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
  • C22F1/183—High-melting or refractory metals or alloys based thereon of titanium or alloys based thereon

Definitions

• the invention relates to a method for manufacturing a titanium alloy part with high characteristics, intended for example for compressor disks for aircraft propulsion systems, as well as the parts obtained.
• the document FR 2 144 205 (GB 1356734) describes a titanium alloy of composition by weight: Al 3 to 7 - Sn 1 to 3 - Zr 1 to 4 - Mo 2 to 6 - Cr 2 to 6 and up to approximately 0 , 2% of 0, 6% of V, 0.5% of Si, complement Ti and impurities. With preferably: Al 4.5 to 5.5 - Sn 1.5 to 2.5 - Zr 1.5 to 2.5 - Mo 3.5 to 4.5 - Cr 3.5 to 4.5 - and up to about 0.12% O.
• the Applicant has tried to obtain parts of the same type of alloy having a regular structure and without segregation, and having high mechanical characteristics at 20 ° C (Rm - R p0,2 - K 1C ) with sufficient elongation as well as '' a much improved creep resistance at 400 ° C.
• the above problem is solved by means of new composition limits and a new transformation process, these composition limits and the conditions of hot working and heat treatment then being inseparable.
• the alphagenic elements Al and Sn give respectively, in combination with the other addition elements, insufficient hardnesses when they are in lower contents than the minimum values chosen, and random or frequent precipitations when they are in higher contents than the maximum values set; they preferably have contents of between 4.5 and 5.4% for Al, and between 1.8 and 2.5% for Sn.
• the Zr content is preferably between 3.5 and 4.8% and more preferably between 4.1 and 4.8%.
• the three elements Al, Sn and Zr do not together cause fragility, and we can notice that the sum: % Al +% Sn / 3 +% Zr / 6, taken as a reference in FR 2 144 205 with respect to the tendency of the Ti3Al compound to form, is equal to 7 for their maximum contents.
• Mo slightly hardening, has a significant effect of lowering the temperature of transformation of the alpha-beta structure into a fully beta structure, hereinafter called "transus beta".
• Mo is preferably between 2.0 and 4.5%.
• V has substantially the same role as Mo and is hardening beta by precipitation like Cr, it is optionally added, (Cr + V) being maintained between 1.5 and 4.5%.
• Fe causes hardening by precipitation of intermetallic compounds, it is known to lower the resistance to hot creep at high temperature (about 550 to 600 ° C) because of these precipitates which thus cause a certain brittleness.
• the Fe content is maintained in all cases below 2%, and is preferably adjusted between 0.7 and 1.5% because it then surprisingly results in a very improved creep resistance at 400 ° C. , which is interesting for example for the parts used in the "medium temperature" stages (typically 350 to less than 500 ° C.) of aeronautical compressors.
• the "S / s" wrought ratio (initial section / final section) of this final wrought is preferably greater than or equal to 2.
• this solution treatment is usually carried out at a temperature chosen between (“transus beta” - 40 ° C) and ("transus beta” - 10 ° C) with maintenance at a temperature of chosen duration usually between 20 min and 2 h and most often between 30 min and 1 h 30 min and this dissolution is followed by ambient cooling with water or more usually with air.
• An income is then made at a temperature chosen between 550 and 650 ° C, so as to improve the elongation at break A% and the creep resistance at 400 ° C while retaining sufficient mechanical strength and toughness (R m - R p0.2 and K 1C ).
• the advantages of the process of the invention are as follows: - reproducibly obtaining a fine needle structure, without segregation of any kind; - elimination of the risks of fragility; - simultaneous obtaining of all the desired characteristics: structure and previous mechanical characteristics.
• Each ingot has undergone a first roughing in beta at 1050 ° C / 1100 ° C of the initial diameter ⁇ 200 mm squared 80 mm. Then, for a portion of each, a second rough refinement of the structure in alpha-beta by flat forging of 70 ⁇ 30 nm, at temperature (preheating temperature) equal to 50 ° C. less than the temperature of the transus estimated for each of the six alloys (Table 2). This estimate was made by an internal approach rule taking into account the contents of addition elements.
• 2nd range (Table 4): we took portions of the 80 mm squares, except the square H, from the first roughing in beta, and we applied a second roughing in alpha-beta to the square 65 mm, at a temperature adjusted to 50 ° C less than the actual "transus beta" determined previously (Table 2). Then a final forging of a 70x30 mm plate was made on this square, starting from a preheated state for 30 min at ("transus beta" + 10 ° C) and ending in alpha-beta, fine needle structures alpha-beta being obtained. The parts were then subjected to a solution for 1 h at real "transus beta" - 30 ° C.
• the samples of the 1st range have a final forging at a lower temperature than the samples of the 2nd range, and in addition this forging was carried out at a temperature offset in a variable manner compared to the real "transus beta" of the alloy. : for example 110 ° C less than this transus for A1, and 40 ° C less for E1.
• - K is a control centered in the analysis recommended by FR 2 144 205
• H is another control without Sn and without Zr, which in this first series gives insufficient mechanical resistance and creep resistance.
• the comparison of the results of the 1st and 2nd ranges shows the importance of a final forging beginning in beta.
• New ingots have been developed, with Al contents close to 5% and higher Zr contents than in the first series of tests.
• the compositions of the five ingots chosen in this example are given in Table 7. Only one ingot marked FB contains iron, with a content of 1.1%.
• Each ingot has first undergone a first roughing with a beta press at 1050 ° C of the initial diameter ⁇ 200 nm squared 40 nm. The actual "transus beta" of the five alloys was determined at this stage, according to the method described for the 1st series of tests.
• FB and GB show the best compromises of the various properties including A% and the creep resistance at 400 ° C.
• FB which is the better of the two, especially in creep (38 h for 0.5% elongation) contains 5.4% Al - 4.2% Zr and 1.1% Fe.
• AB2 present on micrograph segregation ("beta flecks") linked to its 4.1% Cr content, which means that Cr contents at most equal to 2.5% are preferred, without this condition preventing good properties from being obtained (results from FB).

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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)
• Solid-Phase Diffusion Into Metallic Material Surfaces (AREA)
• Heat Treatment Of Steel (AREA)

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• 1987
  • 1987-04-16 FR FR8705786A patent/FR2614040B1/fr not_active Expired
• 1988
  • 1988-04-11 IL IL86029A patent/IL86029A/xx not_active IP Right Cessation
  • 1988-04-12 CA CA000563913A patent/CA1314792C/fr not_active Expired - Fee Related
  • 1988-04-13 EP EP88420121A patent/EP0287486B1/de not_active Expired - Lifetime
  • 1988-04-13 DE DE8888420121T patent/DE3861736D1/de not_active Expired - Lifetime
  • 1988-04-13 ES ES88420121T patent/ES2020341B3/es not_active Expired - Lifetime
  • 1988-04-13 DD DD88314702A patent/DD281422A5/de not_active IP Right Cessation
  • 1988-04-14 US US07/181,715 patent/US4854977A/en not_active Expired - Fee Related
  • 1988-04-14 ZA ZA882635A patent/ZA882635B/xx unknown
  • 1988-04-15 JP JP63093271A patent/JPH07116577B2/ja not_active Expired - Lifetime
  • 1988-04-15 BR BR8801837A patent/BR8801837A/pt not_active IP Right Cessation
  • 1988-10-26 US US07/262,792 patent/US4878966A/en not_active Expired - Fee Related

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