WO1994023080A1 - ALLIAGE DE TITANE A PHASE β AMELIOREE - Google Patents

ALLIAGE DE TITANE A PHASE β AMELIOREE Download PDF

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Publication number
WO1994023080A1
WO1994023080A1 PCT/GB1994/000639 GB9400639W WO9423080A1 WO 1994023080 A1 WO1994023080 A1 WO 1994023080A1 GB 9400639 W GB9400639 W GB 9400639W WO 9423080 A1 WO9423080 A1 WO 9423080A1
Authority
WO
WIPO (PCT)
Prior art keywords
alloy
alloys
fracture toughness
titanium
mpa
Prior art date
Application number
PCT/GB1994/000639
Other languages
English (en)
Inventor
Harvey Millard Flower
David Richard Frederick West
Anthony Ifeanyi Paul Nwobu
Original Assignee
The Secretary Of State For Defense
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by The Secretary Of State For Defense filed Critical The Secretary Of State For Defense
Publication of WO1994023080A1 publication Critical patent/WO1994023080A1/fr

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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

Definitions

  • This invention relates to an improved titanium base alloy and more particularly to titanium base alloys including vanadium, aluminium and iron as essential constituents.
  • High strength and toughness as well as good hot workability are important in thick section titanium forgings such as compressor discs and helicopter rotor heads.
  • Applications for titanium alloys where good cold formability is required include springs, fasteners and honeycomb structures. In order to obtain high strength the alloy must have sufficient fracture toughness to prevent failure in the presence of microscopic flaws.
  • Elemental titanium at ambient temperatures is of a close packed hexagonal structure commonly called the ⁇ -phase, whilst at a temperature of 883°C or higher it transforms to a body-centered cubic structure known as the ⁇ -phase.
  • the ⁇ -phase is stabilised by aluminium, preferably in the range 2.5 to 8% by weight, which leads to an increase in the mechanical strength and hardness of the resulting alloy while retaining the alloy in a sufficient ductility for fabrication processes.
  • UK Patent No. 782564 describes improvements relating to titanium-aluminium base alloys.
  • This document lists the mechanical properties of titanium alloys including three containing additions of aluminium, vanadium or iron having the following point compositions: Ti-5V-*4A1, Ti-10V-4Al and Ti ⁇ 5V-l.5Fe-*Al.
  • More recently developed alloys include the Transage series (e.g. T12 Q ) and Ti-10-2-3 (a titanium alloy comprising 10. vanadium, 2% iron, 3% aluminium, proportions being in weight % ) .
  • T12 Q Transage series
  • Ti-10-2-3 a titanium alloy comprising 10. vanadium, 2% iron, 3% aluminium, proportions being in weight %
  • the latter of these two alloys is described in the US Patent No. 3802877- Vanadium is employed as the principal ⁇ -stabilising element and small additions of aluminium reduce density and increase hardenability.
  • the invention is a near ⁇ -phase titanium base alloy comprising the following constituents in proportions by weight:
  • a preferred composition for the improved titanium alloy comprises:
  • a near ⁇ -phase alloy is one in which a significant proportion of the structure is ⁇ -phase.
  • alloys according to the invention are heat treated to obtain the requisite microstructure for maximum fracture toughness and fatigue strength.
  • the alloys are annealed at 800°C, water quenched and then aged in a salt bath at 525°C over a period of 8 hours.
  • Figure 1 shows the age hardening curves of the Ti-12V-l.5Fe-4Al alloy aged in salt baths at 350-600°C.
  • Figure 2 shows yield stress against fracture toughness the alloy Ti-12V-1.5Fe-*4Al compared to that of a prior art alloy Ti-10V-2Fe ⁇ 3Al.
  • Figure 3 shows yield stress against tensile elongation for the alloy Ti-12V-1.5Fe-*.Al compared to that of a prior art alloy Ti-10V-2Fe-3Al.
  • Figure 1 shows the age-hardening curves of alloys having compositions falling within the invention and aged in salt baths at 350-600 c C. Such alloys attain the maximum hardening and hardness of about 500Hv which is unchanged over a temperature range of 350-*00°C. Age-hardening at temperatures above these temperature ranges is lower and decreases with the rise in ageing temperature. Annealing at temperatures high in the
  • Table 1 shows the tensile properties and fracture toughness values of the age-hardened Ti-12V-1.5Fe-*Al alloy.
  • the table shows the annealing treatment followed by any subsequent age hardening. The duration of each treatment is given in hours(h) or minutes(m).
  • the Ti-12V-1.5Fe-4Al alloy shows excellent tensile ductility.
  • the alloy shows a tensile elongation of 5-8/..
  • the tensile ductility is reduced and is also affected by heating rate used during ageing (1321 MPa / 0% combination of a furnace aged condition compared to 1298 MPa / % combination of a salt bath aged condition) .
  • Fracture toughness of the age hardened alloy is affected by the prior annealing temperature.
  • the fracture toughness of the ⁇ -quenched and aged alloy is compared to that of the high (a + ⁇ ) annealed and aged condition, the latter condition shows better fracture toughness (80 MPam 1/2 for yield stress of 1248 MPa against 60.3 MPam 1/2 for 1233 MPa of the ⁇ -quenched and aged condition; Table 1).
  • Salt bath and furnace ageing has little effect on the fracture toughness of the alloy since a precipitate morphology is little affected by the salt bath and furnace ageing.
  • the alloy annealed at 750 °C (also 50°C below the ⁇ -transus) and aged at 500°C shows similar fracture toughness values, 63 and 59 MPam 1 2 for the salt bath and furnace aged conditions that show the yield stress values respectively 131 and 1321 MPa. Even in the ⁇ quenched and aged condition in which furnace ageing deteriorates tensile elongation (1564 MPa/0.8j.
  • the mechanical properties of the invention are compared with those reported for the Ti-10-2-3 alloy in figures 2 and 3- These figures show respectively yield stress versus tensile elongation and yield stress versus fracture toughness values for the ( ⁇ + ⁇ ) microstructure and demonstate that the invention has superior yield stress/ ductility/fracture toughness combinations compared to the Ti-10-2-3 alloy.
  • Figure 2 shows that at yield stress of 1200-1500 MPa, the fracture toughness values of the invention developed here are higher than those of Ti-10-2-3 alloy. For example at a yield stress of about 1250 MPa the alloy according to the invention shows fracture toughness values of 80 Mpam 1 2 compared to 4l MPam 1 2 observed for the Ti-10-2-3 alloy.
  • the fracture toughness of the invention is superior at 65 MPam 1 2 compared to a value of 30 MPam 1/2 observed for the Ti-10-2-3 alloy.
  • the bimodal structure of the alloys show tensile elongation of 3 ⁇ 1% compared with the tensile elongation of 2-4 % for the Ti-10-2-3 alloy (Fig 3).
  • Alloys according to the invention show improved mechanical properties compared to the Ti-10-2-3 alloy because they use the optimum V, Fe and Al combinations to achieve after processing the most attractive ( ⁇ + ⁇ ) microstructure at high strength levels. They do not depend on the transitional ⁇ > ⁇ + ⁇ reaction as in Ti-10-2-3 alloy to achieve the high strength in the ( ⁇ + ⁇ ) structure.
  • the uniform a type structure of the Ti-10-2-3 alloy shows poor fracture toughness.
  • a plates of high aspect ratio and of a zig zag morphology are observed at temperatures in which the ⁇ > __> + ⁇ reactions occur in the Ti-10-2-3 alloy. This enhances fracture toughness in the new alloys.
  • Table 1 Mechanical Properties of Ti-12V-1 .5Fe-4Al Alloy
  • T-S Transverse-short, furnace ageing
  • T-L Transbverse long, Longitudinal direction
  • WQ Water quenching Transverse direction
  • AC Air-cooling

