the TiAl type (or more briefly "TiAl alloys") with high aluminum content 48% are more ductile and less resistant than shades with low aluminum content such as 44%. However, for contents greater than 48% the trend reverses quickly with reduced ductility then creep resistance and oxidation resistance are find improved. Thus, the aluminum content must be locked in a window of very narrow composition (47-48 %) to ensure a good compromise of properties. However, this high sensitivity of the aluminum content of TiAl alloys is a serious handicap for their development which requires a very high degree of precision in quantities of added elements. An ingot of several kilograms can thus present variations in levels in aluminum greater than 1% in different places, with consequence of the different properties, which may differ from user specifications. In addition, aluminum is volatile during the merger, causing a loss of aluminum concentration which is dependent on the number of mergers. This is another reason why he is difficult to scrupulously respect the levels in nominal aluminum.

Le fer a pour effet d'agrandir la fenêtre de teneur en aluminium pour laquelle le bon compromis de propriétés est respecté. Autrement dit, les propriétés de ductilité et de résistance mécanique demeurent constantes sur un plus large intervalle de teneur en aluminium, rendant ainsi moins délicate la fabrication des alliages pour obtenir les propriétés voulues.Iron has the effect of enlarging the window of aluminum for which the good compromise of properties is respected. In other words, the properties of ductility and mechanical strength remain constant over a wider aluminum content range, thus making the delicate manufacturing of alloys to obtain the desired properties.

Les alliages TiAl contenant du fer se singularisent d'une autre manière. Alors que la quasi-totalité des alliages TiAl à l'état coulé ne se déforment plastiquement qu'à des températures supérieures à 800 °C, les nuances contenant du fer peuvent se déformer plastiquement à plus basse température. La température de transition fragile-ductile est en effet très brutale pour tous les alliages TiAl qui peuvent donc être classés en fonction de cette caractéristique. Un grand nombre d'additifs élémentaires se sont avérés inefficaces dans le passé pour améliorer la ductilité à des températures inférieures à 800 °C. Or, il a été constaté que l'addition conjointe de fer et de zirconium rend les alliages TiAl encore plus ductiles à 800 °C. L'avantage qui en est alors retiré est de pouvoir les fabriquer en recourant à des procédés de mise en forme traditionnels utilisant des températures compatibles avec les outils courants.TiAl alloys containing iron are distinguished by a another way. While almost all TiAl alloys in the poured state plastically deform only at temperatures above 800 ° C, the shades containing Iron can deform plastically at lower temperatures. The brittle-ductile transition temperature is indeed very brutal for all TiAl alloys which can therefore be classified according to this characteristic. A big number of elementary additives proved to be ineffective in the past to improve ductility at temperatures below 800 ° C. However, it has been found that the addition joint of iron and zirconium makes TiAl alloys even more ductile at 800 ° C. The advantage then removed is to be able to manufacture them by resorting to traditional shaping processes using temperatures compatible with common tools.

Le seul effet pénalisant du fer qui a été constaté est une diminution de la tenue au fluage, qui peut conduire à limiter l'addition de fer à des quantités faibles (autour de 1 %). L'utilisation du silicium dans la présente invention peut compenser cet effet en procurant un gain extrêmement rapide sur la tenue au fluage, ce qui permet de limiter sa concentration à 0,5 %. En effet des teneurs en silicium supérieures sont déconseillées car elles provoquent la précipitation de siliciures qui sont connus pour être préjudiciables pour la ductilité.The only penalizing effect of iron that has been found is a decrease in creep resistance, which may lead to the addition of iron to small amounts (around 1%). The use of silicon in the present invention can compensate for this effect by providing an extremely fast gain creep resistance, which limits its concentration at 0.5%. Indeed, higher silicon contents are discouraged because they cause the precipitation of silicides that are known to be detrimental to the ductility.

En ce qui concerne le zirconium, il a été constaté qu'une teneur élevée (5 %) avait pour effet de repousser la transition fragile-ductile vers les hautes températures et donc de contrecarrer l'effet bénéfique du fer. Par conséquent, la teneur en zirconium à utiliser doit être nettement inférieure à 5 %. Il est aussi préférable de limiter la teneur en zirconium pour des raisons de masse volumique. Enfin, les propriétés macroscopiques de TiAl peuvent être affectées en présence de zirconium en raison d'effets stériques qui prédominent sur les effets électroniques. Les travaux réalisés par les inventeurs ont permis de vérifier qu'il n'était pas souhaitable d'incorporer plus de 2 à 3 % de zirconium pour conserver un compromis acceptable résistance-ductilité.With regard to zirconium, it has been found that high level (5%) had the effect of delaying the transition fragile-ductile towards high temperatures and therefore counteract the beneficial effect of iron. Therefore, the zirconium content to be used must be significantly lower at 5 %. It is also preferable to limit the content of zirconium for density reasons. Finally, Macroscopic properties of TiAl can be affected by presence of zirconium due to steric effects which predominate over electronic effects. Works made by the inventors made it possible to verify that was not desirable to incorporate more than 2 to 3% of zirconium to maintain an acceptable compromise resistance-ductility.

