Classifications

• • 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
• • 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

Definitions

• Beta titanium-base alloys containing 15-35% molybdenum, 1535% vanadium, up to 5% zirconium, .01-0.2% boron, 0.15% hafnium, .0l.2% carbon, up to 5% of at least one element selected from the group consisting of W, Ta, Nb, Cr and Al and the balance Ti are strengthened by heating the alloy to a temperature between 1300 C. and 1500 C. at which the precipitateforming elements dissolve in a beta matrix, cooling the alloy to retain the precipitate-forming elements in solution in the matrix and subsequently ageing the alloy at a temperature between 500 C. and 950 C. to form a very fine precipitate.
• This invention relates to a method of heat-treating beta titanium-base alloys.
• beta titanium-base alloys having good creep strength containing, by weight, 1535% molybdenum, 1535% vanadium, the total molybdenum plus vanadium content being in the range 40-55%, up to 8% zirconium, 0.010.2% boron, balance titanium.
• Incidental alloying elements which may also be present include 5% tungsten, tantalum, niobium, chromium and aluminum. In such alloys 0.1 hafnium and 0.0l0.2% carbon may also be present. In such alloys, carbon and boron combine with the other elements present, notably zirconium to form complex precipitates. Such alloys are hereinafter referred to as alloys of the kind described.
• alloys of the kind described are strongest when the precipitates are finely and uniformly distributed in the beta matrix and that the re quired particle size and distribution can be consistently produced by the treatment now to be described.
• solution treatment temperature The solubility of carbon and boron in these alloys increases with increasing temperature, so that most of t tent the carbon and boron is in solution at temperatures above about 1100 C., which thus defines a lower limit for the solution treatment temperature.
• Solution of carbon and boron is complete in laboratory samples after only short times at temperatures above 1100 C., but solution treatment times will in practice be suited to section size, according to accepted practice in titanium metallurgy. Solution treatment may be terminated either by cooling in air or by quenching in one of the several liquids which are in general use.
• the matrix may be nucleated with the maximum number of sites by quenching or by working the material by forging or extrusion following solution treatment.
• Precipitation is carried out by heating at temperatures between 500 and 950 C., the time required to produce a suitable precipitate decreasing with increasing temperature.
• the precipitate can be formed during air cooling after hot working at the solution treatment temperature or during warm Working after solution treatment and quenching.
• the product is strongest when the precipitates are so finely divided that they are only resolvable in the electron microscope according to Well-established principles. It is necessary, therefore, to provide as many nucleation sites as possible for precipitation.
• precipitation has been carried out at too high a temperature or for too long a time at a certain temperature, the particles grow too large and do little to strengthen the alloy. Examples of the effect of heat treatment, as described above, on the strength of the alloys as measured by stress-rupture tests are shown in Table I.
• treatment B produces inferior results to treatment A.
• results may be explained in terms of the theory of dispersion hardening as briefly outlined above.
• treatment A precipitates are dissolved at 1300" C. and precipitated uniformly and in a finely divided form on subsequent ageing at 650 C.
• treatment B although a high density of nuclei is created by warm-working at 800 C., the carbide formers are not in solution prior to warm-working and are not mobile enough to redistribute on the nucleation sites during ageing.
• Treatment A is typical of the heattreatments that strengthen the alloy. Further more detailed examples of the effect of heat treatment are given in Table II.
• Solution treatment and working is carried out at a temperature above 1100 C., but not greatly in excess of 1450 C. (1500 C. as a maximum) to avoid undue oxidation. If the material is then worked from the solution treatment temperature, sufiicient nucleation sites are created during working and a fine precipitate forms during air cooling following working. If the material is not worked after solution treatment, the cooling rate must be fast enough to retain the precipitate-forming elements in solution down to the ageing temperature. With laboratory samples, air cooling is sufiicient, but with larger samples quenching in one of the several liquids which are in general use is necessary. Ageing is then carried out at temperatures above 500 C., below which the diffusion of the precipitate-forming elements is so slow as to preclude their formation. The upper limit for ageing is that temperature at which undue coarsing of the precipitate occurs, which for these alloys is approximately 950 C. Ageing time is selected in accordance with temperature,
• a method of heat-treating a beta titanium-base alloy consisting essentially of, by weight, beta matrix-forming elements molybdenum 15-35% and vanadium 15-35%, the total of said molybdenum and vanadium together being 40-55%, up to 5% zirconium, 0.010.2% boron, up to 5% of at least one metal selected from the group consisting of tungsten, tantalum, niobium, chromium and aluminum, and precipitate-forming elements hafnium 0.1- 5% and carbon 0.01-0.2%, balance titanium, said method comprising the steps of (a) heating said alloy at a temperature between 1300 C. and 1500 C. to effect solution of said precipitateforming elements in said beta matrix whereby said beta matrix is nucleated with a maximum number of nucleation sites,
• a method of heat-treating a beta titanium-base alloy consisting essentially of, by weight, beta matrix-forming elements molybdenum 15-35% and vanadium 15-35%, the total of said molybdenum and vanadium together being 40-55%, up to 5% zirconium, 0.0l-0.2% boron, up to 5% of at least one metal selected from the group consisting of tungsten, tantalum, niobium, chromium and aluminum, and precipitate-forming elements hafnium 0.1- 5% and carbon 0.01-0.2%, balance titanium, said method comprising the steps of (a) hot working said alloy at a temperature between 1300 C. and 1500 C. to effect solution of said precipitate-forming elements and to form a maximum number of nucleation sites in said beta matrix,
• a method of heat-treating a beta titanium-base alloy consisting essentially of, by weight, beta matrix-forming elements molybdenum 15-35% and vanadium 15-35%, the total of said molybdenum and vanadium together being 40-55%, up to 5% zirconium, 0.010.2% boron, up to 5% of at least one metal selected from the group consisting of tungsten, tantalum, niobium, chromium and aluminum, and precipitate-forming elements hafnium 0.1- 5% and carbon 0.01-0.2%, balance titanium, said method comprising the steps of (a) heating said alloy at a temperature of 1300 C.,
• a method of heat-treating a beta titanium-base alloy consisting essentially of, by weight, beta matrix-forming elements molybdenum 1535% and vanadium 15-35%, the total of said molybdenum and vanadium together being 40-55%, up to 5% Zirconium, 0.0l0.2% boron, up to 5% of at least one metal selected from the group consisting of tungsten, tantalum, niobium, chromium and aluminum, and precipitate-forming elements hafnium 0.1- 5% and carbon 0.01-0.2%, balance titanium, said method comprising the steps of (a) heating said alloy at a temperature between 1300 C. and 1500 C. at which said precipitate-forming elements dissolve in said beta matrix,
• a method of treating an alloy consisting of, by weight 20% molybdenum, 20% vanadium, 4% zirconium, 0.05% boron, balance titanium and impurities comprising heating the alloy at 1400 C., water quenching and ageing for 1 hour at 650 C.
• a method of treating an alloy consisting of, by weight 22% molybdenum, 22% vanadium, 4% tungsten, 4% zirconium, 0.3% carbon, balance titanium and impurities comprising heating and extruding the alloy at 1370 C. and air cooling at a rate suitable for the formation of a fine precipitate.

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Citations (3)

• 1965
  • 1965-06-23 GB GB26600/65A patent/GB1144304A/en not_active Expired
• 1966
  • 1966-06-17 US US558240A patent/US3444009A/en not_active Expired - Lifetime
  • 1966-06-23 BE BE683033D patent/BE683033A/xx unknown

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