UNS R56400 (Titanium alloy 6Al-4V)

Short Introduction:

  • Titanium alloy 6Al-4V is the most widely used of all the alpha-beta titanium alloys. It is typically used in the annealed condition, at service temperatures through 750°F. However it may be heat treated for high strength in sections under 4″ thick. Harden ability is limited and sections over one inch may not develop full properties. HY Titanium 6-4 is welded with matching or with ELI filler wire.

  •  Mill anneal: 1300-1450°F 2 hours, air cool. Re-crystallization anneal bar for better ductility and fatigue strength, 1750°F 2 hours, furnace cool.

    For maximum fracture toughness and SCC resistance: Beta anneal 1950°F 1-2 hours, water quench. Then age 1150-1300°F 2 to 4 hours, air cool.

    For maximum strength: solution-treated and aged (STA) condition is: For sheet, 1675-1725°F 5 to 25 minutes, water quench. Age 975°F 4 to 6 hours, air cool. For bars and forgings, 1675-1725°F 1 hour, water quench. Age 975-1025°F 3 hours, air cool.

    For increased fracture toughness, but lower tensile strength: precipitation treat (overage) 1150-1250°F 4 hours, air cool. Stress relief annealing is commonly 1000-1200°F 1 to 4 hours, air cool.

  • Titanium alloy 6Al-4V is resistant to general corrosion but may be quickly attacked by environments that cause breakdown of the protective oxide. These include hydrofluoric (HF), hydroelectric (HCl), sulfuric and phosphoric acids. Inhibitors may help for the last four but not for HF. HY Titanium 6-4 resists attack by pure hydrocarbons, and most chlorinated and fluoridated hydrocarbons (provided water has not caused formation of small amounts of HCl and HF.

  • Titanium alloy 6Al-4V is susceptible to chloride stress corrosion cracking (SCC), although being among the better of the titanium alloys in this regard. For marine environments silver plated bolts are not used, as silver bonds easily with chlorine in this environment. HY Titanium 6-4 is also susceptible to SCC in environments such as methyl alcohol, red fuming HNO3, and N2O4. In the case of red fuming nitrate acid, the problem is limited to environments containing less than 1.5% water, or more than 6% NO2. Failure in N2O4 has occurred when oxygen and chlorides were present as impurities.

Category:

Description

UNS R56400 (Titanium alloy 6Al-4V)

UNS R56400 (Titanium alloy 6Al-4V)

Material grades and equivalents Titanium alloy 6Al-4V /UNS R56400

 

Chemistry Composition

Element  Al V C N O H Fe Y Others,
Each
Others,
Total
Ti
MIN 5.5 3.5
MAX 6.75 4.5 0.08 0.05 0.2 0.0125 0.3 0.005 0.1 0.4 Balance

 

Features

  • High strength to 600°F
  • Excellent general corrosion resistance
  • High strength-to-weight ratio

Applications

  • Turbine blades, discs and rings
  • Aircraft structural components
  • Weapons structural components
  • Fasteners
  • Medical and dental implants
  • Hand tools
  • Sporting equipment
  • Chemical process equipment

Physical Properties

Density: 0.160 lb/inch3
Melting Range: 2929 – 3020°F
Beta Transus: 1825± 25°F

Temperature, °F 70 200 400 600
Coefficient of Thermal Expansion, in/in°F x 10-6 - 5.3 5.4 5.5
Thermal Conductivity,

Btu • Ft/Ft² • Hr°F STA

4.0 4.3 5.2 6.1
Modulus of Elasticity,

psi X 106 STA

16.7 16.0 15.0 14.0

 

Mechanical Properties:

Specified, AMS 4911, annealed sheet & plate

  Anneal 1300°F, Air Cool Anneal 1300°F, Solution anneal 1750°F , Age 1000°F
Ultimate Tensile Strength, ksi 138-155 150-172
0.2% Yield Strength, ksi 128-147 137-156
Elongation, % 15-20 15-17
Reduction of Area, % 38-51 41-46

 

Typical Tensile Strength and Fracture Toughness, Various Heat Treatments for Flat-rolled Products (MCIC-HB-02 1985 reprint)

0.2% Yield Strength, ksi Fracture Toughness K1C, ksi √in
Annealed
(Continuously Rolled Sheet)
132 142 (transversea) 128 140 (transversea)
Beta Annealed (plate) 131 134
Beta STA 1250°F b 128 150
Beta STA 1000°F b 143 120
STA 1250°Fc 137 105
STA 1000°Fc 159 80

(a) Directional variations,
(b) Beta heat treated followed by solution treating and overaging 1250˚F, or aging 1000˚F
(c) Solution treating and overaging 1250˚F, or aging 1000˚F