Une addition réduite de molybdène (1 %) conjointement avec les éléments fer et zirconium permet d'obtenir un gain supplémentaire de ductilité à 800 °C, ce qui était le résultat recherché. Cependant, une teneur plus élevée n'est pas souhaitable car cet élément provoque une augmentation de la résistance mécanique à chaud, ce qui nécessite alors l'emploi d'une force plus élevée de la presse pour le déformer. Il faut aussi retenir que la tenue au fluage s'en trouve également améliorée par rapport aux alliages ne contenant pas cette addition de molybdène, effet qu'il sera possible de moduler par l'addition conjointe de Mo et de Si.Reduced addition of molybdenum (1%) together with the elements iron and zirconium makes it possible to obtain a gain additional ductility at 800 ° C, which was the desired result. However, a higher content is not undesirable because this element causes an increase in the mechanical strength when hot, which then requires the use of a higher force of the press for the deform. It must also be remembered that creep resistance is also found improved compared to alloys do not containing this addition of molybdenum, it will be possible to modulate by the joint addition of Mo and Si.

Les alliages selon l'invention répondent à l'état coulé aux exigences de grande ductilité à chaud permettant leur mise en forme par forgeage anisotherme.The alloys according to the invention correspond to the poured state high hot ductility requirements allowing their implementation form by anisothermic forging.

Les alliages décrits dans les exemples ci-après ont été fabriqués en utilisant la fusion à arc sous vide. Les lingotins ont ensuite subi un compactage isostatique à 1250 °C destiné à la fermeture des porosités et retassures. La caractérisation comparative des alliages a eu lieu après compactage et traitement thermique. Le traitement thermique comprend une mise en solution de 4 heures à 1250 °C suivie d'un refroidissement du four et d'un recuit de détensionnement de 4 heures à 900 °C. Ce traitement a pour but de générer deux types de structures suivant la concentration en aluminium. Il permet de stabiliser la structure lamellaire biphasée γ+α2 (TiAl+Ti3Al) pour les nuances les plus riches en titane et de stabiliser la structure duplex composée de grains lamellaires et de grains monolithiques de phase γ (TiAl) pour les nuances les plus riches en aluminium. Cette structure biphasée γ/α2 qui est bénéfique pour la ductilité ne peut toutefois pas être obtenue pour des concentrations en aluminium supérieures à 49 %, l'alliage demeurant alors monophasé γ même après traitement thermique. Ce traitement permet également une redistribution plus uniforme dans l'ensemble de la structure de certains éléments tels que le zirconium qui peuvent avoir tendance à ségréger dans les dernières zones liquides au cours de la solidification.The alloys described in the examples below were manufactured using vacuum arc melting. The ingots were then subjected to isostatic compaction at 1250 ° C for the closure of porosities and shrinkage. The comparative characterization of the alloys took place after compaction and heat treatment. The heat treatment comprises a solution of 4 hours at 1250 ° C followed by a cooling of the oven and a stress relieving annealing of 4 hours at 900 ° C. This treatment aims to generate two types of structures according to the aluminum concentration. It allows to stabilize the γ + α 2 two-phase lamellar structure (TiAl + Ti 3 Al) for the richest titanium grades and to stabilize the duplex structure composed of lamellar grains and γ-phase monolithic grains (TiAl) for the grades the richest in aluminum. This two-phase γ / α 2 structure which is beneficial for the ductility can not however be obtained for aluminum concentrations greater than 49%, the alloy then remaining single-phase γ even after heat treatment. This treatment also allows a more uniform redistribution throughout the structure of certain elements such as zirconium which may tend to segregate in the last liquid areas during solidification.

