Titanium Grade Selection: Grade 2 vs Grade 5 vs Grade 9 Compared
Selecting the right titanium grade is critical for achieving the optimal balance of strength, corrosion resistance, and cost for your application. This comprehensive guide compares the three most common commercial titanium grades: Grade 2 (CP Ti), Grade 5 (Ti-6Al-4V), and Grade 9 (Ti-3Al-2.5V).
Understanding Titanium Grades
Titanium grades are classified as:
- Commercially Pure (CP) Titanium: Unalloyed titanium (Grade 1-4)
- Alpha-Beta Alloys: Ti-6Al-4V (Grade 5)
- Near-Alpha Alloys: Ti-3Al-2.5V (Grade 9)
Titanium Grade 2 (Commercially Pure)
Chemical Composition
| Element | Content (%) |
|---|---|
| Titanium | Balance (~99.2%) |
| Oxygen | 0.25 max |
| Iron | 0.30 max |
| Carbon | 0.10 max |
| Nitrogen | 0.03 max |
| Hydrogen | 0.015 max |
Mechanical Properties (Annealed)
| Property | Value |
|---|---|
| Tensile Strength | 344-490 MPa (50-71 ksi) |
| Yield Strength (0.2%) | 275-450 MPa (40-65 ksi) |
| Elongation | 30% minimum |
| Reduction of Area | 40% minimum |
| Hardness | 150-200 HB |
Characteristics
- Most formable CP titanium grade
- Excellent corrosion resistance
- Good weldability
- Moderate strength
- Most economical CP grade
Common Applications
- Chemical processing equipment
- Desalination plants
- Marine applications
- Heat exchangers
- Medical implants (dental, surgical)
- Pipe and tube for aggressive environments
- Aerospace ducting
Titanium Grade 5 (Ti-6Al-4V) – Alpha-Beta Alloy
Chemical Composition
| Element | Content (%) |
|---|---|
| Titanium | Balance (~90%) |
| Aluminum | 5.5-6.75 |
| Vanadium | 3.5-4.5 |
| Iron | 0.30 max |
| Oxygen | 0.20 max |
| Carbon | 0.10 max |
| Nitrogen | 0.05 max |
| Hydrogen | 0.015 max |
Mechanical Properties
Annealed Condition
| Property | Value |
|---|---|
| Tensile Strength | 950 MPa (138 ksi) |
| Yield Strength (0.2%) | 880 MPa (128 ksi) |
| Elongation | 14% minimum |
| Reduction of Area | 30% minimum |
Solution Treated and Aged (STA)
| Property | Value |
|---|---|
| Tensile Strength | 1100 MPa (160 ksi) |
| Yield Strength (0.2%) | 1035 MPa (150 ksi) |
| Elongation | 10% minimum |
| Reduction of Area | 25% minimum |
Characteristics
- Highest strength of common titanium grades
- Good fracture toughness
- Excellent fatigue resistance
- Good creep resistance up to 400°C
- Requires proper heat treatment for optimal properties
Common Applications
- Aircraft structures and components
- Gas turbine engine parts
- Missile and space vehicle parts
- Sports equipment (bicycles, clubs)
- Medical implants (orthopedic)
- High-performance marine components
- Pressure vessels
Titanium Grade 9 (Ti-3Al-2.5V) – Near-Alpha Alloy
Chemical Composition
| Element | Content (%) |
|---|---|
| Titanium | Balance (~94%) |
| Aluminum | 2.5-3.5 |
| Vanadium | 2.0-3.0 |
| Iron | 0.25 max |
| Oxygen | 0.15 max |
| Carbon | 0.05 max |
| Nitrogen | 0.02 max |
| Hydrogen | 0.015 max |
Mechanical Properties
| Property | Annealed | Cold Worked |
|---|---|---|
| Tensile Strength | 620 MPa (90 ksi) | 900 MPa (130 ksi) |
| Yield Strength (0.2%) | 510 MPa (74 ksi) | 760 MPa (110 ksi) |
| Elongation | 20% minimum | 12% minimum |
Characteristics
- Intermediate strength between CP and Grade 5
- Better cold workability than Grade 5
- Good weldability
- Excellent for tube applications
- Good fatigue properties
- 30-40% stronger than Grade 2
Common Applications
- Aircraft hydraulic tubing
- Sporting goods (bicycle frames, golf clubs)
- Medical devices
- Chemical processing
- Offshore platforms
- Cryogenic applications
Comprehensive Comparison
Mechanical Properties Comparison
| Property | Grade 2 | Grade 5 | Grade 9 |
|---|---|---|---|
| Tensile Strength | 344-490 MPa | 950-1100 MPa | 620-900 MPa |
