TA7 Titanium Alloy for Parts such as Liners

TA7 alloy is a medium-strength, α-type titanium alloy whose properties cannot be enhanced by heat treatment. It is typically used in the annealed condition and possesses excellent fracture toughness at both room and elevated temperatures. The alloy features good fusion weldability and is suitable for Tungsten Inert Gas (TIG) and Metal Inert Gas (MIG) welding processes under inert gas protection. It can be used to manufacture components like casing housings and wall panels. The alloy's long-term service temperature can reach 500°C, with a short-term service temperature up to 800°C. TA7 ELI alloy is a version with low interstitial impurity elements, making it suitable for low-temperature applications. Available semi-finished products include sheet, bar, pancake, and ring forgings, and it can also be used to produce castings.

Material Grades: TA7, TA7 ELI, ZTA7.

Similar Grades: Ti-5Al-2.5Sn (USA), BT5-1 (Russia), IMI317 (UK).

Key Technical Standards: Multiple Chinese national (GB), military (GJB), and aerospace (HB) standards, as well as AMS standards, cover its chemical composition, sheet, bar, forgings, and castings.

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According to standards including GB/T 3620.1-1994 and GJB 2896-1997, the main components of TA7 alloy are:

Titanium (Ti): Base

Aluminum (Al): 4.0 - 6.0%

Tin (Sn): 2.0 - 3.0%
Impurity elements (Fe, Si, C, N, H, O, etc.) are strictly controlled within specified limits.

Annealing:

Sheet: 700–800°C, 10–120 min, air cool.

Bars & Forgings: 750–850°C, 0.5–4 h, air cool.

Castings: 600–700°C, 1–2 h, air cool or furnace cool.

Stress Relief Annealing: 540–650°C, 15–360 min, air cool or furnace cool.

Hot Isostatic Pressing (HIP) for Castings: At 910±10°C under 100–140 MPa argon pressure for 2–2.5 h, then furnace cool below 300°C.

Melting & Casting: Ingots should undergo two or more cycles of Vacuum Arc Remelting (VAR). Alloying elements Al and Sn are added as an Al-Sn master alloy. Consumable electrode welding uses plasma welding under argon protection; TIG welding is strictly prohibited. Castings are produced using vacuum arc skull furnaces with various mold types.

Application Overview: Components such as engine adapter mounts, front casing housings, sealing ring housings made from TA7 alloy die forgings and rings, as well as liners, bracket mounts, and wall panels formed by hot pressing of sheets, have been used in the aviation industry.

Special Requirement (Brittleness): TA7 alloy is relatively sensitive to increased brittleness caused by higher levels of interstitial elements and impurities, especially when used under cryogenic conditions.

Thermal Properties:

Melting Temperature Range: 1540 – 1650°C

Density: 4.42 g/cm³

Magnetic Properties: Non-magnetic.

Corrosion Resistance: Stable under atmospheric conditions and in seawater. However, compared to TC4 alloy, it is more susceptible to hot salt stress corrosion. Stress corrosion can occur when exposed for 100 hours in an environment heavily coated with artificial sea salt at 316°C and under a stress of 207 MPa.

Phase Transformation Temperatures:

β → α+β transus: 1040 – 1090°C

α → α+β transus: 930 – 970°C

Microstructural Characteristics: The equilibrium microstructure below the α→α+β transus (approx. 950°C) is single-phase α. Rapid cooling from different phase fields results in α' or α'' phases, which decompose into α-phase during annealing.

The alloy has good weldability. TIG or MIG welding with inert gas protection can ensure the alloy maintains high toughness at low temperatures. Brazing is generally avoided due to potential brittleness from intermetallic compounds. Commonly used methods include argon arc, spot, and seam welding. Argon arc welded joints show high strength coefficients at room, high, and low temperatures. Seam welded joints exhibit high strength coefficients at room and high temperatures but a lower coefficient at low temperature.

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Our factory operates a dedicated production facility equipped with modern machinery for processing titanium. We have a complete set of equipment including forging presses, hot and cold rolling mills, tube drawing and welding lines, bar & wire drawing machines, and surface treatment units. This allows us to control the production process from raw material to finished products such as sheets, plates, tubes, bars, and wires. Our workshop is capable of handling large-volume orders while maintaining consistent quality across our product range.

Our packaging is designed for maximum security and international standards. We use tailored wooden crates for heavy plates and bars, with internal waterproof wrapping and blocking to prevent movement. Tubes and coils are securely packed in wooden boxes with reinforced edges and protective end caps. For smaller items like wires and strips, we use standard export cartons with inner plastic and moisture-proof sealing. All packages are clearly marked with product details, weight, and handling instructions to ensure safe arrival. We can also customize packing methods, such as palletization or container optimization, based on specific shipping and customer requirements.

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