Les alliages selon l'invention comportent d'une part une addition de zirconium, et d'autre part des additions d'éléments W, Mo, Fe et Cr qui sont connus comme éléments β-gènes, en ce sens qu'ils stabilisent la formation de la phase β. La ductilité à chaud est déterminée par les propriétés de traction à 800 °C. Ces alliages devant conserver une ductilité à froid suffisante pour permettre l'usinage et la manutention des pièces, les propriétés de traction à 20 °C ont également été déterminées.The alloys according to the invention comprise on the one hand an addition of zirconium, and on the other hand additions of elements W, Mo, Fe and Cr which are known as β -generic elements, in that they stabilize the formation of the β phase. The hot ductility is determined by the tensile properties at 800 ° C. Since these alloys must retain sufficient cold ductility to allow the machining and handling of parts, tensile properties at 20 ° C have also been determined.

L'invention est illustrée ci-après par la description d'essais portant sur divers alliages, pour chacun desquels sont indiqués successivement un numéro d'identification, la composition en atomes et la composition en masse.The invention is illustrated below by the description tests on various alloys, for each of which are successively indicated an identification number, the atom composition and mass composition.

Une première série d'essais a pour but de tester l'association d'éléments durcissants (W, Mo) et d'un élément ductilisant (Zr). On prépare des alliages contenant soit 2 % W, soit 1 % W + 1 % Mo, avec pour chacune de ces combinaisons deux valeurs de Al + Mo, la teneur en aluminium étant choisie ainsi légèrement plus faible en présence de molybdène en raison du plus faible pouvoir β-gène du molybdène par rapport à celui du tungstène. 1029 Ti-45Al-2W-2Zr (Ti-28,9Al-8,7W-4,3Zr) 1017 Ti-48Al-2W-2Zr (Ti-30,4Al-8,8W-4,4Zr) 1027 Ti-44Al-1W-1Mo-2Zr (Ti-28,7Al-4,4W-4,4Zr-2,3Mo) 1028 Ti-47Al-1W-1Mo-2Zr (Ti-31,1Al-4,5W-4,5Zr-2,3Mo) A first series of tests is intended to test the combination of hardening elements (W, Mo) and a ductilizing element (Zr). Alloys containing either 2% W or 1% W + 1% Mo are prepared with, for each of these combinations, two values of Al + Mo, the aluminum content being thus chosen slightly lower in the presence of molybdenum because of the more low power β-gene molybdenum compared to that of tungsten. 1029 Ti-45Al-2W-2Zr (Ti-28,9Al-8,7W-4,3Zr) 1017 Ti-48Al-2W-2Zr (Ti-30,4Al-8,8W-4,4Zr) 1027 Ti-44Al-1W-1Mo-2Zr (Ti-28,7Al-4,4W-4,4Zr-2.3Mb) 1028 Ti-47Al-1W-1Mo-2Zr (Ti-31,1Al-4.5W-4,5Zr-2.3Mb)

Les résultats de traction à 20 et 800 °C révèlent que l'introduction des éléments durcissants est fortement pénalisante pour la ductilité puisque les allongements à 20 °C et à 800 °C ne dépassent pas 1,2 % et 2,9 % respectivement (tableau 1). Le molybdène apparaít en tout cas plus bénéfique que le tungstène pour cette propriété. Quant au durcissement évalué à partir de la limite d'élasticité, il est certes appréciable avec en particulier l'ajout de molybdène, mais ne justifie pas de sacrifier autant la ductilité. En résumé, la substitution de 1 Mo à 1 W apparaít favorable pour le compromis résistance-ductilité à 20 et 800 °C. Caractéristiques de traction des alliages Ti-45Al-2W-2Zr (1029), Ti-48Al-2W-2Zr (1017), Ti-44Al-1W-1Mo-2Zr (1027) et Ti-47Al-1W-1Mo-2Zr (1028) Alliage T (°C) σ0,2 (MPa) σmax (MPa) A (%) 1029 20 545 594 0,40 800 430 516 1,20 1017 20 431 509 0,76 800 390 458 0,98 1027 20 603 640 0,36 800 472 569 1,96 1028 20 500 626 1,21 800 462 588 2,88 The tensile results at 20 and 800 ° C reveal that the introduction of the hardening elements is highly disadvantageous for the ductility since the elongations at 20 ° C. and 800 ° C. do not exceed 1.2% and 2.9% respectively ( Table 1). In any case, molybdenum appears to be more beneficial than tungsten for this property. As for the hardening evaluated from the yield strength, it is certainly appreciable with in particular the addition of molybdenum, but does not justify sacrificing ductility as much. In summary, the substitution of 1 Mo to 1 W appears favorable for the resistance-ductility compromise at 20 and 800 ° C. Traction characteristics of the Ti-45Al-2W-2Zr (1029), Ti-48Al-2W-2Zr (1017), Ti-44Al-1W-1Mo-2Zr (1027) and Ti-47Al-1W-1Mo-2Zr alloys ( 1028) Alloy T (° C) σ 0.2 (MPa) σ max (MPa) AT (%) 1029 20 545 594 0.40 800 430 516 1.20 1017 20 431 509 0.76 800 390 458 0.98 1027 20 603 640 0.36 800 472 569 1.96 1028 20 500 626 1.21 800 462 588 2.88

