Titanium Grade 9 – Ti-3Al-2.5V

Titanium Grade 9 (Ti-3Al-2.5V) is a near-alpha (α-β) titanium alloy that offers an excellent balance of strength, formability, corrosion resistance, and weldability. It is widely regarded as the “workhorse tubing alloy” of the titanium family, positioned between commercially pure titanium and Ti-6Al-4V.

Material Classification

Microstructure & Metallurgical Behavior

Predominantly equiaxed α-grains with a thin β-phase at grain boundaries. Strength is achieved through solid-solution strengthening from aluminum and vanadium, along with controlled oxygen content.

✔ Not heat-treatable for major strengthening
✔ Stress-relief annealing improves fatigue life
✔ Superior cold-workability compared to Ti-6Al-4V

Corrosion & Environmental Resistance

Titanium Grade 9 forms a stable TiO₂ passive layer, providing excellent resistance to:

✔ Seawater & marine atmospheres
✔ Chlorides
✔ Weak acids and alkalis
✔ Oxidizing environments
✔ Stress corrosion cracking

Fabrication & Processing

Formability: Excellent, especially for thin-wall tubing and cold-formed parts
Weldability: Excellent (TIG, MIG, EBW); no post-weld heat treatment typically required
Machinability: Better than Grade 5, harder than CP titanium

Advantages

✔ Excellent strength-to-weight ratio
✔ Superior formability for tubing and thin sections
✔ Outstanding weldability
✔ Excellent corrosion resistance
✔ Cost-effective alternative to Ti-6Al-4V

Limitations

⚠ Lower maximum strength than Grade 5 / Grade 23
⚠ Not intended for very high-temperature aerospace structures
⚠ Limited availability in very thick sections

Grade Comparison

Summary:
Titanium Grade 9 (Ti-3Al-2.5V) bridges the gap between commercially pure titanium and Ti-6Al-4V. Its combination of strength, excellent formability, weldability, and corrosion resistance makes it the preferred choice for aerospace tubing, marine systems, industrial piping, and performance engineering.