TA2 titanium alloy is a commercially pure titanium (CP titanium) widely used in various industries, equivalent to GR2 in ASTM standards and R50400 in UNS designations. It balances excellent corrosion resistance, formability, and moderate strength, making it a versatile material in demanding environments. Below is a detailed overview:
1. Chemical Composition
TA2 is primarily composed of high-purity titanium, with strict limits on impurity elements to ensure performance. Key components (by weight percentage) are:
Titanium (Ti): ≥99.2%
Oxygen (O): ≤0.25% (critical for balancing strength and ductility)
Iron (Fe): ≤0.30%
Carbon (C): ≤0.10%
Nitrogen (N): ≤0.03%
Hydrogen (H): ≤0.015%
Impurities like oxygen and iron slightly enhance strength but must be controlled to avoid reducing ductility and corrosion resistance.
2. Mechanical Properties
TA2 offers a moderate strength-ductility balance, suitable for applications requiring both formability and structural integrity:
Tensile strength: ≥345 MPa
Yield strength: ≥275 MPa
Elongation: ≥20% (excellent ductility for forming)
Hardness: ~70 HRB (Rockwell B scale)
Compared to lower-purity CP titanium (e.g., TA1/GR1), TA2 has higher strength due to slightly higher oxygen content, while maintaining good toughness.
3. Physical Properties
Density: 4.51 g/cm³ (about 60% of steel, enabling lightweight designs)
Melting point: ~1668°C (high temperature stability)
Thermal conductivity: 16.8 W/(m·K) (low, requiring careful heat management during machining)
Electrical resistivity: ~42 μΩ·cm
Modulus of elasticity: ~103 GPa (stiffer than aluminum but more flexible than steel)
4. Key Characteristics
Superior Corrosion Resistance:
Forms a dense, self-healing titanium dioxide (TiO₂) film on its surface, resisting corrosion in:
Seawater and marine environments (resists pitting and crevice corrosion better than stainless steel).
Organic acids (e.g., acetic acid, formic acid) and dilute inorganic acids (e.g., sulfuric acid, hydrochloric acid, at low concentrations/temperatures).
Alkali solutions (except high-concentration, high-temperature caustics).
Excellent Formability:
Can be cold-worked via bending, rolling, deep drawing, and spinning. It retains ductility even after moderate cold deformation, making it ideal for complex shapes (e.g., thin-walled tubes, sheets).
Good Weldability:
Welds well using processes like TIG (tungsten inert gas) and plasma welding, with minimal loss of base metal properties in joints. Proper shielding (e.g., argon gas) prevents contamination by oxygen/nitrogen during welding.
Biocompatibility:
Chemically inert in the human body, non-toxic, and non-allergenic. It does not react with bodily fluids or tissues, making it safe for long-term implantation.
5. Typical Applications
TA2’s versatility makes it indispensable in multiple sectors:
Chemical & Petrochemical Industry:
Storage tanks, pipelines, and heat exchangers for corrosive fluids.
Pumps, valves, and fittings handling acids, brines, or chlorides.
Aerospace & Marine:
Aircraft hydraulic lines, fuel tanks, and structural components (where lightweight and corrosion resistance are critical).
Ship hulls, propeller shafts, and offshore drilling components (resisting seawater corrosion).
Medical Field:
Surgical instruments, orthopedic implants (e.g., bone plates, screws), and dental fixtures (due to biocompatibility and corrosion resistance in bodily fluids).
Consumer & Industrial:
Desalination plants (membrane housings, evaporators).
Sports equipment (golf club heads, bicycle frames) for strength-to-weight ratio.
6. Processing Considerations
Machining: Low thermal conductivity can cause tool overheating; use sharp tools, coolants, and slow speeds.
Heat Treatment: Not typically heat-treated (strengthening relies on cold working).
Surface Treatment: May be polished or anodized for enhanced wear resistance or aesthetic purposes.
In summary, TA2 titanium alloy is a reliable choice for applications demanding corrosion resistance, formability, and moderate strength, bridging the gap between lower-strength pure titanium (TA1) and higher-strength alloys (e.g., TA3, TC4).