La deuxième série de nuances se caractérise par les compositions suivantes: 1031 Ti-45Al-2W-2Cr-1Zr (Ti-29,1Al-8,8W-2,5Cr-2,2Zr) 1032 Ti-47Al-2W-2Cr-1Zr (Ti-30,7Al-8,9W-2,5Cr-2,2Zr) 1033 Ti-46Al-1Fe-1W-1Zr (Ti-30,5Al-1,4Fe-4,6W-2,3Zr) 1034 Ti-48Al-1Fe-1W-1Zr (Ti-32,6Al-1,4Fe-4,6W-2,3Zr) The second series of shades is characterized by the following compositions: 1031 Ti-45Al-2W-2Cr-1ZR (Ti-29,1Al-8,8W-2,5Cr-2,2Zr) 1032 Ti-47Al-2W-2Cr-1ZR (Ti-30,7Al-8,9W-2,5Cr-2,2Zr) 1033 Ti-46Al-1FE-1W-1ZR (Ti-30,5Al-1,4Fe-4,6W-2,3Zr) 1034 Ti-48Al-1FE-1W-1ZR (Ti-32,6Al-1,4Fe-4,6W-2,3Zr)

Cette série a pour but de tester l'association d'un seul élément durcissant (W) et de plusieurs éléments ductilisants (Cr, Fe, Zr), ce qui a conduit à réduire à 1 % la teneur en zirconium (tableau 2). Les résultats de ductilité révèlent que les allongements ne dépassent pas 1 % à 20 °C. Le tungstène apparaít clairement comme responsable de cette fragilité à basse température, ce qui confirme les résultats de la première série. D'autre part, une réduction à 1 % de la teneur en élément durcissant (W) se traduit conformément par un adoucissement. Il est à remarquer que les deux nuances contenant du fer se caractérisent par la même ductilité à 20 °C en dépit de la différence de teneur en aluminium, un comportement qui tranche par rapport aux autres couples de nuances. Un autre point intéressant concerne les allongements à 800 °C qui atteignent près de 28 % pour l'alliage Ti-48Al-1W-1Fe-1Zr, mettant manifestement en évidence l'effet bénéfique du fer sur la ductilité à chaud. Caractéristiques de traction des alliages Ti-45Al-2W-2Cr-1Zr (1031), Ti-47Al-2W-2Cr-1Zr (1032), Ti-46Al-1W-1Fe-1Zr (1033) et Ti-48Al-1W-1Fe-1Zr (1034) Alliage T (°C) σ0,2 (MPa) σmax (MPa) A (%) 1031 20 522 570 0,41 800 418 511 3,62 1032 20 498 532 0,35 800 422 520 1,72 1033 20 474 574 0,87 800 390 456 3,80 1034 20 357 431 0,84 800 338 440 27,52 The aim of this series is to test the combination of a single hardening element (W) and several ductilizing elements (Cr, Fe, Zr), which led to a reduction of 1% in the zirconium content (Table 2). The ductility results reveal that the elongations do not exceed 1% at 20 ° C. Tungsten clearly appears to be responsible for this fragility at low temperature, which confirms the results of the first series. On the other hand, a 1% reduction in the hardening element content (W) is reflected in a softening manner. It should be noted that the two grades containing iron are characterized by the same ductility at 20 ° C despite the difference in aluminum content, a behavior that contrasts with other pairs of grades. Another interesting point concerns the elongations at 800 ° C which reach nearly 28% for the alloy Ti-48Al-1W-1Fe-1Zr, clearly demonstrating the beneficial effect of iron on hot ductility. Tensile properties of Ti-45Al-2W-2Cr-1Zr (1031), Ti-47Al-2W-2Cr-1Zr (1032), Ti-46Al-1W-1Fe-1Zr (1033) and Ti-48Al-1W- alloys 1Fe-1Zr (1034) Alloy T (° C) σ 0.2 (MPa) σ max (MPa) AT (%) 1031 20 522 570 0.41 800 418 511 3.62 1032 20 498 532 0.35 800 422 520 1.72 1033 20 474 574 0.87 800 390 456 3.80 1034 20 357 431 0.84 800 338 440 27.52

