Classifications

• • 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

Definitions

• the invention relates to a novel composition of titanium alloy with high mechanical characteristics for the manufacture of high performance parts especially for the aeronautical industry, such as landing gear elements or turbine disks.
• titanium alloys with high mechanical characteristics comprising a significant proportion of aluminum, such as, for example, Ti 6-4 (6% aluminum and 4% vanadium).
• Ti 8-1-1 (8% aluminum, 1% molybdenum and 1% vanadium) and also Ti 10-2-3 (1% vanadium, 2% iron and 3% aluminum) , the percentages representing a portion of the total mass.
• Titanium alloys of the quasi-beta type containing a large proportion of aluminum as well as oxygen are also known.
• An example of such an alloy is given by the document EP1302555 which describes a titanium alloy having the following composition, expressed as a percentage of the total mass:
• Such alloys are intended to be hot-forged, at a temperature close to the ⁇ ⁇ ⁇ + ⁇ polymorphic transition temperature, and then subjected to a heat treatment during which the part is heated to a temperature close to the polymorphic transition temperature.
• ⁇ ⁇ ⁇ + ⁇ to reveal a beta phase coexisting with an alpha phase, followed by stage cooling and aging of the part.
• the purpose of such a treatment is to obtain a significant proportion of beta phase in the finished part, in order to give it a high mechanical strength.
• elements such as vanadium, molybdenum, chromium or iron contribute to stabilize the beta phase during cooling of the part, which makes it possible to freeze a large part of the alloy in this phase.
• the promotion of the beta phase is usually detrimental to the alpha phase, (typically representing 60 to 70% of the mass of a piece made of this alloy) which promotes the toughness of the piece.
• the alpha phase typically representing 60 to 70% of the mass of a piece made of this alloy
• zirconium has been added to the composition to promote the stabilization of the alpha phase during cooling, forming solid solutions with alpha titanium which is relatively close in density and melting temperature.
• the aim of the invention is to propose a novel titanium alloy composition which can potentially be to obtain better mechanical characteristics.
• a titanium alloy is proposed that is particularly suitable for hot forging at a temperature close to the ⁇ ⁇ ⁇ + ⁇ polymorphic transition temperature and the heat treatment with heating at a temperature close to the said temperature.
• the alloy with at least 4% by weight of aluminum, at least 0.1% by weight of oxygen and at least 0.01% by weight of carbon, the alloy comprising in addition to at least one element selected from vanadium, molybdenum, chromium or iron.
• the titanium alloy also comprises hafnium in a mass proportion of at least 0.1%.
• the inventors assume that an increase in the proportion of aluminum and / or oxygen relative to the known compositions leads to an increase in the polymorphic transition temperature ⁇ ⁇ ⁇ + ⁇ , which would allow forging at a higher temperature, which would therefore contribute to reinforcing the mechanical strength characteristics of the final piece.
• aluminum and oxygen seem to be the cause of precipitation of oxidizing phases which have a negative effect on the final mechanical performance of the part.
• the inventors propose to accompany this increase with a significant contribution of hafnium, which has a particularly strong affinity with oxygen and which seems facilitate the precipitation of the phases of the alloy by binding to oxygen, thus avoiding the formation of oxidizing phases of aluminum and titanium, so that the negative effect related to the increase of the proportions of aluminum and oxygen is otherwise removed, at least significantly attenuated.
• hafnium has several advantages. In addition to the aforementioned affinity with oxygen, hafnium has an electronic structure comparable to that of zirconium. The inventors thus assume that it could, in the same way as zirconium, promote the stabilization of the alpha phase of titanium by forming solid solutions therewith. In addition, hafnium has continuous solubility in the beta phase, and complete miscibility in the alpha phase of titanium. Finally, it is present in trace amounts in some titanium ores. Measurements on various ores show that the proportion of hafnium in ores does not exceed 0.05%. It therefore seems advantageous not to seek to eliminate this component of the ore, but on the contrary to enrich this ore in hafnium to obtain the proportion recommended according to the invention.
• such an alloy is subjected after forging to the following heat treatment:
• Cooling preferably in air
• compositions As an exemplary embodiment, three typical compositions are given here, and in each of them, a example is specified. The proportions indicated are mass proportions.
• alloy No. 2 in accordance with Composition No. 2, is also selected:
• zirconium is thus added, which, in addition to its propensity to stabilize the alpha phase of titanium, also seems to have an affinity with the oxygen of interest, so that zirconium acts in concert with hafnium to capture oxygen and thus avoiding the precipitation of oxidizing phases of aluminum and titanium.
• the simultaneous presence of these two elements also seems to have a synergistic effect, further decreasing the segregation of the constituent species of the alloy during cooling of the alloy.
• Silicon seems, although it is not in the same column of the Mendeliev table as zirconium or hafnium, also to have a beneficial effect in counteracting the precipitation of oxidizing phases of aluminum and titanium;
• the proportions are given to within ⁇ 10% in relative value.
• the proportion of aluminum will be between 6.3% and 7.7%, and the proportion of hafnium will be between 0.81% and .99%.
• compositions and alloys described in detail comprise vanadium, molybdenum, chromium and iron, the invention also covers alloys using only some or even one of them in the proportions indicated. , or in other proportions. Moreover, the proportion of oxygen may be increased beyond 0.3%.
• the titanium compositions and alloys according to the invention may not contain zirconium, silicon or carbon (except traces). These alloys or compositions may comprise other elements than those quoted here, in proportions that do not call into question the possibility of forging at temperatures close to the polymorphic transition ⁇ ⁇ ⁇ + ⁇ nor the possibility of heat treatment with heating at a temperature close to the temperature of transition to show in the semi-finished product a phase ⁇ cohabitant with an ⁇ phase.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Forging (AREA)
• Treatment Of Steel In Its Molten State (AREA)
• Manufacture And Refinement Of Metals (AREA)
• Heat Treatment Of Steel (AREA)
• Turbine Rotor Nozzle Sealing (AREA)
• Shaping Metal By Deep-Drawing, Or The Like (AREA)

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• 2009
  • 2009-06-08 FR FR0902754A patent/FR2946363B1/fr active Active
• 2010
  • 2010-06-08 US US13/376,882 patent/US9399806B2/en active Active
  • 2010-06-08 JP JP2012514455A patent/JP2012529568A/ja active Pending
  • 2010-06-08 EA EA201101687A patent/EA020469B1/ru not_active IP Right Cessation
  • 2010-06-08 CA CA2764226A patent/CA2764226C/fr active Active
  • 2010-06-08 WO PCT/EP2010/058038 patent/WO2010142701A1/fr not_active Ceased
  • 2010-06-08 EP EP10724829.6A patent/EP2440679B1/fr active Active
  • 2010-06-08 CN CN201080026174.5A patent/CN102482735B/zh active Active
  • 2010-06-08 BR BRPI1010616A patent/BRPI1010616A2/pt not_active IP Right Cessation
• 2015
  • 2015-02-02 JP JP2015018608A patent/JP2015155574A/ja active Pending

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