Grade 7 titanium (UNS R52400) is a titanium-palladium alloy (containing ~0.12–0.25% palladium) renowned for its exceptional corrosion resistance, making it a premier choice for harsh chemical and aqueous environments. Its key characteristics are defined by both material properties and practical performance:
Superior Corrosion Resistance
It exhibits outstanding resistance to general corrosion, pitting, crevice corrosion, and stress corrosion cracking (SCC) in aggressive media. This includes oxidizing acids (e.g., nitric acid), reducing acids (e.g., hydrochloric acid, sulfuric acid), saltwater, and chloride-containing solutions-environments where unalloyed titanium (e.g., Grade 2) may fail. The palladium addition acts as a cathodic stabilizer, preventing localized corrosion.
Mechanical Properties Balance
It maintains moderate strength (lower than high-strength titanium alloys like Grade 5) with excellent ductility and formability. It can be easily fabricated via rolling, forging, welding, bending, and machining, while retaining structural integrity under mechanical stress.
Biocompatibility and Temperature Stability
It is biocompatible (suitable for some medical applications) and performs reliably across a wide temperature range: from cryogenic temperatures (retaining toughness) to moderate elevated temperatures (up to ~315°C/600°F, where its corrosion resistance and mechanical properties remain stable).
Lightweight and Non-Magnetic
Like all titanium alloys, it has a low density (~4.51 g/cm³)-about 60% of steel-offering weight savings in structural designs. It is also non-magnetic, making it ideal for applications requiring magnetic neutrality (e.g., aerospace, electronics).
Chemical Inertness
It is inert to most organic compounds, alkalis, and many industrial chemicals, avoiding contamination of processes or materials it contacts (critical for chemical processing, pharmaceutical, and food industries).
The yield strength of Grade 7 titanium is defined by its minimum specified value for fully annealed material (the most common supply condition), with slight variations based on product form (sheet, plate, bar, tube) and thickness:
Minimum Yield Strength (0.2% Offset): 275 MPa (40 ksi)
Typical Yield Strength: 310–380 MPa (45–55 ksi)
For example:
Sheet/plate (≤12.7 mm thickness): 275 MPa (40 ksi) min
Bar/tube (annealed): 275 MPa (40 ksi) min
Note: Cold-worked Grade 7 titanium (e.g., half-hard, full-hard) will have higher yield strength (e.g., up to 550 MPa/80 ksi), but annealed material is standard for corrosion-focused applications to maximize ductility and corrosion resistance.
The tensile strength of Grade 7 titanium is specified to ensure structural reliability, with consistent ranges across product forms (annealed condition):
Minimum Tensile Strength: 485 MPa (70 ksi)
Typical Tensile Strength: 550–650 MPa (80–94 ksi)
Elongation at Break: 20–25% (minimum 20% for most product forms)
Key details:
The tensile strength is significantly higher than unalloyed Grade 2 titanium (485 MPa min vs. 345 MPa min for Grade 2), while retaining better corrosion resistance.
For cold-worked material, tensile strength can exceed 700 MPa (100 ksi), but this is less common as it may reduce formability and corrosion performance in extreme environments.