La figure unique représente, pour les alliages des deux séries précédentes, la limite d'élasticité et l'allongement à rupture à 20 °C en fonction de la teneur en aluminium. Les points correspondant à chaque propriété sont situés approximativement sur une droite. Il se dégage ainsi clairement une relation inverse entre la ductilité et la limite d'élasticité. L'augmentation de la ductilité et la diminution de la limite d'élasticité telles qu'elles sont observées sur les compositions plus riches en aluminium sont liées à deux changements microstructuraux. La nuance plus riche en aluminium possède tout d'abord une fraction volumique de phase γ monolithique plus élevée (et corrélativement une fraction lamellaire plus basse); or, il est connu que les structures duplex sont plus ductiles et moins résistantes que les structures entièrement lamellaires. De plus, cette nuance est moins riche en phase β. La nuance Ti-48Al-1Fe-1W-1Zr est majoritairement composée de phase γ monolithique et la fraction volumique trop faible de lamelles ne permet plus de fractionner la taille de grains, ce qui explique le niveau de ductilité légèrement plus réduit à température ambiante que pour d'autres additions. En contrepartie, l'incorporation de fer produit un effet particulier puisqu'elle permet d'atteindre un certain niveau de ductilité pour le traitement thermique standard, en l'occurrence 0,8 % pour l'alliage Ti-46Al-1Fe-1W-1Zr, ce qui n'est pas le cas pour les autres nuances riches en titane. À l'état standard, la nuance Ti-46Al-1Fe-1W-1Zr se caractérise par la présence d'une quantité élevée de phase β alors que la nuance Ti-48Al-1Fe-1W-1Zr présente une majorité de phase γ monolithique et une minorité de phase β.The single figure represents, for the alloys of the two previous series, the elastic limit and elongation at break at 20 ° C as a function of the aluminum content. The points corresponding to each property are located approximately on a straight line. Clearly, there is an inverse relationship between ductility and the yield strength. The increase in ductility and the decrease in the yield strength as observed on the richer aluminum compositions are related to two microstructural changes. The richer aluminum grade firstly has a higher monolithic γ volume fraction (and correspondingly a lower lamellar fraction); however, it is known that duplex structures are more ductile and less resistant than fully lamellar structures. In addition, this shade is less rich in β phase. The Ti-48Al-1Fe-1W-1Zr grade is predominantly composed of monolithic γ-phase and the low volume fraction of lamellae no longer makes it possible to fractionate the grain size, which explains the level of ductility slightly reduced at ambient temperature than for other additions. In return, the incorporation of iron produces a particular effect since it makes it possible to reach a certain level of ductility for the standard heat treatment, in this case 0.8% for the alloy Ti-46Al-1Fe-1W- 1Zr, which is not the case for other shades rich in titanium. In the standard state, the Ti-46Al-1Fe-1W-1Zr grade is characterized by the presence of a high amount of β- phase while the Ti-48Al-1Fe-1W-1Zr grade has a majority of monolithic γ-phase. and a phase minority β .

La troisième série de nuances se caractérise par des ajouts de fer, de zirconium et de molybdène. Deux nuances correspondent à une substitution de Mo à W par rapport aux nuances préférées ci-dessus. Les deux autres nuances se caractérisent par l'absence de molybdène: 1144 Ti-46Al-1Fe-1Zr-0,2Si (Ti-32A1-1,4Fe-2,4Zr-0,2Si) 1145 Ti-47Al-1Fe-1Zr-0,2Si (Ti-32,9Al-1,4Fe-2,4Zr-0,2Si) 1147 Ti-46Al-1Fe-1Mo-1Zr-0,2Si (Ti-31,6Al-1,4Fe-2,5Mo-2,3Zr-0,2Si) 1146 Ti-47Al-1Fe-1Mo-1Zr-0,2Si (Ti-32,5Al-1,4Fe-2,5Mo-2,3Zr-0,2Si) The third series of shades is characterized by additions of iron, zirconium and molybdenum. Two shades correspond to a substitution of Mo to W with respect to the preferred shades above. The other two grades are characterized by the absence of molybdenum: 1144 Ti-46Al-1FE-1ZR-0,2Si (Ti-32A1-1,4Fe-2,4Zr-0,2Si) 1145 Ti-47Al-1FE-1ZR-0,2Si (Ti-32,9Al-1,4Fe-2,4Zr-0,2Si) 1147 Ti-46Al-1FE-1Mo-1ZR-0,2Si (Ti-31,6Al-1,4Fe-2.5Mo-2,3Zr-0,2Si) 1146 Ti-47Al-1FE-1Mo-1ZR-0,2Si (Ti-32,5Al-1,4Fe-2.5Mo-2,3Zr-0,2Si)

