TA11 A-4 (Ti-811) Titanium Alloy

TA11 Titanium Overview

  • Type: TA11 (Near-alpha titanium alloy )
  • Nominal Composition: Ti-8Al-1Mo-1V
  • Stabilizing Elements:
    • Alpha stabilizer: Aluminum (Al)
    • Isomorphous stabilizers: Molybdenum (Mo) and Vanadium (V)
  • Properties:
    • High elastic modulus
    • Low density
    • Highest specific stiffness among industrial titanium alloys
    • Room temperature tensile strength comparable to TCA alloy
    • Superior high-temperature strength and creep resistance compared to TC4 alloy
    • Higher sensitivity to thermal salt stress corrosion than TC4 alloy
  • Applications:
    • Used in the manufacture of high-pressure compressor disks, blades, and casings for aircraft engines
    • Maximum long-term operating temperature: 450°C
    • Commonly produced as bars, forgings, plates, strips, and welding wires
  • Density: 4.37 g/cm³

Material Technical Standards

  • XJ/BS 5163—1997: YZTi-811 alloy bars (Baotou Nonferrous Metals Processing Plant)
  • AMS 4972D—1990: Solution treated and stabilized Ti-8Al-1Mo-1V alloy bars, wires, and rings

Chemical Composition

ElementContent (%)
TiBalance
Al7.35-8.35
Mo0.75-1.25
V0.75-1.25
Fe≤0.30
C≤0.08
N≤0.05
H≤0.015
O≤0.12

Heat Treatment

  • Double Annealing:
    • 900-925°C for 1 hour, air cooling
    • 565-595°C for 8 hours, air cooling
  • Stress Relief Annealing:
    • 600-700°C for 0.25-4 hours, air cooling or furnace cooling

Melting and Casting Process

  • The alloy should undergo at least two vacuum consumable electrode arc melting processes.
  • Alloys used for manufacturing aircraft engine rotor parts should undergo three vacuum consumable melting processes.

Application Overview and Special Requirements

  • Application: Manufacturing of high-pressure compressor rotor blades for aircraft engines
  • Special Requirements: Due to the alloy’s sensitivity to chloride stress corrosion, caution is required when used in chloride-containing environments.

Oxidation Resistance

  • Comparable to TC4 alloy

Corrosion Resistance

  • Stable in atmospheric conditions and seawater
  • Sensitive to chloride stress corrosion at both high temperatures (thermal salt stress corrosion) and ambient temperatures (aqueous stress corrosion)

TA11 Titanium Alloy Microstructure

  • Rapid Cooling from Alpha + Beta Phase Region (below 900°C):
    • The beta phase transforms into martensitic structure
  • Rapid Cooling below this Temperature Range:
    • Beta phase rich in Mo and V is retained
  • Heating at 450°C:
    • Decomposition of beta phase
  • Primary Microstructure:
    • Mainly alpha phase with a small amount of beta phase

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