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Heat Treatment Of Steel (AREA)

Abstract

Alliages de titane caractérisés par une résistance, une ductilité et une ténacité à la rupture supérieures par rapport aux alliages de l'art antérieur, qui contiennent (en pourcentage pondéral) 11,5 à 12,5 % de vanadium, 1,1 à 1,7 % de fer et 3,5 à 4,2 % d'aluminium. Selon l'invention, il est préférable de soumettre les alliages à un traitement thermique pour leur conférer une ténacité à la rupture et une résistance à la fatigue maximales. Le traitement thermique comporte le recuit entre 790 et 810°C, la trempe à l'eau pendant 1 à 6 heures et le vieillissement dans un bain de sel entre 500 et 530 °C pendant 6 à 10 heures.
PCT/GB1994/000639 1993-04-01 1994-03-28 ALLIAGE DE TITANE A PHASE β AMELIOREE WO1994023080A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB939306864A GB9306864D0 (en) 1993-04-01 1993-04-01 Titanium alloy
GB9306864.1 1993-04-01

Publications (1)

Publication Number Publication Date
WO1994023080A1 true WO1994023080A1 (fr) 1994-10-13

Family

ID=10733196

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB1994/000639 WO1994023080A1 (fr) 1993-04-01 1994-03-28 ALLIAGE DE TITANE A PHASE β AMELIOREE

Country Status (2)

Country Link
GB (1) GB9306864D0 (fr)
WO (1) WO1994023080A1 (fr)

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1124962A (en) * 1965-05-22 1968-08-21 Imp Metal Ind Kynoch Ltd Improvements in or relating to titanium alloys
WO1985003190A2 (fr) * 1984-01-19 1985-08-01 Sundstrand Data Control, Inc. ALLIAGE DE TITANE (10V-2Fe-3Al) POUR UN ENREGISTREUR DE DONNEES D'UN AERONEF
EP0202791A1 (fr) * 1985-04-25 1986-11-26 Daido Tokushuko Kabushiki Kaisha Alliages à base de titane

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1124962A (en) * 1965-05-22 1968-08-21 Imp Metal Ind Kynoch Ltd Improvements in or relating to titanium alloys
WO1985003190A2 (fr) * 1984-01-19 1985-08-01 Sundstrand Data Control, Inc. ALLIAGE DE TITANE (10V-2Fe-3Al) POUR UN ENREGISTREUR DE DONNEES D'UN AERONEF
EP0169242A1 (fr) * 1984-01-19 1986-01-29 Sundstrand Data Control, Inc. ALLIAGE DE TITANE (10V-2Fe-3Al) POUR UN ENREGISTREUR DE DONNEES D'UN AERONEF
EP0202791A1 (fr) * 1985-04-25 1986-11-26 Daido Tokushuko Kabushiki Kaisha Alliages à base de titane

Also Published As

Publication number Publication date
GB9306864D0 (en) 1993-05-26

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