L'ajout de silicium est effectué pour contrebalancer l'éventuelle faiblesse apportée par le fer vis-à-vis de la tenue au fluage. La comparaison des résultats avec les précédentes séries révèle que la substitution individuelle du fer ou du molybdène au tungstène diminue la fragilité des alliages. Le niveau de ductilité à froid est tout à fait satisfaisant avec des allongements compris entre 1 et 2 % (tableau 3). Les résultats antérieurs sont confirmés en ce sens qu'en présence de fer, la ductilité est relativement peu sensible à la teneur en Al. L'effet bénéfique du molybdène sur la ductilité à chaud est également confirmé, alors que cet effet était bien moins visible sur les alliages de la première série en présence de tungstène. Il apparaít donc un effet de synergie entre les éléments fer et molybdène quant à leur action sur la ductilité à chaud. Ainsi, la comparaison des quatre dernières nuances révèle que l'ajout de molybdène permet d'augmenter les allongements à 800 °C de 27 % en moyenne à 73 % en moyenne. Un tel niveau de ductilité à 800 °C permet d'escompter une bonne déformabilité au cours du forgeage ultérieur, d'autant que celui-ci est réalisé en débutant à une température plus élevée, typiquement 1000 °C. Un examen du faciès de rupture des éprouvettes s'allongeant de 73 % en moyenne révèle que la structure est composée de nombreux petits grains lamellaires, sans recristallisation dynamique sous forme de grains monolithiques, ce qui laisse prévoir un bon comportement en fluage. Caractéristiques de traction des alliages Ti-46Al-1Fe-1Zr-0,2Si (1144), Ti-47Al-1Fe-1Zr-0,2Si (1145), Ti-46Al-1Fe-1Mo-1Zr-0,2Si (1147) et Ti-47A1-1Fe-1Mo-1Zr-0,2Si (1146) Alliage T (°C) σ0,2 (MPa) σmax (MPa) A (%) 1144 20 442 539 1,26 800 396 480 21,0 1145 20 391 486 1,14 800 357 445 33,0 1147 20 438 565 1,23 800 380 451 60,0 1146 20 371 506 1,40 800 354 438 76,0 The addition of silicon is done to counterbalance the possible weakness provided by the iron vis-à-vis the creep resistance. The comparison of the results with the previous series reveals that the individual substitution of iron or molybdenum for tungsten reduces the brittleness of the alloys. The level of cold ductility is quite satisfactory with elongations of between 1 and 2% (Table 3). Previous results are confirmed in the sense that in the presence of iron, the ductility is relatively insensitive to the Al content. The beneficial effect of molybdenum on hot ductility is also confirmed, whereas this effect was much less visible. on the alloys of the first series in the presence of tungsten. There is therefore a synergistic effect between the iron and molybdenum elements as to their action on hot ductility. Thus, the comparison of the last four shades reveals that the addition of molybdenum makes it possible to increase the elongations to 800 ° C from 27% on average to 73% on average. Such a level of ductility at 800 ° C makes it possible to expect good deformability during the subsequent forging, especially since this is done by starting at a higher temperature, typically 1000 ° C. An examination of the fracture facies of 73% average lengthening specimens reveals that the structure is composed of numerous small lamellar grains, without dynamic recrystallization in the form of monolithic grains, which suggests a good creep behavior. Tensile Characteristics of Ti-46Al-1Fe-1Zr-0.2Si (1144), Ti-47Al-1Fe-1Zr-0.2Si (1145), Ti-46Al-1Fe-1Mo-1Zr-0.2Si (1147) Alloys ) and Ti-47A1-1Fe-1Mo-1Zr-0.2Si (1146) Alloy T (° C) σ 0.2 (MPa) σ max (MPa) AT (%) 1144 20 442 539 1.26 800 396 480 21.0 1145 20 391 486 1.14 800 357 445 33.0 1147 20 438 565 1.23 800 380 451 60.0 1146 20 371 506 1.40 800 354 438 76.0

Des essais de fluage ont également été réalisés à 750 °C sous 200 MPa sur la plupart des alliages des trois séries précédentes afin de les tester dans les conditions les plus proches de l'utilisation dans des turbomachines aéronautiques.Creep tests were also carried out at 750 ° C. 200 MPa on most alloys of the previous three series in order to test them in the most close to use in aerospace turbomachines.

