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: AI 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% 0.6% V, 0.5% Si, Ti complement and impurities.
• the Applicant has tried to obtain parts of the same alloy having a regular structure and without segregation, and having high mechanical characteristics at 20 ° C (Rm - R p0,2 - K ic ) with sufficient elongation as well as a creep resistance at 400 ° C significantly improved.
• 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 AI and Sn respectively give, 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 AI, and between 1.8 and 2.5% for Sn.
• the Zr has an important hardening role, and an embrittling effect above 5%, the Zr content is preferably between 3.5 and 4.8% and more preferably between 4.1 and 4.8%.
• the three elements AI, Sn and Zr do not entail fragility together, and it can be noted that the sum: taken as reference in FR 2 144 205 via with respect to the tendency of the comosed Ti 3 AI 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 a dircitation by precipitation of intermetallic compounds, it is known as lowering 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 increase in the 0 content increases, as is known, the mechanical resistance and slightly decreases the toughness (K ic ), it is therefore limited to a maximum of 0.15% and preferably maintained less than or equal to 0, 13%.
• a small addition of Si improves the creep resistance at 50 G -550 D C, it is limited to 0.3% maximum in the context of obtaining sufficient ductility.
• 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 dissolving is followed by ambient cooling with water or more usually with air. 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 - Rp o , 2 and K 1C ).
• the durations and tempering temperatures are typically chosen between 6 and 10 h and between 570 and 640 ° C.
• Each ingot has undergone a first roughing in beta at 1050 ° / 1100 ° C of the initial diameter 0 200 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 x 30 mm, at preheating temperature) equal to 50 ° C less than the estimated transus temperature 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.
• 3rd range (Table 5): a portion of the dishes of 70 x 30 mm obtained in the second range was applied an additional final forgeae at 60 x 30 mm starting from ("transus beta" + 30 ° C) and also ending in alpha-beta (needle structures with alpha phase lines were observed micrographically).
• 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 variably with respect to the real "transus beta" of the alloy. : for example 110 ° C less than this transus for AI, 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 strength and creep resistance.
• the comparison of the results of the 1st and 2nd ranges shows the importance of a final forging beginning in beta.
• the comparison of the results of the 2nd and 3rd ranges shows that the increase in the temperature at the start of this final forging above the "transus beta", resulting here in better homogenization during preheating and a greater proportion of the final working in the beta domain, causes a significant increase in mechanical strength, with consequently the possibility of obtaining a more interesting compromise of characteristics after adjustment of the tempering conditions. This also shows the importance of a precise adjustment of the final forging temperature compared to the real "transus beta" of the alloy.
• alloys D, J and E appear particularly interesting (mechanical resistance and creep resistance observed for the 2nd range), subject to a setting above 550 ° C of the tempering temperature.
• the first two contain 2, 1 and 1.9% iron, respectively.
• Each ingot has first sbi a first roughing in the beta press at 1050 ° C of the initial diameter 0 200 mm squared rb 40 mm.
• the hot wrought blanks obtained were heat treated: solution for 1 h at ("transus beta" of the alloy -30 ° C) followed by air cooling, then returned to 8 h at temperature (Table 8) chosen by a special procedure.
• This procedure consisted of processing small samples at staggered temperatures, followed by microhardness measurements H " 30 g and plotting the hardness curve as a function of the triat temperature, the temperature chosen for the income then corresponding to the minimum of hardness + 10%.
• the KB alloy has a catastrophic A% elongation, which shows the importance of finishing the final forging in alpha-beta (needle structure with alpha edges), to have sufficient ductility. This alloy could be of interest if its final forging had been slowed down so as to end in alpha-beta.
• 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 (384 h for 0.5% elongation) contains 5.4% AI -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)
• Heat Treatment Of Steel (AREA)
• Solid-Phase Diffusion Into Metallic Material Surfaces (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/fr 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
  • 1988-04-13 DE DE8888420121T patent/DE3861736D1/de not_active Expired - Lifetime
  • 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 BR BR8801837A patent/BR8801837A/pt not_active IP Right Cessation
  • 1988-04-15 JP JP63093271A patent/JPH07116577B2/ja not_active Expired - Lifetime
  • 1988-10-26 US US07/262,792 patent/US4878966A/en not_active Expired - Fee Related

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