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Dr. Dmitri Kopeliovich
Titanium α-alloys consist entirely of α-phase. They contain aluminum (Al) as the major alloying element, stabilizing α-phase.
Titanium near α-alloys contain small amount of ductile β-phase. Besides α-phase stabilizer (aluminum), Near α-Alloys are alloyed by 1-2% of β-phase stabilizers (molybdenum, silicon).
Alloying elements in titanium α-alloys and Near α-alloys provide also solution strengthening.
Aluminum is the most effective strengthener of the alloys.
Titanium α-Alloys and Near α-Alloys have good Fracture Toughness and creep resistance combined with moderate mechanical strength, which is retained at increased temperatures up to 1100 ºF (600ºC).
The alloys are easily welded, but their workability in hot state is poor.
Due to the presence of β-phase in Near α-Alloys they may be heat-treated and are forged in hot state.
Titanium α-Alloys and Near α-Alloys are used for manufacturing steam turbine blades, autoclaves and other process equipment vessels operating up to 900 ºF (480ºC), high pressure cryogenic vessels, aircraft engine compressor blades, missile fuel tanks and structural parts, operating for short times up to 1100 ºF (600ºC), airframe and jet-engine parts, welded stator assemblies and hollow compressor blades.
| Designation | O,% | Fe,% | Al,% | Sn,% | Mo,% | Zr,% | Others,% |
|---|---|---|---|---|---|---|---|
| Grade 6 (Ti-5Al-2.5Sn) | 0.20 max. | 0.5 max. | 4.0-6.0 | 2.0-3.0 | - | - | - |
| Ti-8Al-1Mo-1V | 0.12 max. | - | 7.5-8.5 | - | 0.75-1.75 | - | V=0.75-1.75 |
| Ti-6Al-2Sn-4Zr-2Mo-0.1Si | 0.25 max. | 0.25 max. | 5.5-6.5 | 1.75-2.25 | 1.75-2.25 | 3.5-4.5 | Si=0.1 max. |
| Ti-5.5Al-3.5Sn-3Zr-1Nb | 0.09-0.15 | - | 5.2-5.7 | 3.0-4.0 | 0.2-0.35 | 2.5-3.5 | Si=0.2-0.5, Nb=0.7-1.3 |
(Concentration of nickel - balance)