Les résultats de fluage de la première série reflètent de façon plus marquée la forte influence de la teneur en aluminium et indirectement de la microstructure sur la tenue au fluage que l'effet de la substitution de Mo à W (tableau 4). En effet, la comparaison des nuances TiAl+2W+2Zr ayant des teneurs en aluminium différentes (1017 et 1029) révèle la forte sensibilité de la tenue au fluage vis-à-vis de l'aluminium. Il existe presque un ordre de grandeur entre les vitesses de fluage secondaires à l'avantage de la nuance riche en aluminium. Pour les nuances à faible teneur en aluminium, la phase β résiduelle est assez grossière. En revanche, pour les nuances à forte teneur en aluminium, la phase β est plus réduite et se caractérise par une précipitation dense dans les lamelles. Ces précipités agissent comme des obstacles à la déformation et permettent d'expliquer l'amélioration inattendue en fluage. Pour la différence de propriétés observée entre 1017 et 1028, il est difficile alors d'incriminer la présence non bénéfique du molybdène car la teneur en aluminium est légèrement inférieure pour la nuance contenant du molybdène. D'une façon générale, les propriétés de fluage obtenues sur ces quatre nuances sont excellentes par rapport aux alliages connus à base de TiAl. Caractéristiques de fluage des alliages Ti-45Al-2W-2Zr (1029), Ti-48Al-2W-2Zr (1017), Ti-44Al-1W-1Mo-2Zr (1027) et Ti-47Al-1W-1Mo-2Zr (1028) Alliage Durée (h) Primaire Secondaire ε ˙ (s-1) A = 0,2 % A = 0,5 % A (%) Durée (h) 1029 33 153 0,13 12 5,0.10-9 1017 392 1160 - - 0,9. 10-9 1027 18 129 0,32 46 3,7.10-9 1028 85 574 0,15 52 0,67.10-9 The creep results of the first series reflect more strongly the strong influence of aluminum content and indirectly the microstructure on creep resistance than the effect of substitution of Mo to W (Table 4). Indeed, the comparison of the TiAl + 2W + 2Zr grades with different aluminum contents (1017 and 1029) reveals the high sensitivity of the creep resistance to aluminum. There is almost an order of magnitude between the secondary creep rates to the advantage of the aluminum rich shade. For low aluminum grades, the residual β phase is quite coarse. On the other hand, for the shades with high aluminum content, the β phase is smaller and is characterized by a dense precipitation in the lamellae. These precipitates act as obstacles to deformation and explain the unexpected improvement in creep. For the difference in properties observed between 1017 and 1028, it is difficult then to incriminate the non-beneficial presence of molybdenum because the aluminum content is slightly lower for the molybdenum-containing grade. In general, the creep properties obtained on these four grades are excellent compared to known alloys based on TiAl. Creep characteristics of the alloys Ti-45Al-2W-2Zr (1029), Ti-48Al-2W-2Zr (1017), Ti-44Al-1W-1Mo-2Zr (1027) and Ti-47Al-1W-1Mo-2Zr ( 1028) Alloy Duration (h) Primary Secondary ε ˙ (s -1 ) A = 0.2% A = 0.5% AT (%) Duration (h) 1029 33 153 0.13 12 5.0.10 -9 1017 392 1160 - - 0.9. 10 -9 1027 18 129 0.32 46 3.7.10 -9 1028 85 574 0.15 52 0.67.10 -9

Les résultats de fluage obtenus sur trois des nuances des deuxième et troisième séries révèlent l'effet néfaste pour la résistance au fluage des éléments ductilisants chrome et fer (tableau 5). Toutefois, l'ajout de 0,2 % de silicium pour une nuance de la troisième série permet de diminuer nettement la vitesse de fluage secondaire, pour atteindre un niveau comparable à celui de la première série. Caractéristiques de fluage des alliages Ti-45Al-2W-2Cr-1Zr (1031), Ti-46Al-1W-1Fe-1Zr (1033) et Ti-46Al-1Fe-1Zr-0,2Si (1144) Alliage Durée (h) Primaire Secondaire ε ˙ (s-1) A = 0,2 % A = 0,5 % A (%) Durée (h) 1031 17 77 0,22 22 11.10-9 1033 2,5 32 0,38 20 26.10-9 1144 30 250 0,50 250 2,5.10-9 The creep results obtained on three of the grades of the second and third series reveal the detrimental effect on the creep resistance of the chromium and iron ductilizing elements (Table 5). However, the addition of 0.2% silicon for a grade of the third series makes it possible to significantly reduce the secondary creep rate to reach a level comparable to that of the first series. Creep Characteristics of Ti-45Al-2W-2Cr-1Zr (1031), Ti-46Al-1W-1Fe-1Zr (1033) and Ti-46Al-1Fe-1Zr-0.2Si (1144) Alloys Alloy Duration (h) Primary Secondary ε ˙ (s -1 ) A = 0.2% A = 0.5% AT (%) Duration (h) 1031 17 77 0.22 22 11.10 -9 1033 2.5 32 0.38 20 26.10 -9 1144 30 250 0.50 250 2.5.10 -9