| Yield Strength | 275-450 MPa | 880-1035 MPa | 510-760 MPa |
| Elongation | 30% | 10-14% | 12-20% |
| Formability | Excellent | Moderate | Good |
| Weldability | Excellent | Good | Good |
| Corrosion Resistance | Excellent | Very Good | Very Good |
Temperature Performance
| Property | Grade 2 | Grade 5 | Grade 9 |
|---|---|---|---|
| Maximum Service | 425°C (800°F) | 400°C (750°F) | 315°C (600°F) |
| Creep Resistance | Good | Very Good | Moderate |
| Thermal Stability | Excellent | Good | Good |
Fabrication Comparison
| Process | Grade 2 | Grade 5 | Grade 9 |
|---|---|---|---|
| Cold Forming | Excellent | Limited | Good |
| Hot Forming | Good | Good | Good |
| Machining | Moderate | Moderate | Moderate |
| Welding (Auto) | Excellent | Good | Good |
| Welding (Manual) | Excellent | Fair | Fair |
Cost Comparison
Titanium pricing varies significantly by grade:
| Grade | Relative Cost | Cost Index |
|---|---|---|
| Grade 2 | Lowest CP titanium | 1.0x |
| Grade 9 | Intermediate | 1.3-1.5x |
| Grade 5 | Highest common grade | 1.5-2.0x |
Note: All titanium grades are significantly more expensive than steel or stainless steel (typically 5-20x depending on the comparison).
Application Selection Guide
Choose Grade 2 (CP Ti) When:
- Corrosion resistance is the primary concern
- Moderate strength is sufficient
- Maximum formability is required
- Budget is limited
- Chemical processing environment
- Medical devices (biocompatibility critical)
- Marine or offshore applications
- Welding fabrication is extensive
Choose Grade 5 (Ti-6Al-4V) When:
- Maximum strength is required
- High fatigue resistance needed
- Aerospace structural components
- Gas turbine applications
- High-stress medical implants
- Weight reduction is critical
- Can justify higher cost for performance
- Thermal resistance to ~400°C needed
Choose Grade 9 (Ti-3Al-2.5V) When:
- Tube or pipe applications
- Intermediate strength (stronger than Grade 2)
- Hydraulic systems (aircraft tubing)
- Sporting goods (bicycles, golf)
- Good cold workability needed
- Balance of strength and formability
- Cost-sensitive high-strength applications
- Cryogenic service
Heat Treatment Effects
Grade 2 (CP Titanium)
- Annealed condition is standard
- Cannot be strengthened by heat treatment
- Properties come from chemistry purity
Grade 5 (Ti-6Al-4V)
- Annealed: Good ductility, moderate strength
- Solution Treated: Maximum ductility
- Solution Treated + Aged (STA): Maximum strength
- Heat treatment required for optimal properties
Grade 9 (Ti-3Al-2.5V)
- Annealed: Good ductility, moderate strength
- Cold Worked: Increases strength significantly
- Can be strengthened by cold work + aging
Corrosion Resistance by Environment
| Environment | Grade 2 | Grade 5 | Grade 9 |
|---|---|---|---|
| Chloride Solutions | Excellent | Very Good | Very Good |
| Seawater | Excellent | Very Good | Very Good |
| Nitric Acid | Excellent | Excellent | Excellent |
| Sulfuric Acid | Good | Good | Good |
| Hydrochloric Acid | Good | Moderate | Moderate |
| Oxidizing Media | Excellent | Excellent | Excellent |
Conclusion
Selecting between Titanium Grade 2, Grade 5, and Grade 9 depends on your specific requirements:
- Grade 2 offers the best corrosion resistance and formability at the lowest cost for the CP titanium family
- Grade 5 provides the highest strength for demanding aerospace and high-performance applications
- Grade 9 balances strength and formability, making it ideal for tube applications
Need titanium materials? Contact Xi’an Coremetal Steel for Grade 2, Grade 5, and Grade 9 titanium sheet, plate, tube, and pipe in various forms and sizes.
Contact: Tracy | Email: tracy@coremetalsteel.com | Phone: +86 18291910632