Indépendamment de la présente invention, les alliages utilisés dans les turbomachines aéronautiques doivent également avoir une bonne résistance à l'oxydation. Dans cette optique, la résistance à l'oxydation des alliages préférés peut, si nécessaire, être améliorée par l'introduction d'une certaine quantité de niobium, élément connu pour son action favorable sur cette propriété.Independently of the present invention, the alloys used in aeronautical turbomachines must also have good resistance to oxidation. In this optics, the resistance to oxidation of alloys may, if necessary, be improved by introducing of a certain amount of niobium, an element known for his favorable action on this property.

Claims (7)

Alliage constitué d'aluminiure de titane dans lequel une fraction minoritaire des atomes d'aluminium et de titane est remplacée par d'autres atomes, caractérisé en ce qu'il contient en atomes 44 à 49 % d'aluminium, 0,5 à 3 % de zirconium, 0,5 à 2 % de fer, 0,5 à 2 % de molybdène, 0,2 à 0,5 % de silicium et 0 à 3 % de niobium.An alloy consisting of titanium aluminide in which a minority fraction of the aluminum and titanium atoms is replaced by other atoms, characterized in that it contains 44 to 49% of aluminum, 0.5 to 3 % zirconium, 0.5 to 2% iron, 0.5 to 2% molybdenum, 0.2 to 0.5% silicon and 0 to 3% niobium. Alliage selon la revendication 1, qui contient en atomes 45 à 48 % d'aluminium, environ 1 % de zirconium, environ 1 % de fer, environ 1 % de molybdène et environ 0,2 % de silicium.An alloy according to claim 1 which contains in atoms 45 to 48% aluminum, about 1% zirconium, about 1% iron, about 1% molybdenum and about 0.2% of silicon. Alliage selon la revendication 2, qui contient en atomes environ 46 % d'aluminium.An alloy according to claim 2 which contains in about 46% aluminum atoms. Alliage selon la revendication 2, qui contient en atomes environ 47 % d'aluminium.An alloy according to claim 2 which contains in about 47% of aluminum atoms. Alliage selon l'une des revendications précédentes, qui est composé exclusivement d'aluminium, de titane, de zirconium, de fer, de molybdène, de silicium et le cas échéant de niobium, sous réserve d'impuretés éventuelles.Alloy according to one of the preceding claims, which is composed exclusively of aluminum, titanium, zirconium, iron, molybdenum, silicon and, where appropriate, niobium, subject to possible impurities. Procédé de traitement thermique d'un alliage selon l'une des revendications précédentes, dans lequel on met en solution ses éléments constitutifs par chauffage à une température comprise entre 1200 °C et 1350 °C, on refroidit à la température ambiante et on recuit à une température comprise entre 800 °C et 950 °C.Heat treatment process of an alloy according to one of the preceding claims, in which solution its constituent elements by heating to a temperature between 1200 ° C and 1350 ° C, it is cooled at room temperature and annealing at a temperature between 800 ° C and 950 ° C. Procédé selon la revendication 4, dans lequel la mise en solution est effectuée à 1250 °C environ pendant 4 heures environ et le recuit à 900 °C environ pendant 4 heures environ.The method of claim 4, wherein the setting in solution is carried out at about 1250 ° C for 4 hours about and annealing at about 900 ° C for 4 hours about.
EP05290750A 2004-04-07 2005-04-05 Titanium-aluminium alloy having high-temperature ductility Expired - Lifetime EP1584697B1 (en)

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FR0403658A FR2868791B1 (en) 2004-04-07 2004-04-07 DUCTILE HOT TITANIUM ALUMINUM ALLOY
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DE602005025273D1 (en) 2011-01-27
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FR2868791A1 (en) 2005-10-14
EP1584697B1 (en) 2010-12-15
ATE491819T1 (en) 2011-01-15

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